Electrode active material, electrode layer, and battery

Abstract

The primary objective of this disclosure is to provide an electrode active material that can suppress volume changes in the electrode layer. [Solution] In this disclosure, an electrode active material containing secondary particles formed by the aggregation of a plurality of primary particles, wherein the primary particles are a Si-based active material containing the element Si, and the particle size D of the secondary particles 10 (μm) and particle size D 50 The above problem is solved by providing an electrode active material whose (μm) satisfies a predetermined formula (1).

Description

[Technical Field]

[0001] This disclosure relates to electrode active materials, electrode layers, and batteries. [Background technology]

[0002] In recent years, there has been a great deal of activity in battery development. For example, in the automotive industry, development is progressing on batteries used in electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), and hybrid electric vehicles (HEVs). Batteries typically have a positive electrode layer, a negative electrode layer, and an electrolyte layer placed between the positive and negative electrode layers. Furthermore, active materials containing the element Si (Si-based active materials) are known as electrode active materials. For example, Patent Document 1 discloses a negative electrode for a secondary battery that contains composite particles comprising a plurality of porous silicon particles and a binder. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-017797 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] While Si-based active materials offer high capacity, they exhibit significant volume changes during charging and discharging. Large volume changes during charging and discharging can easily lead to crack formation in the electrode layer, which in turn can degrade battery performance (e.g., increased resistance, reduced cycle characteristics). Therefore, there is a need to suppress volume changes during charging and discharging in electrode layers containing Si-based active materials.

[0005] This disclosure has been made in view of the above circumstances, and its main purpose is to provide an electrode active material that can suppress volume changes in the electrode layer. [Means for solving the problem]

[0006] [1] An electrode active material containing secondary particles formed by aggregation of a plurality of primary particles, wherein the primary particles are Si-based active materials containing Si element, the particle diameter D 90 (μm) and the particle diameter D 50 (μm) satisfy the following formula (1), the electrode active material. Formula (1): D 50 / D 10 <3.7

[0007] [2] An electrode active material containing secondary particles formed by aggregation of a plurality of primary particles, wherein the primary particles are Si-based active materials containing Si element, the particle diameter D 50 (μm) and the particle diameter D 90 (μm) satisfy the following formula (2), the electrode active material. Formula (2): D 90 / D 50 <3.7

[0008] [3] An electrode active material containing secondary particles formed by aggregation of a plurality of primary particles, wherein the primary particles are Si-based active materials containing Si element, the particle diameter D 10 (μm) and the particle diameter D 90 (μm) satisfy the following formula (3), the electrode active material. Formula (3): D 90 / D 10 [[ID=​​​​​​​​​​​​

[0011] [6] In the above formula (3), the above D 90 / D 10 The electrode active material described in [3], wherein the ratio is 2.5 or higher.

[0012] [7] The primary particles are porous particles, as described in any of [1] to [6].

[0013] [8] The electrode active material according to any one of [1] to [7], wherein the secondary particles are particles formed by agglomerating the above-mentioned plurality of primary particles with a binder.

[0014] [9] The above secondary particles are a sintered body, an electrode active material as described in any of [1] to [7].

[0015]

[10] An electrode layer containing an electrode active material described in any of [1] to [9].

[0016]

[11] The electrode layer according to

[10] , wherein the electrode layer is a negative electrode layer.

[0017]

[12] A 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, A battery in which one of the positive electrode layer and the negative electrode layer contains the electrode active material described in any of [1] to [9].

[0018]

[13] The battery according to

[12] , wherein the electrolyte layer is a solid electrolyte layer. [Effects of the Invention]

[0019] This disclosure provides an electrode active material that can suppress volume changes in the electrode layer. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic cross-sectional view illustrating a battery in this disclosure. [Figure 2] This graph shows the results for Examples 1-5 and Comparative Examples 1-6. [Figure 3] This graph shows the results for Examples 6-10 and Comparative Example 7. [Modes for carrying out the invention]

[0021] The electrode active material, electrode layer, and battery described herein will be explained in detail below.

[0022] A. Electrode active material The electrode active material in this disclosure contains a plurality of primary particles and secondary particles formed by the aggregation of the plurality of primary particles. The primary particles are a Si-based active material containing the element Si, and the particle size D of the secondary particles is 10 (μm), particle size D 50 (μm) and particle size D 90 (μm) satisfies at least one of the following equations (1) to (3). Formula (1):D 50 / D 10 <3.7 Formula (2):D 90 / D 50 <3.7 Formula (3):D 90 / D 10 <15.4 Herein, in this disclosure, particle size D 10 , D 50 and D 90 These represent the cumulative 10% particle size, cumulative 50% particle size, and cumulative 90% particle size in the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer, respectively.

[0023] According to this disclosure, the particle size D of secondary particles 10 , D 50 and D 90 Since it satisfies at least one of the predetermined equations (1) to (3), it becomes an electrode active material that can suppress volume changes in the electrode layer.

[0024] In the secondary particles in this disclosure, the particle size D 10 (μm) and particle size D 50 It is preferable that (μm) satisfies the following formula (1). Formula (1):D 50 / D 10 <3.7 D 50 / D 10 The particle size is below average (D 50 This is an index that shows the extent of the distribution in the region below (the region on the fine particle side). 50 / D 10 A smaller value indicates a narrower distribution in the region of the fine particles. 50 / D 10 It may be 3.5 or less, 3.3 or less, 3.0 or less, or 2.7 or less. On the other hand, D 50 / D 10 For example, it may be 1.5 or higher, 1.6 or higher, 2.0 or higher, or 2.3 or higher.

[0025] Here, if the particle size of the secondary particles is small, it is presumed that the aggregation of the primary particles is insufficient. In that case, it is presumed that sufficient gaps between the primary particles in the secondary particles (voids in the secondary particles) are not formed, and the expansion of the primary particles cannot be sufficiently absorbed by the secondary particles as a whole. In this respect, D 50 / D 10 If the value is less than 3.7, it is presumed that the contact points between secondary particles decrease, and the formation of bridges (structures in which secondary particles are connected and tensed) is suppressed. As a result, the expansion of secondary particles is dispersed without being transmitted to each other, and it is presumed that the volume change of the electrode layer can be suppressed. On the other hand, D 50 / D 10 If the value is greater than 3.7, it is presumed that the frequency of bridging between secondary particles is high, and the expansion of secondary particles is transmitted to each other, increasing the volume change of the electrode layer.

[0026] In the secondary particles in this disclosure, the particle size D 50 (μm) and particle size D90 It is preferable that (μm) satisfies the following formula (2). Formula (2):D 90 / D 50 <3.7 D 90 / D 50 This refers to particles with a diameter above average (D 50 This is an index that shows the extent of the distribution in the region (the region on the coarse particle side) mentioned above. 90 / D 50 A smaller value indicates a narrower distribution in the region of coarse particles. 90 / D 50 It may be 3.6 or less, 3.3 or less, 3.0 or less, or 2.7 or less. On the other hand, D 90 / D 50 For example, it may be 1.5 or higher, 1.6 or higher, 2.0 or higher, or 2.3 or higher.

[0027] Here, if the particle size of the secondary particles is large, it is presumed that the primary particles will aggregate sufficiently and sufficient voids will be formed in the secondary particles. On the other hand, if the particle size of the secondary particles is too large, it is presumed that uneven reactions will occur within the secondary particles, resulting in localized expansion and contraction. In this respect, D 90 / D 50 When the value is less than 3.7, coarse particles are more easily densified in the electrode layer, which broadens the reaction initiation points in secondary particles, and as a result, it is presumed that reaction unevenness can be suppressed.

[0028] In the secondary particles in this disclosure, the particle size D 10 (μm) and particle size D 90 It is preferable that (μm) satisfies the following formula (3). Formula (3):D 90 / D 10 <15.4 D 90 / D 10 D 90 From D 10 This is an indicator that shows the breadth of the distribution within the range. 90 / D 10 A smaller value indicates a narrower distribution.90 / D 10 It may be 15.0 or less, 13.0 or less, or 10.0 or less. On the other hand, D 90 / D 10 For example, it may be 2.0 or higher, 2.5 or higher, 3.0 or higher, 5.0 or higher, or 7.0 or higher.

[0029] D 90 / D 10 When the value is less than 15.4, it is presumed that the contact points with the electrolyte (e.g., solid electrolyte) in the electrode layer become good for the electrode active material as a whole, and a good ion conduction path is formed. Therefore, it is thought that local reactions in the electrode layer can be suppressed, and local expansion and contraction of the electrode layer can be suppressed.

[0030] The electrode active material in this disclosure may satisfy any one of formulas (1) to (3), any two of them, or all three. Specifically, cases where two formulas are satisfied include cases where formulas (1) and (3) are satisfied but formula (2) is not, and cases where formulas (2) and (3) are satisfied but formula (1) is not. In cases where both formulas (1) and (2) are satisfied, formula (3) is usually also satisfied.

[0031] Secondary particle size D 10 (μm) is not particularly limited as long as it satisfies the above formula. 10 (μm) is, for example, 0.1 μm or more, may be 0.5 μm or more, may be 1.0 μm or more, or may be 3.0 μm or more. On the other hand, D 10 (μm) is, for example, 15.0 μm or less, but may also be 13.0 μm or less, 11.0 μm or less, 10.0 μm or less, 8.0 μm or less, or 5.0 μm or less.

[0032] Secondary particle size D 50 (μm) is not particularly limited as long as it satisfies the above formula. 50(μm) is, for example, 1.0 μm or more, and may be 2.0 μm or more, may be 3.0 μm or more, and may be 5.0 μm or more. On the other hand, D 50 (μm) is, for example, 50.0 μm or less, and may be 30.0 μm or less, may be 25.0 μm or less, may be 20.0 μm or less, may be 15.0 μm or less, may be 10.0 μm or less, may be 8.0 μm or less, and may be 5.0 μm or less.

[0033] The particle diameter D of the secondary particles 90 (μm) is not particularly limited as long as it satisfies the above formula. D 90 (μm) is, for example, 5.0 μm or more, and may be 10.0 μm or more, may be 15.0 μm or more, may be 20.0 μm or more, and may be 25.0 μm or more. On the other hand, D 90 (μm) is, for example, 100.0 μm or less, and may be 70.0 μm or less, may be 50.0 μm or less, and may be 30.0 μm or less.

[0034] A method for adjusting the particle diameter of the secondary particles will be described later.

[0035] 1. Primary particles The primary particles in the present disclosure are Si-based active materials containing Si element.

[0036] The primary particles (Si-based active material) may be elemental Si, may be an alloy (Si alloy) containing Si as a main component, or may be a Si oxide. The proportion of Si element in the Si alloy is, for example, 50 mol% or more and 95 mol% or less.

[0037] Primary particles may be solid particles. Alternatively, primary particles may be porous particles having internal voids. Here, Si-based active materials having voids are referred to as porous Si. The presence of voids can be confirmed by SEM (scanning electron microscope) observation. Furthermore, the porosity is not particularly limited, but may be, for example, 4% or more, or 10% or more. Also, the above porosity may be, for example, 40% or less, or 20% or less. The porosity can be determined by the following procedure, for example. First, a cross-sectional image of the Si-based active material is obtained using SEM. From the obtained image, the silicon portion and the void portion are separated using image analysis software and binarized. The areas of the silicon portion and the void portion are determined, and the porosity (%) is calculated from the following formula. Porosity (%) = 100 × (Area of ​​voids) / ((Area of ​​silicon) + (Area of ​​voids))

[0038] Porous Si preferably has many minute voids with a pore diameter of 100 nm or less. Voids with a pore diameter of 100 nm or less can suppress void collapse due to pressing compared to voids with a pore diameter of 100 nm or more. The void volume X (cumulative void volume) of voids with a pore diameter of 100 nm or less is, for example, 0.05 cc / g or more, 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 X can be determined, for example, by BET measurement.

[0039] It is preferable that porous Si has many minute voids with a pore diameter of 50 nm or less. Voids with a pore diameter of 50 nm or less can further suppress void collapse due to pressing compared to voids with a pore diameter greater than 50 nm and a pore diameter of 100 nm or less. The void amount Y of voids with a pore diameter of 50 nm or less is, for example, 0.05 cc / g or more, may be 0.075 cc / g or more, or may be 0.10 cc / g or more. On the other hand, the void amount Y is, for example, 0.25 cc / g or less.

[0040] Porous Si preferably has many minute voids with a pore diameter of 10 nm or less. Voids with a pore diameter of 10 nm or less can accommodate precipitated Li with a higher packing efficiency compared to voids with a pore diameter of 10 nm or more, thus suppressing volume changes due to charging and discharging. The void volume Z of voids with a pore diameter of 10 nm or less is, for example, 0.015 cc / g or more, may be 0.02 cc / g or more, or may be 0.03 cc / g or more. On the other hand, the void volume Z is, for example, 0.09 cc / g or less.

[0041] One method for producing porous Si is to prepare an alloy of Li and Si (LiSi alloy), and then remove Li from the LiSi alloy. LiSi alloy can be obtained, for example, by mixing Li and Si. One method for removing Li from the LiSi alloy is to react the LiSi alloy with a Li extracting agent. Examples of Li extracting agents include alcohols such as methanol and acids such as acetic acid.

[0042] The primary particles (Si-based active material) may be crystalline or amorphous. If crystalline, the Si-based active material typically has a Si crystalline phase. An example of the Si crystalline phase is the diamond-type crystalline phase. General Si contains the diamond-type crystalline phase as its Si crystalline phase. The Si-based active material may contain the diamond-type crystalline phase as the main phase of its Si crystalline phase.

[0043] Another example of a Si crystal phase is a silicon clathrate type crystal phase. This silicon clathrate type crystal phase may be either a silicon clathrate I type crystal phase or a silicon clathrate II type crystal phase. In a silicon clathrate type crystal phase, multiple Si elements constitute a polyhedron (cage) containing pentagons or hexagons. This polyhedron has internal spaces that can encapsulate metal ions such as Li ions. The insertion of metal ions into these spaces suppresses volume changes due to charging and discharging. The Si-based active material may contain either a silicon clathrate I type crystal phase or a silicon clathrate II type crystal phase as the main phase of the Si crystal phase. A method for producing a silicon clathrate type crystal phase includes, for example, reacting Na and Si to produce a Na-Si alloy, and then sintering the Na-Si alloy to remove the Na.

[0044] Primary particle size D 10 , D 50 and D 90 The particle size D is not particularly limited as long as the secondary particles described above are obtained. 10 For example, the particle size is between 0.1 μm and 3.0 μm. 50 For example, the particle size D is 0.3 μm or larger and 5.0 μm or smaller. 90 For example, the particle size is between 0.5 μm and 10.0 μm.

[0045] One example of a method for forming porous Si (porous particles) is to produce a LiSi alloy by reacting solid primary particles (Si-based active material) with metallic Li, and then remove Li from the LiSi alloy. The LiSi alloy can be obtained, for example, by mixing primary particles (Si-based active material) and metallic Li. The molar ratio of Li to Si (Li / Si) is, for example, 1.0 or higher, may be 2.0 or higher, 3.0 or higher, or 4.0 or higher. On the other hand, Li / Si is, for example, 8.0 or lower. A method for removing Li from the LiSi alloy can be, for example, by reacting 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.

[0046] Another example of a method for forming porous particles is to produce an MgSi alloy by reacting solid primary particles (Si-based active material) with metallic Mg, and then removing Mg from the MgSi alloy. The MgSi alloy can be obtained, for example, by heating a mixture of primary particles (Si-based active material) and metallic Mg. The ratio of Mg to Si (Mg / Si) is, for example, 1.0 or more, may be 1.5 or more, or 2.0 or more. On the other hand, the Mg / Si ratio is, for example, 6.0 or less. As a method for removing Mg from the MgSi alloy, for example, the MgSi alloy can be heated in an inert gas atmosphere containing oxygen to change the Mg in the Mg-Si alloy to MgO, and then the MgO can be removed with an acid solution. Examples of acid solutions include aqueous solutions containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0047] In addition, the primary particles (clathrate Si) having the above-described class rate type crystal phase can be produced by mixing Si and a Na source such as NaH and heating to produce a Na-Si alloy, and then heating the Na-Si alloy to reduce the amount of Na in the Na-Si alloy to generate a silicon clathrate type crystal phase. Further, the primary particles (porous clathrate Si) having voids and a clathrate type crystal phase can be produced by using the porous Si as the above Si.

[0048] 2. Secondary particles The secondary particles in the present disclosure are particles in which a plurality of the above-described primary particles are aggregated. The secondary particles are, for example, particles in which a plurality of primary particles are aggregated by a binder. That is, the electrode active material in the present disclosure may contain a binder. Examples of the binder 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 weight or more and 30% by weight or less, and may be 5% by weight or more and 25% by weight or less.

[0049] In addition, the secondary particles may be a sintered body. The sintered body (secondary particles) may contain at least one of a carbide of a saccharide and a carbide of an organic acid inside. Examples of the saccharide include monosaccharides such as glucose and fructose, and disaccharides such as sucrose and maltose. Examples of the organic acid include formic acid, acetic acid, propionic acid, and butyric acid.

[0050] In the secondary particles in the present disclosure, the particle diameter D 10 (μm), the particle diameter D 50 (μm) and the particle diameter D 90 (μm) may satisfy the following formula (4). Formula (4): (D 90 -D 10 ) / D 50 <8.7 (D90 -D 10 ) / D 50 D 50 This is an index that shows the extent of the overall distribution of particles relative to a standard. (D 90 -D 10 ) / D 50 A smaller value means a narrower distribution. (D 90 -D 10 ) / D 50 It may be 8.0 or less, 6.0 or less, 5.0 or less, or 3.0 or less. On the other hand, (D 90 -D 10 ) / D 50 For example, it may be 1.0 or greater, 1.3 or greater, 1.5 or greater, or 2.0 or greater.

[0051] Secondary particle size D 10 , D 50 and D 90 This is as described above. Furthermore, the particle size of the secondary particles can be considered as the particle size of the electrode active material.

[0052] The method for producing secondary particles in this disclosure is not particularly limited, but one example is spray drying. Spray drying is a method of drying a slurry containing the above-mentioned plurality of primary particles and binder and a dispersion medium by spraying it into hot air. The particle size of the secondary particles can be controlled by adjusting, for example, the particle size of the primary particles, as well as the conditions of the spray drying method, such as the spray pressure and slurry flow rate. For example, the spray pressure is 0.05 MPa or more and 0.5 MPa or less. For example, the slurry flow rate is 0.5 g / min or more and 30 g / min or less.

[0053] Furthermore, the method described in the examples can be used as a method for producing secondary particles that are sintered bodies.

[0054] 3. Electrode active material The electrode active material in this disclosure is typically used in batteries. The electrode active material may be a positive electrode active material or a negative electrode active material, but the latter is preferred because it allows for the creation of a high-capacity battery.

[0055] B. Electrode layer The electrode layer in this disclosure contains the electrode active material described above. The electrode active material is the same as described in "A. Electrode Active Material" above, so its description is omitted here.

[0056] According to this disclosure, because the electrode active material described above is included, volume changes are suppressed and crack formation is suppressed in the electrode layer.

[0057] The proportion of electrode active material in the electrode layer is, for example, 20% by weight or more, but may also be 30% by weight or more, or 40% by weight or more. If the proportion of electrode active material is too low, a sufficient energy density may not be obtained. On the other hand, the proportion of electrode active material in the electrode layer is, for example, 80% by weight or less, but may also be 70% by weight or less, or 60% by weight or less. If the proportion of electrode active material is too high, the ionic conductivity and electronic conductivity of the electrode layer may decrease.

[0058] The electrode layer in this disclosure may optionally contain at least one of a solid electrolyte, a conductive material, and a binder.

[0059] Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. Sulfide solid electrolytes preferably contain sulfur (S) as the main component of the anionic element. Oxide solid electrolytes preferably contain oxygen (O) as the main component of the anionic element. Halide solid electrolytes preferably contain a halogen (at least one of F, Cl, Br, or I) as the main component of the anion. Among these, sulfide solid electrolytes are preferred because of their high ionic conductivity.

[0060] The sulfide solid electrolyte may further contain element X (where X is at least one of As, Sb, Si, Ge, Sn, B, Al, Ga, and In). The sulfide solid electrolyte may also further contain at least one of element O and a halogen element.

[0061] The sulfide solid electrolyte is the ortho-composition PS4. 3- It is preferable that the structure has the anionic structure as the main component, because it has high chemical stability. PS4 3- The proportion of the structure is, for example, 70 mol% or more, and may be 90 mol% or more, relative to the total anion structure in the sulfide solid electrolyte.

[0062] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2-P2S5-LiI, and Li2S-P2S5-Z. m S n (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga.) Li2S-SiS2-Li3PO4 is an example.

[0063] The sulfide solid electrolyte may be glass (amorphous), crystallized glass (glass ceramics), or a crystalline sulfide solid electrolyte. Examples of crystalline phases for crystalline sulfide solid electrolytes include the thio-LISICON type crystalline phase, the LGPS type crystalline phase, and the argyrodite type crystalline phase.

[0064] Other examples of solid electrolytes include organic solid electrolytes such as polymer electrolytes and gel electrolytes.

[0065] The proportion of solid electrolyte in the electrode layer is, for example, between 10% and 60% by weight. If the proportion of solid electrolyte is too low, there may be insufficient ion conduction paths in the electrode layer. If the proportion of solid electrolyte is too high, the proportion of electrode active material will be relatively low, which may result in a lower energy density.

[0066] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjenblack (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs). The proportion of conductive material in the electrode layer is, for example, 0.1% by weight or more and 10% by weight or less.

[0067] Examples of binders include rubber-based binders such as butylene rubber (BR) and styrene-butadiene rubber (SBR), as well as fluoride-based binders such as polyvinylidene fluoride (PVDF). The proportion of binder in the electrode layer is, for example, 0.5% by weight or more and 5% by weight or less.

[0068] The electrode layer in this disclosure is typically used in batteries. The electrode layer may be a positive electrode layer or a negative electrode layer, but the latter is preferred because it allows for the creation of high-capacity batteries. The thickness of the electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0069] C.Battery Figure 1 is a schematic cross-sectional view illustrating a battery in this disclosure. The battery 10 shown in Figure 1 includes a positive electrode layer 1, a negative electrode layer 2, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 for collecting current from the positive electrode layer 1, and a negative electrode current collector 5 for collecting current from the negative electrode layer 2. In this disclosure, one of the positive electrode layer 1 and the negative electrode layer 2 contains the electrode active material described in "A. Electrode Active Material".

[0070] According to this disclosure, by using the electrode active material described above, cracking of the electrode layer is suppressed, resulting in a battery in which the increase in resistance is suppressed and the deterioration of cycle characteristics is suppressed. As described above, it is preferable that the electrode active material described above is the negative electrode active material, that is, that the negative electrode layer contains the electrode active material described above. The details of a battery in which the negative electrode layer contains the electrode active material described above will be described below.

[0071] 1. Negative electrode layer The negative electrode layer is a layer containing at least a negative electrode active material. The negative electrode active material and the negative electrode layer are the same as those described in "A. Electrode Active Material" and "B. Electrode Layer". If the electrolyte layer described later contains an electrolyte solution, the negative electrode layer may also contain the electrolyte solution described later as the electrolyte.

[0072] 2. Positive electrode layer The positive electrode layer is a layer containing at least a positive electrode active material. The positive electrode layer may also contain, if necessary, at least one of an electrolyte, a conductive material, and a binder. The conductive material and binder are as described in "B. Electrode Layer". The electrolyte is described in "3. Electrolyte Layer".

[0073] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Rock salt layered active materials such as O2, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 Examples include spinel-type active materials such as O4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0074] 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 sulfide solid electrolytes). Examples of Li-ion conductive oxides include LiNbO3. The thickness of the coating layer is, for example, 1 nm to 30 nm. In addition, Li2S can be used as the positive electrode active material.

[0075] Examples of the positive electrode active material's shape include particulate matter. The average particle size (D) of the positive electrode active material is... 50 The average particle diameter (D) of the positive electrode active material is not particularly limited, but for example it may be 10 nm or more, and may also be 100 nm or more. 50 ) is, for example, 50 μm or less, and may also be 20 μm or less. D 50 The details are as described above.

[0076] The proportion of positive electrode active material in the positive electrode layer is, for example, 20% by weight or more and 80% by weight or less. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0077] 3. Electrolyte layer The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least an electrolyte. The electrolyte layer may also contain a binder as needed. The binder is as described in "B. Electrode Layer".

[0078] The electrolyte may be a solid electrolyte or a liquid electrolyte (electrolyte solution). Examples of solid electrolytes include those described in "B. Electrode Layer".

[0079] The electrolyte preferably contains a supporting salt and a solvent. Examples of supporting salts (lithium salts) for lithium-ion conductive electrolytes include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6, and organic lithium salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(FSO2)2, and LiC(CF3SO2)3. Examples of solvents used in the electrolyte include cyclic esters (cyclic carbonates) such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), and linear esters (linear carbonates) such as dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0080] The electrolyte layer may be a solid electrolyte layer containing a solid electrolyte. Alternatively, the electrolyte layer may be a layer in which the separator is impregnated with the aforementioned electrolyte. The material of the separator may be an organic material or an inorganic material. Specifically, examples include porous membranes such as polyethylene (PE), polypropylene (PP), cellulose, polyvinylidene fluoride, polyamide, and polyimide, nonwoven fabrics such as resin nonwoven fabrics and glass fiber nonwoven fabrics, and porous ceramic membranes. Furthermore, the separator may have a single-layer structure or a laminated structure.

[0081] 4. Other configurations The battery in this disclosure preferably has a positive electrode current collector for collecting current from the positive electrode layer and a negative electrode current collector for collecting current from the negative electrode layer. Examples of materials for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include SUS, copper, nickel, and carbon.

[0082] The battery in this disclosure may further include a restraining jig that applies restraining pressure along the thickness direction to the positive electrode layer, electrolyte layer, and negative electrode layer. In particular, when the electrolyte layer is a solid electrolyte layer, it is preferable to apply restraining pressure in order to form good ion conduction paths and electron conduction paths. The restraining pressure may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. On the other hand, the restraining pressure may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0083] 5.Battery The type of battery in this disclosure is not particularly limited, but is typically a lithium-ion battery. Furthermore, the battery in this disclosure may be a liquid battery in which the electrolyte layer contains an electrolyte solution, or a solid battery in which the electrolyte layer contains a solid electrolyte. The solid battery may be a semi-solid battery or a fully solid battery. In this disclosure, a semi-solid battery is a battery in which the electrolyte layer has a solid electrolyte and a liquid component (e.g., an ionic liquid). In this disclosure, a fully solid battery is a battery in which the electrolyte layer has only an inorganic solid electrolyte as the electrolyte. Furthermore, the battery in this disclosure may be a primary battery or a secondary battery, but a secondary battery is preferred because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery.

[0084] Applications of batteries include, for example, powering vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline cars, and diesel cars. In particular, they are preferred for use as a power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Batteries may also be used as a power source for other mobile devices (e.g., trains, ships, aircraft), or as a power source for electrical products such as information processing devices.

[0085] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0086] [Example 1] (Preparation of primary particles) 0.65 g of Si particles (manufactured by Kojun Chemical) and 0.60 g of Li metal (manufactured by 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 the LiSi precursor and 125 ml of dispersion medium (1,3,5-trimethylbenzene, manufactured by Nacalai Tesque) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT). The resulting LiSi precursor dispersion was cooled to 0°C, and 125 ml of ethanol (manufactured by Nacalai Tesque) as a Li extraction solvent was added dropwise, and the mixture was reacted for 120 minutes. After the reaction, 50 ml of acetic acid (manufactured by Nacalai Tesque) was added dropwise, and the mixture was reacted for another 60 minutes. After the reaction, the liquid and solid reactants were separated by suction filtration. The obtained solid reactants were vacuum-dried at 120°C for 2 hours to recover porous primary particles (porous Si).

[0087] (Fabrication of secondary particles (non-sintered bodies)) The obtained primary particles (porous Si) and a PVDF-HFP binder (manufactured by Kureha Corporation) were dispersed and partially dissolved in dimethyl carbonate (manufactured by Nacalai Tesque Corporation) in a primary particle:binder ratio (weight ratio) of 100:13.3 to obtain a slurry. This slurry was sprayed into a spray dryer under a nitrogen gas atmosphere at 140°C and dried (spray drying method). By adjusting the spray pressure and slurry flow rate in the spray drying method, particle sizes (D) as shown in Table 1 were obtained. 10 , D 50 , D 90 Secondary particles (non-sintered bodies) having the following characteristics were obtained.

[0088] (Preparation of evaluation batteries) As described below, an evaluation battery was fabricated using the above secondary particles as the negative electrode active material.

[0089] The above secondary particles are 1.0 g, conductive material (VGCF, manufactured by Showa Denko) is 0.04 g, and sulfide solid electrolyte (LiI-LiBr-Li3PS4-based sulfide solid electrolyte, D 50 A negative electrode slurry was prepared by mixing 0.776 g of (0.2 μm) material, 0.02 g of binder (PVdF, manufactured by Kureha Corporation), and 1.7 g of butyl butyrate (manufactured by Kishida Chemical Co., Ltd.) using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). This negative electrode slurry was coated onto a negative electrode current collector (Cu foil) using the blade method and dried on a hot plate at 100°C for 30 minutes. This resulted in obtaining a negative electrode having a negative electrode current collector and a negative electrode layer.

[0090] Next, the positive electrode active material (LiNi 0.8 Co 0.15 Mn 0.05 1.5g of O2, 0.023g of conductive material (VGCF, manufactured by Showa Denko), and a sulfide solid electrolyte (LiI-LiBr-Li3PS4-based sulfide solid electrolyte, D 50 A positive electrode slurry was prepared by mixing 0.239 g of (0.2 μm) material, 0.011 g of binder (PVdF, manufactured by Kureha Corporation), and 0.8 g of butyl butyrate (manufactured by Kishida Chemical Co., Ltd.) using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). This positive electrode slurry was coated onto a positive electrode current collector (Al foil) using the blade method and dried on a hot plate at 100°C for 30 minutes. This resulted in obtaining a positive electrode having a positive electrode current collector and a positive electrode layer.

[0091] Next, a sulfide solid electrolyte (LiI-LiBr-Li3PS4-based sulfide solid electrolyte), a binder (PVdF, manufactured by Kureha Corporation), and a dispersion medium (butyl butyrate) were dispersed using an ultrasonic dispersion device to prepare a slurry for the solid electrolyte layer. This slurry was coated onto a transfer foil (Al foil) using the blade method and dried on a hot plate at 100°C for 30 minutes. This resulted in a transfer foil having a solid electrolyte layer.

[0092] The positive electrode and transfer foil were laminated so that the positive electrode layer and the solid electrolyte layer faced each other. After pressing this in a roll press machine at a pressure of 50 kN / cm and a temperature of 160°C, the solid transfer foil (Al foil) was peeled off, and 1 cm 2 The material was punched out to the specified size. This obtained a positive electrode laminate. Next, the negative electrode and transfer foil were laminated so that the negative electrode layer and solid electrolyte layer faced each other. This was pressed in a roll press at a pressure of 50 kN / cm, and then the transfer foil (Al foil) was peeled off. This obtained a negative electrode laminate. Furthermore, a transfer foil was laminated on the solid electrolyte layer side of the negative electrode laminate so that the solid electrolyte layer faced each other. This laminate was pre-pressed in a flat single-axis press at a pressure of 100 MPa and a temperature of 25°C, and then the transfer foil (Al foil) was peeled off from the solid electrolyte layer, and 1.08 cm 2 By punching out the material to the specified size, a negative electrode laminate having an additional solid electrolyte layer was obtained.

[0093] A positive electrode laminate and a negative electrode laminate having an additional solid electrolyte layer were stacked facing each other. This laminate was pressed in a planar single-axis press at a press pressure of 600 MPa and a temperature of 160°C to obtain a battery laminate. The obtained battery laminate was sandwiched between two restraint plates, and these two restraint plates were fastened together with fasteners at a restraint pressure of 1 MPa to fix the distance between them. This resulted in obtaining an evaluation battery (all-solid-state battery).

[0094] [Examples 2-5 and Comparative Examples 1-6] In preparing the secondary particles, secondary particles with the particle sizes shown in Table 1 were obtained by adjusting the spray drying conditions (at least one of the spray pressure and slurry flow rate). An evaluation battery was prepared in the same manner as in Example 1, except that these secondary particles were used as the negative electrode active material.

[0095] [Example 6] (Fabrication of secondary particles (sintered bodies)) Solid Si particles (SiOx (High Purity Chemicals)) and fructose were dispersed in water in a ratio (by weight) of Si particles:fructose = 100:7.4 to obtain a slurry. This slurry was sprayed into a 200°C spray dryer and dried (spray drying method). By adjusting the spray pressure and slurry flow rate in the spray drying method, particle sizes (D) as shown in Table 1 were obtained. 10 , D 50 , D 90 A secondary particle was obtained that had the following properties:

[0096] Next, secondary particles, which are sintered bodies, were fabricated as follows. The obtained secondary particles were calcined in Ar at 700°C for 6 hours to carbonize the fructose. 1.5 g of the carbonized secondary particles and 2.61 g of Mg2Si (high-purity chemical) were reduced by calcining at 80 MPa, 700°C, for 6 hours. Subsequently, the primary particles within the secondary particles were made porous by washing and removing MgO with hydrochloric acid. After washing, the liquid and solid reactants were separated by suction filtration. The obtained solid reactant (sintered body) was vacuum dried at 120°C for 12 hours and recovered.

[0097] (Preparation of evaluation batteries) An evaluation battery was prepared in the same manner as in Example 1, except that the recovered sintered body was used as the negative electrode active material.

[0098] [Examples 7-10 and Comparative Example 7] By adjusting the spray pressure and slurry flow rate in the spray drying method, the particle size (D) shown in Table 1 can be adjusted. 10 , D 50 , D 90 Secondary particles having the following properties were obtained. The obtained secondary particles were sintered in the same manner as in Example 6 to obtain a sintered body. An evaluation battery was fabricated in the same manner as in Example 1, except that this sintered body was used as the negative electrode active material.

[0099] [evaluation] The batteries obtained in Examples 1-10 and Comparative Examples 1-7 were CC / CV charged to 4.55V at 0.245mA, and then CC / CV discharged to 3.0V at 0.245mA. During this process, the confinement pressure fluctuation per unit of battery capacity (ΔMPa / mAh) was determined as the expansion rate. The confinement pressure fluctuation of Comparative Example 1 was used as the baseline for relative evaluation. The results are shown in Table 1, Figures 2 and 3. Figures 2(a)-(c) show the results for Comparative Examples 1-6 and Examples 1-5, respectively, while Figures 3(a)-(c) show the results for Comparative Example 7 and Examples 6-10, respectively. In Figures 2 and 3, examples are indicated by circles, and comparative examples by triangles.

[0100] [Table 1]

[0101] As shown in Table 1 and Figures 2-3, in the battery using the electrode active material of this disclosure, it was confirmed that the expansion rate was significantly suppressed and the volume change of the electrode layer was suppressed. Also, Example 7(D 90 / D 50 The expansion rate of Example 6 (D = 2.5) is lower than that of Example 6 (D 90 / D 50 The expansion rate is greater than that of =2.9), D 90 / D 50 It was inferred that if it becomes too small, the expansion rate tends to increase unexpectedly. Therefore, D 90 / D 50 Regarding this, a value of 2.0 or higher is preferred, and a value of 2.5 or higher is more preferred. [Explanation of Symbols]

[0102] 1 ... Positive electrode layer 2 ... Negative electrode layer 3...electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 10...battery

Claims

1. An electrode active material containing secondary particles formed by the aggregation of multiple primary particles, The primary particles are Si-based active materials containing Si elements. Particle size D of the secondary particles １０ (μm) and particle size D ５０ An electrode active material whose (μm) satisfies the following formula (1). Equation (1): D ５０ / D １０ <3.7

2. An electrode active material containing secondary particles formed by the aggregation of multiple primary particles, The primary particles are Si-based active materials containing Si elements. Particle size D of the secondary particles ５０ (μm) and particle size D ９０ An electrode active material whose (μm) satisfies the following equation (2). Equation (2): D ９０ / D ５０ <3.7

3. An electrode active material containing secondary particles formed by the aggregation of multiple primary particles, The primary particles are Si-based active materials containing Si elements. The particle diameter D of the secondary particles １０ (μm) and the particle diameter D ９０ (μm) satisfy the following formula (3), and it is an electrode active material. Equation (3): D ９０ / D １０ <15.4

4. In the above formula (1), D ５０ / D １０ The electrode active material according to claim 1, wherein the ratio is 1.6 or higher.

5. In formula (2) above, D ９０ / D ５０ The electrode active material according to claim 2, wherein the ratio is 1.6 or higher.

6. In the above formula (3), D ９０ / D １０ The electrode active material according to claim 3, wherein the ratio is 2.5 or higher.

7. The electrode active material according to any one of claims 1 to 3, wherein the primary particles are porous particles.

8. The electrode active material according to any one of claims 1 to 3, wherein the secondary particles are particles formed by agglomerating the plurality of primary particles with a binder.

9. The electrode active material according to any one of claims 1 to 3, wherein the secondary particles are a sintered body.

10. An electrode layer containing the electrode active material according to any one of claims 1 to 3.

11. The electrode layer according to claim 10, wherein the electrode layer is a negative electrode layer.

12. A 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, A battery in which one of the positive electrode layer and the negative electrode layer contains the electrode active material according to any one of claims 1 to 3.

13. The battery according to claim 12, wherein the electrolyte layer is a solid electrolyte layer.

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