Electrode composite material and battery

Abstract

This disclosure provides an electrode composite material that can suppress excessive crushing of the electrode active material in the thickness direction due to pressing when an electrode active material layer is formed, and / or improve the uniformity of each component in the thickness direction and the planar direction, and a battery containing such an electrode composite material. [Solution] The electrode mixture of the present disclosure comprises electrode active material particles and tetrapod-shaped particles. The battery of the present disclosure has an electrode active material layer, and the electrode active material layer contains the electrode mixture of the present disclosure.

Description

Technical Field

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

Background Art

[0002] Conventionally, various electrode materials for batteries have been developed. In particular, in an electrode active material layer containing alloy-based active material particles that expand and contract during charge and discharge of a battery, a technique for suppressing volume changes in the electrode active material layer due to the above expansion and contraction has been developed.

[0003] For example, Patent Document 1 discloses a negative electrode for a secondary battery having an active material layer, the active material layer including a sulfide solid electrolyte and composite particles as an active material, the composite particles including a plurality of porous silicon particles and a binder, and the active material layer having a porosity of more than 15%.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, an electrode active material layer for a solid battery is usually pressed for densification. It may be desirable that the electrode active material is not excessively crushed even by such pressing. In particular, in a porous electrode active material as disclosed in, for example, Patent Document 1, it is desirable that the porous electrode active material is not excessively crushed in order to maintain the porous structure.

[0006] Also, from the viewpoint of facilitating the occurrence of an electrode reaction uniformly within the electrode active material layer, it is desirable that the uniformity of each constituent component of the electrode active material layer is high in the thickness direction and the plane direction.

[0007] The present disclosure aims to provide an electrode composite material that can suppress excessive crushing of the electrode active material in the thickness direction due to pressing when an electrode active material layer is formed, and / or improve the uniformity of each component in the thickness direction and the planar direction, and a battery containing such an electrode composite material. [Means for solving the problem]

[0008] The Disclosing Party has found that the above-mentioned problems can be solved by the following means. <Aspect 1> Electrode active material particles, and Tetrapod-shaped particles An electrode composite material containing this material. <Aspect 2> The electrode composite material according to embodiment 1, wherein the ratio of the length of one side of the tetrapod-shaped particles to the average particle diameter of the electrode active material particles is 1 or more and 50 or less. <Aspect 3> The electrode composite material according to embodiment 1, wherein the electrode active material particles form electrode active material composite particles. <Aspect 4> The electrode composite material according to embodiment 3, wherein the ratio of the length of one side of the tetrapod-shaped particle to the average particle diameter of the electrode active material composite particle is 0.1 or more and 10 or less. <Aspect 5> An electrode mixture according to any one of embodiments 1 to 4, further comprising fibrous particles. <Aspect 6> The electrode composite material according to embodiment 5, wherein the fibrous particles are vapor-grown carbon fibers. <Aspect 7> The electrode mixture according to embodiment 5 or 6, wherein the ratio of the length of one side of the tetrapod-shaped particles to the fiber length of the fibrous particles is 0.5 or more and 20 or less. <Aspect 8> The electrode composite material according to any one of embodiments 1 to 7, wherein the electrode active material particles are alloy-based electrode active material particles. <Pattern 9> The electrode composite material according to embodiment 8, wherein the alloy electrode active material particles are silicon particles. <Aspect 10> The electrode composite material according to any one of Aspects 1 to 9, wherein the tetrapod-shaped particles are zinc oxide particles. <Aspect 11> The electrode composite material according to any one of Aspects 1 to 10, wherein the ratio of the content of the tetrapod-shaped particles to the content of the electrode active material particles is 1.0% by volume or more and 6.0% by volume or less. <Aspect 12> The electrode composite material according to any one of Aspects 1 to 11, further comprising a solid electrolyte. <Aspect 13> The electrode composite material according to Aspect 12, wherein the solid electrolyte is a sulfide solid electrolyte. <Aspect 14> Having an electrode active material layer and The battery, wherein the electrode active material layer contains the electrode composite material according to any one of Aspects 1 to 13. <Aspect 15> The battery according to Aspect 14, which is a solid-state battery.

Advantages of the Invention

[0009] According to the present disclosure, when forming the electrode active material layer, it is possible to suppress excessive crushing of the electrode active material in the thickness direction due to pressing, and / or improve the uniformity of each constituent component in the thickness direction and the plane direction. An electrode composite material can be provided, and a battery containing such an electrode composite material can be provided.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the electrode composite material of the present disclosure as an electrode active material layer. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the electrode composite material of the present disclosure as an electrode active material layer.

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments and can be variously modified and implemented within the scope of the gist of the disclosure.

[0012] <<Electrode composite material>> The electrode mixture of this disclosure includes electrode active material particles and tetrapod-shaped particles.

[0013] The Disclosing Parties have unexpectedly discovered that, by including electrode active material particles and tetrapod-shaped particles in the electrode composite, it is possible to suppress excessive crushing of the electrode active material in the thickness direction due to pressing when an electrode active material layer is formed. The reason for this is thought to be that, although not intended to be bound by any theory, the tetrapod-shaped particles 20 function as pillars, as illustrated in Figure 1, thereby suppressing excessive crushing of the electrode active material.

[0014] Furthermore, the Disclosing Parties unexpectedly discovered that the electrode mixture, by including electrode active material particles and tetrapod-shaped particles, can improve the uniformity of each component in the thickness and planar directions when an electrode active material layer is formed. The reason for this is thought to be that, although not intended to be bound by any theory, the tetrapod-shaped particles 20 can suppress the planar orientation of each component of the electrode mixture, as illustrated in Figure 2.

[0015] Figures 1 and 2 are schematic cross-sectional views showing an example of the electrode composite material 1 of this disclosure as an electrode active material layer. In Figures 1 and 2, "10" represents electrode active material particles or electrode active material composite particles described later, "20" represents tetrapod-shaped particles, and "30" represents fibrous particles.

[0016] In this disclosure, “compound mixture” means a composition that can constitute an active material layer, either in itself or by further containing other components. In this disclosure, “compound mixture slurry” means a slurry that includes a dispersion medium in addition to the “compound mixture,” and thereby can be applied and dried to form an active material layer.

[0017] With respect to this disclosure, the "electrode mixture" may be either a "positive electrode mixture" or a "negative electrode mixture," and may be particularly a "negative electrode mixture."

[0018] The following describes each element that constitutes the electrode composite material of this disclosure.

[0019] <Electrode active material particles> The electrode mixture of this disclosure includes electrode active material particles. The "electrode active material" may be a "positive electrode active material" or a "negative electrode active material," and may be particularly a "negative electrode active material." For example, if the electrode active material particles are negative electrode active material particles, the electrode mixture of this disclosure is a negative electrode mixture.

[0020] In the electrode composite material of this disclosure, the electrode active material particles may be alloy-based electrode active material particles. The alloy-based active material particles are not particularly limited and may, for example, expand and contract during the charging and discharging of the battery.

[0021] Specifically, alloy-based electrode active materials may include, but are not limited to, silicon (Si) alloy-based electrode active materials or tin (Sn) alloy-based electrode active materials.

[0022] Examples of Si alloy electrode active materials include silicon, silicon oxide, silicon carbide, silicon nitride, or solid solutions thereof. Furthermore, Si alloy electrode active materials may also contain elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, Ti, etc.

[0023] Examples of Sn alloy electrode active materials include tin, tin oxides, tin nitrides, or solid solutions thereof. Furthermore, Sn alloy electrode active materials may also contain elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, Si, etc.

[0024] The alloy-based electrode active material may contain silicon. That is, the electrode active material particles may contain silicon particles, and in particular may be silicon particles.

[0025] The silicon particles may be amorphous or crystalline. The crystalline phase contained in the silicon particles is not particularly limited.

[0026] The silicon particles may be porous silicon particles. With this configuration, the expansion of silicon as an alloy electrode active material can be absorbed by the pores within the porous silicon particles. Furthermore, the tetrapod-shaped particles, described later, can also function as pillars for the pores within the porous silicon particles. Therefore, volume changes in the electrode active material layer can be suppressed more effectively.

[0027] In this disclosure, porous silicon particles may include nanoporous silicon. Nanoporous silicon refers to silicon having multiple pores with a pore diameter on the nanometer order, i.e., less than 1000 nm, particularly less than 100 nm. Porous silicon particles may also contain pores with a diameter of 55 nm or less. Pores with a diameter of 55 nm or less are difficult to crush by pressing. That is, porous silicon particles containing pores with a diameter of 55 nm or less tend to maintain their porous structure even after pressing. For example, per gram of porous silicon particles, there may be 0.21 cc or more, 0.22 cc / g or more, or 0.23 cc / g or more of pores with a diameter of 55 nm or less, and also 0.30 cc / g or less, 0.28 cc / g or less, or 0.26 cc / g or less. The amount of pores with a diameter of 55 nm or less contained in porous silicon particles can be determined, for example, from the pore size distribution by nitrogen gas adsorption method or DFT method.

[0028] The proportion of pores in porous silicon particles is not particularly limited. This proportion may be, for example, 1% or more, 5% or more, 10% or more, or 20% or more, and may also be 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less. This pore proportion can be determined, for example, by observation using a scanning electron microscope (SEM). A large number of samples is preferable, for example, 100 or more. This proportion can be the average value obtained from these samples.

[0029] The average particle size of the electrode active material particles may be, for example, 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.5 μm or more, or 1 μm or more, and may also be 10 μm or less, 5 μm or less, 3 μm or less, 2 μm or less, or 1.5 μm or less. The average particle size can be determined by observation with an electron microscope such as a scanning electron microscope (SEM), and can be determined, for example, as the average value of the maximum Ferret diameter of each of multiple particles. The number of samples is preferably large, for example, 20 or more, 50 or more, or 100 or more. The average particle size can be adjusted as appropriate, for example, by appropriately changing the manufacturing conditions of the electrode active material particles or by performing a classification process.

[0030] The electrode active material particles may or may not contain electrode active materials other than alloy-based electrode active materials. The content of alloy-based electrode active materials in the electrode active material particles is not particularly limited and may be, for example, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, 99% or more by mass, or 100% by mass. In other words, the electrode active material particles may contain only alloy-based electrode active materials as electrode active materials.

[0031] (electrode active material composite particles) In the electrode composite material of this disclosure, the electrode active material particles may form electrode active material composite particles.

[0032] The average particle size of the electrode active material composite particles may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, or 10 μm or more, and may also be 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The average particle size can be determined by observation with an electron microscope such as a scanning electron microscope (SEM), and can be determined, for example, as the average value of the maximum Ferret diameter of each of the multiple particles. The number of samples is preferably large, for example, 20 or more, 50 or more, or 100 or more. The average particle size can be adjusted as appropriate, for example, by appropriately changing the manufacturing conditions of the electrode active material composite particles or by performing a classification process.

[0033] The electrode active material composite particles have voids. These voids can absorb the expansion that occurs when the alloy-based electrode active material particles are silicon particles. The tetrapod-shaped particles, described later, can function as pillars for these voids. That is, the tetrapod-shaped particles can suppress the collapse of these voids, for example, by pressing during the densification of the electrode active material layer.

[0034] The porosity of the electrode active material composite particles is not particularly limited and can be set appropriately considering the desired battery capacity, the amount of expansion of the electrode active material particles, etc.

[0035] The electrode active material composite particles may further contain a binder. The electrode active material composite particles may be secondary particles in which multiple electrode active material particles are bonded to each other via a binder, for example.

[0036] The content of electrode active material particles in the electrode active material composite particles is not particularly limited and can be set appropriately considering the desired battery capacity, etc.

[0037] The binder is not particularly limited and may include, for example, rubber binders such as butadiene rubber (BR) binders, butylene rubber (IIR) binders, acrylate butadiene rubber (ABR) binders, and styrene butadiene rubber (SBR) binders; polymer binders such as polyvinylidene fluoride (PVDF) binders, polytetrafluoroethylene (PTFE) binders, polyimide (PI) binders, carboxymethylcellulose (CMC) binders, polyacrylate binders, and polyacrylic acid ester binders; sugar binders such as fructose, glucose, sucrose, and maltose; or combinations thereof.

[0038] The binder content in the electrode active material composite particles is not particularly limited and can be set as appropriate considering the desired binding properties, etc.

[0039] The method for forming electrode active material composite particles is not particularly limited, and for example, they can be formed by providing a slurry containing electrode active material particles and a dispersion medium, and drying and removing the dispersion medium by spray drying.

[0040] The dispersion medium is not particularly limited as long as it can disperse the electrode active material particles.

[0041] The slurry may further contain a binder. In this case, the dispersion medium may be capable of dissolving the binder; that is, the dispersion medium may be a solvent for the binder.

[0042] <Tetrapod-shaped particles> The electrode mixture of this disclosure contains tetrapod-shaped particles. By including tetrapod-shaped particles in the electrode mixture, excessive crushing of the electrode active material in the thickness direction due to pressing can be suppressed when an electrode active material layer is formed.

[0043] In the electrode mixture of this disclosure, the tetrapod-shaped particles may be zinc oxide particles. The tetrapod-shaped zinc oxide particles may be, for example, commercially available products.

[0044] The tetrapod-shaped form of tetrapod-shaped particles in the electrode mixture can be observed, for example, by 3D-SEM, CT scan, etc.

[0045] The length of one side of the tetrapod-shaped particle is not particularly limited and may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more, or 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. In this invention, the "length of one side" of the tetrapod-shaped particle refers to the average length of the four legs that constitute the tetrapod-shaped particle.

[0046] The content of tetrapod-shaped particles is not particularly limited and can be set appropriately within a range that does not interfere with the electrode reaction while allowing them to function as pillars.

[0047] (Relationship with electrode active material particles or composite particles thereof) In the electrode mixture of the present disclosure, the ratio of the length of one side of the tetrapod-shaped particles to the average particle diameter of the electrode active material particles may be 1 or more and 50 or less. This ratio may be 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 6 or more, and may also be 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 7 or less.

[0048] In the electrode composite material of this disclosure, the ratio of the length of one side of the tetrapod-shaped particles to the average particle diameter of the electrode active material composite particles may be 0.1 or more and 10 or less. This ratio may be 0.1 or more, 0.3 or more, 0.5 or more, 1 or more, or 2 or more, and may be 10 or less, 5 or less, 3 or less, or 2 or less.

[0049] In the electrode mixture of this disclosure, the ratio of the content of tetrapod-shaped particles to the content of electrode active material particles may be 1.0 volume% or more and 6.0 volume% or less. This ratio may be 1.0 volume% or more, or 1.5 volume% or more, and may be 6.0 volume% or less, 5.0 volume% or less, 4.0 volume% or less, 3.0 volume% or less, or 2.0 volume% or less.

[0050] <Fibrous particles> The electrode mixture of the present disclosure may further contain fibrous particles. The fibrous particles may function as conductive additives. In the context of this disclosure, "fibrous" means having an aspect ratio of 2.5 or greater.

[0051] The disclosing parties in this case considered that if the electrode mixture does not contain tetrapod-shaped particles but contains fibrous particles, the fibrous particles tend to be oriented in the planar direction, that is, they tend to exist in a bent state. They believed that this would impair the uniformity of each component in the electrode active material layer in both the thickness direction and the planar direction.

[0052] In response to this, the Disclosers believed that the above problem could be solved by further including tetrapod-shaped particles in the electrode mixture containing fibrous particles. The reason for this is presumed to be as follows, although this is not intended to be bound by any theory: That is, as illustrated in Figure 2, by including tetrapod-shaped particles 20 in the electrode mixture 1, the orientation of the fibrous particles 30 in the planar direction is suppressed, and the fibrous particles 30 can also be oriented in the thickness direction, that is, the fibrous particles 30 can exist in an upright state. And this is thought to improve the uniformity of each component in the electrode active material layer in the thickness direction and the planar direction.

[0053] The orientation of fibrous particles in the thickness direction improves conductivity, thereby facilitating uniform electrode reactions. Furthermore, the orientation of fibrous particles in the thickness direction improves the strength of the electrode composite material as an electrode active material layer.

[0054] The fibrous particles are not particularly limited and may be, for example, fibrous carbon, fibrous elemental metal or metal compound, or a combination thereof.

[0055] Examples of fibrous carbon include carbon nanotubes (CNTs), vapor-grown carbon fibers (VGCFs), carbon nanofibers (CNFs), and carbon microfibers (CMFs). Examples of carbon nanotubes include single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs).

[0056] Examples of metals that make up fibrous metals include nickel, aluminum, copper, iron, stainless steel, and titanium.

[0057] The fibrous particles may be, in particular, vapor-grown carbon fibers (VGCF).

[0058] The fiber diameter of the fibrous particles is not particularly limited and may be, for example, 0.1 nm or more, 0.3 nm or more, 0.5 nm or more, 1 nm or more, 5 nm or more, 10 nm or more, 50 nm or more, 80 nm or more, 100 nm, 120 nm or more, 140 nm or more, or 150 nm or more, and may also be 1000 nm or less, 750 nm or less, 500 nm or less, 300 nm or less, 200 nm or less, or 150 nm or less.

[0059] The fiber length of the fibrous particles may be, for example, 0.1 μm or more, 0.5 μm or more, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm, or 5 μm or more, and may also be 100 μm or less, 70 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, 10 μm or less, or 5 μm or less.

[0060] The aspect ratio of the fibrous particles is not particularly limited and may be, for example, 2.5 or more, 5 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 50 or more, 100 or more, 150 or more, 200 or more, 250 or more, 500 or more, 1000 or more, 2500 or more, or 5000 or more, and may also be 10000 or less, 7500 or less, 5000 or less, 2500 or less, 1000 or less, 750 or less, 500 or less, 250 or less, 100 or less, 75 or less, 50 or less, 40 or less, or 35 or less.

[0061] The content of fibrous particles is not particularly limited and can be set as appropriate, for example, taking into consideration the desired conductivity.

[0062] (Relationship with tetrapod-shaped particles) In the electrode composite material of this disclosure, the ratio of the length of one side of the tetrapod-shaped particles to the fiber length of the fibrous particles may be 0.5 or more and 20 or less. This ratio may be 0.5 or more, 1 or more, 2 or more, 3 or more, or 4 or more, and may be 20 or less, 10 or less, 8 or less, 5 or less, or 4 or less.

[0063] <Solid electrolyte> The electrode composite material of this disclosure may further contain a solid electrolyte. The solid electrolyte is not particularly limited and includes, for example, inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes, and organic polymer electrolytes such as polymer electrolytes. The solid electrolyte may be a sulfide solid electrolyte in particular.

[0064] When the electrode composite material of this disclosure is an electrode composite material for a lithium-ion secondary battery, the lithium-ion conductive sulfide solid electrolyte may be, for example, a solid electrolyte containing Li, X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S. The sulfide solid electrolyte may further contain at least one of O and halogen elements. The halogen elements may be, for example, F, Cl, Br, and I.

[0065] Sulfide solid electrolytes include, 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-ZmSn (where m and n are positive numbers, and Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (However, x and y are positive numbers. M may be one of P, Si, Ge, B, Al, Ga, or In.)

[0066] The content of the solid electrolyte is not particularly limited and can be set as appropriate, taking into consideration the desired ionic conductivity, etc.

[0067] <Other ingredients> The electrode composite material may further contain components other than those mentioned above. Such components are not particularly limited and may include, for example, conductive additives, binders, etc.

[0068] The conductive additive may be the same as the fibrous carbon described above, or it may be different. The conductive additive may be, for example, a carbon material, metal particles, or a combination thereof. The carbon material may be, for example, a non-fibrous carbon material such as acetylene black (AB) or Ketjenblack (KB); a fibrous carbon material such as vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), or carbon nanofiber (CNF), or a combination thereof. The metal particles may be, for example, nickel, copper, iron, stainless steel, or a combination thereof.

[0069] The binder may be the same as or different from the binder used to form the electrode active material composite particles described above. Examples of binders include rubber-based binders such as butadiene rubber, hydrogenated butadiene rubber, styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, acrylate butadiene rubber (ABR), and ethylene propylene rubber; fluoride-based binders such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluororubber; polyolefin-based thermoplastic resins such as polyethylene, polypropylene, and polystyrene; imide-based resins such as polyimide and polyamide-imide; amide-based resins such as polyamide; acrylic-based resins such as polymethyl acrylate and polyethyl acrylate; methacrylic-based resins such as polymethyl methacrylate and polyethyl methacrylate; or combinations thereof.

[0070] The content of other components in the electrode mixture is not particularly limited.

[0071] <<Battery>> The battery of this disclosure has an electrode active material layer, and the electrode active material layer contains the electrode composite material of this disclosure. The battery of this disclosure may have a negative electrode current collector layer, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order. In this case, the electrode active material layer containing the electrode composite material of this disclosure may be a negative electrode active material layer or a positive electrode active material layer, and may be particularly a negative electrode active material layer.

[0072] The battery described herein may be a liquid-based battery or a solid-state battery, and may be a solid-state battery in particular. In this disclosure, "solid-state battery" means a battery that uses at least a solid electrolyte as its electrolyte, and therefore a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as its electrolyte. Furthermore, a solid-state battery may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as its electrolyte.

[0073] The battery described herein may be a primary battery or a secondary battery, and may be a lithium-ion secondary battery in particular.

[0074] The battery of this disclosure can be restrained from both sides in the stacking direction of each layer by restraining members such as end plates. Examples of restraining methods include, but are not limited to, methods that utilize the restraining torque of bolts.

[0075] The following describes each element constituting the battery of this disclosure. The following examples illustrate the case where the electrode active material layer containing the electrode composite material of this disclosure is the negative electrode active material layer.

[0076] <Negative electrode current collector layer> The negative electrode current collector layer may be in the form of foil, plate, mesh, perforated metal, foam, etc. The negative electrode current collector layer may be metal foil or metal mesh, or a carbon sheet, and may be metal foil in particular. The negative electrode current collector layer may consist of multiple foils, sheets, etc.

[0077] The metal constituting the negative electrode current collector layer is not particularly limited and may be, for example, copper, nickel, chromium, gold, platinum, silver, aluminum, iron, titanium, zinc, cobalt, stainless steel, etc. In particular, the negative electrode current collector layer may contain at least one metal selected from copper, nickel, and stainless steel.

[0078] A coating layer may be formed on the surface of the negative electrode current collector layer for purposes such as adjusting resistance. Alternatively, the negative electrode current collector layer may be made of metal foil or a substrate to which the above-mentioned metal has been plated or deposited. Furthermore, if the negative electrode current collector layer consists of multiple metal foils, there may be some layer between these multiple metal foils.

[0079] The thickness of the negative electrode current collector layer is not particularly limited and may be, for example, 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0080] <Negative electrode active material layer> The negative electrode active material layer includes the electrode mixture of this disclosure. For details of the electrode mixture of this disclosure, refer to the above description relating to the electrode mixture of this disclosure. The negative electrode active material layer may also be formed by molding the electrode mixture of this disclosure itself into layers.

[0081] The thickness of the negative electrode active material layer is not particularly limited and may be, for example, 0.1 μm or more and 1000 μm or less.

[0082] <Solid electrolyte layer> The solid electrolyte layer contains at least a solid electrolyte and may optionally further contain a binder or the like.

[0083] For solid electrolytes and binders, refer to the above description of electrode composites in this disclosure.

[0084] The thickness of the solid electrolyte layer is not particularly limited and may be, for example, 0.1 μm or more and 1000 μm or less.

[0085] <Cathode active material layer> The positive electrode active material layer contains at least a positive electrode active material and may optionally further contain a solid electrolyte, a conductive additive, a binder, etc.

[0086] The positive electrode active material is not particularly limited and may be, for example, an oxide active material. When the battery of this disclosure is a lithium-ion secondary battery, the oxide active material may be, for example, LiCoO2, LiMnO2, Li2NiMn3O8, LiVO2, LiCrO2, LiFePO4, LiCoPO4, LiNiO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 It may be O2 or the like. Furthermore, a coating layer containing a Li ion conductive oxide, such as LiNbO3, may be formed on the surface of these active materials.

[0087] The amount of positive electrode active material in the positive electrode active material layer is not particularly limited.

[0088] For solid electrolytes, conductive additives, and binders, refer to the above description of electrode composites in this disclosure.

[0089] The thickness of the positive electrode active material layer is not particularly limited and may be, for example, 0.1 μm or more and 1000 μm or less.

[0090] <Positive electrode current collector layer> The positive electrode current collector layer may be in the form of foil, plate, mesh, perforated metal, foam, etc. The positive electrode current collector layer may be metal foil or metal mesh, and in particular may be metal foil. The positive electrode current collector layer may consist of multiple foils.

[0091] The metals constituting the positive electrode current collector layer may be copper, nickel, chromium, gold, platinum, silver, aluminum, iron, titanium, zinc, cobalt, stainless steel, etc., and in particular, the positive electrode current collector layer may contain aluminum.

[0092] A coating layer may be formed on the surface of the positive electrode current collector layer for purposes such as adjusting resistance. The positive electrode current collector layer may also be a metal foil or substrate with the above-mentioned metal plated or deposited onto it. Furthermore, if the positive electrode current collector layer consists of multiple metal foils, there may be some layer between these multiple metal foils.

[0093] The thickness of the positive electrode current collector layer is not particularly limited and may be, for example, 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0094] <Other configurations> The battery may have all of the above components housed inside an outer casing. Any known battery casing can be used. Furthermore, multiple batteries may be electrically connected and stacked as desired to form a battery pack. In this case, the battery pack may be housed inside a known battery case. The battery may also have other obvious components such as necessary terminals. The shape of the battery may be, for example, coin-type, laminated (pouch) type, cylindrical, or rectangular.

[0095] <Battery manufacturing method> A method for manufacturing the battery of the present disclosure is not particularly limited and includes, for example, forming an electrode active material layer containing the electrode composite material of the present disclosure.

[0096] An example of a method for forming an electrode active material layer containing an electrode composite is to mix constituent materials such as electrode active material particles to obtain an electrode composite, and then dry-mold or wet-molded the obtained electrode composite.

[0097] In particular, if the battery is a solid-state battery, the electrode active material layer may be press-molded to increase densification. Since the electrode active material layer contains tetrapod-shaped particles, such pressing maintains the voids formed within the electrode active material composite particles.

[0098] A method for manufacturing a battery according to the present disclosure may further include forming an electrode stack by stacking a negative electrode current collector layer, a negative electrode active material layer, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in this order.

[0099] Other components, such as terminals, are attached to the electrode stack as needed. The battery is obtained by housing the electrode stack in a battery case and sealing it. [Examples]

[0100] <<Example 1>> <Fabrication of nanoporous silicon particles> 0.65 g of Si particles (particle size 0.5 μm, manufactured by Kojunsei Kagaku Co., Ltd.) and 0.60 g of Li metal (manufactured by Honjo Kinzoku Co., Ltd.) were mixed in an agate mortar under an Ar atmosphere to obtain a LiSi precursor. In a glass reactor under an Ar atmosphere, 1.0 g of the LiSi precursor and 125 ml of dispersion medium (1,3,5-trimethylbenzene, manufactured by Nacalai Tesque) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.). The resulting LiSi precursor dispersion was cooled to 0°C, and 125 ml of ethanol (manufactured by Nacalai Tesque) as a Li extraction solvent was added dropwise, and the mixture was reacted for 120 minutes. After the reaction, 50 ml of acetic acid (manufactured by Nacalai Tesque) was added dropwise, and the mixture was reacted for another 60 minutes. After the reaction, the liquid and solid reactants were separated by suction filtration. The obtained solid reactants were vacuum-dried at 120°C for 2 hours to obtain nanoporous Si containing multiple pores with a diameter of 55 nm or less.

[0101] <Formation of the negative electrode active material layer> To 3 g of tetralin as a solvent, 0.5 g of prepared Si particles (average particle size: 1 μm), 30 mg of zinc oxide particles (side length: 10 μm) as tetrapod-shaped particles, 0.8 g of sulfide solid electrolyte, and 0.3 g of a 5 wt% styrene-butadiene rubber (SBR) tetralin solution as a binder were added. The mixture was dispersed for 10 minutes using ultrasound at an amplitude of 40 μm and a frequency of 20 kHz to obtain a negative electrode mixture slurry. The obtained slurry was blade-coated onto a roughened nickel (Ni) foil as a negative electrode current collector layer with a gap of 300 μm. This resulted in a negative electrode active material layer formed in layers from the electrode mixture of this disclosure.

[0102] <Formation of the solid electrolyte layer> 0.8 g of heptane as a solvent, 0.4 g of sulfide solid electrolyte, and 0.05 g of a 5 wt% acrylate butadiene rubber (ABR) heptane solution as a binder were added and dispersed by sonication for 10 minutes to obtain a solid electrolyte mixture slurry. The obtained slurry was coated onto stainless steel foil as a release sheet with a gap of 50 μm. This obtained a solid electrolyte layer. Two of these solid electrolyte layers were formed.

[0103] <Formation of the positive electrode active material layer> To 1 g of butyl butyrate as a solvent, 2 g of lithium nickel-cobalt-manganate (NCM) as the positive electrode active material, 0.03 g of VGCF-H as a conductive additive, 0.3 g of sulfide solid electrolyte, and 0.3 g of PVDF-HFP 5 wt% butyl butyrate solution as a binder were added and dispersed by sonication for 10 minutes to obtain a positive electrode mixture slurry. The obtained slurry was blade-coated onto aluminum foil, which served as the positive electrode current collector layer, with a gap of 200 μm. This obtained the positive electrode active material layer.

[0104] <Battery manufacturing> The first solid electrolyte layer was placed on top of the negative electrode active material layer and roll-pressed at a linear pressure of 3 t / cm at room temperature. The second solid electrolyte layer was placed on top of the positive electrode active material layer and roll-pressed at a linear pressure of 4 t / cm at 170°C. Each layer was rolled to 1 cm. 2The solid electrolyte layers, from which the stainless steel foil had been removed, were punched out and then joined together. This resulted in the battery of Example 1.

[0105] <Rating> The battery was restrained at 5 MPa, and charge-discharge tests were conducted while recording the load cell values. For the negative electrode active material, the restraining pressure (MPa) at the point when 1000 mAh was charged was compared with the value obtained by dividing the cell's initial charge capacity (mAh) (MPa / mAh). The values ​​of the restraining pressure fluctuations were used when the battery was charged at a rate of 1 / 10C using constant current-constant voltage (CCCV) until 4.35V, discharged at 1 / 3C using CCCV until 3.35V, and then charged again using CCCV.

[0106] <<Example 2>> The battery of Example 2 was obtained and evaluated in the same manner as in Example 1, except that the zinc oxide particles used as tetrapod-shaped particles were changed to those listed in Table 1. For convenience, in Table 1, tetrapod-shaped particles and their substitute compounds are shown as fillers.

[0107] <<Comparative Example 1>> A battery for Comparative Example 1 was obtained and evaluated in the same manner as in Example 1, except that tetrapod-shaped particles were not used.

[0108] <<Comparative Example 2>> A battery for Comparative Example 2 was obtained and evaluated in the same manner as in Example 1, except that alumina particles were used as a substitute compound for tetrapod-shaped particles.

[0109] Table 1 shows the evaluation results of the confinement pressure fluctuations of the batteries in Examples 1 and 2, and Comparative Examples 1 and 2.

[0110] [Table 1]

[0111] As shown in Table 1, the battery in the example containing tetrapod-shaped particles in the electrode mixture showed small fluctuations in confinement pressure.

[0112] <<Example 3>> <Fabrication of electrode active material composite particles> The above-mentioned nanoporous Si (primary particles) and a PVDF-HFP-based binder (manufactured by Kureha Corporation) were dispersed and partially dissolved in dimethyl carbonate (manufactured by Nacalai Tesque) in a ratio (mass ratio) of nanoporous Si:binder = 100:13.3 to obtain a slurry. This slurry was sprayed into a spray dryer under a nitrogen gas atmosphere at 140°C and dried to obtain electrode active material composite particles containing nanoporous Si and binder.

[0113] A battery of Example 3 was obtained and evaluated in the same manner as in Example 1, except that the obtained electrode active material composite particles were used as the electrode active material.

[0114] <<Example 4, and Comparative Examples 3 and 4>> Except for using the electrode active material composite particles obtained in Example 3 as the electrode active material, batteries for Example 4 and Comparative Examples 1 and 2 were obtained and evaluated in the same manner as in Example 2 and Comparative Examples 1 and 2, respectively.

[0115] Table 1 shows the evaluation results of the confinement pressure fluctuations of the batteries in Examples 3 and 4, and Comparative Examples 3 and 4.

[0116] [Table 2]

[0117] As shown in Table 2, the batteries in the examples containing tetrapod-shaped particles in the electrode mixture exhibited smaller confinement pressure fluctuations. Furthermore, the batteries in Examples 3 and 4 showed even smaller confinement pressure fluctuations than those in Examples 1 and 2. This is thought to be because the tetrapod-shaped particles in the electrode mixture functioned as pillars, making it difficult for the voids within the electrode active material composite particles to collapse even when pressed during battery fabrication.

[0118] <<Examples 5 and 6>> The batteries of Examples 5 and 6 were obtained and evaluated in the same manner as in Example 4, except that the volume ratio (ZnO / Si) of zinc oxide particles as tetrapod-shaped particles to the content of electrode active material composite particles was changed as shown in Table 3. The results are shown in Table 3. For reference, Example 4 is also included in Table 3.

[0119] [Table 3]

[0120] As shown in Table 3, the constraint pressure fluctuation was small for all of the battery volume ratios (ZnO / Si) examined, and the constraint pressure fluctuation was smallest in the battery of Example 5 in particular.

[0121] <<Example 7>> The battery of Example 7 was obtained and evaluated in the same manner as in Example 4, except that VGCF (fiber length: 5 μm) was added as fibrous particles during the preparation of the negative electrode mixture slurry. The results are shown in Table 4. For reference, Example 4 is also included in Table 4.

[0122] <<Comparative Example 5>> The battery of Comparative Example 5 was prepared in the same manner as in Comparative Example 3, except that VGCF (fiber length: 5 μm) was added as fibrous particles during the preparation of the negative electrode mixture slurry, and was evaluated. The results are shown in Table 4. For reference, Comparative Example 3 is also included in Table 4.

[0123] <Strength of the negative electrode active material layer> The laminate of the negative electrode active material layer and the negative electrode current collector layer before densification was punched out to a diameter of φ11.28 mm, and the negative electrode current collector layer side was attached to a base with double-sided tape. Double-sided tape was also attached to the negative electrode active material layer side, and the tip of a tensile testing machine was attached to the adhesive surface of the double-sided tape opposite to the negative electrode active material layer side, and pressed with 50 N to ensure tight adhesion of the double-sided tape. A tensile test was then performed, and the maximum load was defined as the peel strength. Note that this peel strength refers to the strength against cohesive failure in the negative electrode active material layer, and therefore does not refer to the strength against peeling between the negative electrode active material layer and the negative electrode current collector layer. The high peel strength suggests that the VGCF is also oriented in the thickness direction.

[0124] [Table 4]

[0125] As shown in Table 4, the battery of Example 7, which contained zinc oxide particles as tetrapod-shaped particles and VGCF as fibrous particles in the electrode mixture, showed the smallest fluctuation in confinement pressure. This is thought to be because the tetrapod-shaped particles in the electrode mixture oriented the VGCF in the thickness direction, thereby improving the function of VGCF as a conductive additive, and thus making it easier for the electrode reaction to occur uniformly, as well as improving the strength of the electrode mixture as an electrode active material layer. [Explanation of Symbols]

[0126] 1 Electrode composite material (electrode active material layer) 10 Electrode active material particles (electrode active material composite particles) 20 Tetrapod-shaped particles 30 fibrous particles

Claims

1. Electrode active material particles, and Tetrapod-shaped particles An electrode composite material containing this material.

2. The electrode composite material according to claim 1, wherein the ratio of the length of one side of the tetrapod-shaped particle to the average particle diameter of the electrode active material particle is 1 or more and 50 or less.

3. The electrode composite material according to claim 1, wherein the electrode active material particles form electrode active material composite particles.

4. The electrode composite material according to claim 3, wherein the ratio of the length of one side of the tetrapod-shaped particle to the average particle diameter of the electrode active material composite particle is 0.1 or more and 10 or less.

5. The electrode mixture according to claim 1, further comprising fibrous particles.

6. The electrode composite material according to claim 5, wherein the fibrous particles are vapor-grown carbon fibers.

7. The electrode composite material according to claim 5, wherein the ratio of the length of one side of the tetrapod-shaped particle to the fiber length of the fibrous particle is 0.5 or more and 20 or less.

8. The electrode composite material according to claim 1, wherein the electrode active material particles are alloy-based electrode active material particles.

9. The electrode composite material according to claim 8, wherein the alloy electrode active material particles are silicon particles.

10. The electrode mixture according to claim 1, wherein the tetrapod-shaped particles are zinc oxide particles.

11. The electrode mixture according to claim 1, wherein the ratio of the content of the tetrapod-shaped particles to the content of the electrode active material particles is 1.0 volume% or more and 6.0 volume% or less.

12. The electrode mixture according to claim 1, further comprising a solid electrolyte.

13. The electrode composite material according to claim 12, wherein the solid electrolyte is a sulfide solid electrolyte.

14. It has an electrode active material layer, and A battery in which the electrode active material layer contains the electrode composite material according to any one of claims 1 to 13.

15. The battery according to claim 14, which is a solid-state battery.

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