WO2020003848A1 - Lithium nickel cobalt tungsten oxide having layered rock salt structure - Google Patents

Abstract

Provided is a novel material that may be an active material. The present invention is a lithium nickel cobalt tungsten oxide having a layered rock salt structure which is characterized by being represented by general formula (1). General formula (1): Li_aNi_bCo_cW_dD_eO_fF_g In general formula (1), a, b, c, d, e, f, and g satisfy 0.5≤a≤2, 0.5≤b≤0.97, 0<c<0.5, 0<d<0.5, 0≤e≤0.2, b+c+d+e=1, 1.8≤f≤2.2, and 0≤g≤0.2. D is a doping element.

Description

Lithium nickel cobalt tungsten oxide with layered rock salt structure

The present invention relates to a lithium nickel cobalt tungsten oxide having a layered rock salt structure used as a positive electrode active material of a lithium ion secondary battery.

It is known that various materials are used as a positive electrode active material of a lithium ion secondary battery. Among them, lithium nickel oxide represented by LiNiO ₂ was widely used as a positive electrode active material at the beginning of development of a lithium ion secondary battery as described in Patent Document 1.

In addition, a lithium nickel metal oxide in which a part of nickel of LiNiO ₂ has been replaced by another metal has been developed, and research on a lithium ion secondary battery using the lithium nickel metal oxide as a positive electrode active material has been actively conducted. Has been done. In particular, in recent years, a large number of lithium ion secondary batteries employing a lithium nickel cobalt aluminum oxide having a layered rock salt structure in which part of nickel of LiNiO ₂ is replaced by cobalt and aluminum as a positive electrode active material have been reported.

Patent Literature 2 specifically describes a lithium ion secondary battery employing LiNi _0.81 Co _0.15 Al _0.04 O ₂ as a positive electrode active material.

Patent Literature 3 discloses a lithium ion employing LiNi _0.8 Co _0.16 Al _0.04 O ₂ or LiNi _0.8 Co _0.15 Al _0.04 O _1.9 F _0.1 as a positive electrode active material. A secondary battery is specifically described.

Patent Literature 4 specifically describes a lithium ion secondary battery employing LiNi _0.8 Co _0.15 Al _0.05 O ₂ as a positive electrode active material.

Patent Literature 5 _discloses Li _1.013 Ni _0.831 Co _0.119 Al _0.050 O ₂ , Li _1.013 Ni _0.858 Co _0.123 Al _0.020 O ₂ or Li ₁ as a positive electrode active material. Lithium ion secondary batteries employing _0.013 Ni _0.867 Co _0.098 Al _0.035 O ₂ are specifically described.

JP-A-63-121260 JP 2006-128119 A JP 2006-278341 A JP 2014-139926 A JP-A-2017-195020

However, the demand for a positive electrode active material of a lithium ion secondary battery is increasing, and there is an eager desire to provide a new lithium composite metal oxide that can be a more excellent positive electrode active material.

The present invention has been made in view of such circumstances, and has as its object to provide a new material that can be a positive electrode active material.

As a result of intensive studies by the present inventors, it has been found that a lithium nickel cobalt tungsten oxide having a layered rock salt structure in which part of nickel of LiNiO ₂ is replaced with cobalt and tungsten is a suitable cathode active material. The present invention has been completed based on such findings.

The lithium nickel cobalt tungsten oxide having a layered rock salt structure of the present invention is represented by the following general formula (1).
Formula _{(1) Li a Ni b Co} c W d D e O f F g
In the general formula (1), a, b, c, d, e, f, and g are 0.5 ≦ a ≦ 2, 0.5 ≦ b ≦ 0.97, 0 <c <0.5, 0 < d <0.5, 0 ≦ e ≦ 0.2, b + c + d + e = 1, 1.8 ≦ f ≦ 2.2, and 0 ≦ g ≦ 0.2. D is a doping element.

According to the present invention, a new material that can be a suitable positive electrode active material can be provided.

3 is an SEM image of a lithium nickel cobalt tungsten oxide having a layered rock salt structure of Example 1. 3 is a charge / discharge curve of the lithium ion secondary battery of Example 1. 9 is a charge / discharge curve of the lithium ion secondary battery of Example 3.

Hereinafter, the best mode for carrying out the present invention will be described. Unless otherwise specified, the numerical range “xy” described in this specification includes the lower limit x and the upper limit y. A numerical range can be formed by arbitrarily combining these upper and lower limits and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from within the numerical value range can be set as upper and lower limit numerical values.

Lithium nickel cobalt tungsten oxide having a layered rock salt structure of the present invention (hereinafter, may be abbreviated as LNCW oxide of the present invention. In addition, lithium nickel cobalt tungsten oxide having a layered rock salt structure may be abbreviated as LNCW oxide. Is represented by the following general formula (1).
Formula _{(1) Li a Ni b Co} c W d D e O f F g
In the general formula (1), a, b, c, d, e, f, and g are 0.5 ≦ a ≦ 2, 0.5 ≦ b ≦ 0.97, 0 <c <0.5, 0 < d <0.5, 0 ≦ e ≦ 0.2, b + c + d + e = 1, 1.8 ≦ f ≦ 2.2, and 0 ≦ g ≦ 0.2. D is a doping element.

Ｌ The LNCW oxide of the present invention functions as a positive electrode active material of a lithium ion secondary battery.

Since the valence of lithium is +1 and the valence of oxygen is -2, in the conventional lithium nickel cobalt aluminum oxide, lithium was excluded in order to secure electrical neutrality between the metal and oxygen. The valence of the entire nickel cobalt aluminum is +3. Here, since cobalt and aluminum have a valence of +3 and are stable, it is considered that the valence of nickel is also +3. In the lithium nickel cobalt aluminum oxide, nickel is an element that preferentially contributes to the oxidation reaction during charging.
Then, as the oxidation reaction of lithium nickel cobalt aluminum oxide during charging, one-electron oxidation of Ni ³⁺ → Ni ⁴⁺ + e ⁻ occurs.

Tungsten is present in the LNCW oxide of the present invention. Tungsten has a valence of +6 and is stable. Due to the presence of tungsten with a high oxidation number, it can be said that the LNCW oxide of the present invention allows the presence of nickel having a valence of +2 in addition to nickel having a valence of +3. Then, the oxidation reaction at the time of charging also causes two-electron oxidation of Ni ²⁺ → Ni ⁴⁺ + 2e ⁻ . Therefore, it can be said that the LNCW oxide of the present invention has a large charge / discharge capacity.

In the LNCW oxide of the present invention, nickel is considered to be an element that preferentially contributes to the oxidation-reduction reaction during charge and discharge. Therefore, the value of b in the general formula (1) is determined by the capacity of the LNCW oxide of the present invention. Is a value that greatly affects
b preferably satisfies 0.6 ≦ b ≦ 0.97, more preferably satisfies 0.7 ≦ b ≦ 0.97, and satisfies 0.8 ≦ b ≦ 0.96. More preferred. Also, 0.95 or 0.9 can be adopted as the upper limit of b.

In the general formula (1), c preferably satisfies 0.01 ≦ c ≦ 0.3, more preferably satisfies 0.02 ≦ c ≦ 0.2, and 0.03 ≦ c ≦ 0. .15, more preferably 0.04 ≦ c ≦ 0.1.
In the general formula (1), d preferably satisfies 0.001 ≦ d ≦ 0.3, more preferably satisfies 0.003 ≦ d ≦ 0.2, and 0.004 ≦ d ≦ 0. .1 is more preferable, and it is particularly preferable that 0.005 ≦ d ≦ 0.05 is satisfied.
When the values of c and d greatly change, the size of the primary particles of the LNCW oxide of the present invention may change significantly, or the space group of the crystal structure may change.

a, e, f, and g may be numerical values within the range defined by the general formula (1), and are preferably 0.5 ≦ a ≦ 1.5, 0 <e ≦ 0.15, 1.8 ≦ f ≦ 2.1, 0 <g ≦ 0.15, more preferably 0.8 ≦ a ≦ 1.3, 0 <e ≦ 0.1, 1.9 ≦ f ≦ 2.1, 0 <g ≦ 0 .1 can be exemplified.

D in the general formula (1) is a doping element, which is an element capable of improving the characteristics of the LNCW oxide of the present invention. F in the general formula (1) is also an element capable of improving the characteristics of the LNCW oxide of the present invention.

One preferred embodiment of the general formula (1) is the following general formula (1-1).
Formula _{(1-1) Li a Ni b Co} c W d D 1 e1 D 2 e2 O f F g
In the general formula (1-1), a, b, c, d, e1, e2, f, and g are 0.5 ≦ a ≦ 2, 0.5 ≦ b ≦ 0.97, and 0 <c <0. 5, 0 <d <0.5, 0 ≦ e1 ≦ 0.2, 0 ≦ e2 <0.2, 0 <e1 + e2 ≦ 0.2, b + c + d + e1 + e2 = 1, 1.8 ≦ f ≦ 2.2, 0 ≦ g ≦ 0.2 is satisfied.
D ¹ is Zr, Ca, V, Mn, Cu, Ni, Sn, Tl, Fe, Sr, Ti, Ba, Mo, Y, a rare earth element, Os, Ir, Cd, Re, Bi, Rh, W, Cr, At least one element selected from Co, Zn, In, Al, Li, Na, Pb, Ru, and Nb.
D ² is an element other than ^{Li, Ni, Co, W,} D 1, O, F.

好 適 For the preferred ranges of a, b, c, d, f, and g in the general formula (1-1), the description in the general formula (1) is cited.

D ¹ in the general formula (1-1) is a doping element that can particularly suitably improve the characteristics of the LNCW oxide of the present invention. e1 preferably satisfies 0.0001 ≦ e1 ≦ 0.2, more preferably satisfies 0.001 ≦ e1 ≦ 0.2, and satisfies 0.01 ≦ e1 ≦ 0.15. More preferred. In addition, e1 may be 0 or 0 <e1 ≦ 0.2.

D ² in the general formula (1-1) is a doping element capable of suitably improving the characteristics of the LNCW oxide of the present invention. The ^{D 2, Mn, Al, Mo} , Na, at least one element selected from P preferred.
Examples of the range of e2 in the general formula (1-1) include 0 <e2 ≦ 0.1, 0 <e2 ≦ 0.00.05, and 0 <e2 ≦ 0.01. In addition, e2 may be 0.

Next, a method for producing the LNCW oxide of the present invention will be described.

One embodiment of the method for producing an LNCW oxide of the present invention is:
Preparing a transition metal hydroxide containing nickel, cobalt and tungsten,
Heating the transition metal hydroxide to remove adhering water or a transition metal oxide;
A step of mixing the transition metal hydroxide from which the attached water has been removed or the transition metal oxide with a lithium salt and calcining the mixture.

A preferred embodiment of the method for producing an LNCW oxide of the present invention (hereinafter, also referred to as a “preferred production method of the present invention”) is described below.
a) preparing a transition metal hydroxide containing nickel, cobalt and tungsten;
b) heating the transition metal hydroxide to remove adhering water or to form a transition metal oxide;
c) a step of coating the transition metal hydroxide or the transition metal oxide from which adhering water has been removed with a metal compound to form a coated body;
d) mixing the coated body and a lithium salt and firing the mixture.

D ¹ in the general formula (1-1) is a metal mainly derived from the metal compound in step c).
D ² is an element derived from predominantly a) step and / or d) compounds that may be added in step.

In a preferred production method of the present invention, in step c), particles of a transition metal hydroxide or a transition metal oxide are coated with a metal compound, and in the subsequent step d), the metal compound in the coated portion is It is considered to be a barrier, preventing nickel inside the particles from migrating to lithium sites having a layered rock salt structure. That is, in the LNCW oxide manufactured by the preferable manufacturing method of the present invention, it is considered that the ratio of nickel correctly present in the transition metal site that should originally exist is higher than that of the conventional one.
As a result, the lithium ion secondary battery including the positive electrode including the preferred LNCW oxide of the present invention exhibits favorable battery characteristics.

Hereinafter, a preferred production method of the present invention will be described in order from step a). Unless otherwise specified, the pH defined in this specification refers to a value measured at 25 ° C.

First, the step a) will be described. Step a) is a step of preparing a transition metal hydroxide containing nickel, cobalt and tungsten.

The transition metal hydroxide containing nickel, cobalt and tungsten used in the step a) can be produced by mixing an aqueous solution containing nickel, cobalt and tungsten and a basic aqueous solution to precipitate the transition metal hydroxide. . The production process of the transition metal hydroxide will be described in detail.

The production process of the transition metal hydroxide,
Dissolving a nickel salt, a cobalt salt and a tungsten compound in water, and preparing a transition metal-containing aqueous solution containing nickel, cobalt and tungsten at a predetermined ratio,
A step of preparing a basic aqueous solution,
A transition metal hydroxide precipitation step of supplying the transition metal-containing aqueous solution to the basic aqueous solution to precipitate nickel, cobalt and tungsten as transition metal hydroxides.

Examples of the nickel salt include nickel sulfate, nickel carbonate, nickel nitrate, nickel acetate, and nickel chloride. Examples of the cobalt salt include cobalt sulfate, cobalt carbonate, cobalt nitrate, cobalt acetate, and cobalt chloride. Examples of the tungsten compound include tungstates such as Li ₂ WO ₄ , Na ₂ WO ₄ , K ₂ WO ₄ , and (NH ₄ ) ₂ WO ₄ .

ニ ッ ケ ル The mixing ratio of the nickel salt, the cobalt salt and the tungsten compound in the aqueous solution containing the transition metal may be adjusted so that the mixing ratio becomes a desired metal composition ratio of the LNCW oxide.

(4) The step of preparing the transition metal-containing aqueous solution is preferably performed in a reaction vessel equipped with a stirrer, and more preferably in a reaction vessel equipped with a device capable of introducing an inert gas such as nitrogen or argon. Further, a reaction tank provided with a device under constant temperature conditions is more preferable.

The transition metal-containing aqueous solution is preferably heated to a temperature in the range of preferably 40 to 90 ° C, more preferably 40 to 80 ° C.

ＰＨ The pH of the basic aqueous solution is preferably in the range of 9 to 14, more preferably in the range of 10 to 13, and still more preferably in the range of 10.5 to 12. As the basic compound that can be used, any compound that dissolves in water and exhibits basicity may be used. Examples thereof include ammonia, sodium hydroxide, potassium hydroxide, and alkali metal hydroxides such as lithium hydroxide, sodium carbonate, and carbonate. Alkali metal carbonates such as potassium and lithium carbonate; alkali metal phosphates such as trisodium phosphate, tripotassium phosphate and trilithium phosphate; and alkali metal acetates such as sodium acetate, potassium acetate and lithium acetate. Can be. The basic compound may be used alone or in combination of two or more. In the following steps, it is preferable that the pH of the aqueous solution is maintained in a suitable range, and therefore, the basic aqueous solution preferably contains at least a basic compound having a buffering ability. Examples of the basic compound having a buffering ability include ammonia, alkali metal carbonate, alkali metal phosphate, and alkali metal acetate.

The step of preparing the basic aqueous solution is preferably performed in a reaction vessel equipped with a stirrer, and more preferably in a reaction vessel equipped with a device capable of introducing an inert gas such as nitrogen or argon. Further, a reaction tank provided with a device under constant temperature conditions is more preferable.

(4) The basic aqueous solution is preferably heated to a temperature in the range of preferably 40 to 90 ° C, more preferably 40 to 80 ° C.

In the transition metal hydroxide precipitation step, by supplying the transition metal-containing aqueous solution to the basic aqueous solution, metal ions and hydroxide ions react, and nickel, cobalt and tungsten having low solubility in water. Is generated and precipitates. When tungstate is used, tungsten is precipitated as tungstic acid, O ₂ W (OH) ₂ , together with nickel hydroxide and cobalt hydroxide. Here, such precipitates are collectively referred to as transition metal hydroxides. The precipitated transition metal hydroxide particles form the basis of the primary particles of the LNCW oxide. Therefore, if the transition metal hydroxide precipitation step is performed under conditions where the transition metal hydroxide deposition rate is extremely high, that is, under conditions where transition metal hydroxide nuclei are generated everywhere, disordered transition metal hydroxides are formed. Particles may form, which may result in undesirable crystal habits of the primary particles of the LNCW oxide. Therefore, in the transition metal hydroxide precipitation step, it is preferable to precipitate particles of the transition metal hydroxide under as mild conditions as possible.

か ら In view of the above, the rate of supplying the transition metal-containing aqueous solution is preferably from 10 to 1000 mL / h, more preferably from 20 to 500 mL / h, and particularly preferably from 50 to 300 mL / h.

In the transition metal hydroxide precipitation step, the reaction solution is preferably maintained at a constant pH. Here, the pH value means the value itself obtained by measuring the reaction solution with a pH meter. The pH is preferably in the range of 9 to 14, more preferably in the range of 10 to 12, and particularly preferably in the range of 10.5 to 11. In order to maintain the reaction solution at a constant pH, it is preferable to prepare another basic aqueous solution and appropriately add it to the reaction solution in the transition metal hydroxide precipitation step.

The transition metal hydroxide precipitation step is preferably performed in a reaction vessel equipped with a stirrer, and more preferably in a reaction vessel equipped with a device capable of introducing an inert gas such as nitrogen or argon. Further, a reaction tank provided with a device under constant temperature conditions is more preferable.

In the transition metal hydroxide precipitation step, it is preferable that the amount of dissolved oxygen present in the reaction system is small. If the amount of dissolved oxygen present in the reaction system is large, an undesired oxidation reaction may occur, or a suitable crystallization of the transition metal hydroxide accompanying the precipitation of the transition metal hydroxide may be hindered.

In order to reduce the amount of dissolved oxygen present in the reaction system, the transition metal hydroxide precipitation step is performed under heating, while performing while introducing an inert gas into the reaction system, a deoxidizer, It is preferable to carry out the reaction in the presence of a reducing agent, an antioxidant and the like.

Examples of the heating range are 40 to 90 ° C. and 60 to 80 ° C.
Examples of the inert gas include nitrogen, argon, and helium.
Examples of the oxygen scavenger, reducing agent and antioxidant include ascorbic acid and its salts, glyoxylic acid and its salts, hydrazine, dimethylhydrazine, hydroquinone, dimethylamine borane, NaBH ₄ , NaBH ₃ CN, KBH ₄ , sulfurous acid and its salts Thiosulfuric acid and its salts, pyrosulfite and its salts, phosphorous acid and its salts, hypophosphorous acid and its salts.

後 に After the transition metal hydroxide precipitation step, the transition metal hydroxide is separated by filtration or the like. With the above method, a transition metal hydroxide can be obtained.

Incidentally, a) in the process, compounds containing an element of D ² in the general formula (1-1) is added, transition metal hydroxide containing D ² may be manufactured.

Next, the step b) will be described. The step b) is a step of heating a transition metal hydroxide containing nickel to remove adhered water or to form a transition metal oxide.
The heating temperature is preferably in the range of 100 to 800 ° C, more preferably in the range of 200 to 700 ° C, and particularly preferably in the range of 300 to 600 ° C. Step b) may be performed under normal pressure or under reduced pressure.

Next, the step c) will be described. The step c) is a step of coating a transition metal hydroxide or a transition metal oxide from which adhering water has been removed with a metal compound to obtain a coated body.
Hereinafter, a case where the “transition metal oxide” is coated with a metal compound will be described. In the case where the “transition metal hydroxide from which adhered water has been removed” is coated with a metal compound, in the following description, “transition metal oxide” is appropriately changed to “transition metal hydroxide from which adhered water has been removed”. Then, it should be read.

Specific examples of the metal compounds, the or hydroxide ^{D 1,} for _{example, ZrO 2, CaVO 3, MnO} 2, La 2 CuO 4, La 2 NiO 4, SnO 2, Tl 2 Mn 2 O 7, EuO, Fe ₂ O ₃ , CaMnO ₃ , SrMnO ₃ , (Sr, La) TiO ₃ , LaTiO ₃ , SrFeO ₃ , BaMoO ₃ , CaMoO ₃ , Ln ₂ Os ₂ O ₇ (Ln is an element selected from Y and rare earth elements) _{.), Tl 2 Ir 2 O} 7, Cd 2 Re 2 O 7, Lu 2 Ir 2 O 7, Bi 2 Rh 2 O 7, Bi 2 Ir 2 O 7, Ti 2 O 3, WO 2, VO, V 2 _{O 3, LaMnO 3, CaCrO 3} , LaCoO 3, (ZnO) 5, SrCrO 3, In 0.97 Y 0.03 O 3, Zn x Al y O (x + y = 1 _{, LiV 2 O 4, Na 1} -x CoO 2 (0 <x <1), LiTi 2 O 4, SrMoO 3, BaPbO 3, Tl 2 Os 2 O 7, Pb 2 Os 2 O 7, Pb 2 Ir 2 O _{7, Lu 2 Ru 2 O 7} , Bi 2 Ru 2 O 7, SrRuO 3, CaRuO 3, CrO 2, MoO 2, ReO 2, TiO, LaO, SmO, LaNiO 3, SrVO 3, ReO 3, IrO 2, RuO _{2, RhO 2, OsO 2,} NdO, NbO, La 2 O 3, NiO, LaSr x Co y O 3 (x + y = 1), NaCoO 3, NaNiO 3, LiCoO 3, metal oxide selected from LiNiO ₃ or Metal hydroxides of these precursors can be exemplified.
Among the metal compounds, the metal oxide preferably has a crystal structure such as a perovskite type.

In order to coat the transition metal oxide with the metal compound, a method in which a precursor of each metal compound or an aqueous solution in which each metal is dissolved is sprayed on the transition metal oxide, and / or simultaneously, may be dried. . Further, the transition metal oxide is immersed in an aqueous solution in which the precursor of each metal compound or each metal is dissolved, and the precursor of each metal compound or the hydroxide of each metal is attached to the surface of the transition metal oxide. Then, a method of heating and drying may be adopted. In particular, a dispersion of the transition metal oxide, a precursor of each metal compound and an aqueous solution in which each metal is dissolved are mixed, and a hydroxide of each metal is precipitated on the surface of the transition metal oxide, and then dried. (Hereinafter, sometimes referred to as “precipitation method”).

Hereinafter, D ¹ is the preferred precipitation method when the Zr, will be described in detail. The precipitation method includes the following steps c-1), c-2) and c-3). If D ¹ is a metal other than Zr are, c-1) step, c-2) step and c-3) zirconium may be read as to the metal in the process. When D ¹ is a plurality of metals, an aqueous solution containing a plurality of metals may be used in step c-2), or the metal species of the aqueous metal solution may be changed while the step c-1) is performed. The steps c-2) and c-3) may be repeated.

c-1) a dispersion liquid preparing step of dispersing the transition metal oxide in water,
c-2) a zirconium precipitation step of mixing the zirconium aqueous solution containing the hetero element-containing organic compound and the dispersion to precipitate zirconium hydroxide on the surface of the transition metal oxide;
c-3) A step of drying a transition metal oxide having zirconium hydroxide deposited on the surface to form a coated body

It is preferable to pulverize the transition metal oxide before the step (c-1). Further, it is preferable to adjust the pH so that the pH of the dispersion is in the range of about 9 to 12.

Next, the step c-2) will be described.
A zirconium aqueous solution containing a hetero element-containing organic compound is produced by dissolving a zirconium salt and a hetero element-containing organic compound in water. The aqueous zirconium solution containing the hetero element-containing organic compound is usually an acidic solution. The mixing ratio of zirconium and the hetero element-containing organic compound in the zirconium salt is preferably in a molar ratio of zirconium: hetero element-containing organic compound = 1: 1 to 1: 3.

Examples of the zirconium salt include zirconium oxide, zirconium hydroxide, zirconium sulfate, zirconium nitrate, zirconium phosphate, and zirconium halide.

ヘ テ ロ The hetero element in the hetero element-containing organic compound means N, O, P or S. Examples of the hetero element-containing organic compound include an amino group, an amide group, an imide group, an imino group, a cyano group, an azo group, a hydroxyl group, an alkoxy group, a carboxyl group, an ester group, an ether group, a carbonyl group, which can be coordinated with a metal ion. Phosphate group, phosphate group, phosphonate group, phosphonate group, phosphinate group, phosphinate group, phosphenate group, phosphenate group, phosphite group, phosphenite group, thiol group, Organic compounds having a sulfide group, a sulfinyl group, a sulfonyl group, a sulfonic acid group, a thiocarboxyl group, a thioester group, or a thiocarbonyl group can be given.

Particularly, as the hetero element-containing organic compound, a chelate compound having a plurality of the above groups and capable of coordinating to a metal ion at a plurality of positions is preferable.

Specific examples of chelating compounds include polyamine compounds such as ethylenediamine, diethylenetriamine, glycine, alanine, cysteine, glutamine, arginine, asparagine, aspartic acid, serine, amino acids such as ethylenediaminetetraacetic acid, malonic acid, succinic acid, glutaric acid, and maleic acid. Examples thereof include acids, dicarboxylic acids such as phthalic acid, and hydroxycarboxylic acids.

As the chelate compound, hydroxycarboxylic acid is particularly preferred. Examples of the hydroxycarboxylic acid having a hydroxyl group and a carboxyl group in a molecule include an aliphatic hydroxycarboxylic acid and an aromatic hydroxycarboxylic acid.

Aliphatic hydroxycarboxylic acids include glycolic acid, lactic acid, tartronic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, malic acid, tartaric acid, citramalic acid, citric acid, isocitric acid, leucic acid , Mevalonic acid, pantoic acid, quinic acid and shikimic acid.

Examples of the aromatic hydroxycarboxylic acid include o-hydroxybenzoic acid derivatives such as salicylic acid, gentisic acid and orseric acid, mandelic acid, benzylic acid and 2-hydroxy-2-phenylpropionic acid.

Any of the above specific hydroxycarboxylic acids can form a conformation in which an OH group and a CO ₂ H group can coordinate to the same zirconium ion.

In step c-2), it is preferable to control the pH of the mixed solution in step c-2) in order to deposit zirconium efficiently. Here, it is assumed that zirconium hydroxide having low solubility is precipitated on the surface of the transition metal oxide by setting the pH of the mixed solution to the alkali side. For example, it is preferable to add a basic aqueous solution so that the pH of the solution in step c-2) is in the range of 9 to 13. As the basic aqueous solution, those described in the step a) may be employed.

The transition metal oxide that has passed through the step c-2) is separated by a method such as filtration and supplied to the step c-3).

The drying in the step c-3) is preferably performed under heating and / or under reduced pressure. Examples of the heating temperature are in the range of 100 to 500 ° C and 200 to 400 ° C.
The main purpose of the drying in the step c-3) is to remove water adhering to the transition metal oxide having zirconium hydroxide precipitated on the surface. However, by increasing the heating temperature, zirconium hydroxide present on the surface of the transition metal oxide may be dehydrated and changed to zirconium oxide. That is, the coated body may be a transition metal oxide coated with zirconium hydroxide or a transition metal oxide coated with zirconium oxide.

Next, the step d) will be described. Step d) is a step in which the coated body and the lithium salt are mixed and fired.

Examples of the lithium salt include lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, lithium oxalate, and lithium halide. The amount of the lithium salt may be appropriately determined so that the LNCW oxide has a desired lithium composition.

Examples of the mixing device include a mortar and pestle, a stirring mixer, a V-type mixer, a W-type mixer, a ribbon-type mixer, a drum mixer, and a ball mill.

In the d) step, the compound and containing an element of D ² in the general formula (1-1), F compounds may be mixed. In particular, a compound selected from a Na compound, an F compound and a P compound is preferably mixed. Due to the presence of D ^2, the improvement of rate characteristics and / or the capacity retention rate of the lithium ion secondary battery having a LNCW oxide of the present invention can be expected.

The Na _compounds, exemplified _{NaF, NaCl, NaBr, NaI,} and sodium salts, such as _{Na 3 PO 4, Na 2 HPO} 4, NaH 2 PO 4, Na 2 SO 4, NaHSO 4, NaNO 3, CH 3 CO 2 Na it can.
Examples of the F compound include metal fluorides such as LiF, NaF, KF, MgF ₂ , CaF ₂ , BaF ₂ , and AlF ₃ .
Examples of the P compound include H ₃ PO ₄ , LiH ₂ PO ₄ , Li ₂ HPO ₄ , Li ₃ PO ₄ , NaH ₂ PO ₄ , Na ₂ HPO ₄ , Na ₃ PO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ , phosphoric acid and phosphates such K ₃ PO ₄ can be exemplified.

The firing may be performed in an air atmosphere or an oxygen gas atmosphere, or may be performed in the presence of an inert gas such as helium or argon. The heating temperature in the firing step can be, for example, in the range of 400 to 1200 ° C. The heating time in the firing step can be, for example, 1 to 50 hours.

The baking in the step d) may be performed under a single temperature condition, or may be performed by combining a plurality of baking processes having different temperature conditions, or may be performed by setting a specific temperature raising program. May be.

As a method of combining a plurality of firing steps having different temperature conditions, a first firing step in which the mixture of the coated body and the lithium salt is heated at 400 to 800 ° C. to form a first fired body; A second firing step of heating at 550 to 1000 ° C. can be mentioned. By combining a plurality of firing steps, an LNCW oxide that can be a more suitable active material can be manufactured.

温度 Examples of the temperature of the first baking step include a range of 400 to 800 ° C. and 650 to 750 ° C. Examples of the heating time in the first firing step include a range of 3 to 30 hours, 5 to 20 hours, and 5 to 15 hours.

The second firing step is a step of heating the first fired body at 550 to 1000 ° C.
Here, from the viewpoint of LNCW oxide crystal formation, heating at as low a temperature as possible facilitates generation of crystals having a uniform composition and a uniform shape. Therefore, the temperature of the second firing step may be in the range of 550 to 950 ° C., 550 to 900 ° C., 550 to 850 ° C., and 550 to 800 ° C.

加熱 Examples of the heating time in the second baking step include a range of 3 to 30 hours, 5 to 20 hours, and 5 to 15 hours.

In the preferred production method of the present invention, in step c), the transition metal oxide particles are coated with the metal compound, so that the coated metal compound becomes a barrier in the first and second firing steps, It is considered that nickel is restrained from migrating to lithium sites having a layered rock salt structure.

It is preferable that the LNCW oxide obtained in the step d) has a certain particle size distribution through a pulverizing step and a classification step. As the range of the particle size distribution, the average particle size (D ₅₀ ) is preferably 50 μm or less, more preferably 1 μm or more and 30 μm or less, still more preferably 1 μm or more and 20 μm or less in a measurement with a general laser scattering diffraction type particle size distribution meter. And 2 μm or more and 10 μm or less are particularly preferable.

Another preferred embodiment of the method for producing an LNCW oxide of the present invention (hereinafter, also referred to as a “second production method”) is as follows.
a′-1) preparing a transition metal hydroxide containing nickel and cobalt;
a′-2) a step of adding an aqueous solution of tungstate to a basic suspension containing a transition metal hydroxide,
a′-3) a step of lowering the pH of the suspension after the addition of the aqueous solution of tungstate to precipitate tungstic acid on the surface of the transition metal hydroxide to form a coated body;
b ′) heating the coated body to remove adhering water or to form a transition metal oxide;
d ′) a step of mixing the transition metal hydroxide or the transition metal oxide from which the adhering water has been removed with a lithium salt and firing the mixture.
The technical items that specify each step include the a) step or c) step described above for the a′-1) to a′-3) steps, and the b) step described above for the b ′) step. Regarding the step d ′), the technical content of the step d) described above is appropriately and appropriately used.

Further, another preferred aspect of the method for producing an LNCW oxide of the present invention (hereinafter, may be referred to as “third production method”) is as follows.
a '') providing a transition metal hydroxide comprising nickel and cobalt;
b '') heating the transition metal hydroxide to remove adhering water or to form a transition metal oxide;
c '') To the transition metal hydroxide or the suspension containing the transition metal oxide from which the adhering water has been removed, an aqueous solution of tungstate is added to convert the transition metal hydroxide or the transition metal oxide into tungsten. Coating with an acid to form a coated body,
d '') mixing the coated body and a lithium salt and firing the mixture.
In addition, the technical items specifying each step include the a) step described above for the a ″) step, the b) step described above for the b ″) step, and the previously described b) step for the c ″) step. For the step c), the steps a′-2), a′-3), and d ″), the technical contents of the step d) described above are appropriately and appropriately used.

In the second manufacturing method, tungsten is added in the step a'-2) and integrated with the transition metal hydroxide containing nickel and cobalt in the step a'-3). In the third manufacturing method, tungsten is integrated with a transition metal hydroxide containing nickel and cobalt in step c ″).

Here, when a transition metal hydroxide containing nickel, cobalt and tungsten is produced at a time by coprecipitation, a tungstate composed of hexavalent tungsten is used as a nickel hydroxide. May be partially oxidized to form nickel oxyhydroxide. As a result, it is assumed that the crystal growth of the transition metal hydroxide is hindered.
On the other hand, when a transition metal hydroxide is produced without adding tungsten, as in the second production method and the third production method, in the a′-1) step and the a ″) step where tungsten is not added, It is considered that the crystal growth of the transition metal hydroxide containing nickel and cobalt proceeds smoothly because there is no inhibition of the crystal growth as described above.

Since the size of the crystal of the transition metal hydroxide as an intermediate is considered to be the basis of the size of the primary particles of the LNCW oxide of the present invention, it is produced by the second production method and the third production method. It can be said that the LNCW oxide of the present invention contains relatively large primary particles. And, the LNCW oxide of the present invention containing large primary particles is expected to have low resistance.

The size of the primary particles of the LNCW oxide is preferably in the range of 50 nm to 1000 nm, more preferably in the range of 100 nm to 500 nm, and even more preferably in the range of 150 nm to 500 nm by microscopic observation. The primary particles mean particles that are recognized as one particle during SEM observation.

In the LNCW oxide of the present invention, among the peaks observed in the powder X-ray diffraction measurement using Cu-κα, the peak intensity (lamellar intensity) derived from the lamellar structure observed at 2θ = 17 to 20 ° is obtained. The relationship between the peak intensity (rock salt strength) derived from the rock salt structure observed at 2θ = 42 to 46 ° preferably satisfies (layer strength) / (rock salt strength) ≧ 0.5, and (layer strength) ) / (Rock salt strength) ≧ 0.6, more preferably (layer strength) / (rock salt strength) ≧ 0.7, more preferably (layer strength) / (rock salt strength) ≧ 0 .9, and more preferably (layer strength) / (rock salt strength) ≧ 1. As the upper limit of (layer strength) / (rock salt strength), 4, 3, and 2 can be exemplified.

Ｌ The LNCW oxide of the present invention can be used as an active material of a lithium ion secondary battery. The lithium ion secondary battery of the present invention includes the LNCW oxide of the present invention as an active material. Specifically, the lithium ion secondary battery of the present invention includes a positive electrode including the LNCW oxide of the present invention as a positive electrode active material, a negative electrode, and a solid electrolyte, or includes the LNCW oxide of the present invention as a positive electrode active material. A positive electrode, a negative electrode, an electrolytic solution, and a separator provided as materials are provided.

The positive electrode has a current collector and a positive electrode active material layer bound to the surface of the current collector.

(4) The current collector refers to a chemically inert electronic conductor that keeps current flowing through the electrodes during discharging or charging of the lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel A metal material can be exemplified. The current collector may be covered with a known protective layer. A current collector whose surface is treated by a known method may be used as the current collector.

The current collector can be in the form of a foil, a sheet, a film, a line, a bar, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of a foil, sheet, or film, the thickness is preferably in the range of 1 μm to 100 μm.

The positive electrode active material layer contains a positive electrode active material and, if necessary, a conductive auxiliary and / or a binder.

As the positive electrode active material, any material containing the LNCW oxide of the present invention may be used, and only the LNCW oxide of the present invention may be employed, or a combination of the LNCW oxide of the present invention and a known positive electrode active material may be used. May be.

Examples of the known positive electrode active material include a spinel structure compound such as LiMn ₂ O ₄ , and a general formula: LiM _h PO ₄ (M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, and Ba). , At least one element selected from Ti, Al, Si, B, Te and Mo, an olivine structure compound represented by 0 <h <2), LiMVO ₄ or Li ₂ MSiO ₄ (where M is Co, Ni , Mn, or Fe), a polyanionic compound represented by LiMPO ₄ F (M is a transition metal), a tabolite compound represented by LiMPO ₃ (M is a transition metal). Borate compounds, Li ₂ MnO _{3 and the} like.

The conductive additive is added to increase the conductivity of the electrode. Therefore, the conductive assistant may be arbitrarily added when the conductivity of the electrode is insufficient, and may not be added when the conductivity of the electrode is sufficiently excellent. The conductive additive may be any chemically inert high electron conductor, and examples thereof include carbon black, graphite, vapor grown carbon fiber (Vapor Grown Carbon Fiber), and various metal particles. You. Examples of the carbon black include acetylene black, Ketjen Black (registered trademark), furnace black, and channel black. These conductive aids can be used alone or in combination of two or more.

The compounding ratio of the conductive additive in the active material layer is preferably from 1: 0.005 to 1: 0.5, and preferably from 1: 0.01 to 1: 0, by mass ratio. .2, more preferably 1: 0.03 to 1: 0.1. If the amount of the conductive auxiliary agent is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary agent is too large, the moldability of the active material layer deteriorates and the energy density of the electrode decreases.

The binder plays a role of anchoring the active material and the conductive assistant to the surface of the current collector and maintaining the conductive network in the electrode. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber; thermoplastic resins such as polypropylene and polyethylene; imide-based resins such as polyimide and polyamideimide; resins containing alkoxysilyl groups; Examples include acrylic resins such as (meth) acrylic acid, styrene-butadiene rubber (SBR), and carboxymethyl cellulose. These binders may be used alone or in combination.

The mixing ratio of the binder in the active material layer is preferably 1: 0.001 to 1: 0.3, and 1: 0.005 to 1: 0, in terms of mass ratio. .2, more preferably 1: 0.01 to 1: 0.15. This is because if the amount of the binder is too small, the moldability of the electrode decreases, and if the amount of the binder is too large, the energy density of the electrode decreases.

The negative electrode has a current collector and a negative electrode active material layer bound to the surface of the current collector. As the current collector, those described for the positive electrode may be appropriately employed. The negative electrode active material layer contains a negative electrode active material and, if necessary, a conductive auxiliary and / or a binder.

As the negative electrode active material, a known material may be employed, and examples thereof include a carbon-based material capable of inserting and extracting lithium, an element capable of being alloyed with lithium, and a compound having an element capable of being alloyed with lithium. .

Examples of the carbon-based material include non-graphitizable carbon, graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon and carbon blacks. Here, the organic polymer compound fired body is obtained by firing a polymer material such as phenols and furans at an appropriate temperature and carbonizing the polymer material.

Specific examples of elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, and Si. , Ge, Sn, Pb, Sb, and Bi can be exemplified, and Si or Sn is particularly preferable.

Specific examples of the compound having an element that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO, and in particular, SiO _x (0.3 ≦ x ≦ 1.6, or 0.5 ≦ x ≦ 1.5) Is preferred.

Above all, the negative electrode active material preferably contains a Si-based material having Si. The Si-based material is preferably made of silicon or / and a silicon compound capable of occluding and releasing lithium ions, and is preferably, for example, SiO _x (0.5 ≦ x ≦ 1.5). Although silicon has a large theoretical charge / discharge capacity, silicon has a large volume change during charge / discharge. Therefore, the volume change of silicon can be reduced by using SiO _x containing silicon as the negative electrode active material.

As the negative electrode active material, a Si material obtained by heating a layered polysilane obtained by treating CaSi ₂ with an acid such as hydrochloric acid or hydrofluoric acid at 300 to 1000 ° C. may be employed. Further, the Si material may be heated together with a carbon source, and a carbon-coated Si material may be used as the negative electrode active material.

一種 As the negative electrode active material, one or more of the above can be used.

導電 As for the conductive auxiliary agent and the binder used for the negative electrode, those described for the positive electrode may be appropriately and appropriately employed in the same mixing ratio.

In order to form an active material layer on the surface of the current collector, the current is collected using a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, and a curtain coating method. The active material may be applied to the surface of the body. Specifically, a slurry is prepared by mixing an active material, a solvent, and, if necessary, a binder and / or a conductive assistant. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The slurry is applied to the surface of the current collector and then dried. The dried product may be compressed to increase the electrode density.

も の As the solid electrolyte, a solid electrolyte that can be used as a solid electrolyte of a lithium ion secondary battery may be appropriately adopted.

The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.

環状 As the non-aqueous solvent, cyclic carbonate, cyclic ester, chain carbonate, chain ester, ethers and the like can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and examples of the cyclic ester include gamma-butyrolactone, 2-methyl-gamma-butyrolactone, acetyl-gamma-butyrolactone, and gamma-valerolactone. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethyl methyl carbonate, and examples of the chain ester include alkyl propionate, dialkyl malonate, and alkyl acetate. Examples of the ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which part or all of the hydrogen in the chemical structure of the above specific solvent is replaced by fluorine may be used.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , and LiN (CF ₃ SO ₂ ) ₂ .

Examples of the electrolyte include a solution in which a lithium salt is dissolved in a nonaqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate at a concentration of about 0.5 mol / L to 1.7 mol / L.

The separator separates the positive electrode and the negative electrode, and prevents lithium ions from passing through while preventing a short circuit due to contact between the two electrodes. Examples of the separator include synthetic resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid, polyester, and polyacrylonitrile; polysaccharides such as cellulose and amylose; and natural resins such as fibroin, keratin, lignin, and suberin. Examples thereof include a porous body, a nonwoven fabric, and a woven fabric using one or a plurality of electric insulating materials such as polymers and ceramics. Further, the separator may have a multilayer structure.

Next, an example of a method for manufacturing a lithium ion secondary battery will be described.

セ パ レ ー タ A separator is interposed between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be any of a stacked type in which a positive electrode, a separator, and a negative electrode are stacked, or a wound type in which a positive electrode, a separator, and a negative electrode are wound. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collecting lead or the like, an electrolytic solution is added to the electrode body and lithium ion secondary Use a battery. In addition, the lithium ion secondary battery of the present invention may be charged and discharged in a voltage range suitable for the type of active material included in the electrode.

形状 The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical type, a square type, a coin type, and a laminate type can be adopted.

リ チ ウ ム The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be any vehicle that uses electric energy from a lithium ion secondary battery for all or part of its power source, such as an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with a lithium ion secondary battery include various home electric appliances, office equipment, industrial equipment, and the like, other than vehicles, such as personal computers and portable communication devices, which are driven by batteries. Furthermore, the lithium ion secondary battery of the present invention can be used as a wind power photovoltaic power generator, a hydroelectric power generator, a power storage device and a power smoothing device for a power system, a power supply source for motive power of ships and the like, and / or auxiliary equipment, an aircraft, a space. Power supply for motive power of ships and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, electric power It may be used for a power storage device that temporarily stores power required for charging at a vehicle charging station or the like.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The present invention can be implemented in various forms with modifications, improvements, and the like that can be made by those skilled in the art without departing from the gist of the present invention.

実 施 Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. Note that the present invention is not limited by these examples.

(Example 1)
The LNCW oxide of Example 1 was manufactured as follows.

a) Step 80 g of nickel sulfate hexahydrate, 11 g of cobalt sulfate heptahydrate, and 5 g of sodium tungstate dihydrate were dissolved in 400 mL of pure water to prepare a transition metal-containing aqueous solution. . The molar ratio of nickel, cobalt, and tungsten in the transition metal-containing aqueous solution is 85: 11: 4.

30 g of 25% aqueous ammonia was mixed with pure water to prepare 400 mL of a first basic aqueous solution.

ナ ト リ ウ ム Sodium hydroxide, ammonia water and pure water were mixed to prepare a second basic aqueous solution having a pH of 10.75.

In a constant temperature bath maintained at 80 ° C., a transition metal-containing aqueous solution was supplied to the second basic aqueous solution under nitrogen gas introduction and stirring conditions to precipitate nickel, cobalt and tungsten as transition metal hydroxides. . At this time, in order to maintain the pH of the reaction solution in the range of 10.75 to 10.80, a first basic aqueous solution and a 48 wt% aqueous sodium hydroxide solution were appropriately added dropwise. Here, the pH value means the value itself obtained by measuring the reaction solution with a pH meter.

The transition metal hydroxide was separated by filtration. The transition metal hydroxide was washed with pure water using an ultrasonic cleaner, and then the transition metal hydroxide was isolated by filtration.

b) Step In the atmosphere, the transition metal hydroxide was heated at 300 ° C. for 5 hours to obtain a transition metal oxide.

c) Step A transition metal oxide dispersion was prepared by adding the transition metal oxide to pure water.

0.3 g of zirconium sulfate and 0.17 g of glycolic acid as hydroxycarboxylic acid were dissolved in water to prepare an aqueous solution of zirconium containing hydroxycarboxylic acid. In the aqueous solution of zirconium containing hydroxycarboxylic acid, the molar ratio of zirconium to glycolic acid was 1: 2.

(4) The dispersion of the transition metal oxide and the aqueous solution of zirconium containing hydroxycarboxylic acid were mixed to form a mixed solution. Then, a sodium hydroxide solution was added over 1 hour until the pH of the mixed solution reached 12.5, to obtain a coated body in which zirconium hydroxide was deposited on the surface of the transition metal oxide. After the coated body was separated by filtration, it was dried.

d) Step 10 g of the dried coated body, 2.12 g of lithium hydroxide anhydride, 0.13 g of Na ₃ PO ₄ , and 0.023 g of LiF were mixed in a mortar to form a mixture. Then, the mixture was heated at 650 ° C. for 5 hours in an air atmosphere to obtain a first fired body.

The first fired body was crushed in a mortar to obtain a powder. The powdery first fired body was heated at 750 ° C. for 15 hours in an oxygen gas atmosphere to obtain an LNCW oxide. The LNCW oxide was crushed in a mortar to obtain the LNCW oxide of Example 1.
The composition of the theoretical LNCW oxide of Example 1 _{is Li 1 Ni 0.85 Co 0.11 W 0.04} Zr 0.0025 Na 0.01 P 0.01 O 2 F 0.01.

リ チ ウ ム A lithium ion secondary battery of Example 1 was manufactured as follows.

ア ル ミ ニ ウ ム A 20 μm-thick aluminum foil was prepared as a positive electrode current collector. 94 parts by mass of the LNCW oxide of Example 1 as a positive electrode active material, 3 parts by mass of acetylene black as a conductive additive, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed. This mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone to prepare a slurry. The slurry was placed on the surface of the aluminum foil, and the slurry was applied using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone by volatilization, thereby forming a positive electrode active material layer on the surface of the aluminum foil. The aluminum foil having the positive electrode active material layer formed on the surface was compressed using a roll press, and the aluminum foil and the positive electrode active material layer were firmly adhered and joined to form a bonded article. The joined article was heated at 120 ° C. for 6 hours using a vacuum dryer, cut into a predetermined shape, and used as a positive electrode.

The negative electrode was manufactured as follows.
98.3 parts by mass of graphite, 1 part by mass of styrene-butadiene rubber as a binder and 0.7 parts by mass of carboxymethylcellulose were mixed, and the mixture was dispersed in an appropriate amount of ion-exchanged water to produce a slurry. The slurry was applied to a 20 μm-thick copper foil serving as a negative electrode current collector using a doctor blade so as to form a film. The current collector coated with the slurry was dried and then pressed to obtain a bonded article. The bonded article was heated at 120 ° C. for 6 hours using a vacuum dryer, cut into a predetermined shape, and used as a negative electrode.

Using the above positive electrode and negative electrode, a laminate type lithium ion secondary battery was manufactured. Specifically, a 25 μm-thick rectangular sheet made of a resin film having a three-layer structure of polypropylene / polyethylene / polypropylene was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. This electrode group was covered with a set of two laminated films, three sides were sealed, and then an electrolyte was injected into the bag-shaped laminated film. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent obtained by mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate at a volume ratio of 3: 3: 4 was used. Thereafter, by sealing the remaining one side, the four sides were hermetically sealed, and the laminated lithium ion secondary battery of Example 1 in which the electrode plate group and the electrolyte were sealed was obtained. Note that the positive electrode and the negative electrode have tabs that can be electrically connected to the outside, and some of these tabs extend outside the laminated lithium ion secondary battery.
Through the above steps, the lithium ion secondary battery of Example 1 was manufactured.

(Example 2)
In the step a), the LNCW oxide and the lithium ion secondary battery of Example 2 were manufactured in the same manner as in Example 1, except that ascorbic acid was added to the aqueous solution containing a transition metal.
The transition metal-containing aqueous solution used in Example 2 was a solution having a concentration of ascorbic acid of 7.5 g / L. In the solution, W and ascorbic acid are present in equimolar amounts.

(Example 3)
c) The LNCW oxide and lithium ion secondary battery of Example 3 were manufactured in the same manner as in Example 1, except that the step was not performed.

(Comparative Example 1)
A lithium ion secondary battery of Comparative Example 1 was manufactured in the same manner as in Example 1 except that LiNi _0.85 Co _0.11 Al _0.04 O ₂ was used as the positive electrode active material.

(Evaluation Example 1)
The surface of the LNCW oxide of Example 1 was observed with a scanning electron microscope (SEM). FIG. 1 shows an SEM image of the LNCW oxide of Example 1.
According to the measurement with the SEM image, the primary particle diameter of the LNCW oxide of Example 1 was about 50 nm, and the secondary particle diameter was about 4 μm.

When the secondary particles of the LNCW oxide of Example 1 were analyzed by SEM-EDX in which the scanning electron microscope was combined with energy dispersive X-ray spectroscopy, nickel, cobalt and tungsten were uniformly distributed. Was confirmed.

(Evaluation example 2)
The crystal structures of the LNCW oxides of Examples 1, 2 and 3 were analyzed with a powder X-ray diffractometer using Cu-κα.
It was confirmed that all the LNCW oxides showed a diffraction pattern of a layered rock salt structure.

Regarding the relationship between the peak intensity derived from the layered structure observed at 2θ = 17 to 20 ° (layered intensity) and the peak intensity derived from the rock salt structure observed at 2θ = 42 to 46 ° (rock salt intensity), It is shown in Table 1.

(Evaluation example 3)
With respect to the lithium ion secondary batteries of Example 1 and Comparative Example 1, a charge / discharge cycle of charging to 4.4 V and discharging to 2.5 V at a rate of 0.1 C was repeated.
Table 2 shows the discharge capacity per unit volume of the positive electrode active material in the initial charge / discharge cycle and the discharge capacity retention rate at the time when the charge / discharge cycle was repeated 12 times. The discharge capacity retention ratio is a ratio to the initial discharge capacity.

わ か る It can be seen that the lithium ion secondary battery of Example 1 is superior to the lithium ion secondary battery of Comparative Example 1 in both parameters of the initial discharge capacity and the discharge capacity retention rate.

(Evaluation example 4)
For the lithium ion secondary batteries of Examples 1 and 3, the first charge / discharge of charging to 4.0 V and discharging to 2.5 V at a 0.03 C rate was performed, and the battery was charged to 4.2 V. A second charge / discharge of discharging the battery to 2.5 V was performed, and a third charging / discharging of charging the battery to 4.3 V and discharging the battery to 2.5 V was performed.
FIG. 2 shows a charge / discharge curve of the lithium ion secondary battery of Example 1, and FIG. 3 shows a charge / discharge curve of the lithium ion secondary battery of Example 3.

2 and 3 that the capacity of the lithium ion secondary battery of Example 1 is larger than the capacity of the lithium ion secondary battery of Example 3 in both charging and discharging.
It can be said that the LNCW oxide of Example 1 to which Zr was added was more preferable than the LNCW oxide of Example 3 to which Zr was not added.

(Example 4)
a) The molar ratio of nickel, cobalt, and tungsten in the aqueous solution containing the transition metal in the step was 92: 4: 4, the step c) was not performed, and the firing temperature and the firing time in the step d) slightly changed. Except having made it, the LNCW oxide of Example 4 and the lithium ion secondary battery of Example 4 were manufactured by the method similar to Example 1.

(Example 5)
a) The molar ratio of nickel, cobalt, and tungsten in the aqueous solution containing the transition metal in the step was 95: 3: 2, the step c) was not performed, and the firing temperature and the firing time in the step d) slightly changed. Except having made it, the LNCW oxide of Example 5 and the lithium ion secondary battery of Example 5 were manufactured by the method similar to Example 1.

(Example 6)
a) The molar ratio of nickel, cobalt, and tungsten in the aqueous solution containing the transition metal in the step was 95: 4: 1, the step c) was not performed, and the firing temperature and the firing time in the step d) slightly changed. Except having made it, the LNCW oxide of Example 6 and the lithium ion secondary battery of Example 6 were manufactured by the method similar to Example 1.

(Example 7)
a) the molar ratio of nickel, cobalt, and tungsten in the aqueous solution containing the transition metal in step a) was 95.5: 4: 0.5; c) step was not performed; and b) the firing temperature and firing in step d). An LNCW oxide and a lithium ion secondary battery of Example 7 were produced in the same manner as in Example 1, except that the time was slightly changed.

(Evaluation example 5)
With respect to the lithium ion secondary batteries of Examples 4 to 7 and Comparative Example 1, a charge / discharge cycle of charging to 4.4 V and discharging to 2.5 V at a 0.1 C rate was repeated. Evaluation example 5 was performed on a different date and time from evaluation example 3.
Table 3 shows the charge capacity and the discharge capacity per unit volume of the positive electrode active material in the first charge / discharge cycle, together with the composition ratio of nickel, cobalt, and tungsten in the LNCW oxide.

結果 From the results in Table 3, it can be said that the capacity of the LNCW oxide having a high nickel ratio and a low tungsten ratio is high.

Claims (7)

1. A lithium nickel cobalt tungsten oxide having a layered rock salt structure, which is represented by the following general formula (1).
   Formula _{(1) Li a Ni b Co} c W d D e O f F g
   In the general formula (1), a, b, c, d, e, f, and g are 0.5 ≦ a ≦ 2, 0.5 ≦ b ≦ 0.97, 0 <c <0.5, 0 < d <0.5, 0 ≦ e ≦ 0.2, b + c + d + e = 1, 1.8 ≦ f ≦ 2.2, and 0 ≦ g ≦ 0.2. D is a doping element.
2. The lithium nickel cobalt tungsten oxide having a layered rock salt structure according to claim 1, wherein the general formula (1) is the following general formula (1-1).
   Formula _{(1-1) Li a Ni b Co} c W d D 1 e1 D 2 e2 O f F g
   In the general formula (1-1), a, b, c, d, e1, e2, f, and g are 0.5 ≦ a ≦ 2, 0.5 ≦ b ≦ 0.97, and 0 <c <0. 5, 0 <d <0.5, 0 ≦ e1 ≦ 0.2, 0 ≦ e2 <0.2, 0 <e1 + e2 ≦ 0.2, b + c + d + e1 + e2 = 1, 1.8 ≦ f ≦ 2.2, 0 ≦ g ≦ 0.2 is satisfied.
   D ¹ is Zr, Ca, V, Mn, Cu, Ni, Sn, Tl, Fe, Sr, Ti, Ba, Mo, Y, a rare earth element, Os, Ir, Cd, Re, Bi, Rh, W, Cr, At least one element selected from Co, Zn, In, Al, Li, Na, Pb, Ru, and Nb.
   D ² is an element other than ^{Li, Ni, Co, W,} D 1, O, F.
3. D ² is Mn, Al, Mo, Na, lithium-nickel-cobalt tungsten oxide of layered rock salt structure according to claim 2, wherein at least one element selected from P.
4. The lithium nickel cobalt tungsten oxide having a layered rock salt structure according to claim 2 or 3, wherein D ² contains Na and P, and g satisfies 0 <g ≦ 0.2.
5. In the powder X-ray diffraction measurement using Cu-κα, the peak intensity (layer intensity) derived from the layer structure observed at 2θ = 17 to 20 ° and the rock salt structure observed at 2θ = 42 to 46 ° The lithium nickel cobalt having a layered rock salt structure according to any one of claims 1 to 4, wherein the relationship of the peak intensity (rock salt strength) derived from the composition satisfies (layer strength) / (rock salt strength) ≧ 0.5. Tungsten oxide.
6. A positive electrode containing the lithium nickel cobalt tungsten oxide having a layered rock salt structure according to any one of claims 1 to 5.
7. A lithium ion secondary battery comprising the positive electrode according to claim 6.

Images