Composite particles, electrode mixture, electrode layer, battery, and method for producing electrode layer

Abstract

The invention relates to composite particles, an electrode mixture, an electrode layer, a battery, and a method for manufacturing the electrode layer. The main purpose of the present invention is to provide composite particles capable of suppressing battery resistance. The present disclosure solves the problem by providing composite particles containing a binder and a plurality of active materials containing an Si element or an Sn element, the composite particles having a first portion containing the active materials and a second portion not containing the active materials when the composite particles are viewed in cross section, and the proportion of the second portion in the composite particles is 55% or less.

Description

Technical Field

[0001] The present disclosure relates to composite particles, an electrode composite material, 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 for electric vehicles (BEVs), plug-in hybrid vehicles (PHEVs), or hybrid vehicles (HEVs) has been promoted. In addition, the development of components and materials for the above batteries has been promoted.

[0003] For example, Patent Document 1 discloses a negative electrode layer containing composite particles and having a porosity of 15% or less, the composite particles having a plurality of particles containing an Si element or an Sn element, and a binder.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-121557 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] Si and Sn have a large theoretical capacity and are effective for increasing the energy density of batteries. However, the volume change during charge and discharge is large, and the volume change (expansion and contraction amount) of the electrode layer using Si or Sn may become large. If the volume change of the electrode is large, the ion conduction path may be cut off and the battery resistance may increase. In this regard, as in Patent Document 1, it has been studied to absorb the expansion of the composite particles by providing voids in the negative electrode layer, thereby suppressing the cutting off of the ion conduction path and suppressing the battery resistance. On the other hand, there is still room for further improvement in suppressing the battery resistance.

[0009] The present disclosure has been completed in view of the above actual situation, and the main object is to provide composite particles capable of suppressing battery resistance.

[0010] Means for Solving the Problems

[0011] [1] Composite particles containing: a plurality of active materials containing an Si element or an Sn element, and a binder, wherein when the cross-section of the composite particles is observed, the composite particles have a first part containing the active materials and a second part not containing the active materials, and the proportion of the second part in the composite particles is 55% or less.

[0012] [2] The composite particles according to [1], wherein the proportion is 30% or more.

[0013] [3] The composite particles according to [1] or [2], wherein the active material contains the Si element and has voids inside.

[0014] [4] The composite particles according to any one of [1] to [3], wherein the active material contains the Si element and has a silicon inclusion type crystal phase.

[0015] [5] An electrode composite material containing the composite particles according to any one of [1] to [4].

[0016] [6] An electrode layer is an electrode layer containing composite particles, the composite particles containing: a plurality of active materials containing the Si element or the 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.

[0017] [7] The electrode layer according to [6], wherein the aspect ratio is 3.0 or less.

[0018] [8] The electrode layer according to [6] or [7], wherein the aspect ratio is 1.6 or more.

[0019] [9] The electrode layer according to any one of [6] to [8], wherein the electrode layer contains a conductive additive and a solid electrolyte.

[0020]

[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 [6] to [9].

[0021]

[11] The battery according to

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

[0022]

[12] A method for manufacturing an electrode layer, comprising: a preparation step of preparing an electrode composite material containing the composite particles according to any one of [1] to [4]; a precursor layer formation step of forming a precursor layer using the electrode composite material; and an electrode layer formation step of applying a pressing pressure to the precursor layer to form an electrode layer, wherein in the electrode layer formation step, the pressing pressure is applied in such a manner that 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 becomes 3.6 or less.

[0023]

[13] The method for manufacturing an electrode layer according to

[12] , wherein in the electrode layer formation step, the pressing pressure is applied by roll pressing, and the pressing pressure is 30 kN / cm or more and 100 kN / cm or less.

[0024] Effects of the Invention

[0025] When the composite particles of the present disclosure are used in a battery, an effect of suppressing the battery resistance can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A diagram for explaining a method of measuring the ratio of the second part in the present disclosure.

[0027] Figure 2 A diagram for explaining the crystal phase of the Si-based active material in the present disclosure.

[0028] Figure 3 A diagram for explaining a method of measuring the aspect ratio in the present disclosure.

[0029] Figure 4 A schematic cross-sectional view of an example of the battery in the present disclosure.

[0030] Figure 5 A flowchart exemplifying a method of manufacturing an electrode layer in the present disclosure.

[0031] Figure 6 A coordinate diagram showing the results of the examples and comparative examples.

[0032] DESCRIPTION OF REFERENCE NUMERALS

[0033] 1... Positive electrode active material layer

[0034] 2... Negative electrode active material layer

[0035] 3... Electrolyte layer

[0036] 4... Positive electrode current collector

[0037] 5... Negative electrode current collector

[0038] 10... Battery DETAILED DESCRIPTION

[0039] Hereinafter, the composite particles, electrode composite materials, electrode layers, batteries, and methods for manufacturing electrode layers in the present disclosure will be described in detail.

[0040] A. Composite Particles

[0041] The composite particles in the present disclosure contain: a plurality of active materials containing Si element or Sn element, and a binder. In addition, when observing the cross section of the composite particles, 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. Herein, in the present specification, the active material containing Si element may sometimes be referred to as Si-based active material, and the active material containing Sn element may sometimes be referred to as Sn-based active material.

[0042] The composite particles in the present disclosure contain a specified active material and a binder, and have a specified second part in cross-sectional observation. Therefore, the second part absorbs expansion and can 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.

[0043] In addition, in the composite particles in the present disclosure, since the proportion of the second part is 55% or less, a specified aspect ratio can be achieved within the electrode layer. As will be described in detail later, it is speculated that by having a specified aspect ratio of the composite particles within the electrode layer, the curvature of the ion conduction path in the electrode layer can be reduced. As a result, the non-uniformity of the reaction in the thickness direction of the electrode layer can be suppressed, the volume change amount of the electrode layer can be suppressed, and the battery resistance can be suppressed.

[0044] When the composite particles in the present disclosure are observed in cross-section, they have a first part containing a Si-based active material or a Sn-based active material and a second part not containing the above-mentioned active material. The second part generally refers to the part containing voids or a binder formed between adjacent active materials. It should be noted that, as described later, when the Si-based active material has voids inside, the void part inside the Si-based active material is included in the above-mentioned first part.

[0045] The proportion of the above-mentioned second part can be 50% or less, can be 45% or less, can be 40% or less. On the other hand, the proportion of the above-mentioned second part is, for example, 30% or more, and can be 35% or more.

[0046] Among them, the proportion of the above-mentioned second part can be calculated by the following method, for example. First, as shown in Figure 1 (a), a cross-sectional image of the composite particles is obtained using a scanning electron microscope (SEM). A more specific method for obtaining the cross-sectional image is described in the examples. Secondly, as shown in Figure 1 (b), the cross-sectional image is subjected to image analysis, and the first part containing the Si-based active material or the Sn-based active material (the deep part in Figure 1 (b)) and the second part not containing the above-mentioned active material (the light part in Figure 1 (b)) are binarized. Then, in the binarized image, using image analysis software, the proportion of the area of the second part to the total area of the first part and the second part is calculated. The proportion of the second part in the present disclosure is preferably the average value of 10 or more samples (composite particles) measured. The number of samples can be 20 or more, can be 50 or more, can be 100 or more.

[0047] The composite particles in the present disclosure contain: a plurality of active materials containing Si element or Sn element, and a binder. The composite particles can be regarded as aggregates formed by the aggregation of a plurality of the above active materials (Si-based active materials or Sn-based active materials). Furthermore, the above active materials can be primary particles or secondary particles formed by the aggregation of primary particles.

[0048] The active material containing Si element (Si-based active material) may be Si single substance, an alloy containing Si as a main component (Si alloy), or Si oxide. The proportion of Si element in the Si alloy is, for example, 50 mol% or more and 95 mol% or less.

[0049] In addition, the Si-based active material may have voids inside. Furthermore, the Si-based active material with voids is called porous Si. Whether there are voids can be confirmed by SEM (scanning electron microscope) observation. In addition, there is no particular limitation on the porosity, for example, it is greater than 4%, and can be greater than 10%. In addition, the above-mentioned porosity is, for example, less than 40%, and can be less than 20%. The porosity can be obtained, for example, by the following steps. 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 binarization is performed. The areas of the silicon part and the void part are obtained, and the porosity (%) is calculated by the following formula.

[0050] Void ratio (%) = 100 × (void area) / ((silicon area) + (void area))

[0051] In the 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. In addition, the BET specific surface area of the porous Si is, for example, 20 m 2 / g or more and 200m 2 / g or less.

[0052] As a method for preparing porous Si, for example, the following method can be cited: preparing an alloy of Li and Si (LiSi alloy), and then removing Li from the LiSi alloy. The LiSi alloy is obtained, for example, by mixing Li and Si. As a method for removing Li from the LiSi alloy, for example, a method for reacting the LiSi alloy with a Li extraction material can be cited. As the Li extraction material, for example, alcohols such as methanol and acids such as acetic acid can be cited.

[0053] in, Figure 2 This is a schematic three-dimensional diagram to illustrate the crystal phase of Si. Generally, Si has Figure 2 (a) shows a diamond-type crystal phase. The Si-based active material in the present disclosure may have Figure 2 (b) and (c) show the silicon inclusion type crystal phase.Figure 2 In the diamond-type crystal phase shown in (a), a plurality of Si elements are used to form tetrahedrons. The interior of the tetrahedron does not have a space that can accommodate metal ions such as Li ions. On the other hand, Figure 2 The skeleton atoms of the silicon inclusion type I and II crystal phases shown in (b) and (c) have a cage-like structure (cage), and metal ions such as Li ions can enter therein, thereby further suppressing the expansion and contraction of the composite particles, and as a result, further suppressing the expansion and contraction of the electrode layer. In addition, Si-based active materials having a silicon inclusion type crystal phase are called inclusion Si, and in particular, Si-based active materials having the above-mentioned voids and an inclusion type crystal phase are called porous inclusion Si (pc-Si).

[0054] The Si-based active material may have a silicon inclusion compound type I crystal phase, or may have a silicon inclusion compound type II crystal phase. In particular, the Si-based active material preferably has a silicon inclusion compound type II crystal phase as the main phase. The so-called "main phase" refers to the peak belonging to the crystal phase having the largest diffraction intensity among the peaks observed by X-ray diffraction measurement. The proportion of the silicon inclusion compound type II crystal phase contained in the Si-based active material is, for example, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. In addition, the proportion of the silicon inclusion compound type II crystal phase contained in the Si-based active material may be 100% by weight or less than 100% by weight. The proportion of the crystal phase can be obtained by using the RIR method (Reference Intensity Ratio method).

[0055] As a method for producing porous inclusion Si, for example, the following method can be listed: the above-mentioned porous Si is mixed with a Na source such as NaH and heated to produce a Na-Si alloy, and the Na-Si alloy is heated to reduce the amount of Na in the Na-Si alloy to generate a silicon inclusion type crystal phase.

[0056] The active material containing the Sn element (Sn-based active material) may be a single substance of Sn, an alloy containing Sn as a main component (Sn alloy), or a Sn oxide. The proportion of the Sn element in the Sn alloy is, for example, 50 mol% or more and 95 mol% or less.

[0057] The ratio of the Si-based active material or the Sn-based active material in the composite particles is, for example, 90% by weight or more and 99% by weight or less.

[0058] There is no particular limitation on the binder in the present disclosure. As the binder, for example, polyimide-based binders can be cited; 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). The binder can be used alone or in combination of multiple kinds.

[0059] The proportion of the binder in the composite particles is, for example, 0.5% by weight or more and 10% by weight or less.

[0060] The average particle diameter (D 50 ) of the composite particles is, for example, 1 μm or more and 100 μm or less. The so-called average particle diameter (D 50 ) refers to the volume cumulative particle diameter measured by the laser diffraction scattering particle size distribution measurement method. In addition, the average particle diameter (D 50 ) of the above active material is, for example, 0.1 μm or more and 3 μm or less. The number of the above active materials contained in the composite active material is, for example, 10 or more and 150 or less. There is no particular limitation on the use of the composite particles, and they are preferably used in batteries.

[0061] B. Electrode composite

[0062] The electrode composite in the present disclosure contains the above composite particles. In addition, the electrode composite may further contain at least one of a conductive additive, a binder, and an electrolyte as needed.

[0063] According to the present disclosure, since it contains the above composite particles, when used in a battery, it can suppress the battery resistance.

[0064] There is no particular limitation on the proportion of the composite particles in the electrode composite. For example, it is 50% by weight or more, can be 70% by weight or more, and can be 90% by weight or more. On the other hand, the proportion of the composite particles is, for example, 99% by weight or less and can be 95% by weight or less.

[0065] As the conductive additive, for example, carbon materials can be cited. As the carbon materials, for example, particulate carbon materials such as acetylene black (AB) and Ketjen black (KB); fibrous carbon materials such as carbon fiber, carbon nanotube (CNT), and carbon nanofiber (CNF) can be cited. The proportion of the conductive additive in the electrode composite is, for example, 0.01% by weight or more and 10% by weight or less, and can be 0.1% by weight or more and 5% by weight or less.

[0066] For the binder, the binders described in "A. Composite particles" can be listed. The binder in the composite particles and the binder in the electrode composite material can be of the same type or different types. The proportion of the binder in the electrode composite material is, for example, 0.5% by weight or more and 10% by weight or less, and can be 1% by weight or more and 5% by weight or less.

[0067] The electrode composite material preferably contains a solid electrolyte as the electrolyte. As the solid electrolyte, for example, inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes can be listed. The sulfide solid electrolyte preferably contains sulfur (S) as the main component of the anion element. The oxide solid electrolyte preferably contains oxygen (O) as the main component of the anion element. The halide solid electrolyte preferably contains a halogen as the main component of the anion. Among these, a sulfide solid electrolyte is preferred.

[0068] The sulfide solid electrolyte preferably contains Li element, M element (M is at least one of P, Sn, Al, Zn, In, Ge, Si, Sb, Ga, and Bi), and S element. In addition, the sulfide solid electrolyte may contain halogen elements such as F, Cl, Br, and I. In addition, in the sulfide solid electrolyte, a part of the S element may be replaced by the O element.

[0069] The sulfide solid electrolyte can be a glassy (amorphous) sulfide solid electrolyte, a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. As the crystal phase contained in the sulfide solid electrolyte, for example, LGPS type crystal phase, Thio-LISICON type crystal phase, and argyrodite type crystal phase can be listed.

[0070] As the sulfide solid electrolyte, for example, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers. Z is any one of Ge, Zn, and Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.).

[0071] 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 can be 40% by weight or more and 70% by weight or less.

[0072] 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 can be a slurry. On the other hand, the electrode composite material can be a powder. As the organic solvent, for example, organic solvents conventionally known in the field of batteries such as butyl butyrate can be cited.

[0073] C. Electrode layer

[0074] The electrode layer in the present disclosure is an electrode layer containing composite particles, and the composite particles contain: a plurality of active substances 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. It should be noted that the so-called "cross-sectional shape of the composite particles in the above electrode layer" means the cross-sectional shape of the composite particles that can be observed when the electrode layer is observed in cross-section in the thickness direction.

[0075] The aspect ratio in the present disclosure refers to the ratio (b / a) of the major axis b to the minor axis a of the composite particles obtained when the cross-sectional shape of the composite particles is approximated to an ellipse. Here, it is assumed that the electrode layer is fabricated by applying a pressing pressure as described later. That is, it is assumed that the composite particles are included in the electrode layer in a state compressed 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 up-down direction of the paper surface in the following Figure 3 ). In addition, the major axis b of the composite particles can be regarded as the length of the composite particles in the direction crossing the thickness direction of the electrode layer (the left-right direction of the paper surface in the following Figure 3 ).

[0076] According to the present disclosure, since it contains composite particles with a specified aspect ratio of 3.6 or less, an electrode layer capable of suppressing battery resistance is obtained.

[0077] Among them, generally, carrier ions move in the electrode layer through an electrolyte portion with good ion conductivity. That is, the ion conduction path of the carrier ions bends in a way that bypasses the composite particles. Therefore, when the aspect ratio is greater than 3.6, the distance to bypass 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. In the electrode layer in 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 the increase in battery resistance caused by the increase in ion conduction resistance can be suppressed.

[0078] The aspect ratio can be 3.5 or less, can be 3.3 or less, can be 3.0 or less, can be 2.8 or less. On the other hand, the aspect ratio is, for example, 1.5 or more, can be 1.6 or more, can be 1.8 or more, can be 2.0 or more, can be 2.3 or more, can be 2.5 or more.

[0079] The minor axis a and the major axis b of the composite particles are not particularly limited as long as they satisfy the above aspect ratio. The minor axis a is, for example, 0.1 μm or more and 30 μm or less. In addition, the major axis b is, for example, 1.0 μm or more and 100 μm or less.

[0080] Among them, the above minor axis, major axis, and aspect ratio can be calculated by, for example, the following method. First, as Figure 3 (a) shows, a cross-sectional image of the electrode layer is obtained using a scanning electron microscope (SEM). Secondly, as Figure 3 (b) shows, for the cross-sectional image, image analysis is performed to binarize the part of the composite particles (black) and the part outside the composite particles (white). Furthermore, the part of the composite particles and other parts can be distinguished by, for example, elemental analysis such as SEM-EDX. Secondly, as Figure 3 (c) shows, in the binarized image, the part of the composite particles is approximated as an ellipse using image analysis software. Moreover, as Figure 3 (d) shows, for each composite particle approximated as an ellipse, the minor axis, major axis, and area are measured, and 10 composite particles are selected in the order of the largest cross-sectional area. From the minor axis and major axis of each selected composite particle, the aspect ratio (major axis / minor axis) is measured, and the average value of the measured aspect ratios is taken as the aspect ratio in the present disclosure.

[0081] The number of selected composite particles can be more than 10. The number of selected composite particles can be 30 or more, can be 50 or more, can be 100 or more. In addition, as the observation field of view of the SEM image, it is preferably set to a field of view including the above-mentioned number or more of composite particles. The observation field of view is, for example, 1000 μm 2 or more and 50000 μm 2 or less. In addition, as the image analysis software, for example, ImageJ Fiji can be used.

[0082] Regarding the composite particles, it is the same as the content described in "A. Composite Particles". Among them, it is assumed that the electrode layer is manufactured by applying a pressing pressure as described later. Therefore, it is assumed that the proportion of the second part of the composite particles in the electrode layer decreases compared to before the pressing pressure is applied. In addition, in the case where the composite particles contain porous Si, similarly, it is assumed that the void volume of voids with a pore diameter of 50 nm or less decreases compared to before the pressing pressure is applied.

[0083] The electrode layer may be a positive electrode active material layer containing the above composite particles as a positive electrode active material, or may be a negative electrode active material layer containing the above composite particles as a negative electrode active material, with the latter being preferred. This is because a battery with a high voltage can be obtained. In addition, the electrode layer may further contain at least one of a conductive additive, a binder, and an electrolyte as needed. For the conductive additive, the binder, and the electrolyte, the content is the same as that described in "B. Electrode composite material".

[0084] There is no particular limitation on the thickness of the electrode layer. For example, it is 0.1 μm or more and 1000 μm or less.

[0085] D. Battery

[0086] Figure 4 is a schematic cross-sectional view of the battery in the present disclosure for illustration. Figure 4 The shown battery 10 has a positive electrode active material layer 1, a negative electrode active material layer 2, and an electrolyte layer 3 disposed between the positive electrode active material layer 1 and the negative electrode active material layer 2. In addition, the negative electrode active material layer 2 in the battery 10 is the above-described electrode layer in the present disclosure.

[0087] 1. Positive electrode active material layer

[0088] The positive electrode active material layer contains at least a positive electrode active material, and may contain at least one of a conductive additive, a binder, and an electrolyte as needed. For the conductive additive, the binder, and the electrolyte, the content is the same as that described in "B. Electrode composite material".

[0089] The positive electrode active material is not particularly limited as long as it is an active material having a reaction potential higher than that of the above composite particles. Examples of the positive electrode active material include oxide active materials. Examples of the oxide active materials include LiCoO2, LiNi 0.8 Co 0.15 Mn 0.05 O2 and LiNi 0.33 Co 0.33 Mn 0.33 O2 and other rock salt layer-type active materials; LiMn2O4, Li4Ti5O 12 and other spinel-type active materials; LiFePO4 and other olivine-type active materials. Examples of the shape of the positive electrode active material include particulate form. The average particle size (D 50 ) is, for example, 0.5 μm or more and 50 μm or less. The average particle size (D 50 ) is as described above.

[0090] There is no particular limitation on the thickness of the positive electrode active material layer. For example, it is 0.1 μm or more and 1000 μm or less.

[0091] 2. Negative electrode active material layer

[0092] The negative electrode active material layer is the above-mentioned electrode layer. For the electrode layer, it is the same as that described in "C. Electrode layer".

[0093] 3. Electrolyte layer

[0094] The electrolyte layer contains an electrolyte. The electrolyte is preferably a solid electrolyte. For the solid electrolyte, it is the same as that described in the above "B. Electrode composite material". In addition, the electrolyte layer may contain a binder as needed. For the binder, it is the same as that described in "B. Electrode composite material". Furthermore, in the present disclosure, the electrolyte layer containing a solid electrolyte is referred to as a solid electrolyte layer, and the battery including the solid electrolyte layer is referred to as an all-solid battery.

[0095] There is no particular limitation on the thickness of the electrolyte layer, for example, it is 0.1 μm or more and 1000 μm or less.

[0096] 4. Other components

[0097] As Figure 4 shown, the battery 10 in the present disclosure generally has a positive electrode current collector 4 that collects electrons of the positive electrode active material layer 1 and a negative electrode current collector 5 that collects electrons of the negative electrode active material layer 2. As materials for the positive electrode current collector, for example, SUS, aluminum, nickel, iron, titanium, and carbon can be cited. As materials for the negative electrode current collector, for example, SUS, copper, nickel, and carbon can be cited.

[0098] In addition, the battery in the present disclosure may include an outer package body that houses the above components. As the outer package body, for example, a laminated outer package body and a housing-type outer package body can be cited. In addition, the battery in the present disclosure may include a constraint jig that applies a constraint pressure in the thickness direction to the above components. As the constraint jig, a known jig can be used. The constraint pressure is, for example, 0.1 MPa or more and 50 MPa or less, and can be 1 MPa or more and 20 MPa or less.

[0099] 5. Battery

[0100] The battery in the present disclosure is typically a lithium-ion secondary battery. In addition, the battery in the present disclosure is preferably an all-solid battery having a solid electrolyte layer as the electrolyte layer. As uses of the battery, for example, power sources for vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), battery electric vehicles (BEV), gasoline vehicles, and diesel vehicles can be cited. In addition, the battery in the present disclosure can be used as a power source for moving bodies other than vehicles (such as railways, ships, and aircraft), and can also be used as a power source for electrical products such as information processing devices.

[0101] E. Manufacturing method of the electrode layer

[0102] Figure 5A flowchart illustrating a method for manufacturing an electrode layer in the present disclosure. As Figure 5 shown, in the method for manufacturing an electrode layer in the present disclosure, first, an electrode composite material containing the above-mentioned composite particles is prepared (preparation step). Next, a precursor layer is formed using the above-mentioned electrode composite material (precursor layer formation step). Then, pressing pressure is applied to the above-mentioned precursor layer to form an electrode layer (electrode layer formation step). In addition, in the above-mentioned electrode layer formation step, the pressing pressure is applied in such a manner that when the cross-sectional shape of the above-mentioned composite particles in the above-mentioned electrode layer is approximated as an ellipse, the aspect ratio of the above-mentioned composite particles becomes 3.6 or less.

[0103] According to the present disclosure, a precursor layer is formed using an electrode composite material containing the above-mentioned composite particles, and pressing pressure is applied to the precursor layer to form an electrode layer containing composite particles having a specified aspect ratio. As a result, when used in a battery, an electrode layer capable of suppressing battery resistance can be manufactured.

[0104] 1. Preparation step

[0105] The preparation step is a step of preparing an electrode composite material containing the above-mentioned composite particles. The composite particles are the same as those described in "A. Composite particles". In addition, the electrode composite material is the same as that described in "B. Electrode composite material".

[0106] 2. Precursor layer formation step

[0107] The precursor layer formation step is a step of forming a precursor layer using the above-mentioned electrode composite material.

[0108] In the precursor layer formation step, as long as a layered precursor layer can be formed from the electrode composite material, the method is not particularly limited. As a method for forming the precursor layer, for example, a coating method using the electrode composite material as a slurry can be cited. Examples of the coating method include a method of coating the electrode composite material on a substrate such as a metal plate and drying it. Regarding the thickness of the precursor layer, as long as an electrode layer having a required thickness can be obtained, it is not particularly limited and can be appropriately adjusted.

[0109] 3. Electrode layer formation step

[0110] The electrode layer formation step is a step of applying pressing pressure to the above-mentioned precursor layer to form an electrode layer. In addition, in the electrode layer formation step, the pressing pressure is applied in such a manner that when the cross-sectional shape of the above-mentioned composite particles in the above-mentioned electrode layer is approximated as an ellipse, the aspect ratio of the above-mentioned composite particles becomes 3.6 or less.

[0111] The method of applying pressing pressure (pressing method) is not particularly limited, and for example, roll pressing and flat pressing can be cited. Regarding the pressing pressure (linear pressure) in roll pressing and the pressing pressure (surface pressure) in flat pressing, as long as the above aspect ratio is obtained, there is no particular limitation. The linear pressure in roll pressing is, for example, 30 kN / cm or more, can be 40 kN / cm or more, and can be 50 kN / cm or more. On the other hand, the linear pressure is, for example, 100 kN / cm or less, can be 80 kN / cm or less, and can be 60 kN / cm or less. In addition, the surface pressure in flat pressing is, for example, 800 MPa or more and 3000 MPa or less. In addition, the above precursor layer can be heated while pressing. The heating temperature is, for example, 80 °C or more and 200 °C or less.

[0112] 4. Electrode layer

[0113] There is no particular limitation on the electrode layer obtained through the above respective processes, and the electrode layer described in "C. Electrode layer" is preferably used.

[0114] Furthermore, the present disclosure is not limited to the above embodiments. The above embodiments are illustrative, and technical solutions having substantially the same constitution as the technical idea described in the claims of the present disclosure and achieving the same effects are included in the technical scope of the present disclosure.

[0115] Examples

[0116] [Example 1]

[0117] (Fabrication of positive electrode)

[0118] A binder (PVDF), a conductive additive, a sulfide solid electrolyte, and a positive electrode active material (NCM: LiNi 0.8 Co 0.15 Mn 0.05 O2) were added to an organic solvent. After addition, a kneading was performed using an ultrasonic homogenizer to obtain an electrode composite material slurry. The obtained electrode composite material slurry was coated on a positive electrode current collector (Al foil) and dried. Thus, a positive electrode having a positive electrode current collector and a positive electrode active material layer was obtained.

[0119] (Fabrication of negative electrode)

[0120] A Si-based active material (pc-Si: average particle diameter (D 50 ) 0.5 μm) was put into a binder solution containing an organic solvent and a binder (PVDF), and mixed to prepare a slurry. Using the spray drying method with this slurry, composite particles containing a Si-based active material and a binder were fabricated.

[0121] For the produced composite particles, the proportion of the second part was measured as described below. The results are shown in Table 1. First, the composite particles and epoxy resin were mixed and cured to obtain a cured product. Second, for the above cured product, cross-section exposure processing using an ion milling method was performed. The cross-section of the processed product was observed by SEM to obtain a cross-sectional image of the composite particles. For the obtained cross-sectional image, it 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 in each composite particle, the proportion of the second part was calculated. Then, the average value of the proportions of the second part of 10 composite particles was obtained. It should be noted that regarding the cross-section of the observed composite particles, as Figure 1 shown, a sea-island structure with the second part as the sea and the first part as the island was observed.

[0122] The composite particles, a binder (PVDF), a conductive additive (VGCF), and a sulfide solid electrolyte (Li2S-P2S5-based sulfide solid electrolyte) were added to an organic solvent, and kneading was performed using an ultrasonic homogenizer. Thus, a negative electrode slurry was produced. The negative electrode slurry was coated on a negative electrode current collector (Cu foil) and dried. Thus, a negative electrode having a negative electrode current collector and a negative electrode active material layer was obtained.

[0123] (Fabrication of Evaluation Battery)

[0124] A binder (PVDF) and a sulfide solid electrolyte (Li2S-P2S5-based sulfide solid electrolyte) were added to an organic solvent, and kneading was performed using an ultrasonic homogenizer. Thus, a composite material slurry was obtained. The composite material slurry was coated on a substrate (Al foil) and dried. Thus, a transfer member having a substrate and a solid electrolyte layer was obtained.

[0125] The produced positive electrode, negative electrode, and transfer member were each formed into a long strip shape. Second, the positive electrode and the transfer member were overlapped with the positive electrode active material layer and the solid electrolyte layer facing each other, and roll-pressed at 165 °C and a pressure of 50 kN / cm. Then, the substrate was peeled off to obtain a positive electrode side member. In addition, the negative electrode and the transfer member were overlapped with the negative electrode active material layer and the solid electrolyte layer facing each other, and roll-pressed at 25 °C and a pressure of 50 kN / cm. Then, the substrate was peeled off to obtain a negative electrode side member. Second, the above negative electrode side member was punched into φ13.00 mm, and the positive electrode side member was punched into φ11.28 mm. A powdered sulfide solid electrolyte was disposed on the solid electrolyte layer of the punched negative electrode side member, and uniaxial pressing was performed. Second, the negative electrode side member and the positive electrode side member were overlapped with the solid electrolyte layers facing each other, and current extraction electrodes were installed on the positive electrode and the negative electrode. Then, it was sealed in an aluminum laminate using a vacuum laminator and constrained with a pressure of 5 MPa. Thus, an evaluation battery (all-solid battery) was fabricated.

[0126] [Examples 2 to 7 and Comparative Examples 1 to 5]

[0127] In the production of the composite particles, the solid content fraction of the slurry was changed to produce composite particles having the ratio of the second part shown in Table 1. Except for using these composite particles to produce the negative electrode, an evaluation battery was produced in the same manner as in Example 1.

[0128] [Evaluation]

[0129] (Measurement of aspect ratio)

[0130] For the produced evaluation batteries, SEM observation was performed to obtain cross-sectional SEM images of the negative electrode active material layer. By using the above method, the aspect ratio of the composite particles in the negative electrode active material layer was calculated from the cross-sectional SEM images. The results are shown in Table 1.

[0131] (Measurement of battery resistance)

[0132] The voltage of each produced evaluation battery was adjusted to 3.7 V. Then, it was discharged at 5C, and the resistance value was calculated based on the voltage drop amount 5 seconds after the start of discharge. The resistance value of Comparative Example 1 was set to 100%, and the evaluation was performed relatively. The results are shown in Table 1. In addition, the relationship between the battery resistance and the ratio of the second part is shown in Figure 6 (a), and the relationship between the battery resistance and the aspect ratio is shown in Figure 6 (b).

[0133]

Table 1

[0134]

[0135] As shown in Table 1 and Figure 6 it can be confirmed that in the electrode layer produced using composite particles having a ratio of the second part of 55% or less, the aspect ratio of the composite particles becomes 3.6 or less. In addition, in the battery using this electrode layer, it was confirmed that the battery resistance was significantly suppressed.

Claims

1. Composite particles, comprising: a plurality of active materials containing Si element or Sn element, and a binder, when observing a cross-section of the composite particles, the composite particles have 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 particles 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 particles according to claim 1, wherein, The active material contains the Si element and has a silicon inclusion type crystal phase.

5. An electrode composite material containing the composite particles according to any one of claims 1 to 4.

6. An electrode layer, which is an electrode layer containing composite particles, the composite particles comprising: 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.

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 additive 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, the negative electrode active material layer being 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 method for manufacturing an electrode layer, comprising: a preparation step of preparing an electrode composite material containing the composite particles according to any one of claims 1 to 4; a precursor layer formation step of forming a precursor layer using the electrode composite material; and an electrode layer formation step of applying a pressing pressure to the precursor layer to form an electrode layer, Among them, in the electrode layer formation step, the pressing pressure is applied in such a manner that 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 becomes 3.6 or less.

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

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