JP2020167145A - Positive electrode active material for all-solid-state lithium-ion batteries, electrodes and all-solid-state lithium-ion batteries - Google Patents

Abstract

A positive electrode active material for an all-solid-state lithium-ion battery, an electrode, and an all-solid-state lithium-ion battery capable of smoothly exchanging lithium ions between a positive electrode and a solid electrolyte to improve battery performance. . The lithium metal composite oxide is composed of particles containing crystals of a lithium metal composite oxide, the lithium metal composite oxide has a layered structure and contains at least Li and a transition metal, and the particles are subjected to laser diffraction particle size distribution measurement. The relational expression (D90-D10)/D50≧0.90 holds for D10, D50, and D90 obtained from the volume-based cumulative distribution measured by the crystal, and the crystal has 2θ=18 in X-ray diffraction measurement using CuKα rays. All solids in which the ratio α/β of the crystallite size α at the peak within the range of 7 ± 2° and the crystallite size β at the peak within the range of 2θ = 44.6 ± 2° is 1.0 or more Positive electrode active material for lithium-ion batteries. [Selection figure] None

Description

The present invention relates to a positive electrode active material for an all-solid-state lithium-ion battery, an electrode, and an all-solid-state lithium-ion battery.

Research on lithium-ion secondary batteries is active for applications such as drive power sources for electric vehicles and household storage batteries. Among them, the all-solid-state lithium-ion secondary battery has advantages such as high energy density, wide operating temperature range, and resistance to deterioration as compared with the conventional lithium-ion secondary battery using an electrolytic solution. Therefore, the all-solid-state lithium-ion secondary battery is attracting attention as a next-generation energy storage device.

In the following description, the "conventional lithium ion secondary battery using an electrolytic solution" may be referred to as a "liquid lithium ion secondary battery" in order to distinguish it from an all-solid-state lithium ion secondary battery.

Patent Document 1 describes an all-solid-state lithium ion secondary battery using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material. LiNi _1/3 Mn _1/3 Co _1/3 O ₂ is a well-known material as a positive electrode active material for a liquid-based lithium ion secondary battery.

JP-A-2018-014317

At the positive electrode of the all-solid-state lithium-ion secondary battery, lithium ions are exchanged between the positive electrode active material and the solid electrolyte. In the study of an all-solid-state lithium-ion secondary battery, there has been a demand for a positive electrode active material capable of smoothly transferring and receiving the above-mentioned lithium ions and improving battery performance.

Further, in the study of the all-solid-state lithium ion secondary battery, the study knowledge of the conventional liquid-based lithium ion secondary battery may not be utilized. Therefore, it has been necessary to study the all-solid-state lithium-ion secondary battery.

The present invention has been made in view of such circumstances, and is an all-solid-state lithium-ion battery capable of smoothly exchanging lithium ions with and from a solid electrolyte at the positive electrode and improving battery performance. It is an object of the present invention to provide a positive electrode active material for use. Another object of the present invention is to provide an electrode having such a positive electrode active material for an all-solid-state lithium-ion battery and an all-solid-state lithium-ion battery.

In order to solve the above problems, the present invention includes the following aspects.

[1] A positive electrode active material for an all-solid lithium-ion battery composed of particles containing crystals of a lithium metal composite oxide, wherein the lithium metal composite oxide has a layered structure and contains at least Li and a transition metal. The particles contain, with respect to the volume-based cumulative distribution measured by the laser diffraction type particle size distribution measurement, the particle diameters at which the cumulative ratios from the small particle side are 10%, 50%, and 90% are D10, D50, respectively. When D90 is set, the relational expression (D90-D10) / D50 ≧ 0.90 holds, and the crystal is a crystal at a peak within the range of 2θ = 18.7 ± 2 ° in X-ray diffraction measurement using CuKα ray. A positive electrode active material for an all-solid lithium-ion battery in which the ratio α / β of the child size α to the crystallite size β at the peak within the range of 2θ = 44.6 ± 2 ° is 1.0 or more.

[2] The positive electrode active material for an all-solid-state lithium-ion battery of [1] used for an all-solid-state lithium-ion battery containing an oxide solid electrolyte.

[3] The positive electrode activity for an all-solid-state lithium-ion battery according to [1] or [2], wherein the transition metal is at least one selected from the group consisting of Ni, Co, Mn, Ti, Fe, V and W. material.

[4] The lithium metal composite oxide is a positive electrode active material for an all-solid-state lithium-ion battery according to [3] represented by the following formula (1).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 (1)
(However, M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V, and −0. 1 ≦ x ≦ 0.30, 0 <y ≦ 0.40, 0 ≦ z ≦ 0.40, 0 ≦ w ≦ 0.10.

[5] The positive electrode active material for an all-solid-state lithium-ion battery according to [4], which satisfies 1-yz-w ≧ 0.50 and y ≦ 0.30 in the above formula (1).

[6] The particles are composed of primary particles, secondary particles formed by aggregating the primary particles, and single particles that exist independently of the primary particles and the secondary particles. The positive electrode active material for an all-solid lithium ion battery according to any one of [1] to [5], wherein the content of the single particle in the particles is 20% or more.

[7] The positive electrode active material for an all-solid-state lithium-ion battery according to any one of [1] to [6], wherein the particles have a coating layer made of a metal composite oxide on the surface of the particles.

[8] An electrode containing the positive electrode active material for an all-solid-state lithium-ion battery according to any one of [1] to [7].

[9] The electrode according to [8], further comprising a solid electrolyte.

[10] It has a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode. The solid electrolyte layer contains a first solid electrolyte, and the positive electrode is the solid electrolyte layer. The positive electrode active material layer has a positive electrode active material layer in contact with the positive electrode active material layer and a current collector in which the positive electrode active material layer is laminated, and the positive electrode active material layer is an all-solid body according to any one of [1] to [7]. An all-solid-state lithium-ion battery comprising a positive electrode active material for a lithium-ion battery or the electrode according to [8] or [9].

[11] The all-solid-state lithium-ion battery according to [10], wherein the positive electrode active material layer contains the positive electrode active material for an all-solid-state lithium-ion battery and a second solid electrolyte.

[12] The all-solid-state lithium-ion battery according to [11], wherein the first solid electrolyte and the second solid electrolyte are the same substance.

[13] The all-solid-state lithium-ion battery according to any one of [10] to [12], wherein the first solid electrolyte has an amorphous structure.

[14] The all-solid-state lithium-ion battery according to any one of [10] to [13], wherein the first solid electrolyte is an oxide solid electrolyte.

According to the present invention, it is possible to provide a positive electrode active material for an all-solid-state lithium-ion battery, which can smoothly transfer lithium ions to and from a solid electrolyte at the positive electrode and can improve battery performance. Further, it is possible to provide an electrode having such a positive electrode active material for an all-solid-state lithium-ion battery and an all-solid-state lithium-ion battery.

FIG. 1 is a schematic view of a crystallite having a crystal structure belonging to the space group R-3m. FIG. 2 is a schematic view showing a laminate included in the all-solid-state lithium-ion battery of the embodiment. FIG. 3 is a schematic view showing the overall configuration of the all-solid-state lithium-ion battery of the embodiment.

<Positive electrode active material for all-solid-state lithium-ion batteries>
The positive electrode active material for an all-solid-state lithium-ion battery of the present embodiment is particles containing crystals of a lithium metal composite oxide. The positive electrode active material for an all-solid-state lithium-ion battery of the present embodiment is a positive electrode active material preferably used for an all-solid-state lithium-ion battery containing an oxide solid electrolyte.
Hereinafter, the positive electrode active material for an all-solid-state lithium ion battery of the present embodiment may be simply referred to as a “positive electrode active material”.

The positive electrode active material of the present embodiment satisfies the following requirements.
(Requirement 1) The lithium metal composite oxide contained in the positive electrode active material has a layered structure and contains at least Li and a transition metal.

(Requirement 2) Regarding the cumulative distribution measured by the laser diffraction type particle size distribution measurement, the particle diameters at which the cumulative ratios from the small particle side are 10%, 50%, and 90% are set to D10, D50, and D90, respectively. Then, the relational expression (D90-D10) / D50 ≧ 0.90 holds.

(Requirement 3) The crystal has a crystallite size α at a peak in the range of 2θ = 18.7 ± 2 ° and a peak in the range of 2θ = 44.6 ± 2 ° in X-ray diffraction measurement using CuKα ray. The ratio α / β to the crystallite size β in the above is 1.0 or more.
Hereinafter, they will be described in order.

(Requirement 1: Lithium metal composite oxide)
The lithium metal composite oxide contained in the positive electrode active material of the present embodiment contains at least one selected from the group consisting of Ni, Co, Mn, Ti, Fe, V and W as the transition metal.

The lithium metal composite oxide contained in the positive electrode active material of the present embodiment contains at least one selected from the group consisting of Ni, Co and Mn as the transition metal, so that the lithium metal composite oxide obtained is Li ion. Form a desorbable or insertable stable crystal structure. Therefore, when the positive electrode active material of the present embodiment is used for the positive electrode of the secondary battery, a high charge / discharge capacity can be obtained.

Further, the lithium metal composite oxide contained in the positive electrode active material of the present embodiment contains at least one selected from the group consisting of Ti, Fe, V and W, so that the lithium metal composite oxide obtained is crystalline. The structure becomes strong. Therefore, the positive electrode active material of the present embodiment is a positive electrode active material having high thermal stability. Further, the positive electrode active material of the present embodiment has improved cycle characteristics.

More specifically, the lithium metal composite oxide is represented by the following composition formula (1).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 ··· (1)
(However, M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La and V, and- 0.1 ≦ x ≦ 0.30, 0 ≦ y ≦ 0.40, 0 ≦ z ≦ 0.40, 0 ≦ w ≦ 0.10.

(About x)
From the viewpoint of obtaining a lithium secondary battery having good cycle characteristics, x in the composition formula (1) is preferably more than 0, more preferably 0.01 or more, and further preferably 0.02 or more. .. Further, from the viewpoint of obtaining a lithium secondary battery having a higher initial coulombic efficiency, x in the composition formula (1) is preferably 0.25 or less, and more preferably 0.10 or less.

In the present specification, "good cycle characteristics" means that the amount of decrease in battery capacity is low due to repeated charging and discharging, and that the capacity ratio at the time of remeasurement to the initial capacity is unlikely to decrease. ..

Further, in the present specification, the "first Coulomb efficiency" is a value obtained by "(first discharge capacity) / (first charge capacity) x 100 (%)". A secondary battery with high initial coulombic efficiency tends to have a small irreversible capacity at the time of initial charge / discharge, and a larger capacity per volume and weight.

The upper limit value and the lower limit value of x can be arbitrarily combined. In the composition formula (1), x may be −0.10 or more and 0.25 or less, or −0.10 or more and 0.10 or less.

x may be more than 0 and 0.30 or less, may be more than 0 and be 0.25 or less, and may be more than 0 and 0.10 or less.

x may be 0.01 or more and 0.30 or less, 0.01 or more and 0.25 or less, or 0.01 or more and 0.10 or less.

x may be 0.02 or more and 0.3 or less, 0.02 or more and 0.25 or less, or 0.02 or more and 0.10 or less.

In this embodiment, it is preferable that 0 <x ≦ 0.30.

(About y)
Further, from the viewpoint of obtaining a lithium secondary battery having a low internal resistance of the battery, y in the composition formula (1) is preferably more than 0, more preferably 0.005 or more, and more preferably 0.01 or more. It is more preferable, and it is particularly preferable that it is 0.05 or more. Further, from the viewpoint of obtaining a lithium secondary battery having high thermal stability, y in the composition formula (1) is more preferably 0.35 or less, further preferably 0.33 or less, and 0. It is even more preferably 30 or less.

The upper limit value and the lower limit value of y can be arbitrarily combined. In the composition formula (1), y may be 0 or more and 0.35 or less, 0 or more and 0.33 or less, or 0 or more and 0.30 or less.

y may be more than 0 and 0.40 or less, more than 0 and 0.35 or less, more than 0 and 0.33 or less, more than 0 and 0.30 or less. There may be.

y may be 0.005 or more and 0.40 or less, 0.005 or more and 0.35 or less, 0.005 or more and 0.33 or less, and 0.005 or more and 0. It may be .30 or less.

y may be 0.01 or more and 0.40 or less, 0.01 or more and 0.35 or less, 0.01 or more and 0.33 or less, and 0.01 or more and 0. It may be .30 or less.

y may be 0.05 or more and 0.40 or less, 0.05 or more and 0.35 or less, 0.05 or more and 0.33 or less, and 0.05 or more and 0. It may be .30 or less.

In this embodiment, it is preferable that 0 <y ≦ 0.40.

In the present embodiment, in the composition formula (1), 0 <x ≦ 0.10 and 0 <y ≦ 0.40 are more preferable.

(About z)
Further, from the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, z in the composition formula (1) is preferably 0.01 or more, more preferably 0.02 or more, and 0.1 or more. It is more preferable to have. Further, from the viewpoint of obtaining a lithium secondary battery having high storage stability at a high temperature (for example, in an environment of 60 ° C.), z in the composition formula (1) is preferably 0.39 or less, preferably 0.38 or less. More preferably, it is more preferably 0.35 or less.

The upper limit value and the lower limit value of z can be arbitrarily combined. In the composition formula (1), z may be 0 or more and 0.39 or less, 0 or more and 0.38 or less, or 0 or more and 0.35 or less.

z may be 0.01 or more and 0.40 or less, 0.01 or more and 0.39 or less, 0.01 or more and 0.38 or less, and 0.01 or more and 0. It may be .35 or less.

z may be 0.02 or more and 0.40 or less, 0.02 or more and 0.39 or less, 0.02 or more and 0.38 or less, and 0.02 or more and 0. It may be .35 or less.

z may be 0.10 or more and 0.40 or less, 0.10 or more and 0.39 or less, 0.10 or more and 0.38 or less, and 0.10 or more and 0. It may be .35 or less.

(About w)
Further, from the viewpoint of obtaining a lithium secondary battery having a low internal resistance of the battery, w in the composition formula (1) preferably exceeds 0, more preferably 0.0005 or more, and more preferably 0.001 or more. Is even more preferable. Further, from the viewpoint of obtaining a lithium secondary battery having a large discharge capacity at a high current rate, w in the composition formula (1) is preferably 0.09 or less, more preferably 0.08 or less, and 0. It is more preferably .07 or less.

The upper limit value and the lower limit value of w can be arbitrarily combined. In the composition formula (1), w may be 0 or more and 0.09 or less, 0 or more and 0.08 or less, or 0 or more and 0.07 or less.

w may be more than 0 and 0.10 or less, more than 0 and 0.09 or less, more than 0 and 0.08 or less, more than 0 and 0.07 or less. There may be.

w may be 0.0005 or more and 0.10 or less, 0.0005 or more and 0.09 or less, 0.0005 or more and 0.08 or less, and 0.0005 or more and 0. It may be .07 or less.

w may be 0.001 or more and 0.10 or less, 0.001 or more and 0.09 or less, 0.001 or more and 0.08 or less, and 0.001 or more and 0. It may be .07 or less.

(About y + z + w)
Further, from the viewpoint of obtaining a lithium secondary battery having a large battery capacity, in the present embodiment, y + z + w in the composition formula (1) is preferably 0.50 or less, more preferably 0.48 or less, and 0.46 or less. More preferred.

The lithium metal composite oxide contained in the positive electrode active material of the present embodiment preferably satisfies 1-yz-w ≧ 0.50 and y ≦ 0.30 in the composition formula (1). That is, the lithium metal composite oxide contained in the positive electrode active material of the present embodiment has a Ni content molar ratio of 0.50 or more and a Co content molar ratio of 0.30 or less in the composition formula (1). preferable.

(About M)
M in the composition formula (1) is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga, La and V. Represents.

Further, from the viewpoint of obtaining a lithium secondary battery having high cycle characteristics, M in the composition formula (1) is one or more elements selected from the group consisting of Ti, Mg, Al, W, B and Zr. Is preferable, and it is more preferable that it is one or more elements selected from the group consisting of Al and Zr. Further, from the viewpoint of obtaining a lithium secondary battery having high thermal stability, it is preferable that the element is one or more selected from the group consisting of Ti, Al, W, B and Zr.

An example of a preferable combination of x, y, z, and w described above is x of 0.02 or more and 0.3 or less, y of 0.05 or more and 0.30 or less, and z of 0.02 or more and 0. It is 35 or less, and w is 0 or more and 0.07 or less. For example, a lithium metal composite oxide having x = 0.05, y = 0.20, z = 0.30, w = 0, x = 0.05, y = 0.08, z = 0.04, Examples thereof include a lithium metal composite oxide having w = 0 and a lithium metal composite oxide having x = 0.25, y = 0.07, z = 0.02, and w = 0.

(Layered structure)
In the present embodiment, the crystal structure of the lithium metal composite oxide is a layered structure. The crystal structure of the lithium metal composite oxide is more preferably a hexagonal crystal structure or a monoclinic crystal structure.

The hexagonal crystal structure is P3, P3 ₁ , P3 ₂ , R3, P-3, R-3, P312, P321, P3 ₁ 12, P3 ₁ 21, P3 ₂ 12, P3 ₂ 21, R32, P3 m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 ₁ , P6 ₅ , P6 ₂ , P6 ₄ , P6 _{3 , P6, P6 / m, P6} 3 / m, P622, P6 1 22, P6 5 22, P6 2 22, P6 4 22, P6 3 22, P6mm, P6cc, P6 3 cm, P6 3 mc, P- It belongs to any one space group selected from the group consisting of 6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P6 ₃ / mcm, and P6 ₃ / mmc.

The monoclinic crystal structure is P2, P2 ₁ , C2, Pm, Pc, Cm, Cc, P2 / m, P2 ₁ / m, C2 / m, P2 / c, P2 ₁ / c, C2 /. It belongs to any one space group selected from the group consisting of c.

Of these, in order to obtain a lithium secondary battery with a high discharge capacity, the crystal structure is a hexagonal crystal structure belonging to the space group R-3m or a monoclinic crystal structure belonging to C2 / m. The structure is particularly preferable.

(Requirement 2: Particle size distribution)
Regarding the above-mentioned requirement 2, the "volume-based cumulative particle size" can be measured by a measuring method based on the laser diffraction / scattering method. Particle size distribution measurement based on the laser diffraction scattering method is called "laser diffraction type particle size distribution measurement".

Specifically, the cumulative particle size of the positive electrode active material is measured by the following measuring method.

First, 0.1 g of the positive electrode active material is put into 50 ml of a 0.2 mass% sodium hexametaphosphate aqueous solution to obtain a dispersion liquid in which the positive electrode active material is dispersed.

Next, the particle size distribution of the obtained dispersion is measured using a Microtrack MT3300EXII (laser diffraction scattering particle size distribution measuring device) manufactured by Microtrac Bell Co., Ltd., and a volume-based cumulative particle size distribution curve is obtained. The measurement range of the particle size distribution was 0 μm or more and 2000 μm or less.

In the obtained cumulative particle size distribution curve, the value of the particle size at the point where the cumulative volume from the fine particle side is 10% when the whole is 100% is 10% cumulative volume particle size D ₁₀ (μm), 50%. The value of the particle size at the point is 50% cumulative volume particle size D ₅₀ (μm), and the value of the particle size at the point 90% is 90% cumulative volume particle size D ₉₀ (μm).

In the present embodiment, (D _90- D ₁₀ ) / D ₅₀ is preferably 1.0 or more, more preferably 1.2 or more, and even more preferably 1.5 or more.

In the present embodiment, (D _90- D ₁₀ ) / D ₅₀ is preferably 10.0 or less, more preferably 6.5 or less.

The upper and lower limits of (D _90- D ₁₀ ) / D ₅₀ can be arbitrarily combined. In the present embodiment, (D _90- D ₁₀ ) / D ₅₀ may be 0.9 or more and 10.0 or less, or 0.9 or more and 6.5 or less.
(D _90- D ₁₀ ) / D ₅₀ may be 1.0 or more and 10.0 or less, or 1.0 or more and 6.5 or less.

(D _90- D ₁₀ ) / D ₅₀ may be 1.2 or more and 10.0 or less, or 1.2 or more and 6.5 or less.

(D _90- D ₁₀ ) / D ₅₀ may be 1.5 or more and 10.0 or less, or 1.5 or more and 6.5 or less.

In order to set (D _90- D ₁₀ ) / D ₅₀ in a desired range, two or more kinds of positive electrode active materials having different particle sizes may be mixed to prepare a particle size distribution.

(Requirement 3: Crystallite size ratio)
Regarding the above-mentioned requirement 3, the "crystallite size α" and "crystallite size β" can be measured by powder X-ray diffraction measurement using CuKα ray.

Specifically, the crystallite size of the lithium metal composite oxide contained in the positive electrode active material is measured by the following measuring method.

First, the positive electrode active material of the present embodiment is subjected to powder X-ray diffraction measurement using CuKα as a radiation source and a measurement range of a diffraction angle 2θ of 10 ° or more and 90 ° or less. As a result of the measurement, an X-ray diffraction spectrum is obtained in which the horizontal axis is 2θ and the vertical axis is the relative intensity when the maximum peak intensity of all the peaks in the measurement range is 1.

Then, from the obtained X-ray diffraction spectrum, a peak in the range of 2θ = 18.7 ± 2 ° and a peak in the range of 2θ = 44.6 ± 2 ° are determined.

Next, the full width at half maximum is calculated for each of the determined peaks.

In calculating the half-value full width, plot the average value of each intensity at 2θ = 10-12 ° at 2θ = 10 °, and plot the average value of each intensity at 2θ = 88-90 ° at 2θ = 90 °. The straight line connecting the mean value plotted at 2θ = 10 ° and the mean value plotted at 2θ = 90 ° was used as the baseline.

By substituting the diffraction angle of the peak and the obtained half-value width into the Scherrer equation (D = Kλ / Bcosθ (D: crystallite size, K: Scherrer constant, B: half-value width of the peak)), the crystallite size Can be calculated.

It should be noted that calculating the crystallite size from the full width at half maximum of the diffraction peak using the Scherrer equation is a conventionally used method (for example, "X-ray structure analysis-determining the arrangement of atoms-" 2002 4 Published 3rd edition on April 30, by Yoshio Waseda and Eiichiro Matsubara, see).

Hereinafter, the case where the lithium metal composite oxide contained in the positive electrode active material of the present embodiment has a hexagonal crystal structure belonging to the space group R-3m will be described in more detail with reference to the drawings. To do.

FIG. 1 is a schematic view of a crystallite having a crystal structure belonging to the space group R-3m. In the crystallite shown in FIG. 1, the crystallite size in the perpendicular direction of the 003 plane corresponds to the above-mentioned crystallite size α. Further, in the crystallite shown in FIG. 1, the crystallite size in the perpendicular direction on the 104th plane corresponds to the crystallite size β.

The larger the value of the crystallite size ratio α / β is, the more the crystallites are anisotropically grown parallel to the z-axis in FIG. 1, and the value of α / β approaches 1. The more it shows that the crystallites are isotropically grown.

The positive electrode active material of the present embodiment has a crystallite size ratio α / β of 1.0 or more. That is, in the positive electrode active material of the present embodiment, the crystals of the lithium metal composite oxide contained in the positive electrode active material are anisotropically grown in the z-axis direction with respect to the x-axis or y-axis in FIG. ..

In the positive electrode active material of the present embodiment, the lithium metal composite oxide has anisotropically grown crystals, so that the battery performance such as the discharge capacity can be improved.

For example, case 1 is a crystallite of a lithium metal composite oxide having a crystallite size ratio α / β of 1.0 or more, and a flat crystallite in which the crystallites are anisotropically grown in a direction parallel to the xy plane of FIG. In case 2, the crystallites of case 1 and the crystallites of case 2 having the same volume are compared. In this case, the crystallite in case 1 has a shorter distance to the center of the crystallite than the crystallite in case 2. Therefore, in the crystallite of Case 1, the movement of Li with charge and discharge becomes easy.

In the present embodiment, α / β is preferably 1.2 or more, and more preferably 1.5 or more. Further, α / β is preferably 3.0 or less, and more preferably 2.5 or less.

In order to obtain a lithium secondary battery having high cycle characteristics, the crystallite size α is preferably 400 Å or more and 1200 Å or less, more preferably 1100 Å or less, further preferably 1000 Å or less, and 900 Å or less. Is even more preferable, and 840 Å or less is particularly preferable. Further, in the sense of obtaining a lithium secondary battery having a high charge capacity, the crystallite size α is more preferably 450 Å or more, and further preferably 500 Å or more.

The upper and lower limits of α can be combined arbitrarily. In the present embodiment, α may be 400 Å or more and 1100 Å or less, 400 Å or more and 1000 or less, or 400 Å or more and 900 Å or less.

α may be 450 Å or more and 1200 Å or less, 450 Å or more and 1100 Å or less, 450 Å or more and 1000 or less, or 450 Å or more and 900 Å or less.

α may be 500 Å or more and 1200 Å or less, 500 Å or more and 1100 Å or less, 500 Å or more and 1000 or less, or 500 Å or more and 900 Å or less.

In order to obtain a lithium secondary battery having high cycle characteristics, the crystallite size β is preferably 600 Å or less, more preferably 550 Å or less, further preferably 500 Å or less, and more preferably 450 Å or less. Especially preferable. Further, in order to obtain a lithium secondary battery having a high charge capacity, the crystallite size β is preferably 200 Å or more, more preferably 250 Å or more, and further preferably 300 Å or more.

The upper limit value and the lower limit value of β can be arbitrarily combined. In the present embodiment, β may be 200 Å or more and 600 Å or less, 200 Å or more and 550 or less, 200 Å or more and 500 Å or less, or 200 Å or more and 450 Å or less.

β may be 250 Å or more and 600 Å or less, 250 Å or more and 550 or less, 250 Å or more and 500 Å or less, or 250 Å or more and 450 Å or less.

β may be 300 Å or more and 600 Å or less, 300 Å or more and 550 or less, 300 Å or more and 500 Å or less, or 300 Å or more and 450 Å or less.

According to the studies by the inventors, when used for the positive electrode of a conventional liquid-based lithium-ion secondary battery, even a positive electrode active material showing good battery performance is used for the positive electrode of an all-solid-state lithium-ion battery. It was found that some of them had insufficient performance. As a result of examination by the inventors based on the knowledge peculiar to such an all-solid-state lithium-ion secondary battery, the positive electrode active material of the present embodiment satisfying the above-mentioned requirements 1 to 3 is an all-solid-state lithium-ion battery. It was found that a high initial charge capacity was measured when used for the positive electrode.

First, in the positive electrode active material of the present embodiment, the insertion and desorption of lithium ions can be satisfactorily performed by satisfying the requirement 1.

Further, the positive electrode active material of the present embodiment satisfies Requirement 2. In the positive electrode of an all-solid-state lithium-ion secondary battery, lithium ions are exchanged between the positive electrode active material and the solid electrolyte. In such an all-solid-state lithium-ion secondary battery, by having a wide particle size distribution that satisfies the requirement 2, the contact area between the positive electrode active materials or between the positive electrode active material and the solid electrolyte tends to expand. As a result, when the positive electrode active material of the present embodiment is used for the positive electrode of the all-solid-state lithium-ion battery, lithium ions can be easily exchanged between the positive electrode active material and the solid electrolyte.

Further, satisfying the requirement 3 in the positive electrode active material of the present embodiment means that the crystals of the lithium metal composite oxide having a layered structure are anisotropically grown in the laminating direction of the layered structure. A lithium metal composite oxide satisfying Requirement 3 easily inserts and desorbs lithium ions between layers from a direction intersecting the stacking direction of the layered structure. Therefore, if the positive electrode active material of the present embodiment satisfies the requirement 3, the battery performance can be easily improved.

Therefore, when the positive electrode active material of the present embodiment satisfying requirements 1 to 3 is used for the positive electrode of an all-solid-state lithium-ion battery, lithium ions can be smoothly transferred to and from the solid electrolyte, and the battery performance. Can be improved.

(Other configuration 1)
In the positive electrode active material of the present embodiment, the particles constituting the positive electrode active material exist independently of the primary particles, the secondary particles formed by aggregating the primary particles, and the primary particles and the secondary particles. It is preferably composed of particles.

In the present invention, the "primary particle" is a particle having no grain boundary in appearance when observed with a scanning electron microscope in a field of view of 20000 times, and has a particle diameter of less than 0.5 μm. Means particles.

In the present invention, the "secondary particles" mean particles formed by agglomeration of primary particles. When the secondary particles are observed with a scanning electron microscope in a field of view of 20000 times, grain boundaries are present on the appearance.

In the present invention, a "single particle" is a particle that exists independently of a secondary particle and has no grain boundary in appearance when observed with a scanning electron microscope at a field of view of 20000 times. It means particles having a particle diameter of 0.5 μm or more.

That is, the positive electrode active material of the present embodiment includes particles having no grain boundaries on the appearance and particles having grain boundaries on the appearance when observed at a field of view of 20000 times using a scanning electron microscope. Consists of.

Particles having no grain boundaries on the outside are composed of "primary particles" having a small particle size and "single particles" having a large particle size based on a particle size of 0.5 μm.

The particles having grain boundaries on the appearance are "secondary particles" which are aggregated particles of the above-mentioned "primary particles".

In the positive electrode active material of the present embodiment, the content of single particles in the whole particles is preferably 20% or more. When the positive electrode active material having a single particle content of 20% or more in the whole particles is used in an all-solid-state battery, it is easy to secure a contact interface with a solid electrolyte in the positive electrode layer, and lithium ion conduction through the interface is easy. It is done smoothly.

Further, it is assumed that the positive electrode active material having a single particle content of 20% or more in the whole particles is used for the positive electrode of an all-solid-state battery and repeatedly charged and discharged because there is no grain boundary in the single particles in the whole particles. However, the particles are not easily broken and the conductive path is easily maintained.

The average particle size of the single particles is preferably 0.5 μm or more, and more preferably 1.0 μm or more. The average particle size of the single particles is preferably 10 μm or less, and more preferably 5 μm or less.

The upper limit value and the lower limit value of the average particle diameter of a single particle can be arbitrarily combined.

The average particle size of the secondary particles is preferably 3.0 μm or more, and more preferably 5.0 μm or more. The average particle size of the secondary particles is preferably 15 μm or less, and more preferably 10 μm or less.

The upper limit value and the lower limit value of the average particle diameter of the secondary particles can be arbitrarily combined.

The average particle size of the single particle and the secondary particle can be measured by the following method.

First, the positive electrode active material of the present embodiment is placed on a conductive sheet attached on the sample stage. Next, using a scanning electron microscope (JSM-5510 manufactured by JEOL Ltd.), the positive electrode active material is irradiated with an electron beam having an accelerating voltage of 20 kV, and observation is performed with a field of view of 20000 times.

Next, 50 or more and 98 or less single particles or secondary particles are extracted from the obtained electron microscope image (SEM photograph) by the following method.

(Single particle extraction method)
When measuring the average particle size of a single particle, all the single particles included in one visual field are to be measured in a magnified field of 20000 times. When the number of single particles contained in one visual field is less than 50, the single particles in a plurality of visual fields are measured until the number of measurements is 50 or more.

(Extraction method of secondary particles)
When measuring the average particle size of secondary particles, all the secondary particles included in one visual field are measured in a magnified field of 20000 times. When the number of secondary particles contained in one field of view is less than 50, the secondary particles in a plurality of fields of view are measured until the number of measurements is 50 or more.

With respect to the extracted image of a single particle or a secondary particle, the distance between the parallel lines (constant direction diameter) when sandwiched between parallel lines drawn from a certain direction is measured as the particle diameter of the single particle or the secondary particle.

The calculated average particle size of the obtained single particle or secondary particle is the average particle size of the single particle contained in the positive electrode active material or the average particle size of the secondary particle contained in the positive electrode active material.

(Other configuration 2)
The positive electrode active material of the present embodiment preferably has a coating layer made of a metal composite oxide on the surface of the particles constituting the positive electrode active material.

As the metal composite oxide constituting the coating layer, one having lithium ion conductivity is used.

As such a metal composite oxide, for example, at least one selected from the group consisting of Li and Nb, Ge, Si, P, Al, W, Ta, Ti, S, Zr, Zn, V and B. A metal composite oxide with an element can be mentioned.

When the positive electrode active material of the present embodiment has a coating layer, the formation of a high resistance layer at the interface between the positive electrode active material and the solid electrolyte can be suppressed, and high output of the all-solid-state battery can be realized. Such an effect is likely to be obtained in a sulfide-based all-solid-state battery using a sulfide-based solid electrolyte as the solid electrolyte.

<Manufacturing method of positive electrode active material 1>
In producing the lithium metal composite oxide contained in the positive electrode active material of the present embodiment, first, metals other than lithium, that is, Ni, Co, Mn, Fe, Cu, Ti, Mg, Al, W, B, Mo , Nb, Zn, Sn, Zr, Ga, La and V, a metal composite compound containing any one or more arbitrary metals is prepared, and the metal composite compound is fired with an appropriate lithium salt, an inert melting agent and the like. It is preferable to do so. As the metal composite compound, a metal composite hydroxide or a metal composite oxide is preferable.

Hereinafter, an example of the method for producing the lithium metal composite oxide will be described separately for the process for producing the metal composite compound and the process for producing the lithium metal composite oxide.

(Manufacturing process of metal composite compound)
The metal composite compound can be produced by a commonly known batch co-precipitation method or continuous co-precipitation method. Hereinafter, the production method thereof will be described in detail using a metal composite hydroxide containing nickel, cobalt and manganese as an example.

First co-precipitation method, in particular by a continuous method described in 2002-201028 JP-nickel salt solution, cobalt salt solution, is reacted manganese salt solution and a complexing _{agent, Ni a Co b Mn c (} OH) ₂ A metal composite hydroxide represented by (a + b + c = 1 in the formula) is produced.

The nickel salt which is the solute of the nickel salt solution is not particularly limited, and for example, any one or more of nickel sulfate, nickel nitrate, nickel chloride and nickel acetate can be used.

As the cobalt salt which is the solute of the cobalt salt solution, for example, any one or more of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate can be used.

As the manganese salt which is the solute of the manganese salt solution, for example, any one or more of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

The above metal salts are used at a ratio corresponding to the composition ratio of the above Ni _a Co _b Mn _c (OH) ₂ . In addition, water is used as a solvent.

The complexing agent is a compound capable of forming a complex with nickel, cobalt, and manganese ions in an aqueous solution. Examples thereof include ammonium ion feeders (ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride), hydrazine, ethylenediamine tetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine. The complexing agent may not be contained, and if the complexing agent is contained, the amount of the complexing agent contained in the nickel salt solution, the cobalt salt solution, the arbitrary metal M salt solution and the mixed solution containing the complexing agent is For example, the molar ratio to the total number of moles of the metal salt is greater than 0 and 2.0 or less.

At the time of precipitation, alkali metal hydroxides (for example, sodium hydroxide and potassium hydroxide) are added as necessary to adjust the pH value of the aqueous solution.

When a complexing agent is continuously supplied to the reaction vessel in addition to the nickel salt solution, cobalt salt solution, and manganese salt solution, nickel, cobalt, and manganese react with each other, and Ni _a Co _b Mn _c (OH) ₂ Is manufactured.

During the reaction, the temperature of the reaction vessel is controlled, for example, in the range of 20 ° C. or higher and 80 ° C. or lower, preferably 30 to 70 ° C.

The pH value in the reaction vessel is controlled, for example, in the range of pH 9 or more and pH 13 or less, preferably pH 11 or more and pH 13 or less.

The substances in the reaction vessel are appropriately stirred and mixed. The reaction vessel is of a type in which the formed reaction precipitate overflows for separation.

The secondary particle size of the lithium metal composite oxide finally obtained in the following steps by appropriately controlling the concentration of the metal salt supplied to the reaction vessel, the stirring speed, the reaction temperature, the reaction pH, the firing conditions described later, and the like. , Various physical properties such as pore radius can be controlled.

In addition to controlling the above conditions, various gases such as an inert gas such as nitrogen, argon and carbon dioxide, an oxidizing gas such as air and oxygen, or a mixed gas thereof are supplied into the reaction vessel to obtain the gas. The oxidation state of the reaction product may be controlled.

Peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorates, hypochlorites, nitric acid, halogens, ozone, etc. are used as compounds that oxidize the obtained reaction products. can do.

As a compound for reducing the obtained reaction product, organic acids such as oxalic acid and formic acid, sulfites, hydrazine and the like can be used.

After the above reaction, the obtained reaction precipitate is washed with water and then dried to obtain a metal composite compound. In the present embodiment, as the metal composite compound, nickel cobalt manganese hydroxide as a nickel cobalt manganese composite compound is obtained. If necessary, the reaction precipitate may be washed with a weak acid water or an alkaline solution containing sodium hydroxide or potassium hydroxide.

In the present embodiment, the above requirements (2) and (3) are set within the scope of the present embodiment by pulverizing the metal composite compound obtained by drying by applying an appropriate external force to adjust the dispersed state of the particles. A metal composite hydroxide that is easy to control can be obtained inside.

The "appropriate external force" refers to an external force that disperses the aggregated state without destroying the crystallites of the metal composite compound. In the present embodiment, it is preferable to use a grinder as the grinder at the time of the above grind, and a millstone grinder is particularly preferable. When a stone mill type grinder is used, it is preferable to adjust the clearance between the upper mill and the lower mill according to the aggregated state of the metal composite hydroxide. The clearance between the upper mortar and the lower mortar is preferably in the range of 10 μm or more and 200 μm or less, for example.

In the above example, the nickel-cobalt-manganese composite hydroxide is produced, but the nickel-cobalt-manganese composite oxide may be prepared.

For example, a nickel cobalt manganese composite oxide can be prepared by firing a nickel cobalt manganese composite hydroxide. The firing time is preferably 1 hour or more and 30 hours or less, which is the total time from the start of temperature rise to the end of temperature retention. The rate of temperature rise in the heating step to reach the maximum holding temperature is preferably 180 ° C./hr or more, more preferably 200 ° C./hr or more, and particularly preferably 250 ° C./hr or more.

The maximum holding temperature in the present specification is the maximum holding temperature of the atmosphere in the firing furnace in the firing step, and means the firing temperature in the firing step. In the case of the main firing step having a plurality of heating steps, the maximum holding temperature means the maximum temperature of each heating step.

The heating rate in the present specification is the time from the start of temperature rise to the maximum holding temperature in the firing apparatus, and the temperature from the start of temperature rise in the firing furnace of the firing apparatus to the maximum holding temperature. It is calculated from the temperature difference.

(Manufacturing process of lithium metal composite oxide)
The metal composite oxide or metal composite hydroxide is dried and then mixed with a lithium salt. Further, in the present embodiment, it is preferable to mix the inert melting agent at the same time as this mixing.

By firing a mixture containing an inert melt containing a metal composite oxide or a metal composite hydroxide, a lithium salt and an inert melt, the mixture is fired in the presence of the inert melt. By firing in the presence of an inert melting agent, it is possible to prevent the primary particles from sintering each other to generate secondary particles. In addition, the growth of single particles can be promoted.

In the present embodiment, the drying conditions are not particularly limited.
For example, under the condition that the metal composite oxide or the metal composite hydroxide is not oxidized / reduced (the oxide is maintained as an oxide, the hydroxide is maintained as a hydroxide), the metal composite hydroxide is used. Either the condition of being oxidized (the hydroxide is oxidized to the oxide) or the condition of reducing the metal composite oxide (the oxide is reduced to the hydroxide) may be used.

An inert gas such as nitrogen, helium, or argon may be used for the condition where oxidation / reduction is not performed, and oxygen or air may be used under the condition where the hydroxide is oxidized.

Further, as a condition for reducing the metal composite oxide, a reducing agent such as hydrazine or sodium sulfite may be used in an inert gas atmosphere.

As the lithium salt, any one or a mixture of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, and lithium oxide can be used.

After drying the metal composite oxide or the metal composite hydroxide, classification may be performed as appropriate.

The above lithium salt and metal composite hydroxide are used in consideration of the composition ratio of the final target product. For example, when using a nickel-cobalt-manganese composite hydroxide, lithium salt and the metal complex hydroxide _is used in a proportion corresponding to _{LiNi a Co b Mn c O 2} ( where, a + b + c = 1 ) composition ratio of .. Further, in the lithium metal composite oxide which is the final target product, when lithium is excessive (the molar content ratio is more than 1), the lithium contained in the lithium salt and the metal element contained in the metal composite hydroxide Mix so that the molar ratio of is more than 1.

A lithium-nickel cobalt manganese composite oxide is obtained by calcining a mixture of a nickel cobalt manganese metal composite hydroxide and a lithium salt. For firing, dry air, an oxygen atmosphere, an inert atmosphere, or the like is used according to the desired composition, and a plurality of heating steps are carried out if necessary.

In the present embodiment, the mixture may be fired in the presence of an inert melting agent. Firing in the presence of the Inactive Melting Agent can accelerate the reaction of the mixture. The inert melting agent may remain in the lithium metal composite oxide after firing, or may be removed by washing with water or alcohol after firing. In the present embodiment, it is preferable to wash the lithium metal composite oxide after firing with water or alcohol.

By adjusting the holding temperature in firing, the particle size of the obtained single particles of the lithium metal composite oxide can be controlled within a preferable range of the present embodiment.

Generally, the higher the holding temperature, the larger the particle size of the single particle and the smaller the BET specific surface area tends to be. The holding temperature in firing may be appropriately adjusted according to the type of transition metal element used, the type and amount of the precipitant and the inert melting agent.

In the present embodiment, the holding temperature may be set in consideration of the melting point of the inert melting agent, which will be described later, in the range of the melting point of the inert melting agent minus 100 ° C. or higher and the melting point of the inert melting agent plus 100 ° C. or lower. Is preferable.

Specific examples of the holding temperature include a range of 200 ° C. or higher and 1150 ° C. or lower, preferably 300 ° C. or higher and 1050 ° C. or lower, and more preferably 500 ° C. or higher and 1000 ° C. or lower.

The time for holding at the holding temperature is 0.1 hour or more and 20 hours or less, preferably 0.5 hours or more and 10 hours or less. The rate of temperature rise to the holding temperature is usually 50 ° C./hour or more and 400 ° C./hour or less, and the rate of temperature decrease from the holding temperature to room temperature is usually 10 ° C./hour or more and 400 ° C./hour or less. Further, as the firing atmosphere, air, oxygen, nitrogen, argon or a mixed gas thereof can be used.

The lithium metal composite oxide obtained by firing is appropriately classified after pulverization to obtain a positive electrode active material applicable to a lithium secondary battery.

In the present embodiment, the lithium metal composite oxide obtained by calcination is pulverized by applying an appropriate external force to adjust the dispersed state of the particles, thereby satisfying the above requirements (2) and (3) within the scope of the present embodiment. A controlled lithium metal composite oxide can be obtained within.

In the present embodiment, the lithium metal composite oxide obtained by calcination is pulverized by applying an appropriate external force to adjust the dispersed state of the particles, thereby satisfying the above requirements (2) and (3) within the scope of the present embodiment. A controlled lithium metal composite oxide can be obtained within.

The "appropriate external force" refers to an external force that disperses the agglomerated state without destroying the crystallites of the lithium metal composite oxide. In the present embodiment, it is preferable to use a grinder as the grinder at the time of the above grind, and a millstone grinder is particularly preferable. When a stone mill type grinder is used, it is preferable to adjust the clearance between the upper mill and the lower mill according to the aggregated state of the lithium metal composite oxide. The clearance between the upper mortar and the lower mortar is preferably in the range of 10 μm or more and 200 μm or less, for example.

The inert melting agent that can be used in the present embodiment is not particularly limited as long as it does not easily react with the mixture during firing. In the present embodiment, a fluoride of one or more elements (hereinafter referred to as “A”) selected from the group consisting of Na, K, Rb, Cs, Ca, Mg, Sr and Ba, and a chloride of A. , A carbonate, A sulfate, A nitrate, A phosphate, A hydroxide, A molybdate and A tungstate, one or more selected from the group. ..

The fluorides of A include NaF (melting point: 993 ° C.), KF (melting point: 858 ° C.), RbF (melting point: 795 ° C.), CsF (melting point: 682 ° C.), CaF ₂ (melting point: 1402 ° C.), MgF ₂ (Melting point: 1263 ° C.), SrF ₂ (melting point: 1473 ° C.) and BaF ₂ (melting point: 1355 ° C.).

Chlorides of A include NaCl (melting point: 801 ° C.), KCl (melting point: 770 ° C.), RbCl (melting point: 718 ° C.), CsCl (melting point: 645 ° C.), CaCl ₂ (melting point: 782 ° C.), MgCl ₂ (Melting point: 714 ° C.), SrCl ₂ (melting point: 857 ° C.) and NaCl ₂ (melting point: 963 ° C.).

The carbonates of A include Na ₂ CO ₃ (melting point: 854 ° C), K ₂ CO ₃ (melting point: 899 ° C), Rb ₂ CO ₃ (melting point: 837 ° C), Cs ₂ CO ₃ (melting point: 793 ° C). , CaCO ₃ (melting point: 825 ° C.), MgCO ₃ (melting point: 990 ° C.), SrCO ₃ (melting point: 1497 ° C.) and BaCO ₃ (melting point: 1380 ° C.).

Sulfates of A include Na ₂ SO ₄ (melting point: 884 ° C), K ₂ SO ₄ (melting point: 1069 ° C), Rb ₂ SO ₄ (melting point: 1066 ° C), Cs ₂ SO ₄ (melting point: 1005 ° C). , CaSO ₄ (mp: 1460 ℃), MgSO ₄ (mp: 1137 ℃), SrSO ₄ (mp: 1605 ° C.) and BaSO ₄ (mp: 1580 ° C.) can be mentioned.

The nitrates of A include NaNO ₃ (melting point: 310 ° C), KNO ₃ (melting point: 337 ° C), RbNO ₃ (melting point: 316 ° C), CsNO ₃ (melting point: 417 ° C), Ca (NO ₃ ) ₂ (melting point). : 561 ° C.), Mg (NO ₃ ) ₂ , Sr (NO ₃ ) ₂ (melting point: 645 ° C.) and Ba (NO ₃ ) ₂ (melting point: 596 ° C.).

Phosphates of A include Na ₃ PO ₄ , K ₃ PO ₄ (melting point: 1340 ° C), Rb ₃ PO ₄ , Cs ₃ PO ₄ , Ca ₃ (PO ₄ ) ₂ , Mg ₃ (PO ₄ ) ₂ ( Melting point: 1184 ° C.), Sr ₃ (PO ₄ ) ₂ (melting point: 1727 ° C.) and Ba ₃ (PO ₄ ) ₂ (melting point: 1767 ° C.).

Hydroxides of A include NaOH (melting point: 318 ° C.), KOH (melting point: 360 ° C.), RbOH (melting point: 301 ° C.), CsOH (melting point: 272 ° C.), Ca (OH) ₂ (melting point: 408 ° C.). ), Mg (OH) ₂ (melting point: 350 ° C.), Sr (OH) ₂ (melting point: 375 ° C.) and Ba (OH) ₂ (melting point: 853 ° C.).

Examples of the molybdate of A include Na ₂ MoO ₄ (melting point: 698 ° C), K ₂ MoO ₄ (melting point: 919 ° C), Rb ₂ MoO ₄ (melting point: 958 ° C), and Cs ₂ MoO ₄ (melting point: 956 ° C). ), CaMoO ₄ (melting point: 1520 ° C.), MgMoO ₄ (melting point: 1060 ° C.), SrMoO ₄ (melting point: 1040 ° C.) and BaMoO ₄ (melting point: 1460 ° C.).

The tungstate A, _Na 2 WO ₄ (mp: 687 ° _C.), can be exemplified _{K 2 WO 4, Rb 2 WO} 4, Cs 2 WO 4, CaWO 4, MgWO 4, SrWO 4 and BaWO ₄ ..

In the present embodiment, two or more kinds of these inert melting agents can be used. When two or more are used, the melting point may decrease. Among these inert melting agents, the inert melting agent for obtaining a lithium metal composite oxide having higher crystallinity is any one or a combination of carbonate and sulfate of A and chloride of A. Is preferable. Further, as A, it is preferable that either one or both of sodium (Na) and potassium (K) are used. That is, among the above, the particularly preferable inert melting agent is at least one selected from the group consisting of NaCl, KCl, Na ₂ CO ₃ , K ₂ CO _3, Na ₂ SO _4, and K ₂ SO _4. ..
By using these inert melting agents, the average crushing strength of the obtained lithium metal composite oxide can be controlled within a preferable range of the present embodiment.

In the present embodiment, when either one or both of K ₂ SO ₄ and Na ₂ SO ₄ are used as the inert melting agent, the average crushing strength of the obtained lithium metal composite oxide is preferable in the present embodiment. Can be controlled to a range.

In the present embodiment, the abundance of the inert melting agent at the time of firing may be appropriately selected. In order to keep the average crushing strength of the obtained lithium metal composite oxide within the range of the present embodiment, the abundance of the inert melting agent at the time of firing is 0.1 part by mass or more with respect to 100 parts by mass of the lithium compound. It is preferably 1 part by mass or more, and more preferably 1 part by mass or more. Further, if necessary, an inert melting agent other than the above-mentioned inert melting agents may be used in combination. Examples of the melting agent include ammonium salts such as NH ₄ Cl and NH ₄ F.

(Covering layer forming process)
When forming a coating layer on the particle surface of the positive electrode active material, first, the coating material raw material and the lithium metal composite oxide are mixed. Next, a coating layer made of the lithium metal composite oxide can be formed on the surface of the particles of the lithium metal composite oxide by heat treatment if necessary.

Depending on the coating material raw material, when the metal composite oxide or hydroxide is mixed with the lithium salt in the above-mentioned manufacturing process of the lithium metal composite oxide, the coating material raw material can be further added and mixed.

The coating material raw material is an oxide of the above-mentioned lithium salt and at least one element selected from the group consisting of Nb, Ge, Si, P, Al, W, Ta, Ti, S, Zr, Zn, V and B. , Hydroxides, carbonates, nitrates, sulfates, halides, oxalates or alkoxides can be used. The compound containing at least one element selected from the group consisting of Nb, Ge, Si, P, Al, W, Ta, Ti, S, Zr, Zn, V and B is preferably an oxide.

Examples of the coating material raw material include aluminum oxide, aluminum hydroxide, aluminum sulfate, aluminum chloride, aluminum alkoxide, boron oxide, boric acid and the like, and aluminum oxide, aluminum hydroxide, boron oxide, boric acid, niobium oxide and niobate. Lithium, lithium borate, lithium phosphate, lithium silicate are preferable.

In order to more efficiently coat the surface of the lithium metal composite oxide with the coating material raw material, the coating material raw material is preferably fine particles as compared with the secondary particles of the lithium metal composite oxide. Specifically, the average secondary particle size of the coating material raw material is preferably 1 μm or less, and more preferably 0.1 μm or less.

The smaller the lower limit of the average secondary particle size of the coating material is, the more preferable, but it is, for example, 0.001 μm. The average secondary particle size of the coating material raw material can be measured by the same method as the average secondary particle size of the lithium metal composite oxide.

The coating material and the lithium metal composite oxide are mixed uniformly until there are no agglomerates. The mixing apparatus is not limited as long as the coating material raw material and the lithium metal composite oxide can be uniformly mixed, but it is preferable to mix them using a Ladyge mixer. The same applies to the case where the coating material raw material is added and mixed in the mixing step of mixing the metal composite oxide or hydroxide and the lithium salt.

Further, by performing the mixing in water or an atmosphere containing water and carbon dioxide gas, the coating layer can be more firmly adhered to the surface of the lithium metal composite oxide.

The coating layer can also be more firmly adhered to the surface of the lithium metal composite oxide by retaining the coating material raw material and the lithium metal composite oxide in an atmosphere containing water or water and carbon dioxide gas after mixing.

The heat treatment conditions (temperature, holding time) in the heat treatment performed as necessary after mixing the coating material raw material and the lithium metal composite oxide may differ depending on the type of the coating material raw material.

For example, when aluminum is used as a coating raw material, it is preferable to bake in a temperature range of 600 ° C. or higher and 800 ° C. or lower for 4 hours or more and 10 hours or less. By firing under the firing conditions of this high temperature for a long time, the range of the above requirements (1) and (2) can be controlled. If the firing temperature is higher than 800 ° C., the coating material raw material may be solid-solved with the lithium metal composite oxide, and the coating layer may not be formed. If the firing time is shorter than 4 hours, the coating material may not be diffused sufficiently and the coating layer may not be formed uniformly.

The firing temperature in the present specification means the temperature of the atmosphere in the firing furnace, and is the maximum holding temperature in the main firing step (hereinafter, may be referred to as the maximum holding temperature), and a plurality of heating steps are performed. In the case of the main firing step having, it means the temperature when heating at the maximum holding temperature in each heating step.

By using techniques such as sputtering, CVD, vapor deposition, and spray coating, a coating layer can be formed on the surface of the lithium metal composite oxide to obtain a positive electrode active material for a lithium secondary battery.

Further, a positive electrode active material for a lithium secondary battery may be obtained by mixing and firing the metal composite oxide or hydroxide, a lithium salt and a coating material raw material.

The particles having a coating layer formed on the surface of the primary particles or the secondary particles of the lithium metal composite oxide are appropriately crushed and classified to be a positive electrode active material for a lithium secondary battery.

<Manufacturing method of positive electrode active material 2>
When the positive electrode active material of the present embodiment contains single particles and secondary particles, the positive electrode active material can be produced by making the following changes from the above-mentioned positive electrode active material production method 1.

(Manufacturing process of metal composite compound)
In the method 2 for producing a positive electrode active material, in the process of producing a metal composite compound, a metal composite compound that finally forms a single particle and a metal composite compound that forms a secondary particle are produced, respectively. Hereinafter, the metal composite compound that finally forms a single particle may be referred to as a “single particle precursor”. In addition, the metal composite compound that finally forms secondary particles may be referred to as "secondary particle precursor".

In the method 2 for producing a positive electrode active material, when a metal composite compound is produced by the above-mentioned coprecipitation method, a first coprecipitation tank for producing a single particle precursor and a second coprecipitation tank for forming a secondary particle precursor are formed. Use a co-precipitation tank.

A single particle precursor can be produced by appropriately controlling the concentration of the metal salt supplied to the first coprecipitation tank, the stirring speed, the reaction temperature, the reaction pH, the firing conditions described later, and the like.

Specifically, the temperature of the reaction vessel is preferably, for example, 30 ° C. or higher and 80 ° C. or lower, more preferably controlled within the range of 40 to 70 ° C., and the range of ± 20 ° C. with respect to the second reaction vessel described later. Is more preferable. Further, the pH value in the reaction vessel is preferably, for example, pH 10 or more and pH 13 or less, more preferably controlled in the range of pH 11 or more and pH 12.5 or less, and in the range of ± pH 2 or less with respect to the second reaction tank described later. It is even more preferable that the pH is higher than that of the second reaction vessel.

Further, the secondary particle precursor can be produced by appropriately controlling the concentration of the metal salt supplied to the second coprecipitation tank, the stirring speed, the reaction temperature, the reaction pH, the firing conditions described later, and the like.

Specifically, the temperature of the reaction vessel is preferably, for example, 20 ° C. or higher and 80 ° C. or lower, more preferably controlled in the range of 30 to 70 ° C., and in the range of ± 20 ° C. with respect to the second reaction vessel described later. Is more preferable. Further, the pH value in the reaction vessel is preferably, for example, pH 10 or more and pH 13 or less, more preferably controlled in the range of pH 11 or more and pH 12.5 or less, and in the range of ± pH 2 or less with respect to the second reaction tank described later. It is more preferable that the pH is lower than that of the second reaction tank.

The reaction products thus obtained are washed with water and then dried to isolate nickel-cobalt-manganese hydroxide (single particle precursor, secondary particle precursor).

In the above example, the nickel-cobalt-manganese composite hydroxide is produced, but the nickel-cobalt-manganese composite oxide may be prepared.

(Manufacturing process of lithium metal composite oxide)
In the process for producing a lithium metal composite oxide, the single particle precursor, the metal composite oxide as the secondary particle precursor, or the metal composite hydroxide obtained in the above step is dried and then mixed with a lithium salt. To do. The single particle precursor and the secondary particle precursor may be appropriately classified after drying.

By mixing the single particle precursor and the secondary particle precursor at a predetermined mass ratio at the time of mixing, the abundance ratio of the obtained single particle and the secondary particle can be roughly controlled.

In the steps after mixing, the single particle precursor and the secondary particle precursor are aggregated or separated from each other, and there are also secondary particles based on the single particle precursor or single particles based on the secondary particle precursor. However, by adjusting the mixing ratio of the single particle precursor and the secondary particle precursor and the conditions of the steps after mixing, the presence of the single particle and the secondary particle in the finally obtained lithium metal composite oxide. The ratio can be controlled.

By adjusting the holding temperature during firing, the average particle size of the single particles and the average particle size of the secondary particles of the obtained lithium metal composite oxide can be controlled within the preferable ranges of the present embodiment.

<Manufacturing method of positive electrode active material 3>
When the positive electrode active material of the present embodiment contains single particles and secondary particles, the first lithium metal composite oxide composed of the single particles and the secondary particles are obtained by the above-mentioned production method 1 of the positive electrode active material. It can be produced by producing a second lithium metal composite oxide composed of the above, respectively, and mixing the first lithium metal composite oxide and the second lithium metal composite oxide.

In the method 3 for producing the positive electrode active material, in the process of producing the lithium metal composite oxide, the holding temperature when firing the first lithium metal composite oxide is set to the holding temperature when firing the second lithium metal composite oxide. It should be higher than the holding temperature. Specifically, when producing the first lithium metal composite oxide, it is preferably 30 ° C. or higher, more preferably 50 ° C. or higher, and 80 ° C. higher than the holding temperature of the second lithium metal composite oxide. It is more preferable that the value is higher than that.

By mixing the obtained first lithium metal composite oxide and the second lithium metal composite oxide in a predetermined ratio, a lithium metal composite oxide containing single particles and secondary particles can be obtained.

<All-solid-state lithium-ion battery>
Next, while explaining the configuration of the all-solid lithium-ion battery, a positive electrode using the positive electrode active material for a secondary battery according to one aspect of the present invention as the positive electrode active material of the all-solid lithium-ion battery, and an all-solid having this positive electrode. A lithium ion battery will be described.

2 and 3 are schematic views showing an example of the all-solid-state lithium-ion battery of the present embodiment. FIG. 2 is a schematic view showing a laminate included in the all-solid-state lithium-ion battery of the present embodiment. FIG. 3 is a schematic view showing the overall configuration of the all-solid-state lithium-ion battery of the present embodiment.

The all-solid-state secondary battery 1000 has a positive electrode 110, a negative electrode 120, a laminated body 100 having a solid electrolyte layer 130, and an exterior body 200 containing the laminated body 100.
The materials constituting each member will be described later.

The laminate 100 may have an external terminal 113 connected to the positive electrode current collector 112 and an external terminal 123 connected to the negative electrode current collector 122. In addition, the all-solid-state secondary battery 1000 may have a separator between the positive electrode 110 and the negative electrode 120 as used in a conventional liquid-based lithium ion secondary battery.

The all-solid-state secondary battery 1000 has an insulator (not shown) that insulates the laminate 100 and the exterior body 200, and a sealant (not shown) that seals the opening 200a of the exterior body 200.

As the exterior body 200, a container formed of a metal material having high corrosion resistance such as aluminum, stainless steel, and nickel-plated steel can be used. Further, it is also possible to use a container in which a laminated film having a corrosion resistant treatment on at least one surface is processed into a bag shape.

Examples of the shape of the all-solid-state lithium-ion battery 1000 include a coin type, a button type, a paper type (or a sheet type), a cylindrical type, and a square type.

The all-solid-state secondary battery 1000 is illustrated as having one laminate 100, but is not limited to this. The all-solid-state secondary battery 1000 may have a configuration in which the laminated body 100 is used as a unit cell and a plurality of unit cells (laminated body 100) are sealed inside the exterior body 200.

Hereinafter, each configuration will be described in order.

(Positive electrode)
The positive electrode 110 of the present embodiment has a positive electrode active material layer 111 and a positive electrode current collector 112.

The positive electrode active material layer 111 contains the positive electrode active material which is one aspect of the present invention described above. Further, the positive electrode active material layer 111 may contain a solid electrolyte (second solid electrolyte), a conductive material, and a binder.

(Solid electrolyte)
As the solid electrolyte that the positive electrode active material layer 111 of the present embodiment may have, a solid electrolyte that has lithium ion conductivity and is used in a known all-solid-state battery can be adopted. Examples of such a solid electrolyte include an inorganic electrolyte and an organic electrolyte. Examples of the inorganic electrolyte include an oxide-based solid electrolyte, a sulfide-based solid electrolyte, and a hydride-based solid electrolyte. Examples of the organic electrolyte include polymer-based solid electrolytes.

(Oxide-based solid electrolyte)
Examples of the oxide-based solid electrolyte include perovskite-type oxides, NASICON-type oxides, LISION-type oxides, garnet-type oxides, and the like.

Examples of the perovskite-type oxide include Li-La-Ti-based oxides such as Li _a La _1-a TIO ₃ (0 <a <1) and Li _b La _1-b TaO ₃ (0 <b <1). Examples thereof include Li-La-Ta-based oxides and Li-La-Nb-based oxides such as Li _c La _1-c NbO ₃ (0 <c <1).

Examples of the NASICON type oxide include Li _{1 + d} Al _d Ti _2-d (PO ₄ ) ₃ (0 ≦ d ≦ 1). NASICON type ^{_{oxide, Li m M 1 n M 2}} o P p O q ( wherein, ^{M 1} is, selected B, Al, Ga, In, C, Si, Ge, Sn, from the group consisting of Sb and Se one or more elements .M ² to the Ti, Zr, Ge, an in, Ga, one or more elements selected from the group consisting of Sn and Al .m, n, o, p and q are arbitrary positive It is an oxide represented by a number.).

As the LISION type oxide, Li ₄ M ³ O _4- Li ₃ M ⁴ O ₄ (M ³ is one or more elements selected from the group consisting of Si, Ge, and Ti. M ⁴ is P, As. And an oxide represented by one or more elements selected from the group consisting of V.).

Examples of the garnet-type oxide include Li-La-Zr-based oxides such as Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ).

The oxide-based solid electrolyte may be a crystalline material or an amorphous material. As amorphous solid electrolytes such as Li-BO compounds such as _{Li 3 BO 3, Li 2 B} 4 O 7, LiBO 2 and the like. The oxide-based solid electrolyte preferably contains an amorphous material.

(Sulfide-based solid electrolyte)
Examples of the sulfide-based solid electrolyte include Li ₂ SP ₂ S ₅ series compounds, Li ₂ S-SiS ₂ series compounds, Li ₂ S-GeS ₂ series compounds, Li ₂ SB ₂ S ₃ series compounds, and Li _{2 S-P} 2 S ₃ type _{compound, LiI-Si 2 S-P} 2 S 5, LiI-Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 S 5, Li 10 GeP 2 S 12 etc. Can be mentioned.

In addition, in this specification, the expression "system compound" which refers to a sulfide-based solid electrolyte is a solid electrolyte mainly containing raw materials such as "Li ₂ S" and "P ₂ S ₅ " described before "system compound". It is used as a general term for. For example, the Li ₂ SP ₂ S ₅ system compound contains a solid electrolyte containing Li ₂ S and P ₂ S ₅ and further containing other raw materials. In addition, the Li ₂ SP ₂ S ₅ series compounds also include solid electrolytes having different mixing ratios of Li ₂ S and P ₂ S ₅ .

Li ₂ The _S-P 2 _{S 5} -based _{compounds, Li 2 S-P 2 S} 5, Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 _{S 5 -LiBr, Li 2 S-} P 2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-P 2 S 5 -Z m S n (m, n Is a positive number. Z can be Ge, Zn, Ga) or the like.

Examples of the Li ₂ S-SiS ₂ system compounds include Li ₂ S-SiS ₂ , Li ₂ S-SiS _2- LiI, Li ₂ S-SiS _2- LiBr, Li ₂ S-SiS _2- LiCl, and Li ₂ S-SiS. _2- B ₂ S _3- LiI, Li ₂ S-SiS _2- P ₂ S _5- LiI, Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li ₂ SO ₄ , Li ₂ S −SiS ₂ −Li _x MO _y (x, y are positive numbers. M is P, Si, Ge, B, Al, Ga or In) and the like.

Examples of the Li ₂ S-GeS ₂ system compound include Li ₂ S-GeS ₂ and Li ₂ S-GeS _2- P ₂ S ₅ .

The sulfide-based solid electrolyte may be a crystalline material or an amorphous material. The sulfide-based solid electrolyte preferably contains an amorphous material.

(Hydride-based solid electrolyte)
The hydride-based solid electrolyte _{material, LiBH 4, LiBH 4 -3KI,} LiBH 4 -PI 2, LiBH 4 -P 2 S 5, LiBH 4 -LiNH 2, 3LiBH 4 -LiI, LiNH 2, Li 2 AlH 6, Li (NH ₂ ) ₂ I, Li ₂ NH, LiGd (BH ₄ ) ₃ Cl, Li ₂ (BH ₄ ) (NH ₂ ), Li ₃ (NH ₂ ) I, Li ₄ (BH ₄ ) (NH ₂ ) ₃ And so on.

Examples of the polymer-based solid electrolyte include organic polymer electrolytes such as polyethylene oxide-based polymer compounds, polymer compounds containing one or more selected from the group consisting of polyorganosiloxane chains and polyoxyalkylene chains. .. Further, a so-called gel type compound in which a non-aqueous electrolytic solution is retained in a polymer compound can also be used.

Two or more types of solid electrolytes can be used in combination as long as the effects of the invention are not impaired.

(Conductive material)
As the conductive material that the positive electrode active material layer 111 of the present embodiment may have, a carbon material or a metal compound can be used. Examples of the carbon material include graphite powder, carbon black (for example, acetylene black), and fibrous carbon material. Since carbon black is fine and has a large surface area, it is possible to increase the conductivity inside the positive electrode 110 by adding an appropriate amount to the positive electrode active material layer 111, and improve charge / discharge efficiency and output characteristics. On the other hand, if the amount of carbon black added is too large, the binding force between the positive electrode active material layer 111 and the positive electrode current collector 112 and the binding force inside the positive electrode active material layer 111 both decrease, and the internal resistance is increased. It causes. Examples of the metal compound include metals having electric conductivity, metal alloys and metal oxides.

In the case of a carbon material, the ratio of the conductive material in the positive electrode active material layer 111 is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When a fibrous carbon material such as graphitized carbon fiber or carbon nanotube is used as the conductive material, this ratio can be reduced.

(binder)
When the positive electrode active material layer 111 has a binder, a thermoplastic resin can be used as the binder. Examples of this thermoplastic resin include a polyimide resin, polyvinylidene fluoride (hereinafter, may be referred to as PVdF), polytetrafluoroethylene (hereinafter, may be referred to as PTFE), ethylene tetrafluoride, propylene hexafluoride, and the like. Fluororesin such as vinylidene fluoride-based copolymer, propylene hexafluoride / vinylidene fluoride-based copolymer, ethylene tetrafluoride / perfluorovinyl ether-based copolymer; polyolefin resin such as polyethylene and polypropylene; it can.

Two or more kinds of these thermoplastic resins may be mixed and used. By using a fluorine resin and a polyolefin resin as the binder, the ratio of the fluorine resin to the entire positive electrode active material layer 111 is 1% by mass or more and 10% by mass or less, and the ratio of the polyolefin resin is 0.1% by mass or more and 2% by mass or less. The positive electrode active material layer 111 has a high adhesion between the positive electrode active material layer 111 and the positive electrode current collector 112 and a high bonding force inside the positive electrode active material layer 111.

The positive electrode active material layer 111 may be processed in advance as a sheet-shaped molded body containing the positive electrode active material and used as the “electrode” in the present invention. Further, in the following description, such a sheet-shaped molded body may be referred to as a "positive electrode active material sheet". A laminated body in which a current collector is laminated on a positive electrode active material sheet may be used as an electrode.

The positive electrode active material sheet may contain any one or more selected from the group consisting of the above-mentioned solid electrolyte, conductive material and binder.

The positive electrode active material sheet is prepared by mixing, for example, a positive electrode active material, a sintering aid, the above-mentioned conductive material, the above-mentioned binder, a plasticizer, and a solvent to prepare a slurry, and the obtained slurry is used. It is obtained by applying it on a carrier film and drying it.

As the sintering aid, for example, Li ₃ BO ₃ or Al ₂ O ₃ can be used.

As the plasticizer, for example, dioctyl phthalate can be used.

As the solvent, for example, acetone, ethanol or N-methyl-2-pyrrolidone can be used.

When preparing the slurry, a ball mill can be used for mixing. Since the obtained mixture often contains air bubbles mixed during mixing, it is preferable to reduce the pressure to defoam. When defoaming, a part of the solvent volatilizes and concentrates, so that the slurry becomes highly viscous.

The slurry can be applied using a known doctor blade.

As the carrier film, a PET film can be used.

The positive electrode active material sheet obtained after drying is peeled off from the carrier film and appropriately processed into a required shape by punching before use. Further, the positive electrode active material sheet may be uniaxially pressed in the thickness direction as appropriate.

(Positive current collector)
As the positive electrode current collector 112 included in the positive electrode 110 of the present embodiment, a sheet-shaped member made of a metal material such as Al, Ni, stainless steel, or Au can be used. Of these, Al is used as a forming material and processed into a thin film because it is easy to process and inexpensive.

Examples of the method of supporting the positive electrode active material layer 111 on the positive electrode current collector 112 include a method of pressure molding the positive electrode active material layer 111 on the positive electrode current collector 112. A cold press or a hot press can be used for pressure molding.

Further, a mixture of the positive electrode active material, the solid electrolyte, the conductive material, and the binder is made into a paste using an organic solvent to prepare a positive electrode mixture, and the obtained positive electrode mixture is applied to at least one surface side of the positive electrode current collector 112 and dried. The positive electrode active material layer 111 may be supported on the positive electrode current collector 112 by pressing and fixing.

Further, a mixture of the positive electrode active material, the solid electrolyte, and the conductive material is made into a paste using an organic solvent to prepare a positive electrode mixture, and the obtained positive electrode mixture is applied to at least one surface side of the positive electrode current collector 112, dried, and baked. By connecting, the positive electrode active material layer 111 may be supported on the positive electrode current collector 112.

Examples of the organic solvent that can be used in the positive electrode mixture include amine solvents such as N, N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate. Examples include amide-based solvents such as dimethylacetamide and N-methyl-2-pyrrolidone (hereinafter, may be referred to as NMP).

Examples of the method of applying the positive electrode mixture to the positive electrode current collector 112 include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method and an electrostatic spray method.

The positive electrode 110 can be manufactured by the method described above.

(Negative electrode)
The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122. The negative electrode active material layer 121 contains a negative electrode active material. Further, the negative electrode active material layer 121 may contain a solid electrolyte and a conductive material. As the solid electrolyte, the conductive material, and the binder, those described above can be used.

(Negative electrode active material)
The negative electrode active material of the negative electrode active material layer 121 is a carbon material, a chalcogen compound (oxide, sulfide, etc.), a nitride, a metal, or an alloy, and lithium ions are doped and dedoped at a potential lower than that of the positive electrode 110. Possible materials are mentioned.

Examples of the carbon material that can be used as the negative electrode active material include graphite such as natural graphite and artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and calcined organic polymer compounds.

Oxides that can be used as the negative electrode active material include silicon oxides represented by the formula SiO _x (here, x is a positive real number) such as SiO ₂ , SiO; the formula TiO _x such as TiO ₂ and TiO (here). , X is a positive real number) titanium oxide; V ₂ O ₅ , VO _2, etc. Formula VO _x (where x is a positive real number) vanadium oxide; Fe ₃ O ₄ , Fe ₂ O ₃ , FeO, etc. Iron oxide represented by the formula FeO _x (where x is a positive real number); SnO ₂ , SnO, etc. Formula SnO _x (where x is a positive real number) Tin oxide; Oxide of tungsten represented by the general formula WO _x (where x is a positive real number) such as WO ₃ and WO ₂ ; Li ₄ Ti ₅ O ₁₂ and Li VO ₂ and other lithium and titanium Alternatively, a metal composite oxide containing vanadium; can be mentioned.

Sulfides that can be used as the negative electrode active material include Ti ₂ S ₃ , TiS ₂ , TiS, and other titanium sulfides represented by the formula TiS _x (where x is a positive real number); V ₃ S ₄ , VS. _2. VS, etc. The sulfide of vanadium represented by the formula VS _x (where x is a positive real number); Fe ₃ S ₄ , FeS ₂ , FeS, etc. formula FeS _x (where x is a positive real number) Iron sulfide represented by; Mo ₂ S ₃ , MoS _2, etc. Formula MoS _x (where x is a positive real number) Molybdenum sulfide represented by the formula MoS _x (where x is a positive real number); SnS _2, SnS, etc. formula SnS _x (here, here) Tin sulfide represented by x is a positive real number); WS _{2 and the} like formula WS _x (where x is a positive real number) and represented by tungsten sulfide; Sb ₂ S _{3 and the} like formula SbS _x (here) in, x is antimony represented by a positive real _{number); Se 5 S 3, SeS} 2, SeS formula SeS _x (wherein such, sulfide selenium x is represented by a positive real number); the Can be mentioned.

The nitrides that can be used as the negative electrode active material are Li ₃ N, Li _3-x A _x N (where A is either or both of Ni and Co, and 0 <x <3). Such as lithium-containing nitrides can be mentioned.

These carbon materials, oxides, sulfides, and nitrides may be used alone or in combination of two or more. Further, these carbon materials, oxides, sulfides and nitrides may be either crystalline or amorphous.

Examples of the metal that can be used as the negative electrode active material include lithium metal, silicon metal, and tin metal.

Alloys that can be used as the negative electrode active material include lithium alloys such as Li-Al, Li-Ni, Li-Si, Li-Sn, and Li-Sn-Ni; silicon alloys such as Si-Zn; Sn-Mn, Sn. Also mentioned are tin alloys such as −Co, Sn—Ni, Sn—Cu, Sn—La; alloys such as Cu ₂ Sb, La ₃ Ni ₂ Sn ₇ ;

These metals and alloys are mainly used alone as electrodes after being processed into a foil, for example.

Among the above negative electrode active materials, the potential of the negative electrode 120 hardly changes from the uncharged state to the fully charged state during charging (potential flatness is good), the average discharge potential is low, and the capacity retention rate when repeatedly charged and discharged. A carbon material containing graphite as a main component, such as natural graphite and artificial graphite, is preferably used because of its high value (good cycle characteristics). The shape of the carbon material may be, for example, a flaky shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an agglomerate of fine powder.

Further, among the negative electrode active materials, oxides are preferably used because of high thermal stability and difficulty in forming dendrites (dendritic crystals) due to Li metal. As the shape of the oxide, a fibrous or fine powder agglomerate is preferably used.

(Negative electrode current collector)
Examples of the negative electrode current collector 122 included in the negative electrode 120 include a strip-shaped member made of a metal material such as Cu, Ni, or stainless steel as a forming material. Among them, Cu is used as a forming material and processed into a thin film because it is difficult to form an alloy with lithium and it is easy to process.

As a method of supporting the negative electrode active material layer 121 on the negative electrode current collector 122, a method by pressure molding and a paste-like negative electrode mixture containing the negative electrode active material are applied on the negative electrode current collector 122 as in the case of the positive electrode 110. Examples thereof include a method of coating, drying and then pressing and crimping, and a method of applying a paste-like negative electrode mixture containing a negative electrode active material on the negative electrode current collector 122, drying and then sintering.

(Solid electrolyte layer)
The solid electrolyte layer 130 has the above-mentioned solid electrolyte (first solid electrolyte). When the positive electrode active material layer 111 contains a solid electrolyte, the solid electrolyte (first solid electrolyte) constituting the solid electrolyte layer 130 and the solid electrolyte (second solid electrolyte) contained in the positive electrode active material layer 111 are present. It may be the same substance. The solid electrolyte layer 130 functions as a medium for transmitting lithium ions and also functions as a separator that separates the positive electrode 110 and the negative electrode 120.

The solid electrolyte layer 130 can be formed by depositing an inorganic solid electrolyte on the surface of the positive electrode active material layer 111 of the positive electrode 110 by a sputtering method.

Further, the solid electrolyte layer 130 can be formed by applying a paste-like mixture containing a solid electrolyte to the surface of the positive electrode active material layer 111 of the positive electrode 110 and drying the mixture. After drying, the solid electrolyte layer 130 may be formed by press molding and further pressurizing by a cold isotropic pressurization method (CIP).

Further, the solid electrolyte layer 130 can be formed by forming the solid electrolyte in pellet form in advance, stacking the pellets of the solid electrolyte and the above-mentioned positive electrode active material sheet, and uniaxially pressing them in the stacking direction. The positive electrode active material sheet becomes the positive electrode active material layer 111.

The positive electrode current collector 112 is further arranged on the positive electrode active material layer 111 with respect to the obtained laminate of the positive electrode active material layer 111 and the solid electrolyte layer 130. The solid electrolyte layer 130 and the positive electrode 110 can be formed by uniaxially pressing in the stacking direction and further sintering.

In the laminate 100, the negative electrode 120 is laminated on the solid electrolyte layer 130 provided on the positive electrode 110 as described above by using a known method so that the negative electrode electrolyte layer 121 is in contact with the surface of the solid electrolyte layer 130. It can be manufactured by.

According to the positive electrode active material for an all-solid-state lithium-ion battery having the above configuration, lithium ions can be smoothly exchanged between the positive electrode and the solid electrolyte, and the battery performance can be improved.

According to the electrodes having the above configuration, since the positive electrode active material for the all-solid-state lithium-ion battery described above is provided, the battery performance of the all-solid-state lithium-ion battery can be improved.

The all-solid-state lithium-ion battery having the above configuration has the above-mentioned positive electrode active material for the all-solid-state lithium-ion battery, and therefore exhibits excellent battery performance.

Although a preferred embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to such an example. The various shapes and combinations of the constituent members shown in the above-mentioned examples are examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

<Composition analysis of positive electrode active material>
In the composition analysis of the positive electrode active material produced by the method described later, after dissolving the obtained particles of the positive electrode active material in hydrochloric acid, an inductively coupled plasma emission spectrometer (SSI Nanotechnology Co., Ltd., SPS3000) is used. It was done using.

<Measurement of (D _90- D ₁₀ ) / D ₅₀ >
The ratio (D ₉₀ / D ₁₀ ) of the 90% cumulative volume particle size D _{90 of the} positive electrode active material to the 10% cumulative volume particle size D ₁₀ was calculated by the following method.

First, 0.1 g of the positive electrode active material was put into 50 ml of a 0.2 mass% sodium hexametaphosphate aqueous solution to obtain a dispersion liquid in which the powder was dispersed.

Next, the particle size distribution of the obtained dispersion was measured using a Microtrack MT3300EXII (laser diffraction scattering particle size distribution measuring device) manufactured by Microtrack Bell Co., Ltd., and a volume-based cumulative particle size distribution curve was obtained.

Then, in the obtained cumulative particle size distribution curve, the value of the particle size seen from the fine particle side at the time of 10% accumulation is 10% cumulative volume particle size D ₁₀ (μm), and the particles seen from the fine particle side at the time of 50% accumulation. The diameter value is 50% cumulative volume particle size D ₅₀ (μm), the particle size value seen from the fine particle side at 90% accumulation is 90% cumulative volume particle size D ₉₀ (μm), and the ratio (D _90- D). ₁₀ ) / D ₅₀ was calculated.

<Measurement of crystallite size>
The powder X-ray diffraction measurement of the positive electrode active material was performed using an X-ray diffractometer (X'Pert PRO, PANalytical).

The obtained positive electrode active material is filled in a dedicated substrate, and measurement is performed using a CuKα radiation source under the conditions of diffraction angle 2θ = 10 ° to 90 °, sampling width 0.02 °, and scan speed 4 ° / min. By doing so, a powder X-ray diffraction pattern was obtained.

Using the powder X-ray diffraction pattern comprehensive analysis software JADE5, the peak A appearing in the range of 2θ = 18.7 ° ± 2 ° and the peak appearing in the range of 2θ = 44.6 ° ± 2 ° from the powder X-ray diffraction pattern. The half width was calculated for each of B. Using the obtained full width at half maximum, the crystallite size α and the crystallite size β were calculated by the Scherrer equation.

From the obtained crystallite size α and crystallite size β, the crystallite size ratio α / β was determined.

<Example 1>
(Manufacturing of positive electrode active material 1)
After putting water in a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added to maintain the liquid temperature at 50 ° C.

A nickel sulfate aqueous solution, a cobalt sulfate aqueous solution, and a manganese sulfate aqueous solution are mixed so that the atomic ratio of nickel atom, cobalt atom, and manganese atom is 0.50: 0.20: 0.30 to prepare a mixed raw material solution. Prepared.

Next, the mixed raw material solution and the ammonium sulfate aqueous solution were continuously added as a complexing agent into the reaction vessel under stirring, and nitrogen gas was continuously aerated in the reaction vessel. An aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 11.1, nickel-cobalt-manganese composite hydroxide particles were obtained, washed, and then dehydrated with a centrifuge, washed, dehydrated. The nickel-cobalt-manganese composite hydroxide 1 was obtained by isolating and drying at 120 ° C.

Nickel cobalt manganese composite hydroxide particles 1 and lithium hydroxide powder are weighed and mixed so that Li / (Ni + Co + Mn) = 1.05, and then fired at 970 ° C. for 4 hours in an air atmosphere to activate the positive electrode. Substance 1 was obtained.

(Evaluation of positive electrode active material 1)
When the composition of the positive electrode active material 1 was analyzed and corresponded to the composition formula (1), it was x = 0.05, y = 0.50, z = 0.30, w = 0.

As a result of SEM observation of the positive electrode active material 1, primary particles and secondary particles were contained, and single particles were not contained.

When the particle size distribution of the positive electrode active material 1 was measured, D ₅₀ was 10.86 and (D _90- D ₁₀ ) / D ₅₀ was 1.16.

When the positive electrode active material 1 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 1.10.

<Example 2>
(Manufacturing of positive electrode active material 2)
After putting water in a reaction vessel equipped with a stirrer and an overflow pipe, an aqueous sodium hydroxide solution was added to maintain the liquid temperature at 50 ° C.

The nickel sulfate aqueous solution, the cobalt sulfate aqueous solution, and the manganese sulfate aqueous solution are mixed so that the atomic ratio of the nickel atom, the cobalt atom, and the manganese atom is 0.55: 0.25: 0.25, and the mixed raw material liquid 2 is prepared. Prepared.

Next, the mixed raw material solution and the ammonium sulfate aqueous solution were continuously added as a complexing agent into the reaction vessel under stirring. An aqueous sodium hydroxide solution was added dropwise at appropriate times so that the pH of the solution in the reaction vessel became 12.0 to obtain nickel-cobalt-manganese composite hydroxide particles. The obtained nickel-cobalt-manganese composite hydroxide particles were washed, dehydrated with a centrifuge, washed, dehydrated, isolated, and dried at 120 ° C. to obtain nickel-cobalt-manganese composite hydroxide 2.

Nickel cobalt manganese composite hydroxide particles 2 and lithium hydroxide monohydrate powder are weighed and mixed so that Li / (Ni + Co + Mn) = 1.03, and then fired at 650 ° C. for 5 hours in an oxygen atmosphere. Then, it was fired at 960 ° C. for 5 hours in an oxygen atmosphere and further fired at 400 ° C. for 5 hours in an air atmosphere to obtain a lithium metal composite oxide. The obtained lithium metal composite oxide was used as the positive electrode active material 2.

(Evaluation of positive electrode active material 2)
When the composition of the positive electrode active material 2 was analyzed and the composition was made to correspond to the composition formula (1), x = 0.03, y = 0.20, z = 0.25, and w = 0.

As a result of SEM observation of the positive electrode active material 2, single particles were contained.

When the particle size distribution of the positive electrode active material 2 was measured, D ₅₀ was 3.52 and (D _90- D ₁₀ ) / D ₅₀ was 0.91.

When the positive electrode active material 2 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 1.89.

<Example 3>
(Manufacturing of positive electrode active material 3)
Nickel cobalt manganese composite hydroxide particles 2 and lithium hydroxide monohydrate powder are weighed and mixed so that Li / (Ni + Co + Mn) = 1.05, and then fired at 650 ° C. for 5 hours in an oxygen atmosphere. Then, it was fired at 1015 ° C. for 5 hours in an oxygen atmosphere, and further fired at 400 ° C. for 5 hours in an air atmosphere to obtain a lithium metal composite oxide.

The obtained lithium metal composite oxide was pulverized with a pin mill type crusher (Impact Mill AVIS100, manufactured by Mill System Co., Ltd.) and then sieved with a turbo screener (TS125 × 200 type, manufactured by Freund Turbo Co., Ltd.). The operating conditions of the pin mill type crusher and turbo screener are as follows.
(Pin mill type crusher operating conditions)
Rotation speed: 16000 rpm, supply speed: 8 kg / hr
(Turbo screener operating conditions)
Screen used: 45 μm mesh, blade rotation speed: 1800 rpm, supply speed: 50 kg / hr

The positive electrode active material 3 was obtained by recovering the powder that had passed through the screen in the turbo screener.

(Evaluation of positive electrode active material 3)
When the composition of the positive electrode active material 3 was analyzed and made to correspond to the composition formula (1), x = 0.05, y = 0.20, z = 0.25, and w = 0.

As a result of SEM observation of the positive electrode active material 3, single particles were contained.

When the particle size distribution of the positive electrode active material 3 was measured, D ₅₀ was 5.41 and (D _90- D ₁₀ ) / D ₅₀ was 0.90.

When the positive electrode active material 3 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 1.94.

<Example 4>
(Manufacturing of positive electrode active material 4)
A mixed raw material solution is prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate so that the atomic ratio of nickel atom, cobalt atom, and manganese atom is 0.88: 0.08: 0.04. Nickel-cobalt-manganese composite hydroxide 4 was obtained in the same manner as in Example 1 except that the aqueous solution of sodium hydroxide was added dropwise in a timely manner so that the pH of the solution in the reaction vessel was 12.4. ..

Nickel cobalt manganese composite hydroxide 4, lithium hydroxide powder, and potassium sulfate powder are mixed with Li / (Ni + Co + Mn) = 1.05, K ₂ SO ₄ / (LiOH + K ₂ SO ₄ ) = 0.1 (mol / mol / After weighing and mixing so as to be mol), the mixture was calcined at 800 ° C. for 10 hours in an oxygen atmosphere to obtain a mixture 4 containing a lithium metal composite oxide.

The mixture 4 and pure water (water temperature 5 ° C.) were mixed so that the ratio of the mixture 4 to the total amount of the mixture 4 and pure water was 30% by mass, and the obtained slurry was stirred for 10 minutes.

The slurry was dehydrated, and the obtained solid was rinsed with pure water (liquid temperature 5 ° C.) having twice the mass of the mixture 4 used for preparing the slurry (rinse step). The solid material was dehydrated again, vacuum dried at 80 ° C. for 15 hours, and then vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode active material 4.

(Evaluation of positive electrode active material 4)
When the composition of the positive electrode active material 4 was analyzed and made to correspond to the composition formula (1), x = 0.05, y = 0.08, z = 0.04, and w = 0.

As a result of SEM observation of the positive electrode active material 4, single particles were contained.

When the particle size distribution of the positive electrode active material 4 was measured, D ₅₀ was 5.79 and (D _90- D ₁₀ ) / D ₅₀ was 1.78.

When the positive electrode active material 4 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 1.84.

<Example 5>
(Manufacturing of positive electrode active material 5)
Nickel-cobalt-manganese composite hydroxylation in the same manner as in Example 4, except that an aqueous sodium hydroxide solution was added dropwise to bring the pH of the solution in the reaction vessel to 11.2, and the liquid temperature was maintained at 70 ° C. A precipitate containing the substance was obtained.

The obtained precipitate was pulverized with a counter jet mill (100 AFG type, manufactured by Hosokawa Micron Co., Ltd.) to obtain a nickel cobalt-manganese composite hydroxide 5. The operating conditions of the counter jet mill are as follows.
(Counter jet mill operating conditions)
Crushing pressure: 0.59 MPa, classification rotation speed: 17,000 rpm, supply speed: 2 kg / hr

Nickel cobalt manganese composite hydroxide 5, lithium hydroxide powder, and potassium sulfate powder are mixed with Li / (Ni + Co + Mn) = 1.20, K ₂ SO ₄ / (LiOH + K ₂ SO ₄ ) = 0.1 (mol / mol / A positive electrode active material 5 was obtained in the same manner as in Example 4 except that the mixture was weighed and mixed so as to be mol).

(Evaluation of positive electrode active material 5)
When the composition of the positive electrode active material 5 was analyzed and the composition was made to correspond to the composition formula (1), x = 0.20, y = 0.08, z = 0.04, and w = 0.

As a result of SEM observation of the positive electrode active material 5, single particles were contained.

When the particle size distribution of the positive electrode active material 5 was measured, D ₅₀ was 3.32 and (D _90- D ₁₀ ) / D ₅₀ was 6.32.

When the positive electrode active material 5 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 1.94.

<Example 6>
(Manufacturing of positive electrode active material 6)
A mixed raw material solution is prepared by mixing an aqueous solution of nickel sulfate, an aqueous solution of cobalt sulfate, and an aqueous solution of manganese sulfate so that the atomic ratio of nickel atom, cobalt atom, and manganese atom is 0.91: 0.07: 0.02. Nickel-cobalt-manganese composite hydroxide 6 was obtained in the same manner as in Example 4, except that the aqueous solution of sodium hydroxide was added dropwise in a timely manner so that the pH of the solution in the reaction vessel was 12.3. ..

Nickel cobalt manganese composite hydroxide 6, lithium hydroxide powder, and potassium sulfate powder were mixed with Li / (Ni + Co + Mn) = 1.26, K ₂ SO ₄ / (LiOH + K ₂ SO ₄ ) = 0.1 (mol / mol /). After weighing and mixing so as to be mol), the mixture was fired at 790 ° C. for 10 hours in an oxygen atmosphere to obtain a mixture 6 containing a lithium metal composite oxide.

The mixture 6 and pure water (water temperature 5 ° C.) were mixed so that the ratio of the mixture 6 to the total amount of the mixture 6 and pure water was 30% by mass, and the obtained slurry was stirred for 10 minutes.

The slurry was dehydrated, and the obtained solid was rinsed with pure water (water temperature 5 ° C.) having twice the mass of the mixture 4 used for preparing the slurry (rinse step). The solid was dehydrated again, vacuum dried at 80 ° C. for 15 hours and then vacuum dried at 150 ° C. for 8 hours.

The obtained powder was sieved with a turbo screener (manufactured by Freund Turbo Co., Ltd.) to obtain a positive electrode active material 6. The operating conditions and sieving conditions of the turbo screener were the same as in Example 3.

(Evaluation of positive electrode active material 6)
When the composition of the positive electrode active material 6 was analyzed and the composition was made to correspond to the composition formula (1), x = 0.02, y = 0.07, z = 0.02, and w = 0.

As a result of SEM observation of the positive electrode active material 6, single particles were contained.

When the particle size distribution of the positive electrode active material 6 was measured, D ₅₀ was 4.13 and (D _90- D ₁₀ ) / D ₅₀ was 1.33.

When the positive electrode active material 6 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 2.01.

<Comparative example 1>
(Manufacturing of positive electrode active material E1)
A commercially available product of LiCoO ₂ was evaluated as the positive electrode active material E1. As the positive electrode active material E1, a commercially available product of LiCoO ₂ having a particle size distribution within the range of D50 = 5 μm ± 2 μm was used.

(Evaluation of positive electrode active material E1)
As a result of SEM observation of the positive electrode active material E1, single particles were contained.

When the particle size distribution of the positive electrode active material E1 was measured, D ₅₀ was 6.81 and (D _90- D ₁₀ ) / D ₅₀ was 1.56.

When the positive electrode active material E1 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 0.40.

<Comparative example 2>
(Manufacturing of positive electrode active material E2)
A commercially available product of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ was evaluated as the positive electrode active material E2. As the positive electrode active material E2, a commercially available product of LiNi _0.33 Co _0.33 Mn _0.33 O ₂ having a particle size distribution within the range of D50 = 5 μm ± 2 μm was used.

(Evaluation of positive electrode active material E2)
As a result of SEM observation of the positive electrode active material E2, primary particles and secondary particles were contained, and single particles were not contained.

When the particle size distribution of the positive electrode active material E2 was measured, D ₅₀ was 4.79 and (D _90- D ₁₀ ) / D ₅₀ was 0.89.

When the positive electrode active material E2 was subjected to X-ray diffraction measurement, the crystallite size ratio α / β was 1.13.

<Manufacturing of all-solid-state lithium-ion secondary batteries>
(Manufacturing of positive electrode active material sheet)
The positive electrode active material obtained by the above-mentioned production method and Li ₃ BO ₃ were mixed so as to have a composition of positive electrode active material: Li ₃ BO ₃ = 80:20 (molar ratio) to obtain a mixed powder. A resin binder (ethyl cellulose), a plasticizer (dioctyl phthalate), and a solvent (acetone) are added to the obtained mixed powder. Mixed powder: Resin binder: Plasticizer: Solvent = 100:10:10: 100 (mass) Ratio) was added, and the mixture was mixed using a planetary stirring / defoaming device.

The obtained slurry was defoamed using a planetary stirring / defoaming device to obtain a positive electrode mixture slurry.

Using a doctor blade, the obtained positive electrode mixture slurry was applied onto a PET film, and the coating film was dried to form a positive electrode film having a thickness of 50 μm.

The positive electrode film is peeled from the PET film, punched into a circle with a diameter of 14.5 mm, and further uniaxially pressed at 20 MPa for 1 minute in the thickness direction of the positive electrode film to obtain a positive electrode active material sheet having a thickness of 40 μm. Was done. Li ₃ BO ₃ contained in the positive electrode active material sheet functions as a solid electrolyte in contact with the positive electrode active material in the positive electrode active material sheet. Further, Li ₃ BO ₃ functions as a binder for holding the positive electrode active material in the positive electrode active material sheet.

(Manufacturing of all-solid-state lithium-ion batteries)
A positive electrode active material sheet and a solid electrolyte pellet of Li _6.75 La ₃ Zr _1.75 Nb _0.25 O ₁₂ (manufactured by Toyoshima Seisakusho Co., Ltd.) are laminated and uniaxially pressed in parallel with the lamination direction to form a laminate. Obtained. The solid electrolyte pellet used had a diameter of 14.5 mm and a thickness of 0.5 mm.

A positive electrode current collector (gold leaf, thickness 500 μm) was further superposed on the positive electrode active material sheet of the obtained laminate, and the mixture was heated at 300 ° C. for 1 hour in a state of being pressurized at 100 gf to burn off the organic component. Further, the temperature was raised to 800 ° C. at 5 ° C./min and then sintered at 800 ° C. for 1 hour to obtain a laminate of a solid electrolyte layer and a positive electrode.

Then, the following operation was performed in the glove box in an argon atmosphere.

A negative electrode (Li foil, thickness 300 μm), a negative electrode current collector (stainless steel plate, thickness 50 μm), and a wave washer (made of stainless steel) were further superimposed on the solid electrolyte layer of the laminate of the solid electrolyte layer and the positive electrode.

For the laminated body stacked from the positive electrode to the wave washer, place the positive electrode on the lower lid of the parts for coin-type battery R2032 (manufactured by Hosen Co., Ltd.), stack it on the wave washer, cover it, and crimp it with a crimping machine. , An all-solid-state lithium-ion battery was manufactured.

<Charge / discharge test>
Using the half cell produced by the above method, a charge / discharge test was carried out under the conditions shown below, and the initial charge / discharge efficiency was calculated.

(Charging / discharging conditions)
Test temperature 60 ° C
Maximum charging voltage 4.3V, charging current density 0.01C,
Minimum discharge voltage 2.0V, discharge current density 0.01C, cutoff 0.002C

(Calculation of initial charge / discharge efficiency)
The initial charge / discharge efficiency was calculated from the charge capacity and the discharge capacity when charging / discharging under the above conditions based on the following formula.
Initial charge / discharge efficiency (%)
= Initial discharge capacity (mAh / g) / Initial charge capacity (mAh / g) x 100

<Manufacturing of liquid-based lithium secondary batteries>
(Manufacture of positive electrode for lithium secondary battery)
The positive electrode active material, the conductive material (acetylene black), and the binder (PVdF) obtained by the production method described later are added so as to have a composition of positive electrode active material: conductive material: binder = 92: 5: 3 (mass ratio). To prepare a paste-like positive electrode mixture by kneading. N-methyl-2-pyrrolidone was used as an organic solvent when preparing the positive electrode mixture.

The obtained positive electrode mixture was applied to an Al foil having a thickness of 40 μm as a current collector and vacuum dried at 150 ° C. for 8 hours to obtain a positive electrode for a lithium secondary battery. The electrode area of the positive electrode for the lithium secondary battery was 1.65 cm ² .

(Manufacturing of lithium secondary battery (coin type half cell))
The following operations were performed in a glove box with an argon atmosphere.

Place the positive electrode for the lithium secondary battery manufactured in (Making the positive electrode for the lithium secondary battery) on the lower lid of the part for the coin-type battery R2032 (manufactured by Hosen Co., Ltd.) with the aluminum foil side facing down. A separator (porous polyethylene film) was placed on top.

300 μl of the electrolytic solution was injected therein. As the electrolytic solution, a solution prepared by dissolving LiPF ₆ at a concentration of 1.0 mol / l in a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate was used.

Next, using metallic lithium as the negative electrode, the negative electrode is placed on the upper side of the laminated film separator, the upper lid is closed through a gasket, and the lithium secondary battery (coin type half cell R2032; hereinafter, “half cell”) is crimped with a caulking machine. It may be referred to as).

<Evaluation result>
The evaluation results are shown in Tables 1 to 4. Tables 1 and 2 show the measured values for each positive electrode active material, and Table 3 shows the results of physical property evaluation of the all-solid-state lithium ion secondary battery using each positive electrode active material.

“Me” of “Li / Me” shown in Table 1 indicates the amount of the remaining metal excluding Li among the metals contained in the lithium metal composite oxide constituting the positive electrode active material. Specifically, "Me" indicates the total amount of Ni, Co, Mn, and M. In addition, "ND" in Table 1 indicates "no data".

In addition, Table 4 shows the results of physical property evaluation of the liquid-based lithium ion secondary battery using each positive electrode active material. The results shown in Table 4 are reference examples.

In Table 3, the initial charge capacity was evaluated as follows, and the evaluation results are shown in the “evaluation” column. In the evaluation, ◎ and 〇 were judged to be non-defective products, and △ and × were judged to be defective products.
⊚: Initial charge capacity is 100 mAh / g or more 〇: Initial charge capacity is 40 mAh / g or more and less than 100 mAh / h Δ: Initial charge capacity is 10 mAh / g or more and less than 40 mAh / h ×: Initial charge capacity is less than 10 mAh / g

As a result of the evaluation, the all-solid-state lithium-ion batteries using the positive electrode active materials of Examples 1 to 6 showed a high initial charge capacity, whereas the positive electrode active materials of Comparative Examples 1 and 2 showed an initial charge capacity. Was low.

When a liquid-based lithium ion secondary battery was prepared and evaluated for the positive electrode active materials of Examples and Comparative Examples, it was evaluated that any of the positive electrode active materials could be used satisfactorily as shown in Table 4.

As described above, even if the positive electrode active material operates well in the liquid-based lithium ion secondary battery, the battery performance of the all-solid-state lithium ion secondary battery is significantly different from that of the all-solid-state lithium ion secondary battery. It was found that the positive electrode active material for a solid-state lithium-ion secondary battery exhibits good battery performance.

From the above, it was found that the present invention is useful.

100 ... Laminated body, 110 ... Positive electrode, 111 ... Positive electrode active material layer, 112 ... Positive electrode current collector, 113 ... External terminal, 120 ... Negative electrode, 121 ... Negative electrode electrolyte layer, 122 ... Negative electrode current collector, 123 ... External terminal, 130 ... solid electrolyte layer, 200 ... exterior, 200a ... opening, 1000 ... all-solid secondary battery

Claims (14)

A positive electrode active material for an all-solid-state lithium-ion battery composed of particles containing crystals of a lithium metal composite oxide.
The lithium metal composite oxide has a layered structure and contains at least Li and a transition metal.
Regarding the volume-based cumulative distribution measured by the laser diffraction type particle size distribution measurement, the particle diameters at which the cumulative ratios from the small particle side are 10%, 50%, and 90% are set to D10, D50, and D90, respectively. Then, the relational expression (D90-D10) / D50 ≧ 0.90 holds, and
The crystals have a crystallite size α at a peak in the range of 2θ = 18.7 ± 2 ° and a crystallite at a peak in the range of 2θ = 44.6 ± 2 ° in X-ray diffraction measurement using CuKα ray. A positive electrode active material for an all-solid-state lithium-ion battery having a ratio α / β to size β of 1.0 or more. The positive electrode active material for an all-solid-state lithium-ion battery according to claim 1, which is used for an all-solid-state lithium-ion battery containing an oxide solid electrolyte. The positive electrode active material for an all-solid-state lithium-ion battery according to claim 1 or 2, wherein the transition metal is at least one selected from the group consisting of Ni, Co, Mn, Ti, Fe, V and W. The lithium metal composite oxide is the positive electrode active material for an all-solid-state lithium-ion battery according to claim 3, which is represented by the following formula (1).
_{Li [Li x (Ni (1} -y-z-w) Co y Mn z M w) 1-x] O 2 (1)
(However, M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, B, Mo, Nb, Zn, Sn, Zr, Ga and V, and −0. 10 ≦ x ≦ 0.30, 0 <y ≦ 0.40, 0 ≦ z ≦ 0.40, 0 ≦ w ≦ 0.10. The positive electrode active material for an all-solid-state lithium-ion battery according to claim 4, which satisfies 1-yz-w ≧ 0.50 and y ≦ 0.30 in the above formula (1). The particles are composed of primary particles, secondary particles formed by aggregating the primary particles, and single particles that exist independently of the primary particles and the secondary particles.
The positive electrode active material for an all-solid-state lithium-ion battery according to any one of claims 1 to 5, wherein the content of the single particles in the particles is 20% or more. The positive electrode active material for an all-solid-state lithium-ion battery according to any one of claims 1 to 6, wherein the particles have a coating layer made of a metal composite oxide on the surface of the particles. An electrode containing the positive electrode active material for an all-solid-state lithium-ion battery according to any one of claims 1 to 7. The electrode according to claim 8, further comprising a solid electrolyte. It has a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode.
The solid electrolyte layer contains a first solid electrolyte.
The positive electrode has a positive electrode active material layer in contact with the solid electrolyte layer and a current collector in which the positive electrode active material layer is laminated.
The positive electrode active material layer is an all-solid-state lithium-ion battery including the positive electrode active material for an all-solid-state lithium-ion battery according to any one of claims 1 to 7 or the electrode according to claim 8 or 9. The all-solid-state lithium-ion battery according to claim 10, wherein the positive electrode active material layer includes the positive electrode active material for an all-solid-state lithium-ion battery and a second solid electrolyte. The all-solid-state lithium-ion battery according to claim 11, wherein the first solid electrolyte and the second solid electrolyte are the same substance. The all-solid-state lithium-ion battery according to any one of claims 10 to 12, wherein the first solid electrolyte has an amorphous structure. The all-solid-state lithium-ion battery according to any one of claims 10 to 13, wherein the first solid electrolyte is an oxide solid electrolyte.

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