Active material-conductive agent composite, electrode for rechargeable battery including active material-conductive agent composite, rechargeable battery, and non-aqueous electrolyte rechargeable battery

Abstract

An active material-conductive agent composite, an electrode for a rechargeable battery including the active material-conductive agent composite, a rechargeable battery, and a non-aqueous electrolyte rechargeable battery are provided. Examples of the present disclosure maintain high charge / discharge efficiency of a rechargeable battery including an electrode including an active material, such as a silicon-based active material, and manufactured by a dry method. Examples of the present disclosure include an active material-conductive agent composite including an active material capable of intercalating and deintercalating lithium, a conductive agent, and a first binder that binds the active material and the conductive agent. The active material is in the form of spherical particles, and the conductive agent is bonded to the surface of the active material by a first binder so as to extend in the radial direction of the active material.

Description

[0001] This application claims priority to Japanese Patent Application No. 2024-143288, filed on August 23, 2024, with the Japan Patent Office, and Korean Patent Application No. 10-2025-0116060, filed on August 20, 2025, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to an active material-conductive agent complex, an electrode for a rechargeable battery including the active material-conductive agent complex, and a rechargeable battery including the electrode. Background Technology

[0003] Rechargeable batteries, including lithium-ion rechargeable batteries, are commonly used as power sources for devices such as smartphones and / or laptops. As these electronic devices have become smaller and lighter, rechargeable batteries with higher energy density are increasingly advantageous.

[0004] The demand for rechargeable batteries that will be used as power sources for vehicles such as electric vehicles and / or hybrid vehicles has increased, and rechargeable batteries with relatively high energy density are needed to ensure at least the same performance as comparable gasoline engines.

[0005] To meet this need for improved energy density, high-capacity electrodes, including those made of carbon-based active materials, are advantageous.

[0006] These electrodes are typically manufactured using a wet manufacturing process, in which active materials, conductive additives, binders, etc., are dispersed in a solvent, stirred, and then coated onto a current collector foil and dried. Recently, a dry manufacturing process has been developed, which has the potential to reduce or eliminate the drying process in the wet manufacturing process, thereby reducing the environmental impact (Japanese Patent No. 7227328). Summary of the Invention

[0007] However, when the electrode is manufactured using a dry manufacturing method and includes an active material that has a relatively large volume change during charge and discharge (such as silicon-based active materials as high-capacity active materials), the charge and discharge efficiency of the rechargeable battery equipped with the electrode may be significantly reduced.

[0008] The exemplary embodiments of this disclosure address the aforementioned challenges, one of which is due to the expansion and contraction of the active material during charging and discharging, the interruption of the conductive path, and the isolation of the active material at the end of the discharge.

[0009] In other words, some example implementations include the following: [1] An active material-conductive agent composite, the active material-conductive agent composite comprising: an active material capable of lithium intercalation and deintercalation, Conductive agent; The first adhesive binds the active material and the conductive agent together. The active substance is in the form of spherical particles, and The conductive agent is bonded to the surface of the active material by a first binder to elongate in the diametrical direction of the active material.

[0010] [2] As described in [1], the active substance-conductive agent complex, wherein the conductive agent is in fibrous form.

[0011] [3] The active material-conductive agent complex as described in [1] or [2], wherein the active material is a silicon-based active material.

[0012] [4] An electrode for a rechargeable battery, the electrode comprising: The active substance-conductive agent complex described in any one of [1] to [3]; The second adhesive is a different adhesive from the first adhesive; The third adhesive may be the same as or different from the first adhesive. The second binder is made of or includes fluoropolymers in the form of fibrils.

[0013] [5] An electrode for a rechargeable battery as described in [4], wherein a second binder and a third binder bond multiple active material-conductive agent complexes together.

[0014] [6] An electrode for a rechargeable battery as described in [4] or [5], wherein the electrode includes a current collector, an electrode mixture layer, and a conductive adhesive layer between the current collector and the electrode mixture layer, and The electrode mixture layer comprises an active material-conductive agent complex, a second binder, and a third binder.

[0015] [7] An electrode for a rechargeable battery as described in any of [4] to [6], wherein the conductive adhesive layer comprises a carbon material, an adhesive for the substrate layer, and a dispersant, and the adhesive for the substrate layer is a styrene-butadiene copolymer or a styrene-acrylate copolymer, or includes a styrene-butadiene copolymer or a styrene-acrylate copolymer.

[0016] [8] A rechargeable battery comprising a positive electrode and a negative electrode, wherein the negative electrode is an electrode for a rechargeable battery as described in any one of [4] to [7].

[0017] [9] A non-aqueous electrolyte rechargeable battery, the non-aqueous electrolyte rechargeable battery comprising a positive electrode and a negative electrode, wherein the negative electrode is or comprises an electrode for a rechargeable battery as described in any one of [4] to [7].

[0018] According to an example embodiment, the charge / discharge efficiency of a rechargeable battery equipped with electrodes comprising active materials (such as silicon-based active materials) and manufactured by a dry process can be maintained at a high level. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating a non-aqueous electrolyte rechargeable battery according to some example embodiments. Detailed Implementation

[0020] Referring now to the embodiments in more detail, examples of which are illustrated in the accompanying drawings. In this regard, the exemplary embodiments given may have different forms and should not be construed as limited to the description set forth herein. Therefore, exemplary embodiments are described only with reference to the accompanying drawings to explain aspects of this specification. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. When a statement such as “at least one of…” follows a list of elements, the statement modifies the entire list of elements, not individual elements within that list. Since this disclosure described below allows for one or more suitable modifications and numerous exemplary embodiments, exemplary embodiments are illustrated in the accompanying drawings and described in more detail in the detailed description.

[0021] The following describes exemplary embodiments in detail, enabling those skilled in the art to readily implement the embodiments. However, this disclosure can be implemented in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0022] The terminology used herein is for describing exemplary embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless the context clearly indicates otherwise. Unless otherwise defined, all chemical names, technical and scientific terms, and terms as defined in common dictionaries, should be interpreted as having meanings consistent with the context of the relevant field and should not be interpreted in an idealized or overly formal sense. It is understood that although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. Therefore, a first element may be referred to as a second element without departing from the teachings of this disclosure. Similarly, a second element may be referred to as a first element.

[0023] As used herein, the phrase “combination of” means mixtures of components, laminates, complexes, copolymers, alloys, blends, reaction products, etc.

[0024] As used herein, unless the context clearly indicates otherwise, the singular forms of words such as “a,” “one,” and “the” are also intended to include the plural forms. As used herein, the term “use” and its variations may be considered synonymous with the term “utilize” and its variations, respectively. As used herein, when expressions such as “at least one of…,” “one of…,” and “selected from…” follow / before a list of elements, such expressions modify the entire list of elements, not individual elements within that list. For example, the expressions “at least one of a to c,” “at least one of a, b, or c,” and “at least one of a, b, and / or c” can mean only a, only b, only c, (e.g., simultaneously) both a and b, (e.g., simultaneously) both a and c, (e.g., simultaneously) both b and c, all of a, b, and c, or variations thereof.

[0025] It should be understood here that terms such as “comprising,” “including,” “having,” or variations thereof are intended to indicate the presence of the features, quantities, steps, elements, or combinations thereof embodied, but these terms do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0026] The term “may” is understood to refer to “one or more exemplary embodiments of this disclosure,” some of which include the described element, and some of which do not include the element and / or include alternative elements. Similarly, alternative language such as “or” refers to “one or more exemplary embodiments of this disclosure,” each of which includes the corresponding listed item. For ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “up,” “bottom,” and “top” may be used herein to describe the relationship between one element or feature as shown in the accompanying drawings and another element(s). It is understood that, in addition to the orientations depicted in the accompanying drawings, the spatial relative terms are intended to cover different orientations of the device in use or operation. For example, when the device in the accompanying drawings is flipped, an element described as “below” or “under” other elements or features will subsequently be oriented “above” or “on” said other elements or features. Thus, the term “below” can cover both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or in other orientations), and the spatial relative descriptive terms used herein should be interpreted accordingly. In this document, "consistent essentially of" means that any additional components will not substantially affect the chemical, physical, optical, or electrical properties of the material. Furthermore, in this specification, the phrase "in a plan view" or "plan view" means a view of the target portion from above, and the phrase "in a cross-section" means a view of a cross-section formed by vertically cutting the target portion from the side. In this disclosure, "excluding one or any component," "excluding one or any component," and / or "free of 'component'" mean that the "component" has not been added, selected, or used as a component or compound in the composition, but may still be included in less than a suitable amount due to other impurities and / or external factors.

[0027] It is understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element may be directly on the other element, or there may be an intervening element between them. Conversely, when an element is referred to as being "directly on" another element, there is no intervening element.

[0028] Furthermore, the term "layer" here includes not only shapes that form across the entire surface when viewed from a plan view, but also shapes that form on a portion of the surface.

[0029] Here, "or" will not be interpreted as having an exclusive meaning. For example, "A or B" is interpreted as including A, B, A+B, etc.

[0030] The term "metal" is interpreted as encompassing common metals, transition metals, and metalloids (semi-metals).

[0031] As used herein, poly(meth)acrylic acid refers to polyacrylic acid (PAA) and / or polymethacrylic acid (PMAA).

[0032] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it means that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0033] The following describes the specific construction of a non-aqueous electrolyte rechargeable battery according to some example embodiments.

[0034] 1. Basic structure of non-aqueous electrolyte rechargeable batteries: According to some example embodiments, a non-aqueous electrolyte rechargeable battery is a rechargeable lithium-ion battery that includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte configured to house them therein.

[0035] There are no particular restrictions on the shape of rechargeable lithium-ion batteries, but they can be, for example, cylindrical, prismatic, laminated, or button-shaped.

[0036] In the following text, refer to Figure 1 Describes a non-aqueous electrolyte rechargeable battery according to an example embodiment. Figure 1 This is a schematic diagram illustrating a non-aqueous electrolyte rechargeable battery according to an example embodiment. (Refer to...) Figure 1 A rechargeable lithium battery 100 according to an exemplary embodiment of the present disclosure includes: a battery cell including a positive electrode 114, a negative electrode 112 facing the positive electrode 114, a separator 113 between the positive electrode 114 and the negative electrode 112, and an electrolyte (not shown) for a rechargeable lithium battery impregnating the positive electrode 114, the negative electrode 112 and the separator 113; a battery housing 120 for housing the battery cell; and a sealing member 140 for sealing the battery housing 120.

[0037] 1-1. Positive electrode: The positive electrode includes a positive electrode current collector and a layer of positive electrode mixture on the positive electrode current collector.

[0038] The positive electrode current collector can be or includes any material, as long as the material is a conductor. The positive electrode current collector is, for example, plate-shaped or thin, and can be made of or include aluminum, stainless steel, nickel-plated steel, etc.

[0039] The positive electrode mixture layer may include at least a positive electrode active material, and may also include a conductive agent and a positive electrode binder.

[0040] The positive electrode active material can be or includes, for example, a transition metal oxide or solid solution oxide comprising lithium, and is not particularly limited thereto, as long as the positive electrode active material can electrochemically insert and extract lithium ions. Examples of transition metal oxides comprising lithium include Li. 1.0 Ni 0.88 Co 0.1 Al 0.01 Mg 0.01 O2, etc. Additionally, examples of transition metal oxides including lithium may also include Li·Co composite oxides (such as LiCoO2), Li·Ni·Co-Mn composite oxides (such as LiNi...). x Co y Mn z Solid solution oxides include Li₂, Li-Ni composite oxides (such as LiNiO₂), and Li-Mn composite oxides (such as LiMn₂O₄). Examples of solid solution oxides may include Li₂. a Mn x Co y Ni z O2 (1.150≤a≤1.430, 0.45≤x≤0.6, 0.10≤y≤0.15, 0.20≤z≤0.28), LiMn 1.5 Ni 0.5 O4. On the other hand, there are no particular restrictions on the content (ratio) of the positive electrode active material, as long as the ratio is suitable for the positive electrode mixture layer of a non-aqueous electrolyte rechargeable battery. Furthermore, these compounds can be used alone or in mixtures of various types.

[0041] There are no particular restrictions on the conductive agent, as long as it increases the conductivity of the positive electrode. Examples of conductive agents include reagents containing one or more of carbon black, natural graphite, artificial graphite, fibrous carbon, and nanomaterials.

[0042] Examples of carbon black may include at least one of furnace black, channel black, thermal crack black, Ketjen black, and acetylene black.

[0043] Examples of fibrous carbon can include carbon fibers, etc.

[0044] Examples of nanomaterials may include at least one of carbon nanotubes, carbon nanofibers, single-layer graphene, and multilayer graphene.

[0045] There are no particular restrictions on the amount of conductive agent, and it can be any amount suitable for the positive electrode mixture layer of a non-aqueous electrolyte rechargeable battery.

[0046] The positive electrode binder may be or include at least one of the following: fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride; ethylene resins such as styrene-butadiene rubber and ethylene-propylene-diene terpolymer; acrylonitrile-butadiene rubber; fluororubber; polyvinyl acetate; polymethyl methacrylate; polyethylene; polyvinyl alcohol; carboxymethyl cellulose; carboxymethyl cellulose derivatives (salts of carboxymethyl cellulose, etc.); nitrocellulose, etc. There are no particular limitations on the positive electrode binder, as long as it can bond the positive electrode active material and the conductive agent to the positive electrode current collector. From the viewpoint of increasing the weight per unit area of ​​the positive electrode mixture layer, it is desirable that the positive electrode mixture layer includes a fluoropolymer (such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride) as a binder, and that the binder content in the positive electrode mixture layer is greater than or equal to about 0.5 parts by weight and less than or equal to about 10 parts by weight. When the binder content is within this range, the mechanical strength of the positive electrode mixture layer is improved to a level that ensures the desired processability, and the energy density of the positive electrode plate can be increased.

[0047] 1-2, Negative Electrode: The negative electrode is described in detail below.

[0048] 1-3. Diaphragm: There are no particular limitations on the separator, and any separator can be used, as long as it is used for a rechargeable lithium-ion battery. The separator can be or include porous membranes, nonwoven fabrics, etc., that individually or in combination exhibit the desired or improved high-rate discharge performance. The resin constituting the separator can be or include at least one of the following: polyolefin resins (such as polyethylene, polypropylene, etc.), polyester resins (such as polyethylene terephthalate, polybutylene terephthalate, etc.), polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-ethylene-tetrafluoroethylene copolymer, etc. On the other hand, there are no particular restrictions on the porosity of the separator, and the porosity of the separator of a conventional rechargeable lithium-ion battery can be used arbitrarily.

[0049] On the surface of the separator, there may be a heat-resistant layer including inorganic particles to improve heat resistance or a layer including an adhesive for fixing battery elements by adhering to the electrode assembly. The aforementioned inorganic particles may include at least one of Al2O3, AlOOH, Mg(OH)2, SiO2, etc. Examples of the adhesive may include at least one of a vinylidene fluoride-hexafluoropropylene copolymer, an acid-modified product of a vinylidene fluoride polymer, and a styrene-(meth)acrylate copolymer.

[0050] 1-4. Non-aqueous electrolyte: As the non-aqueous electrolyte solution, the same non-aqueous electrolyte solution as conventionally used for rechargeable lithium-ion batteries can be used without particular limitation. The non-aqueous electrolyte solution has a composition in which an electrolyte salt is included in a non-aqueous solvent, which is a solvent for the electrolyte solution. Examples of the non-aqueous solvent may include at least one of the following, which can be used alone or as a mixture of two or more solvents: cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, fluoroethylene carbonate, and vinylene carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; chain carbonates such as dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate; chain esters such as methyl formate, methyl acetate, methyl butyrate, ethyl propionate, propyl propionate; ethers such as tetrahydrofuran or its derivatives, 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, methyl diglycol dimethyl ether, ethylene glycol monopropyl ether, or propylene glycol monopropyl ether; nitriles such as acetonitrile and benzonitrile; dioxolane or its derivatives; thioethane; sulfolane; and sultone or its derivatives. On the other hand, when two or more types of non-aqueous solvents are mixed, the mixing ratio of each of each non-aqueous solvent can be the mixing ratio that can be used in conventional rechargeable lithium-ion batteries.

[0051] Examples of the electrolyte salt may include: inorganic ionic salts including at least one of lithium (Li), sodium (Na), and potassium (K), such as or including LiClO4, LiBF4, LiAsF6, LiPF6, LiPF 6-x (C n F 2n+1 ) x [provided that 1 < x < 6 and n = 1 or 2], LiSCN, LiBr, LiI, Li2SO4, Li2B 10 Cl 10At least one of NaClO4, NaI, NaSCN, NaBr, KClO4, and KSCN; or organic ionic salts such as LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2)(C4F9SO2), LiC(CF3SO2)3, LiC(C2F5SO2)3, (CH3)4NBF4, (CH3)4NBr, (C2H5)4N The following ionic compounds can be used: ClO4, (C2H5)4NI, (C3H7)4NBr, (n-C4H9)4NClO4, (n-C4H9)4NI, (C2H5)4N-maleate, (C2H5)4N-benzoate, (C2H5)4N-phthalate, lithium stearyl sulfonate, lithium octyl sulfonate, lithium dodecylbenzene sulfonate, etc., and these ionic compounds can be used alone or in mixtures of two or more types of compounds. The concentration of the electrolyte salt can be the same as that of the non-aqueous electrolyte used in conventional rechargeable lithium-ion batteries, and there are no particular limitations. In this example embodiment, it is desirable to use a non-aqueous electrolyte comprising the above-mentioned lithium compounds (electrolyte salts) at a concentration greater than or equal to about 0.8 mol / L and less than or equal to about 1.5 mol / L.

[0052] On the other hand, various additives can be added to the non-aqueous electrolyte. Examples of such additives may include at least one of the following: negative electrode additives, positive electrode additives, ester additives, carbonate additives, sulfate ester additives, phosphate ester additives, borate ester additives, acid anhydride additives, and electrolyte additives. Any one of the above additives may be added to the non-aqueous electrolyte, or multiple types of additives may be added.

[0053] 2. Construction of a non-aqueous electrolyte rechargeable battery according to the characteristics of the example embodiment: The following describes the characteristic construction of a non-aqueous electrolyte rechargeable battery according to some example embodiments.

[0054] The negative electrode includes a negative electrode current collector, a negative electrode mixture layer on the negative electrode current collector, and an adhesive layer (also called a substrate layer) between the negative electrode current collector and the negative electrode mixture layer.

[0055] The negative electrode current collector can be any conductive material, such as plate-shaped or thin-walled, and can be made of or include copper, stainless steel, nickel-plated steel, etc.

[0056] In this example embodiment, the negative electrode mixture layer is a self-supporting layer formed by a dry process and includes a negative electrode active material, a conductive agent, and a negative electrode binder.

[0057] There are no particular limitations on the negative electrode active material, as long as it is in particulate form and can electrochemically insert and deintercalate lithium ions. The particle shape of the negative electrode active material can vary, and may be spherical, polygonal, needle-like, scaly, or irregular in shape. In this example embodiment, spherical negative electrode active material is used as an example. Spherical shape means that the overall shape of the particle is spherical or approximately spherical. The particle size of the negative electrode active material can be greater than or equal to about 0.1 μm and less than or equal to about 50 μm, and in this example embodiment, as an example, a negative electrode active material having a particle size in the range of greater than or equal to about 1 μm and less than or equal to about 20 μm can be used.

[0058] Negative electrode active materials include, for example, graphitic active materials (artificial graphite, natural graphite, mixtures of artificial and natural graphite, natural graphite coated with artificial graphite, etc.), silicon-based active materials (mixtures or complexes of silicon (Si) or its oxide particles with graphitic active materials, silicon particles, alloys including silicon as a matrix material), tin-based active materials (e.g., mixtures or complexes of tin (Sn) or its oxide particles with graphitic active materials, tin particles, alloys including tin as a matrix material), metallic lithium, such as Li4Ti5O 12 At least one of titanium oxide compounds, lithium nitride, etc.

[0059] As the negative electrode active material, only one type of negative electrode active material listed above can be used, or two or more types of negative electrode active materials can be used in combination. Among these types of negative electrode active materials, high-capacity active materials exceeding about 350 mAh / g, about 500 mAh / g or greater, about 1000 mAh / g or greater, and about 1500 mAh / g or greater are advantageous. Examples of such high-capacity active materials can include silicon-based active materials. The aforementioned silicon oxide can be represented as SiO. x (0≤x≤2). When the total negative electrode mixture layer is 100% by mass, the amount of negative electrode active material in the negative electrode mixture layer (the total amount when two or more types of negative electrode active materials are used) can be greater than or equal to about 80% by mass and less than or equal to about 99% by mass, greater than or equal to about 85% by mass and less than or equal to about 99% by mass, or greater than or equal to about 90% by mass and less than or equal to about 99% by mass.

[0060] There are no particular limitations on the conductive agent, as long as it increases the conductivity of the negative electrode mixture layer. Examples of conductive agents include those containing at least one of carbon black, natural graphite, artificial graphite, fibrous carbon, and nanomaterials.

[0061] Examples of carbon black may include at least one of furnace black, channel black, thermal crack black, Ketjen black, and acetylene black.

[0062] Examples of fibrous carbon can include carbon fibers.

[0063] Examples of nanomaterials may include at least one of carbon nanotubes, carbon nanofibers, monolayer graphene, and multilayer graphene.

[0064] Among these carbon materials, carbon materials with elongated shapes (such as elliptical, needle-shaped, or rod-shaped) are desirable, as are fibrous carbon materials.

[0065] When the total negative electrode mixture layer is 100% by mass, the amount of conductive agent in the negative electrode mixture layer can be greater than or equal to about 0.01% by mass and less than or equal to about 5% by mass, greater than or equal to about 0.05% by mass and less than or equal to about 3% by mass, or greater than or equal to about 0.1% by mass and less than or equal to about 1% by mass.

[0066] The negative electrode adhesive in this example embodiment includes three types of adhesives: a first adhesive, a second adhesive, and a third adhesive. These first, second, and third adhesives are different types of adhesives.

[0067] The first binder is not particularly limited and can be or include any reagent capable of bonding the conductive agent to the aforementioned negative electrode active material. Because the first binder is supplied to the surface of the active material in a dissolved or dispersed state in a solvent to form a layer on the surface of the active material that is partially or entirely composed of the binder, it is desirable that the binder is readily soluble or dispersed in the solvent used. From the viewpoint of reducing environmental impact, it is preferable that the first binder be water-soluble. As described above, the first binder is desirable to be soluble or dispersed in a solvent, insoluble in the electrolyte, and possess charge / discharge resistance (the property of not deforming during charging / discharging). Examples of such a first binder can include various binders conventionally used in rechargeable batteries (such as acrylic acid-acrylonitrile copolymer, acrylic acid-sodium styrene sulfonate-acrylonitrile copolymer, carboxymethyl cellulose, or PVDF).

[0068] The first binder bonds the aforementioned conductive agent to the surface of the aforementioned negative electrode active material, causing the conductive agent to extend from the surface of the negative electrode active material in the diametrical direction of the negative electrode active material, thereby forming an active material-conductive agent complex, which is a composite of the negative electrode active material and the conductive agent. As described above, the active material-conductive agent complex has a chestnut shape by arranging the conductive agent to extend outward from the surface of the negative electrode active material.

[0069] When the total negative electrode mixture layer is 100% by mass, the amount of the first binder in the negative electrode mixture layer may be greater than or equal to about 0.001% by mass and less than or equal to about 1% by mass, greater than or equal to about 0.005% by mass and less than or equal to about 0.5% by mass, or greater than or equal to about 0.01% by mass and less than or equal to about 0.1% by mass.

[0070] The second binder is or includes fibrillated binders that form intersecting structures, grids, and / or meshes with each other to provide the negative electrode mixture layer with the mechanical strength required for manufacturing as a self-supporting film. As this second binder, fibrillated binders typically included in electrode mixture layers manufactured by dry processes can be widely used. The second binder includes, for example, fluoropolymers. The fluoropolymers constituting the second binder can be or include, for example, one or more of polytetrafluoroethylene (PTFE), ultra-high molecular weight polyethylene (UHMWPE), and / or other suitable fibrillating materials.

[0071] When the total negative electrode mixture layer is 100% by mass, the amount of the second binder in the negative electrode mixture layer may be greater than or equal to about 0.01% by mass and less than or equal to about 5% by mass, greater than or equal to about 0.05% by mass and less than or equal to about 4% by mass, or greater than or equal to about 0.1% by mass and less than or equal to about 3% by mass.

[0072] It is expected that the amount of the second adhesive is greater than the amount of the first adhesive.

[0073] There are no particular limitations on the third binder, as long as it bonds the components forming the negative electrode mixture layer together. However, it is desirable that the third binder is insoluble in the electrolyte solution, has charge / discharge resistance (the property of not deforming during charging / discharging), and bonds the components together by fusion. From the viewpoint of simplifying the manufacturing process as much as possible, it is desirable that thermal melting and thermal bonding can be performed at the temperatures used in conventional negative electrode manufacturing processes. Examples of such a third binder may include, for example, polyethylene and polyvinylidene fluoride (PVDF). The third binder may be in the form of particles that can be intercalated between the various components to promote the bonding of the various components constituting the negative electrode mixture layer together. For the same reason, it is desirable that the particle size of the third binder be as small as possible, for example, less than or equal to about 1 μm, and as small as possible at the nanoscale.

[0074] When the total negative electrode mixture layer is 100% by mass, the amount of the third binder in the negative electrode mixture layer may be greater than or equal to about 0.01% by mass and less than or equal to about 10% by mass, greater than or equal to about 0.05% by mass and less than or equal to about 6% by mass, or greater than or equal to about 0.1% by mass and less than or equal to about 4% by mass.

[0075] It is desired that the amount of the third adhesive is greater than the amount of the first adhesive.

[0076] The substrate layer is disposed between the negative electrode current collector and the negative electrode mixture layer, and reduces or inhibits the shedding or peeling of the negative electrode mixture layer.

[0077] The matrix layer includes carbon materials, binders, and dispersants for the matrix layer.

[0078] There are no particular limitations on carbon materials, as long as they increase the conductivity of the matrix layer. Examples of carbon materials can include at least one of carbon black, natural graphite, artificial graphite, fibrous carbon, and nanomaterials.

[0079] Examples of carbon black may include at least one of furnace black, channel black, thermal crack black, Ketjen black, and acetylene black.

[0080] Examples of fibrous carbon include carbon fibers.

[0081] Examples of nanomaterials may include at least one of carbon nanotubes, carbon nanofibers, single-layer graphene, and multilayer graphene.

[0082] In carbon materials, the use of easily dispersible carbon black can be advantageous. Among carbon blacks, the use of acetylene black, which has high electrical conductivity, can be advantageous.

[0083] The amount of carbon material in the matrix layer can be greater than or equal to about 1% by mass and less than or equal to about 35% by mass, or greater than or equal to about 5% by mass and less than or equal to about 30% by mass. When the amount of carbon material is greater than or equal to about 1% by mass, the conductivity of the matrix layer is desirable, and when the amount of carbon material is greater than or equal to about 5% by mass, the conductivity of the matrix layer is even more desirable. On the other hand, reducing the amount of carbon material allows for an increase in the amount of binder or dispersant used in the aforementioned matrix layer, which results in the desired adhesion or improved dispersibility of the matrix layer. Therefore, the amount of carbon material can be less than or equal to about 35% by mass, or less than or equal to about 30% by mass.

[0084] The binder for the substrate layer will bond the various components (e.g., carbon materials) in the substrate layer to each other, and will also bond the substrate layer to the negative electrode current collector or negative electrode mixture layer. For example, the binder for the substrate layer according to this example embodiment includes, for example, a styrene-butadiene copolymer (also known as SBR), and may be composed of or include a styrene-butadiene copolymer. A styrene-butadiene copolymer is a copolymer whose main structural units are polymers of styrene and butadiene.

[0085] When the aforementioned substrate layer and the aforementioned negative electrode current collector or negative electrode mixture layer are bonded, adhesive strength can be exhibited due to the softening of the adhesive used in the substrate layer. The softening temperature of the styrene-butadiene copolymer is its glass transition temperature. Typically, the glass transition temperature of styrene-butadiene copolymers is lower than that of fluoropolymers (such as PVDF) (melting point: 177°C), therefore the bonding process temperature can be lowered, which is desirable from the viewpoint of reducing manufacturing costs.

[0086] Styrene-butadiene copolymers can include emulsion-polymerized SBRs and solution-polymerized SBRs. Emulsion-polymerized SBRs can be obtained in the form of an aqueous dispersion (also known as an emulsion or latex). When synthesizing SBRs using emulsion polymerization, emulsifiers are sometimes added. To stabilize the dispersion of SBR particles in water, the SBR particles are sometimes modified in small amounts with monomers (such as unsaturated carboxylic acids or unsaturated nitrile compounds). To stabilize the dispersion of SBR particles in water, surfactants are sometimes added. SBR particles can comprise combinations of heterogeneous polymers. The particles of combined SBRs can have structures such as core-shell or island structures.

[0087] In this example embodiment, an aqueous dispersion of the emulsion-polymerized styrene-butadiene copolymer can be used as a binder for the substrate layer. The styrene-butadiene copolymer has a low viscosity in the aqueous dispersion. The low viscosity of the binder used for the substrate layer can help reduce the viscosity of the slurry used for the substrate layer. The low viscosity of the slurry used for the substrate layer can be advantageous in film coating. The emulsion-polymerized styrene-butadiene copolymer has a relatively large molecular weight, for example, in the range of about 10,000 to about 3,000,000. The larger molecular weight of the binder used for the substrate layer can help increase the strength of the binder used for the substrate layer, and further increase the strength of the substrate layer. A high-strength substrate layer can help reduce the defect rate of the coated film.

[0088] As described above, the aqueous dispersion of styrene-butadiene copolymer may include additives, including emulsifiers and surfactants. Additionally, the aqueous dispersion of styrene-butadiene copolymer may be slightly modified with monomers such as unsaturated carboxylic acids or unsaturated nitrile compounds. Additives or modifications can affect the pH of the aqueous dispersion of styrene-butadiene copolymer.

[0089] When preparing a slurry for the substrate layer by mixing an adhesive for the substrate layer with materials other than the adhesive for the substrate layer, there is a desired pH range for the aqueous dispersion of the adhesive for the substrate layer. For example, when the pH of the materials other than the adhesive for the substrate layer is less than 7, and the adhesive for the substrate layer is not strongly alkaline but close to neutral (preferably neutral or acidic), the formation of agglomerates in the slurry for the substrate layer due to acid-base interactions can be reduced or suppressed. When the formation of agglomerates in the slurry for the substrate layer can be reduced or suppressed, the degradation of coating performance can be reduced or suppressed when coating the slurry for the substrate layer.

[0090] In this example embodiment, polyacrylic acid is used as a dispersant for the matrix layer as described below. The aqueous solution of polyacrylic acid has a pH of less than about 7. To reduce or inhibit the formation of aggregates through the above mechanism, a binder with a pH of about 8 or lower can be used as a binder for the matrix layer.

[0091] The glass transition temperature of the styrene-butadiene copolymer can be less than or equal to about 30°C and greater than or equal to about -30°C. When the styrene-butadiene copolymer is in an environment with a temperature above its glass transition temperature, it softens. Because the styrene-butadiene copolymer softens sufficiently, it exhibits the desired adhesion in the process of adhering the negative electrode mixture layer to the substrate layer. When the glass transition temperature is less than or equal to about 30°C, the desired adhesion is obtained even when the temperature of the hot roll press used to adhere the negative electrode mixture layer to the substrate layer is not too high (e.g., exceeding 120°C). The glass transition temperature of the styrene-butadiene copolymer can be greater than or equal to about -20°C and less than or equal to about 20°C, or greater than or equal to about -15°C and less than or equal to about 15°C.

[0092] When a styrene-butadiene copolymer is immersed in an electrolyte in a dry state, the copolymer absorbs the electrolyte and swells. Excessive swelling can lead to a decrease in the adhesive strength between the electrode mixture layer and the substrate layer. Therefore, a styrene-butadiene copolymer with a swelling degree of less than about 278% by mass is desirable. For example, a desired swelling degree could be less than or equal to about 200% by mass, or less than or equal to about 150% by mass.

[0093] Examples of styrene-butadiene copolymers that satisfy the above properties may include, for example, TRD2001, TRD102A, and TRD104A from ENEOSMaterials Co., Ltd., and BM-451B from Zeon Corporation.

[0094] To sufficiently reduce or prevent detachment or peeling of the electrode mixture layer caused by the substrate layer, the amount of binder in the substrate layer can be greater than or equal to about 50% by mass. Conversely, to sufficiently ensure the conductivity of the substrate layer, the amount of binder in the substrate layer can be less than or equal to about 90% by mass. The amount of binder in the substrate layer can be greater than or equal to about 55% by mass and less than or equal to about 85% by mass, greater than or equal to about 60% by mass and less than or equal to about 85% by mass, or greater than or equal to about 60% by mass and less than or equal to about 80% by mass.

[0095] The dispersant is used to disperse the carbon material and binder used in the matrix layer substantially uniformly, and in this example embodiment, polyacrylic acid corresponds to the dispersant.

[0096] Polyacrylic acid has multiple carboxyl groups in its molecule, which can be neutralized by alkali metal ions such as sodium ions.

[0097] It is desirable that the polyacrylic acid used in this example embodiment has carboxyl groups that are not neutralized as much as possible. For example, the proportion of neutralized carboxyl groups in the polyacrylic acid may be less than or equal to about 20%, less than or equal to about 10%, or may be 0% (i.e., the carboxyl groups of the polyacrylic acid are not neutralized).

[0098] The amount of dispersant in the matrix layer can be greater than or equal to about 1% by mass and less than or equal to about 30% by mass, greater than or equal to about 2% by mass and less than or equal to about 25% by mass, or greater than or equal to about 3% by mass and less than or equal to about 20% by mass. When the amount of dispersant is greater than or equal to about 1% by mass, the aforementioned carbon material and the binder used in the matrix layer can be dispersed substantially uniformly, and when the amount of dispersant is greater than or equal to about 2% by mass, a more uniform dispersion can be obtained. On the other hand, reducing the amount of dispersant allows for an increase in the amount of the aforementioned binder or conductive agent used in the matrix layer, which results in improved battery performance due to the desired adhesion or low resistance of the matrix layer. Therefore, the amount of dispersant can be less than or equal to about 30% by mass, or less than or equal to about 25% by mass.

[0099] 3. A method for manufacturing a non-aqueous electrolyte rechargeable battery according to an example embodiment: The following describes a method for manufacturing a rechargeable lithium-ion battery according to an example embodiment of the present invention.

[0100] 3-1. Manufacturing method of positive electrode: The positive electrode according to this example embodiment is manufactured as follows.

[0101] Positive electrode composite sheets can be manufactured using a dry manufacturing method. In this method, positive electrode active material, conductive agent, and positive electrode binder are mixed in a desired ratio, kneaded to form a positive electrode composite block, and then pressed. The positive electrode can be manufactured by laminating this positive electrode composite sheet onto a positive electrode current collector using a hot roll press or similar method. Furthermore, there are no particular limitations on the manufacturing equipment used in the dry lamination process of the positive electrode composite sheet onto the positive electrode current collector. Considerations for the manufacturing equipment used in this process include roll press equipment, hot roll press equipment, dry laminators, calendering equipment, and hot press equipment.

[0102] Alternatively, a positive electrode slurry can be prepared by dispersing a mixture of materials forming the positive electrode mixture layer in a solvent for the positive electrode slurry, and the positive electrode slurry can be coated onto a positive electrode current collector and dried to form a positive electrode mixture layer.

[0103] 3-2. Manufacturing method of negative electrode: First, the components contained in the aforementioned substrate layer are suspended in a solvent such as water to prepare a substrate layer slurry in a slurry state. This substrate layer slurry is then coated onto the negative electrode current collector and dried to form the substrate layer. Here, the coating amount of the substrate layer slurry is such that the thickness of the dried substrate layer can be, for example, greater than or equal to about 0.5 μm and less than or equal to about 5 μm. The thickness of the dried substrate layer can be greater than or equal to about 0.5 μm and less than or equal to about 2 μm, for example, greater than or equal to about 0.5 μm and less than or equal to about 1.5 μm. On the other hand, there are no particular limitations on the coating method. Coating methods can include blade coating, gravure coating, reverse roll coating, slot die coating, etc. Each of the following coating processes is also performed by the same method.

[0104] Next, a first binder, a negative electrode active material, and a conductive agent dissolved in a solvent such as water are mixed and the mixture is dried to create an active material-conductive agent complex in which the conductive agent is bonded to the surface of the negative electrode active material by the first binder. During the drying process, the conductive agent is dried and fixed in a state where it is arranged like spikes between the negative electrode active material through capillary action.

[0105] The active material-conductive agent composite manufactured in this manner is mixed with a second binder and a third binder in a desired ratio, kneaded to produce a negative electrode mixture block, and then a negative electrode mixture sheet is manufactured by a dry manufacturing method of pressing the negative electrode mixture block. Furthermore, the negative electrode mixture block sheet manufactured in this manner may include not only active materials composited with the conductive agent but also active materials not composited with the conductive agent. The negative electrode is manufactured by a dry method of laminating the negative electrode composite sheet onto a substrate layer using a hot roll press or the like. On the other hand, there are no particular limitations on the manufacturing equipment used in the process of laminating the negative electrode mixture sheet onto the substrate layer using a dry method. As manufacturing equipment used in the process of laminating the negative electrode mixture sheet onto the substrate layer, roll press equipment, hot roll press equipment, dry laminator, calendering equipment, hot press equipment, etc., are all considered. In the above lamination process, for example, when using a hot roller press, the roller temperature of the hot roller press can be appropriately varied depending on the material used for the negative electrode mixture layer, but is expected to be greater than or equal to about 20°C and less than or equal to about 200°C, greater than or equal to about 40°C and less than or equal to about 170°C, or greater than or equal to about 60°C and less than or equal to about 150°C. It is expected that the third binder will be thermally fused during this hot roller pressing.

[0106] 3-3. Manufacturing method of non-aqueous electrolyte rechargeable battery: Next, an electrode structure is fabricated by placing a separator between the positive and negative electrodes. The electrode structure can then be processed into a desired shape (e.g., cylindrical, prismatic, laminated, button-shaped, etc.) and inserted into a container of that shape. Subsequently, a non-aqueous electrolyte is inserted into the corresponding container, causing the electrolyte to permeate each pore in the separator or the gap between the positive and negative electrodes. Thus, a rechargeable lithium-ion battery is manufactured.

[0107] 4. The effect of this example embodiment: According to the non-aqueous electrolyte rechargeable battery constructed as described above, the battery includes an active material (silicon-based active material) with a relatively large volume change of 10% or more during charging and discharging. A negative electrode mixture layer is manufactured by a dry process, such that even in the presence of volume changes in the active material due to charging and discharging, and the creation of gaps between the active materials, a conductive path can be maintained by a conductive agent extending outward from the surface of the negative electrode active material. Therefore, the charge / discharge efficiency of the rechargeable battery can be maintained at a high level.

[0108] 5. Another example embodiment of this disclosure: This disclosure is not limited to the foregoing example embodiments.

[0109] For example, in the above example embodiments, the matrix layer includes a styrene-butadiene copolymer as a binder for the matrix layer, but instead of a styrene-butadiene copolymer, the matrix layer may include a styrene-acrylate copolymer, etc.

[0110] Styrene-acrylate copolymers can refer to copolymers whose structural units are mainly composed of polymerized styrene and acrylate, or include polymerized styrene and acrylate, and can be or include, for example, copolymers containing structural units of styrene and acrylate in a range of greater than or equal to about 80% by mass and less than or equal to about 99% by mass. Acrylates may include at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, isobutyl acrylate, amyl acrylate, n-hexyl acrylate, isoamyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, ethoxy-diethylene glycol acrylate, methoxy-triethylene glycol acrylate, tetrahydrofurfuryl acrylate, phenoxy-polyethylene glycol acrylate, phenoxy-diethylene glycol acrylate, phenoxyethyl acrylate, methoxyethyl acrylate, glycidyl acrylate, and 2-acryloyloxyethyl phosphate, and may include, for example, butyl acrylate and 2-ethylhexyl acrylate.

[0111] Styrene-acrylate copolymers may include structural units other than styrene and acrylate in a range of greater than or equal to about 1% by mass and less than or equal to about 20% by mass.

[0112] The structural units included in styrene-acrylate copolymers may include: at least one of aromatic vinyl compounds (such as p-methylstyrene, m-methylstyrene, o-methylstyrene, o-tert-butylstyrene, m-tert-butylstyrene, p-tert-butylstyrene, p-chlorostyrene, and o-chlorostyrene), unsaturated alkyl methacrylate compounds (such as at least one of methyl methacrylate, ethyl methacrylate, butyl methacrylate, isopropyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isobutyl methacrylate, amyl methacrylate, n-hexyl methacrylate, isoamyl methacrylate, lauryl methacrylate, stearyl methacrylate, and isobornyl methacrylate), (meth)acrylic acid compounds (such as at least one of methacrylic acid, acrylic acid, itaconic acid, fumaric acid, and maleic acid), and unsaturated carboxylic acid amide compounds. Structural units obtained by polymerization of at least one of (meth)acrylamide, N-methyl (meth)acrylamide, N-dimethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and N-isobutoxymethyl (meth)acrylamide; and structural units obtained by polymerization of at least one of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, diethylene glycol ethoxymethacrylate, methoxytriethylene glycol methacrylate, tetrahydrofurfuryl methacrylate, phenoxy-polyethylene glycol methacrylate, phenoxydiethylene glycol methacrylate, phenoxyethyl methacrylate, methoxyethyl methacrylate, glycidyl methacrylate, methacrylonitrile, and 2-methacryloyloxyethyl phosphate.

[0113] The glass transition temperature of styrene-acrylate copolymers can be less than or equal to about 20°C and greater than or equal to about -20°C. When the glass transition temperature is within this range, the desired adhesion can be obtained even if the temperature of the hot roll press used to adhere the negative electrode mixture layer to the substrate layer is not set too high (e.g., exceeding about 120°C). The glass transition temperature of styrene-acrylate copolymers can be greater than or equal to about -15°C and less than or equal to about 15°C, for example, greater than or equal to about -10°C and less than or equal to about 15°C.

[0114] The glass transition temperature of styrene-acrylate copolymers can be adjusted according to the type and content of the structural units. Because styrene-acrylate copolymers comprise structural units of greater than or equal to about 80% by mass and less than or equal to about 99% by mass, obtained by polymerizing styrene and acrylate, the content of styrene and acrylate can be adjusted. For example, since the glass transition temperature of styrene homopolymer is about 100°C and the glass transition temperature of 2-ethylhexyl acrylate homopolymer is about -55°C, by adjusting the content of styrene and 2-ethylhexyl acrylate, styrene-acrylate copolymers with a glass transition temperature between about -55°C and about 100°C can be synthesized. In addition, when the glass transition temperature of the homopolymer of the monomers used is known, the glass transition temperature can be calculated from the volume fraction of these monomer compounds using the Fox equation. Furthermore, by synthesizing styrene-acrylate copolymers as described above and performing differential scanning calorimetry (DSC), styrene-acrylate copolymers with glass transition temperatures greater than or equal to about -20°C and less than or equal to about 20°C can be obtained.

[0115] In the above example embodiments, a negative electrode has been described, but a positive electrode having the same structure as an electrode mixture layer or substrate layer is also feasible.

[0116] In addition, positive or negative electrodes can be formed without a substrate layer (adhesive layer), and a positive or negative electrode mixture layer can be formed directly on the positive or negative electrode current collector.

[0117] The electrodes according to the example embodiments are not limited to non-aqueous electrolyte rechargeable batteries, and can generally be applied to rechargeable batteries, such as semi-solid rechargeable batteries or all-solid rechargeable batteries with a solid electrolyte layer.

[0118] Furthermore, this disclosure is not limited to these exemplary embodiments, and various modifications are of course possible without departing from its spirit.

[0119] Example: The present disclosure is described in more detail below with reference to the following examples. However, the following examples are merely illustrative of the present disclosure, and the present disclosure is not limited thereto.

[0120] Example 1: Preparation of chestnut-spiky silicon-based active material (S1): Silicon-based active material and carbon nanotubes (SWCNTs) were added to an aqueous solution of carboxymethyl cellulose (CMC) as the first binder, with 0.75 parts by mass of SWCNTs added to 100 parts by mass of the silicon-based active material, and the mixture was stirred. A solid was then obtained by drying in air at 103°C and further in a vacuum at 80°C for 6 hours. The obtained solid was pulverized using a mortar to obtain a powdered active material-conductive agent composite (S1) (also known as chestnut-shaped silicon-based active material (S1)).

[0121] Fabrication of the dry negative electrode sheet (D1): A silicon-based active material (S1) in the shape of chestnut spiky fibers, a carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder are mixed in a mass ratio of 4:94:1:1, stretched into a sheet shape, and pressed into contact with a substrate layer formed on a negative electrode current collector made of 10 μm thick copper foil to obtain a dry negative electrode sheet (D1). In the example and comparative examples, the mass ratio of S1 is calculated using the mass of the silicon-based active material used as the starting material. The substrate layer comprises styrene-butadiene copolymer, acetylene black, and polyacrylic acid in a mass ratio of 60:28:12.

[0122] Example 2: Silicon-based active material and carbon nanotubes (SWCNTs) were added to an aqueous solution of CMC, which served as the first binder, at a ratio of 2.25 parts by mass of SWCNTs to 100 parts by mass of silicon-based active material, and the mixture was stirred. A solid was then obtained by drying in air at 103°C and further in a vacuum at 80°C for 6 hours. The obtained solid was pulverized using a mortar to obtain a powdered active material-conductive agent composite (S2) (also known as chestnut-spiky silicon-based active material (S2)).

[0123] Fabrication of the dry negative electrode sheet (D2): A chestnut-shaped silicon-based active material (S2), a carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder are mixed in a ratio of 4:94:1:1 (mass ratio), stretched into a sheet shape, and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D2).

[0124] Example 3: A silicon-based active material and single-walled carbon nanotubes (SWCNTs) as a conductive agent were added to an aqueous solution of CMC, which served as the first binder, at a ratio of 0.25 parts by mass of SWCNTs to 100 parts by mass of the silicon-based active material, and the mixture was stirred. A solid was then obtained by drying in air at 103°C and further in a vacuum at 80°C for 6 hours. The obtained solid was pulverized using a mortar to obtain a powdered active material-conductive agent composite (S3), also known as chestnut-shaped silicon-based active material (S3).

[0125] Fabrication of the dry negative electrode sheet (D3): A chestnut-shaped silicon-based active material (S3), a carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder are mixed in a ratio of 4:94:1:1 (mass ratio), stretched into a sheet shape, and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D3).

[0126] Example 4: A silicon-based active material and carbon nanotubes (SWCNTs) as a first binder were added to an NMP solution of PVDF at a ratio of 0.25 parts by mass of SWCNTs to 100 parts by mass of the silicon-based active material, and the mixture was stirred. A solid was then obtained by drying in air at 120°C and further in a vacuum at 120°C for 6 hours. The obtained solid was pulverized using a mortar to obtain a powdered active material-conductive agent composite (S4), also known as chestnut-shaped silicon-based active material (S4).

[0127] Fabrication of the dry negative electrode sheet (D4): A mixture of chestnut-hair-like silicon-based active material (S4), carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder in a ratio of 4:94:1:1 (mass ratio) is stretched into a sheet shape and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D4).

[0128] Example 5: Fabrication of the dry negative electrode sheet (D5): A chestnut-shaped silicon-based active material (S1), a carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder are mixed in a ratio of 4:94:0.5:1 (mass ratio), stretched into a sheet shape, and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D5).

[0129] Example 6: Fabrication of the dry negative electrode sheet (D6): A mixture of chestnut-shaped silicon-based active material (S1), carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder in a ratio of 4:94:0.5:2 (mass ratio) is stretched into a sheet shape and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D6).

[0130] Example 7: Fabrication of the dry negative electrode sheet (D7): A chestnut-shaped silicon-based active material (S1), a carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder are mixed in a ratio of 4:94:0.3:1 (mass ratio), stretched into a sheet shape, and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D7).

[0131] Example 8: Manufacturing of the dry negative electrode sheet (D8): A chestnut-shaped silicon-based active material (S1), a carbon-based negative electrode active material, fibrillated PTFE as a second binder, and particulate PVDF as a third binder are mixed in a ratio of 4:94:0.3:2 (mass ratio), stretched into a sheet shape, and pressed onto a 10μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (D8).

[0132] Compare with Example 1: Fabrication of the dry negative electrode sheet (R1): Untreated silicon-based active material (S0), carbon-based negative electrode active material, conductive agent, and fibrillated PTFE as a second binder were mixed in a ratio of 4:94:0.03:1 (mass ratio), stretched into a sheet shape, and pressed onto a 10 μm thick copper foil negative electrode current collector to obtain a dry negative electrode sheet (R1). The components of Examples 1 to 8 and Comparative Example 1 are summarized in Table 1 below.

[0133] Table 1:

[0134] Manufacturing of the half-cell used for testing: Dry negative electrode sheets (D1 to D7) or dry negative electrode sheet (R1) are laminated with lithium metal foil through a separator, sandwiched in an aluminum laminate. The edges of the aluminum laminate, except for a portion, are thermally welded. After electrolyte injection, all edges are thermally welded and sealed in a vacuum to manufacture a half-cell for testing. A portion of each of the lithium metal foil and the negative electrode is designed to protrude from the laminate to avoid disrupting the battery vacuum; the protruding portion serves as a terminal.

[0135] Evaluation of the half-cell used for testing: The charge / discharge characteristics of the half-cell manufactured in this manner were evaluated under the following conditions. Measurements were performed by placing the half-cell in a constant-temperature bath at 25°C. A predetermined pressure was applied to the electrode surface by clamping the half-cell between two resin plates and inserting a clamp between the plates. The battery was charged at 0.7 mA / cm². 2 Charged with a constant current for 15 hours, then at 0.7 mA / cm². 2 The battery was discharged at a constant current until the battery voltage reached 1.5V. This was repeated twice, and the charge / discharge capacity ratio (discharge capacity / charge capacity) and electrode plate expansion % (thickness of the electrode mixture layer after charging / thickness before charging) were compared between the first and second discharges. The results are shown in Table 2 below.

[0136] Manufacturing of the full-cell unit used for testing: Each of the dry negative electrode sheets (D1 to D7) or dry negative electrode sheet (R1) is laminated with the positive electrode through a separator, sandwiched in an aluminum laminate, with all but a portion of the aluminum laminate's edges thermally welded. After electrolyte injection, all edges are thermally welded and sealed in a vacuum to manufacture a full cell for testing. A portion of each of the positive and negative electrodes is designed to protrude from the laminate to avoid disrupting the cell's vacuum, and these protrusions are designated as the positive electrode terminal and the negative electrode terminal, respectively.

[0137] Evaluation of the full-cell unit used for testing: Full cell cells using negative electrodes fabricated in Examples 1 to 8 and Comparative Example 1 were charged to 4.25V at a constant current with a design capacity of 0.5CA in a constant-temperature bath at 25°C, and then charged at a constant voltage at 4.25V until the voltage became 0.05CA. The initial discharge capacity was then obtained by discharging to 2.8V at a constant current of 0.5CA. Cycle life testing was performed under the same conditions for 100 cycles. The capacity retention after 100 cycles was measured by dividing the discharge capacity after 100 cycles by the initial discharge capacity. The results are shown in Table 2 below.

[0138] Table 2:

[0139] According to the results in Table 2 above, when a negative electrode mixture layer is manufactured by dry process, the negative electrode mixture layer comprising a chestnut-shaped active material-conductive agent complex, in which the conductive agent is bonded to the surface of the active material by a first binder so as to extend in the diametrical direction of the active material, can maintain a significantly high charge-discharge capacity ratio and significantly reduce or suppress the expansion rate of the electrode plate.

[0140] While this disclosure has been described in conjunction with what are now considered to be exemplary embodiments, it will be understood that the disclosure is not limited to the disclosed exemplary embodiments. Rather, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An active substance-conductive agent complex, said active substance-conductive agent complex comprising: Active material, capable of inserting and de-intercalating lithium; Conductive agent; as well as The first adhesive binds the active material and the conductive agent together. in: The active substance is in the form of spherical particles, and The conductive agent is bonded to the surface of the active material by the first adhesive to elongate in the diametrical direction of the active material.

2. The active substance-conductive agent composite according to claim 1, wherein, The conductive agent is in fibrous form.

3. The active substance-conductive agent composite according to claim 1, wherein, The active material includes silicon-based active materials.

4. An electrode for a rechargeable battery, the electrode comprising: The active substance-conductive agent complex according to any one of claims 1 to 3; The second adhesive is a different adhesive from the first adhesive; as well as The third adhesive may be the same as or different from the first adhesive. The second adhesive is in the form of fibrils, including fluoropolymers.

5. The electrode according to claim 4, wherein, The second and third adhesives bond the plurality of active material-conductive agent complexes together.

6. The electrode according to claim 4, wherein: The electrode includes a current collector, an electrode mixture layer, and a conductive adhesive layer between the current collector and the electrode mixture layer. The electrode mixture layer includes the active material-conductive agent complex, the second binder, and the third binder.

7. The electrode according to claim 6, wherein: The conductive adhesive layer comprises a carbon material, an adhesive for the substrate layer, and a dispersant, and The adhesive used for the substrate layer includes styrene-butadiene copolymers or styrene-acrylate copolymers.

8. A rechargeable battery, said rechargeable battery comprising: Positive and negative electrodes The negative electrode comprises the electrode according to any one of claims 4 to 7.

9. A non-aqueous electrolyte rechargeable battery, said non-aqueous electrolyte rechargeable battery comprising: Positive and negative electrodes The negative electrode comprises the electrode according to any one of claims 4 to 7.

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