Composite particles, electrode mixture, secondary battery, and method for manufacturing electrode mixture

Abstract

To provide composite particles that can be used to manufacture dry electrodes with excellent load characteristics. [Solution] The solution comprises multiple electrode active material particles and a binder. The plurality of electrode active material particles include large electrode active material particles with a relatively large average particle size and small electrode active material particles with a relatively small average particle size. The binder is a thermoplastic elastomer, A composite particle in which at least one of the plurality of electrode active material particles is in contact with the binder.

Description

[Technical Field]

[0001] This disclosure relates to composite particles, an electrode mixture containing said composite particles, a secondary battery, and a method for manufacturing the electrode mixture. [Background technology]

[0002] Rechargeable batteries can be repeatedly charged and discharged and are used in a variety of applications. For example, rechargeable batteries are used in mobile devices such as cell phones, smartphones, and laptop computers.

[0003] As a secondary battery, one can be used in which an electrode assembly containing a positive electrode, a negative electrode, and a separator between them is housed in an outer casing, and an electrolyte is injected into it. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent application 2022-515497 publication [Overview of the project] [Problems that the invention aims to solve]

[0005] Patent Document 1 discloses a particulate material used in electrodes, which consists of composite particles in which porous particles form a framework and an electroactive material is arranged within the pores of the porous particles. In the manufacture of electrodes using such composite particles, a slurry is formed by dispersing the composite particles in a solvent.

[0006] In the above manufacturing method, after applying the slurry onto the current collector, a step of removing the solvent in the slurry is required. In order to omit this solvent removal step and enable more efficient manufacturing of electrodes, dry electrodes manufactured by a so-called dry process that do not require a solvent in electrode manufacturing have attracted attention. However, in dry electrodes, since the electrodes are formed without using a solvent, a large amount of binder is used, which may reduce the load characteristics of the electrodes.

[0007] This disclosure has been made in view of such problems. That is, the main object of this disclosure is to provide composite particles capable of manufacturing dry electrodes with excellent load characteristics, an electrode composite material containing the composite particles, a manufacturing method thereof, and a secondary battery containing the composite particles.

Means for Solving the Problems

[0008] In order to achieve the above object, the composite particles according to an embodiment of this disclosure include a plurality of electrode active material particles and a binder. The plurality of electrode active material particles include electrode active material large particles having a relatively large average particle diameter and electrode active material small particles having a relatively small average particle diameter. The binder is a thermoplastic elastomer. At least one of the plurality of electrode active material particles is in contact with the binder.

[0009] Also, an electrode composite material according to an embodiment of this disclosure is a compression molded body of the above composite particles.

[0010] Also, a secondary battery according to an embodiment of this disclosure includes a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode contains the above composite particles.

[0011] Also, a manufacturing method of an electrode composite material according to an embodiment of this disclosure includes mixing a plurality of electrode active material particles and a binder to form composite particles, and pressing the composite particles to form a compression molded body. Includes, The plurality of electrode active material particles include large electrode active material particles with a relatively large average particle size and small electrode active material particles with a relatively small average particle size. The binder is a thermoplastic elastomer, In the composite particle, at least one of the plurality of electrode active material particles is in contact with the binder. [Effects of the Invention]

[0012] By using the composite particles of this disclosure in an electrode mixture, an electrode mixture and a secondary battery with superior load characteristics are provided as a dry electrode. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic external perspective view of a secondary battery according to one embodiment of the present disclosure. [Figure 2A] Figure 2A is a schematic cross-sectional view of an electrode assembly according to one embodiment of the present disclosure. [Figure 2B] Figure 2B is a schematic cross-sectional view of an electrode assembly according to one embodiment of the present disclosure. [Figure 3] Figure 3 is a schematic diagram of a composite particle according to one embodiment of the present disclosure. [Figure 4] Figure 4 is a schematic cross-sectional view showing the AA cross-section of the composite particle shown in Figure 3. [Figure 5] Figure 5 is a schematic diagram of a composite particle according to one embodiment of the present disclosure. [Figure 6] Figure 6 is a schematic cross-sectional view showing the BB cross-section of the composite particles shown in Figure 5. [Figure 7] Figure 7 is an SEM image of a composite particle according to one embodiment of the present disclosure, taken at a magnification of 2000x. [Figure 8] Figure 8 is an SEM image of a composite particle according to one embodiment of this disclosure, taken at a magnification of 800x. [Figure 9] Figure 9 is a schematic enlarged cross-sectional view showing a cross-section of an electrode composite obtained by powder rolling of the composite particles of this disclosure. [Figure 10] Figure 10 is a schematic cross-sectional view of an electrode component layer including an electrode composite 110 formed by powder rolling of the composite particles of the present disclosure, a current collector 130, and a separator 3. [Figure 11] Figure 11 is a graph showing the evaluation results of the reaction capacity of the cells in the examples and comparative examples. [Modes for carrying out the invention]

[0014] The embodiments of this disclosure will be described in detail below. While the explanation will be given with reference to the drawings as necessary, the illustrations are provided for illustrative purposes only to help understand this disclosure, and the appearance and dimensional ratios may differ from those of the actual product.

[0015] The applicant provides the following descriptions and examples to enable those skilled in the art to fully understand the disclosure, and it should be noted that these are not intended to limit the subject matter described in the claims. In other words, the disclosure is not particularly limited to the preferred embodiments described below, and can be modified and implemented as appropriate within the scope of its purpose. For the sake of convenience, such as explaining the main points or making it easier to understand, the descriptions may be divided into embodiments and examples, but partial substitution and / or combination of configurations shown in different embodiments is possible. In descriptions of such embodiments, redundant explanations of substantially identical matters may be omitted, and only the differences may be described. In particular, similar effects of similar configurations may not be mentioned sequentially in each embodiment.

[0016] Furthermore, any references to direction or orientation in the description of this specification are merely for explanatory convenience and are not intended to limit the scope of this disclosure unless explicitly stated otherwise. For example, relative terms such as "outside (or outside, external, or outer perimeter)" and "inside (or inside, internal, or inner perimeter)," as well as their derived terms, should be understood to refer to the direction as described or illustrated. Similarly, "on top of" an element includes not only cases where it is in contact with the upper surface of the element, but also cases where it is not in contact with the upper surface of the element. That is, "on top of" an element includes not only positions above the element at a distance, i.e., positions above the element via other objects or at a distance above it, but also positions directly above the element in contact with it. Moreover, "on top" does not necessarily mean the upper side in the vertical direction. "On top" merely indicates the relative positional relationship of an element. In other words, unless explicitly stated otherwise, the invention is not required to be limited to a specific direction, orientation, form, etc. Furthermore, terms such as "provided," "positioned," "connected," and "attached," as well as their derived terms, are also included, unless otherwise explicitly stated, and may refer to direct actions or actions involving other elements.

[0017] The composite particles of this disclosure, and the electrode composite materials produced using said composite particles, can be used in secondary batteries. To facilitate understanding of this disclosure, the basic overall structure of a secondary battery will be described below.

[0018] [Basic configuration of a secondary battery] In this specification, the term "secondary battery" is not overly restrictive in its name, and may also include, for example, "energy storage devices."

[0019] The secondary battery according to this disclosure comprises an electrode assembly composed of electrode constituent layers including a positive electrode, a negative electrode, and a separator. The secondary battery according to this disclosure may have a laminated structure in which such electrode constituent layers are stacked, or a wound structure in which the electrode constituent layers are wound in a roll shape (hereinafter also referred to as a "wound electrode body" or "wound structure"). Figure 1 schematically shows an exemplary external appearance of the secondary battery 500, and Figures 2A and 2B schematically show exemplary internal structures thereof. As shown in the figures, the electrode assembly 100A or 100B is housed inside the outer casing 60. In the exemplary embodiments shown in Figures 2A and 2B, the electrode assembly 100A or 100B has a configuration in which electrode constituent layers 5 including a positive electrode 1, a negative electrode 2, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2 are stacked (Figure 2A) and a configuration in which they are wound (Figure 2B). In the secondary battery 500, such electrode assemblies 100A or 100B are sealed in an outer casing 60 together with an electrolyte (e.g., a non-aqueous electrolyte). The structure of the electrode assembly is not necessarily limited to a laminated or wound structure. For example, the electrode assembly may have a so-called stack-and-fold structure in which a positive electrode 1, a negative electrode 2, and a separator 3 are laminated on a long film and then folded.

[0020] Positive electrode 1 may consist of at least a positive electrode composite material and a positive electrode current collector. In positive electrode 1, the positive electrode composite material may be provided on at least one side of the positive electrode current collector. The positive electrode composite material contains a positive electrode active material as an electrode active material. For example, multiple positive electrodes 1 in an electrode assembly may each have the positive electrode composite material provided on both sides of the positive electrode current collector, or the positive electrode composite material may be provided on only one side of the positive electrode current collector.

[0021] The thickness of the positive electrode material layer is not particularly limited, but may be between 1 μm and 300 μm, for example, between 5 μm and 200 μm. The thickness of the positive electrode material layer is the thickness inside the secondary battery, and the average value of measurements taken at any 10 locations may be used.

[0022] The negative electrode 2 may consist of at least a negative electrode composite material and a negative electrode current collector. The negative electrode 2 may have the negative electrode composite material provided on at least one side of the negative electrode current collector. The negative electrode composite material contains a negative electrode active material as an electrode active material. For example, each of the multiple negative electrodes in the electrode assembly may have a negative electrode material layer provided on both sides of the negative electrode current collector, or it may have the negative electrode composite material provided on only one side of the negative electrode current collector.

[0023] The thickness of the negative electrode material layer is not particularly limited, but may be between 1 μm and 300 μm, for example, between 5 μm and 200 μm. The thickness of the negative electrode material layer is the thickness inside the secondary battery, and the average value of measurements taken at any 10 locations may be used.

[0024] The positive electrode current collector and negative electrode current collector used in positive electrode 1 and negative electrode 2 are components that contribute to collecting and supplying electrons generated in the electrode active material due to the battery reaction. Such electrode current collectors may be sheet-shaped metal members. Furthermore, the electrode current collectors may be single-layered or multi-layered. Moreover, the electrode current collectors may have a porous or perforated form. For example, the current collector may be metal foil, perforated metal, mesh, or expanded metal. The positive electrode current collector used in positive electrode 1 may consist of metal foil containing at least one selected from the group consisting of aluminum, nickel, and stainless steel, for example. On the other hand, the negative electrode current collector used in negative electrode 2 may consist of metal foil containing at least one selected from the group consisting of copper, aluminum, nickel, and stainless steel, for example.

[0025] The separator 3, located between the positive electrode 1 and the negative electrode 2, is a component provided to prevent short circuits caused by contact between the positive and negative electrodes and to maintain the electrolyte. In other words, the separator 3 is a component that isolates the positive electrode 1 and the negative electrode 2, prevents short circuits of current caused by contact between the two electrodes, and allows ions (e.g., lithium ions) to pass through. For example, the separator 3 may be a porous or microporous insulating material, and may have a film form due to its small thickness.

[0026] The separator 3 may be one or more types of porous membranes, such as synthetic resins and / or ceramics, or it may be a laminated film of two or more types of porous membranes. Examples of synthetic resins used for the separator 3 include polytetrafluoroethylene, polypropylene, and polyethylene. For example, the separator 3 may include a porous membrane (base layer) and a polymer compound layer provided on one or both sides of the base layer. For example, if the electrode assembly 100B is a wound body as shown in Figure 2, the adhesion of the separator 3 to the positive electrode 1 and the adhesion of the separator 3 to the negative electrode 2 may be improved, making it easier to suppress distortion of the wound body. The polymer compound layer may include one or more types of polymer compounds, such as polyvinylidene fluoride. These materials have excellent physical strength and tend to be electrochemically stable. The polymer compound layer may also include one or more types of insulating particles, such as inorganic particles. The type of inorganic particles may be, for example, aluminum oxide and / or aluminum nitride. The separator 3 in this disclosure should not be particularly limited by its name, and may also be a solid electrolyte, a gel electrolyte, and / or insulating inorganic particles having similar functions.

[0027] The thickness of separator 3 is not particularly limited, but may be between 1 μm and 100 μm, for example, between 2 μm and 20 μm. The thickness of separator 3 is the thickness inside the secondary battery (especially the thickness between the positive and negative electrodes), and the average value of measurements taken at any 10 locations may be used.

[0028] In the secondary battery of this disclosure, an electrode assembly consisting of an electrode constituent layer 5 including a positive electrode 1, a negative electrode 2, and a separator 3 may be sealed in an outer casing together with an electrolyte. The electrolyte in the secondary battery of this disclosure may be a so-called "non-aqueous" electrolyte. The electrolyte will contain metal ions released from the electrodes (positive electrode and / or negative electrode), and therefore the electrolyte can assist in the movement of metal ions in the battery reaction. The electrolyte may be in liquid or gel form.

[0029] Typically, the electrolyte comprises a solvent and an electrolyte salt. The electrolyte may further contain one or more other materials, such as additives. In one preferred embodiment, the separator 3 is impregnated with the electrolyte, and the positive electrode 1 and / or negative electrode 2 may also be impregnated with the electrolyte.

[0030] The solvent may contain one or more non-aqueous solvents, such as organic solvents. Electrolytes containing non-aqueous solvents can be so-called non-aqueous electrolytes. Examples of non-aqueous solvents include cyclic carbonate esters, linear carbonate esters, lactones, linear carboxylic acid esters, and / or nitriles (e.g., mononitriles). Using these materials can make it easier to obtain better battery capacity, cycle characteristics, and / or storage characteristics.

[0031] Cyclic carbonate esters may include, for example, ethylene carbonate, propylene carbonate, and / or butylene carbonate. Chain-like carbonate esters may include, for example, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and / or methylpropyl carbonate. Lactones may include, for example, γ-butyrolactone and / or γ-valerolactone. Chain-like carboxylic acid esters may include, for example, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and / or ethyl trimethylacetate. Nitriles may include, for example, acetonitrile, methoxyacetonitrile, and / or 3-methoxypropionitrile.

[0032] In addition, non-aqueous solvents may include, for example, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate and / or dimethyl sulfoxide. Among these, it is preferable that the non-aqueous solvent contains one or more of the following: ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate. This is because it is easier to obtain higher battery capacity, better cycle characteristics and / or better storage characteristics.

[0033] Furthermore, the non-aqueous solvent may be, for example, an unsaturated cyclic carbonate ester, a halogenated carbonate ester, a sulfonic acid ester, an acid anhydride, a dicyano compound (dinitrile compound), a diisocyanate compound, a phosphate ester, and / or a chain compound having a triple bond between carbon atoms. This is because it easily improves the chemical stability of the electrolyte. Here, "unsaturated cyclic carbonate ester" refers to a cyclic carbonate ester having one or more unsaturated bonds (double or triple bonds between carbon atoms). Examples of such unsaturated cyclic carbonate esters include vinylene carbonate, vinylethylene carbonate, and / or methyleneethylene carbonate. "Halogenated carbonate ester" refers to a cyclic or chain carbonate ester containing one or more halogen elements as constituent elements. When a halogenated carbonate ester contains two or more halogens as constituent elements, the types of those two or more halogens may be just one type or two or more types. Examples of cyclic halogenated carbonate esters include 4-fluoro-1,3-dioxolan-2-one and / or 4,5-difluoro-1,3-dioxolan-2-one. Examples of linear halogenated carbonate esters may be fluoromethylmethyl carbonate, bis(fluoromethyl) carbonate and / or difluoromethylmethyl carbonate. Examples of sulfonic acid esters may be monosulfonic acid esters and / or disulfonic acid esters. Monosulfonic acid esters may be cyclic monosulfonic acid esters or linear monosulfonic acid esters. Examples of cyclic monosulfonic acid esters may be sultones such as 1,3-propanesultone and / or 1,3-propensultone. Examples of linear monosulfonic acid esters are compounds obtained by cleaving a cyclic monosulfonic acid ester. Disulfonic acid esters may be cyclic disulfonic acid esters or linear disulfonic acid esters. The acid anhydride may be, for example, a carboxylic acid anhydride, a disulfonic acid anhydride, and / or a carboxylic acid sulfonic acid anhydride. The carboxylic acid anhydride may be, for example, succinic anhydride, glutaric acid anhydride, and / or maleic anhydride.Disulfonic anhydrides may be, for example, ethanedisulfonic anhydride and / or propanedisulfonic anhydride. Carboxylic acid sulfonic anhydrides may be, for example, sulfobenzoic anhydride, sulfopropionic anhydride and / or sulfobutyric anhydride. Dinitrile compounds are, for example, compounds represented by NC-R1-CN (where R1 is either an alkylene group or an arylene group). These dinitrile compounds may be, for example, succinonitrile (NC-C2H4-CN), glutalonitrile (NC-C3H6-CN), adiponitrile (NC-C4H8-CN), and phthalonitrile (NC-C6H4-CN). Diisocyanate compounds are, for example, compounds represented by OCN-R2-NCO (where R2 is either an alkylene group or an arylene group). These diisocyanate compounds may be, for example, hexamethylene diisocyanate (OCN-C6H4-CN). 12 It may be -NCO), etc. Phosphate esters may be, for example, trimethyl phosphate and triethyl phosphate. A chain compound having a carbon-carbon triple bond is a chain compound having one or more carbon-carbon triple bonds (-C≡C-). This chain compound having a carbon-carbon triple bond may be, for example, propargylmethyl carbonate (CH≡C-CH2-OC(=O)-O-CH3) and propargyl methylsulfonic acid (CH≡C-CH2-OS(=O)2-CH3).

[0034] The electrolyte salts contained in the electrolyte may include one or more types of salts, such as lithium salts. The electrolyte salts may also include salts other than lithium salts. Such non-lithium salts may be salts of light metals other than lithium, for example. Examples of lithium salts include lithium hexafluoride phosphate (LiPF6), lithium tetraborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoride arsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), dilithium hexafluorosilicate (Li2SiF6), lithium chloride (LiCl), and / or lithium bromide (LiBr). This is because it is easier to obtain better battery capacity, cycle characteristics, and / or storage characteristics. Among these, it may be one or more of lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoride arsenate.

[0035] As used herein, “outer casing 60” means a member for housing or enclosing an electrode assembly, which is formed by winding or laminating electrode constituent layers including a positive electrode, a negative electrode, and a separator. For example, the outer casing 60 may be an outer casing having a laminated structure or a metal outer casing having a non-laminated structure. In this specification, “metal outer casing having a non-laminated structure” means that the outer casing 60 is not a laminated member such as one consisting of a metal sheet / fusion layer / protective layer. In other words, the outer casing 60 in this disclosure may differ from the outer casing 60 of a soft-case type battery, which corresponds to a pouch made of so-called laminated film. Preferably, the metal outer casing having a non-laminated structure has a structure consisting of a single metal member. For example, such a metal outer casing may be a single metal member consisting of stainless steel (SUS) and / or aluminum. Here, “single metal member” means, in a broad sense, that the outer casing 60 does not have a so-called laminated structure, and in a narrow sense, that the outer casing 60 is a member consisting substantially only of metal. Therefore, if the component consists substantially of only metal, the surface of the metal casing may be subjected to an appropriate surface treatment. For example, in the cross-section obtained by cutting such a metal casing in the thickness direction, a single metal layer can be observed, excluding the parts that have been surface-treated. In this specification, "stainless steel" refers to stainless steel as defined in, for example, "JIS G 0203 Steel Terminology," and may be an alloy steel containing chromium or chromium and nickel. In a preferred embodiment, the casing may have a can shape (in such a case, the casing 60 may also be referred to as the "casing can" in this specification).

[0036] The outer casing 60 may be composed of two or more parts. For example, the outer casing 60 may consist of two or more components such as a main body 61 and a lid 62 (see Figure 1). For example, if the outer casing 60 consists of a main body 61 and a lid 62, after housing the electrode assembly, electrolyte, and optionally the electrode terminals, the main body 61 and the lid 62 are combined to seal the outer casing 60. The sealing method is not particularly limited and may be sealed by welding, for example.

[0037] Any material that can be used to construct a hard-case type casing in the field of secondary batteries can be used as the material constituting the main body 61 and the lid 62 of the casing 60. Such material may be a conductive material that can achieve electron transfer, or an insulating material that cannot achieve electron transfer.

[0038] From the viewpoint of electrode extraction, the material of the outer casing 60 is preferably a conductive material. That is, the outer casing 60 preferably includes two components: a positive electrode conductive part and a negative electrode conductive part. Here, the main body and lid of the outer casing 60 may each constitute either the positive electrode conductive part or the negative electrode conductive part, respectively.

[0039] As the conductive material, at least one conductive material selected from the group consisting of, for example, silver, gold, copper, iron, tin, platinum, aluminum, nickel, and stainless steel may be used. As the insulating material, at least one insulating polymer material selected from, for example, polyester (e.g., polyethylene terephthalate), polyimide, polyamide, polyamide-imide, and polyolefin (e.g., polyethylene, polypropylene) may be used.

[0040] The dimensions of the main body 61 and lid 62 of the outer casing 60 are primarily determined according to the dimensions of the electrode assembly. For example, it is preferable that the dimensions are such that the movement of the electrode assembly within the outer casing 60 is prevented when the electrode assembly is housed there. By preventing the movement of the electrode assembly, damage to the electrode assembly due to impact or the like can be prevented, thereby improving the safety of the secondary battery.

[0041] The outer casing 60 may be a flexible case such as a pouch made of laminate film. The laminate film may have a configuration in which at least a metal layer (e.g., aluminum) and an adhesive layer (e.g., polypropylene and / or polyethylene) are laminated, and an additional protective layer (e.g., nylon and / or polyamide) may be laminated.

[0042] The secondary battery may be provided with electrode terminals 81. Such electrode terminals 81 may be provided on at least one surface of the casing 60. For example, positive and negative electrode terminals may be provided on different surfaces of the casing 60, respectively. From the viewpoint of electrode extraction, it is preferable that the positive and negative electrode terminals are provided on opposing surfaces of the casing 60.

[0043] The electrode terminals are preferably made of a material with high conductivity. While there are no particular limitations on the material of the electrode terminals, at least one material can be selected from the group consisting of silver, gold, copper, iron, tin, platinum, aluminum, nickel, and stainless steel.

[0044] [Features of this disclosure] This disclosure relates to composite particles capable of forming electrode mixtures contained in secondary batteries, electrode mixtures manufactured using said composite particles, and secondary batteries equipped with said electrode mixtures. Based on the basic configuration of the secondary battery described above, the composite particles and electrode mixtures manufactured using said composite particles will be described in this disclosure.

[0045] Figure 3 is a schematic diagram showing the composite particle 10 of this disclosure. Figure 4 is a schematic cross-sectional view showing the AA cross-section of the composite particle shown in Figure 3. The composite particle 10 includes a plurality of electrode active material particles 11 and a binder 16. The plurality of electrode active material particles 11 include electrode active material particles having different average particle sizes. Specifically, the plurality of electrode active material particles may include large electrode active material particles 12 with relatively large average particle sizes and small electrode active material particles 14 with relatively small average particle sizes. By including a plurality of electrode active material particles 11 with different average particle sizes, the small electrode active material particles 14 can be arranged between the plurality of large electrode active material particles 12 in the composite particle 10. This makes it possible to reduce the distance between the electrode active material particles 11. By reducing the distance between the electrode active material particles, the amount of binder 16 positioned between the electrode active material particles 11 can be reduced. In general, the binder content in an electrode mixture affects the load characteristics of the electrode mixture. The lower the binder content, the better the load characteristics of the electrode mixture can be obtained. As a result, using the composite particles 10, it becomes possible to produce an electrode composite material with a low binder content and excellent load characteristics.

[0046] The binder 16 is positioned to contact at least one of the multiple electrode active material particles. That is, at least some of the large electrode active material particles 12 and small electrode active material particles 14 contained in the composite particle 10 are in contact with the binder 16. The binder 16 may adhere the electrode active material particles that are in contact with the binder 16 by coming into contact with at least one of the electrode active material particles 11. In other words, at least one of the multiple electrode active material particles 11 may be adhered to each other via the binder 16. In such a structure, the binder 16 contributes to the formation of the composite particle 10 by adhering the multiple electrode active material particles 11 to each other. That is, the binder 16 can play a role in stably maintaining the structure of the composite particle 10 containing the multiple electrode active material particles 11.

[0047] The inventors of this application have newly discovered that using a thermoplastic elastomer as a binder 16 in a composite particle 10 comprising large electrode active material particles 12 and small electrode active material particles 14 is particularly useful. Specifically, it has been found that the composite particle 10 of this disclosure, which includes a binder 16 of a thermoplastic elastomer having flexibility and elasticity, is suitable for forming electrode composites by a dry process. In other words, with the composite particle 10 of this disclosure, it is not necessary to disperse the composite particle 10 in an organic solvent to form a slurry, and an electrode composite can be obtained as a dry electrode by powder rolling the composite particle 10. In other words, with the composite particle 10 of this disclosure, a pressurized molded body obtained by powder rolling the composite particle 10 can be used as an electrode composite. Such an electrode composite is a molded body obtained by pressurizing the composite particle 10, and is distinguished from an electrode composite formed by slurry formation through the addition of a solvent. The electrode composite obtained by powder rolling of the composite particles 10 may also be referred to as, for example, a pressure-molded body, a compacted powder-molded body, a rolled body, a compression-molded body, or a powder-compressed body.

[0048] Although not bound by any particular theory, according to the composite particles 10 of this disclosure, the inclusion of a thermoplastic elastomer as a binder 16 allows the binder 16 to suitably penetrate between multiple composite particles 10 during powder rolling, thus binding the electrode active material particles contained in different composite particles 10 together. Through such binding, an electrode composite material with a stable structure can be obtained by powder rolling multiple composite particles 10. In other words, the binder 16 can suitably contribute not only to the stabilization of the structure of the composite particles 10 but also to the stabilization of the structure of the electrode composite material as a dry electrode. Therefore, according to the composite particles 10 of this disclosure, an electrode composite material can be formed by a dry process. This eliminates the need for the slurry formation step of the composite particles 10 and the drying step to remove the solvent used for slurry formation when manufacturing the electrode composite material. Consequently, according to the composite particles 10 of this disclosure, an electrode composite material can be formed more efficiently.

[0049] The inventors of this application have found that a dry electrode obtained using the composite particles 10 of this disclosure has superior load characteristics compared to an electrode obtained through a slurry formation process (hereinafter also referred to as a wet electrode). Specifically, a secondary battery comprising an electrode composite obtained by powder rolling of the composite particles 10 of this disclosure may be preferable to a wet electrode in terms of capacity retention rate and capacity.

[0050] Generally, in wet electrodes obtained via slurry formation, the binder is dispersed in the solvent, so after the subsequent removal of the solvent, the binder can be uniformly positioned on the surface 122 of the electrode active material particles. On the other hand, according to the composite particles 10 of this disclosure, an electrode mixture can be formed by powder rolling. As a result, in the resulting electrode mixture, the binder 16 located between the electrode active material particles 11 may partially penetrate into the gaps between the electrode active material particles 11 and be positioned unevenly or locally on the electrode active material particles 11. Therefore, compared to the case of wet electrodes, the contact area between the electrode active material particles 11 and the binder 16 in the electrode mixture may be smaller. This means that in the electrode mixture as a dry electrode obtained using the composite particles 10 of this disclosure, the exposed area of ​​the electrode active material particles 11 is larger. This increases the contact area between the electrolyte and the electrode active material particles 11, and the electrochemical reaction resistance in the electrode mixture can be reduced. In addition, the charge and discharge rate can be improved by improving the ion transfer resistance (i.e., improving the ion path to the electrode active material particles 11).

[0051] Furthermore, although not bound by any particular theory, one further reason why excellent loading characteristics can be provided is presumed to be the small amount of binder 16 contained in the composite particles 10. This effect may be related to the fact that the composite particles 10 of this disclosure contain electrode active material particles of different sizes and a thermoplastic elastomer binder. Specifically, because the composite particles 10 of this disclosure contain large electrode active material particles 12 and small electrode active material particles 14, the small electrode active material particles 14 are arranged between multiple large electrode active material particles 12, reducing the distance between the electrode active material particles. In addition, by using a thermoplastic elastomer as the binder 16, it becomes possible to suitably insert the binder 16 into the gaps between the electrode active material particles 11 by powder rolling. As a result, the electrode active material particles 11 can be bound together with a small amount of binder 16, reducing the binder 16 content ratio in the electrode composite and potentially obtaining an electrode composite with excellent loading characteristics.

[0052] The binder 16 may be in contact with two or more electrode active material large particles 12, binding the electrode active material large particles 12 together. For example, as shown in Figures 3 and 4, the binder 16 may be positioned between a plurality of electrode active material particles 11 and on the surface 122 of the electrode active material particles 11 so as to cover at least a portion of the composite particle 10. The binder 16 may be arranged in a mesh-like pattern inside or on the surface of the composite particle 10. In such a structure, the binder 16 and the electrode active material particles 11 may be in surface contact, line contact, and / or point contact. Preferably, the binder 16 may be in line contact and / or point contact with the electrode active material particles 11. That is, the binder 16 and the electrode active material particles 11 may be in contact in local areas of the electrode active material particles 11. The electrode active material particles 11 may have a contact area with the binder 16 and a non-contact area that does not come into contact with the binder 16. The contact region may be a linear or point-like local region. In such a structure, the electrode active material particles 11 may be in contact with the binder 16 only in the local region. This reduces the binder 16 content in the composite particles 10. Therefore, an electrode composite material with a lower binder 16 content and superior load characteristics can be obtained.

[0053] Examples of thermoplastic elastomers used in binder 16 include styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), butylene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butylene rubber (SBR), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), and hydrogenated styrene-butylene rubber (HSBR).

[0054] Generally, compounds belonging to the group of perfluoroalkyl compounds and polyfluoroalkyl compounds (PFAS), such as polyvinylidene fluoride (PVdF), are known as binders for forming dry electrodes. However, some of these compounds are restricted substances under the European REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) regulation due to concerns about environmental impact and health hazards. The composite particles 10 of this disclosure make it possible to suitably form dry electrodes without using such restricted substances.

[0055] If oxidation resistance of the electrode composite material is important, the binder 16 may be a polymer obtained by hydrogenating (also called "hydrogenation" or "hydrogenation") at least a portion of the C=C double bonds of a diene-based elastomer. By using such a material as the binder 16, in addition to obtaining an electrode composite material suitable for dry electrodes, the oxidation resistance of the electrode composite material can be improved. Therefore, an electrode composite material that can be suitably used as a cathode composite material can be obtained. In other words, with the composite particles 10 of this disclosure, a cathode composite material suitable for dry electrodes can be obtained. For example, the binder 16 may be at least one selected from the group consisting of HSBR obtained by hydrogenating styrene-butadiene rubber, HNBR obtained by hydrogenating acrylonitrile-butadiene rubber, HBR obtained by hydrogenating polybutadiene, and SEBS obtained by hydrogenating styrene-butadiene-styrene block copolymer.

[0056] If further emphasis is placed on the oxidation resistance of the electrode mixture, the binder 16 may be a hydrogenated polymer elastomer. In this specification, "hydrogenated polymer elastomer" means an elastomer with a hydrogenation rate of 80% or more and 100% or less. When the hydrogenation rate is within the above range, composite particles capable of forming an electrode mixture with excellent oxidation resistance can be obtained. For example, the hydrogenation rate of HNBR used as binder 16 may be 80% or more and 100% or less. In addition, the amount of acrylonitrile bound to the HNBR is not particularly limited, but may be, for example, 5% or more and 50% or less. By using such HNBR, an electrode mixture with excellent oxidation resistance that can be suitably used as a cathode mixture can be obtained.

[0057] The material of the binder 16 can be measured, for example, by the following method. First, a mass spectrum is obtained by mass spectrometry using a mass spectrometer to analyze the pyrolysis products obtained by heating the composite particles 10 or electrode mixture. By analyzing the obtained mass spectrum, the molecular weight and elemental composition of the binder 16 can be determined, and the type of material can be estimated by comparing it with a standard spectrum. Next, the composite particles 10 or electrode mixture are subjected to nuclear magnetic resonance spectroscopy (NMR) to obtain an NMR spectrum. 1 A 1H-NMR spectrum was obtained. More specifically, the composite particles, or electrode mixture cut into approximately 10 mg pieces, were dissolved in a solvent (deuterated chloroform (CDCl3)) to a concentration of approximately 1 wt%, packed into a sample tube, and then subjected to measurement. These operations were performed in a dry room atmosphere. The hydrogenation rate can be determined from the ratio of the integral value of the peak of the double bond of butadiene to the integral value of the peak of the single bond where butadiene is hydrogenated in the obtained NMR spectrum. For example, if the ratio of the integral value of the double bond of butadiene to the integral value of the single bond where butadiene is hydrogenated is in the range of 0:100 to 20:80, the measured binder 16 can be determined to be a hydrogenated polymer elastomer with a hydrogenation rate of 80% or more.

[0058] The composite particle 10 may include a plurality of large electrode active material particles 12 and a plurality of small electrode active material particles 14. That is, the composite particle 10 may include a plurality of large electrode active material particles 12, a plurality of small electrode active material particles 14, and a binder 16. As shown in Figure 4, at least one of the plurality of small electrode active material particles 14 may be located between the plurality of large electrode active material particles 12. The plurality of large electrode active material particles 12 may be adjacent to each other with at least one of the small electrode active material particles 14 in between. With this arrangement, the small electrode active material particles 14 are positioned in the gaps between the plurality of large electrode active material particles 12, so the distance between the electrode active material particles can be reduced.

[0059] Furthermore, with this arrangement, small electrode active material particles 14 can be held between large electrode active material particles 12. In other words, multiple large electrode active material particles 12 may form gaps capable of holding the small electrode active material particles 14. The binder 16 may be positioned mainly on the inner surface of the composite particle 10 so as to bind multiple electrode active material particles 11 together as a single composite particle. Also, electrode active material particles that do not come into contact with the binder 16 may be located inside the composite particle 10. For example, the composite particle 10 may contain multiple adjacent small electrode active material particles 14A without the binder 16 in between. Therefore, the small electrode active material particles 14 may be held within the composite particle 10 not only by binding with the binder 16, but also by the arrangement of the large electrode active material particles 12. With this structure, it is possible to reduce the amount of binder 16 contained in the composite particle 10.

[0060] Figure 9 is a schematic enlarged cross-sectional view showing a cross-section of an electrode composite obtained by powder rolling of the composite particles of this disclosure. According to this disclosure, as shown in Figure 9, even in an electrode composite formed by powder rolling of the composite particles 10 as described above, there may be electrode active material particles that do not come into contact with the binder 16. This improves the ion path in the electrode composite, making it possible to form an electrode composite with superior ionic conductivity.

[0061] As shown in Figure 4, at least one of the electrode active material small particles 14 located between the multiple electrode active material large particles 12 does not need to be in contact with the binder 16. In other words, the composite particle 10 may include electrode active material small particles 14A located between the multiple electrode active material large particles 12 and not in contact with the binder 16. The electrode active material small particles 14A may be held between the multiple electrode active material large particles 12. With this structure, the composite particle 10 can suitably hold the electrode active material small particles 14 even if the amount of binder 16 contained in the composite particle 10 is small.

[0062] The average particle size of the composite particles 10 may be, for example, 50 μm or less, and more preferably 30 μm or more and 40 μm or less. When the average particle size of the composite particles is within the above range, it becomes possible to form an electrode composite material with excellent structural stability by powder rolling.

[0063] In this specification, "average particle size of composite particle 10" corresponds to the mode diameter of composite particle 10. That is, the average particle size corresponds to the particle size at the peak (mode) in the cumulative curve (particle size distribution) where the total volume is 100% in the volume-based particle size distribution. The average particle size of composite particle 10 may be calculated from the particle size distribution obtained by a method using laser diffraction and scattering in accordance with ISO 13320 and JIS Z 8825-1. Specifically, in the obtained particle size distribution, the particle size at the peak top of the largest particle size within the range of 30 μm to 50 μm may be taken as the average particle size of composite particle 10.

[0064] The maximum particle size of the composite particles 10 may be 50 μm or less. The composite particles 10 may pass through a sieve with a mesh size of 50 μm, in accordance with the JIS 8801:2019 standard. By ensuring that the particle size of the composite particles is uniformly 50 μm or less, it becomes possible to form an electrode composite material with excellent structural stability by powder rolling.

[0065] The average particle size of the electrode active material small particles 14 contained in the composite particle 10 may be 5% to 30% or 5% to 20% of the average particle size of the electrode active material large particles 12. When the ratio of the average particle size of the electrode active material small particles 14 to the average particle size of the electrode active material large particles 12 is within the above range, at least one electrode active material small particle 14 is suitably arranged between a plurality of electrode active material large particles 12 in the composite particle 10 and the electrode composite material obtained by powder rolling the composite particle 10. This allows the structure to be suitably maintained with a small amount of binder 16. Therefore, with such a composite particle 10, an electrode composite material with excellent structural stability and load characteristics can be obtained by powder rolling.

[0066] The average particle sizes of the large electrode active material particles 12 and the small electrode active material particles 14 may be calculated from the particle size distribution obtained by a laser diffraction / scattering method in accordance with ISO 13320 and JIS Z 8825-1. The particle size distribution may have a multimodal distribution containing two or more peaks. Although not particularly limited, the following description will focus on the case where the average particle size of the large electrode active material particles 12 is 10 μm or more and 30 μm or less, and the average particle size of the small electrode active material particles 14 is 1 μm or more and less than 10 μm. In this case, the particle size at the peak top of the largest particle size peak within the range of 10 μm to 30 μm in the obtained particle size distribution may be taken as the average particle size of the large electrode active material particles 12. Also, the particle size at the peak top of the largest particle size peak within the range of 1 μm to less than 10 μm in the obtained particle size distribution may be taken as the average particle size of the small electrode active material particles 14. Furthermore, as long as the relative sizes of the average particle sizes are maintained, the average particle size of the large electrode active material particles 12 and the average particle size of the small electrode active material particles 14 are not constrained to the ranges described above.

[0067] The average particle size of the large electrode active material particles 12 may be 10 μm or more and 30 μm or less, and more preferably 15 μm or more and 25 μm or less. On the other hand, the average particle size of the small electrode active material particles 14 is smaller than the average particle size of the large electrode active material particles 12, and may be 1 μm or more and less than 10 μm, and more preferably 1 μm or more and 8 μm or less. When the average particle sizes of the large electrode active material particles 12 and the small electrode active material particles 14 are within the above ranges, multiple electrode active material particles can be suitably combined, and a composite particle 10 can be obtained in which the structure is maintained with a small amount of binder 16. Furthermore, by powder rolling such a composite particle 10, multiple electrode active material particles can be suitably held via the binder 16, and an electrode composite material with excellent load characteristics can be obtained.

[0068] The electrode active material particles contained in the composite particle 10 may be electrode active material contained in the positive electrode or the negative electrode. The composite particle 10 may contain positive electrode active material particles or negative electrode active material particles. Specifically, the composite particle 10 may contain large positive electrode active material particles and small positive electrode active material particles, or it may contain large negative electrode active material particles and small negative electrode active material particles. A positive electrode composite material can be obtained by powder rolling the composite particle 10 containing positive electrode active material particles. Alternatively, a negative electrode composite material can be obtained by powder rolling the composite particle 10 containing negative electrode active material particles.

[0069] The positive electrode active material and the negative electrode active material are substances that directly participate in electron transfer in a secondary battery and are the main materials of the positive and negative electrodes that carry out charging and discharging, i.e., battery reactions. More specifically, in a secondary battery, ions are brought into the electrolyte due to the "positive electrode active material contained in the positive electrode composite material" and the "negative electrode active material contained in the negative electrode composite material," and charging and discharging occur when these ions move between the positive and negative electrodes to transfer electrons. The positive electrode composite material and the negative electrode composite material may be layers that are particularly capable of intercalating and releasing lithium ions. In other words, a secondary battery equipped with an electrode composite material obtained by powder rolling of composite particles according to this disclosure may be a non-aqueous electrolyte secondary battery in which lithium ions move between the positive and negative electrodes via a non-aqueous electrolyte to charge and discharge the battery. When lithium ions are involved in charging and discharging, the secondary battery according to this disclosure corresponds to a so-called "lithium-ion battery" and has layers capable of intercalating and releasing lithium ions as the positive electrode and negative electrode.

[0070] In the context of lithium-ion batteries, the positive electrode active material particles may be materials that contribute to the intercalation and deintercalation of lithium ions. In other words, the composite particle 10 may contain one or more types of positive electrode active material particles capable of intercalating and deintercalating lithium. From this perspective, the positive electrode active material particles may be, for example, lithium-containing compounds. The type of lithium-containing compound is not particularly limited, but if emphasis is placed on easily obtaining a high energy density, examples include lithium-containing composite oxides and lithium-containing phosphate compounds.

[0071] The lithium-containing composite oxide is a general term for oxides containing lithium and one or more other elements (elements other than lithium) as constituent elements, and may have any crystal structure such as a layered rock salt type and a spinel type, for example. The lithium-containing phosphate compound is a general term for phosphate compounds containing lithium and one or more other elements as constituent elements, and may have a crystal structure such as an olivine type, for example. The type of the other element is not particularly limited as long as it is any one or more of arbitrary elements. Among them, the other element is preferably any one or more of the elements belonging to Groups 2 to 15 in the long-period type periodic table. Emphasizing that a high voltage is easily obtained, the other element may be, for example, nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and the like.

[0072] The lithium-containing composite oxide having a layered rock salt type crystal structure may be, for example, a compound represented by each of the following formulas (1) to (3). Li a Mn (1-b-c) Ni b M11 c O (2-d) F e ···(1) (In the formula, M11 is at least one of cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to e each satisfy 0.8 ≦ a ≦ 1.2, 0 < b < 0.5, 0 ≦ c ≦ 0.5, (b + c) < 1, -0.1 ≦ d ≦ 0.2, and 0 ≦ e ≦ 0.1. However, the composition of lithium varies depending on the charge-discharge state, and a is the value in the fully discharged state.) Li a Ni (1-b) M12 b O (2-c) F d ···(2) (In the formula, M12 is at least one of the following: cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to d satisfy the following conditions, respectively: 0.8 ≤ a ≤ 1.2, 0.005 ≤ b ≤ 0.5, -0.1 ≤ c ≤ 0.2, and 0 ≤ d ≤ 0.1. However, the composition of lithium varies depending on the charge / discharge state, and a is the value in the fully discharged state.) Li a Co (1-b) M13 b O (2-c) F d ...(3) (In the formula, M13 is at least one of nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to d satisfy 0.8 ≤ a ≤ 1.2, 0 ≤ b < 0.5, -0.1 ≤ c ≤ 0.2, and 0 ≤ d ≤ 0.1, respectively. However, the composition of lithium differs depending on the charge and discharge state, and a is the value in the fully discharged state.) Specific examples of lithium-containing composite oxides having a layered rock salt-type crystal structure include, for example, LiNiO2, LiCoO2, and LiCo 0.98 Al 0.01 Mg 0.01 O2, LiLiLi 0.5 Co 0.2 Mn 0.3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 O2, LiLiLi 0.33 Co 0.33 Mn 0.33 O2, Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O2 and Li1.15 (Mn 0.65 Ni 0.22 Co 0.13 Examples include O2. Furthermore, when a lithium-containing composite oxide having a layered rock salt-type crystalline structure contains nickel, cobalt, manganese, and aluminum as constituent elements, it is preferable that the atomic ratio of nickel be 50 atomic percent or more. This is because it is easier to obtain a high energy density.

[0073] A lithium-containing composite oxide having a spinel-type crystal structure may be, for example, a compound represented by the following formula (4). Li a Mn (2-b) M14 b O c F d ...(4) (In the formula, M14 is at least one of the following: cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). a to d satisfy 0.9 ≤ a ≤ 1.1, 0 ≤ b ≤ 0.6, 3.7 ≤ c ≤ 4.1, and 0 ≤ d ≤ 0.1, respectively. However, the composition of lithium differs depending on the charge / discharge state, and a is the value in the fully discharged state.) Specific examples of lithium-containing composite oxides having a spinel-type crystal structure include LiMn2O4, for example.

[0074] Lithium-containing phosphate compounds having an olivine-type crystal structure are, for example, compounds represented by the following formula (5). Li a M15PO4···(5) (In the formula, M15 is at least one of the following: cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), niobium (Nb), copper (Cu), zinc (Zn), molybdenum (Mo), calcium (Ca), strontium (Sr), tungsten (W), and zirconium (Zr). a satisfies 0.9 ≤ a ≤ 1.1. However, the composition of lithium varies depending on the charge / discharge state, and a is the value for the fully discharged state.) Specific examples of lithium-containing phosphate compounds having an olivine-type crystal structure include LiFePO4, LiMnPO4, and LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 It could be PO4, for example.

[0075] The lithium-containing composite oxide may also be a compound represented by the following formula (6). (Li2MnO3) x (LiMnO2) 1-x ...(6) (x satisfies 0 ≤ x ≤ 1. However, the lithium composition differs depending on the charge / discharge state, and x is the value for the fully discharged state.)

[0076] In addition, the positive electrode active material particles may be one or more of the following: oxides, disulfides, chalcogenides, and conductive polymers. Oxides may be titanium oxide, vanadium oxide, and manganese dioxide, for example. Disulfides may be titanium disulfide and molybdenum sulfide, for example. Chalcogenides may be niobium selenide, for example. Conductive polymers may be sulfur, polyaniline, and polythiophene, for example. However, the positive electrode active material particles are not particularly limited and may be other materials not listed above.

[0077] Similarly, if the composite particle 10 includes negative electrode active material particles, the negative electrode active material particles may be materials that contribute to the intercalation and deintercalation of lithium ions. In other words, the composite particle 10 may contain one or more types of negative electrode active material particles capable of intercalating and deintercalating lithium. From this perspective, the negative electrode active material particles may be, for example, various carbon materials, metallic materials, and / or other materials.

[0078] When carbon materials are used as negative electrode active material particles, the change in crystal structure during lithium absorption and release is very small, making it easy to stably obtain a high energy density. In addition, since carbon materials also function as negative electrode conductive agents, the conductivity of the negative electrode layer is easily improved.

[0079] Specific carbon materials include, for example, easily graphitizable carbon, poorly graphitizable carbon, and / or graphite. More specifically, the carbon material may be, for example, pyrolytic carbons, cokes, glassy carbon fibers, calcined organic polymer compounds, activated carbon, and carbon blacks. Cokes may include pitch coke, needle coke, and petroleum coke. Calcined organic polymer compounds are, for example, substances obtained by calcining (carbonizing) polymer compounds such as phenolic resins and furan resins at an appropriate temperature. In addition, the carbon material may be low-crystalline carbon heat-treated at a temperature of about 1000°C or lower, or amorphous carbon. The shape of the carbon material is not particularly limited and may be at least one of fibrous, spherical, granular, and flaky.

[0080] The term "metallic material" used as negative electrode active material particles is a general term for materials containing one or more metallic elements and metalloid elements as constituent elements. When carbon material is used as negative electrode active material particles, a high energy density is easily obtained. Metallic materials may be elements, alloys, compounds, two or more of these, or materials containing at least one or more of these phases. However, alloys may include materials consisting of two or more metallic elements, as well as materials containing one or more metallic elements and one or more metalloid elements. Furthermore, alloys may contain nonmetallic elements. The structure of this metallic material may be, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a combination of two or more of these. Such metallic elements and metalloid elements may be, for example, one or more of the metallic elements and metalloid elements capable of forming alloys with lithium.

[0081] Specifically, the metallic and metalloid elements may be, for example, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd), and / or platinum (Pt). In one preferred embodiment, the metallic elements are silicon and tin, because they have excellent ability to intercalate and deintercalate lithium, making it easier to obtain higher energy densities.

[0082] The material containing silicon as a constituent element may be elemental silicon, an alloy of silicon, a compound of silicon, two or more selected from them, or a material containing at least a part of one or more phases of them. Similarly, the material containing tin as a constituent element may be elemental tin, an alloy of tin, a compound of tin, two or more of them, or a material containing at least a part of one or more phases of them. The "elemental substance" described in this specification is an elemental substance in a general sense, so the elemental substance may contain trace amounts of impurities. That is, the purity of the elemental substance is not necessarily limited to 100%.

[0083] The alloy of silicon may contain, for example, any one or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than silicon. The compound of silicon may contain, for example, any one or more of carbon and oxygen as constituent elements other than silicon. Note that the compound of silicon may contain any one or more of a series of elements described for the alloy of silicon as constituent elements other than silicon. Specific examples of the alloy of silicon and specific examples of the compound of silicon include SiB4, SiB6, MgSi, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiO v (0 < v ≤ 2), and / or LiSiO, etc. can be cited. Note that for SiO v v in it may be 0.2 < v < 1.4.

[0084] Tin alloys may contain, for example, any one or more of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as constituent elements other than tin. Tin compounds may contain, for example, any one or more of carbon and oxygen as constituent elements other than tin. Note that tin compounds may also contain any one or more of the series of elements described for tin alloys as constituent elements other than tin. Specific examples of tin alloys and specific examples of tin compounds include SnO w (0 < w ≦ 2), SnSiO3, LiSnO, and / or Mg2Sn, etc.

[0085] In particular, a material containing tin as a constituent element may be, for example, a material (tin-containing material) containing a second constituent element and a third constituent element together with tin as the first constituent element. The second constituent element may be, for example, any one or more of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver, indium, cesium (Ce), hafnium (Hf), tantalum, tungsten, bismuth, and silicon. The third constituent element may be, for example, any one or more of boron, carbon, aluminum, and phosphorus. This is because it is easy to obtain high battery capacity and excellent cycle characteristics. Among them, the tin-containing material may be a material (tin-cobalt-carbon-containing material) containing tin, cobalt, and carbon as constituent elements. This is because it is easy to obtain a high energy density.

[0086] In tin-cobalt-carbon-containing materials, at least a portion of the carbon, which is one of the constituent elements, may be bonded to other constituent elements, such as metallic or metalloid elements. This is because it makes it easier to suppress the aggregation and crystallization of tin. Such tin-cobalt-carbon-containing materials are not limited to materials in which the constituent elements are only tin, cobalt, and carbon (SnCoC). For example, in addition to tin, cobalt, and carbon, this tin-cobalt-carbon-containing material may also contain one or more of the following as constituent elements: silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, and bismuth. In addition to tin-cobalt-carbon-containing materials, there may also be materials containing tin, cobalt, iron, and carbon as constituent elements (tin-cobalt-iron-carbon-containing materials).

[0087] In addition, the negative electrode active material particles may be one or more of the following: metal oxides and polymer compounds. Examples of metal oxides include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of polymer compounds include polyacetylene, polyaniline, and polypyrrole.

[0088] Figure 5 is a schematic diagram showing a composite particle according to another embodiment of the present disclosure. Figure 6 is a schematic cross-sectional view of the composite particle. As shown, the composite particle 10 may further contain a conductive additive 18. Figure 10 is also a schematic cross-sectional view of an electrode component including an electrode mixture 110 formed by powder rolling of the composite particle of the present disclosure, a current collector 130, and a separator 3. The conductive additive 18 may play a role in ensuring electrical contact between electrode active material particles and / or between electrode active material particles and the current collector, thereby improving conductivity in the electrode mixture. At least one of the plurality of electrode active material particles 11 may be in contact with the conductive additive 18. The conductive additive 18 may be held by a binder 16 on the surface 122 of at least one of the plurality of electrode active material particles 11. Additionally or alternatively, at least one conductive additive 18A may be located on the interior side of the composite particle 10, between the plurality of electrode active material particles 11. In other words, at least one conductive additive 18A may be held in a gap formed between a plurality of electrode active material particles 11 without coming into contact with the binder 16.

[0089] The conductive additive 18 may play a role in electrically connecting multiple electrode active material particles 11 in the electrode mixture formed using the composite particles 10. In other words, the conductive additive 18 can improve the electrical conductivity of the electrode mixture by electrically connecting multiple electrode active material particles 11.

[0090] The conductive additive 18 may be located primarily between the electrode active material particles. As shown in Figures 5 and 6, multiple conductive additives 18 may be aggregated and located in local regions between the electrode active material particles. The conductive additive 18 may not be uniformly located across the entire surface 122 of the electrode active material particles, but rather aggregated in local regions to form conductive paths connecting the electrode active material particles. With this structure, the electrode active material particles may be electrically connected by the conductive additive 18. Furthermore, in regions where the conductive additive 18 is not present, the surface 122 of the electrode active material particles is exposed, allowing for favorable conduction of ions. Therefore, by providing such a structure, it may be possible to achieve both excellent electrical conductivity and ionic conductivity.

[0091] The conductive additive 18 may have an average particle size smaller than the electrode active material particles 14. This allows the conductive additive 18 to fit nicely between the electrode active material particles, including the electrode active material particles, during powder rolling using the composite particles 10, thereby improving the electrical conductivity of the resulting electrode composite. For example, the conductive additive 18 may have a particle size of 0.01 μm or more and less than 1 μm, or 0.01 μm or more and 0.5 μm or less. When the average particle size of the conductive additive 18 is within the above range, the conductive additive 18 can be positioned in the gaps between the electrode active material particles in the electrode composite obtained from the composite particles 10, thereby forming a suitable conductive network.

[0092] In this specification, the average particle size of the conductive additive 18 corresponds to the mode diameter of the conductive additive 18. The average particle size of the conductive additive 18 may be calculated from a particle size distribution obtained by a method using laser diffraction and scattering in accordance with ISO 13320 and JIS Z 8825-1. The particle size distribution may have a multimodal distribution containing two or more peaks. In the obtained particle size distribution, the particle size at the peak top of the largest particle size within the range of 0.01 μm or more and less than 1 μm may be taken as the average particle size of the conductive additive 18.

[0093] Generally, because conductive additives 18 tend to aggregate, when the particle size of a powder containing only conductive additives 18 is measured using the laser diffraction / scattering method, it may be observed as a larger particle size than the actual individual particle sizes of conductive additives 18 (for example, particle size measured by microscopy). On the other hand, in the composite particles 10 of this disclosure and the electrode mixture obtained by powder rolling of the composite particles 10, the aggregation of conductive additives 18 can be suppressed by the presence of large electrode active material particles 12, small electrode active material particles 14, and binder 16. Therefore, even when using the same conductive additive 18, the average particle size of conductive additives 18 measured using the laser diffraction / scattering method in a powder containing only conductive additives 18 may differ from the average particle size of conductive additives 18 measured using the laser diffraction / scattering method in the composite particles 10 or electrode mixture. It should be noted that the range of average particle size of conductive additives 18 contained in the composite particles 10 and electrode mixture of this disclosure described above is based on the average particle size of conductive additives 18 measured from the state of the composite particles 10 or electrode mixture.

[0094] The conductive additive 18 can be any known conductive additive used in batteries. For example, if the composite particles 10 include positive electrode active material particles, one or more types of carbon materials may be used as the conductive additive 18. These carbon materials may be, for example, graphite, carbon black, acetylene black, and Ketjen black. However, the conductive additive 18 may also be any conductive material, such as a metallic material or a conductive polymer.

[0095] For example, if the composite particles 10 include negative electrode active material particles, the conductive additive 18 can be at least one selected from carbon black such as thermal black, furnace black, channel black, Ketjen black, and acetylene black; carbon fibers such as graphite, carbon nanotubes, and vapor-grown carbon fibers; metal powders such as copper, nickel, aluminum, and silver; and polyphenylene derivatives.

[0096] The binder 16 content in the composite particles 10 can be between 0.5% by weight and 10% by weight. By including the binder 16 within this range, an electrode composite material having a stable structure containing large electrode active material particles 12 and small electrode active material particles 14 can be obtained by powder rolling the composite particles 10. In other words, by including the binder 16 within the above range, composite particles 10 capable of forming a dry electrode with excellent load characteristics can be obtained without going through a slurry formation process using a solvent. If the load characteristics of the electrode composite material obtained from the composite particles 10 are given greater importance, the binder 16 content in the composite particles 10 is preferably between 0.5% by weight and 2% by weight.

[0097] It is preferable that the content of large electrode active material particles 12 in the composite particle 10 is greater than the content of small electrode active material particles 14. This makes it easier to obtain a structure in which small electrode active material particles 14 are arranged in the gaps between multiple large electrode active material particles 12. For example, the content of large electrode active material particles 12 may be 70% by weight or more and 99% by weight or less, or 80% by weight or more and 99% by weight or less. Also, the content of small electrode active material particles 14 may be 0.5% by weight or more and 20% or less, or 0.5% by weight or more and 10% by weight or less. When the content of large electrode active material particles 12 and small electrode active material particles 14 are within the above ranges, a suitable structure can be obtained in which small electrode active material particles 14 are arranged between multiple large electrode active material particles 12.

[0098] According to the composite particles 10 of this disclosure, an electrode composite can be formed simply by powder rolling the composite particles 10 without mixing in solvents or the like. Therefore, the electrode composite, which is a pressure-molded body formed by powder rolling, may have the same material composition as the composite particles 10. In other words, the content of large electrode active material particles 12, small electrode active material particles 14, and binder 16 in the electrode composite obtained by powder rolling the composite particles 10 of this disclosure may be the same as the content in the composite particles 10.

[0099] The components of materials such as electrode active material particles 11, binder 16, and conductive additive 18 contained in the composite particle 10, or the electrode composite material formed using the composite particle, can be determined, for example, by mass spectrometry using a mass spectrometer and / or by high-resolution nuclear magnetic resonance spectroscopy. 1 It can be analyzed by 1H-NMR analysis.

[0100] [Manufacturing method for electrode composite material] This disclosure also relates to a method for manufacturing electrode composites. One manufacturing method is described below as an example, but this disclosure is not limited to this method. Furthermore, the order of description and other chronological matters below are merely for explanatory purposes and are not necessarily binding.

[0101] The method for manufacturing electrode composite materials includes forming composite particles and forming a pressure-molded body by pressurizing the composite particles.

[0102] (Formation of composite particles) The composite particles of this disclosure may be formed by the following method: Large electrode active material particles, small electrode active material particles, and a binder are dispersed in a solvent (e.g., N-methyl-2-pyrrolidone (NMP)) in a predetermined weight ratio to form a slurry. The slurry is then applied to a release film and dried to obtain a composite material film. By pulverizing the obtained composite material film, composite particles containing large electrode active material particles, small electrode active material particles, and a binder can be obtained. In addition, a conductive additive may be added during slurry formation as needed.

[0103] (Forming of pressure-molded bodies) After obtaining composite particles, the composite particles are subjected to pressure to form an electrode composite as a pressure-molded body. The pressure-molded body may be formed by powder rolling. More specifically, for example, the composite particles may be powder-rolled using a twin-roll mill to obtain the electrode composite as a pressure-molded body. Various conditions in powder rolling, such as the peripheral speed ratio and linear pressure, may be appropriately changed depending on the materials contained in the composite particles and the dimensions of the target electrode composite. By doing so, an electrode composite with excellent load characteristics can be obtained, comprising at least large electrode active material particles, small electrode active material particles, and a binder.

[0104] The embodiments of this disclosure have been described above, but these are merely typical examples. Therefore, those skilled in the art will easily understand that this disclosure is not limited thereto, and various embodiments are conceivable without altering the essence of this disclosure.

[0105] Furthermore, the above-described embodiment of the present disclosure includes the following preferred embodiments. First aspect: It comprises multiple electrode active material particles and a binder. The plurality of electrode active material particles include large electrode active material particles with a relatively large average particle size and small electrode active material particles with a relatively small average particle size. The binder is a thermoplastic elastomer, A composite particle in which at least one of the plurality of electrode active material particles is in contact with the binder. Second aspect: The composite particle according to the first embodiment, wherein the thermoplastic elastomer is a hydrogenated polymer elastomer. Third aspect: The composite particle according to the first or second embodiment, wherein the thermoplastic elastomer is at least one of hydrogenated nitrile rubber and hydrogenated styrene-butadiene rubber. Fourth aspect: The electrode active material comprises a plurality of small electrode active material particles and a plurality of large electrode active material particles, A composite particle according to any one of the first to third embodiments, wherein at least one of the electrode active material small particles is located between a plurality of electrode active material large particles. Fifth aspect: The composite particle according to the fourth embodiment, wherein the at least one electrode active material small particle located between a plurality of electrode active material large particles is not in contact with the binder. Sixth aspect: The composite particle according to any one of the first to fifth embodiments, wherein the maximum particle size of the composite particle is 50 μm or less. Seventh aspect: The composite particle according to any of the first to sixth embodiments, wherein the average particle size of the composite particle is 30 μm or more and 40 μm or less. Eighth aspect: The composite particle according to any of the first to seventh embodiments, wherein the average particle size of the electrode active material small particles is 5% or more and 30% or less of the average particle size of the electrode active material large particles. Appearance 9: The average particle size of the electrode active material large particles is 10 μm or more and 30 μm or less. The composite particle according to any of the first to eighth embodiments, wherein the average particle size of the electrode active material small particles is 1 μm or more and 8 μm or less. Tenth aspect: It further contains a conductive additive, The conductive additive is in contact with at least one of the plurality of electrode active material particles, as described in any of the first to ninth embodiments. Appearance No. 11: The composite particle according to the tenth embodiment, wherein the average particle size of the conductive additive is 0.01 μm or more and less than 1 μm. Appearance 12: The composite particle according to any of the first to eleventh embodiments, wherein the binder content is 0.5% by weight or more and 10% by weight or less. Appearance 13: The composite particle according to any of the first to twelfth embodiments, wherein the binder content is 0.5% by weight or more and 2% by weight or less. Appearance 14: The content of the electrode active material large particles is 80% by weight or more and 99% by weight or less. The composite particle according to any of the first to thirteenth embodiments, wherein the content of the electrode active material small particles is 0.5% by weight or more and 10% by weight or less. Appearance 15: The composite particle according to any one of the first to fourteenth embodiments, wherein the electrode active material particles have a contact region that comes into contact with the binder and a non-contact region that does not come into contact with the binder. Appearance 16: The composite particle according to any one of the first to fifteen embodiments, wherein the electrode active material particles are positive electrode active material particles. Appearance 17: An electrode composite material which is a pressure-molded body of the composite particles described in any of the first to sixteenth embodiments. Apparatus 18: It comprises a positive electrode, a negative electrode, and an electrolyte. A secondary battery in which at least one of the positive electrode and the negative electrode contains the composite particles described in any of the first to fifteenth embodiments. Appearance 19: The process involves mixing multiple electrode active material particles with a binder to form composite particles, and The composite particles are pressed to form a pressure-molded body. Includes, The plurality of electrode active material particles include large electrode active material particles with a relatively large average particle size and small electrode active material particles with a relatively small average particle size. The binder is a thermoplastic elastomer, A method for manufacturing an electrode composite, wherein in the composite particles, at least one of the plurality of electrode active material particles is in contact with the binder. [Examples]

[0106] A demonstration test was conducted in accordance with this disclosure.

[0107] (Formation of composite particles) Acetylene black (Denka Co., Ltd., Li-435) was used as a conductive additive, HNBR as a binder, lithium nickelate (NCA) with an average particle size of 18 μm as the large electrode active material particles, and lithium nickelate (NCA) with an average particle size of 3 μm as the small electrode active material particles. A slurry was obtained by dispersing these materials in N-methyl-2-pyrrolidone (NMP) in a weight ratio of large electrode active material particles:small electrode active material particles:conductive additive:binder = 68.1:29.2:1.6:1.1. The hydrogenation rate of HNBR was 99%, and the acrylonitrile content was 34%. The average particle size of the conductive additive (catalog value) was 23 nm. The average particle sizes of large and small electrode active material particles were calculated from the particle size distribution obtained using the SALD-7500nano laser diffraction-scattering method in accordance with ISO 13320 and JIS Z 8825-1, respectively.

[0108] Next, the slurry was applied to one side of the release film using a doctor blade type table coater with a gap set to 500 μm, and then dried in an oven at 100°C for 10 minutes.

[0109] The composite film obtained by drying was crushed using a mortar and pestle to obtain composite particles. The maximum particle size of the obtained composite particles was measured by sieving and found to be 50 μm. The obtained composite particles were photographed using a scanning electron microscope (SEM). The obtained images are shown in Figures 7 and 8. In addition, the average particle size of the composite particles, large electrode active material particles, small electrode active material particles, and conductive additive was calculated from the particle size distribution obtained by laser diffraction / scattering method in accordance with ISO 13320 and JIS Z 8825-1 using SALD-7500nano. The average particle size of the composite particles was 38 μm. Furthermore, it was confirmed that the average particle sizes of the large electrode active material particles and small electrode active material particles were equivalent to the average particle size of the raw materials used to form the composite particles. In addition, the average particle size of the conductive additive was 0.1 μm, and it was confirmed that the conductive additive was slightly aggregated due to the formation of the composite particles.

[0110] (Formation of electrode composite material) The composite particles were powder-rolled using a twin-roll mill to obtain an electrode composite as a press-molded body. Powder rolling was performed at a peripheral speed ratio of 10:8 and a linear pressure of 0.8 kN / cm. A cross-section of the obtained electrode composite was photographed using a scanning electron microscope (SEM), and the average particle sizes of the large electrode active material particles, small electrode active material particles, and conductive additive contained in the electrode composite were calculated from the obtained SEM images. It was confirmed that these average particle sizes were equivalent to those of each material measured in the composite particles.

[0111] (Preparation of comparative wet electrodes) The coated electrode may be formed by the following method. Large electrode active material particles, small electrode active material particles, a conductive additive, and a binder were mixed to form a slurry dispersed in a solvent (e.g., N-methyl-2-pyrrolidone (NMP)), which was then coated onto one side of an Al foil using a doctor blade table coater. After drying in an oven at 100°C for 10 minutes, the slurry was adjusted to the same volume density as in Example 1 using a uniaxial press.

[0112] (Evaluation of electrode composite materials) The electrode composite material obtained by the method described above was prepared according to the following procedure.

[0113] To evaluate the electrode mixtures, cells were fabricated using the electrode mixtures from the examples and comparative wet electrodes. Specifically, electrode mixtures punched to a predetermined cell size and metallic lithium plates were stacked with a separator in between. After injecting the electrolyte (1M LiPF6, EC:EMC=25:75vol), vacuum impregnation was performed, and various cells were fabricated by performing the initial charge and discharge at a constant current of 0.2CA. Two cells containing the electrode mixtures from the examples (Examples 1-2) and two cells containing comparative wet electrodes (Comparative Examples 1-2) were fabricated and evaluated.

[0114] (Evaluation of capacity retention rate) The capacity retention rate (constant current discharge capacity ratio at 0.2 CA) was measured when each cell was discharged to 2.5 V at a constant current of 1 CA under a temperature of 25°C. The evaluation results are shown in Table 1.

[0115] [Table 1]

[0116] (Evaluation of reaction capacity) Various cells were subjected to charging and discharging. The charging and discharging conditions were as follows. The evaluation results are shown in Figure 11. Discharge conditions: CC discharge 26.8mA / 4.25V cutoff Charging conditions: CC charging 26.8mA / 2.5V cutoff Temperature: 25℃

[0117] The evaluation results showed that the cells of Examples 1 and 2, which were equipped with electrode mixtures made using the composite particles of this disclosure, exhibited a higher capacity retention rate compared to the cells of Comparative Examples 1 and 2, which were made using wet electrodes. Furthermore, the graph shown in Figure 11 indicates that the cells equipped with electrode mixtures made using the composite particles of this disclosure were able to maintain a higher voltage from the mid-to-late stages of discharge compared to wet electrodes. From the above, it was demonstrated that the composite particles of this disclosure can provide an electrode mixture with excellent load characteristics as a dry electrode. [Industrial applicability]

[0118] The composite particles, electrode mixtures, and secondary batteries of this disclosure can be used in various fields where energy storage is envisioned. Although these are merely examples, the composite particles, electrode mixtures, and secondary batteries of this disclosure can be used in the electrical, information, and communication fields where mobile devices are used (e.g., the electrical and electronic equipment field or mobile device field, including small electronic devices such as mobile phones, smartphones, laptops and digital cameras, activity trackers, ARM computers, electronic paper, RFID tags, card-type electronic money, and smartwatches), household and small industrial applications (e.g., power tools, golf carts, household, caregiving, and industrial robots), large industrial applications (e.g., forklifts, elevators, and port cranes), transportation systems (e.g., hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power grid applications (e.g., various power generation systems, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT fields and space and deep-sea applications (e.g., space probes, submersible research vessels, etc.). [Explanation of Symbols]

[0119] 1 positive electrode 11 Electrode active material particles 12 Electrode active material large particles 14 Electrode active material small particles 16 Binders 18 Conductive additives 110 Electrode composite material 130 Positive electrode current collector 2 negative electrode 3 Separators 5 Electrode composition layer 100A,100B electrode assembly 60 Exterior 81 Electrode terminal 82 Insulating material 500 secondary battery

Claims

1. It comprises multiple electrode active material particles and a binder. The plurality of electrode active material particles include large electrode active material particles with a relatively large average particle size and small electrode active material particles with a relatively small average particle size. The binder is a thermoplastic elastomer, A composite particle in which at least one of the plurality of electrode active material particles is in contact with the binder.

2. The composite particle according to claim 1, wherein the thermoplastic elastomer is a hydrogenated polymer elastomer.

3. The composite particle according to claim 1 or 2, wherein the thermoplastic elastomer is at least one of hydrogenated nitrile rubber and hydrogenated styrene-butadiene rubber.

4. It comprises a plurality of small electrode active material particles and a plurality of large electrode active material particles, The composite particle according to any one of claims 1 to 3, wherein at least one of the electrode active material small particles is located between a plurality of electrode active material large particles.

5. The composite particle according to claim 4, wherein the at least one electrode active material small particle located between a plurality of electrode active material large particles is not in contact with the binder.

6. The composite particle according to any one of claims 1 to 5, wherein the maximum particle size of the composite particle is 50 μm or less.

7. The composite particle according to any one of claims 1 to 6, wherein the average particle size of the composite particle is 30 μm or more and 40 μm or less.

8. The composite particle according to any one of claims 1 to 7, wherein the average particle size of the electrode active material small particles is 5% or more and 30% or less of the average particle size of the electrode active material large particles.

9. The average particle size of the electrode active material large particles is 10 μm or more and 30 μm or less. The composite particle according to any one of claims 1 to 8, wherein the average particle size of the electrode active material small particles is 1 μm or more and 8 μm or less.

10. It further contains a conductive additive, The composite particle according to any one of claims 1 to 9, wherein the conductive additive is in contact with at least one of the plurality of electrode active material particles.

11. The composite particle according to claim 10, wherein the average particle size of the conductive additive is 0.01 μm or more and less than 1 μm.

12. The composite particle according to any one of claims 1 to 11, wherein the binder content is 0.5% by weight or more and 10% by weight or less.

13. The composite particle according to any one of claims 1 to 12, wherein the binder content is 0.5% by weight or more and 2% by weight or less.

14. The content of the electrode active material large particles is 80% by weight or more and 99% by weight or less. The composite particle according to any one of claims 1 to 13, wherein the content of the electrode active material small particles is 0.5% by weight or more and 10% by weight or less.

15. The composite particle according to any one of claims 1 to 14, wherein the electrode active material particles comprise a contact region that contacts the binder and a non-contact region that does not contact the binder.

16. The composite particle according to any one of claims 1 to 15, wherein the electrode active material particles are positive electrode active material particles.

17. An electrode composite material which is a pressure-molded body of the composite particles according to any one of claims 1 to 16.

18. It comprises a positive electrode, a negative electrode, and an electrolyte. A secondary battery in which at least one of the positive electrode and the negative electrode contains the composite particles described in any one of claims 1 to 15.

19. The process involves mixing multiple electrode active material particles with a binder to form composite particles, and The composite particles are pressed to form a pressure-molded body. Includes, The plurality of electrode active material particles include large electrode active material particles with a relatively large average particle size and small electrode active material particles with a relatively small average particle size. The binder is a thermoplastic elastomer, A method for manufacturing an electrode composite, wherein in the composite particles, at least one of the plurality of electrode active material particles is in contact with the binder.

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