Electrode layer and battery

Abstract

The invention relates to an electrode layer and a battery. The main purpose of the present invention is to provide an electrode layer in which the volume change is suppressed. The present disclosure solves the problem by providing an electrode layer containing composite particles, the composite particles containing a binder and a plurality of active materials containing elemental Si or elemental Sn, the average particle diameter of the composite particles in the thickness direction of the electrode layer being R, and the thickness of the electrode layer being d, R being the average particle diameter of the composite particles in the thickness direction of the electrode layer, and d being the average particle diameter of the composite particles in the thickness direction of the electrode layer. And the ratio (R / d) of the R to the d is 0.20 or less.

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 for battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs) has been promoted. In addition, the development of components and materials for the above batteries has been promoted.

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

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-121557

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-146104 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Si and Sn have a large theoretical capacity and are effective for increasing the energy density of the battery. However, the volume change during charge and discharge is large, and the volume change amount (expansion / contraction amount) of the electrode layer using Si or Sn may become large. If the volume change amount of the electrode layer 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 studied to provide voids in the electrode layer to suppress the volume change amount of the electrode layer, but there is still room for further improvement regarding the volume change.

[0010] In view of the above actual situation, the present disclosure has been completed, and the main object thereof is to provide an electrode layer in which the volume change amount is suppressed.

[0011] Means for Solving the Problems

[0012] [1] An electrode layer is an electrode layer containing composite particles. The composite particles contain: a plurality of active materials containing an Si element or an Sn element and a binder. When the average particle diameter of the composite particles in the thickness direction of the electrode layer is set to R and the thickness of the electrode layer is set to d, the ratio R / d of R to d is 0.20 or less.

[0013] [2] The electrode layer according to [1], wherein R / d is 0.03 or more.

[0014] [3] The electrode layer according to [1] or [2], wherein R is 1 μm or more and 16 μm or less.

[0015] [4] The electrode layer according to any one of [1] to [3], wherein d is 28 μm or more and 81 μm or less.

[0016] [5] The electrode layer according to any one of [1] to [4], wherein the active material contains the Si element and has voids inside.

[0017] [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.

[0018] [7] The electrode layer according to any one of [1] to [6], wherein the electrode layer contains a conductive additive and a solid electrolyte.

[0019] [8] The electrode layer according to [7], wherein the solid electrolyte is a sulfide solid electrolyte

[0020] [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 [1] to [8].

[0021]

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

[0022] Effects of the Invention

[0023] The present disclosure achieves the effect of being able to suppress the volume change amount of the electrode layer. Description of the Drawings

[0024] Figure 1 A diagram for explaining the calculation method of R / d in the present disclosure.

[0025] Figure 2 A diagram for explaining the crystal phase of the Si-based active material in the present disclosure.

[0026] Figure 3 A schematic cross-sectional view illustrating the battery in the present disclosure.

[0027] Figure 4 A coordinate diagram showing the results of the examples and comparative examples.

[0028] Description of Reference Numerals

[0029] 1…Positive electrode active material layer

[0030] 2…Negative electrode active material layer

[0031] 3…Electrolyte layer

[0032] 4…Positive electrode current collector

[0033] 5…Negative electrode current collector

[0034] 10…Battery Detailed implementation manners

[0035] The electrode layers and batteries in the present disclosure will be described in detail below.

[0036] A. Electrode layer

[0037] The electrode layer in the present disclosure contains composite particles. The above composite particles contain: a binder, and a plurality of active materials containing Si element or Sn element. In addition, when the average particle diameter of the above composite particles in the thickness direction of the above electrode layer is set as R and the thickness of the above electrode layer is set as d, the ratio (R / d) of the above R to the above d is 0.20 or less. Herein, in the present specification, the active material containing Si element is sometimes referred to as Si-based active material, and the active material containing Sn element is sometimes referred to as Sn-based active material.

[0038] According to the present disclosure, since the electrode layer contains the specified composite particles and R / d is 0.20 or less, the electrode layer with the volume change amount suppressed is obtained.

[0039] It is assumed that if R / d becomes larger, the average particle diameter R of the composite particles in the thickness direction will become larger. In addition, it is assumed that if R / d becomes larger, the number of composite particles arranged in the thickness direction of the electrode layer will relatively decrease. As a result, in one composite particle, the reaction with the ion carrier is likely to occur on the surface on the electrolyte layer side, and the reaction with the ion carrier is difficult to occur on the surface on the current collector side. Therefore, in one composite particle, the reaction unevenness with the ion carrier occurs, and the expansion and contraction amount of the composite particles due to the expansion and contraction of the active material becomes larger.

[0040] In the electrode layer in the present disclosure, it is speculated that since R / d is 0.20 or less, the reaction unevenness in the composite particles can be suppressed, and since a sufficient ion conduction path can be ensured, the reaction unevenness in the entire electrode layer can be suppressed. As a result, it is speculated that the volume change amount of the electrode layer is suppressed.

[0041] R / d can be 0.18 or less, can be 0.16 or less, can be 0.14 or less. On the other hand, R / d is, for example, 0.02 or more, can be 0.03 or more, can be 0.05 or more, can be 0.08 or more, can be 0.10 or more. Among them, generally, the charge carriers move within the electrode layer through the electrolyte portion with good ionic conductivity. That is, the ionic conduction path of the charge carriers bends in a way to avoid the composite particle portion. In addition, if R / d becomes smaller, the number of composite particles arranged in the thickness direction of the electrode layer relatively increases. As a result, the composite particles on the electrolyte layer side are likely to react with the charge carriers, and the composite particles on the current collector side are difficult to react with the charge carriers. Therefore, reaction non-uniformity occurs in the electrode layer in the thickness direction, and the volume change amount of the entire electrode layer may become large. If R / d is 0.02 or more, the curvature of the ionic conduction path can be made small enough, and the non-uniformity of the reaction can be sufficiently suppressed.

[0042] The average particle diameter R of the composite particles is not particularly limited as long as the above-mentioned R / d is satisfied. R is, for example, 1 μm or more, can be 3 μm or more, can be 5 μm or more. On the other hand, R is, for example, 16 μm or less, can be 15 μm or less, can be 10 μm or less, can be 6 μm or less.

[0043] The thickness d of the electrode layer is not particularly limited as long as the above-mentioned R / d is satisfied. d is, for example, 20 μm or more, can be 28 μm or more, can be 30 μm or more, can be 50 μm or more. On the other hand, d is, for example, 100 μm or less, can be 90 μm or less, can be 81 μm or less.

[0044] Here, the calculation method of R / d will be described. First, for the thickness d of the electrode layer, a conventionally well-known method can be used to obtain it. For example, a method using an arbitrary thickness gauge and a method of analyzing the cross-sectional image of the electrode layer obtained by microscopic observation can be cited.

[0045] In addition, for the average particle diameter R of the composite particles, for example, the following method can be used to obtain it. First, as shown in Figure 1 (a), a cross-sectional image of the electrode layer is obtained using a scanning electron microscope (SEM). Secondly, as shown in Figure 1 (b), the cross-sectional image is subjected to image analysis and binarized with the composite particle portion (black) and the portion other than the composite particles (white). It should be noted that the composite particle portion and other portions can be distinguished by, for example, elemental analysis such as SEM-EDX. Secondly, as shown in Figure 1 (c), in the binarized image, the composite particle portion is approximated as an ellipse using image analysis software. Then, as shown in Figure 1As shown in (d), the cross-sectional area of each composite particle approximately elliptical is measured, and 50 composite particles are selected in the order of the largest 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 size R of the composite particles.

[0046] The number of selected composite particles may be more than 50. The number of selected composite particles may be more than 100. In addition, the observation field of the SEM image is preferably a field containing composite particles of the above number or more. The observation field of the SEM image is, for example, 1000 μm. 2 Above and 50000μm 2 In addition, as image analysis software, for example, ImageJ Fiji can be used.

[0047] From d and R measured and calculated as described above, R / d is calculated.

[0048] 1. Composite particles

[0049] The composite particles in the present disclosure contain: a plurality of active materials containing Si element or Sn element, and a binder. Furthermore, the composite particles can be regarded as aggregates formed by the aggregation of a plurality of the above active materials (Si-based active materials or Sn-based active materials). Furthermore, the above active materials can be primary particles or secondary particles formed by the aggregation of primary particles.

[0050] The average particle size r(D 50 ) is not particularly limited, and is, for example, 0.1 μm or more and 3 μm or less. The average particle size (D 50 ) refers to the volume cumulative particle size measured using a laser diffraction scattering particle size distribution measuring device. The number of the active material contained in the composite particles is, for example, 10 or more and 150 or less.

[0051] The active material containing Si element (Si-based active material) may be Si single substance, an alloy containing Si as a main component (Si alloy), or Si oxide. The proportion of Si element in the Si alloy is, for example, 50 mol% or more and 95 mol% or less.

[0052] In addition, the Si-based active material may have voids inside. Furthermore, the Si-based active material having voids is referred to as porous Si. Regarding whether there are voids, it can be confirmed by SEM (scanning electron microscope) observation. In addition, the porosity is not particularly limited, for example, it is 4% or more and can be 10% or more. In addition, the above porosity is, for example, 40% or less and can be 20% or less. The porosity can be obtained, for example, by the following steps. First, a cross-sectional image of the Si-based active material is obtained using SEM. From the obtained image, using image analysis software, the silicon part and the void part are distinguished and binarized. The areas of the silicon part and the void part are obtained, and the porosity (%) is calculated by the following formula.

[0053] Porosity (%) = 100 × (void part area) / ((silicon part area) + (void part area))

[0054] In the porous Si, the void volume of the 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. In addition, the BET specific surface area of the porous Si is, for example, 20 m 2 / g or more and 200 m 2 / g or less.

[0055] As a method for producing the porous Si, for example, the following method can be cited: producing an alloy of Li and Si (LiSi alloy), and then removing Li from the LiSi alloy. The LiSi alloy is 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 cited. As the Li extraction material, for example, alcohols such as methanol and acids such as acetic acid can be cited.

[0056] Among them, Figure 2 is a schematic three-dimensional diagram for explaining the crystal phase of Si. Generally, Si has Figure 2 the diamond-type crystal phase shown in (a). And the Si-based active material in the present disclosure may have Figure 2 the silicon clathrate-type crystal phases shown in (b) and (c). In Figure 2 the diamond-type crystal phase shown in (a), tetrahedrons are formed using a plurality of Si elements. There is no space inside the tetrahedron that can accommodate metal ions such as Li ions. On the other hand, Figure 2The skeleton atoms of the silicon inclusion type I and II crystal phases shown in (b) and (c) have a cage-type structure (cage), and since metal ions such as Li ions can enter therein, the expansion and contraction of the composite particles can be further suppressed, and as a result, the expansion and contraction of the electrode layer can be further suppressed. In addition, Si-based active materials having a silicon inclusion type crystal phase are called inclusion Si, and in particular, Si-based active materials having the above-mentioned voids and an inclusion type crystal phase are called porous inclusion Si (pc-Si).

[0057] The Si-based active material may have a silicon inclusion compound type I crystal phase, or may have a silicon inclusion compound type II crystal phase. In particular, the Si-based active material preferably has a silicon inclusion compound type II crystal phase as the main phase. The so-called "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 inclusion compound type II crystal phase contained in the Si-based active material is, for example, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. In addition, the proportion of the silicon inclusion compound 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 obtained by using the RIR method (Reference Intensity Ratio method).

[0058] As a method for producing porous inclusion Si, for example, the following method can be listed: the above-mentioned porous Si is mixed with a Na source such as NaH and heated to produce a Na-Si alloy, and the Na-Si alloy is heated to reduce the amount of Na in the Na-Si alloy to generate a silicon inclusion type crystal phase.

[0059] The active material containing the Sn element (Sn-based active material) may be a single substance of Sn, an alloy containing Sn as a main component (Sn alloy), 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.

[0060] The ratio of the Si-based active material or the Sn-based active material in the composite particles is, for example, 90% by weight or more and 99% by weight or less.

[0061] The adhesive in the present disclosure is not particularly limited. Examples of the adhesive include polyimide-based adhesives; rubber-based adhesives such as amine-modified butadiene rubber (ABR), butadiene rubber (BR), and styrene butadiene rubber (SBR); cellulose-based adhesives such as carboxymethyl cellulose (CMC); acrylic-based adhesives such as polyacrylic acid, polyacrylic acid salts, and polyacrylic esters; and fluoride-based adhesives such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). The adhesive may be used alone or in combination.

[0062] The proportion of the binder in the composite particles is, for example, 0.5% by weight or more and 10% by weight or less.

[0063] Among them, in the electrode layer, the aspect ratio of the composite particles is, for example, 3.6 or less, can be 3.5 or less, can be 3.3 or less, can be 3.0 or less, can be 2.8 or less. On the other hand, the aspect ratio is, for example, 1.5 or more, can be 1.6 or more, can be 1.8 or more, can be 2.0 or more, can be 2.3 or more, can be 2.5 or more. Further, the aspect ratio of the composite particles refers to the ratio (b / a) of the major axis b to the minor axis a of the composite particles obtained when the cross-sectional shape of the composite particles in the electrode layer is approximated as an ellipse. In addition, it is assumed that the electrode layer is fabricated by applying a pressing pressure. That is, it is assumed that the composite particles are included 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 ( Figure 1 the up-and-down direction of the paper surface in the figure) of the electrode layer. In addition, the major axis b of the composite particles can be regarded as the length of the composite particles in the direction ( Figure 1 the left-and-right direction of the paper surface in the figure) intersecting the thickness direction of the electrode layer.

[0064] Among them, similar to the above R / d, the above aspect ratio can be obtained from the cross-sectional SEM image of the electrode layer. As Figure 1 shown in (a) to (c), in the binarized SEM image, using image analysis software, the part of the composite particles is approximated as an ellipse. Then, for each composite particle approximated as an ellipse, the minor axis, major axis, and area are measured, and 10 composite particles are selected in the order of the largest cross-sectional area. From the minor axis and major axis of each selected composite particle, the aspect ratio (major axis / minor axis) is measured, and the average value of the measured aspect ratios is taken as the aspect ratio in the present disclosure. Further, the number of selected composite particles can be more than 10.

[0065] The proportion of the composite particles in the electrode layer is, for example, 50% by weight or more, can be 70% by weight or more, can be 90% by weight or more. On the other hand, the proportion of the composite particles is, for example, 99% by weight or less, can be 95% by weight or less.

[0066] The composite particles can be fabricated as follows. First, a slurry containing the above-mentioned Si-based active material or Sn-based active material and a binder is prepared. Then, the above slurry is sprayed in hot air using a spray drying method and dried to obtain the above composite particles. Among them, the above R in the composite particles can be adjusted by changing conditions in the spray drying method such as the solid content fraction (solid component ratio) of the slurry and the spray pressure. The solid content fraction of the slurry is, for example, 0.5% by weight or more and 35% by weight or less. In addition, the spray pressure is, for example, 0.03 MPa or more and 0.20 MPa or less.

[0067] 2. Electrode layer

[0068] The electrode layer may be a positive electrode active material layer containing the above composite particles as the positive electrode active material, or may be a negative electrode active material layer containing the above composite particles as the negative electrode active material, and the latter is preferred. This is because a battery with a high voltage can be obtained. In addition, the electrode layer may further contain at least one of a conductive aid, a binder, and an electrolyte as needed.

[0069] As the conductive aid, for example, carbon materials can be cited. As the carbon materials, for example, particulate carbon materials such as acetylene black (AB) and Ketjen black (KB); fibrous carbon materials such as carbon fiber, carbon nanotube (CNT), and carbon nanofiber (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.

[0070] For the binder, the binders described in "1. Composite particles" can be cited. 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.

[0071] The electrode layer preferably contains a solid electrolyte as the electrolyte. As the solid electrolyte, for example, inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes can be cited. 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, a sulfide solid electrolyte is preferred.

[0072] The sulfide solid electrolyte preferably contains Li element, M element (M is at least one of P, Sn, Al, Zn, In, Ge, Si, Sb, Ga, and Bi), and S element. In addition, the sulfide solid electrolyte may contain halogen elements such as F, Cl, Br, and I. In addition, in the sulfide solid electrolyte, a part of the S element may be replaced by the O element.

[0073] The sulfide solid electrolyte may be a glassy (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. As the crystal phase contained in the sulfide solid electrolyte, for example, LGPS-type crystal phase, Thio-LISICON-type crystal phase, and argyrodite-type crystal phase can be cited.

[0074] As the sulfide solid electrolyte, for example, 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 any one of Ge, Zn, and Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.).

[0075] 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 can be 40% by weight or more and 70% by weight or less.

[0076] B. Battery

[0077] Figure 3 is a schematic cross-sectional view of the battery in the present disclosure for illustration. Figure 3 The battery 10 shown has 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. In addition, the negative electrode active material layer 2 in the battery 10 is the electrode layer in the present disclosure described above.

[0078] 1. Positive electrode active material layer

[0079] The positive electrode active material layer contains at least a positive electrode active material, and optionally contains at least one of a conductive additive, a binder, and an electrolyte. For the conductive additive, the binder, and the electrolyte, the content is the same as that described in "A. Electrode layer".

[0080] 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. As the positive electrode active material, for example, oxide active materials can be cited. As the oxide active materials, for example, LiCoO2, LiNi 0.8 Co 0.15 Mn 0.05 O2 and LiNi 0.33 Co 0.33 Mn 0.33Rock salt layer-type active materials such as O2; spinel-type active materials such as LiMn2O4, Li4Ti5O 12 ; and olivine-type active materials such as LiFePO4. As the shape of the positive electrode active material, for example, particulate form can be cited. 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.

[0081] There is no particular limitation on the thickness of the positive electrode active material layer, and it is, for example, 0.1 μm or more and 1000 μm or less.

[0082] 2. Negative electrode active material layer

[0083] The negative electrode active material layer is the above-described electrode layer. For the electrode layer, it is the same as the content described in "A. Electrode layer".

[0084] 3. Electrolyte layer

[0085] The electrolyte layer contains an electrolyte. The electrolyte is preferably a solid electrolyte. For the solid electrolyte, it is the same as the content described in the above "A. Electrode layer". In addition, the electrolyte layer may contain a binder as needed. For the binder, it is the same as the content described in "A. Electrode layer". Further, in the present disclosure, the electrolyte layer containing a solid electrolyte is referred to as a solid electrolyte layer, and the battery including the solid electrolyte layer is referred to as an all-solid battery.

[0086] There is no particular limitation on the thickness of the electrolyte layer, and it is, for example, 0.1 μm or more and 1000 μm or less.

[0087] 4. Other components

[0088] As Figure 3 shown, the battery 10 in the present disclosure generally has a positive electrode current collector 4 that collects electrons of the positive electrode active material layer 1 and a negative electrode current collector 5 that collects electrons of the negative electrode active material layer 2. As the material of the positive electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be cited. As the material of the negative electrode current collector, for example, SUS, copper, nickel, and carbon can be cited.

[0089] In addition, the battery in the present disclosure may include an outer package that houses the above-described components. As the outer package, for example, a laminated outer package and a case-type outer package can be cited. In addition, the battery in the present disclosure may include a constraint jig that applies a constraint pressure in the thickness direction to the above-described components. As the constraint jig, a known jig can be used. The constraint pressure is, for example, 0.1 MPa or more and 50 MPa or less, and can be 1 MPa or more and 20 MPa or less.

[0090] 5. Battery

[0091] The batteries in the present disclosure are typically lithium-ion secondary batteries. Additionally, the batteries in the present disclosure are preferably all-solid-state batteries having a solid electrolyte layer as the electrolyte layer. As applications of the batteries, for example, power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles can be cited. Additionally, the batteries in the present disclosure can be used as power sources for mobile bodies other than vehicles (e.g., railways, ships, aircraft), and can also be used as power sources for electrical products such as information processing devices.

[0092] Furthermore, the present disclosure is not limited to the above-described embodiments. The above-described embodiments are illustrative, and technical solutions having substantially the same constitution as the technical idea described in the patent claims of the present disclosure and achieving the same effects are included in the technical scope of the present disclosure.

[0093] Examples

[0094] [Example 1]

[0095] (Fabrication of the positive electrode)

[0096] 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, mixing was performed using an ultrasonic homogenizer to obtain a positive electrode slurry. The positive electrode slurry was coated on a positive electrode current collector (Al foil) and dried. Thus, a positive electrode having a positive electrode current collector and a positive electrode active material layer was obtained.

[0097] (Fabrication of the negative electrode)

[0098] A Si-based active material (pc-Si: average particle diameter (D 50 ) 0.5 μm) was introduced into a binder solution containing an organic solvent and a binder (PVDF), and mixing was carried out to obtain an active material slurry. A composite particle containing a Si-based active material and a binder was fabricated by a spray drying method using the active material slurry.

[0099] The 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 mixing was performed using an ultrasonic homogenizer. Thus, a negative electrode slurry was fabricated. The negative electrode slurry was coated on a negative electrode current collector (Cu foil) such that the thickness d of the electrode layer became the value shown in Table 1, and dried. Thus, a negative electrode having a negative electrode current collector and a negative electrode active material layer was obtained.

[0100] (Fabrication of the evaluation battery)

[0101] An adhesive (PVDF) and a sulfide solid electrolyte (Li2S-P2S5-based sulfide solid electrolyte) were added to an organic solvent and kneaded using an ultrasonic homogenizer. Thus, a composite slurry was obtained. The composite slurry was coated on a substrate (Al foil) and dried. Thus, a transfer member having a substrate and a solid electrolyte layer was obtained.

[0102] The fabricated positive electrode, negative electrode, and transfer member were each formed into a long strip shape. Next, the positive electrode and the transfer member were overlapped with the positive electrode active material layer and the solid electrolyte layer facing each other, and roll-pressed at 165 °C under a pressure of 50 kN / cm. Then, the substrate was peeled off to obtain a positive electrode side member. In addition, the negative electrode and the transfer member were overlapped with the negative electrode active material layer and the solid electrolyte layer facing each other, and roll-pressed at 25 °C under a pressure of 50 kN / cm. Then, the substrate was peeled off to obtain a negative electrode side member. Next, the above-mentioned negative electrode side member was punched into The positive electrode side member was punched into Powdered sulfide solid electrolyte was disposed on the solid electrolyte layer of the punched negative electrode side member, and uniaxial pressing was performed. Next, the negative electrode side member and the positive electrode side member were overlapped with the solid electrolyte layers facing each other, and current extraction electrodes were attached to the positive electrode and the negative electrode. Then, it was sealed in an aluminum laminate using a vacuum laminator and constrained under a pressure of 5 MPa. Thus, an evaluation battery (all-solid battery) was fabricated.

[0103] For the fabricated evaluation battery, SEM observation was performed, and a cross-sectional SEM image of the negative electrode active material layer was obtained. Using the above method, the average particle diameter R of the composite particles and the thickness d of the electrode layer were obtained from the cross-sectional SEM image of the negative electrode active material layer, and R / d was calculated. The results are shown in Table 1.

[0104] [Examples 2 to 13 and Comparative Examples 1 to 5]

[0105] The solid content fraction of the slurry was changed, and the spray pressure in the spray drying method was changed to fabricate composite particles. Using these composite particles, and changing the coating amount of the negative electrode slurry, an evaluation battery including a negative electrode having R / d shown in Table 1 was fabricated.

[0106] [Evaluation]

[0107] For each of the fabricated evaluation batteries, charging was performed, and the increase in the constraint pressure measured using a force sensor was evaluated as the amount of expansion of the electrode layer. The results are shown in Table 1 and Figure 4 . It should be noted that the increase in the constraint pressure (amount of expansion of the electrode layer) of Comparative Example 1 was set to 100% and evaluated relatively.

[0108]

Table 1

[0109]

[0110] As shown in Table 1 and Figure 4 as shown, compared with all the comparative examples, the swelling amount of the electrode layer was suppressed in all the examples. In particular, in the range where R / d is 0.03 or more and 0.20 or less, the swelling amount of the electrode layer was significantly suppressed.

Claims

1. An electrode layer, which is 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, when the average particle diameter of the composite particles in the thickness direction of the electrode layer is set as R and the thickness of the electrode layer is set as d, the ratio R / d of R to d is 0.20 or less.

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

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

4. The electrode layer according to claim 1, wherein The 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 inclusion type crystal phase.

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

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

9. A battery, which has 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, and the negative electrode active material layer is the electrode layer according to any one of claims 1 to 8.

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

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