Electrode, method for manufacturing electrode, and electrochemical device

Abstract

An electrode which contains an active material and a current collector having a three-dimensional porous structure, and which satisfies either or both of the following conditions (i) and (ii). (i) When the average opening diameter of the current collector is A ([mu] m) and the median diameter (D50) of the active material is B ([mu] m), A and B satisfy the relationship represented by formula (1). 0.10 < = B / A < = 2.00 (1) (ii) The current collector is filled with an active material component containing an active material, and the filling rate (%) defined by formula (2) is 37% or more. Filling rate (%) = [beta] / ([alpha]-[gamma]) * 100 (2) In the formula, [alpha] represents an observed area of the current collector obtained from an electron microscope photograph of a cross section in the electrode thickness direction, and [beta] and [gamma] respectively represent projected areas of the active material and the current collector calculated by image analysis software within the observed area.

Description

[0001] Related applications This application claims priority to Japanese Patent Application No. 2023-056012 filed in Japan on March 30, 2023 and Japanese Patent Application No. 2023-137490 filed in Japan on August 25, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to electrodes useful for electrochemical devices, methods for manufacturing the same, and electrochemical devices. Background Technology

[0003] In recent years, with the widespread adoption of small devices such as smartphones and laptops, as well as electric and hybrid vehicles, various electrochemical devices have been developed. Among them, the use of non-aqueous electrolyte secondary batteries, represented by lithium-ion secondary batteries, is expanding, with advancements in miniaturization and lightweighting for automotive applications and other uses.

[0004] For example, Patent Document 1 (International Publication No. 2022 / 118692) discloses an electrode using a current collector, which is a conductor with a three-dimensional porous structure and an air permeability of 0.1 to 600 cc / cm. 2 The electrode has a thickness of less than 100 μm and a thickness that can be reduced by a factor of 100. This electrode allows for a reduction in thickness, significantly lowers electrode resistance, and achieves good charge-discharge characteristics.

[0005] Existing technical documents Patent documents Patent document 1: International Publication No. 2022 / 118692. Summary of the Invention

[0006] The problem that the invention aims to solve However, although Patent Document 1 describes controlling the permeability of the current collector and making the current collector thinner to reduce the resistance of the electrode from the viewpoint of improving the fluid permeability of the electrolyte, there is still room for improvement in the current collector, especially the current collector with a three-dimensional porous structure, to obtain practical output performance.

[0007] In view of the above-mentioned problems, the object of the present invention is to provide an electrode that can improve the capacity retention of electrochemical devices.

[0008] Problem-solving methods The inventors conducted repeated and in-depth research and found that the above-mentioned problems could be solved by constructing electrodes with the following structure. Based on this insight, they conducted further repeated research and thus completed the present invention.

[0009] That is, the present invention may include the following methods.

[0010] [Method 1] An electrode comprising a current collector and an active material, wherein the current collector has a three-dimensional porous structure with an average opening diameter A, and the active material has a median diameter (D). 50 B, the aforementioned average opening diameter A (μm) and the aforementioned median diameter (D) 50 B(μm) satisfies the following relationship (1), 0.10≤B / A≤2.00 (1) (B / A is preferably 0.13 or more, more preferably 0.15 or more, preferably 1.96 or less, more preferably 1.70 or less, even more preferably 1.50 or less, and particularly preferably 1.20 or less).

[0011] [Method 2] The electrode according to Method 1, wherein the aforementioned current collector is filled with an active material component containing the aforementioned active material, and the filling rate (%) specified by the following formula (2) is 37% or more. Fill rate (%) = β / (α-γ) × 100 (2) In the formula, α represents the observation area, which is determined by the thickness of the current collector × the observation length, based on the electron microscope image (SEM image) of the cross section in the electrode thickness direction. β and γ represent the projected areas of the active material and the current collector (the solid phase part of the current collector) within the observation area, respectively, calculated using image analysis software.

[0012] [Method 3] An electrode having a current collector having a three-dimensional porous structure, wherein the current collector is filled with an active material component containing an active material, and the filling rate (%) specified in the following formula (2) is 37% or more (preferably 45% or more). Fill rate (%) = β / (α-γ) × 100 (2) In the formula, α represents the observation area, which is determined by the thickness of the current collector × the observation length, based on an electron microscope photograph of the cross-section in the electrode thickness direction. β and γ represent the projected areas of the active material and the current collector (the solid phase part of the current collector) within the observation area, respectively, calculated using image analysis software.

[0013] [Method 4] The electrode according to Method 3, wherein the aforementioned current collector has an average opening diameter A, and the aforementioned active material has a median diameter (D). 50 B, the aforementioned average opening diameter A (μm) and the aforementioned median diameter (D) 50 B(μm) satisfies the following relationship (1), 0.10≤B / A≤2.00 (1) (B / A is preferably 0.13 or more, more preferably 0.15 or more, preferably 1.96 or less, more preferably 1.70 or less, even more preferably 1.50 or less, and particularly preferably 1.20 or less).

[0014] [Method 5] The electrode according to any one of Methods 1 to 4, wherein the thickness of the aforementioned current collector is less than 100 μm (e.g., 5 to 80 μm, more preferably 5 to 60 μm, further preferably 5 to 45 μm, particularly preferably 10 to 30 μm).

[0015] [Method 6] An electrode according to any one of Methods 1 to 5, wherein the air permeability of the aforementioned current collector is 0.1~600 cc / cm 2 / second (preferably 1cc / cm) 2 / second or higher, more preferably 10cc / cm 2 / second or higher, and preferably 500cc / cm 2 / second or less, more preferably 400cc / cm 2 (less than / second).

[0016] [Method 7] An electrode according to any one of Methods 1 to 6, wherein the aforementioned current collector comprises a non-conductive structure and a metal coating.

[0017] [Method 8] The electrode according to Method 7, wherein the aforementioned non-conductive structure comprises a fiber aggregate with an average fiber diameter of 10 μm or less.

[0018] [Method 9] The electrode according to Method 8, wherein the aforementioned fiber assembly is a nonwoven fabric.

[0019] [Method 10] An electrode according to any one of Methods 7 to 9, wherein the aforementioned metal coating comprises at least one metal selected from aluminum, copper, nickel, gold, and silver.

[0020] [Method 11] An electrode according to any one of Methods 1 to 10, wherein the aforementioned active material can absorb and release electrolyte ions.

[0021] [Method 12] An electrode according to any one of Methods 1 to 11, wherein the electrode further comprises a conductive material.

[0022] [Method 13] An electrode according to any one of Methods 1 to 12, wherein the median diameter of the aforementioned active material is 0.1 to 100 μm, for example, 0.1 to 16 μm.

[0023] [Method 14] An electrode according to any one of Methods 1 to 13, wherein the aforementioned current collector is filled with an active material component comprising an active material and a non-water-soluble binder.

[0024] [Method 15] A method for manufacturing an electrode according to any one of Methods 1 to 14, comprising at least: a step of preparing a current collector having a three-dimensional porous structure with an average opening diameter A, and... For the process of forming an active material layer containing an active material with a median diameter B in the aforementioned current collector, the aforementioned average opening diameter A and the aforementioned median diameter B satisfy the following formula (1).

[0025] 0.10≤B / A≤2.00 (1) (B / A is preferably 0.13 or more, more preferably 0.15 or more, preferably 1.96 or less, more preferably 1.70 or less, even more preferably 1.50 or less, and particularly preferably 1.20 or less) [Method 16] The method for manufacturing an electrode according to any one of Methods 1 to 14 includes at least a step of filling a current collector having a three-dimensional porous structure with an active material component.

[0026] [Method 17] The electrode manufacturing method according to Method 16, wherein the air permeability of the aforementioned current collector before filling with the active material component is 0.1~600cc / cm 2 / Second.

[0027] [Method 18] The electrode manufacturing method according to Method 16 or 17, wherein the thickness of the aforementioned current collector before filling with the active material component is 100 μm or less.

[0028] [Model 19] An electrochemical device comprising an electrode as described in any one of Models 1 to 14.

[0029] It should be noted that any combination of at least two constituent elements disclosed in the claims and / or specification is included in this invention. In particular, any combination of two or more claims recited in the claims is also included in this invention.

[0030] Invention Effects The electrode according to the present invention can improve the capacity retention of an electrochemical device equipped with the electrode. Attached Figure Description

[0031] The invention will be more clearly understood from the following description of suitable embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims.

[0032] [ Figure 1 [Image 1] is a microscope photograph (200x magnification) illustrating the method for measuring the average opening diameter of the current collector according to the first embodiment of the present invention.

[0033] [ Figure 2 [Image 1] is a scanning electron microscope image (2000x) of the electrode cross section used to illustrate the electrode filling rate determination method of the second embodiment of the present invention.

[0034] [ Figure 3 [ is used for explanation] Figure 2 A schematic diagram of the current collector and active material locations within the observation area in a scanning electron microscope image.

[0035] [ Figure 4 [Illustration 1] is a schematic cross-sectional view showing an example of the structure of an electrochemical device. Detailed Implementation

[0036] The electrode of the present invention is a current collector having a three-dimensional porous structure and an electrode containing an active material, and is an electrode that satisfies any one or both of the following conditions (i) and (ii).

[0037] (i) When the average opening diameter of the current collector is A (μm) and the median diameter of the active material is D 50 When A is B (μm), A and B satisfy the following relationship (1).

[0038] 0.10≤B / A≤2.00 (1) (ii) The current collector is filled with an active material component containing an active material, and the filling rate (%) specified in the following formula (2) is 37% or more.

[0039] Filling rate (%) = β / (α-γ) × 100 (2) In the formula, α represents the observation area of ​​the current collector obtained from the electron microscope image (SEM image) of the cross section in the electrode thickness direction, and β and γ represent the projected areas of the active material and the current collector (the solid phase part of the current collector) within the observation area calculated by image analysis software, respectively.

[0040] The electrode of this invention is suitable as an electrode for electrochemical devices. These electrochemical devices include secondary batteries such as lithium-ion batteries, nickel-metal hydride batteries, and nickel-cadmium batteries, as well as capacitors such as double-layer capacitors. Specifically, the electrochemical device can be a non-aqueous electrolyte secondary battery (e.g., lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-air batteries, all-solid-state batteries, organic radical batteries, etc.), and is more preferably a lithium-ion secondary battery.

[0041] The following explanation uses an electrode for a non-aqueous electrolyte secondary battery as an example.

[0042] Implementation Method 1 [Current Collector] A current collector is a conductor with a three-dimensional porous structure (hereinafter sometimes referred to as a three-dimensional porous structure or simply a porous structure). Here, a three-dimensional porous structure refers to a porous structure with voids distributed in three-dimensional space. The current collector has an average opening diameter A, which is obtained by averaging the opening diameters of the multiple openings formed by the porous structure.

[0043] (Three-dimensional porous structure) To achieve a three-dimensional porous structure, the current collector can be constructed using fibrous structures (fiber aggregates) such as fabrics / nonwovens (including paper), or resin foams such as foamed urethane. There is no limitation on the method used to obtain a conductor with a porous structure; the porous conductor can also be formed using known conductive raw materials used in electrodes. The porous conductor can also take the shape of a nonwoven fabric.

[0044] In addition, when a conductive body with a three-dimensional porous composite structure includes a non-conductive structure and a metal coating formed on the non-conductive structure, the non-conductive structure is not particularly limited and can be a known resin foam or a fibrous structure containing non-conductive fibers (such as fabric or non-woven fabric).

[0045] Figure 1 This is a microscopic photograph illustrating a method for measuring the average opening diameter of a current collector, used to illustrate one aspect of the present invention. In a three-dimensional porous structure, firstly, a sample is cut out in a predetermined shape along the planar direction of the current collector. Considering the intrusion of active materials into the current collector, a portion from the surface of the current collector to a predetermined depth (e.g., less than 100 μm) along the thickness direction can be peeled off and measured, but generally, the thickness of the current collector itself can also be measured. Then, a magnified photograph taken on a substrate (e.g., a black plate) can be obtained from the cut sample.

[0046] by Figure 1 Let's take an example to illustrate. Figure 1 This is a magnified photograph of a sample placed on a black-backed flat plate after being clamped and fixed in place by a glass slide. As shown in the photograph, the fibrous materials constituting the sample overlap each other in the depth (thickness) direction. On the other hand, there is no space for the fibrous material, i.e., the space of the base portion can be identified, which can function as a through-hole in the depth direction. In this case, for the average opening diameter of the current collector, since the space of the base portion surrounded by the fibrous material is regarded as a through-hole, the diameter of the circle with the area determined by the image can be calculated based on the area of ​​each through-hole, and the average of the diameters of each through-hole is regarded as the average opening diameter.

[0047] The number of through holes measured is appropriately determined based on the size of the through holes in the sample. If large through holes are present in the photograph, the number of through holes used in the measurement is reduced. Typically, an average value is calculated using 500 to 5000 through holes.

[0048] It should be noted that, from the perspective of reducing measurement errors, the area of ​​the through hole can also be taken as 2μm. 2 The above area represents the average area of ​​the through holes observed.

[0049] Furthermore, when the current collector is a fiber structure, the fiber itself may emit black light and appear black, depending on the circumstances. In this case, to distinguish between the black light portion of the fiber and the through-hole that can be identified by the black color of the plate against a black background, the area of ​​a square with a side length of 0.5 times the average fiber diameter can be used as a threshold, and the area of ​​the black portion larger than this threshold can be used as the area of ​​the through-hole.

[0050] For example, when the average fiber diameter of the fibers constituting the fiber structure is 4 μm, a 4 μm fiber with an area equivalent to a square with one side of 2 μm can be used. 2 The above area represents the average area of ​​the through holes observed.

[0051] It should be noted that when measuring the image of a magnified photograph, binarization is preferred. For example, by using image analysis software (such as the "Multi-File Analysis Application" manufactured by Keynes Co., Ltd.), the settings are configured to distinguish between black parts and other parts, thereby utilizing the binarized image.

[0052] Preferably, from the viewpoint of improving the permeability of the electrolyte, the air permeability of the current collector can be 0.1 to 600 cc / cm. 2 / second. Since a correlation is considered to exist between the permeability of the current collector and the permeability of the electrolyte, high permeability of the current collector can improve electrolyte permeability, ensuring ionic conductivity and consequently reducing electrode resistance. Conversely, low permeability of the current collector can improve the mechanical strength of the porous structure, thereby enhancing the durability of the current collector and the stability of electrode manufacturing.

[0053] The air permeability of the current collector is preferably 0.1 cc / cm. 2 / second or higher, preferably 1cc / cm 2 / second or higher, further preferably 10cc / cm 2 / second or higher. On the other hand, the air permeability of the current collector is preferably 600cc / cm. 2 Below / second, preferably 500cc / cm 2 Below / second, further preferably 400cc / cm 2 / second or less.

[0054] For example, the air permeability of the current collector can be 0.1–600 cc / cm. 2 / second, preferably 1~500cc / cm 2 / second, further preferably 10~400cc / cm 2 / Second.

[0055] Here, the air permeability of the current collector can be measured using the method described in the examples below. It should be noted that when measuring the current collector disposed inside the electrode, the air permeability can be measured on the current collector after the active material components in the current collector have been removed with a solvent or the like.

[0056] Furthermore, the thickness of the current collector can be 100 μm or less. With such a thin current collector, a battery with a high charge / discharge capacity per unit volume can be obtained. Therefore, the current collector thickness is preferably 80 μm or less, more preferably 60 μm or less, even more preferably 45 μm or less, further preferably 40 μm or less, and most preferably 30 μm or less. While there is no particular limitation on the lower limit of the current collector thickness, it is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of avoiding breakage during battery manufacturing and handling. For example, the current collector thickness can preferably be 5–80 μm, more preferably 5–60 μm, further preferably 5–45 μm, and particularly preferably 10–30 μm.

[0057] Here, the thickness of the current collector can be determined, for example, by taking a scanning electron microscope image (SEM image) of a cross-section of the electrode in the thickness direction, specifically by the method described in the embodiments below.

[0058] The weight per unit area of ​​the current collector can range from 1.0 to 50 g / m². 2 The smaller the weight per unit area of ​​the current collector, the better the air permeability and the thinner the current collector can be. Therefore, 15 g / m² is preferred. 2 The following is more preferably 12g / m 2 The following is a further preferred value: 10 g / m 2 Below. Furthermore, from the viewpoint of the mechanical strength of the current collector, a higher weight per unit area is preferred, preferably 1.0 g / m². 2 The above, and more preferably 2.0 g / m 2 The above is further preferred to be 3.0 g / m 2 Therefore, the preferred weight per unit area of ​​the current collector is 1.0~30 g / m². 2 The concentration can be more preferably 1.0~20g / m 2 It can be further optimized to be 1.0~15g / m 2It can be particularly preferred to be 2.0~12g / m 2 It should be noted that the preferred concentration is 3.0~10g / m³. 2 .

[0059] Metal coatings can be formed on non-conductive porous structures (hereinafter sometimes referred to as non-conductive porous structures) by methods such as plating and composite formation, thereby imparting conductivity to the non-conductive porous structures.

[0060] When a conductive body with a three-dimensional porous composite structure comprises a non-conductive structure and a metal coating, the non-conductive structure is not particularly limited and can be a known resin foam or a fibrous structure containing non-conductive fibers. Preferably, the conductive body serving as a current collector is a conductive body with a three-dimensional porous composite structure obtained by forming a metal coating on a non-conductive porous structure (especially a non-conductive fibrous structure) and then compositing it.

[0061] Examples of non-conductive fibers include polyolefin fibers, cellulose fibers, (meth)acrylic fibers, polyvinyl alcohol fibers, vinyl chloride fibers, styrene fibers, polyester fibers, polyamide fibers, polycarbonate fibers, and urethane fibers. Among these fibers, from the viewpoint of exhibiting the aforementioned strength, polyester fibers such as polyethylene terephthalate fibers, polybutylene terephthalate fibers, polypropylene terephthalate fibers, and melt-liquid crystal-forming aromatic polyester fibers are preferred. Of these, melt-liquid crystal-forming aromatic polyester fibers (e.g., melt-liquid crystal-forming fully aromatic polyester fibers) are particularly preferred.

[0062] Melt-liquid-forming aromatic polyesters, particularly melt-liquid-forming fully aromatic polyesters, constituting the aforementioned melt-liquid-forming aromatic polyester fibers, are resins with excellent heat resistance and chemical resistance. In this specification, melt-liquid-forming property refers to the property of exhibiting optical anisotropy (liquidity) in the molten phase; melt-liquid-forming aromatic polyesters refer to polyesters exhibiting melt-liquid-forming properties. "Melt-liquid-forming property" can be determined, for example, by placing a sample on a hot stage, heating it in a nitrogen atmosphere, and observing the transmitted light of the sample. Melt-liquid-forming aromatic polyesters contain repeating constituent units, such as those from aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids. The chemical composition of the constituent units from aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids is not particularly limited, provided it does not impair the effects of the present invention. Furthermore, within the scope of not impairing the effects of the present invention, melt-liquid-forming aromatic polyesters may contain constituent units from aromatic diamines, aromatic hydroxylamines, or aromatic aminocarboxylic acids. For example, examples shown in Table 1 can be cited as preferred constituent units.

[0063] [Table 1] (Where, X in the formula is selected from the following structure) (Where, m = 0 to 2, Y = substituents selected from hydrogen, halogen atom, alkyl, aryl, aralkyl, alkoxy, aryloxy, and arylalkoxy) Y is a substituent that can be substituted within the range of 1 to the maximum number of substituents in an aromatic ring or cyclic ring. Specifically, it is a substituent selected from hydrogen atom, halogen atom (e.g., fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl (e.g., alkyl with 1 to 4 carbon atoms such as methyl, ethyl, isopropyl, tert-butyl, etc.), alkoxy (e.g., methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl (e.g., phenyl, naphthyl, etc.), aralkyl [benzyl (phenylmethyl), phenethyl (phenylethyl) etc.], aryloxy (e.g., phenoxy, etc.) and arylalkoxy (e.g., benzyloxy, etc.).

[0064] As a more preferred constituent unit, examples (1) to (18) shown in Tables 2, 3 and 4 below can be cited. It should be noted that when the constituent unit in the formula is a constituent unit that can represent multiple structures, two or more such constituent units can be combined and used as constituent units constituting the polymer.

[0065] [Table 2] [Table 3] [Table 4] In the constituent units of Tables 2, 3, and 4, n is an integer of 1 or 2. Each constituent unit n=1 and n=2 can exist alone or in combination. Y1 and Y2 can be independently hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.), alkyl groups (e.g., methyl, ethyl, isopropyl, tert-butyl, etc., with 1 to 4 carbon atoms), alkoxy groups (e.g., methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl groups (e.g., phenyl, naphthyl, etc.), aralkyl groups [benzyl (phenylmethyl), phenethyl (phenylethyl), etc.], aryloxy groups (e.g., phenoxy, etc.), arylalkoxy groups (e.g., benzyloxy, etc.). Among these, hydrogen atoms, chlorine atoms, bromine atoms, or methyl groups are preferred for Y1 and Y2.

[0066] In addition, Z can be represented by the substituents shown in the following formula.

[0067] [Chemistry 1] The melt-liquid crystal forming fully aromatic polyester used in this invention is preferably composed of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid as the main components, or composed of p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid and biphenol as the main components.

[0068] Nonwoven fabrics comprising molten liquid crystal forming aromatic polyesters are preferably meltblown nonwoven fabrics obtained by meltblowing. The meltblowing method can employ known methods, for example, the following: molten molten liquid crystal forming aromatic polyester is extruded as molten polymer from a plurality of nozzles arranged in a row; high-temperature, high-speed air is ejected from a gas injection port located adjacent to the nozzle head; the extruded molten polymer is then finely fibrous; and the fiber stream is then collected on a conveyor belt serving as a collector to manufacture the nonwoven fabric. To impart heat resistance, the obtained nonwoven fabric can also be heat-treated. The preferred heating temperature is above <melting point of the molten liquid crystal forming aromatic polyester -40°C> and below <melting point of the molten liquid crystal forming aromatic polyester +20°C>, and the heat treatment is preferably performed for 3 hours or more. Examples of gases used as the heating medium during heat treatment include mixtures of nitrogen, oxygen, argon, carbon dioxide, or air; from a cost perspective, oxygen or air is more preferred. The heat treatment can be performed under tension or without tension, depending on the purpose.

[0069] As a melt-liquid crystal-forming aromatic polyester, a melt viscosity of 20 Pa·s or less at 310°C is preferred. If the melt viscosity at 310°C exceeds 20 Pa·s, it is difficult to achieve ultra-fine fiberization, which is not preferred due to reasons such as oligomer formation during polymerization and adverse conditions during polymerization and granulation. On the other hand, it is also difficult to achieve fiberization if the melt viscosity is too low, and it is desirable to exhibit a melt viscosity of 5 Pa·s or more at 310°C. The melt viscosity of this melt-liquid crystal-forming aromatic polyester at 310°C refers, for example, to the value obtained by measuring using a melt indexer (manufactured by Takara Kogyo Co., Ltd.: L244).

[0070] It should be noted that, as needed, colorants, inorganic fillers, antioxidants, UV absorbers, and other commonly used additives and thermoplastic elastomers may be added to the above-mentioned melt liquid crystal forming aromatic polyester within a range that does not impair the function of the present invention (e.g., less than 10% by weight).

[0071] In fibrous structures, from the perspectives of avoiding manufacturing process complexity, maintaining strength and flexibility, and controlling contact points during the formation of the metal coating, a nonwoven fabric structure is preferred. Examples of nonwoven fabrics include those formed by wet or dry processes, meltblown nonwovens, spunlace nonwovens, thermoplastic nonwovens, and needle-punched nonwovens. Among these nonwoven fabrics, fibers with small diameters and long lengths are preferred, and meltblown nonwovens are particularly advantageous. Especially when using conductive nonwoven fabrics as conductors, it is possible to obtain the aforementioned thin current collector, which comprises a meltblown nonwoven fabric formed from a molten liquid crystal forming aromatic polyester and a metal coating formed on the nonwoven fabric.

[0072] Specifically, the average fiber diameter of the fibers constituting the nonwoven fabric is 10 μm or less, preferably in the range of 0.1 to 10 μm. This is because when the average fiber diameter is less than 0.1 μm, it is easy to generate lint and form fiber clumps. In addition, when the average fiber diameter exceeds 10 μm, the texture becomes coarser, and the conductivity becomes insufficient when metal is coated. When meltblown nonwoven fabric is used as the nonwoven fabric, the average fiber diameter of the fibers constituting the meltblown nonwoven fabric is preferably in the range of 0.5 to 8 μm, more preferably in the range of 0.5 to 7 μm, and even more preferably in the range of 1 to 6 μm. It should be noted that the average fiber diameter of the fibers constituting the meltblown nonwoven fabric of the present invention refers to the average value obtained by magnifying and photographing the nonwoven fabric with a scanning electron microscope and measuring the diameter of any 100 fibers.

[0073] When applying nonwoven fabrics in three-dimensional porous structures, meltblown nonwoven fabrics with such molten liquid crystal forming aromatic polyesters as the main component are preferred.

[0074] (Metallic coating) When the conductive material of the present invention is a non-conductive structure with a metal coating, the metal coating is preferably coated on a fibrous structure, and more preferably on a non-woven fabric structure (specifically, on the fibers constituting the fibrous structure such as a non-woven fabric), from the viewpoints of avoiding manufacturing process complexity, maintaining strength, maintaining flexibility, and controlling the contact points during the formation of the metal coating. The metal coating preferably contains any metal selected from copper, nickel, gold, silver, and aluminum. These metals can be used alone or in combination of two or more. From the perspectives of high conductivity and ease of metal coating formation, multilayered coatings containing any metal selected from copper, nickel, gold, and aluminum are particularly preferred. From the perspectives of economy and high conductivity, copper, nickel, and aluminum are particularly preferred metal coatings. These metal coatings can be multilayered; for example, a first metal layer can be formed on a non-conductive structure, and then a second metal layer can be formed on the first metal layer.

[0075] The surface resistivity of the conductor of the present invention varies depending on the type and thickness of the metal coating. From the viewpoint of ensuring sufficient conductivity, a surface resistivity of 10 is preferred. -3 In the range of ~100Ω / □, more preferably in the range of 10 -3 ~10 -1 Within the range of Ω / □.

[0076] As a method for forming a metal coating, existing known methods such as electroplating, electroless plating, sputtering, and vacuum evaporation can be used. From the viewpoint of easily obtaining high conductivity, electroless plating is preferred. As an electroless plating method, existing known methods can be used without particular limitation. Generally, it is a method of forming a metal coating by immersing a non-conductive structure (e.g., the fiber surface of a nonwoven fabric) that serves as a substrate with a catalyst in an electroless plating bath containing dissolved metal salts, reducing agents, and buffers.

[0077] Regarding the thickness of the metal coating of the current collector (conductor) of the present invention, it is, for example, in the range of 0.05 to 10 μm, or in the range of 0.1 to 5 μm. From the viewpoint of imparting the aforementioned surface resistance value and controlling the air permeability of the current collector, it is more preferable to be 4 μm or less, or 2 μm or less. When the thickness of the metal coating is less than 0.05 μm, sufficient conductivity cannot be obtained. On the other hand, when the thickness of the metal coating is greater than 10 μm, the flexibility and suppleness of the current collector are impaired, which is therefore not preferred.

[0078] When a metal coating is formed, for example, an air permeability of 0.2–800 cc / cm can be achieved. 2 A non-conductive structure forms a metallic coating at a speed of 0.1–600 cc / cm². 2 / second of current collector.

[0079] For example, the air permeability of a non-conductive structure (e.g., a non-conductive meltblown nonwoven fabric) is preferably 0.2 to 800 cc / cm. 2 / second. The air permeability of the non-conductive structure exceeds 800cc / cm². 2 At a current-collector density of 800 cc / cm, it is difficult to set the permeability of the current collector within the aforementioned range, resulting in difficulty in achieving the desired resistance reduction. Therefore, 800 cc / cm is preferred. 2 Below / second, preferably 700cc / cm 2 Below / second, further preferably 600cc / cm 2 / second or less. Furthermore, there is no particular limitation on the lower limit of air permeability for non-conductive structures; however, from the viewpoint of ensuring mechanical strength and conductivity after metal coating, 0.2 cc / cm is preferred. 2 / second or higher, preferably 1cc / cm 2 / second or more.

[0080] Furthermore, the thickness of the non-conductive structure (e.g., non-conductive meltblown nonwoven fabric) is preferably in the range of 5 μm or more and less than 100 μm. When the thickness of the non-conductive structure is less than 5 μm, it tends to break easily during battery manufacturing and handling. Conversely, when the thickness of the non-conductive structure is 100 μm or more, the requirement for thin-film current collectors cannot be met. Therefore, the thickness of the non-conductive structure is preferably in the range of 5 μm or more and less than 100 μm, more preferably in the range of 7 to 30 μm, and even more preferably in the range of 9 to 20 μm.

[0081] The above description of the current collector can also be applied to the electrode of the second embodiment.

[0082] [Active Substances] The electrode of this invention comprises a current collector and an active material, and may contain a conductive agent and / or binder as needed. The active material is capable of absorbing and releasing electrolyte ions and has a specified median diameter (D). 50 Median diameter (D) 50 This indicates that in the particle size distribution determined by laser scattering, the particle size with a cumulative volume of 50% from the microparticle side is the boundary, and particles with larger and smaller particle sizes exist in equal volumes.

[0083] The preferred median diameter of the active material varies depending on the implementation of the electrode, but from the viewpoint of suppressing side reactions during charging and discharging and balancing electrode formability and the coatability of the active material layer (sometimes also called the active material component layer), it can also be 0.1 to 100 μm.

[0084] The above description can also be applied to the electrode of the second embodiment.

[0085] [First Embodiment of the Electrode] In one embodiment of the electrode of the present invention, it is preferable that the average opening diameter of the current collector and the median diameter of the active material satisfy a predetermined relationship. That is, when the average opening diameter of the current collector is A (μm) and the median diameter of the material is B (μm), and B / A satisfies the relationship of Equation (1) below, the capacity retention rate of the obtained electrochemical device can be improved because the active material can be effectively inserted into the opening portion of the current collector.

[0086] 0.10≤B / A≤2.00 (1) A smaller B / A value results in a larger average opening diameter of the current collector relative to the particle size of the active material, increasing the proportion of active material entering the current collector opening and thus increasing the contact area between the active material and the current collector. This reduces the resistance of the electrochemical device and improves capacity retention. However, if B / A is too small, excess active material clogs the current collector, increasing the electrolyte moving resistance. Consequently, the resistance of the electrochemical device increases, and the capacity retention decreases. Therefore, a B / A value below the lower limit of 0.10 is not preferred.

[0087] A higher B / A value means that, for current collectors with the same opening diameter, it is better able to prevent an increase in interfacial resistance between active materials and electrolyte migration resistance, thus reducing the resistance of the electrochemical device. However, if the B / A value exceeds the upper limit of 2.00, the proportion of active material entering the opening of the current collector decreases, and the contact area with the current collector decreases. As a result, it becomes difficult to improve the capacity retention rate of the electrochemical device.

[0088] The value of B / A is preferably 0.13 or higher, more preferably 0.15 or higher, and even more preferably 0.20 or higher. On the other hand, the value of B / A is preferably 1.96 or lower, more preferably 1.70 or lower, even more preferably 1.50 or lower, and particularly preferably 1.20 or lower. For example, B / A can be 0.13 to 1.96, 0.15 to 1.70, 0.20 to 1.50, or 0.20 to 1.20.

[0089] The preferred range can vary appropriately depending on the relationship with the median diameter of the active material, but the average opening diameter A can be, for example, 1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 10 to 20 μm, depending on the ease of forming the metal coating and the permeability of the electrolyte.

[0090] In this embodiment, the preferred range of the median diameter B of the active material varies appropriately according to its relationship with the average opening diameter of the current collector. However, from the viewpoint of suppressing side reactions during charging and discharging and taking into account both electrode formability and the coating properties of the active material layer, for example, the median diameter B of the active material can be 0.1 to 100 μm, more preferably 1 to 50 μm, or even more preferably 2 to 30 μm.

[0091] [positive electrode] As the positive electrode active material, as long as it has a specified average diameter in relation to the current collector, there is no particular limitation, and known positive electrode active materials can be used. As the positive electrode active material capable of absorbing and releasing electrolyte ions, examples include: layered oxide systems (represented by LiMO2 or NaMO2, where M is a metal; for example, LiCoO2, LiNiO2, LiMnO2, NaFeO2, NaNiO2, NaCoO2, NaMnO2, NaVO2, or LiNixCoyMnzO2, NaNixMnzO2 (here x, y, z represent the composition ratios)), olivine systems (represented by LiMPO4 or NaMPO4, where M is a metal; for example, LiFePO4, NaFePO4, etc.), spinel systems (represented by LiM2O4 or NaM2O4, where M is a metal; for example, LiMn2O4, NaMn2O4, etc.) of composite metal chalcogenides, lithium-excess spinel compounds represented by Li 1+x Mn 2-x O4 (0 < x < 2), metal oxides such as Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4, etc., phosphate-containing compounds, polyanion-containing compounds, Prussian blue analogs, sulfur, compounds or polymers having nitroxide radicals, compounds or polymers having oxygen radicals, compounds or polymers having nitrogen radicals, organic radicals such as compounds or polymers having a fulvalene skeleton. These positive electrode active materials can be used alone or in combination of two or more. Among them, composite metal chalcogenides are preferred.

[0092] In addition, in the case of constructing a battery with electrostatic adsorption such as a lithium-ion capacitor, carbon materials and inorganic materials with a high specific surface area such as activated carbon, mesoporous carbon, and defective titanium oxide, which are conductive ceramics, can be cited.

[0093] The positive electrode active material can be applied to the current collector as a positive electrode paste or can form a positive electrode active material layer. The content of the positive electrode active material in the positive electrode active material layer is preferably 80.0 to 99.9% by weight, more preferably 90 to 99.5% by weight, relative to the total weight of the positive electrode active material layer (or the total weight of the solid components of the paste).

[0094] The aforementioned positive electrode active material layer may also contain the aforementioned positive electrode active material, a binder as needed, and selectively contained conductive materials (conductive additives). The binder content in the aforementioned positive electrode active material layer may be 1% to 5% by weight relative to the total weight of the positive electrode active material layer. Furthermore, if conductive materials are further included, 90% to 98% by weight of the positive electrode active material, 1% to 5% by weight of the binder, and 1% to 5% by weight of the conductive material may be used. When the positive electrode active material layer contains binders, conductive materials (conductive additives), etc., in addition to the positive electrode active material, the solid components containing these components are sometimes referred to as the positive electrode active material component, and the positive electrode active material layer is referred to as the positive electrode active material component layer.

[0095] The aforementioned adhesive facilitates good adhesion between the positive electrode active material particles and the positive electrode active material, and also ensures good adhesion of the positive electrode active material to the current collector. As the aforementioned adhesive, non-water-soluble adhesives, water-soluble adhesives, or combinations thereof can be used.

[0096] Examples of the aforementioned non-water-soluble adhesives include polyvinyl chloride (PVC), carboxylated PVC, polyvinyl fluoride (PVC), polymers containing ethylene oxide, polyvinylpyrrolidone (PVP), polyurethane, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polyamide-imide, polyimide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, copolymers of (meth)acrylic acid and (meth)acrylic acid alkyl esters, copolymers of olefins with 2 to 8 carbon atoms and maleic acid, PVC, carboxylated PVC, PVC, polymers containing ethylene oxide, polyvinylpyrrolidone (PVP), polyurethane, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, polypropylene, copolymers of propylene and olefins with 2 to 8 carbon atoms, polyamide-imide, polyimide, or combinations thereof.

[0097] Examples of the aforementioned water-soluble adhesives include polyvinyl alcohol, copolymers of vinyl alcohol and olefinic unsaturated carboxylic acids and their alkali metal modified products, alkali metal modified products of olefin-olefinic unsaturated carboxylic acid copolymers with 2-4 carbon atoms, alkali metal modified products of olefin-maleic anhydride copolymers with 2-4 carbon atoms, sodium poly(meth)acrylate, etc.

[0098] The aforementioned positive electrode can further utilize a cellulose-based compound that imparts viscosity as a thickener. As this cellulose-based compound, one or more carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts can be used in combination. As the aforementioned alkali metal, Na, K, or Li can be used. The amount of such thickener used can be from 0.1 parts by weight to 3 parts by weight relative to 100 parts by weight of the active material.

[0099] The aforementioned conductive materials are used to impart conductivity to the electrodes. Any material can be used as long as it is an electronically conductive material that does not cause chemical changes in the battery. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as copper, nickel, aluminum, and silver powders or metal fibers; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0100] As a solvent used in the slurry for the positive electrode, an organic solvent can be used, wherein a polar organic solvent capable of dissolving the binder, as described later, is preferred.

[0101] Specifically, acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, ethylenediamine, etc., can be used as organic solvents. Among these, N-methylpyrrolidone (NMP) is the most preferred from the viewpoints of ease of handling, safety, and ease of synthesis.

[0102] It should be noted that these organic solvents can be used alone or in combination of two or more.

[0103] The amount of the solvent used is preferably 1 to 80% by weight, more preferably 5 to 70% by weight, and even more preferably 10 to 60% by weight in the solid component concentration of the positive electrode slurry. By setting the solid component concentration within the above range, it is possible to uniformly disperse the positive electrode active material and other contained components, which is therefore suitable.

[0104] As a method for manufacturing the positive electrode slurry, it can be manufactured by mixing the above-mentioned positive electrode active material and other components as needed in the above-mentioned solvent. There are no particular limitations on the mixing method; for example, a general mixing device such as a disperser, mill, or kneader can be used. For example, stirring for 20 minutes or more and 120 minutes or less is preferred.

[0105] There are no particular restrictions on the mixing temperature; for example, it can be in the range of 0°C to 160°C, more preferably in the range of 20°C to 80°C. Too low a temperature will increase the viscosity and make coating impossible, so it is not preferred. At too high a temperature, it is not preferred from the viewpoints of safety and equipment operability, considering factors such as the evaporation of organic solvents and associated viscosity changes.

[0106] The aforementioned positive electrode is made using a positive electrode slurry and includes a current collector and a positive electrode active material layer. The positive electrode active material layer can be formed by mixing the active material, conductive materials as needed, and adhesives, molding it into a sheet, and then depositing it on the current collector as the positive electrode active material layer. Alternatively, it can be formed by coating (applying) the positive electrode slurry onto the current collector and then drying it.

[0107] There are no particular limitations on the method for coating the positive electrode slurry onto the current collector, and known methods can be used. Specifically, coating methods can include doctor blade coating, dip coating, reverse roller coating, direct roller coating, gravure coating, extrusion coating, brush coating, etc. In this case, the positive electrode slurry can be coated only on one side of the current collector, or it can be coated on both sides. The thickness of the slurry film on the current collector before drying can be appropriately set according to the thickness of the positive electrode composite material layer obtained after drying.

[0108] There are no particular limitations on the method for drying the positive electrode of the current collector with a slurry; known methods can be used, such as drying with warm air, hot air, low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. By drying the positive electrode of the electrochemical element on the current collector with a slurry in this way, a positive electrode active material layer can be formed on the current collector, resulting in a positive electrode having both a current collector and a positive electrode active material layer.

[0109] The preferred drying process is carried out by drying the positive electrode slurry on the current collector at a drying temperature of 100°C or higher and 160°C under atmospheric pressure or reduced pressure for 1 to 12 hours.

[0110] It should be noted that, after the drying process, a mold press or roller press can be used to apply pressure to the positive electrode active material layer. This pressure treatment can improve the adhesion between the positive electrode active material layer and the current collector.

[0111] The thickness of the positive electrode active material varies depending on the manufacturing method and the required battery performance, and is therefore not limited. It is usually 10μm to 200μm, more preferably 20μm to 150μm, and considering the battery capacity and its compatibility with the negative electrode, it is formed to be 25μm to 130μm.

[0112] [negative electrode] There are no particular limitations on the negative electrode active material as long as it has a specified average diameter in relation to the current collector; known negative electrode active materials can be used. Negative electrode active materials include substances capable of absorbing and releasing electrolyte ions, alkali metals (Li, Na, K, Rb, Cs), alkaline earth metals (Be, Mg, Ca, Sr, Ba), alloys of alkali metals and alkaline earth metals, doped and dedoped substances of alkali metals and alkaline earth metals, or transition metal oxides.

[0113] The substance capable of absorbing and releasing electrolyte ions described above is preferably a carbonaceous material. For example, as long as it is a commonly used carbon-based negative electrode active material, any substance can be used. As representative examples, crystalline carbon, amorphous carbon, or a combination of them can be used. As particles of crystalline carbon, graphite such as amorphous, plate-shaped, scaly, spherical, or fibrous natural graphite or artificial graphite can be cited. As examples of the above amorphous carbon, soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc. can be cited. These can also be used in a state where lithium is previously occluded.

[0114] As the alloy of the above alkali metal and alkaline earth metal, an alloy of an alkali metal and an alkaline earth metal and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0115] As substances that can be doped and de-doped into alkali metals and alkaline earth metals, Si, SiO x (0 < x < 2), Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and their combinations, and is not Si), Sn, SnO2, Sn-R (where R is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and their combinations, and is not Sn), etc. can also be used by mixing at least one of them with SiO2. As the above elements Q and R, substances selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and their combinations can be used.

[0116] As the above transition metal oxide, vanadium oxide, lithium vanadium oxide, etc. can be cited.

[0117] In the case of constructing a battery that adsorbs electrostatic electrolyte ions such as an electric double layer capacitor and a lithium ion capacitor, carbon materials and inorganic materials with a high specific surface area such as activated carbon, mesoporous carbon, and conductive ceramics such as defective titanium oxide can be cited.

[0118] The negative electrode active material can be used as a negative electrode slurry in current collectors or to form a negative electrode active material layer. The content of the negative electrode active material in the negative electrode active material layer relative to the total weight of the negative electrode active material layer (or the total weight of the solid components of the slurry) is preferably 80.0 to 99.9% by weight, more preferably 90 to 99.5% by weight.

[0119] The aforementioned negative electrode active material layer may further comprise the aforementioned negative electrode active material, and, as needed, a binder and selectively contained conductive material (conductive additive). In the aforementioned negative electrode active material layer, the binder content relative to the total weight of the negative electrode active material layer may be 1% to 5% by weight. Furthermore, when conductive material is also included, it is preferable to use 90% to 98% by weight of the negative electrode active material, and 1% to 5% by weight of the binder and conductive material.

[0120] The aforementioned adhesive serves to ensure good adhesion between the negative electrode active material particles and to ensure good adhesion of the negative electrode active material to the current collector. As the aforementioned adhesive, a non-water-soluble adhesive, a water-soluble adhesive, or a combination thereof can be used. As a non-water-soluble adhesive or a water-soluble adhesive, the substances exemplified in the description of the positive electrode active material layer can also be used.

[0121] Furthermore, the negative electrode active material layer can use a conductive material, or it can use the material exemplified in the description of the positive electrode active material layer. When the negative electrode active material layer contains binders, conductive materials (conductive additives), etc., in addition to the negative electrode active material, the solid components containing these are sometimes referred to as the negative electrode active material components, and the negative electrode active material layer is referred to as the negative electrode active material component layer.

[0122] The negative electrode active material layer can be formed from a negative electrode slurry. The solvent used in the negative electrode slurry can also be the solvent exemplified in the description of the positive electrode active material layer.

[0123] The negative electrode can also be prepared with a solvent in the same way as the positive electrode to form a negative electrode slurry, and applied to the current collector. For example, the above-mentioned active material can be mixed with conductive materials, adhesives, etc. as needed and molded into a sheet, which is then formed as a negative electrode active material layer on the current collector. Alternatively, a slurry of ink-like active material, conductive material, and adhesive can be coated onto the current collector and dried to form a negative electrode active material layer.

[0124] The thickness of the negative electrode active material layer varies depending on the manufacturing method and the desired battery performance, and is therefore not limited. It is typically 10 μm to 200 μm, more preferably 20 μm to 150 μm, and can be formed to 25 μm to 130 μm, taking into account the battery capacity and compatibility with the positive electrode.

[0125] As described below, in this embodiment, at least a portion of the voids in the current collector is preferably filled with a component comprising active materials (positive electrode active material, negative electrode active material) and, as needed, a binder, conductive agent, etc. (active material component). In the electrode of this embodiment, the average opening diameter A of the current collector and the median diameter (D) of the active material are... 50 B satisfies the specified relationship, therefore, during the formation of the above-mentioned active material layer, the slurry containing the active material penetrates into the voids of the current collector, and the voids can be filled with the active material components.

[0126] The electrode includes a current collector and an electrode material layer disposed on at least one surface of the current collector. Here, "electrode material layer disposed on surface of current collector" means that the electrode material layer has a portion adjacent to the current collector, and also includes the case where a portion of the electrode material layer extends into the interior of the current collector.

[0127] Implementation Method 2 In the second embodiment of the present invention, the structure of the current collector and the definition of the median diameter of the active material can also be applied to the content described in the first embodiment. Therefore, in the electrode of the second embodiment, the relationship between the porous structure of the current collector and the active material will be explained first.

[0128] [Second Embodiment of the Electrode] In this embodiment, the electrode preferably comprises a current collector having a three-dimensional porous structure and an active material component filled within the current collector. The filling rate of the active material component relative to the current collector is controlled within a specified range. Here, the active material component refers to a solid component based on an active material, containing the active material and, as needed, binders, conductive additives, etc. The filling rate of the active material component relative to the current collector is preferably 37% or more, more preferably 45% or more. Here, in the cross-section of the current collector filled with the active material component, the ratio of the area occupied by the active material component to the void area of ​​the current collector is defined as the filling rate. By increasing the filling rate, the contact area between the solid phase portion of the current collector (e.g., fibers with a metal coating) and the active material can be increased, thereby improving the capacity retention rate of the electrochemical device. Hereinafter, using... Figure 2 and Figure 3 Explain the method for determining the filling rate.

[0129] Figure 2 This is a scanning electron microscope image (SEM image) obtained by photographing a cross-section along the thickness direction of the electrode. In the image, the highest and lowest positions of the projected portion of the current collector are identified, and straight lines orthogonal to the thickness direction containing these positions are drawn as L1 and L2. The distance between these straight lines is defined as the thickness T of the current collector.

[0130] Next, determine the leftmost and rightmost positions of the projected portion of the current collector in the photograph, and draw out the straight lines parallel to the thickness direction that contain their respective positions as L3 and L4. The distance between these straight lines is defined as the observation length (width of the observation area) W of the current collector.

[0131] Therefore, the observation area is defined as observation area (α) = thickness of the collector × observation length.

[0132] Next, using image analysis software ("Multi-file Analysis Application" manufactured by Keynes Co., Ltd.), the settings were configured to distinguish between the black parts and the other parts. Using the binarized image, the projected areas of the active material and the current collector within the observation area were calculated as (β) and (γ), respectively.

[0133] Figure 3 Indicated for explanation Figure 2 A schematic diagram showing the locations of the current collector and active material within the observation area. Figure 3 In the diagram, the area occupied by active material 2 is represented by a dot, and the area occupied by current collector 1 is represented by a diagonal line. Furthermore, the portion where neither active material 2 nor current collector 1 exists represents void 3. That is, the observed area (α) is formed by the combined area of ​​current collector 1 (the solid phase portion of the current collector), active material 2, and void 3. The area where active material 2 exists is equivalent to the projected area (β) of the active material, and the area where current collector 1 exists is equivalent to the projected area (γ) of the current collector.

[0134] By removing the portion containing current collector 1 from the observed area (α), the area within the observed area (α) that can be filled with active material can be determined. That is, the value (α-γ) of removing the projected area (γ) of the current collector from the observed area (α) is equivalent to the area within the observed area that can be filled with active material. Figure 3 The area in the middle is occupied by active substance 2 and void 3.

[0135] Furthermore, the ratio of the area (α-γ) occupied by active substance 2 to the area (β) that can be filled with active substance 2 is expressed by the formula: β / (α-γ)×100. Thus, the ratio of the actual area (β) filled with active substance to the area (α-γ) that can be filled with active substance in the observed area can be defined as the filling rate (%).

[0136] The filling rate can be 37% or more, preferably 45% or more, further preferably 50% or more, and more preferably 60% or more. There is no specific upper limit for the filling rate, and it can be 100%, but to ensure electrolyte permeability, it is preferably 90% or less. Therefore, the filling rate can, for example, be 45% or more and 90% or less.

[0137] The active material component only needs to be present at a filling rate of more than 37%, preferably more than 45%, inside the current collector. If necessary, an active material component layer can also be formed on the surface of the current collector.

[0138] The overall thickness of the electrode varies depending on the electrode manufacturing method and the required battery performance, and is therefore not limited. For example, it can be 20 μm to 500 μm, preferably 30 μm to 400 μm, and more preferably 40 μm to 300 μm. The thickness of the active material component layer is a value measured by the method described in the examples below.

[0139] The thickness of the active material layer varies depending on the electrode manufacturing method and the required battery performance, and is therefore not limited. For example, it can be 5 μm to 200 μm, preferably 10 μm to 150 μm, and more preferably 20 μm to 130 μm. It should be noted that the thickness of the active material layer refers to the total thickness in the electrode. When an active material layer is provided on only one side, it is considered one layer thickness; when active material layers are provided on both sides, it is considered the total thickness of two layers. The thickness of the active material layer is a value measured using the method described in the examples below.

[0140] By increasing the filling rate of the active material component in the current collector, the ratio of the thickness of the active material component layer to the thickness of the current collector can be reduced. For example, as (thickness of the active material component layer) / (thickness of the current collector), it can be 0.5 to 8, preferably 0.6 to 7. The thickness of the active material component layer is a value measured by the method described in the examples below.

[0141] The electrode density is determined based on the height of the filler layer and the proportion of the active material components, and is therefore not limited; for example, it can be 1.00–2.00 g / cm³. 3 The preferred value is 1.05–1.80 g / cm³. 3 The electrode density is a value determined by the method described in the examples described later.

[0142] [positive electrode] As the positive electrode active material, there is no particular limitation as long as it has a specified average diameter in relation to the current collector, and known positive electrode active materials can be used. Examples of positive electrode active materials capable of absorbing and releasing electrolyte ions include: layered oxide systems (represented by LiMO2 or NaMO2, where M is a metal; for example, LiCoO2, LiNiO2, LiMnO2, NaFeO2, NaNiO2, NaCoO2, NaMnO2, NaVO2, or LiNixCoyMnzO2, NaNixMnzO2 (where x, y, and z represent the composition ratios)), olivine systems (represented by LiMPO4 or NaMPO4, where M is a metal; for example, LiFePO4, NaFePO4, etc.), spinel systems (represented by LiM2O4 or NaM2O4, where M is a metal; for example, LiMn2O4, NaMn2O4, etc.) of composite metal chalcogenides, lithium-excess spinel compounds represented by Li 1+x Mn 2-x O4 (0 < x < 2), metal oxides such as Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn 1.5 O4, etc., phosphate-containing compounds, polyanion-containing compounds, Prussian blue analogs, sulfur, organic radicals such as compounds or polymers having a nitroxide radical, compounds or polymers having an oxygen radical, compounds or polymers having a nitrogen radical, compounds or polymers having a fulvalene skeleton. These positive electrode active materials can be used individually or in combination of two or more. Among them, composite metal chalcogenides are preferred.

[0143] In addition, in the case of constructing an electrostatic adsorption battery such as a lithium-ion capacitor, carbon materials and inorganic materials having a high specific surface area such as activated carbon, mesoporous carbon, defective titanium oxide, and conductive ceramics can be cited.

[0144] The positive electrode active material is applied to the current collector as a positive electrode paste, and the positive electrode active material portion can also be formed. The content of the positive electrode active material in the positive electrode active material portion is preferably 80.0 to 99.9% by weight, more preferably 90 to 99.5% by weight, based on the total weight of the positive electrode active material portion (or the total weight of the solid components of the paste).

[0145] The aforementioned positive electrode active material portion may further contain the aforementioned positive electrode active material, a binder as needed, and selectively contained conductive material (conductive additive). The binder content in the aforementioned positive electrode active material portion may be 1% to 5% by weight relative to the total weight of the positive electrode active material portion. Furthermore, if conductive material is further included, a composition of 90% to 98% by weight of positive electrode active material, 1% to 5% by weight of binder, and 1% to 5% by weight of conductive material may be used.

[0146] The aforementioned adhesive facilitates good adhesion between the positive electrode active material particles and the positive electrode active material, and also ensures good adhesion of the positive electrode active material to the current collector. As the aforementioned adhesive, non-water-soluble adhesives, water-soluble adhesives, or combinations thereof can be used.

[0147] Examples of the aforementioned non-water-soluble adhesives include polyvinyl chloride (PVC), carboxylated PVC, polyvinyl fluoride (PVC), polymers containing ethylene oxide, polyvinylpyrrolidone (PVP), polyurethane, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polyamide-imide, polyimide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, copolymers of (meth)acrylic acid and (meth)acrylic acid alkyl esters, copolymers of olefins with 2 to 8 carbon atoms and maleic acid, PVC, carboxylated PVC, PVC, polymers containing ethylene oxide, polyvinylpyrrolidone (PVP), polyurethane, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, polypropylene, copolymers of propylene and olefins with 2 to 8 carbon atoms, polyamide-imide, polyimide, or combinations thereof.

[0148] Examples of the aforementioned water-soluble adhesives include polyvinyl alcohol, copolymers of vinyl alcohol and olefinic unsaturated carboxylic acids and their alkali metal modified products, alkali metal modified products of olefin-olefinic unsaturated carboxylic acid copolymers with 2-4 carbon atoms, alkali metal modified products of olefin-maleic anhydride copolymers with 2-4 carbon atoms, sodium poly(meth)acrylate, etc.

[0149] The aforementioned positive electrode adhesive can be further modified by using a cellulose-based compound as a tackifier. This cellulose-based compound can be a mixture of one or more carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts. For example, a substance containing carboxymethyl cellulose added to styrene-butadiene rubber can be used as the adhesive. The aforementioned alkali metal can be Na, K, or Li. The amount of this tackifier used can be from 0.1 parts by weight to 3 parts by weight relative to 100 parts by weight of the active material.

[0150] The aforementioned conductive materials are used to impart conductivity to the electrodes. Any material can be used as long as it is an electronically conductive material that does not cause chemical changes in the battery. Examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as copper, nickel, aluminum, and silver powders or metal fibers; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0151] Solvents used in cathode slurries can include, for example, water and various organic solvents (such as amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, etc.). It should be noted that these solvents can be used alone or in mixtures of two or more.

[0152] As the organic solvent, a polar organic solvent capable of dissolving the adhesive is preferred. For example, acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, ethylenediamine, etc., are preferred. Among these, N-methylpyrrolidone (NMP) is most preferred from the viewpoints of ease of handling, safety, and ease of synthesis.

[0153] The amount of the solvent used is preferably 1 to 80% by weight, more preferably 5 to 70% by weight, and even more preferably 10 to 60% by weight in the solid component concentration of the positive electrode slurry. By setting the solid component concentration within the above range, it is possible to uniformly disperse the positive electrode active material and other contained components, which is therefore suitable.

[0154] The electrode manufacturing method includes at least the step of filling an active material component into a current collector with a three-dimensional porous structure.

[0155] When filling current collectors with active material components, the filling rate of the active material components can be improved, for example by (i) adjusting the slurry viscosity to an appropriate range, (ii) adjusting the slurry surface tension to an appropriate range, and / or (iii) adapting the application method. (i) to (iii) above can be performed individually or in combination of two or more.

[0156] It should be noted that the active material component refers to the solid component of the slurry, such as active materials, binders, conductive materials, etc.

[0157] As a method for manufacturing the positive electrode slurry, it can be manufactured by mixing the above-mentioned positive electrode active material and other components as needed in the above-mentioned solvent. There are no particular limitations on the mixing method; for example, a general mixing device such as a disperser, mill, or kneader can be used. For example, stirring for 20 minutes or more and 120 minutes or less is preferred.

[0158] There are no particular restrictions on the mixing temperature; for example, it can be in the range of 0°C to 160°C, more preferably in the range of 20°C to 80°C. Too low a temperature will increase the viscosity and make coating impossible, so it is not preferred. At too high a temperature, it is not preferred from the viewpoints of safety and equipment operability, considering factors such as the evaporation of organic solvents and associated viscosity changes.

[0159] (i) The slurry viscosity can be, for example, 10,000 mPa·s or less, preferably 7,000 mPa·s or less, and more preferably 5,000 mPa·s or less. If the slurry viscosity is too high, the slurry containing active material components will have difficulty penetrating into the interior of the current collector. There is no particular limitation on the lower limit of the slurry viscosity, but from the viewpoint of efficiently filling active material components, it can be 50 mPa·s or more.

[0160] (ii) When water, which has a high surface tension, is used as a solvent, it is preferable to adjust the surface tension of the slurry. For example, water and a surface conditioner for reducing the surface tension of water can be used in combination as solvents. Examples of surface conditioners include lower alcohols such as methanol and ethanol (preferably C14). 1-3 Defoamers include alcohols, various surfactants, and silicone-based oils. The ratio of the surface modifier to water can be appropriately selected depending on the type of surface modifier used. For example, in the case of lower alcohols, the ratio can be 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight, relative to 100 parts by weight of water. In the case of defoamers, the ratio can be 0.005 to 2 parts by weight, preferably 0.01 to 1.5 parts by weight, relative to 100 parts by weight of water. It should be noted that the surface modifier can be used mixed with or without water.

[0161] (iii) Application methods are broadly categorized into coating and dip methods. There are no particular limitations on the method of coating the positive electrode slurry onto the current collector; known methods can be used. Specifically, coating methods include doctor blade coating, dip coating, reverse roller coating, direct roller coating, gravure coating, extrusion coating, and brush coating. In this case, the positive electrode slurry can be coated only on one side of the current collector or on both sides. During coating, the filling rate can be increased, for example, by adjusting the slurry applied using methods (i) and / or (ii) described above.

[0162] Furthermore, when using the impregnation method, while the current collector is immersed in the slurry, methods such as holding, pressurizing, or using ultrasound to vibrate the slurry are employed to promote degassing, thereby facilitating the removal of air from the current collector. This allows for effective filling of the interior of the current collector.

[0163] Then, the slurry can be dried as needed. There are no particular limitations on the drying method; known methods can be used, such as drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with infrared rays, electron beams, etc.

[0164] The preferred drying process is carried out by drying the positive electrode slurry on the current collector at a drying temperature of 60°C or higher and 160°C under atmospheric pressure or reduced pressure for 1 to 12 hours.

[0165] It should be noted that, after the drying process, the positive electrode active material can also be pressurized using a mold press or roller press, as needed. Pressurization can improve the adhesion between the positive electrode active material and the current collector.

[0166] [negative electrode] There are no particular limitations on the negative electrode active material as long as it has a specified average diameter in relation to the current collector; known negative electrode active materials can be used. Negative electrode active materials include substances capable of absorbing and releasing electrolyte ions, alkali metals (Li, Na, K, Rb, Cs), alkaline earth metals (Be, Mg, Ca, Sr, Ba), alloys of alkali metals and alkaline earth metals, doped and dedoped substances of alkali metals and alkaline earth metals, or transition metal oxides.

[0167] The aforementioned substances capable of absorbing and releasing electrolyte ions are preferably carbonaceous materials. For example, any commonly used carbon-based negative electrode active material can be used; crystalline carbon, amorphous carbon, or a combination thereof can be used as examples. Examples of crystalline carbon particles include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite. Examples of amorphous carbon include soft or hard carbon, mesophase pitch carbides, and calcined coke. These can also be used in a state where lithium is pre-absorbed.

[0168] As alloys of the aforementioned alkali metals and alkaline earth metals, alloys of alkali metals and alkaline earth metals and alloys of metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0169] Examples of substances that can be doped and dedoped into alkali metals and alkaline earth metals include Si and SiO. x(0 < x < 2), Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and not Si), Sn, SnO2, Sn-R (where R is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and not Sn), etc. At least one of them can also be mixed with SiO2 for use. As the above elements Q and R, substances selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof can be used.

[0170] As the above transition metal oxides, vanadium oxides, lithium vanadium oxides, etc. can be cited.

[0171] In the case of constructing a battery that adsorbs electrostatic electrolyte ions such as an electric double layer capacitor or a lithium ion capacitor, carbon materials and inorganic materials with a high specific surface area such as activated carbon, mesoporous carbon, and defective titanium oxide, which are conductive ceramics, can be cited.

[0172] When applying the negative electrode active material to the current collector, it can be carried out by the application method exemplified in the description of the positive electrode active material part. Therefore, as the negative electrode slurry, it can be applied to the current collector or the negative electrode active material part can be formed. The content of the negative electrode active material in the negative electrode active material part is preferably 80.0 to 99.9% by weight, more preferably 90 to 99.5% by weight, relative to the total weight of the negative electrode active material part (or the total weight of the solid components of the slurry).

[0173] The above negative electrode active material part can further contain the above negative electrode active material, and a binder as necessary, and a conductive material (conductive aid) contained selectively. In the above negative electrode active material part, the content of the binder can be 1% to 5% by weight relative to the total weight of the negative electrode active material part. In addition, when a conductive material is also contained, it is preferable to use 90% to 98% by weight of the negative electrode active material, 1% to 5% by weight of the binder, and 1% to 5% by weight of the conductive material.

[0174] The aforementioned adhesive serves to ensure good adhesion between the negative electrode active material particles and to ensure good adhesion of the negative electrode active material to the current collector. As the aforementioned adhesive, non-water-soluble adhesives, water-soluble adhesives, or combinations thereof can be used. As non-water-soluble or water-soluble adhesives, the substances exemplified in the description of the positive electrode active material can also be used.

[0175] Furthermore, the negative electrode active material portion can use a conductive material, or the material exemplified in the description of the positive electrode active material portion can be used as the conductive material.

[0176] The negative electrode active material portion can be formed from a negative electrode slurry. The solvent used in the negative electrode slurry can also be the solvent exemplified in the description of the positive electrode active material portion.

[0177] Similar to the positive electrode, the negative electrode is filled with active material components to form a current collector with a three-dimensional porous structure.

[0178] Regarding the relationship that the current collector and active material in the electrode described above should satisfy, the electrode of the present invention can satisfy the conditions of either the first embodiment or the second embodiment, but preferably the electrode of the present invention can satisfy the conditions of both the first embodiment and the second embodiment.

[0179] That is, in the electrode of the first embodiment, the aforementioned current collector is filled with an active material component containing the aforementioned active material, and the filling rate (%) specified by the following formula (2) can be 37% or more. Fill rate (%) = β / (α-γ) × 100 (2) In the formula, α represents the observation area, which is determined by the thickness of the current collector × the observation length, based on an electron microscope image of the cross-section in the electrode thickness direction. β and γ represent the projected areas of the active material and the current collector, respectively, calculated using image analysis software within the observation area.

[0180] Alternatively, in the electrode of the second embodiment, the average opening diameter A (μm) of the current collector is equal to the median diameter (D) of the active material. 50 )B(μm) can satisfy the following relationship (1).

[0181] 0.10≤B / A≤2.00 (1) [Electrochemical equipment] Figure 4 This is a schematic cross-sectional view showing one configuration example (non-aqueous electrolyte secondary battery) of the electrochemical device 10. In the electrochemical device 10, the positive electrode 4 and the negative electrode 5 are arranged opposite each other with a separator 6 between them. The positive electrode 4 includes a positive electrode-side current collector 4a and a positive electrode active material layer 4b, and the negative electrode 5 includes a negative electrode-side current collector 5a and a negative electrode active material layer 5b. They can also be housed in a casing (not shown).

[0182] The electrochemical device 10 of the present invention includes an electrode according to either the first or second embodiment of the present invention. The electrode of the present invention can be used for either the positive electrode 4 or the negative electrode 5, or either one. In the case where the current collector of the present invention is used only for one electrode, in electrodes where the electrode of the present invention is not used, a known or conventional current collector (e.g., copper foil, nickel foil, aluminum foil, etc.) that has conductivity and electrochemical durability can be used as the current collector.

[0183] For example, in the case of the electrochemical device 10 of the present invention being a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte secondary battery does not particularly limit the other materials constituting the battery such as the separator 6 and the electrolyte (not shown), and various materials conventionally used or proposed in non-aqueous electrolyte secondary batteries can be used.

[0184] [Electrolytes] The electrolyte can be any known electrolyte that can be used in electrochemical devices. When used as a non-aqueous electrolyte battery, it preferably contains at least a non-aqueous organic solvent and an alkali metal salt such as a lithium salt.

[0185] The aforementioned non-aqueous organic solvents act as a medium that enables the movement of ions participating in the electrochemical reactions of the battery.

[0186] As non-aqueous organic solvents, carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents can be used. For the aforementioned carbonate-based solvents, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC) can be used. For the aforementioned ester-based solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolactone, valerate, mevalonolactone, and caprolactone can be used. For the aforementioned ether-based solvents, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran can be used. For the aforementioned ketone-based solvents, cyclohexanone can be used. In addition, ethanol, isopropanol, etc. can be used as the above-mentioned alcohol solvents, and nitrile solvents such as R-CN (R is a straight-chain, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, which may contain aromatic rings or ether bonds), amide solvents such as dimethylformamide, dioxolane solvents such as 1,3-dioxolane, sulfones, etc. can be used as the above-mentioned aprotic solvents.

[0187] The aforementioned non-aqueous organic solvents can be used alone or in combination of more than one. When using more than one solvent, the mixing ratio can be adjusted appropriately according to the target battery performance.

[0188] Furthermore, in the case of the aforementioned carbonate solvents, cyclic carbonates and chain carbonates can be mixed. In this case, when cyclic carbonates and chain carbonates are mixed in a volume ratio of 1:1 to 1:9, the electrolyte performance is better exhibited.

[0189] The aforementioned alkali metal salts (e.g., lithium salts) are soluble in organic solvents and can function as a source of alkali metal ions (e.g., lithium ions) within a battery, thus enabling the basic operation of an alkali metal ion secondary battery (e.g., a lithium-ion secondary battery). They are substances that promote the movement of alkali metal ions between the positive and negative electrodes. Representative examples of such alkali metal salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiC4F9SO3, LiClO4, LiAlO4, LiAlCl4, and LiN(C x F 2x＋1 SO2)(C y F 2y＋1 SO2 (where x and y are natural numbers), LiCl, LiI, and LiB(C2O4)2 (lithium dioxolane borate (LiBOB), NaClO4, NaPF6, NaBF4, NaCF3SO3, NaN(CF3SO2)2, NaN(FSO2)2, NaN(C2F5SO2)2, NaC(CF3SO2)3, NaAsF6, NaPF6, NaB(C6H5)4, CH3SO3Na, CF3SO3Na, NaCl, or NaBr, etc. These can be used alone or in mixtures of two or more. Preferably, the concentration of the alkali metal salt can be used in the range of 0.1–2.0 M. When the concentration of the alkali metal salt is less than 0.1 M, there is a tendency for the electrolyte conductivity to decrease and the electrolyte performance to deteriorate; when the concentration exceeds 2.0 M, there is a tendency for the electrolyte viscosity to increase and the mobility of alkali metal ions to decrease.

[0190] To improve battery life, the electrolyte may further contain vinylene carbonate or ethylene carbonate compounds as life enhancers.

[0191] Representative examples of the aforementioned vinyl carbonate compounds include difluoroethylene carbonate, vinyl chloride carbonate, dichloroethylene carbonate, vinyl bromide carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or fluoroethylene carbonate. When such a lifespan enhancer is further used with the aforementioned electrolyte, its dosage can be appropriately adjusted.

[0192] [Partition] In the electrochemical device of the present invention, a separator may exist between the positive and negative electrodes. Such a separator can be any known or conventional separator, such as a polyethylene membrane, a polypropylene membrane, a polyvinylidene fluoride membrane, or a multilayer membrane consisting of two or more layers of these materials. Hybrid multilayer membranes such as a two-layer polyethylene / polypropylene separator, a three-layer polyethylene / polypropylene / polyethylene separator, or a three-layer polypropylene / polyethylene / polypropylene separator may also be used. Example

[0193] The present invention will be described in more detail below through examples, but the present invention is not limited to any of the examples. It should be noted that the physical properties of the examples and comparative examples in the present invention refer to the physical properties measured by the following methods.

[0194] [Median diameter D] 50 (μm)] Median diameter D of carbon precursors and carbonaceous materials 50 (Particle size distribution) was determined by laser scattering as follows. The active material samples from the examples and comparative examples described later were placed in an aqueous solution containing 0.3% by weight of a surfactant (wako Pure Chemical Industries, Ltd.'s "polyoxyethylene (10) octylphenyl ether"), and treated with an ultrasonic cleaner for at least 10 minutes to disperse the sample in the aqueous solution. The particle size distribution was determined using this dispersion. The particle size distribution was determined using a particle size analyzer (Microtrace Bell Ltd.'s "MT3000II") with the solvent refractive index at 1.33 and particle permeability set to absorption. The particle size at 50% of the cumulative volume was set as the average particle size D. 50 .

[0195] [Average opening diameter (μm)] The current collector was cut out at a 2×2cm length along the surface. The cut sample was then held in place by a glass slide and set on a black-backed plate. Next, the sample was observed at 200x magnification using a shape-resolving laser microscope (VK-X1000, manufactured by Keynes Corporation).

[0196] Next, the observation image obtained at a size of 0.75×1.00mm was binarized using image analysis software ("Multi-file Analysis Application" manufactured by Keynes Co., Ltd.) by setting a threshold to distinguish the black parts from the other parts from the plate, and the black parts that could be identified as the substrate were used as each through hole.

[0197] The observed image obtained through image processing was used with an area of ​​2μm. 2The diameter of each through-hole is calculated by taking the diameter of a circle with the same cross-sectional area as the diameter of the corresponding circle. The average opening diameter is calculated for the through-hole opening diameters at 500–5000 points obtained from the observed images, and this average is taken as the average opening diameter for each sample.

[0198] [Average fiber diameter (μm)] The sample sheet (non-woven fabric) was photographed at 1000x magnification using a scanning electron microscope. The diameter of 100 fibers was measured, and the average value of the obtained values ​​was taken as the average fiber diameter of the sample sheet.

[0199] Weight per unit area (g / m²) 2 )] According to JIS L 1906, three sample pieces (20cm x 20cm) were collected from every 1m of the width of the samples (non-woven fabric) prepared in the examples and comparative examples. The mass of each sample piece was measured using an electronic balance, and the average mass of the three sample pieces was divided by the area of ​​the test piece, 400cm². 2 The average mass per unit area is calculated and used as the unit area weight of the nonwoven fabric.

[0200] [Thickness (μm)] According to JIS L 1906, three identical specimens prepared for the unit area weight determination were used. In each specimen, a sample with a diameter of 16 mm and a load of 20 gf / cm² was passed through it. 2 The digital thickness gauge (manufactured by Toyo Seiki Co., Ltd.: Type B1) measures the thickness at 5 locations and takes the average value of 15 points as the thickness of the nonwoven fabric or the current collector before polarization.

[0201] Breathability (cc / cm) 2 / Second)] According to JIS L 1096 6.27.1 (Method A: Frazier Method), three sample pieces identical to those prepared in the unit area weight determination were used. For each sample piece, an air permeability meter (TEXTEST FX3300, Switzerland) was used to measure the permeability at a measurement area of ​​38 cm². 2 The air permeability was measured under a pressure of 125 Pa, and the average air permeability of the three pieces was taken as the air permeability of the nonwoven fabric or current collector.

[0202] [Surface resistivity (Ω / □)] The surface resistance of the current collector was measured using a resistance meter (MULTIMETER3478A, Hewlett-Packard) according to JIS-K-7194, using the four-terminal four-probe method.

[0203] [Slurry viscosity] Regarding the viscosity of the slurry, a type B viscometer (DV2T, manufactured by Eiko Seiki Co., Ltd.) was used to measure the viscosity 2 minutes after the start of the measurement, under the conditions of 25°C, spindle CPA-52Z, and rotation speed of 5 rpm.

[0204] [Fill Rate] The electrode was cut to an appropriate size, embedded in G2 epoxy resin, and then truncated using CP. The cross-section of the electrode was observed at 2000x magnification under 15kV conditions using a scanning electron microscope (SU8200, manufactured by Hitachi High Tech Noroze Co., Ltd.). Next, from the obtained observation images, image analysis software (Digital Being Kids Co., Ltd.'s "PopImaging") was used to extract a projection image of the current collector, consistent only with the thickness of the current collector. Figure 2 ).

[0205] First, in the obtained current collector projection diagram, determine the highest and lowest positions of the projected portion of the current collector, and draw out the straight lines L1 and L2 that contain their respective positions and are orthogonal to the thickness direction. The distance between these straight lines is defined as the thickness of the current collector.

[0206] Next, determine the leftmost and rightmost positions of the projected portion of the current collector in the photograph, and draw out straight lines L3 and L4 parallel to the thickness direction that contain their respective positions. The distance between these straight lines is defined as the observation length of the current collector.

[0207] Furthermore, the observation area is calculated as the thickness of the current collector multiplied by the observation length.

[0208] In the observed area (α), a threshold is set to distinguish between the white portion and the rest of the area from the current collector, and binarization is performed, with the white portion being taken as the current collector portion. The area (γ) of the current collector portion is calculated based on the observed image obtained through image processing. Next, for the portion outside the current collector in the current collector projection image, a threshold is set to distinguish between the portion where active material is present and the portion where active material is absent, and binarization is performed to calculate the area (β) of the portion filled with active material.

[0209] Based on the observed image obtained through image processing, the value (α-γ) after removing the area (γ) of the current collector portion from the observed area (α) is equivalent to the area in the observed area that can be filled with active material.

[0210] Furthermore, the filling rate is calculated by using the following formula to determine the ratio of the area actually filled with active material (β) to the area in the observed area that can be filled with active material (α-γ). Additionally, the average value of the ratios obtained from the observed images at 5 points is used as the filling rate for each sample.

[0211] [Formula] Filling rate (%) = β / (α-γ) × 100 [Thickness of electrode and active material composition layer] Three sample pieces were used as electrodes for the coin cell. In each sample piece, based on JIS L1906, a 16mm diameter electrode with a weight of 20gf / cm was used. 2 The thickness of the electrode was measured at 3 points using a digital manometer (Toyo Seiki Co., Ltd.: Type B1), and the average value of the 9 points was taken as the electrode thickness.

[0212] In addition, the thickness of the active material component layer is calculated by subtracting the thickness of the current collector measured when the fill rate is measured from the electrode thickness.

[0213] [Electrode density] Electrode density is calculated by dividing the weight (g) of graphite mixed in the slurry by the volume (cm³) of the electrode produced during the manufacture of electrodes for coin batteries. 3 The value obtained (g / cm) 3 It should be noted that the electrode volume is calculated using the electrode thickness and the electrode diameter (14 mm).

[0214] [Fan drop] Observe the surface of the fabricated electrode and visually confirm whether there is any active material that has detached or fallen off from the current collector.

[0215] 〇: No active material was identified that detached or separated from the current collector.

[0216] ×: Active material that has been identified as detached or separated from the current collector.

[0217] [Example A1] ● Fabrication of the current collector (1) A melt-blown nonwoven fabric manufacturing apparatus is used to extrude a fully aromatic polyester (VECTRA-L manufactured by Polyplastics Co., Ltd.) formed by a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, with a melting point of 300°C and a melt viscosity of 15 Pa·s at 310°C. The polyester is formed by a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and the extrusion is fed into the apparatus. The apparatus has nozzles with a nozzle orifice diameter of 0.15 mm, L / D = 30, and an average number of 1500 orifices per 1 m width (the spacing between nozzle orifices is 0.67 mm). The apparatus operates at a single-orifice extrusion rate of 0.10 g / min, a resin temperature of 330°C, a hot air temperature of 330°C, and an average nozzle width of 18 Nm per 1 m. 3After spraying, a weight of 11 g / m² was obtained. 2 The nonwoven fabric was then heat-treated in air at 300°C for 6 hours. The resulting nonwoven fabric was then passed between a metal roller heated to 110°C and an elastic roller (manufactured by Riken Co., Ltd.) made of resin with a surface Shore D hardness of 86, and continuously processed using a pressure calender at a linear pressure of 120 kg / cm. The resulting area weight was 11 g / m² as described above. 2 Meltblown nonwoven fabric with an average fiber diameter of 5.1 μm.

[0218] (2) A palladium catalyst was applied to the surface of the meltblown nonwoven fabric obtained in (1) above. The fabric was then immersed in a non-electrolytic copper plating solution containing copper sulfate and potassium / sodium tartrate (Roschelle salt), followed by washing to form a copper coating on the nonwoven fabric surface. Next, the fabric was immersed in a nickel plating solution to electroplating copper, followed by washing and drying. This yielded a copper coating with an average opening diameter of 18.3 μm, a thickness of 46 μm, and an air permeability of 327 cc / cm², further laminated on top of the copper coating. 2 A conductive nonwoven fabric with a per second conductivity. This conductive nonwoven fabric is used as a current collector.

[0219] ● Fabrication of the electrode (negative electrode) <Preparation of Negative Electrode Slurry> 94 parts by weight of artificial graphite with a median diameter of 21.0 μm, 6 parts by weight of polyvinylidene fluoride (Kreha Corporation "KF Polymer #1120"), and NMP (N-methylpyrrolidone) were placed in a special container and mixed using a planetary mixer (ARE-250, manufactured by Shinki) to obtain a slurry.

[0220] <Making a Battery Negative Electrode> The obtained slurry was coated onto a current collector formed from the aforementioned conductive nonwoven fabric using a rod coater (T101, Matsuo Sangyo). After standing for 15 minutes, it was dried once at 86°C using a hot air dryer (Yamato Scientific) for 30 minutes. Next, it was calendered using a roll press (Hokusen). Then, after being punched as a battery electrode (diameter: 14 mm), it was subjected to reduced pressure at 120°C for 3 hours, followed by a second drying under these conditions to produce an electrode for a coin battery.

[0221] [Comparative Example] A1] Similar to Example A1 (1), the weight per unit area was 4 g / m². 2 A meltblown nonwoven fabric with an average fiber diameter of 2.8 μm was obtained. Using this nonwoven fabric, an air permeability of 204 cc / cm was obtained by the same method as in Example A1 (2). 2A conductive nonwoven fabric with a per second, a film thickness of 16 μm, and an average opening diameter of 10.1 μm was produced. This conductive nonwoven fabric was used as a current collector, and otherwise, a negative electrode for a battery was fabricated in the same manner as in Example A1.

[0222] [Comparative Example A2] Rolled copper foil (10 μm thick) is used as the current collector for the negative electrode. Otherwise, the negative electrode for the battery is made in the same manner as in Example A1.

[0223] [Example A2] As the nonwoven fabric, the meltblown nonwoven fabric of Comparative Example A1 was used, and 94 parts by weight of artificial graphite with a median diameter of 5.0 μm were used to prepare the negative electrode slurry. Otherwise, the negative electrode for the battery was prepared in the same manner as in Example A1.

[0224] <Battery Making> The electrodes of the battery obtained above were transferred to a glove box (manufactured by Miwa Seisakusho Co., Ltd.) under an argon atmosphere. A lithium metal foil (0.2 mm thick, φ15 mm) was used as the positive electrode. Polypropylene (Celgard #2400, manufactured by Polypore) was used as the separator. A mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of lithium hexafluorophosphate (LiPF6) with added vinylene carbonate (VC) (1M-LiPF6, EC / EMC / DMC = 3 / 3 / 4 vol%, VC 1 wt%) was injected to fabricate a coin cell (model 2032).

[0225] <Charge and Discharge Characteristics Test> For the manufactured coin batteries, charge-discharge tests were conducted using a commercially available charge-discharge testing machine (TOSCAT3100, manufactured by Toyo System). The coin batteries were placed in a constant temperature bath at 25°C, and during charging, they were charged at 0.2C (approximately 0.50 mA / cm²) relative to the mass of the active material. 2 The lithium battery was charged with a constant current until it reached 0V relative to the lithium potential. Then, a constant voltage of 0V was applied to the lithium potential until a current of 0.0385mA was reached. The capacity at this point was recorded as the charging capacity (mAh / g). Next, a 0.2C charge (approximately 0.50mA / cm²) was applied. 2 The battery is discharged at a constant current until it reaches 1.5V relative to the lithium potential, and the capacity at this point is taken as the discharge capacity (mAh / g). Furthermore, the discharge capacity multiplied by the electrode density is taken as the volumetric capacity. The percentage of discharge capacity to charge capacity is taken as the charge / discharge efficiency, which is an indicator of the utilization efficiency of lithium ions within the battery.

[0226] <Rate Characteristics Test> The coin cell used for the charge-discharge test was placed in a constant temperature bath at 25°C, and charging was performed at 0.2C (approximately 0.50 mA / cm²) relative to the mass of the active material. 2 A constant current is applied until the lithium potential reaches 0V, then a constant voltage charge of 0V is applied until a current of 0.0385mA is reached. Next, the lithium potential is subjected to a 0.5C charge (approximately 1.25mA / cm²). 2 Discharge at a constant current until 1.5V, and set the capacity at 0.4V as the 0.5C discharge capacity (mAh / g).

[0227] Then, the coin cell battery was charged again under the same conditions, and the lithium potential was tested at 3C (approximately 7.5 mA / cm). 2 Discharge the battery with a constant current until it reaches 1.5V, and set the capacity at 0.4V as the 3C discharge capacity (mAh / g). Then, calculate the capacity retention rate according to the following formula.

[0228] Capacity retention rate [%] = 3C discharge capacity / 0.5C discharge capacity × 100 The evaluation results of the physical properties of the current collector and the evaluation results of the electrode and battery characteristics in each embodiment and comparative example are shown in Tables 5 to 8 below.

[0229] As shown in Tables 5 to 8, in Comparative Example A1, although a current collector with a three-dimensional porous structure was used, the fill rate of the voids in the current collector was small because the median diameter of the active material relative to the average opening diameter of the current collector was large. As a result, the capacity retention rate (3C / 0.5C) of the battery was small, which was similar to the capacity retention rate (3C / 0.5C) of the battery in Comparative Example A2, which used rolled copper foil as the current collector.

[0230] On the other hand, in Examples A1 and A2, since a current collector with a three-dimensional porous structure is used and the median diameter of the active material relative to the average opening diameter of the current collector is controlled within a specified range, the capacity retention rate of the battery (3C / 0.5C) can be significantly improved compared with Comparative Examples A1 and A2.

[0231] [Example A3] ●Preparation of negative electrode active materials <Preparation of carbon precursors> Coconut shells were crushed. 100g of coconut shell char (containing 98% by weight of particles with a diameter of 0.850–2.360 mm) obtained by dry distillation at 500°C was fed with nitrogen gas containing 1% by volume hydrogen chloride at a flow rate of 10 L / min and treated at 950°C for 80 minutes. Then, the hydrogen chloride gas supply was stopped, and the mixture was heat-treated at 950°C for another 30 minutes. Next, the mixture was coarsely pulverized to an average particle size of 10 μm using a ball mill, followed by further pulverization using a small jet mill (Seishin Corporation, "Coating System α-mkIII"). Finally, the mixture was classified using a LABO CLASSIELN-01 (Seishin Corporation, Ltd.) to obtain a specific surface area of ​​400 m². 2 / g, carbon precursor with a specified particle size.

[0232] <Production of Carbonaceous Materials> 0.9 g of polystyrene (manufactured by Sekisui Chemicals Co., Ltd., average particle size 400 μm, char residue 1.2%) was mixed with 9.1 g of carbon precursor. 10 g of the mixture was placed in a high-speed heating furnace manufactured by Motoyama Co., Ltd., and heated to 1290 °C at a nitrogen flow rate of 6 L / min. This temperature was maintained for 10 minutes, followed by natural cooling. Once the furnace temperature was confirmed to have dropped below 200 °C, the carbonaceous material was removed from the furnace, thus obtaining hard carbon (median diameter D) which became the negative electrode active material. 50 (1.3μm).

[0233] Hard carbon, obtained as the negative electrode active material and used in place of artificial graphite, is otherwise used to manufacture the negative electrode and battery in the same manner as in Example A2.

[0234] [Examples A4, A5, A6] As the negative electrode active material, hard carbon with a median diameter as shown in Table 10 was used. Otherwise, the negative electrode and battery were made in the same manner as in Example A3.

[0235] [Comparative Example A3] The meltblown nonwoven fabric prepared in Example A1 is used as the nonwoven fabric. Otherwise, the negative electrode and battery are prepared in the same manner as in Example A3.

[0236] The physical properties of the current collector, the evaluation results of the physical properties of the active material and the slurry, and the evaluation results of the electrode and battery characteristics in each embodiment and comparative example are shown in Tables 9 to 12 below.

[0237] As shown in Tables 9 to 12, in Examples A3 to A6, regardless of the median diameter of the active material, since the median diameter of the active material relative to the average opening diameter of the current collector is controlled within a specified range, the capacity retention rate (3C / 0.5C) of the battery can be 90% or more.

[0238] On the other hand, in Comparative Example A3, although a current collector with a three-dimensional porous structure was used, the capacity retention rate was low compared with Examples A3 to A6 because the median diameter of the active material relative to the average opening diameter of the current collector was small. Therefore, even though the same active material as in Example A3 was used, the capacity retention rate was low.

[0239] [Example A7] ● Fabrication of current collector (Al plating) (2) Both sides of the fiber surface of the meltblown nonwoven fabric obtained in Example 1 (1) were coated with Al by vapor deposition. An Al coating with a thickness of 16 μm and an air permeability of 204 cc / cm was obtained. 2 Conductive nonwoven fabric per second.

[0240] ● Fabrication of the electrode (positive electrode) <Preparation of Cathode Slurry> Using a planetary stirrer (ARE-250, manufactured by Shinki Co., Ltd.), N-methylpyrrolidone was added appropriately while mixing to adjust the slurry viscosity to approximately 1500 mPa·s, thus preparing a slurry for the positive electrode. Three parts by weight of polyvinylidene fluoride (KF polymer 1700 manufactured by Kraha Co., Ltd.) were added as a binder, and LiNi with a median diameter of 10 μm was added as the positive electrode active material. 1 / 3 Co 1 / 3 MN 1 / 3 93 parts by weight of O2 (Selcid C-5H manufactured by Nippon Chemical Industries, Ltd.) and 2 parts by weight of Super-P (Timcal Corporation) added as a conductive material. That is, the composition ratio of active material, conductive additive and binder in the positive electrode slurry, based on solid components, is NCM powder: conductive additive: binder = 95:2:3 (mass ratio).

[0241] <Making the Positive Electrode for Batteries> The obtained slurry was coated onto a current collector formed from the aforementioned conductive nonwoven fabric using a rod coater (T101, Matsuo Sangyo). After standing for 5 minutes, it was transferred to a hot plate heated to 80°C for a first drying of 30 minutes. Next, it was calendered using a roll press (Hosen). Then, after being punched as a battery electrode (diameter: 15mm), it was subjected to reduced pressure at 140°C for 3 hours, and a second drying under these conditions was performed to produce an electrode for a coin battery.

[0242] [Comparative Example A4] Aluminum foil (20 μm thick) is used as the current collector for the positive electrode. Otherwise, the positive electrode for the battery is made in the same manner as in Example A7.

[0243] <Battery Making> The electrodes of the battery obtained above were transferred to a glove box (manufactured by Miwa Seisakusho Co., Ltd.) under an argon atmosphere. A lithium metal foil (0.2 mm thick, φ15 mm) was used as the negative electrode. Glass fiber nonwoven fabric (TGP-020A, manufactured by Nippon Sheet Glass Co., Ltd.) was used as the separator. A mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of lithium hexafluorophosphate (LiPF6) with added vinylene carbonate (VC) (1M-LiPF6, EC / EMC / DMC = 1 / 1 / 1 vol%, VC 1 wt%) was injected to fabricate a coin battery (Type 2032).

[0244] <Charge and Discharge Characteristics Test> For the coin-shaped battery, charge-discharge tests were conducted using a commercially available charge-discharge testing machine (TOSCAT3100, Toyo System). The coin-shaped battery was placed in a 25°C constant temperature bath, and the lithium potential was tested at 0.2C (approximately 0.70 mA / cm²). 2 A constant current discharge was applied until 4.2V, and the capacity at this point was taken as the charging capacity (mAh / g). Next, a charge was applied at 0.2C (approximately 0.70 mA / cm²) relative to the weight of the active material. 2 The battery is discharged at a constant current until it reaches 3.0V relative to the lithium potential, and the capacity at this point is taken as the discharge capacity (mAh / g). Furthermore, the discharge capacity multiplied by the electrode density is taken as the volumetric capacity. The percentage of discharge capacity to charge capacity is taken as the charge / discharge efficiency, which is an indicator of the utilization efficiency of lithium ions within the battery.

[0245] <Discharge Rate Characteristics Test> The coin cell used for the charge-discharge test was placed in a constant temperature bath at 25°C, and charging was performed at 0.2C (approximately 0.70 mA / cm²) relative to the weight of the active material. 2 The lithium battery is charged with a constant current until it reaches 4.2V relative to the lithium potential. Then, the lithium potential is subjected to a constant current of 0.5C (approximately 1.75mA / cm). 2 Discharge at a constant current until 3.0V, and set the capacity at 3.0V as the 0.5C discharge capacity (mAh / g).

[0246] Then, the coin cell battery was charged again under the same conditions, and the lithium potential was tested at 3C (approximately 10.5 mA / cm). 2Discharge the battery with a constant current until it reaches 3.0V, and set the capacity at 3.0V as the 3C discharge capacity (mAh / g). Then, calculate the capacity retention rate according to the following formula.

[0247] Capacity retention rate [%] = 3C discharge capacity / 0.5C discharge capacity × 100 The physical properties of the current collector and the evaluation results of the physical properties of the active material and the slurry in Example A7 and Comparative Example A4, as well as the evaluation results of the electrode and battery characteristics, are shown in Tables 13 to 16 below.

[0248] As shown in Tables 13-16, in Example A7, the median diameter of the active material relative to the average opening diameter of the current collector was controlled within a specified range, and the fill rate was also large. Therefore, compared with Comparative Example A4, which used aluminum foil as the current collector, the capacity retention rate was greater.

[0249] [Example B1] ● Fabrication of the current collector (1) A melt-blown nonwoven fabric manufacturing apparatus is used to extrude a fully aromatic polyester (VECTRA-L manufactured by Polyplastics Co., Ltd.) formed by a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, with a melting point of 300°C and a melt viscosity of 15 Pa·s at 310°C. The polyester is formed by a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, and the extrusion is fed into the apparatus. The apparatus has nozzles with a nozzle orifice diameter of 0.15 mm, L / D = 30, and an average number of 1500 orifices per 1 m width (the spacing between nozzle orifices is 0.67 mm). The apparatus operates at a single-orifice extrusion rate of 0.10 g / min, a resin temperature of 330°C, a hot air temperature of 330°C, and an average nozzle width of 18 Nm per 1 m. 3 The spraying process yielded a weight of 4 g / m². 2 The nonwoven fabric was then heat-treated in air at 300°C for 6 hours. The resulting nonwoven fabric was then passed between a metal roller heated to 110°C and an elastic roller (manufactured by Riken Co., Ltd.) made of resin with a surface Shore D hardness of 86 degrees, and continuously processed using a pressure calender at a linear pressure of 120 kg / cm. The resulting area weight was 4 g / m² as described above. 2 Meltblown nonwoven fabric with an average fiber diameter of 2.8 μm.

[0250] (2) A palladium catalyst was applied to the surface of the meltblown nonwoven fabric obtained in (1) above. The fabric was then immersed in a non-electrolytic plating solution containing copper sulfate and potassium / sodium tartrate (Roschelle salt), followed by water washing to form a copper coating on the nonwoven fabric surface. Next, the fabric was immersed in a nickel plating solution to electroplating and coat it with copper. After washing and drying, a copper coating with a thickness of 16 μm and an air permeability of 204 cc / cm² was further laminated onto the copper coating. 2 A conductive nonwoven fabric with a per second conductivity. This conductive nonwoven fabric is used as a current collector.

[0251] ● Fabrication of the electrode (negative electrode) <Preparation of Negative Electrode Slurry> 96.5 parts by weight of artificial graphite with a median diameter of 5.0 μm, 2.0 parts by weight of styrene-butadiene rubber (SBR: JSR Corporation, "TRD2001"), 1.0 part by weight of carboxymethyl cellulose (CMC: Daiichi Kogyo Pharmaceutical Co., Ltd., "SerogenBSH-6"), and 0.5 parts by weight of carbon black (CB: MTI Corporation, "Super P") were mixed with 106.3 parts by weight of deionized water. Then, 2.1 parts by weight of ethanol (Fuji Film & Water Purification Co., Ltd., "Ethanol (99.5)") was added as a surface conditioner to this mixture, resulting in a slurry with a viscosity of approximately 3000 mPa·s (ethanol to total slurry weight ratio: 1 wt%). It should be noted that the solvent in the obtained slurry is referred to as an aqueous solvent (water containing 1 wt% ethanol).

[0252] <Making the Negative Terminal for Batteries> The obtained slurry was coated onto a current collector formed from the aforementioned conductive nonwoven fabric using a rod coater (T101, Matsuo Sangyo). After standing for 15 minutes, it was dried for 30 minutes at a time using a hot air dryer (Yamato Scientific) at 86°C. Next, it was calendered using a roll press (Hokusen). Then, after being punched as a battery electrode (diameter: 14 mm), it was subjected to reduced pressure at 120°C for 3 hours, followed by a second drying under these conditions to produce an electrode for a coin battery.

[0253] [Example B2] The negative electrode for the battery was prepared in the same manner as in Example B1 (2), with 104.2 parts by weight of ion-exchanged water and 4.2 parts by weight of ethanol ("ethanol (99.5)" manufactured by Fuji Thin Film and Koi Chemical Co., Ltd.) and an aqueous solvent (water containing 2 wt% ethanol) as the solvent for the slurry.

[0254] [Example B3] In Example B1, the negative electrode for the battery was prepared in the same manner as in Example B1, using 97.9 parts by weight of ion-exchanged water, 10.4 parts by weight of ethanol ("ethanol (99.5)" manufactured by Fuji Thin Film and Koi Chemical Co., Ltd.), and an aqueous solvent (water containing 5 wt% ethanol) as the solvent for the slurry.

[0255] [Example B4] The same as in Example B1 (1) was prepared with a unit area weight of 11 g / m². 2 A meltblown nonwoven fabric with an average fiber diameter of 5.1 μm was used, and an aqueous solvent (water containing 5 wt% ethanol) was used as the solvent for the slurry. Otherwise, the negative electrode for the battery was manufactured in the same manner as in Example B1. As the nonwoven fabric, the meltblown nonwoven fabric of Example B9 was used, and 94 parts by weight of artificial graphite with a median diameter of 5.0 μm were used to prepare the negative electrode slurry. Otherwise, the negative electrode for the battery was manufactured in the same manner as in Example B1.

[0256] [Example B5] In Example B1, the ion-exchanged water was 108.1 parts by weight, the defoamer was 0.2 parts by weight, and an aqueous solvent (water containing 0.1 wt% defoamer) was used as the solvent for the slurry. Otherwise, the negative electrode for the battery was manufactured in the same manner as in Example B1. It should be noted that "NoPeptex E-D54" manufactured by Sunopco Co., Ltd. was used as the defoamer.

[0257] [Example B6] In Example B1, the amount of ion-exchanged water was 108.3 parts by weight, and no ethanol was added during mixing. Otherwise, a negative electrode slurry was prepared in the same manner as in Example B1. The resulting slurry was applied to the current collector obtained in Example B1 by impregnation. Otherwise, a battery negative electrode was prepared in the same manner as in Example B1. During impregnation, degassing was performed using ultrasound.

[0258] [Example B7] When preparing the negative electrode slurry, 100 parts by weight of artificial graphite with a median diameter of 5.0 μm and 3.125 parts by weight of a 10 wt% aqueous solution of polyvinyl alcohol (PVA215 (manufactured by Kuraray Co., Ltd.): degree of polymerization 1700 degree of saponification 88) were added to make the slurry viscosity approximately 10000 mPa·s. The resulting slurry was used to prepare the negative electrode for the battery in the same manner as in Example B1.

[0259] [Example B8] In preparing the negative electrode slurry, 100 parts by weight of artificial graphite with a median diameter of 5.0 μm and 3.125 parts by weight of a 10 wt% aqueous solution of polyvinyl alcohol (PVA235 (manufactured by Kuraray Co., Ltd.): degree of polymerization 3500, degree of saponification 88) were added to the slurry with a viscosity of approximately 3000 mPa·s. The resulting slurry was used to prepare the negative electrode for the battery in the same manner as in Example B1.

[0260] [Example B9] When preparing the negative electrode slurry, 100 parts by weight of artificial graphite with a median diameter of 5.0 μm and 3.125 parts by weight of a 10 wt% aqueous solution of polyvinyl alcohol (PVA235 (manufactured by Kuraray Co., Ltd.): degree of polymerization 3500 degree of saponification 88) were added to make the slurry viscosity approximately 10000 mPa·s. The resulting slurry was used to prepare the negative electrode for the battery in the same manner as in Example B1.

[0261] [Example B10] The slurry viscosity was set to approximately 10,000 Pa·s. Otherwise, the negative electrode for the battery was prepared in the same manner as in Example B2.

[0262] [Example B11] In Example B1, the amount of ion-exchanged water was set at 108.3 parts by weight, and no ethanol was added during the mixing process. Otherwise, the negative electrode for the battery was prepared in the same manner as in Example B1.

[0263] [Comparative Example B1] Rolled copper foil (10 μm thick) is used as the current collector for the negative electrode. Otherwise, the negative electrode for the battery is fabricated in the same manner as in Example B5.

[0264] [Comparative Example B2] The particle size of the artificial graphite was adjusted to 21 μm, otherwise the slurry was adjusted in the same manner as in Example B9. The viscosity of the slurry at this time was approximately 3000 Pa. Using this slurry, a negative electrode for a battery was fabricated in the same manner as in Example B1.

[0265] <Battery Making> The electrodes of the battery obtained above were transferred to a glove box (manufactured by Miwa Seisakusho Co., Ltd.) under an argon atmosphere. A lithium metal foil (0.2 mm thick, φ15 mm) was used as the positive electrode. Polypropylene (Celgard #2400, manufactured by Polypore) was used as the separator. A mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of lithium hexafluorophosphate (LiPF6) with added vinylene carbonate (VC) (1M-LiPF6, EC / EMC / DMC = 3 / 3 / 4 vol%, VC 1 wt%) was injected to fabricate a coin cell (model 2032).

[0266] <Charge and Discharge Characteristics Test> For the coin batteries produced, charge-discharge tests were conducted using a commercially available charge-discharge testing machine (TOSCAT3100, manufactured by Toyo System). The coin batteries were placed in a constant temperature bath at 25°C, and charging was performed at 0.2C (approximately 0.50 mA / cm²) relative to the weight of the active material. 2 The lithium battery was charged with a constant current until it reached 0V relative to the lithium potential, and then charged with a constant voltage of 0V relative to the lithium potential until it reached a current of 0.0385mA. The capacity at this point was recorded as the charging capacity (mAh / g). Next, the charge was applied at 0.2C relative to the lithium potential (approximately 0.50mA / cm). 2 The battery is discharged at a constant current until it reaches 1.5V, and the capacity at this point is taken as the discharge capacity (mAh / g). Furthermore, the discharge capacity multiplied by the electrode density is taken as the volumetric capacity. The percentage of discharge capacity to charge capacity is taken as the charge / discharge efficiency, which is an indicator of the utilization efficiency of lithium ions within the battery.

[0267] <Discharge Rate Characteristics Test> The coin cell battery used for the charge-discharge test was placed in a constant temperature bath at 25°C, and charging was performed at 0.2C (approximately 0.50 mA / cm²) relative to the weight of the active material. 2 A constant current is applied until the lithium potential is 0V, then a constant voltage of 0V is applied until a current of 0.0385mA is applied relative to the lithium potential. Next, a current of 0.5C (approximately 1.25mA / cm²) is applied to the lithium potential. 2 Discharge at a constant current until 1.5V, and set the capacity at 0.4V as the 0.5C discharge capacity (mAh / g).

[0268] Then, the coin cell battery was charged again under the same conditions, and the lithium potential was tested at 3C (approximately 7.5 mA / cm). 2 Discharge the battery with a constant current until it reaches 1.5V, and set the capacity at 0.4V as the 3C discharge capacity (mAh / g). Then, calculate the capacity retention rate according to the following formula.

[0269] Capacity retention rate [%] = 3C discharge capacity / 0.5C discharge capacity × 100 The evaluation results of the physical properties of the current collector and the evaluation results of the electrode and battery characteristics in each embodiment and comparative example are shown in Tables 17 to 20 below.

[0270] [Table 17] .

[0271] [Table 18] .

[0272] [Table 19] .

[0273] [Table 20] .

[0274] In Comparative Example B1, since copper foil is used as the current collector, the volumetric capacity of the initial charge-discharge characteristics and the capacity retention rate of the discharge rate characteristics cannot be improved.

[0275] Comparative Example B2 corresponds to Example 3 of Patent Document 1, but the median diameter D of the active material relative to the average opening diameter of the current collector is different. 50 The current collector has a fill rate of 35%, which cannot improve the volumetric capacity of the initial charge / discharge characteristics or the capacity retention rate of the discharge rate characteristics.

[0276] In contrast, as shown in Tables 17 to 20, in Examples B1 to B11, the charging capacity can be significantly improved by reducing the particle size of graphite, which is the active material.

[0277] However, the capacity retention rate of Examples B9 to B11, where the current collector fill rate is less than 45%, remains less than 80%, while Examples B1 to B8, with a fill rate of more than 45%, show a higher value of capacity retention rate of more than 80%.

[0278] In Example B9, not only is the slurry viscosity high, but the surface tension of the slurry is also high. Therefore, the filling rate into the current collector cannot be increased, and the capacity retention rate in the initial charge-discharge characteristics and discharge rate characteristics cannot be increased to the level of Examples B1 to B9.

[0279] In Example B10, although an aqueous solvent mixed with ethanol was used to reduce surface tension, the high viscosity of the slurry prevented the increase in the filling rate into the current collector and the improvement in the volumetric capacity of the initial charge-discharge characteristics and the capacity retention rate of the discharge rate characteristics to the level of Examples B1 to B9.

[0280] In Example B11, although the viscosity of the slurry was reduced, the high surface tension of the slurry prevented the increase in the filling rate into the current collector and the increase in the volumetric capacity of the initial charge-discharge characteristics and the capacity retention rate of the discharge rate characteristics to the level of Examples B1 to B9.

[0281] In contrast, in Examples B1 to B5, since the slurry viscosity and surface tension are adjusted, the fill rate in the current collector can be made to be 45% or more. As a result, the volumetric capacity of the initial charge-discharge characteristics can be further improved, and the capacity retention rate in the discharge rate characteristics can be improved.

[0282] In Example B6, even when using the same slurry as in Example B10, by applying ultrasonic waves while impregnating the slurry during application, the filling rate can be increased compared to Example B10. As a result, the volumetric capacity of the initial charge-discharge characteristics can be increased, and the capacity retention rate in the discharge rate characteristics can be improved.

[0283] Furthermore, in Example B7, by reducing the molecular weight of the binder component, and in Example B8, by reducing the concentration of the binder component in the slurry, the filling rate can be increased compared to Example B11, even under conditions of high surface tension in the slurry. As a result, the volumetric capacity of the initial charge-discharge characteristics can be improved, and the capacity retention rate in the discharge rate characteristics can be improved. However, in Examples B6 and B7, a small amount of powdering occurred due to the low viscosity of the binder component.

[0284] The above embodiments illustrate the application of the electrode of the present invention in the negative electrode of a button cell, but the present invention is not limited thereto. The electrode of the present invention can also be applied in the positive electrode of a button cell instead of the above-described case. Furthermore, the non-aqueous electrolyte battery is not limited to a "button cell" and can also be manufactured in other shapes such as cylindrical.

[0285] In addition, in the above embodiments, the electrolyte is set to a liquid state, but it is not limited to this, and other forms of electrolytes such as gels can also be used.

[0286] Industrial applicability The electrode of the present invention can improve the capacity retention of various electrochemical devices, such as mobile terminals like smartphones and laptops, and various vehicles (e.g., electric vehicles and hybrid vehicles) that use electrochemical devices as power supply units.

[0287] As described above, preferred embodiments of the present invention have been illustrated. Those skilled in the art, upon reading this specification, will readily conceive of various modifications and alterations within their apparent scope. Therefore, such modifications and alterations can be interpreted as falling within the scope of the invention as defined by the claims.

[0288] Explanation of reference numerals in the attached figures 1 Current collector 2. Active substances 3 gaps 4 Positive electrode 4a Positive current collector 4b Positive electrode active material composition layer 5. Negative electrode 5a Negative current collector 5b Negative electrode active material composition layer 6. Partition.

Claims

1. An electrode comprising a current collector and an active material, wherein the current collector has a three-dimensional porous structure with an average opening diameter A, and the active material has a median diameter (D). 50 B, the aforementioned average opening diameter A (μm) and the aforementioned median diameter (D) 50 B(μm) satisfies the following relationship (1), 0.10≤B / A≤2.00 (1).

2. The electrode according to claim 1, wherein, The aforementioned current collector is filled with an active material component containing the aforementioned active material, and the filling rate (%) specified in the following formula (2) is 37% or more. Fill rate (%) = β / (α-γ) × 100 (2) In the formula, α represents the observation area, which is determined by the thickness of the current collector × the observation length, based on an electron microscope image of the cross-section in the electrode thickness direction. β and γ represent the projected areas of the active material and the current collector, respectively, calculated using image analysis software within the observation area.

3. An electrode having a current collector having a three-dimensional porous structure, wherein the current collector is filled with an active material component containing an active substance, and the filling rate (%) specified by the following formula (2) is 37% or more. Fill rate (%) = β / (α-γ) × 100 (2) In the formula, α represents the observation area, which is determined by the thickness of the current collector × the observation length, based on an electron microscope image of the cross-section in the electrode thickness direction. β and γ represent the projected areas of the active material and the current collector, respectively, calculated using image analysis software within the observation area.

4. The electrode according to claim 3, wherein, The aforementioned fill rate is above 45%.

5. The electrode according to any one of claims 1 to 4, wherein, The thickness of the aforementioned current collector is less than 100 μm.

6. The electrode according to any one of claims 1 to 4, wherein, The air permeability of the aforementioned current collector is 0.1~600cc / cm. 2 / Second.

7. The electrode according to any one of claims 1 to 4, wherein, The aforementioned current collector comprises a non-conductive structure and a metal coating.

8. The electrode according to claim 7, wherein, The aforementioned non-conductive structure comprises an aggregate of fibers with an average fiber diameter of less than 10 μm.

9. The electrode according to claim 8, wherein, The aforementioned fiber assembly is a nonwoven fabric.

10. The electrode according to claim 7, wherein, The aforementioned metal coating comprises at least one metal selected from aluminum, copper, nickel, gold, and silver.

11. The electrode according to any one of claims 1 to 4, wherein, The aforementioned active substances can absorb and release electrolyte ions.

12. The electrode according to any one of claims 1 to 4, wherein, The aforementioned electrodes further comprise a conductive material.

13. The electrode according to any one of claims 2 to 4, wherein, The median diameter of the aforementioned active substances is 0.1~16μm.

14. The electrode according to any one of claims 2 to 4, wherein, The aforementioned active ingredients include non-water-soluble binders.

15. A method for manufacturing an electrode according to claim 1 or 2, comprising at least the steps of: preparing a current collector having a three-dimensional porous structure with an average opening diameter A, and... For the aforementioned process of forming an active material layer containing an active material with a median diameter B in the current collector, the aforementioned average opening diameter A and the aforementioned median diameter B satisfy the aforementioned equation (1).

16. The method for manufacturing an electrode according to any one of claims 2 to 4, comprising at least a step of filling a current collector having a three-dimensional porous structure with an active material component.

17. The method for manufacturing an electrode according to claim 16, wherein, The air permeability of the aforementioned current collector before being filled with active material components is 0.1~600cc / cm. 2 / Second.

18. The method for manufacturing an electrode according to claim 16, wherein, The thickness of the current collector before filling with active material components is less than 100 μm.

19. An electrochemical device comprising the electrode according to any one of claims 1 to 14.

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