JP2022157526A - Composite materials for battery electrodes, electrodes for lithium ion batteries and lithium ion batteries - Google Patents

Abstract

To provide a lithium ion battery superior in charge/discharge characteristic, a composite material for a battery electrode which can offer such a lithium ion battery, and an electrode for a lithium ion battery.SOLUTION: A composite material for a battery electrode according to the present invention comprises: a matrix phase which contains a solid electrolyte containing Li, P and S atoms, and a compound containing Li and F atoms; and dispersal phases dispersed and included in the matrix phase, and containing a composite oxide including at least one kind of atoms selected from a group consisting of Li atoms, Co atoms, Ni atoms and Mn atoms, and O atoms.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a composite material for a battery electrode suitable as a material for forming an electrode such as a positive electrode that constitutes a lithium ion battery, a lithium ion battery electrode containing the composite material, and a lithium ion battery.

A lithium-ion battery is a secondary battery having a structure in which lithium ions are desorbed from the positive electrode as ions during charging, moved to the negative electrode and absorbed, and lithium ions are inserted back into the positive electrode from the negative electrode during discharging. This lithium-ion battery has features such as high energy density and long life, so it is used in notebook personal computers, home appliances such as cameras, portable electronic devices such as mobile phones, communication devices, It is widely used as a power source for electric tools such as power tools, and recently, it is also used for large batteries mounted on electric vehicles (EV), hybrid electric vehicles (HEV), and the like. In such a lithium-ion battery, if a solid electrolyte is used instead of an electrolyte solution containing a combustible organic solvent, not only can the safety device be simplified, but also the manufacturing cost and productivity can be improved. Research on various materials is actively progressing. Among them, solid electrolytes containing sulfides have high electrical conductivity (lithium ion conductivity) and are said to be useful for increasing the output of batteries.

Conventionally, sulfide solid electrolytes do not contain organic solvents that decompose at high potentials, unlike electrolytic solutions, so it has been thought that they have a wide potential window, that is, they are electrically stable and do not undergo oxidative decomposition. However, in recent years, as described in Patent Document 1, sulfide solid electrolytes are particularly unstable at high potentials, and are electrolyzed at interfaces in contact with active materials exposed to high potentials, resulting in electrolyzed sulfides It has been found that the ionic conductivity of the solid electrolyte is extremely low, resulting in deterioration of the charge/discharge characteristics of the battery. In recent years, it has been found that oxidative decomposition occurs to a small extent in the high potential region.
The above Patent Document 1 includes a sulfide layer containing a sulfide material and an oxide layer containing an oxide obtained by oxidizing the sulfide material, the oxide layer being located on the surface of the sulfide layer, XPS (X-ray Photoelectron Spectroscopy, X-ray photoelectron spectroscopy) x is the oxygen / sulfur element ratio of the outermost surface of the oxide layer measured by XPS depth profile analysis, measured by XPS depth _profile analysis, converted to SiO A sulfide solid electrolyte material satisfying 1.28 ≤ x ≤ 4.06 and x/y ≥ 2.60, where y is the oxygen/sulfur element ratio at a position 32 nm from the outermost surface of the oxide layer at the sputtering rate; A battery including it is disclosed.

In addition, it is said that the charge-discharge characteristics of a lithium-ion battery depend not a little on the configuration of the electrodes. In order to reduce (interfacial resistance), a positive electrode active material containing lithium cobalt oxide and a coating layer containing lithium niobate is formed on at least a part of the surface, and a solid electrolyte containing solid sulfide. and a peak different from the main peak detected in the electronic state analysis by XPS analysis is detected on the lower energy side than the main peak. It is In addition, Patent Document 3 discloses an active material particle containing at least one of cobalt element, nickel element, and manganese element and further containing lithium element and oxygen element, and all or part of the surface of the active material particle and a sulfide-based solid electrolyte further covering 76.0% or more of the surface of the composite particles. there is

JP 2018-26321 A JP 2010-73539 A JP 2014-154407 A

An object of the present invention is to provide a lithium ion battery having excellent charge/discharge cycle characteristics, and a composite material for battery electrodes and a lithium ion battery electrode that provide such a lithium ion battery.

The present invention is shown below.
[1] a matrix phase containing a solid electrolyte containing Li atoms, P atoms and S atoms, and a compound containing Li atoms and F atoms; and at least one selected from Co atoms, Ni atoms and Mn atoms, and a dispersed phase containing a composite oxide containing O atoms.
[2] The compound containing Li atoms and F atoms is LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) The composite material for a battery electrode according to the above [ ₁ ], which is at least one selected from ₂ , _{LiC ( SO2CF3} ) _{3 , LiSO3CF3} and _LiSO3C4F9 .
[3] The dispersed phase is a composite comprising a core portion made of the composite oxide and a coating portion in which at least a part of the surface of the core portion is coated with a lithium ion conductive oxide [1] ] or the composite material for battery electrodes according to [2].
[4] The composite material for a battery electrode according to [3] above, wherein the lithium ion conductive oxide is a composite oxide containing Li atoms, other metal atoms, and O atoms.
[5] The composite material for a battery electrode according to [3] or [4] above, wherein the lithium ion conductive oxide is LiNbO ₃ .
[6] The above [1] to [5], wherein the solid electrolyte contains at least one selected from Li ₃ PS ₄ and Li ₆ PS ₅ X ¹ (X ¹ is a Cl atom, a Br atom or an I atom). The composite material for battery electrodes according to any one of claims 1 to 3.
[7] The composite material for a battery electrode according to any one of [1] to [6] above, wherein the matrix phase further contains LiX ² (X ² is Cl atom, Br atom or I atom).
[8] A lithium ion battery electrode comprising the composite material for a battery electrode according to any one of [1] to [7] above.
[9] A lithium ion battery comprising the lithium ion battery electrode according to [8] above.

According to the composite material for a battery electrode and the electrode for a lithium ion battery of the present invention, a lithium ion battery having excellent charge/discharge cycle characteristics can be provided.

1 is a schematic cross-sectional view showing a main part of a lithium ion battery of the present invention; FIG. 4 is a graph showing the temperature dependence of the electrical conductivity of solid electrolyte compositions or solid electrolytes obtained in Experimental Examples 1-1 to 1-3. 1 is a potential-current curve of solid electrolyte compositions or solid electrolytes obtained in Experimental Examples 1-1 to 1-3. 4 is a graph showing the temperature dependence of the electrical conductivity of solid electrolyte compositions or solid electrolytes obtained in Experimental Examples 1-4 to 1-6. 1 is a potential-current curve of solid electrolyte compositions or solid electrolytes obtained in Experimental Examples 1-4 to 1-6. Fig. 2 is a schematic cross-sectional view showing a charging test measurement cell containing an all-solid-state lithium-ion battery fabricated in [Example]. 1 is a graph showing charge/discharge characteristics of lithium ion batteries obtained in Experimental Examples 1 and 2 and Comparative Example 1. FIG. 4 is a graph showing the results of a charge-discharge cycle test of lithium ion batteries obtained in Experimental Examples 1 and 2 and Comparative Example 1. FIG.

The composite material for battery electrodes of the present invention includes a solid electrolyte containing Li atoms, P atoms and S atoms (hereinafter referred to as "sulfur-based solid electrolyte (A1)") and a compound containing Li atoms and F atoms (hereinafter referred to as " and at least one selected from Li atoms, Co atoms, Ni atoms and Mn atoms dispersed in the matrix phase, and and a dispersed phase containing a composite oxide containing O atoms.

The form of the composite material for battery electrodes of the present invention is not particularly limited as long as it has the above structure, and may be powder, granule, paste, slurry, or the like.

The matrix phase is a phase containing a sulfur-based solid electrolyte (A1) and a fluorine-containing compound, preferably a phase comprising a mixture thereof.

The sulfur-based solid electrolyte (A1) is not particularly limited as long as it is a compound containing Li atoms, P atoms and S atoms, and may be a compound further containing other atoms.
The sulfur-based solid electrolyte (A1) includes a Li ₂ SP ₂ S ₅ -based solid electrolyte and a Li ₂ SP ₂ S ₅ -LiX ¹ -based solid electrolyte (where X ¹ is a Cl atom, a Br atom, or an I atom). is mentioned. Specific compounds include Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , Li ₂ P ₂ S ₆ , Li ₇ P ₂ S ₈ X ¹ (X ¹ is Cl atom, Br atom or I atom), Li ₆ PS ₅ X ¹ (X ¹ is Cl atom, Br atom or I atom) and the like. Among these, Li ₃ PS ₄ and Li ₆ PS ₅ X ¹ (X ¹ is Cl atom, Br atom or I atom) are preferred. The sulfur-based solid electrolyte (A1) contained in the matrix phase can be one type or two or more types.

The fluorine-containing compound is not particularly limited as long as it is a compound containing Li atoms and F atoms, and may be compounds further containing other atoms.
Examples of the fluorine-containing compounds include LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ , LiSO ₃ CF ₃ , LiSO ₃ C ₄ F ₉ and the like. The fluorine-containing compound contained in the matrix phase can be one type or two or more types.

Since the effects of the present invention can be sufficiently obtained, the content of the sulfur-based solid electrolyte (A1) and the fluorine-containing compound in the matrix phase is preferably 50 to 99 mol, respectively, when the total of both is 100 mol%. % and 1 to 50 mol %, more preferably 60 to 95 mol % and 5 to 40 mol %, still more preferably 70 to 90 mol % and 10 to 30 mol %.

Furthermore, the matrix phase can contain components other than the solid electrolyte and the fluorine-containing compound, if necessary. Other components include LiX ² (X ² is Cl atom, Br atom or I atom) and the like.
When the matrix phase contains other components, the content is preferably 5 to 60 parts by mass, more preferably 5 to 60 parts by mass when the total amount of the sulfur-based solid electrolyte (A1) and the fluorine-containing compound is 100 parts by mass. is 10 to 40 parts by mass.

Next, the dispersed phase is a composite oxide containing Li atoms, at least one selected from Co atoms, Ni atoms and Mn atoms, and O atoms (hereinafter referred to as "composite oxide (C)"). and is a component that acts as an active material that absorbs or releases lithium ions. In the present invention, the dispersed phase may be a single-phase dispersed phase consisting only of the composite oxide (C), and at least a portion of the surface of the core consisting of the composite oxide (C) is lithium ion conductive. A composite dispersed phase composed of a composite having a structure coated with a conductive oxide (hereinafter referred to as "lithium ion conductive oxide (D)"), that is, a core and at least a part of the surface of the core It may be a composite dispersed phase composed of a composite including a covering portion covered with a lithium ion conductive oxide (D).

The composite oxide (C) is a compound composed of Li atoms, at least one selected from Co atoms, Ni atoms and Mn atoms, and O atoms (hereinafter referred to as "composite oxide (C1)"). in addition to these atoms, also other metal atoms (Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, etc.); or a compound containing a halogen atom. Among these, the composite oxide (C1) is preferred. In the present invention, the composite oxide (C) that constitutes the dispersed phase can be of one type or two or more types.

The composite oxide (C1) is preferably a compound represented by the following general formula (1).
_{LimNixCoyMnzOn ( 1 ) _}
(Wherein, m is a number that satisfies 0 < m ≤ 2, n is a number that satisfies 0 < n / m ≤ 4, x, y, z are 0 ≤ x ≤ 2, 0 ≤ y ≤ 2, 0 ≤ z ≤ 2, and 0 < (x + y + z) / m ≤ 2)

Examples of compounds represented by the general formula (1) include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoMnO ₄ , Li ₂ NiMn ₃ O ₈ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ and the like.

When the dispersed phase is a composite dispersed phase, the lithium ion conductive oxide (D) covering at least part of the surface of the core portion made of the composite oxide (C) has lithium ion conductivity, It is not particularly limited as long as it is different from the composite oxide (C).

The lithium ion conductive oxide (D) has high surface acidity because it suppresses an increase in interfacial resistance between the sulfur-based solid electrolyte (A1) and the composite oxide (C). Oxidation of zirconium oxide (ZrO ₂ ), tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), boron oxide (B ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), etc. and compounds containing Li atoms, other metal atoms, and O atoms (composite oxides) having lithium ions.
Other metal atoms in the latter composite oxide include Nb atoms, Al atoms, Mo atoms, Si atoms, Fe atoms, Zr atoms, W atoms, V atoms, Ti atoms, Ta atoms and the like. Among these, Nb atoms are preferred. _The latter composite _oxides include _LiNbO3 , _LiNbO2 , _LiAlO2 , _Li2MoO4 , _Li4SiO4 , _{Li4FeO4 , Li4ZrO4 , Li2W2O7 , Li3VO4 , Li 4} Ti ₅ O ₁₂ , LiTaO ₃ and the like. Among these, LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ and LiTaO ₃ are preferred, and LiNbO ₃ is particularly preferred.

In the composite constituting the composite dispersed phase, it is preferable that the covering portion made of the lithium ion conductive oxide (D) is present on the entire surface of the core portion made of the composite oxide (C). The thickness of the covering portion is not particularly limited, but the average value is preferably 1 to 20 nm, more preferably 2 to 10 nm.

The shape and size of the dispersed phase contained in the matrix phase are not particularly limited. The shape of the dispersed phase can be a sphere, an ellipsoid, a polyhedron, an irregular shape, or the like. Further, the size (particle diameter) of the dispersed phase can be 1 to 50 μm.

In the composite material for a battery electrode of the present invention, the mass ratio of the matrix phase and the dispersed phase is not particularly limited, but from the viewpoint of the battery capacity, when the total of both is 100% by mass, each is preferably 5 to 70. % by mass and 30 to 95% by mass, more preferably 10 to 40% by mass and 60 to 90% by mass.

The matrix phase constituting the composite material for a battery electrode of the present invention may contain, in addition to the dispersed phase, a conductive aid made of a carbon material, a metal powder, a metal compound, or the like. Among these, carbon materials are preferable, for example, plate-shaped conductive substances such as graphene; linear conductive substances such as carbon nanotubes and carbon fibers; Carbon black such as channel black, granular conductive material such as graphite, and the like can be used.

The method for producing the composite material for battery electrodes of the present invention can be appropriately selected depending on the form thereof. It can be manufactured by a method of using as, mixing these, and molding the obtained powder mixture.
(1) A method using a sulfur-based solid electrolyte (A1), a fluorine-containing compound, a composite oxide (C), and, if necessary, a conductive aid as raw materials (2) A sulfur-based solid electrolyte as a raw material (A1), a composite having a core composed of a fluorine-containing compound and a composite oxide (C), and a coating having at least a portion of the surface of the core coated with a lithium ion conductive oxide (D) , and, if necessary, a method (3) using a conductive agent as a raw material, a sulfur-based solid electrolyte (A1), a fluorine-containing compound, a composite oxide (C), and a core portion composed of a composite oxide (C) , a composite having a coating portion in which at least part of the surface of the core portion is coated with a lithium ion conductive oxide (D), and, if necessary, a method using a conductive aid

The composite used in the above methods (2) and (3) can be obtained, for example, by a method using a tumbling fluidized bed coating apparatus. In this apparatus, a dispersion of the lithium ion conductive oxide (D) or a precursor of the lithium ion conductive oxide (D) is prepared in a state in which the powder composed of the composite oxide (C) is made into a fluidized bed by an introduced gas. After spraying the solution or dispersion liquid of the solid, if necessary, heat treatment is performed to form a film on the surface of the powder composed of the composite oxide (C). The amount or thickness of the film to be formed can be controlled by the liquid spray amount, spray speed, or the like.

In these methods (1) to (3), the method of mixing the raw materials is not particularly limited, and a conventionally known dry mixing method for preparing a mixture of ceramic powders is preferably applied. , a bead mill, a ball mill (planetary ball mill, etc.), a vibration mill, a turbo mill, a mechanofusion, a disk mill, or the like.

Moreover, the method for molding the powder mixture is not particularly limited, and a conventionally known press molding method or the like is preferably applied. During molding, heating may be performed as long as the raw materials do not change in quality or react with each other.

The composite material for a battery electrode of the present invention is suitable as a material for forming a lithium ion battery electrode, preferably a positive electrode.

The lithium ion battery electrode of the present invention is an article containing the composite material for a battery electrode of the present invention, and is usually a regular structure such as a thin body.
The lithium ion battery electrode of the present invention may be obtained only from the composite material for battery electrode of the present invention comprising the above matrix phase and dispersed phase, or the composite material for battery electrode of the present invention comprising the above matrix phase and dispersed phase. and other components such as conductive aids, binders and other solid electrolytes.

Examples of the binder include polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polyvinylidene fluoride (PVdF), fluorine-containing resins such as vinylidene fluoride-hexafluoropropylene copolymer; polyolefins such as polypropylene and polyethylene. system resin; ethylene/propylene/non-conjugated diene rubber (EPDM etc.), sulfonated EPDM, natural butyl rubber (NBR) and the like.

The lithium ion battery of the present invention is an article provided with the lithium ion battery electrode of the present invention, and has the structure shown in FIG. The lithium ion battery 10 of FIG. 1 includes a positive electrode 11 and a negative electrode 13, which are electrodes for a lithium ion battery, and an electrolyte layer 15 disposed between the positive electrode 11 and the negative electrode 13 to exchange lithium ions therebetween. Prepare. The lithium ion battery of the present invention further includes a positive electrode current collector that collects current from the positive electrode 11 and a negative electrode current collector that collects current from the negative electrode 15 on the outer surface side of each of the positive electrode 11 and the negative electrode 13. (not shown). As described above, the positive electrode 11 of the lithium ion battery 10 preferably contains the composite material for a battery electrode of the present invention.

The negative electrode 13 usually contains a negative electrode active material, and may further contain a binder, a conductive aid, and the like. Examples of negative electrode active materials include carbon materials; metals such as lithium, indium, aluminum and silicon, and alloys containing these.

The electrolyte layer 15 is not particularly limited as long as it contains a solid electrolyte. As solid electrolytes, oxide-based solid electrolytes, sulfide-based solid electrolytes, polymer electrolytes, _LiBH4 and related hydrides, etc. can be used.
Preferably, the electrolyte layer 15 is substantially made of a solid electrolyte.

The positive electrode current collector 17 or the negative electrode current collector 19 can be made of, for example, stainless steel, gold, platinum, copper, zinc, nickel, tin, aluminum, or alloys thereof. It can have a shape, a mesh, and the like.

The lithium ion battery of the present invention includes an electrode made of the composite material for a battery electrode of the present invention, that is, a matrix phase and a dispersed phase containing a sulfur-based solid electrolyte (A1) and a fluorine-containing compound. The sulfide solid electrolyte, which tends to be unstable with respect to potential, electrolyzes at the interface where it contacts the active material, and the ion conductivity of the electrolyzed sulfide solid electrolyte decreases, resulting in deterioration of the charge-discharge characteristics of the battery. It is possible to suppress defects that cause deterioration. This effect is particularly remarkable when the dispersed phase is the composite dispersed phase.

1. Production raw materials The raw materials used for production of the solid electrolyte are as follows.
1-1. Phosphorus pentasulfide (P ₂ S ₅ ) powder “P ₂ S ₅ ” (trade name) manufactured by Aldrich was used. The purity is 99% and the particle size is 100 μm.
1-2. Lithium sulfide (Li ₂ S) powder “Li ₂ S” (trade name) manufactured by Mitsuwa Chemicals Co., Ltd. was used. The purity is 99.9% and the particle size is about 50 μm.
1-3. Lithium chloride (LiCl) powder “LiCl” (trade name) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used. The purity is 99.9% and the particle size is several tens of μm.
1-4. Lithium tetrafluoroborate (LiBF ₄ ) powder “LiBF ₄ ” (trade name) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used. The purity is 99.9% and the particle size is several μm.
1-5. Lithium bis(fluorosulfonyl)imide (LiFSI) powder "LiN( _{SO2F)2 "} (trade name) manufactured by Nippon Shokubai Co., Ltd. was used. The purity is 99% and the particle size is several μm.

2. Manufacture and Evaluation of Solid Electrolyte Composition or Solid Electrolyte A solid electrolyte composition or solid electrolyte was manufactured using the raw materials described above, and the temperature dependence of conductivity was evaluated.

Experimental Example 1-1 (Production of Solid Electrolyte Composition S1)
Lithium sulfide (Li ₂ S) powder, diphosphorus pentasulfide (P ₂ S ₅ ) powder, lithium chloride (LiCl) powder, and lithium tetrafluoroborate (LiBF ₄ ) powder were combined with Li ₂ S, P ₂ S ₅ , LiCl and LiBF ₄ were weighed and mixed so that the molar ratio was 5:1:2:0.5. Next, the mixed powder is placed in a planetary ball mill manufactured by Frisch ₍ container: made of zirconia) together with zirconia balls having a diameter of 10 mm, and subjected to mechanical milling ₍ rotation speed: ₆₀₀ rpm, 20 hours). A solid electrolyte composition S1 comprising a ratio of 80:20 was obtained.

After that, the temperature dependence of the electrical conductivity of the solid electrolyte composition was evaluated by the following method. Specifically, the obtained solid electrolyte composition was made into a disc-shaped test piece (size: 5 mm in radius × 0.6 mm in height) using a uniaxial hydraulic press, and placed in a measurement unit under an argon gas atmosphere. (Glass container), wrap the ribbon heater and heat insulating material connected to the temperature controller around the measurement unit (glass container), and use SOLATRON's IMPEDANCE ANALYZER "S1260" (model name) to It was gradually heated from room temperature and the conductivity was measured at 25°C, 50°C, 70°C, 90°C or 110°C. The electrical conductivity was measured after the test piece was allowed to stand still for 1 hour after starting to be held at each temperature. In addition, the conductivity was measured at each temperature from the low temperature side in sequence, but the temperature was not measured by increasing the temperature step by step. After that, a method of raising the temperature and measuring at 70° C. was adopted.
A graph showing the temperature dependence of conductivity is shown in FIG.

Next, the capacity of the solid electrolyte composition was evaluated by a potential sweep (cyclic voltammetry) method. Specifically, a cell having a configuration of SUS/Li—In alloy foil/solid electrolyte composition/SUS was produced, and the voltage range was 3.0-6.5 V vs. CV measurement was performed with Li/Li ⁺ to examine the oxidation-reduction current when the voltage sweep rate was changed at 0.1 mV/s.
A potential-current curve is shown in FIG.

Experimental Example 1-2 (Production of Solid Electrolyte Composition S2)
The same operation as in Experimental Example 1-1 was performed except that lithium bis(fluorosulfonyl)imide (LiFSI) powder was used instead of lithium tetrafluoroborate (LiBF ₄ ) powder, and Li ₆ PS ₅ Cl and LiFSI at a molar ratio of 80:20 to obtain a solid electrolyte composition S2.
Thereafter, the same operation as in Experimental Example 1-1 was performed to prepare a graph showing the temperature dependence of the electrical conductivity of the solid electrolyte composition and a potential-current curve (see FIGS. 2 and 3).

Experimental Example 1-3 (Production of Solid Electrolyte S3)
Lithium sulfide (Li ₂ S) powder, diphosphorus pentasulfide (P ₂ S ₅ ) powder, and lithium chloride (LiCl) powder are mixed so that the molar ratio of Li ₂ S, P ₂ S ₅ and LiCl is They were weighed to be 5:1:2 and mixed. Next, the mixed powder was placed in a planetary ball mill manufactured by Frisch (container: made of zirconia) together with zirconia balls having a diameter of 10 mm, and subjected to mechanical milling (600 rpm for 20 hours) to obtain a solid electrolyte S3 composed of Li ₆ PS ₅ Cl. got
Thereafter, the same operation as in Experimental Example 1-1 was performed to prepare a graph showing the temperature dependence of the electrical conductivity of the solid electrolyte and a potential-current curve (see FIGS. 2 and 3).

From FIG. 2, it can be seen that the lithium ion conductivity of the solid electrolyte compositions S1 and S2 is superior to that of the solid electrolyte S3 at temperatures above 50.degree.
Further, from FIG. 3, in the case of the solid electrolyte composition S1 and the solid electrolyte composition S2, if the potential is up to about 4.0 V, no increase in the current value is confirmed, and the oxidation deterioration of the solid electrolyte does not occur. , the potential window is wide, that is, it is possible to form an electrode that is electrically stable. Therefore, the solid electrolyte composition S1 and the solid electrolyte composition S2 are suitable as constituent materials for positive electrodes of lithium ion batteries. On the other hand, in the case of the solid electrolyte S3, when the potential exceeds about 3.3 V, current flows, and it is clear that the potential window is narrow.

Experimental Example 1-4 (Production of Solid Electrolyte Composition S4)
Lithium sulfide (Li ₂ S) powder, diphosphorus pentasulfide (P ₂ S ₅ ) powder, and lithium tetrafluoroborate (LiBF ₄ ) powder were combined with Li ₂ S, P ₂ S ₅ and LiBF. ₄ were weighed so that the molar ratio of 4 was 3:1:0.5, and these were mixed. Next, the mixed powder is placed in a planetary ball mill manufactured by Frisch ₍ container: made of zirconia) together with zirconia balls having a diameter of ₁₀ mm, and mechanical milling is performed ₍ 600 rpm for 20 hours). A solid electrolyte composition S4 containing 80:20 was obtained.
Thereafter, the same operation as in Experimental Example 1-1 was performed to prepare a graph showing the temperature dependence of the electrical conductivity of the solid electrolyte composition and a potential-current curve (see FIGS. 4 and 5). The temperatures for measuring the electrical conductivity of the solid electrolyte composition were 25°C, 50°C, 70°C, 90°C, 110°C, 130°C and 150°C.

Experimental Example 1-5 (Production of Solid Electrolyte Composition S5)
Lithium sulfide (Li ₂ S) powder, diphosphorus pentasulfide (P ₂ S ₅ ) powder, lithium tetrafluoroborate (LiBF ₄ ) powder, and lithium chloride (LiCl) powder were combined with Li ₂ S, P ₂ S ₅ , LiBF ₄ and LiCl were weighed and mixed in a molar ratio of 15:5:6:4. Next, the mixed powder was placed in a Frisch planetary ball mill (container: made of zirconia) together with zirconia balls having a diameter of 10 mm, and subjected to mechanical milling (600 rpm for 20 hours) to remove Li ₃ PS ₄ , LiBF ₄ and LiCl. A solid electrolyte composition S5 containing at a molar ratio of 50:30:20 was obtained.
After that, the same operation as in Experimental Example 1-4 was performed to prepare a graph showing the temperature dependence of the electrical conductivity of the solid electrolyte composition and a potential-current curve (see FIGS. 4 and 5).

Experimental Example 1-6 (Production of Solid Electrolyte S6)
Lithium sulfide (Li ₂ S) powder and diphosphorus pentasulfide (P ₂ S ₅ ) powder were weighed so that the molar ratio of Li ₂ S and P ₂ S ₅ was 3:1. were mixed. Next, the mixed powder is placed in a planetary ball mill manufactured by Frisch (container: made of zirconia) together with zirconia balls having a diameter of 10 mm, and subjected to mechanical milling ₍ 600 rpm for 20 hours) to form a solid electrolyte S6 composed of _Li3PS4 . Obtained.
Thereafter, the same operation as in Experimental Example 1-4 was performed to prepare a graph showing the temperature dependence of the electrical conductivity of the solid electrolyte and a potential-current curve (see FIGS. 4 and 5).

From FIG. 4, it can be seen that the lithium ion conductivity of the solid electrolyte composition S5 is superior to that of the solid electrolyte composition S4 and the solid electrolyte S6.
Further, from FIG. 5, in the case of the solid electrolyte composition S4 and the solid electrolyte composition S5, if the potential is up to about 4.7 V, no increase in the current value is confirmed, and the oxidation deterioration of the solid electrolyte does not occur. , the potential window is wide. On the other hand, in the case of the solid electrolyte S6, when the potential exceeds about 3.5 V, current flows, and it is clear that the potential window is narrow.

3. Composite material for battery electrode, production and evaluation of positive electrode and lithium ion battery A composite material was produced. Thereafter, this battery electrode composite material is used to form a positive electrode, and is used in combination with a solid electrolyte S3 (for electrolyte layer) and a Li—In alloy foil (for negative electrode) to form an all-solid-type battery having the structure shown in FIG. A lithium-ion battery was produced.
(1) Active material LiNbO obtained by coating the surface of lithium nickel manganese cobaltate (LiNi _0.5 Mn _0.3 Co _0.2 O ₂ ) particles with LiNbO ₃ using a tumbling fluidized bed coating apparatus. ₃ coated particles (particle diameter: 3 to 10 μm, coating thickness: 5 nm).
(2) Carbon fiber Vapor-grown carbon fiber “VGCF” (trade name) manufactured by Showa Denko KK was used.

Example 1
Solid electrolyte composition S1, active material, and carbon fiber were weighed at a mass ratio of 50:50:3, and mixed using a mortar and pestle to obtain a composite material for a battery electrode.
On the other hand, powder of the solid electrolyte S3 was pressure-molded using a uniaxial hydraulic press to obtain a preform (disc shape, radius: 5 mm, thickness: 0.5 mm) for the electrolyte layer.
After that, while the electrolyte layer preform is housed inside a cylindrical body 17 made of polyetheretherketone (PEEK), the battery electrode composite obtained above is coated on the entire one surface side thereof. About 25 mg of the material was filled, and pressure molding was performed using a uniaxial hydraulic press to obtain a plate-like positive electrode. Furthermore, a Li—In alloy foil (thickness: 0.1 mm, diameter: 5 mm) for the negative electrode is attached to the other surface of the electrolyte layer preform, and the positive electrode 11, the electrolyte layer 15, and the negative electrode 13 are sequentially attached. , an all-solid-state lithium-ion battery 10 was obtained (see FIGS. 1 and 6).
Next, from both sides of the cylindrical body 17 containing the lithium ion battery 10, stainless steel-nickel conductive parts were inserted and fixed with a jig to obtain a measurement cell (see FIG. 6). Then, this measurement cell was enclosed in a glass container (not shown), and the gas in the glass container was replaced with argon gas to conduct a charge/discharge test. In the charge-discharge test, the glass container containing the measurement cell is placed in an electric furnace set at 30 ° C., using a charge-discharge device "BTS-2004H" (model name) manufactured by NAGANO, (0.1-3.0 V vs. Li--In, C rate: 0.1C). The results are shown in FIG.
Moreover, when this charge/discharge test was performed with 60 cycles, the graph of FIG. 8 was obtained.

Example 2
A composite material for a battery electrode was obtained in the same manner as in Example 1, except that the solid electrolyte composition S2 was used instead of the solid electrolyte composition S1. Then, a lithium ion battery was manufactured and a charge/discharge test was performed. The results are shown in FIGS. 7 and 8. FIG.

Comparative example 1
A composite material for a battery electrode was obtained in the same manner as in Example 1, except that the solid electrolyte composition S1 was replaced with the solid electrolyte S3. Then, a lithium ion battery was manufactured and a charge/discharge test was performed. The results are shown in FIGS. 7 and 8. FIG.

As is clear from FIGS. 7 and 8, the lithium ion batteries of Examples 1 and 2 provided with positive electrodes obtained using solid electrolyte compositions S1 and S2 containing compounds containing Li atoms and F atoms, It can be seen that both the discharge capacity and the cycle characteristics are superior to the lithium ion battery of Comparative Example 1. This means that in a lithium-ion battery comprising an electrode formed using the composite material for a battery electrode of the present invention, the solid electrolyte contained in the electrode is prevented from oxidizing and deteriorating at an early stage when charging and discharging are repeated.

The composite material for battery electrodes of the present invention can be used for home appliances such as personal computers and cameras, power storage devices, portable electronic devices such as mobile phones or communication devices, power sources such as power tools such as power tools, and electric vehicles. (EV), hybrid electric vehicle (HEV), etc., and is suitable as a constituent material for electrodes of lithium ion batteries constituting large batteries.

10: Lithium ion battery 11: Positive electrode 13: Negative electrode 15: Electrolyte layer 17: PEEK tubular body 21: Pressing plate 23: Pressing pin 25: Tightening screw 27: Kapton (registered trademark) tape

Claims (9)

a matrix phase containing a solid electrolyte containing Li atoms, P atoms and S atoms; and a compound containing Li atoms and F atoms; A composite material for a battery electrode, comprising a dispersed phase containing a composite oxide containing at least one selected from atoms, Ni atoms and Mn atoms, and O atoms. The compound containing Li atoms and F atoms is LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , _{LiC ( SO2CF3} ) _{3 , LiSO3CF3 and LiSO3C4F9} . 3. According to claim 1 or 2, wherein the dispersed phase comprises a composite comprising a core made of the composite oxide and a covering portion in which at least a part of the surface of the core is covered with a lithium ion conductive oxide. A composite material for a battery electrode as described. 4. The composite material for a battery electrode according to claim 3, wherein said lithium ion conductive oxide is a composite oxide containing Li atoms, other metal atoms and O atoms. 5. The composite material for battery electrodes according to claim ₃ or 4, wherein said lithium ion conductive oxide is LiNbO3. 6. The solid electrolyte according to any one of claims 1 to ₅ , wherein the solid electrolyte contains at least ^one selected from _Li3PS4 and _{Li6PS5X1 (} X1 is ^a Cl atom, a Br atom or an I atom). of composite materials for battery electrodes. The composite material for a battery electrode according to any one of claims 1 to 6, wherein the matrix phase further contains ^{LiX2 (} X2 is a Cl atom, a Br atom or an I atom). A lithium ion battery electrode comprising the battery electrode composite material according to claim 1 . A lithium ion battery comprising the lithium ion battery electrode according to claim 8 .

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