JP2010245038A - Positive electrode mixture and lithium battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an all-solid lithium battery superior in output characteristics. <P>SOLUTION: The positive electrode mixture contains a particle of a compound as expressed by the following formula (1) and a sulfide system solid electrolyte particle, and the tap density of the particle expressed by the formula (1) is 2.0 g/cm<SP>3</SP>or more. Formula (1): Li<SB>a</SB>Ni<SB>b</SB>Co<SB>c</SB>Mn<SB>d</SB>M<SB>e</SB>O<SB>f+σ</SB>. In the formula (1), a is larger than 0.9 and 1.05 or less, f is 2 or 4, σ is -0.2 or more and 0.2 or less, M is one kind or more of element selected from Mg, Ca, Y, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, N, P, S, F and Cl. When f=2, b is 0 or more and 1 or less, c is 0 or more and 1 or less, d is 0 or more and 1 or less, e is 0 or more and 0.5 or less, and b, c, d and e are b+c+d+e=1. When f is 4, b is 0 or more and 2 or less, c is 0 or more and 2 or less, d is 0 or more and 2 or less, e is 0 or more and 1 or less, and b, c, d and e are b+c+d+e=2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a positive electrode mixture used for a lithium battery or the like. The present invention also relates to a lithium battery having high safety by using a nonflammable electrolyte, that is, an inorganic solid electrolyte.

For lithium batteries using flammable organic solvent electrolytes, concerns about their safety, such as ignition, are an essential problem. A drastic solution to this problem is to use a non-flammable electrolyte instead of a flammable organic solvent electrolyte.
A typical non-flammable electrolyte is an inorganic lithium ion conductive solid electrolyte. The use of inorganic solid electrolytes not only increases safety, but also reduces battery life and integrates them with electronic circuits, and because the inorganic solid electrolytes have ion selectivity, cycle life and shelf life It is also possible to improve the reliability of the battery.

  In a lithium battery using a liquid electrolyte, many of the causes of capacity reduction and self-discharge associated with charge / discharge cycles are side reactions occurring in the battery. Specifically, lithium ions are the only ions that contribute to the electrode reaction of lithium ion batteries, but in the liquid electrolyte, anions, solvent molecules, and further impurities move. When these diffuse to the positive electrode surface having a high oxidizing power or the negative electrode surface having a high reducing power, they may be oxidized or reduced. Such a side reaction causes a decrease in battery characteristics.

  Since the liquid electrolyte has no ion selectivity, the above-mentioned side effect occurs in the battery using the liquid electrolyte. On the other hand, the inorganic solid electrolyte has ion selectivity. That is, only lithium ions move through the lithium ion conductive inorganic solid electrolyte. Therefore, as in the liquid electrolyte, side reactions do not continue due to diffusion of substances other than lithium ions on the electrode surface. Therefore, a lithium ion battery (all solid lithium battery) using an inorganic solid electrolyte has a long life and low self-discharge.

However, the all-solid lithium battery has a problem that the obtained output density is lower than that of the liquid electrolyte type.
To solve this problem, for example, a method using a carbon material having a low potential and a high capacity density as a negative electrode material of an all-solid lithium secondary battery has been proposed (see Patent Documents 1 and 2). Although this can increase the energy density of the all-solid lithium secondary battery, the output density obtained in this secondary battery is about several hundred microamperes per square centimeter, which is still lower than that of the liquid electrolyte system. Met.

JP 2003-68361 A JP 2003-217663 A

The all solid lithium battery has excellent reliability including safety as described above. However, in general, the energy density or power density is lower than that of the liquid electrolyte type, and it is necessary to solve this problem particularly when used as a general-purpose battery.
An object of the present invention is to solve the above-described problems and provide an all-solid lithium battery excellent in output characteristics.

According to the present invention, the following positive electrode mixture and lithium battery are provided.
1. The positive electrode active material particles represented by the following formula (1) and sulfide solid electrolyte particles are included, and the tap density of the particles represented by the formula (1) is 2.0 g / cm ³ or more. Characteristic positive electrode composite.
Li _a Ni _b Co _c Mn _{d Me} O _{f + σ} (1)
[In Formula (1), a is larger than 0.9 and 1.05 or less, f is 2 or 4, σ is −0.2 or more and 0.2 or less, M is Mg, Ca, Y, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, N, P, S, F , One or more elements selected from Cl. When f = 2, b is 0 or more and 1 or less, c is 0 or more and 1 or less, d is 0 or more and 1 or less, e is 0 or more and 0.5 or less, and b, c, d, and e are b + c + d + e = 1. Fulfill. When f = 4, b is from 0 to 2, c is from 0 to 2, d is from 0 to 2, e is from 0 to 1, and b, c, d, and e satisfy b + c + d + e = 2. ]
2. 2. The positive electrode composite material according to 1, wherein the particles of the positive electrode active material represented by the formula (1) are surface-modified with a lithium ion conductive oxide.
3. Formula (1) particle size of the particles of the positive electrode active material represented by is at 1μm or more 10μm or less and a specific surface area of not more than 0.20 m ² / g or more 0.8 m ² / g, the sulfide-based solid 3. The positive electrode mixture according to 1 or 2, wherein the particle diameter of the electrolyte particles is 0.01 μm or more and 50 μm or less.
4). The positive electrode active material particles represented by the formula (1) have a particle size of 4.2 μm or more and 7.0 μm or less, and a specific surface area of 0.35 or more and 0.7 m ² / g or less. The positive electrode composite material according to 1 or 2.
5). The positive electrode active material particles represented by the formula (1) and b = 0 include secondary particles and / or single crystal particles composed of a plurality of primary particles, and are defined by the following formula (2). 1 or more and 10 or less, The positive electrode compound material in any one of 1-4 characterized by the above-mentioned.
A = (m + p) / (m + s) (2)
(Where m is the number of single crystal particles, s is the number of secondary particles, and p is the number of primary particles constituting the secondary particles.)
6). The positive electrode composite material according to any one of 1 to 4, wherein the positive electrode active material represented by the formula (1) is Li _a CoO _{2 + σ} .
7). A lithium battery comprising: a positive electrode comprising the positive electrode mixture according to any one of 1 to 6 above; and an electrolyte layer containing a sulfide-based solid electrolyte.

  ADVANTAGE OF THE INVENTION According to this invention, the all-solid-state lithium battery excellent in the output characteristic can be provided.

It is a schematic sectional drawing of the lithium battery which is one Embodiment of this invention.

The positive electrode mixture of the present invention includes positive electrode active material particles and sulfide-based solid electrolyte particles. The positive electrode active material particles have a tap density of 2.0 g / cm ³ or more. The positive electrode mixture is a material for a positive electrode of a battery, and is a mixture of a positive electrode active material and a solid electrolyte.

In the positive electrode mixture of the present invention, the positive electrode active material uses particles of the positive electrode active material represented by the following formula (1).
Li _a Ni _b Co _c Mn _{d Me} O _{f + σ} (1)
[In Formula (1), a is larger than 0.9 and 1.05 or less, f is 2 or 4, σ is −0.2 or more and 0.2 or less, M is Mg, Ca, Y, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, N, P, S, F , One or more elements selected from Cl. When f = 2, b is 0 or more and 1 or less, c is 0 or more and 1 or less, d is 0 or more and 1 or less, e is 0 or more and 0.5 or less, and b, c, d, and e are b + c + d + e = 1. Fulfill. When f = 4, b is from 0 to 2, c is from 0 to 2, d is from 0 to 2, e is from 0 to 1, and b, c, d, and e satisfy b + c + d + e = 2. ]

σ is a value that balances charges, determined by the contents of Li, Ni, Co, Mn, and M, and the type of M, and σ is in the range of −0.2 to 0.2. For convenience, the value of σ is described as 0 in the present application.
The positive electrode active material of the present invention does not necessarily contain M, but can be contained for the purpose of improving various battery characteristics, or may be contained as an inevitable impurity.
When Ti is contained as M, the load characteristic is improved because the speed of deintercalation or intercalation of Li during charge / discharge is increased. When M is Mg or Al, the thermal stability is improved by stabilizing the crystal structure. In addition, there is an effect of promoting the diffusion and reaction of Li when synthesizing the positive electrode active material. When M is Zr or Hf, charging / discharging at a high potential becomes possible by stabilizing the crystal structure.

The positive electrode active material represented by the formula (1) is preferably Li _a CoO _{2 + σ} , Li _a Ni _0.8 Co _0.15 Al _0.05 O _{2 + σ} , Li _a Ni _0.8 Co _0.2 O _{2 + σ} , Li _a NiO _{2 + σ} , Li _a Mn ₂ O _{4 + σ} , Li _a Mn _0.5 Ni _0.5 O _{2 + σ} , Li _a Mn _1.5 Ni _0.5 O _{4 + σ} , or Li _a Mn _1/3 Ni _1/3 Co _{1 / 3} O _{2 + σ} .

In the positive electrode mixture of the present invention, positive electrode active material particles having a tap density of 2.0 g / cm ³ or more are used. By using such particles, the contact surface with the solid electrolyte increases, and the fluidity of the positive electrode active material particles increases, so that the porosity can be lowered when the positive electrode mixture is formed. The tap density is preferably 2.1 g / cm ³ or more, particularly preferably 2.15 g / cm ³ or more.
The tap density is a value measured by a method based on the 15th revised Japanese Pharmacopoeia. Specifically, the density of the positive electrode active material particles after tapping stroke of 30 mm and tapping 200 times (2 times / sec) is measured.

The positive electrode active material particles are preferably surface-modified with a lithium ion conductive oxide. When the surface-modified particles are used, the fluidity of the particles is improved, so that the tap density is improved. Therefore, when used for a battery, the performance of the battery is improved.
As a lithium ion conductive oxide which is a surface modifier, a lithium ion conductive oxide having no electronic conductivity is preferable. For example, lithium titanate _{(Li 4/3 Ti 5/3 O 4)} , crystalline oxide such as LiNbO ₃ and _{LiTaO 3, Li 2 O-SiO} 2 or the like of the amorphous-based (glass) oxide. In particular, Li _4/3 Ti _5/3 O ₄ is preferable.
When the surface-modified positive electrode active material particles are used, the tap density described above means the tap density of the surface-modified particles. The same applies to the particle size and the like described later.

The surface modification can be performed by referring to the following literature, for example.
N. Ohta, K .; Takada, L .; Zhang, R.A. Ma, M.M. Osada, T .; Sasaki, Adv. Mater. 18, 2226 (2005).

The particle diameter (secondary particle D50) of the positive electrode active material particles is 1 to 10 μm. The particle diameter is a value measured by a laser diffraction method.
The specific surface area is in the range of 0.1 to ³ m ² / g. The specific surface area is a value measured by the N ₂ adsorption BET method.

The positive electrode active material particles represented by the formula (1) and b = 0 include secondary particles and / or single crystal particles composed of a plurality of primary particles, and A defined by the following formula (2) is 1 It is preferable that it is 10 or less.
A = (m + p) / (m + s) (2)
(Where m is the number of single crystal particles, s is the number of secondary particles, and p is the number of primary particles constituting the secondary particles.)

A in the formula (2) represents the number of primary particles constituting the secondary particles in the positive electrode active material particles. When A is 1 or more and 10 or less, it can be said that the positive electrode active material particles are secondary particles in which primary particles grow and the surface properties are smooth. A is more preferably 2 or more and 8 or less m, p and s in the above formula (2) are obtained by embedding a plurality of the positive electrode active material particles with a resin and mirror-polishing the sample with a polarizing microscope. Can be measured. Specifically, 20 secondary particles and / or single crystal particles are randomly extracted from a polarizing microscope image (1000 times) of the sample. The number of secondary particles in the 20 particles is s, and the number of single crystal particles is m. Single crystal particles are single crystal particles whose grain boundaries cannot be confirmed by observation with the polarizing microscope described above.
The number p of primary particles can be determined by counting the number of primary particles partitioned by grain boundaries existing inside all the secondary particles observed above. Specifically, the total number of primary particles included in the cross section of secondary particles on the mirror-finished surface is defined as the number p of primary particles.

The positive electrode active material particles used in the present invention can be produced, for example, by uniformly mixing raw material particles such as cobalt oxide and lithium hydroxide and then firing them.
Firing may be pre-baked at a temperature lower than the target firing temperature (for example, 850 ° C. to 1050 ° C.), and then heated to the firing temperature, or after firing at the firing temperature,
The particle size, tap density, etc. of the positive electrode active material particles are determined depending on the starting material, for example, the concentration of the aqueous solution when synthesizing the raw material oxide or hydroxide, the concentration of the alkaline aqueous solution, the addition rate, pH, temperature, It is possible to control the firing conditions when synthesizing the positive electrode active material particles using the obtained raw materials, and the type of lithium salt used. The ratio of the constituent elements of the positive electrode active material particles can be controlled by adjusting the mixing ratio of the raw materials.

Examples of the sulfide-based solid electrolyte particles include those composed only of sulfur atoms, phosphorus atoms and lithium atoms, and those containing atoms such as Al, B, Si and Ge.
The raw material of the solid electrolyte particles, phosphorus pentasulfide and lithium sulfide _{(Li 2 S) (P 2} S 5), or lithium and elemental phosphorus and elemental sulfur sulfide, further lithium sulfide, phosphorus pentasulfide, elemental phosphorus and And / or elemental sulfur. P ₂ S ₃ , SiS ₂ , B ₂ S ₃ , Al ₂ S ₃ , Li ₃ PO ₄ , Li ₄ SiO _4, etc. may be used. Moreover, you may use the material which consists of an organic compound, an inorganic compound, or both organic and inorganic compounds.

The formulation of raw material, for example, when mixing with lithium phosphorus pentasulfide disulfide, the molar ratio is usually _{Li 2 S: P 2 S 5} = 50: 50~80: 20, _preferably, Li ₂ S: _P 2 S ₅ = 60: 40~75: 25. Particularly preferably, it is about Li ₂ S: P ₂ S ₅ = 70: 30.

After the above raw material is melt-reacted, it is cooled rapidly, or the raw material is treated by a mechanical milling method (MM method) to obtain a glassy solid electrolyte. Further, a crystalline solid electrolyte is obtained by heat treatment. From the viewpoint of ion conductivity, a crystalline solid electrolyte is preferable.
For a specific method for producing the solid electrolyte, for example, JP-A-2005-228570 may be referred to.

The particle size of the sulfide-based solid electrolyte particles is preferably 0.01 to 50 μm. More preferably, it is 0.1-10 micrometers. More preferably, it is 0.1-7 micrometers.
The particle diameter means an average value (D50) measured by a laser diffraction method.

  In the positive electrode mixture of the present invention, the mixing ratio of the positive electrode active material particles and the sulfide-based solid electrolyte particles (positive electrode active material: electrolyte “weight ratio”) is 95: 5 to 50:50.

In the present invention, the positive electrode active material particles have a particle size of 1 μm to 10 μm, the positive electrode active material particles have a specific surface area of 0.25 m ² / g to 0.8 m ² / g, and the sulfide-based solid electrolyte particles The particle size is preferably 0.01 to 50 μm.
The positive electrode active material particles preferably have a particle size of 4.2 μm or more and 7.0 μm or less, and the positive electrode active material particles have a specific surface area of 0.35 or more and 0.7 m ² / g or less.
The above conditions mean positive electrode active material particles having a smaller particle size than normal positive electrode active material particles.

The lithium battery of the present invention only needs to have a positive electrode made of the above-described positive electrode mixture of the present invention and an electrolyte layer containing a sulfide-based solid electrolyte, and other constituent members known in the art are used. it can.
FIG. 1 is a schematic cross-sectional view of a lithium battery according to an embodiment of the present invention.
The lithium battery 1 has a configuration in which an electrolyte layer 4 is sandwiched between a positive electrode 5 and a negative electrode 3. In the present embodiment, the positive electrode current collector 6 is in contact with the positive electrode 5, and the negative electrode current collector 2 is in contact with the negative electrode 3. In addition, the lithium battery which concerns on this invention is not limited to a secondary battery, A primary battery is also included.
Examples of each member will be shown below.

1. Negative electrode The negative electrode is not particularly limited as long as it can be used for a negative electrode of a normal battery.
For example, a negative electrode may be manufactured from a negative electrode mixture obtained by mixing a negative electrode active material and a solid electrolyte, or a carbon negative electrode may be used.

As a negative electrode active material, what is marketed can be used without limitation. For example, a carbon material, Sn metal, Si metal, Li metal, In metal, or the like can be suitably used. Specifically, natural graphite, various graphites, metal powder such as Sn, Si, Al, Sb, Zn, Bi, Sn ₅ Cu ₆ , Sn ₂ Co, Sn ₂ Fe, TiSi alloy, NiSi alloy, Li system Examples thereof include metal alloy powders such as alloys, metal oxides such as Si oxide, other amorphous alloys, and plating alloys. Although there is no restriction | limiting in particular regarding a particle size, A thing with an average particle diameter of several micrometers-80 micrometers can be used suitably.

There is no limitation in particular also about a solid electrolyte, For example, the solid electrolyte demonstrated by the positive electrode compound material of this invention can be used.
A negative electrode mixture is produced by mixing the negative electrode active material and the solid electrolyte at a predetermined ratio.
The negative electrode can be produced by a conventionally known method using the above negative electrode mixture.

2. Solid electrolyte There is no particular limitation, and those known in this technical field can be used, but the sulfide-based solid electrolyte used for the positive electrode mixture described above is preferred.

3. Positive electrode current collector and negative electrode current collector Examples of the positive electrode current collector and the negative electrode current collector include metals such as stainless steel, gold, platinum, zinc, nickel, tin, aluminum, molybdenum, niobium, tantalum, tungsten, and titanium. And, these alloys formed into a sheet, foil, net shape, punching metal shape, expanded metal shape or the like are used. In particular, an aluminum foil is preferable for the positive electrode current collector, and an aluminum foil or a tin foil is preferable for the negative electrode current collector in terms of current collection, workability, and cost.

  The method for producing the lithium battery is not particularly limited. For example, in the case of the lithium battery 1 shown in FIG. 1, a positive electrode mixture sheet in which the positive electrode 5 and the positive electrode current collector 6 are laminated, a negative electrode mixture sheet in which the negative electrode 3 and the negative electrode current collector 2 are laminated, and a solid electrolyte There is a method in which sheets (electrolyte layer 3) are respectively produced, and these are stacked and pressed.

  Further, the positive electrode 5 is formed on the positive electrode current collector 6, the electrolyte layer 4 is formed thereon, and the negative electrode 3 formed on the negative electrode current collector 2 is further formed on the positive electrode current collector 6. You may superimpose so that it touches.

  As a method for producing the positive electrode mixture sheet and the negative electrode mixture sheet, for example, the positive electrode 5 and the negative electrode 3 can be formed in a film shape on at least a part of the positive electrode current collector 6 and the negative electrode current collector 2. Examples of the film forming method include a blast method, an aerosol deposition method, a cold spray method, a sputtering method, a vapor deposition method, and a thermal spraying method.

  In addition, the positive electrode 5 and the negative electrode 3 are made into a slurry by applying the positive electrode 5 and the negative electrode 3 to the positive electrode current collector 6 and the negative electrode current collector 2, and the positive electrode 5 and the negative electrode 3. There is also a method of stacking on the electric body 2 and compressing.

Example 1
(1) Production of LiCoO ₂ Particles Cobalt oxide having a particle diameter of 5 μm (D50) and lithium hydroxide were uniformly mixed, then fired at 700 ° C. for 4 hours, and then fired at 950 ° C. for 5 hours. Composition analysis of the obtained oxide particles by ICP revealed LiCoO ₂ particles having a Li / Co ratio of 0.99: 1.00.
LiCoO ₂ particles, N. Ohta, K .; Takada, L .; Zhang, R.A. Ma, M.M. Osada, T .; Sasaki, Adv. Mater. 18, 2226 (2005). The surface was modified with Li _4/3 Ti _5/3 O ₄ by the method described in 1).

The particle diameter of the surface-modified LiCoO ₂ was 5.19 μm (D50), and the BET surface area was 0.66 m ² / g. The measuring method is as follows.
(A) Particle diameter It measured with the laser diffraction type particle size distribution measuring apparatus (the Sysmex company make, Mastersizer 2000).
(B) Specific surface area (BET surface area)
The sample was deaerated at 200 ° C. for 20 minutes and then measured by the N ₂ adsorption BET method using a trade name “NOVA2000” manufactured by Cantachrome.

(2) Preparation of sulfide-based solid electrolyte particles 0.6508 g (0.01417 mol) of high purity lithium sulfide and 1.3492 g (0.00607 mol) of diphosphorus pentasulfide are mixed well, and the mixed powder is put into an alumina pot. Completely sealed.
The pot charged with the mixed powder was attached to a planetary ball mill, and milling was performed for several minutes at a low speed (85 rpm) for the purpose of thoroughly mixing the starting materials. Thereafter, the rotational speed was gradually increased to 370 rpm, and mechanical milling was further performed for 20 hours.
It was confirmed by X-ray measurement that the obtained powder was vitrified. This powder was heat-treated at 300 ° C. for 2 hours to obtain a sulfide-based solid electrolyte.

When the ionic conductivity of the obtained sulfide-based solid electrolyte was measured by an AC impedance method (measurement frequency: 100 Hz to 15 MHz), it showed an ionic conductivity of 1.0 × 10 ⁻³ S / cm at room temperature.
The particle diameter of the sulfide-based solid electrolyte particles was 5 μm.

(3) Preparation of positive electrode mixture The LiCoO ₂ particles (positive electrode active material) prepared in (1) above and the sulfide solid electrolyte prepared in (2) were mixed so that the sulfide solid electrolyte would be 30 wt%. And it was set as the positive electrode compound material.

(4) Manufacture of lithium battery 50 mg of the sulfide-based solid electrolyte prepared in (2) above is put into a plastic cylinder having a diameter of 10 mm, and pressure-molded at 1.7 t / cm ² to form a solid electrolyte layer. did.
Subsequently, 30 mg of the positive electrode mixture prepared in (3) above was charged into the cylinder on which the solid electrolyte layer was formed, and press-molded at 5 t / cm ² to form a laminate of the solid electrolyte layer and the positive electrode.
Next, an indium foil (thickness 0.1 mm, 9 mmφ) was formed on the solid electrolyte layer surface of the laminate, and a lithium battery having a three-layer structure of a positive electrode, a solid electrolyte layer, and a negative electrode was produced.

The produced lithium battery was charged to 3.9 V at 500 μA per cm ² , and then discharged at a discharge current density of 10 mA / cm ² to evaluate the discharge capacity and the discharge voltage. The results are shown in Table 1.

Example 2
A positive electrode mixture was prepared in the same manner as in Example 1 except that LiCoO ₂ particles obtained by the following production method were used, and a lithium battery was produced and evaluated. The surface is not modified. The results are shown in Table 1.

[Production of LiCoO ₂ particles]
Cobalt oxide having a particle size of 7 μm (D50) and lithium carbonate were uniformly mixed, then fired at 700 ° C. for 4 hours, and then fired at 1000 ° C. for 5 hours. Composition analysis of the obtained oxide particles by ICP revealed LiCoO ₂ particles having a Li: Co ratio of 1.01: 1.00. The obtained LiCoO _{2 had} a particle size of 7.00 μm (D50) and a BET surface area of 0.46 m ² / g.

Example 3
The LiCoO ₂ particles obtained in Example 2 were surface modified in the same manner as in Example 1. The particle diameter of the surface-modified LiCoO ₂ was 7.20 μm (D50), and the BET surface area was 0.44 m ² / g. A positive electrode mixture was prepared in the same manner as in Example 1 except that these LiCoO ₂ particles were used, and a lithium battery was produced and evaluated. The results are shown in Table 1.

Example 4
A lithium battery was prepared and evaluated in the same manner as in Example 1 except that a negative electrode composed of the following negative electrode mixture was formed instead of the indium foil. The results are shown in Table 1.
[Negative electrode mixture]
Graphite (particle size: 25 μm in D50) and the sulfide-based solid electrolyte particles prepared in (2) of Example 1 were mixed so that graphite: sulfide-based solid electrolyte particles = 6: 4 (weight ratio). The negative electrode composite was used.
A lithium battery was produced in the same manner as in Example 1 except that 8.8 mg of this negative electrode mixture was used and 14.4 mg of the positive electrode mixture of Example 1 was used.
Incidentally, the negative electrode negative electrode mixture was poured into a plastic cylinder was formed by compression molding at 1.7t / cm ^2.
50 mg of a sulfide-based solid electrolyte was put on the negative electrode and pressure-molded at 3.4 t / cm ² to form a solid electrolyte layer.
Subsequently, 30 mg of the positive electrode mixture was put into a cylinder on which the solid electrolyte layer was formed, and was pressure-molded at 5 t / cm ² .

Example 5
A lithium battery was prepared and evaluated in the same manner as in Example 4 except that 14.4 mg of the positive electrode mixture of Example 3 was used to form the positive electrode. The results are shown in Table 1.

Example 6
Preparation of Li _X (Ni _0.85 Co _0.15 ) O ₂ (X = 1.03) Particles After dissolving metallic nickel in 85 g and metallic cobalt in 15 g nitric acid, it was diluted with pure water to 1650 ml. Subsequently, 820 ml of 4N sodium hydroxide solution was added and stirred, followed by filtration to obtain a hydroxide cake. The obtained cake was dried at 100 ° C. for 10 hours to obtain 166 g of nickel cobalt composite hydroxide. Here, lithium hydroxide monohydrate (LiOH.H ₂ O) was added to and mixed with nickel-cobalt composite hydroxide so that Li / (Ni + Co) = 1.03, and calcined at 800 ° C., Li _X (Ni _0.85 Co _0.15 ) O ₂ (X = 1.03) was synthesized. The obtained Li _X (Ni _0.85 Co _0.15 ) O _{2 had} a particle size of 9.28 μm (D50) and a BET surface area of 0.24 m ² / g. A positive electrode mixture was prepared in the same manner as in Example 1 except that the positive electrode active material was used, and a lithium battery was produced.
The produced lithium battery was charged to 3.6 V at 500 μA per cm ² and then discharged at a discharge current density of 10 mA / cm ² to evaluate the discharge capacity and the discharge voltage. The results are shown in Table 1.

Example 7
Preparation of Li _X (Ni _0.82 Co _0.14 Al _0.04 ) O ₂ (X = 1.03) Particles After dissolving metallic nickel in 85 g and metallic cobalt in 15 g nitric acid, it was diluted with pure water to 1650 ml It was. Subsequently, 820 ml of 4N sodium hydroxide solution and 40 ml of 1 mol / l aluminum nitrate solution were added and stirred, followed by filtration to obtain a hydroxide cake. The obtained cake was dried at 100 ° C. for 10 hours to obtain 168 g of nickel cobalt composite hydroxide. Here, lithium hydroxide monohydrate (LiOH.H ₂ O) was added and mixed so that Li / (Ni + Co + Al) = 1.03, followed by firing at 800 ° C., and Li _X (Ni _0.82 Co _0.14 Al _0.04 ) O ₂ (X = 1.03) was synthesized. The resulting Li _{X (Ni} 0.85 _{Co 0.15)} particle size of the _{O 2} is 9.10μm (D50), BET surface area was 0.25 m ² / g. A positive electrode mixture was prepared in the same manner as in Example 8 except that the positive electrode active material was used, and a lithium battery was prepared and evaluated. The results are shown in Table 1.

Comparative Example 1
Except using LiCoO ₂ particles obtained in the following method in the same manner as in Example 1 to prepare a positive electrode mix was prepared a lithium battery. The results are shown in Table 1.
[Production of LiCoO ₂ particles]
Cobalt oxide having a particle size of 13 μm (D50) and lithium carbonate were uniformly mixed, then fired at 700 ° C. for 4 hours, and then fired at 750 ° C. for 5 hours. Composition analysis of the obtained oxide particles by ICP revealed LiCoO ₂ particles having a Li / Co ratio of 0.99: 1.00. The obtained LiCoO _{2 had} a particle size of 12.50 μm (D50) and a BET surface area of 0.85 m ² / g.

Comparative Example 2
A positive electrode mixture was prepared in the same manner as in Example 1 except that LiCoO ₂ particles (manufactured by Nippon Chemical Industry Co., Ltd., cell seed C-10) were used, and those without surface modification were used, and a lithium battery was produced and evaluated. . The results are shown in Table 1.

Comparative Example 3
A positive electrode mixture was prepared in the same manner as in Example 4 except that the same LiCoO ₂ particles as in Comparative Example 1 were used, and a lithium battery was produced and evaluated. The results are shown in Table 1.

Comparative Example 4
A positive electrode mixture was prepared in the same manner as in Example 4 except that the same LiCoO ₂ particles as in Comparative Example 2 were used, and a lithium battery was prepared and evaluated. The results are shown in Table 1.

Comparative Example 5
When using the same LiCoO ₂ particles as in Comparative Example 2 to produce a battery, a positive electrode mixture was prepared in the same manner as in Example 1 except that the final molding pressure was 7 t / cm ² to produce a lithium battery. And evaluated. The results are shown in Table 1.
As shown in Table 1, since the batteries produced in Comparative Examples 1 to 4 did not function as batteries, the pressure during molding was increased in this example. However, this example did not function as a battery.

  The positive electrode mixture of the present invention is suitable as a positive electrode material for a lithium battery. The lithium battery of the present invention can be suitably used as a power source for various electrical appliances.

DESCRIPTION OF SYMBOLS 1 Lithium battery 2 Negative electrode collector 3 Negative electrode 4 Electrolyte layer 5 Positive electrode 6 Positive electrode collector

Claims (7)

Including positive electrode active material particles represented by the following formula (1) and sulfide-based solid electrolyte particles;
A positive electrode composite material, wherein the tap density of the particles represented by the formula (1) is 2.0 g / cm ³ or more.
Li _a Ni _b Co _c Mn _{d Me} O _{f + σ} (1)
[In Formula (1), a is larger than 0.9 and 1.05 or less, f is 2 or 4, σ is −0.2 or more and 0.2 or less, M is Mg, Ca, Y, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, N, P, S, F And at least one element selected from Cl. When f = 2, b is 0 or more and 1 or less, c is 0 or more and 1 or less, d is 0 or more and 1 or less, e is 0 or more and 0.5 or less, and b, c, d, and e are b + c + d + e = 1. Fulfill. When f = 4, b is from 0 to 2, c is from 0 to 2, d is from 0 to 2, e is from 0 to 1, and b, c, d, and e satisfy b + c + d + e = 2. ]   The positive electrode composite material according to claim 1, wherein the particles of the positive electrode active material represented by the formula (1) are surface-modified with a lithium ion conductive oxide. Formula (1) particle size of the particles of the positive electrode active material represented by is at 1μm or more 10μm or less and a specific surface area of not more than 0.20 m ² / g or more 0.8 m ² / g,
3. The positive electrode mixture according to claim 1, wherein a particle diameter of the sulfide-based solid electrolyte particles is 0.01 μm or more and 50 μm or less. The positive electrode active material particles represented by the formula (1) have a particle size of 4.2 μm or more and 7.0 μm or less, and a specific surface area of 0.35 or more and 0.7 m ² / g or less. The positive electrode composite material according to claim 1 or 2, wherein The positive electrode active material particles represented by the formula (1) and b = 0 include secondary particles and / or single crystal particles composed of a plurality of primary particles, and are defined by the following formula (2). 1 or more and 10 or less, The positive electrode compound material as described in any one of Claims 1-4 characterized by the above-mentioned.
A = (m + p) / (m + s) (2)
(Where m is the number of single crystal particles, s is the number of secondary particles, and p is the number of primary particles constituting the secondary particles.) Positive electrode according to any one of claims 1 to 4, the positive electrode active material represented by the formula (1) is characterized in that it is a Li a _CoO 2 + _σ. A positive electrode comprising the positive electrode mixture according to any one of claims 1 to 6,
A lithium battery comprising an electrolyte layer containing a sulfide-based solid electrolyte.

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