Electrode layer and battery

Abstract

To provide an electrode layer with a less changeable volume.SOLUTION: In the present disclosure, an electrode layer includes composite particles, and the composite particles include a plurality of active materials containing one of an Si-element and an Sn-element and a binder. When R represents the average particle diameter of the composite particles in the thickness direction of the electrode layer and d represents the thickness of the electrode layer, the ratio of R to d (R / d) is 0.20 or less.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to an electrode layer and a battery.

Background Art

[0002] In recent years, the development of batteries has been actively carried out. For example, in the automotive industry, the development of batteries used in battery electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid electric vehicles (HEVs) has been promoted. In addition, the development of members and materials used in the above batteries has been advanced.

[0003] For example, Patent Document 1 discloses a negative electrode layer containing composite particles having a plurality of particles containing an Si element or an Sn element and a binder, and having a porosity of 15% or less. Further, Patent Document 2 discloses that in a non-aqueous electrolyte secondary battery, the thickness of the negative electrode active material layer is 2 times or less the average particle diameter of the negative electrode particles.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Si and Sn have a large theoretical capacity and are effective for increasing the energy density of the battery. On the other hand, the volume change amount during charge and discharge is large, and the volume change amount (expansion and contraction amount) of the electrode layer using Si or Sn may increase. If the volume change amount of the electrode is large, the ion conduction path may be cut off and the battery resistance may increase. In this regard, as in Patent Document 1, it has been considered to suppress the volume change amount of the electrode layer by providing voids in the electrode layer, but there is still room for further improvement in terms of volume change.

[0006] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide an electrode layer with a suppressed volume change amount.

Means for Solving the Problems

[0007] [1] An electrode layer containing composite particles, The composite particles contain a plurality of active materials containing Si element or Sn element and a binder, When the average particle diameter of the composite particles in the thickness direction of the electrode layer is R and the thickness of the electrode layer is d, the ratio (R / d) of R to d is 0.20 or less.

[0008] [2] The electrode layer according to [1], wherein R / d is 0.03 or more.

[0009] [3] The electrode layer according to [1] or [2], wherein R is 1 μm or more and 16 μm or less.

[0010] [4] The electrode layer according to any one of [1] to [3], wherein d is 28 μm or more and 81 μm or less.

[0011] [5] The electrode layer according to any one of [1] to [4], wherein the active material contains the Si element and has voids inside.

[0012] [6] The electrode layer according to any one of [1] to [5], wherein the active material contains the Si element and has a silicon clathrate-type crystal phase.

[0013] [7] The electrode layer according to any one of [1] to [6], wherein the electrode layer contains a conductive assistant and a solid electrolyte.

[0014] [8] The electrode layer according to [7], wherein the solid electrolyte is a sulfide solid electrolyte.

[0015] [9] A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, The battery, wherein the negative electrode active material layer is the electrode layer according to any one of [1] to [8].

[0016]

[10] The battery according to [9], wherein the electrolyte layer is a solid electrolyte layer.

Advantages of the Invention

[0017] In the present disclosure, there is an effect that the amount of volume change of the electrode layer can be suppressed.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0019] Hereinafter, the electrode layer and the battery in the present disclosure will be described in detail.

[0020] A. Electrode Layer The electrode layer in the present disclosure contains composite particles. The composite particles contain a plurality of active materials containing Si element or Sn element, and a binder. Further, when the average particle diameter of the composite particles in the thickness direction of the electrode layer is R and the thickness of the electrode layer is d, the ratio (R / d) of R to d is 0.20 or less. Here, in this specification, an active material containing Si element may be referred to as an Si-based active material, and an active material containing Sn element may be referred to as an Sn-based active material.

[0021] According to the present disclosure, since the electrode layer contains predetermined composite particles and R / d is 0.20 or less, an electrode layer with a suppressed volume change amount is obtained.

[0022] When R / d increases, it is assumed that the average particle diameter R of the composite particles in the thickness direction increases. Further, when R / d increases, the number of composite particles arranged in the thickness direction of the electrode layer is assumed to relatively decrease. As a result, in one composite particle, a reaction with carrier ions is likely to occur on the surface on the electrolyte layer side, and a reaction with carrier ions is less likely to occur on the surface on the current collector side. Therefore, reaction unevenness with carrier ions occurs in one composite particle, and the amount of expansion and contraction of the composite particle due to the expansion and contraction of the active material increases.

[0023] On the other hand, in the electrode layer in the present disclosure, since R / d is 0.20 or less, it is presumed that unevenness in reaction in the composite particles can be suppressed, and sufficient ion conduction paths can be secured, thereby suppressing unevenness in reaction in the entire electrode layer. As a result, it is presumed that the volume change amount of the electrode layer is suppressed.

[0024] R / d may be 0.18 or less, may be 0.16 or less, and may be 0.14 or less. On the other hand, R / d may be, for example, 0.02 or more, may be 0.03 or more, may be 0.05 or more, may be 0.08 or more, and may be 0.10 or more. Here, generally, carrier ions move within the electrode layer through the electrolyte portion having good ionic conductivity. That is, the ionic conduction path of the carrier ions bends so as to avoid the composite particle portion. Also, when R / d becomes small, the number of composite particles arranged in the thickness direction of the electrode layer relatively increases. As a result, the composite particles located on the electrolyte layer side are likely to react with carrier ions, and the composite particles located on the current collector side are less likely to react with carrier ions. Therefore, unevenness in reaction may occur in the electrode layer in the thickness direction, and the volume change amount of the entire electrode layer may increase. On the other hand, if R / d is 0.02 or more, the degree of bending of the ionic conduction path can be sufficiently reduced, and unevenness in reaction can be sufficiently suppressed.

[0025] The average particle diameter R of the composite particles is not particularly limited as long as the above R / d is satisfied. R is, for example, 1 μm or more, may be 3 μm or more, and may be 5 μm or more. On the other hand, R is, for example, 16 μm or less, may be 15 μm or less, may be 10 μm or less, and may be 6 μm or less.

[0026] The thickness d of the electrode layer is not particularly limited as long as the above R / d is satisfied. d is, for example, 20 μm or more, may be 28 μm or more, may be 30 μm or more, and may be 50 μm or more. On the other hand, d is, for example, 100 μm or less, may be 90 μm or less, may be 81 μm or less.

[0027] Here, the calculation method of R / d will be described. First, the thickness d of the electrode layer can be obtained by a conventionally known method. For example, a method using an arbitrary thickness gauge, a method of analyzing a cross-sectional image of the electrode layer obtained by microscopic observation, can be mentioned.

[0028] Also, the average particle diameter R of the composite particles can be obtained, for example, by the following method. First, as shown in Fig. 1(a), a cross-sectional image of the electrode layer is acquired by a scanning electron microscope (SEM). Next, as shown in Fig. 1(b), image analysis is performed on the cross-sectional image, and it is binarized into the part of the composite particles (black) and the part other than the composite particles (white). Note that the part of the composite particles and the other part can be distinguished by elemental analysis such as SEM-EDX. Next, as shown in Fig. 1(c), in the binarized image, the part of the composite particles is approximated by an ellipse using image analysis software. Then, as shown in Fig. 1(d), the cross-sectional area of each composite particle approximated by the ellipse is measured, and 50 composite particles are selected in descending order of the cross-sectional area. Then, the average value of the length in the thickness direction of the selected composite particles is obtained as the average particle diameter R of the composite particles.

[0029] The number of composite particles to be selected may be more than 50. The number of composite particles to be selected may be 100 or more. Also, as the observation field of the SEM image, it is preferable to use a field that contains more composite particles than the above-mentioned number. As the observation field of the SEM image, for example, 1000 μm 2 or more and 50000 μm 2 or less. Also, as the image analysis software, for example, ImageJ Fiji can be used.

[0030] From d and R measured and calculated as described above, R / d is calculated.

[0031] 1. Composite Particles The composite particles in the present disclosure contain a plurality of active materials containing Si element or Sn element and a binder. Note that the composite particles can be regarded as an aggregate in which a plurality of the above-mentioned active materials (Si-based active material or Sn-based active material) are aggregated. Note that the above-mentioned active material may be a primary particle or a secondary particle in which primary particles are aggregated.

[0032] The average particle diameter r (D 50) is not particularly limited, but for example, it is 0.1 μm or more and 3 μm or less. The average particle diameter (D 50 ) refers to the volume cumulative particle diameter measured by a laser diffraction scattering type particle size distribution measuring device. The number of the above active substances contained in the composite active substance is, for example, 10 or more and 150 or less.

[0033] The active substance containing Si element (Si-based active substance) may be single Si, an alloy containing Si as a main component (Si alloy), or a Si oxide. The proportion of Si element in the Si alloy is, for example, 50 mol% or more and 95 mol% or less.

[0034] Further, the Si-based active substance may have voids inside. The Si-based active substance having voids is referred to as porous Si. Having voids can be confirmed by SEM (scanning electron microscope) observation. The porosity is not particularly limited, but for example, it is 4% or more, and may be 10% or more. Further, the above porosity is, for example, 40% or less, and may be 20% or less. The porosity can be obtained, for example, by the following procedure. First, a cross-sectional image of the Si-based active substance is acquired by SEM. From the obtained image, the silicon part and the void part are distinguished using image analysis software and binarized. The areas of the silicon part and the void part are obtained, and the porosity (%) is calculated from the following formula. Porosity (%) = 100×(void part area) / ((silicon part area)+(void part area))

[0035] In porous Si, the void volume of voids with a pore diameter of 50 nm or less is, for example, 0.05 cc / g or more and 0.30 cc / g or less. The BET specific surface area of porous Si is, for example, 20 m 2 / g or more and 200 m 2 / g or less.

[0036] As a method for producing porous Si, for example, a method of producing an alloy of Li and Si (LiSi alloy) and then removing Li from the LiSi alloy can be mentioned. The LiSi alloy can be obtained, for example, by mixing Li and Si. As a method for removing Li from the LiSi alloy, for example, a method of reacting the LiSi alloy with a Li extraction material can be mentioned. Examples of the Li extraction material include alcohols such as methanol and acids such as acetic acid.

[0037] Here, FIG. 2 is a schematic perspective view for explaining the crystal phase of Si. Generally, Si has a diamond-type crystal phase as shown in FIG. 2(a). In contrast, the Si-based active material in the present disclosure may have a silicon clathrate-type crystal phase as shown in FIGS. 2(b) and (c). In the diamond-type crystal phase shown in FIG. 2(a), tetrahedrons are formed by a plurality of Si elements. The tetrahedron does not have a space inside that can enclose metal ions such as Li ions. On the other hand, the silicon clathrate type I and II crystal phases shown in FIGS. 2(b) and (c) have a cage-like structure (cage) of skeletal atoms, and metal ions such as Li ions can enter therein, so that the expansion and contraction of the composite particles can be more suppressed, and as a result, the expansion and contraction of the electrode layer can be more suppressed. The Si-based active material having a silicon clathrate-type crystal phase is referred to as clathrate Si, and in particular, the Si-based active material having the above voids and a clathrate-type crystal phase is referred to as porous clathrate Si (pc-Si).

[0038] The Si-based active material may have a silicon clathrate type I crystal phase or a silicon clathrate type II crystal phase. In particular, it is preferable that the Si-based active material has a silicon clathrate type II crystal phase as the main phase. The "main phase" means that the peak belonging to the crystal phase has the largest diffraction intensity among the peaks observed by X-ray diffraction measurement. The proportion of the silicon clathrate type II crystal phase contained in the Si-based active material is, for example, 80% by weight or more, and may be 85% by weight or more, 90% by weight or more, or 95% by weight or more. Also, the proportion of the silicon clathrate type II crystal phase contained in the Si-based active material may be 100% by weight or less than 100% by weight. The proportion of the crystal phase can be determined by using the RIR method (Reference Intensity Ratio method).

[0039] As a method for producing porous clathrate Si, for example, the above-mentioned porous Si and a Na source such as NaH are mixed and heated to produce a Na-Si alloy, and by heating the Na-Si alloy, the amount of Na in the Na-Si alloy is reduced to generate a silicon clathrate type crystal phase. A method can be mentioned.

[0040] The active material containing the Sn element (Sn-based active material) may be elemental Sn, an alloy (Sn alloy) containing Sn as the main component, or a Sn oxide. The proportion of the Sn element in the Sn alloy is, for example, 50 mol% or more and 95 mol% or less.

[0041] The proportion of the above Si-based active material or Sn-based active material in the composite particles is, for example, 90% by weight or more and 99% by weight or less.

[0042] The binder in the present disclosure is not particularly limited. Examples of the binder include polyimide-based binders; rubber-based binders such as amine-modified butadiene rubber (ABR), butadiene rubber (BR), and styrene-butadiene rubber (SBR); cellulose-based binders such as carboxymethyl cellulose (CMC); acrylic-based binders such as polyacrylic acid, polyacrylate, and polyacrylate ester; and fluoride-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Only one type of binder may be used, or a plurality of types may be mixed and used.

[0043] The proportion of the binder in the composite particles is, for example, 0.5% by weight or more and 10% by weight or less.

[0044] Here, in the electrode layer, the aspect ratio of the composite particles is, for example, 3.6 or less, may be 3.5 or less, may be 3.3 or less, may be 3.0 or less, or may be 2.8 or less. On the other hand, the aspect ratio is, for example, 1.5 or more, may be 1.6 or more, may be 1.8 or more, may be 2.0 or more, may be 2.3 or more, or may be 2.5 or more. The aspect ratio of the composite particles is the ratio (b / a) of the major axis b to the minor axis a of the composite active material obtained when the cross-sectional shape of the composite active material in the electrode layer is approximated to an ellipse. Also, it is assumed that the electrode layer is produced by applying a pressing pressure. That is, it is assumed that the composite particles are contained in the electrode layer in a compressed state in the thickness direction of the electrode layer. Therefore, the minor axis a of the composite particles can be regarded as the length of the composite particles in the thickness direction of the electrode layer (the vertical direction of the paper surface in FIG. 1). Also, the major axis b of the composite particles can be regarded as the length of the composite particles in the direction intersecting the thickness direction of the electrode layer (the left-right direction of the paper surface in FIG. 1).

[0045] Here, similar to the above-described R / d, the aspect ratio can be obtained from the cross-sectional SEM image of the electrode layer. As shown in FIGS. 1(a) to 1(c), in the binarized SEM image, the portion of the composite particles is approximated by an ellipse using image analysis software. Then, for each of the composite active materials approximated by the ellipse, the minor axis, major axis, and area are measured, and 10 composite active materials are selected in descending order of cross-sectional area. The aspect ratio (major axis / minor axis) is measured from the minor axis and major axis of each selected composite active material, and the average value of the measured aspect ratios is obtained as the aspect ratio in the present disclosure. Note that the number of composite particles to be selected may be more than 10.

[0046] The proportion of the composite particles in the electrode layer is, for example, 50% by weight or more, and may be 70% by weight or more, or may be 90% by weight or more. On the other hand, the proportion of the composite particles is, for example, 99% by weight or less, and may be 95% by weight or less.

[0047] The composite particles can be produced, for example, as follows. First, a slurry containing the above-described Si-based active material or Sn-based active material and a binder is prepared. Then, the composite particles can be obtained by spraying the slurry into hot air by a spray drying method and drying it. Here, the above R in the composite particles can be adjusted, for example, by changing the solid content ratio of the slurry and the conditions in the spray drying method such as the spray pressure. The solid content ratio of the slurry is, for example, 0.5% by weight or more and 35% by weight or less. The spray pressure is, for example, 0.03 MPa or more and 0.20 MPa or less.

[0048] 2. Electrode layer The electrode layer may be a positive electrode active material layer containing the above composite particles as a positive electrode active material, or may be a negative electrode active material layer containing the above composite particles as a negative electrode active material, but the latter is preferred. This is because a high-voltage battery can be obtained. Further, the electrode layer may further contain at least one of a conductive assistant, a binder, and an electrolyte, if necessary.

[0049] Examples of the conductive aid include carbon materials. Examples of the carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB); fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). The proportion of the conductive aid in the electrode layer is, for example, 0.01% by weight or more and 10% by weight or less, and may be 0.1% by weight or more and 5% by weight or less.

[0050] Examples of the binder include the binders described in "1. Composite Particles". The binder in the composite particles and the binder in the electrode layer may be of the same type or different types. The proportion of the binder in the electrode layer is, for example, 0.5% by weight or more and 10% by weight or less, and may be 1% by weight or more and 5% by weight or less.

[0051] The electrode layer preferably contains a solid electrolyte as the electrolyte. Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. The sulfide solid electrolyte preferably contains sulfur (S) as the main component of the anion element. The oxide solid electrolyte preferably contains oxygen (O) as the main component of the anion element. The halide solid electrolyte preferably contains a halogen as the main component of the anion. Among these, the sulfide solid electrolyte is preferred.

[0052] The sulfide solid electrolyte preferably contains a Li element, an M element (M is at least one of P, Sn, Al, Zn, In, Ge, Si, Sb, Ga, and Bi), and an S element. The sulfide solid electrolyte may also contain a halogen element such as F, Cl, Br, or I. In the sulfide solid electrolyte, a part of the S element may be substituted with an O element.

[0053] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. Examples of the crystal phase contained in the sulfide solid electrolyte include an LGPS-type crystal phase, a Thio-LISICON-type crystal phase, and an argyrodite-type crystal phase.

[0054] Examples of the sulfide solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers. Z is either Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers. M is either P, Si, Ge, B, Al, Ga, or In).

[0055] The proportion of the solid electrolyte in the electrode layer is, for example, 30% by weight or more and 80% by weight or less, and may be 40% by weight or more and 70% by weight or less.

[0056] B. Battery FIG. 3 is a schematic cross-sectional view illustrating the battery in the present disclosure. The battery 10 shown in FIG. 3 includes a positive electrode active material layer 1, a negative electrode active material layer 2, and an electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2. Further, the negative electrode active material layer 2 in the battery 10 is the electrode layer in the present disclosure described above.

[0057] 1. Positive Electrode Active Material Layer The positive electrode active material layer contains at least a positive electrode active material, and optionally contains at least one of a conductive assistant, a binder, and an electrolyte. The conductive assistant, the binder, and the electrolyte are the same as those described in "A. Electrode Layer".

[0058] The positive electrode active material is not particularly limited as long as it is an active material having a reaction potential higher than that of the above composite particles. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layer-structured active materials such as LiCoO2, LiNi 0.8 Co 0.15 Mn 0.05 O2 and LiNi 0.33 Co 0.33 Mn 0.33 O2, spinel-type active materials such as LiMn2O4, Li4Ti5O 12 and olivine-type active materials such as LiFePO4. Examples of the shape of the positive electrode active material include particulate form. The average particle diameter (D 50 ) is, for example, 0.5 μm or more and 50 μm or less. The average particle diameter (D 50 ) is as described above.

[0059] The thickness of the positive electrode active material layer is not particularly limited, but is, for example, 0.1 μm or more and 1000 μm or less.

[0060] 2. Negative electrode active material layer The negative electrode active material layer is the above-described electrode layer. The electrode layer is the same as that described in "A. Electrode Layer".

[0061] 3. Electrolyte layer The electrolyte layer contains an electrolyte. The electrolyte is preferably a solid electrolyte. The solid electrolyte is the same as that described in the above "A. Electrode Layer". Further, the electrolyte layer may optionally contain a binder. The binder is the same as that described in "A. Electrode Layer". In the present disclosure, an electrolyte layer containing a solid electrolyte is referred to as a solid electrolyte layer, and a battery including the solid electrolyte layer is referred to as an all-solid-state battery.

[0062] The thickness of the electrolyte layer is not particularly limited, and is, for example, 0.1 μm or more and 1000 μm or less.

[0063] 4. Other Configurations As shown in FIG. 3, the battery 10 in the present disclosure typically has a positive electrode current collector 4 that collects electrons from the positive electrode active material layer 1 and a negative electrode current collector 5 that collects electrons from the negative electrode active material layer 2. Examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material of the negative electrode current collector include SUS, copper, nickel, and carbon.

[0064] In addition, the battery in the present disclosure may include an exterior body that houses the above-described members. Examples of the exterior body include a laminate-type exterior body and a case-type exterior body. Further, the battery in the present disclosure may include a restraining jig that applies a restraining pressure in the thickness direction to the above-described members. A known jig can be used as the restraining jig. The restraining pressure is, for example, 0.1 MPa or more and 50 MPa or less, and may be 1 MPa or more and 20 MPa or less.

[0065] 5. Battery The battery in the present disclosure is typically a lithium-ion secondary battery. Further, the battery in the present disclosure is preferably an all-solid-state battery having a solid electrolyte layer as the electrolyte layer. Examples of the use of the battery include a power source for vehicles such as hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), electric vehicles (BEV), gasoline vehicles, and diesel vehicles. Further, the battery in the present disclosure may be used as a power source for moving bodies other than vehicles (e.g., railways, ships, aircraft), and may also be used as a power source for electrical products such as information processing devices.

[0066] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has a configuration substantially the same as the technical idea described in the claims of the present disclosure and exhibits the same operational effects is included in the technical scope of the present disclosure.

Examples

[0067] [Example 1] (Fabrication of the positive electrode) A binder (PVDF), a conductive additive, a sulfide solid electrolyte, and a positive electrode active material (NCM: LiNi 0.8 Co 0.15 Mn 0.05 O2) were added to an organic solvent. After the addition, kneading was performed using an ultrasonic homogenizer to obtain a positive electrode slurry. The positive electrode slurry was applied to a positive electrode current collector (Al foil) and dried. Thereby, a positive electrode having a positive electrode current collector and a positive electrode active material layer was obtained.

[0068] (Fabrication of the negative electrode) To a binder solution containing an organic solvent and a binder (PVDF), a Si-based active material (pc-Si: average particle diameter (D 50 ) 0.5 μm) was introduced and mixed to obtain an active material slurry. Composite particles containing a Si-based active material and a binder were fabricated by a spray drying method using the active material slurry.

[0069] A composite particle, a binder (PVDF), a conductive additive (VGCF), and a sulfide solid electrolyte (Li2S-P2S5-based sulfide solid electrolyte) were added to an organic solvent and kneaded using an ultrasonic homogenizer. Thereby, a negative electrode slurry was fabricated. The negative electrode slurry was applied to a negative electrode current collector (Cu foil) and dried so that the thickness d of the electrode layer became the value shown in Table 1. Thereby, a negative electrode having a negative electrode current collector and a negative electrode active material layer was obtained.

[0070] (Fabrication of the evaluation battery) A binder (PVDF) and a sulfide solid electrolyte (Li2S-P2S5-based sulfide solid electrolyte) were added to an organic solvent and kneaded using an ultrasonic homogenizer. Thereby, a composite material slurry was obtained. The composite material slurry was applied to a substrate (Al foil) and dried. Thereby, a transfer member having a substrate and a solid electrolyte layer was obtained.

[0071] The fabricated positive electrode, negative electrode, and transfer member were each formed into strip shapes. Next, the positive electrode and the transfer member were stacked so that the positive electrode active material layer and the solid electrolyte layer faced each other, and roll-pressed at 165°C under a pressure of 50 kN / cm. Thereafter, the substrate was peeled off to obtain a positive electrode side member. Also, the negative electrode and the transfer member were stacked so that the negative electrode active material layer and the solid electrolyte layer faced each other, and roll-pressed at 25°C under a pressure of 50 kN / cm. Thereafter, the substrate was peeled off to obtain a negative electrode side member. Next, the negative electrode side member was punched out to a diameter of φ13.00 mm, and the positive electrode side member was punched out to a diameter of φ11.28 mm. A powdered sulfide solid electrolyte was placed on the solid electrolyte layer of the punched-out negative electrode side member and uniaxially pressed. Next, the negative electrode side member and the positive electrode side member were stacked so that the solid electrolyte layers faced each other, and tabs for current extraction were attached to the positive electrode and the negative electrode. Then, this was enclosed in an aluminum laminate using a vacuum laminator and constrained under a pressure of 5 MPa. Thereby, an evaluation battery (all-solid-state battery) was fabricated.

[0072] SEM observation was performed on the fabricated evaluation battery, and a cross-sectional SEM image of the negative electrode active material layer was obtained. From the cross-sectional SEM image of the negative electrode active material layer by the method described above, the average particle diameter R of the composite particles and the thickness d of the electrode layer were obtained, and R / d was calculated. The results are shown in Table 1.

[0073] [Examples 2 to 13 and Comparative Examples 1 to 5] Composite particles were fabricated by changing the solid content ratio of the slurry and changing the spray pressure in the spray drying method. Using these composite particles and changing the coating amount of the negative electrode slurry, an evaluation battery equipped with a negative electrode having R / d shown in Table 1 was fabricated.

[0074] [Evaluation] Each fabricated evaluation battery was charged, and the increase in the constraint pressure measured using a load cell was evaluated as the electrode expansion amount. The results are shown in Table 1 and FIG. 4. Note that the increase in the constraint pressure (electrode expansion amount) of Comparative Example 1 was taken as 100% and evaluated relatively.

[0075]

Table 1

[0076] As shown in Table 1 and FIG. 4, the amount of electrode expansion was suppressed in any of the examples as compared with the comparative examples. In particular, in the range where R / d was 0.03 or more and 0.20 or less, the amount of electrode expansion was remarkably suppressed.

Explanation of Signs

[0077] 1... Positive electrode active material layer 2... Negative electrode active material layer 3... Electrolyte layer 4... Positive electrode current collector 5... Negative electrode current collector 10... Battery

Claims

1. An electrode layer containing composite particles, wherein the composite particles contain a plurality of active materials containing Si element or Sn element and a binder, wherein when the average particle diameter of the composite particles in the thickness direction of the electrode layer is R and the thickness of the electrode layer is d, the ratio (R / d) of R to d is 0.20 or less. The electrode layer.

2. The electrode layer according to claim 1, wherein R / d is 0.03 or more.

3. The electrode layer according to claim 1, wherein R is 1 μm or more and 16 μm or less.

4. The electrode layer according to claim 1, wherein d is 28 μm or more and 81 μm or less.

5. The electrode layer according to claim 1, wherein the active material contains the Si element and has voids inside.

6. The electrode layer according to claim 1, wherein the active material contains the Si element and has a silicon clathrate-type crystal phase.

7. The electrode layer according to claim 1, wherein the electrode layer contains a conductive assistant and a solid electrolyte.

8. The electrode layer according to claim 7, wherein the solid electrolyte is a sulfide solid electrolyte.

9. A battery having a positive electrode active material layer, a negative electrode active material layer, and an electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer is the electrode layer according to any one of claims 1 to 8. The battery.

10. The battery according to claim 9, wherein the electrolyte layer is a solid electrolyte layer.

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