Anode mixture and solid state battery

Abstract

A main object of the present disclosure is to provide an anode mixture capable of obtaining an anode layer in which a volume change due to charge and discharge is inhibited.SOLUTION: The present disclosure provides a negative electrode mixture containing a negative electrode active material and a solid electrolyte, wherein the negative electrode mixture contains, as the negative electrode active material, a secondary particle in which a plurality of primary particles are aggregated, the primary particle is a Si-based active material containing a Si element, a particle size D50 of the secondary particle is 2.5 μm or more and less than 20 μ m, and a particle size D50 of the solid electrolyte is 0.005 μm or more and less than 2.0 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a negative electrode mixture and a solid-state battery. [Background technology]

[0002] In recent years, the development of batteries has been actively pursued. For example, in the automotive industry, development of batteries for use in electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs) is progressing. A battery typically has a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer. Also, an active material containing Si element (Si-based active material) is known as a negative electrode active material used in the negative electrode layer. For example, Patent Document 1 discloses a negative electrode for a secondary battery containing composite particles including a plurality of porous silicon particles and a binder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-017797 Summary of the Invention [Problem to be solved by the invention]

[0004] Although Si-based active materials are high-capacity active materials, they undergo large volume changes during charge and discharge. Large volume changes during charge and discharge can easily cause cracks in the negative electrode layer, which can lead to performance degradation (e.g., increased resistance and decreased cycle characteristics) of the negative electrode layer. Therefore, there is a need to suppress volume changes during charge and discharge in negative electrode layers containing Si-based active materials.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a negative electrode mixture that makes it possible to obtain a negative electrode layer that is suppressed from undergoing volumetric change due to charge and discharge. [Means for solving the problem]

[0006] [1] A negative electrode mixture containing a negative electrode active material and a solid electrolyte, the negative electrode mixture contains, as the negative electrode active material, secondary particles formed by aggregation of a plurality of primary particles, the primary particles are Si-based active materials containing Si elements, The particle diameter D of the above secondary particles 50 is 2.5 μm or more and less than 20 μm, The particle diameter D of the above solid electrolyte 50 The negative electrode mixture has a particle size of 0.05 μm or more and less than 2.0 μm.

[0007] [2] The particle diameter D of the secondary particles 50 is 5.0 μm or more and 15 μm or less, The particle diameter D of the solid electrolyte 50 The negative electrode mixture according to [1], wherein the average particle size is 0.1 μm or more and 1.0 μm or less.

[0008] [3] The particle diameter D of the above primary particles 50 The negative electrode mixture according to [1] or [2], wherein the average particle size is 0.3 μm or more and 3.0 μm or less.

[0009] [4] The particle diameter D of the above primary particles 50 The negative electrode mixture according to any one of [1] to [3], wherein the average particle size is 0.5 μm or more and 2.5 μm or less.

[0010] [5] The negative electrode mixture according to any one of [1] to [4], wherein the primary particles are porous particles.

[0011] [6] The particle diameter D of the secondary particles 50 The particle diameter D of the solid electrolyte 50 The negative electrode mixture according to any one of [1] to [5], wherein the ratio of is 0.5% or more and 15% or less.

[0012] [7] The negative electrode mixture according to any one of [1] to [6], wherein the secondary particles are particles formed by aggregating the plurality of primary particles with a binder.

[0013] [8] The negative electrode mixture according to any one of [1] to [7], wherein the solid electrolyte is a sulfide solid electrolyte.

[0014] [9] The negative electrode composite according to [8], wherein the sulfide solid electrolyte contains Li, P, and S elements.

[0015]

[10] A solid-state battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer and containing a solid electrolyte, The solid-state battery, wherein the negative electrode layer contains the negative electrode mixture according to any one of [1] to [9]. [Effects of the Invention]

[0016] The negative electrode mixture according to the present disclosure has the effect of being able to obtain a negative electrode layer that is suppressed from undergoing volumetric change due to charge and discharge. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a solid-state battery according to the present disclosure. [Figure 2] 1 is a graph showing the results of confining pressure fluctuation and resistance in the solid state batteries produced in Examples 1 to 4 and Comparative Example 1. [Figure 3] 1 is a graph showing the results of confining pressure fluctuation and resistance in the solid state batteries produced in Examples 5 to 8 and Comparative Example 2. [Figure 4] 10 is a graph showing the results of confining pressure fluctuation and resistance in the solid state batteries produced in Examples 9 to 14. DETAILED DESCRIPTION OF THE INVENTION

[0018] The negative electrode mixture and solid state battery according to the present disclosure will be described in detail below.

[0019] A. Negative electrode mixture The negative electrode composite in the present disclosure contains a negative electrode active material and a solid electrolyte. The negative electrode composite also contains secondary particles formed by agglomeration of a plurality of primary particles as the negative electrode active material. The primary particles are Si-based active materials containing Si element. The particle diameter D of the secondary particles is 50 and the particle diameter D of the solid electrolyte 50 is within a certain range.

[0020] According to the present disclosure, the negative electrode active material contains secondary particles formed by agglomeration of a plurality of primary particles (Si-based active material), and the particle diameter D of the secondary particles is 50 and the particle diameter D of the solid electrolyte 50 Since the content of the active material is within a specific range, it is possible to obtain a negative electrode composite that can suppress volume changes during charging and discharging. As described above, while Si-based active materials are high-capacity active materials, they also undergo large volume changes during charging and discharging. If the volume changes during charging and discharging are large, cracks are likely to occur in the negative electrode layer, and if cracks occur, performance degradation of the negative electrode layer (e.g., increased resistance, decreased cycle characteristics) is likely to occur. Therefore, there is a demand for suppression of volume changes during charging and discharging in negative electrode layers containing Si-based active materials.

[0021] Therefore, the present inventors investigated a method of agglomerating multiple primary particles (Si-based active materials) to form secondary particles (composite particles). Such secondary particles have voids between the primary particles. The voids can absorb the volumetric changes of the primary particles and reduce the volumetric changes of the secondary particles due to charging and discharging, thereby reducing the volumetric changes of the negative electrode layer due to charging and discharging.

[0022] The present inventors have conducted extensive research into the suppression of volumetric changes in the negative electrode layer due to charging and discharging, and have found that the degree of volumetric changes in the negative electrode layer due to charging and discharging is basically determined by the particle diameter D of the secondary particles. 50 However, surprisingly, the particle diameter of the secondary particles D 50 In addition, the particle diameter D of the solid electrolyte 50Therefore, we have obtained new knowledge that the particle diameter D of the secondary particles is also greatly affected by 50 and the particle diameter D of the solid electrolyte 50 It was found that by keeping the particle diameter D of the secondary particles within a specific range, the volume change of the negative electrode layer due to charging and discharging can be effectively suppressed. 50 and the particle diameter D of the solid electrolyte 50 It has been found that by setting the resistance of the negative electrode layer within a specific range described later, it is possible to reduce the resistance of the negative electrode layer and improve the cycle characteristics.

[0023] 1.Negative electrode active material The negative electrode mixture contains a negative electrode active material. The negative electrode active material contains secondary particles formed by aggregation of a plurality of primary particles. The particle diameter D of the secondary particles 50 The particle diameter D of the secondary particles is usually 2.5 μm or more and less than 20 μm. 50 The particle diameter D of the secondary particles may be 3.0 μm or more, or 5.0 μm or more. 50 If is too small, the volume change of secondary particles due to charging and discharging may not be reduced sufficiently. 50 The particle diameter D of the secondary particles may be 19 μm or less, 17 μm or less, or 15 μm or less. 50 If the particle diameter D is too large, the resistance of the negative electrode layer may not be reduced sufficiently. 50 is the cumulative 50% particle size in the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer.

[0024] (1) Primary particles The primary particles in the present disclosure are Si-based active materials containing elemental Si. Examples of Si-based active materials include simple Si, Si alloys, Si oxides, Si carbides, and Si oxide carbides (silicon oxycarbides). Si alloys are alloys whose main component is Si. Examples of metals other than Si in Si alloys include at least one of W, Mo, Cr, V, Nb, Fe, Ti, Zr, Hf, and Os. Examples of Si oxides include SiO. The Si-based active material may have a diamond-type crystalline phase as the main phase, a clathrate I-type crystalline phase as the main phase, or a clathrate II-type crystalline phase as the main phase.

[0025] The primary particles in the present disclosure may be solid particles or porous particles, but the latter are preferred. Porous particles have voids inside, which can absorb volume changes of the particles and, as a result, can reduce volume changes of the negative electrode layer due to charge and discharge.

[0026] The porosity of the porous particles is, for example, 4% or more, and may be 10% or more. On the other hand, the porosity of the porous particles is, for example, 40% or less, and may be 20% or less. The porosity can be determined by the following procedure. First, a cross section of an electrode layer containing an active material is prepared by ion milling. The cross section is then observed with a scanning electron microscope (SEM) to obtain a photograph of the particles. From the obtained photograph, the silicon portion and the void portion are clearly distinguished using image analysis software and binarized. The areas of the silicon portion and the void portion are determined, and the porosity (%) is calculated using the following formula: Porosity (%) = (void area) / ((silicon area) + (void area)) × 100

[0027] The porous particles preferably have many minute voids with a pore diameter of 100 nm or less. Pores with a pore diameter of 100 nm or less can be prevented from collapsing due to pressing, compared to pores with a pore diameter greater than 100 nm. The void volume X (cumulative pore volume) of pores with a pore diameter of 100 nm or less is, for example, 0.05 cc / g or more, or may be 0.10 cc / g or more, or may be 0.12 cc / g or more. On the other hand, the void volume X is, for example, 0.40 cc / g or less. The void volume in the present disclosure can be determined, for example, by BET measurement.

[0028] The porous particles preferably have many minute voids with a pore diameter of 50 nm or less. Pores with a pore diameter of 50 nm or less can be more effectively prevented from collapsing due to pressing than voids with a pore diameter greater than 50 nm and a pore diameter of 100 nm or less. The void volume Y of voids with a pore diameter of 50 nm or less is, for example, 0.05 cc / g or more, or may be 0.075 cc / g or more, or may be 0.10 cc / g or more. On the other hand, the void volume Y is, for example, 0.25 cc / g or less.

[0029] The porous particles preferably have many minute voids with a pore diameter of 10 nm or less. Pores with a pore diameter of 10 nm or less can accommodate precipitated Li at a higher filling rate than voids with a pore diameter greater than 10 nm, thereby suppressing volume changes due to charge and discharge. The void volume Z of voids with a pore diameter of 10 nm or less is, for example, 0.015 cc / g or more, or may be 0.02 cc / g or more, or even 0.03 cc / g or more. On the other hand, the void volume Z is, for example, 0.09 cc / g or less.

[0030] One example of a method for forming porous particles is to react metallic Li with solid primary particles (Si-based active material) to produce a LiSi alloy, and then remove Li from the LiSi alloy. The LiSi alloy can be obtained, for example, by mixing the primary particles (Si-based active material) with metallic Li. The molar ratio of Li to Si (Li / Si) is, for example, 1.0 or more, or may be 2.0 or more, 3.0 or more, or even 4.0 or more. Meanwhile, Li / Si is, for example, 8.0 or less. One example of a method for removing Li from a LiSi alloy is to react the LiSi alloy with a Li extractant. Examples of Li extractants include alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; and acids such as acetic acid, formic acid, propionic acid, and oxalic acid.

[0031] Another example of a method for forming porous particles is to react metallic Mg with solid primary particles (Si-based active material) to produce an MgSi alloy, and then remove the Mg from the MgSi alloy. The MgSi alloy can be obtained, for example, by heating a mixture of the primary particles (Si-based active material) and metallic Mg. The ratio of Mg to Si (Mg / Si) is, for example, 1.0 or more, or may be 1.5 or more, or even 2.0 or more. Meanwhile, the Mg / Si ratio is, for example, 6.0 or less. An example of a method for removing Mg from an MgSi alloy is to heat the MgSi alloy in an oxygen-containing inert gas atmosphere to convert the Mg in the Mg-Si alloy to MgO, and then remove the MgO with an acid solution. An example of the acid solution is an aqueous solution containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0032] Primary particle diameter D 50 is not particularly limited, but may be, for example, 0.3 μm or more, or 0.5 μm or more. 50 For example, the particle diameter D is 3.0 μm or less, and may be 2.5 μm or less.10 The cumulative 90% particle diameter is the particle diameter D 90 (D 90 -D 10 ) / D 50 means the spread of the distribution, and (D 90 -D 10 ) / D 50 The smaller the value of (D 90 -D 10 ) / D 50 is not particularly limited, but may be, for example, 0.1 or more and 3.0 or less, or 0.3 or more and 2.0 or less.

[0033] The BET specific surface area of ​​the primary particles is not particularly limited, but is, for example, 1 m 2 / g or more, and 10m 2 / g or more, 2 / g or more, and 2 On the other hand, the BET specific surface area of ​​the primary particles may be, for example, 200 m 2 / g or less, and 150m 2 / g or less.

[0034] (2) Secondary particles Secondary particles are particles formed by agglomeration of a plurality of primary particles. Secondary particles are, for example, particles formed by agglomeration of a plurality of primary particles with a binder. Examples of binders include rubber-based binders such as butadiene rubber (BR) and styrene butadiene rubber (SBR), and fluoride-based binders such as polyvinylidene fluoride (PVdF). In the secondary particles, the ratio of the binder to the total of the plurality of primary particles and the binder is, for example, 1% by mass or more and 30% by mass or less, and may be 5% by mass or more and 25% by mass or less. On the other hand, the secondary particles may be a sintered body formed by agglomeration of a plurality of primary particles. In addition, in the secondary particles, (D 90 -D 10 ) / D 50 is not particularly limited, but may be, for example, 0.1 or more and 5.0 or less, or 0.3 or more and 1.0 or less.

[0035] The method for forming secondary particles is not particularly limited, but examples thereof include spray drying. In the spray drying method, a slurry containing a plurality of primary particles, a binder, and a dispersion medium is sprayed into hot air to dry. When forming secondary particles containing porous particles as primary particles, primary particles that are porous may be prepared first, and then the secondary particles may be formed using the primary particles. Alternatively, primary particles that are solid particles may be prepared first, and then the secondary particles may be formed using the primary particles, and then the primary particles that make up the secondary particles may be made porous.

[0036] 2.Solid electrolyte The negative electrode mixture contains a solid electrolyte. In the present disclosure, the particle diameter D 50 is usually 0.05 μm or more and less than 2.0 μm. 50 On the other hand, the particle diameter D of the solid electrolyte may be 0.1 μm or more, 0.2 μm or more, or 0.3 μm or more. 50 The particle diameter D of the solid electrolyte may be 1.8 μm or less, 1.5 μm or less, 1.2 μm or less, or 1.0 μm or less. 50 If the value is too small or too large, the volume change of the negative electrode layer due to charging and discharging may not be sufficiently suppressed.

[0037] In addition, the particle diameter of the secondary particles D 50 Solid electrolyte particle diameter D 50 The ratio (SE / Si2) is not particularly limited, but may be, for example, 0.5% or more, 1.0% or more, 1.2% or more, or 1.5% or more. On the other hand, the ratio (SE / Si2) is, for example, 15% or less, 12% or less, 10% or less, or 5% or less.

[0038] Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, halide solid electrolytes, and other solid electrolytes.

[0039] A sulfide solid electrolyte is a solid electrolyte containing sulfur element (S element) as the main component of the anion element. Examples of the sulfide solid electrolyte include a solid electrolyte containing Li element, X element (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S element. The sulfide solid electrolyte may contain one kind of element or two or more kinds of elements as the X element. The sulfide solid electrolyte preferably contains P element as the X element. The sulfide solid electrolyte may further contain at least one of O element and halogen element. Examples of the halogen element include F element, Cl element, Br element, and I element.

[0040] The sulfide solid electrolyte may be glass (amorphous), glass-ceramics, or crystalline. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include Thio-LISICON type crystalline phase, argyrodite type crystalline phase, and LGPS type crystalline phase.

[0041] The composition of the sulfide solid electrolyte is not particularly limited. For example, xLi2S·(1-x)P2S5 (0.5≦x<1), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.5≦x<1, 0≦y≦30, 0≦z≦30) can be mentioned. In these compositions, x preferably satisfies 0.7≦x≦0.8. Also, as other examples of the composition of the sulfide solid electrolyte, Li 7-x PS 6-x X X can be mentioned. X is at least one of F, Cl, Br, I, and x satisfies 0≦x≦2. Also, as other examples of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0<x<1) can be mentioned. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0042] The oxide solid electrolyte is a solid electrolyte containing oxygen as the main anion element, the nitride solid electrolyte is a solid electrolyte containing nitrogen as the main anion element, and the halide solid electrolyte is a solid electrolyte containing halogen as the main anion element. Any known solid electrolyte can be used as these solid electrolytes. The solid content of the solid electrolyte in the negative electrode composite is, for example, 10% by mass or more and 50% by mass or less, or may be 20% by mass or more and 40% by mass or less.

[0043] 3.Negative electrode composite material The negative electrode mixture may further contain a conductive material. Examples of the conductive material include carbon-based conductive materials and metal-based conductive materials. Examples of the carbon-based conductive material include particulate carbon-based conductive materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon-based conductive materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF). The fibrous carbon-based conductive material is preferably a carbon nanotube (CNT) such as a single-walled carbon nanotube (SWCNT) or a multi-walled carbon nanotube (MWCNT). When the conductive material is particulate, the particle diameter D of the conductive material is 50 is not particularly limited, but is, for example, 10 nm to 10 μm, or alternatively, 20 nm to 1 μm, or 30 nm to 500 nm. The solid content ratio of the conductive material in the negative electrode mixture is, for example, 0.05 mass % to 3 mass %.

[0044] The negative electrode mixture may further contain a binder (second binder) that does not form secondary particles, in addition to the binder (first binder) that forms the secondary particles. The type of the second binder is the same as that described for the first binder. The solid content of the second binder in the negative electrode mixture is, for example, 0.1 mass % or more and 5 mass % or less.

[0045] The negative electrode mixture may or may not further contain a dispersion medium. Examples of the dispersion medium include butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, and N-methyl-2-pyrrolidone (NMP). When the negative electrode mixture contains a dispersion medium, the solid content of the negative electrode mixture is, for example, 20% by mass or more and 80% by mass or less. Furthermore, the negative electrode mixture is generally used in batteries, and is preferably used in solid-state batteries.

[0046] B. Solid state battery Fig. 1 is a schematic cross-sectional view illustrating a solid-state battery according to the present disclosure. The solid-state battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 containing a solid electrolyte and disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. In the present disclosure, the negative electrode layer 2 contains the negative electrode composite described above in "A. Negative electrode composite."

[0047] According to the present disclosure, by using the above-described negative electrode composite, a solid-state battery in which volume change due to charging and discharging is suppressed is obtained.

[0048] 1. Negative electrode layer The negative electrode layer contains the above-mentioned negative electrode composite. The negative electrode composite is the same as that described above in "A. Negative Electrode Composite." The thickness of the negative electrode layer is, for example, 0.1 μm or more and 500 μm or less, or may be 0.1 μm or more and 100 μm or less, or may be 0.1 μm or more and 50 μm or less. In addition, as a method for forming the negative electrode layer, for example, a method in which a negative electrode composite containing a dispersion medium is applied to a negative electrode current collector and then dried can be mentioned.

[0049] 2. Positive electrode layer The positive electrode layer usually contains a positive electrode mixture, which contains at least a positive electrode active material and may further contain at least one of a solid electrolyte, a conductive material, and a binder.

[0050] Examples of the positive electrode active material include oxide active materials, such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0051] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. This is because it can suppress the reaction between the oxide active material and the solid electrolyte (especially the sulfide solid electrolyte). An example of the Li-ion conductive oxide is LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less.

[0052] The solid electrolyte, conductive material, and binder used in the positive electrode composite are the same as those described above in "A. Negative Electrode Composite." The thickness of the positive electrode layer is, for example, 0.1 μm to 500 μm, or may be 0.1 μm to 100 μm, or may be 0.1 μm to 50 μm. The positive electrode layer may be formed, for example, by applying a positive electrode composite containing a dispersion medium to a positive electrode current collector and drying the applied coating.

[0053] 3. Electrolyte layer The electrolyte layer is formed between the positive electrode layer and the negative electrode layer and contains a solid electrolyte. The electrolyte layer may further contain a binder. The solid electrolyte and the binder are the same as those described above in "A. Negative Electrode Composite." The thickness of the electrolyte layer is, for example, 0.1 μm to 500 μm, or may be 0.1 μm to 100 μm, or may be 0.1 μm to 50 μm.

[0054] 4. Other configurations The solid-state battery according to the present disclosure preferably includes a positive electrode current collector that collects current from the positive electrode layer and a negative electrode current collector that collects current from the negative electrode layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. Examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon.

[0055] The solid-state battery according to the present disclosure may further include a constraining jig that applies a constraining pressure to the positive electrode layer, the electrolyte layer, and the negative electrode layer in the thickness direction. The constraining pressure is, for example, 0.1 MPa or more, or may be 1 MPa or more, or may be 5 MPa or more. On the other hand, the constraining pressure is, for example, 100 MPa or less, or may be 50 MPa or less, or may be 20 MPa or less.

[0056] 5. Solid state battery The type of solid-state battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. The solid-state battery in the present disclosure may be a primary battery or a secondary battery, with secondary batteries being preferred. This is because they can be repeatedly charged and discharged and are useful, for example, as automotive batteries. The solid-state battery may be a semi-solid battery or an all-solid battery.

[0057] Examples of uses of solid-state batteries include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, solid-state batteries are preferably used as driving power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). Solid-state batteries may also be used as power sources for mobile objects other than vehicles (for example, trains, ships, and aircraft), or as power sources for electrical appliances such as information processing devices. There are no particular limitations on the method for producing solid-state batteries, and known methods can be used.

[0058] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0059] [Example 1] (Preparation of primary particles) 0.65 g of Si particles (Kojundo Chemical) and 0.60 g of Li metal (Honjo Metal) were mixed in an agate mortar under an Ar atmosphere to obtain a LiSi precursor. In a glass reactor under an Ar atmosphere, 1.0 g of LiSi precursor and 125 ml of a dispersion medium (1,3,5-trimethylbenzene, Nacalai Tesque) were mixed using an ultrasonic homogenizer (UH-50, SMT). The resulting LiSi precursor dispersion was cooled to 0°C, and 125 ml of ethanol (Nacalai Tesque) as a Li extraction solvent was added dropwise. The reaction was continued for 120 minutes. After the reaction, 50 ml of acetic acid (Nacalai Tesque) was added dropwise and the reaction continued for 60 minutes. After the reaction, the liquid and solid reactants were separated by suction filtration. The resulting solid reactant was vacuum dried at 120°C for 2 hours to recover porous primary particles (nanoporous Si). The recovered primary particles are classified and the particle diameter D 50 was adjusted to 1.5 μm.

[0060] (Creation of secondary particles) The obtained primary particles (nanoporous Si) and a PVDF-HFP binder (manufactured by Kureha) were dispersed and partially dissolved in dimethyl carbonate (manufactured by Nacalai Tesque) so that the ratio (mass ratio) of primary particles to binder was 100:13.3. This slurry was sprayed into a spray dryer in a nitrogen gas atmosphere at 140°C and dried to obtain secondary particles in which multiple primary particles were aggregated. The obtained secondary particles were classified to determine the particle diameter D of the secondary particles. 50 was adjusted to 2.5 μm.

[0061] (Production of negative electrode layer) The resulting secondary particles (D 50= 2.5 μm) 1.0 g, conductive material (VGCF, Showa Denko) 0.04 g, sulfide solid electrolyte (LiI-LiBr-Li3PS4 sulfide solid electrolyte, D 50 0.776 g of cellulose acetate (0.2 μm), 0.02 g of binder (PVdF, manufactured by Kureha), and 1.7 g of butyl butyrate (manufactured by Kishida Chemical) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT) to prepare a negative electrode slurry (negative electrode composite). This negative electrode slurry was applied to a negative electrode current collector (Ni foil) by the blade method and dried on a hot plate at 100°C for 30 minutes to obtain a negative electrode layer (thickness 30 μm).

[0062] (Preparation of positive electrode layer) Positive electrode active material (LiNi coated with LiNbO3) 1 / 3 Co 1 / 3 Mn 1 / 3 O2) 1.5 g, conductive material (VGCF, Showa Denko) 0.023 g, sulfide solid electrolyte (LiI-LiBr-Li3PS4 sulfide solid electrolyte, D 50 0.239 g of cellulose acetate (0.2 μm), 0.011 g of binder (PVdF, manufactured by Kureha), and 0.8 g of butyl butyrate (manufactured by Kishida Chemical) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT) to prepare a positive electrode slurry. This positive electrode slurry was applied to a positive electrode current collector (Al foil) by the blade method and dried on a hot plate at 100°C for 30 minutes to obtain a positive electrode layer.

[0063] (Preparation of solid electrolyte layer) A sulfide solid electrolyte (LiI-LiBr-Li3PS4-based sulfide solid electrolyte), a binder (PVdF, manufactured by Kureha), and a dispersion medium (butyl butyrate) were dispersed using an ultrasonic disperser to prepare a slurry for the solid electrolyte layer. This slurry was applied to a transfer foil (Al foil) using a blade method and dried on a hot plate at 100°C for 30 minutes to obtain a transfer foil with a solid electrolyte layer.

[0064] (Battery construction) The positive electrode layer and the solid electrolyte layer were stacked so that they faced each other. After pressing with a roll press at a pressure of 50 kN / cm and a temperature of 160°C, the transfer foil (Al foil) was peeled off from the solid electrolyte layer and a 1 cm 2 A positive electrode laminate was obtained by punching out the laminate to a size of 1.08 cm. Next, the negative electrode layer and the solid electrolyte layer were laminated so that they faced each other. After pressing with a roll press at a pressure of 50 kN / cm, the transfer foil (Al foil) was peeled off from the solid electrolyte layer to obtain a negative electrode laminate. Furthermore, a solid electrolyte layer was laminated on the solid electrolyte layer side of the negative electrode laminate so that it faced each other. This laminate was pre-pressed with a flat uniaxial press at a pressure of 100 MPa and a temperature of 25°C, after which the transfer foil (Al foil) was peeled off from the solid electrolyte layer and a 1.08 cm laminate was obtained. 2 By punching out the sheet into a size of 100 mm, a negative electrode laminate having an additional solid electrolyte layer was obtained.

[0065] The positive electrode laminate and the negative electrode laminate with an additional solid electrolyte layer were stacked facing each other. This laminate was pressed in a flat uniaxial press at a pressure of 600 MPa and a temperature of 160°C to obtain a battery laminate. The resulting battery laminate was sandwiched between two restraint plates, which were then clamped together with fasteners at a pressure of 1 MPa to fix the distance between them, thereby obtaining a battery.

[0066] [Examples 2 to 4 and Comparative Example 1] Secondary particle diameter D 50 A battery was fabricated in the same manner as in Example 1, except that was changed to the values ​​shown in Table 1.

[0067] [Examples 5 to 8 and Comparative Example 2] Particle diameter D of sulfide solid electrolyte 50 A battery was fabricated in the same manner as in Example 3, except that was changed to the values ​​shown in Table 2.

[0068] [Examples 9 to 14] Primary particle diameter D 50 A battery was fabricated in the same manner as in Example 3, except that was changed to the values ​​shown in Table 3.

[0069] [evaluation] (Confining pressure fluctuation) The batteries obtained in Examples 1 to 14 and Comparative Examples 1 and 2 were CC / CV charged at 0.245 mA to 4.55 V, and then CC / CV discharged at 0.245 mA to 3.0 V. The confining pressure fluctuation (ΔMPa / mAh) per unit battery capacity was determined. The results are shown in Tables 1 to 3 and Figures 2 to 4.

[0070] (resistance) The batteries obtained in Examples 1 to 14 and Comparative Examples 1 and 2 were CC / CV charged to 4.35 V at 0.3 mA and then CC / CV discharged to 2.5 V at 0.3 mA, and this charge / discharge cycle was repeated five times. The voltage was then adjusted to 3.7 V, and a current of 10 mA was applied for five seconds. The direct current internal resistance (DCIR) was calculated from the relationship between the voltage drop and the current during discharge. The results are shown in Tables 1 to 3 and Figures 2 to 4.

[0071] (Capacity maintenance rate) The batteries obtained in Examples 1 to 14 and Comparative Examples 1 and 2 were CC / CV charged to 4.35 V at 0.3 mA, and then CC / CV discharged to 2.5 V at 0.3 mA to determine the initial discharge capacity. Charge and discharge were then repeated, and the discharge capacity at the 100th cycle was determined. The discharge capacity at the 100th cycle was divided by the initial discharge capacity to calculate the capacity retention rate (%). The results are shown in Tables 1 to 3.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] As shown in Table 1 and FIG. 2, Examples 1 to 4 had smaller confining pressure fluctuations than Comparative Example 1. In particular, Examples 2 to 4 had significantly smaller confining pressure fluctuations than Comparative Example 1. As such, it was confirmed that the negative electrode composites produced in Examples 1 to 4 can provide negative electrode layers that suppress volume changes due to charge and discharge. Furthermore, as shown in Table 1 and FIG. 2, it was confirmed that Examples 1 to 4 had lower resistance and higher capacity retention rates than Comparative Example 1, achieving both reduced resistance and improved cycle characteristics.

[0076] As shown in Table 2 and FIG. 3, Examples 3, 5 to 8 had smaller confining pressure fluctuations than Comparative Example 2. In particular, Examples 3, 6 to 8 had significantly smaller confining pressure fluctuations than Comparative Example 2. As such, it was confirmed that the negative electrode composites produced in Examples 3, 5 to 8 can provide negative electrode layers that suppress volume changes due to charge and discharge. Furthermore, in all of Examples 3, 5 to 8 and Comparative Example 2, the particle diameter D of the secondary particles 50 is the same at 10 μm, but the particle diameter D 50 In other words, in order to effectively suppress the volume change due to charging and discharging, the particle diameter D 50 , and the particle diameter D of the solid electrolyte 50 3, it was confirmed that Examples 3 and 5 to 8 had lower resistance and higher capacity retention rates than Comparative Example 2, and both reduced resistance and improved cycle characteristics were achieved.

[0077] As shown in Table 3 and Figure 4, the confining pressure fluctuation was small in Examples 3, 9 to 14. In addition, in Examples 3, 9 to 14, the particle diameter D 50 is the same at 10 μm, and the particle diameter D 50 Although the particle diameter of the primary particles is the same at 0.2 μm, 50 In other words, in order to more effectively suppress the volume change due to charging and discharging, the particle diameter D 50 , particle diameter of solid electrolyte D 50and the particle diameter of the primary particles D 50 4, it was confirmed that Examples 3, 10 to 13 had lower resistance and higher capacity retention rates than Example 14, and thus both reduced resistance and improved cycle characteristics were achieved. [Explanation of symbols]

[0078] 1...Positive electrode layer 2...Anode layer 3...electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...solid battery

Claims

1. A negative electrode mixture containing a negative electrode active material and a solid electrolyte, the negative electrode mixture contains, as the negative electrode active material, secondary particles formed by aggregation of a plurality of primary particles, the primary particles are Si-based active materials containing Si elements, The particle diameter D of the secondary particles ５０ is 2.5 μm or more and less than 20 μm, The particle diameter D of the solid electrolyte ５０ is 0.05 μm or more and less than 2.0 μm.

2. The particle diameter D of the secondary particles ５０ is 5.0 μm or more and 15 μm or less, The particle diameter D of the solid electrolyte ５０ The negative electrode mixture according to claim 1 , wherein the average particle size is 0.1 μm or more and 1.0 μm or less.

3. The particle diameter D of the primary particles ５０ The negative electrode mixture according to claim 1 , wherein the average particle size is 0.3 μm or more and 3.0 μm or less.

4. The particle diameter D of the primary particles ５０ The negative electrode mixture according to claim 1 , wherein the average particle size is 0.5 μm or more and 2.5 μm or less.

5. The negative electrode composite according to claim 1 , wherein the primary particles are porous particles.

6. The particle diameter D of the secondary particles ５０ The particle diameter D of the solid electrolyte ５０ The negative electrode mixture according to claim 1 , wherein the ratio of

7. The negative electrode mixture according to claim 1 , wherein the secondary particles are particles formed by aggregating the plurality of primary particles with a binder.

8. The negative electrode composite according to claim 1 , wherein the solid electrolyte is a sulfide solid electrolyte.

9. The negative electrode composite according to claim 8 , wherein the sulfide solid electrolyte contains Li, P, and S elements.

10. A solid-state battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer and containing a solid electrolyte, A solid-state battery, wherein the negative electrode layer contains the negative electrode mixture according to any one of claims 1 to 9.

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