Composite particles, electrode mixture material, electrode layer, battery, and method for manufacturing electrode layer

Abstract

To provide composite particles which can suppress battery resistance.SOLUTION: In the present disclosure, composite particles include a binder and a plurality of active materials containing an Si-element or an Sn-element. The composite particles include a first part containing the active materials and a second part not containing the active materials in the cross-sectional view of the composite particles. The composite particles include the second part in the concentration of not larger than 55%.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present disclosure relates to composite particles, an electrode binder, an electrode layer, a battery, and a method for manufacturing an electrode layer.

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 Si element or Sn element and a binder, and having a porosity of 15% or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

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 / contraction amount) of the electrode layer using Si or Sn may become large. If the volume change amount of the electrode is large, there is a risk that the ion conduction path is cut off and the battery resistance increases. In this regard, as in Patent Document 1, it has been studied to provide voids in the negative electrode layer to absorb the expansion of the composite particles, and to suppress the cutting of the ion conduction path and suppress the battery resistance. On the other hand, there is still room for further improvement in suppressing the battery resistance.

[0006] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide composite particles capable of suppressing battery resistance.

Means for Solving the Problems

[0007] [1] A composite particle containing a plurality of active materials containing Si element or Sn element and a binder, When the above composite particle is viewed in cross section, The above composite particle has a first part containing the above active material and a second part not containing the above active material, and the ratio of the second part in the above composite particle is 55% or less.

[0008] [2] The composite particle according to [1], wherein the ratio is 30% or more.

[0009] [3] The composite particle according to [1] or [2], wherein the above active material contains the above Si element and has voids inside.

[0010] [4] The composite particle according to any one of [1] to [3], wherein the above active material contains the above Si element and has a silicon clathrate type crystal phase.

[0011] [5] An electrode binder containing the composite particle according to any one of [1] to [4].

[0012] [6] An electrode layer containing a composite particle, The above composite particle contains a plurality of active materials containing Si element or Sn element and a binder, When the cross-sectional shape of the above composite particle in the above electrode layer is approximated to an ellipse, The aspect ratio of the above composite particle is 3.6 or less.

[0013] [7] The electrode layer according to [6], wherein the aspect ratio is 3.0 or less.

[0014] [8] The electrode layer according to [6] or [7], wherein the aspect ratio is 1.6 or more.

[0015] [9] The electrode layer according to any one of [6] to [8], wherein the electrode layer contains a conductive assistant and a solid electrolyte.

[0016]

[10] 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 [6] to [9].

[0017]

[11] The battery according to

[10] , wherein the electrolyte layer is a solid electrolyte layer.

[0018]

[12] A preparation step of preparing an electrode mixture containing the composite particles according to any one of [1] to [4], A precursor layer forming step of forming a precursor layer using the electrode mixture, A method for manufacturing an electrode layer, comprising: an electrode layer forming step of applying a pressing pressure to the precursor layer to form an electrode layer, In the electrode layer forming step, When the cross-sectional shape of the composite particles in the electrode layer is approximated to an ellipse, A method for manufacturing an electrode layer, wherein the pressing pressure is applied so that the aspect ratio of the composite particles is 3.6 or less.

[0019]

[13] In the electrode layer forming step, the pressing pressure is applied by roll pressing, The method for manufacturing an electrode layer according to

[12] , wherein the pressing pressure is 30 kN / cm or more and 100 kN / cm or less.

Advantages of the Invention

[0020] When used in a battery, the composite particles in the present disclosure have the effect of suppressing battery resistance.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0022] Hereinafter, the composite particles, electrode binder, electrode layer, battery, and method for manufacturing the electrode layer in the present disclosure will be described in detail.

[0023] A. Composite Particles The composite particles in the present disclosure contain a plurality of active materials containing Si element or Sn element and a binder. Further, when the composite particles are viewed in cross-section, the composite particles have a first part containing the active material and a second part not containing the active material, and the ratio of the second part in the composite particles is 55% or less. Here, in this specification, an active material containing Si element may be referred to as a Si-based active material, and an active material containing Sn element may be referred to as a Sn-based active material.

[0024] The composite particles in the present disclosure contain a predetermined active material and a binder, and have a predetermined second part in a cross-sectional view. Therefore, the second part can absorb expansion and suppress the volume change of the composite particles. As a result, when the composite particles are used in a battery, the battery resistance can be suppressed.

[0025] In addition, in the composite particles in the present disclosure, since the ratio of the second part is 55% or less, a predetermined aspect ratio can be achieved in the electrode layer. Although details will be described later, it is presumed that when the composite particles have a predetermined aspect ratio in the electrode layer, the degree of bending of the ion conduction path in the electrode layer can be reduced. As a result, unevenness in the reaction in the thickness direction of the electrode layer can be suppressed, the amount of volume change of the electrode layer can be suppressed, and the battery resistance can be suppressed.

[0026] The composite particles in the present disclosure, when viewed in cross-section, have a first part containing a Si-based active material or a Sn-based active material, and a second part not containing the above active material. The second part generally refers to a site including a void or a binder formed between adjacent active materials. When the Si-based active material has voids inside as described later, the void part inside the Si-based active material is included in the above first part.

[0027] The ratio of the second part may be 50% or less, may be 45% or less, or may be 40% or less. On the other hand, the ratio of the second part is, for example, 30% or more, and may be 35% or more.

[0028] Here, the ratio of the second part can be calculated, for example, by the following method. First, as shown in Fig. 1(a), a cross-sectional image of the composite particles is obtained by a scanning electron microscope (SEM). A more specific method for obtaining the cross-sectional image will be described in the examples. Next, as shown in Fig. 1(b), image analysis is performed on the cross-sectional image, and it is binarized into a first part (the dark part in Fig. 1(b)) containing the Si-based active material or the Sn-based active material and a second part (the light part in Fig. 1(b)) not containing the active material. Then, in the binarized image, the ratio of the area of the second part to the total area of the first part and the second part is calculated by image analysis software. The ratio of the second part in the present disclosure is preferably the average value obtained by measuring 10 or more samples (composite particles). The number of samples may be 20 or more, 50 or more, or 100 or more.

[0029] The composite particles in the present disclosure contain a plurality of active materials containing Si element or Sn element and a binder. Here, the composite particles can be regarded as aggregates in which a plurality of the above active materials (Si-based active materials or Sn-based active materials) are aggregated. The active material may be primary particles or secondary particles in which primary particles are aggregated.

[0030] The active material containing Si element (Si-based active material) may be Si alone, an alloy (Si alloy) containing Si as a main component, or a Si oxide. The ratio of Si element in the Si alloy is, for example, 50 mol% or more and 95 mol% or less.

[0031] In addition, the Si-based active material may have voids inside. The Si-based active material having voids is referred to as porous Si. The presence of voids can be confirmed by SEM (scanning electron microscope) observation. Also, the porosity is not particularly limited, but for example, it may be 4% or more, and may be 10% or more. Further, the above porosity may be, 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 material is obtained 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 area) / ((silicon area)+(void area))

[0032] 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. Also, the BET specific surface area of porous Si is, for example, 20 m 2 / g or more and 200 m 2 / g or less.

[0033] 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.

[0034] 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-type structure (cage) for the skeletal atoms, and metal ions such as Li ions can enter therein. Therefore, 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).

[0035] 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 ratio 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 ratio 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 ratio of the crystal phase can be determined by using the RIR method (Reference Intensity Ratio method).

[0036] As a method for manufacturing porous class rate Si, for example, the 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 class rate type crystal phase. A method can be mentioned.

[0037] The active material containing Sn element (Sn-based active material) may be simple Sn, an alloy (Sn alloy) containing Sn as a main component, or a Sn oxide. The proportion of Sn element in the Sn alloy is, for example, 50 mol% or more and 95 mol% or less.

[0038] The proportion of the 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.

[0039] 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.

[0040] The proportion of the binder in the composite particles is, for example, 0.5% by weight or more and 10% by weight or less.

[0041] The average particle diameter (D 50 ) of the composite particles is, for example, 1 μm or more and 100 μm or less. The average particle diameter (D 50 ) refers to the volume cumulative particle diameter obtained by measurement by the laser diffraction scattering particle size distribution measurement method. Also, the average particle diameter (D 50) is, for example, 0.1 μm or more and 3 μm or less. The number of the above-mentioned active substances contained in the composite active substance is, for example, 10 or more and 150 or less. The use of the composite particles is not particularly limited, but it is preferably used in a battery.

[0042] B. Electrode composite material The electrode composite material in the present disclosure contains the above-mentioned composite particles. Further, the electrode composite material may further contain at least one of a conductive assistant, a binder, and an electrolyte, if necessary.

[0043] According to the present disclosure, since it contains the above-mentioned composite particles, when used in a battery, the battery resistance can be suppressed.

[0044] The ratio of the composite particles in the electrode composite material is not particularly limited, but is, for example, 50% by weight or more, may be 70% by weight or more, and may be 90% by weight or more. On the other hand, the ratio of the composite particles is, for example, 99% by weight or less, and may be 95% by weight or less.

[0045] Examples of the conductive assistant include carbon materials. Examples of the carbon material include 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 ratio of the conductive assistant in the electrode composite material 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.

[0046] Examples of the binder include the binders described in "A. Composite particles". The binder in the composite particles and the binder in the electrode composite material may be of the same type or different types. The ratio of the binder in the electrode composite material 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.

[0047] The electrode composite 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.

[0048] 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. Further, the sulfide solid electrolyte may contain a halogen element such as F, Cl, Br, and I. Also, in the sulfide solid electrolyte, a part of the S element may be substituted with an O element.

[0049] The sulfide solid electrolyte may be a glass-based (amorphous) sulfide solid electrolyte, a glass-ceramics-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.

[0050] 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 any one of Ge, Zn, and Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li xMO y (However, x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.) can be mentioned.

[0051] The proportion of the solid electrolyte in the electrode composite material 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.

[0052] In addition, the electrode composite material in the present disclosure may contain a dispersion medium such as an organic solvent. That is, the electrode composite material may be a slurry. On the other hand, the electrode composite material may be a powder. Examples of the organic solvent include organic solvents conventionally known in the field of batteries such as butyl butyrate.

[0053] C. Electrode layer The electrode layer in the present disclosure is 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 cross-sectional shape of the composite particles in the electrode layer is approximated to an ellipse, the aspect ratio of the composite particles is 3.6 or less. Here, the "cross-sectional shape of the composite particles in the electrode layer" means the cross-sectional shape of the composite particles that can be observed when the electrode layer is viewed in cross-section in the thickness direction.

[0054] The aspect ratio in the present disclosure is 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 is approximated to an ellipse. Here, it is assumed that the electrode layer is manufactured by applying a pressing pressure as described later. 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. 3 described later). 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. 3 described later).

[0055] According to the present disclosure, since the composite particles have a predetermined aspect ratio of 3.6 or less, an electrode layer capable of suppressing battery resistance is obtained.

[0056] Here, generally, carrier ions move within the electrode layer through an electrolyte portion having good ion conductivity. That is, the ion conduction path of the carrier ions bends so as to bypass the composite particles. Therefore, when the aspect ratio is greater than 3.6, the distance for bypassing the composite particles becomes longer, the ion conduction path in the thickness direction becomes longer, and the ion conduction resistance increases. As a result, the battery resistance increases. On the other hand, in the electrode layer according to the present disclosure, since the aspect ratio is 3.6 or less, the bending of the ion conduction path in the thickness direction can be reduced, and thus an increase in battery resistance due to an increase in ion conduction resistance can be suppressed.

[0057] The aspect ratio may be 3.5 or less, 3.3 or less, 3.0 or less, or 2.8 or less. On the other hand, the aspect ratio is, for example, 1.5 or more, and may be 1.6 or more, 1.8 or more, 2.0 or more, 2.3 or more, or 2.5 or more.

[0058] The minor axis a and the major axis b of the composite particles are not particularly limited as long as the above aspect ratio is satisfied. The minor axis a is, for example, 0.1 μm or more and 30 μm or less. The major axis b is, for example, 1.0 μm or more and 100 μm or less.

[0059] Here, the minor diameter, major diameter, and aspect ratio can be calculated, for example, by the following method. First, as shown in Fig. 3(a), a cross-sectional image of the electrode layer is obtained by a scanning electron microscope (SEM). Next, as shown in Fig. 3(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. 3(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. 3(d), for each composite particle approximated by an ellipse, the minor diameter, major diameter, and area are measured, and 10 composite particles are selected in descending order of cross-sectional area. The aspect ratio (major diameter / minor diameter) is measured from the minor diameter and major diameter of each selected composite particle, and the average value of the measured aspect ratios is obtained as the aspect ratio in the present disclosure.

[0060] The number of composite particles to be selected may be more than 10. The number of composite particles to be selected may be 30 or more, may be 50 or more, or may be 100 or more. Also, as the observation field of the SEM image, it is preferable to use a field containing more composite particles than the above-mentioned number. The observation field is, 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.

[0061] Regarding the composite particles, it is the same as the content described in "A. Composite Particles". Here, it is assumed that the electrode layer is manufactured by applying a pressing pressure as described later. Therefore, in the electrode layer, it is assumed that the ratio of the second part of the composite particles becomes smaller compared to before the pressing pressure is applied. Also, similarly, when the composite particles contain porous Si, the void volume of the voids with a pore diameter of 50 nm or less is assumed to become smaller compared to before the pressing pressure is applied.

[0062] The electrode layer may be a positive electrode active material layer containing the composite particles as a positive electrode active material, or may be a negative electrode active material layer containing the 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. The conductive assistant, the binder, and the electrolyte are the same as those described in "B. Electrode composite material".

[0063] The thickness of the electrode layer is not particularly limited, but for example, it is 0.1 μm or more and 1000 μm or less.

[0064] D. Battery FIG. 4 is a schematic cross-sectional view illustrating a battery in the present disclosure. The battery 10 shown in FIG. 4 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. Further, the negative electrode active material layer 2 in the battery 10 is the electrode layer in the present disclosure described above.

[0065] 1. Positive electrode active material layer The positive electrode active material layer contains at least a positive electrode active material, and may contain at least one of a conductive assistant, a binder, and an electrolyte, if necessary. The conductive assistant, the binder, and the electrolyte are the same as those described in "C. Electrode composite material".

[0066] 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 composite particles. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active material include rock salt layer-type 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 and the like, spinel-type active materials such as LiMn2O4, Li4Ti5O 12 and the like, and olivine-type active materials such as LiFePO4. Examples of the shape of the positive electrode active material include particulate shape. 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.

[0067] 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.

[0068] 2. Negative electrode active material layer The negative electrode active material layer is the electrode layer described above. Regarding the electrode layer, it is the same as the content described in "C. Electrode layer".

[0069] 3. Electrolyte layer The electrolyte layer contains an electrolyte. The electrolyte is preferably a solid electrolyte. Regarding the solid electrolyte, it is the same as the content described in "B. Electrode binder". Further, the electrolyte layer may contain a binder as necessary. Regarding the binder, it is the same as the content described in "B. Electrode binder". 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.

[0070] The thickness of the electrolyte layer is not particularly limited, but is, for example, 0.1 μm or more and 1000 μm or less.

[0071] 4. Other configurations As shown in FIG. 4, the battery 10 in the present disclosure usually 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. 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.

[0072] 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 laminated 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. As the restraining jig, a known jig can be used. 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.

[0073] 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 an electrolyte layer. Examples of the use of the battery include a power source for vehicles such as hybrid vehicles (HEVs), plug-in hybrid vehicles (PHEVs), battery electric vehicles (BEVs), 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.

[0074] E. Method for manufacturing electrode layer FIG. 5 is a flowchart illustrating a method for manufacturing an electrode layer in the present disclosure. As shown in FIG. 5, in the method for manufacturing an electrode layer in the present disclosure, first, an electrode mixture containing the above-described composite particles is prepared (preparation step). Next, a precursor layer is formed using the electrode mixture (precursor layer formation step). Then, a pressing pressure is applied to the precursor layer to form an electrode layer (electrode layer formation step). Further, in the electrode layer formation step, when the cross-sectional shape of the composite particles in the electrode layer is approximated to an ellipse, the pressing pressure is applied so that the aspect ratio of the composite particles is 3.6 or less.

[0075] According to the present disclosure, a precursor layer is formed using an electrode mixture containing the above-described composite particles, and a pressing pressure is applied to the precursor layer, thereby forming an electrode layer containing composite particles having a predetermined aspect ratio. As a result, when used in a battery, an electrode layer capable of suppressing battery resistance can be manufactured.

[0076] 1. Preparation Step The preparation step is a step of preparing an electrode composite material containing the composite particles described above. The composite particles are the same as those described in "A. Composite Particles". Also, the electrode composite material is the same as that described in "B. Electrode Composite Material".

[0077] 2. Precursor Layer Formation Step The precursor layer formation step is a step of forming a precursor layer using the above electrode composite material.

[0078] In the precursor layer formation step, the method is not particularly limited as long as a layered precursor layer can be formed from the electrode composite material. Examples of the method for forming the precursor layer include a coating method using an electrode composite material in the form of a slurry. The coating method can include, for example, a method of applying the electrode composite material to a substrate such as a metal plate and drying it. The thickness of the precursor layer is not particularly limited as long as an electrode layer with a desired thickness can be obtained and can be adjusted as appropriate.

[0079] 3. Electrode Layer Formation Step The electrode layer formation step is a step of applying a pressing pressure to the above precursor layer to form an electrode layer. Also, in the electrode layer formation step, when the cross-sectional shape of the composite particles in the above electrode layer is approximated to an ellipse, the pressing pressure is applied so that the aspect ratio of the composite particles is 3.6 or less.

[0080] The method of applying the pressing pressure (pressing method) is not particularly limited, and examples thereof include a roll press and a flat press. The pressing pressure (linear pressure) in the roll press and the pressing pressure (surface pressure) in the flat press are not particularly limited as long as the above aspect ratio is obtained. The linear pressure in the roll press is, for example, 30 kN / cm or more, may be 40 kN / cm or more, and may be 50 kN / cm or more. On the other hand, the linear pressure is, for example, 100 kN / cm or less, may be 80 kN / cm or less, and may be 60 kN / cm or less. Further, the surface pressure in the flat press is, for example, 800 MPa or more and 3000 MPa or less. Further, the pressing may be performed while heating the precursor layer. The heating temperature is, for example, 80°C or more and 200°C or less.

[0081] 4. Electrode layer The electrode layer obtained through the above-described respective steps is not particularly limited, but is preferably the electrode layer described in "C. Electrode layer".

[0082] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration 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

[0083] [Examples] (Fabrication of positive electrode) A binder (PVDF), a conductive assistant, 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 an electrode mixture slurry. The obtained electrode mixture slurry was coated on 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.

[0084] (Fabrication of negative electrode) To a binder solution containing an organic solvent and a binder (PVDF), Si-based active material (pc-Si: average particle diameter (D 50 ) 0.5 μm) was added and mixed to prepare a slurry. By a spray drying method using this slurry, composite particles containing the Si-based active material and the binder were produced.

[0085] Regarding the produced composite particles, the ratio of the second part was measured as follows. The results are shown in Table 1. First, the composite particles and an epoxy resin were mixed and cured to obtain a solidified product. Next, cross-section machining by an ion milling method was performed on the above solidified product. A cross-sectional image of the composite particles was obtained by observing the machined cross-section with SEM. The obtained cross-sectional image was binarized into a part containing the Si-based active material (the first part) and a part not containing the Si-based active material (the second part), and the ratio of the second part in each composite particle was calculated. Then, the average value of the ratios of the second part of 10 composite particles was obtained. The cross-section of the observed composite particles was observed as a sea-island structure in which the second part was the sea and the first part was the island, as shown in Fig. 1.

[0086] To an organic solvent, composite particles, a binder (PVDF), a conductive assistant (VGCF), and a sulfide solid electrolyte (Li₂S-P₂S₅-based sulfide solid electrolyte) were added and kneaded using an ultrasonic homogenizer. Thereby, a negative electrode slurry was produced. The negative electrode slurry was applied to a negative electrode current collector (Cu foil) and dried. Thereby, a negative electrode having a negative electrode current collector and a negative electrode active material layer was obtained.

[0087] (Fabrication of Evaluation Battery) To an organic solvent, a binder (PVDF) and a sulfide solid electrolyte (Li₂S-P₂S₅-based sulfide solid electrolyte) were added 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.

[0088] 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 a pressure of 50 kN / cm at 165°C. 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 a pressure of 50 kN / cm at 25°C. 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 encapsulated in an aluminum laminate using a vacuum laminator and constrained at a pressure of 5 MPa. Thereby, an evaluation battery (all-solid-state battery) was fabricated.

[0089] [Examples 2 to 7 and Comparative Examples 1 to 5] In the production of the composite particles, by changing the solid content ratio of the slurry, composite particles having the ratio of the second part as shown in Table 1 were produced. An evaluation battery was produced in the same manner as in Example 1 except that a negative electrode was produced using these composite particles.

[0090] [Evaluation] (Measurement of aspect ratio) 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 aspect ratio of the composite particles in the negative electrode active material layer was calculated. The results are shown in Table 1.

[0091] (Measurement of battery resistance) Each of the fabricated evaluation batteries was adjusted to a voltage of 3.7 V. Then, it was discharged at 5C, and the resistance value was calculated based on the voltage drop amount 5 s after the discharge. Using the resistance value of Comparative Example 1 as 100%, it was evaluated relatively. The results are shown in Table 1. Also, the relationship between the battery resistance and the ratio of the second part is shown in Fig. 6(a), and the relationship between the battery resistance and the aspect ratio is shown in Fig. 6(b).

[0092]

Table 1

[0093] As shown in Table 1 and FIG. 6, in the electrode layer produced using composite particles having a ratio of the second part of 55% or less, it was confirmed that the aspect ratio of the composite particles was 3.6 or less. Further, in the battery using this electrode layer, it was confirmed that the battery resistance was significantly suppressed.

Description of reference numerals

[0094] 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. A composite particle containing a plurality of active materials containing Si element or Sn element and a binder, when the cross-section of the composite particle is viewed, the composite particle has a first part containing the active material and a second part not containing the active material, and the proportion of the second part in the composite particle is 55% or less.

2. The composite particle according to claim 1, wherein the proportion is 30% or more.

3. The composite particle according to claim 1, wherein the active material contains the Si element and has voids inside.

4. The composite particle according to claim 1, wherein the active material contains the Si element and has a silicon clathrate-type crystal phase.

5. An electrode binder containing the composite particle according to any one of claims 1 to 4.

6. An electrode layer containing a composite particle, the composite particle contains a plurality of active materials containing Si element or Sn element and a binder, when the cross-sectional shape of the composite particle in the electrode layer is approximated to an ellipse, the aspect ratio of the composite particle is 3.6 or less.

7. The electrode layer according to claim 6, wherein the aspect ratio is 3.0 or less.

8. The electrode layer according to claim 6, wherein the aspect ratio is 1.6 or more.

9. The electrode layer according to claim 6, wherein the electrode layer contains a conductive auxiliary agent and a solid electrolyte.

10. 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 6 to 9.

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

12. A preparation step of preparing an electrode binder containing the composite particle according to any one of claims 1 to 4, a precursor layer forming step of forming a precursor layer using the electrode binder, an electrode layer forming step of applying a pressing pressure to the precursor layer to form an electrode layer, which is a method for manufacturing an electrode layer, in the electrode layer forming step, when the cross-sectional shape of the composite particle in the electrode layer is approximated to an ellipse, the pressing pressure is applied so that the aspect ratio of the composite particle is 3.6 or less.

13. In the electrode layer forming step, the pressing pressure is applied by roll pressing, The method for manufacturing an electrode layer according to claim 12, wherein the press pressure is 30 kN / cm or more and 100 kN / cm or less.

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