Electrode for lithium ion secondary battery, method for producing same, and lithium ion secondary battery

Abstract

An electrode for a lithium ion secondary battery including a current collector, a plurality of intermediate sections disposed on the current collector in an island shape and including a first binder, and a mixture layer disposed on the current collector and on the plurality of intermediate sections, wherein when viewed from the thickness direction of the electrode, the average distance between the peripheral edges of adjacent intermediate sections is 30-250 μm, the area S of each of the plurality of intermediate sections is 5000 μm2 to 150,000 μm2 inclusive, the mixture layer contains graphite and a second binder, and the ratio of the peak intensity corresponding to the (110) plane to the peak intensity corresponding to the (002) plane in the X-ray diffraction pattern of the graphite is 0.0040 or more.

Description

Electrode for lithium ion secondary battery, manufacturing method thereof, and lithium ion secondary battery

[0001] The present invention relates to an electrode for a lithium ion secondary battery, a method for producing the same, and a lithium ion secondary battery.

[0002] Known electrodes for lithium-ion secondary batteries include an electrode in which a composite layer containing an active material and a binder is provided on a current collector. Examples of methods for producing the composite layer include a method in which a slurry containing at least an active material and a binder dispersed in a solvent is applied to the current collector and then dried; a method in which composite particles containing at least an active material and a binder are formed into a layer on the current collector and the resulting layer is compressed; and a method in which an amorphous kneaded material containing at least an active material and a binder is compressed multiple times with a calendar roll, and then attached to the current collector and compressed. Furthermore, electrodes in which a binder layer having a predetermined pattern is provided between the current collector and the composite layer are also known (see, for example, Patent Documents 1 to 5). Also known are electrodes in which particulate binder is dispersed between the current collector and the composite layer (see, for example, Patent Document 6).

[0003] JP 2016-100303 A (Corresponding Publication: U.S. Patent Application Publication No. 2017 / 279114) JP 2014-78497 A JP 2015-106525 A JP 2014-199738 A JP 2013-012393 A (Corresponding Publication: U.S. Patent Application Publication No. 2013 / 004843) JP 2023-082849 A (Corresponding Publication: U.S. Patent Application Publication No. 2023 / 178738)

[0004] Electrodes having a composite layer provided on a current collector tend to lack a binder between the current collector and the composite layer, resulting in insufficient adhesion strength between the current collector and the composite layer. Therefore, a layer containing a binder may be provided between the current collector and the composite layer. In particular, in manufacturing methods for electrodes using solid materials such as composite particles or amorphous kneaded materials, the adhesion strength between the current collector and the composite layer is particularly insufficient, unlike when the slurry is applied to a current collector and then dried to produce an electrode. Therefore, it is useful to provide a layer containing a binder between the current collector and the composite layer entirely or partially. Generally, binders have electrical insulating properties. Therefore, in order to ensure electrical conductivity between the current collector and the composite layer, it is considered to provide a layer containing a binder partially between the current collector and the composite layer. However, when the binder layer provided between the current collector and the composite layer is in a striped or grid pattern, as in the techniques of Patent Documents 1 to 5, the battery may suddenly deteriorate when rapidly charging, i.e., when charging at a high time rate. Patent Documents 4 and 5 also propose a dot-shaped binder layer provided between the current collector and the composite layer, but this may not achieve both rapid charging performance and cycle characteristics. As in the technique of Patent Document 6 (JP 2023-082849 A), when a small amount or fine particulate binder is dispersed between the current collector and the composite layer, the dispersed particulate binder may not be able to withstand the volume change of the composite layer during charge / discharge cycles. As a result, the composite layer may not be able to be retained on the current collector, and the composite layer may peel off from the current collector. In particular, in the case of an element having a structure in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, the pressure that constrains the stacked structure of the element is low, so that when the composite layer peels off from the current collector, the deterioration of battery characteristics tends to be significant.

[0005] Therefore, there is a need for an electrode for a lithium ion secondary battery that can achieve both excellent rapid charging performance and cycle characteristics in a lithium ion secondary battery; a method for manufacturing such an electrode for a lithium ion secondary battery; and a lithium ion secondary battery that can achieve both excellent rapid charging performance and cycle characteristics.

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems. The inventors have inferred the following reason why the rapid charging performance of a battery tends to be low when the binder layer provided between the current collector and the composite layer has a striped or lattice pattern. As described above, binders generally have electrical insulation properties. When the binder layer provided between the current collector and the composite layer has a striped pattern, it is thought that a conductive path is formed from the current collector to the composite layer so as to avoid the striped binder layer. That is, it is thought that a conductive path is less likely to be formed in the binder layer in the direction in which the striped pattern extends. On the other hand, it is thought that a conductive path is more likely to be formed in the composite layer located above the binder layer in the direction perpendicular to the direction in which the striped pattern extends. Therefore, when an electrode using graphite as an active material, whose potential at which an electrochemically reversible reaction occurs is close to the redox potential of metallic lithium, is used as the negative electrode of a lithium-ion secondary battery and a high-time-rate electrochemical reaction, such as rapid charging, is performed, it is thought that the reaction at the electrode will become non-uniform. It is thought that the battery will then suddenly deteriorate due to events such as the deposition of metallic lithium on the negative electrode, resulting in a decrease in battery performance. When the binder layer has a lattice pattern, as in the case of a stripe pattern, it is thought that a conductive path is unlikely to be formed in the direction in which the lattice pattern extends, and therefore the battery will similarly suddenly deteriorate and its performance will decrease.

[0007] The present inventors have further investigated based on the above speculation and have completed the present invention.

[0008] <1> An electrode for a lithium ion secondary battery, comprising: a current collector; a plurality of intermediate portions arranged in an island shape on the current collector and including a first binder; and a composite layer arranged on the current collector and the plurality of intermediate portions, wherein, when viewed in a thickness direction of the electrode, an average distance between peripheries of the plurality of intermediate portions adjacent to each other is 30 μm or more and 250 μm or less, and an area S of each of the plurality of intermediate portions is 5000 μm. ２ 150000 μm or more ２or less, wherein the composite layer contains graphite and a second binder, and the graphite has an X-ray diffraction pattern in which the ratio of the peak intensity corresponding to the (110) plane to the peak intensity corresponding to the (002) plane is 0.0040 or more. <2> The lithium ion secondary battery electrode according to <1>, wherein the composite layer further contains a silicon atom-containing active material. <3> The lithium ion secondary battery electrode according to <1> or <2>, which is a negative electrode. <4> A lithium ion secondary battery comprising the lithium ion secondary battery electrode according to <3> and a positive electrode. <5> During 10-hour rate discharge, the discharge capacity per unit area of ​​a portion where the lithium ion secondary battery electrode serving as the negative electrode and the positive electrode face each other is 3.3 mAh / cm ２ <6> A method for producing an electrode for a lithium ion secondary battery, wherein the electrode includes a current collector, a plurality of intermediate portions arranged on the current collector in an island shape and containing a first binder, and a composite layer arranged on the current collector and the plurality of intermediate portions and containing an active material and a second binder, the average distance between edges of the plurality of intermediate portions adjacent to each other when viewed in a thickness direction of the electrode being 30 μm or more and 250 μm or less, and the area S of each of the plurality of intermediate portions is 5000 μm or more. ２ 150000 μm or more ２ The method for producing an electrode for a lithium ion secondary battery is as follows: the method for producing an electrode for a lithium ion secondary battery includes: a step (1) of applying a binder composition containing the first binder in an island pattern on the current collector to obtain a first intermediate body having the plurality of intermediate portions formed thereon; a step (2) of supplying composite particles containing the active material and the second binder onto the current collector and the plurality of intermediate portions of the first intermediate body to form a composite particle layer; and a step (3) of applying pressure to the composite particle layer to form the mixture layer and obtain the electrode.

[0009] According to the present invention, it is possible to provide an electrode for a lithium ion secondary battery that can achieve both excellent rapid charge performance and cycle characteristics in a lithium ion secondary battery; a method for manufacturing such an electrode for a lithium ion secondary battery; and a lithium ion secondary battery that can achieve both excellent rapid charge performance and cycle characteristics.

[0010] Fig. 1 is a schematic diagram of a lithium ion secondary battery electrode according to embodiment A1, viewed from the thickness direction of the electrode. Fig. 2 is a schematic diagram of a cross section taken along line II-II in Fig. 1. Fig. 3 is a schematic diagram for explaining an intermediate portion adjacent to a certain intermediate portion M1.

[0011] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be modified as desired without departing from the scope of the claims of the present invention and their equivalents. The components of the embodiments shown below can be combined as appropriate. For example, any numerical value selected from a group of numerical values ​​listed as lower limits can be combined with any numerical value selected from a group of numerical values ​​listed as upper limits. Furthermore, in the drawings, identical components are denoted by the same reference numerals, and their description may be omitted.

[0012] In the following description, unless otherwise specified, the term "(meth)acrylic acid" includes acrylic acid, methacrylic acid, and combinations thereof; the term "(meth)acrylate" includes acrylate, methacrylate, and combinations thereof; the term "(meth)acrylic acid ester" includes acrylic acid ester, methacrylic acid ester, and combinations thereof; the term "(meth)acrylamide" includes acrylamide, methacrylamide, and combinations thereof; and the term "(meth)acryloyl" includes acryloyl, methacryloyl, and combinations thereof.

[0013] In the following description, the structure of a structural unit possessed by a polymer may be represented by writing "monomer unit" immediately after the name of a monomer capable of forming the repeating unit by polymerization. For example, a structural unit that can be formed by polymerizing a (meth)acrylic acid ester is also referred to as a "(meth)acrylic acid ester monomer unit." However, the term "monomer unit" is not limited to the polymerization method by which the monomer unit is obtained, and may represent a structural unit obtained by any polymerization method. The structural unit may be a repeating unit.

[0014] In the following description, unless otherwise specified, the "median diameter D50" of a particle means the particle diameter at which the integrated value accumulated from the small diameter side reaches 50% in the volume-based cumulative particle diameter distribution measured by a laser diffraction / light scattering method.

[0015] In the following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effects of the present invention, for example, within a range of ±3°, ±2°, or ±1°.

[0016] In the following description, unless otherwise specified, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as carriers for charge transfer between the positive electrode and the negative electrode.

[0017] <1. Electrode for Lithium-Ion Secondary Battery> <1.1. Overview of Electrode for Lithium-Ion Secondary Battery> A lithium-ion secondary battery electrode according to one embodiment of the present invention includes a current collector, a plurality of intermediate portions arranged in an island shape on the current collector and containing a first binder, and a composite layer arranged on the current collector and the plurality of intermediate portions. The lithium-ion secondary battery electrode according to this embodiment also has an average distance between the peripheries of the plurality of intermediate portions adjacent to each other, when viewed in the thickness direction of the electrode, of 30 μm or more and 250 μm or less, and an area S of each of the plurality of intermediate portions is 5000 μm or less. ２ 150000 μm or more ２ the composite layer contains graphite and a second binder, and the graphite has an X-ray diffraction pattern in which the ratio of the peak intensity corresponding to the (110) plane to the peak intensity corresponding to the (002) plane is 0.0040 or more.

[0018] When the lithium ion secondary battery electrode according to this embodiment is used as an electrode for a lithium ion secondary battery, it is possible to achieve both excellent rapid charging performance and excellent cycle characteristics in the lithium ion secondary battery.

[0019] 1.2. Electrode Embodiment A1 The following describes a lithium-ion secondary battery electrode according to Embodiment A1 of the present invention with reference to the drawings. FIG. 1 is a schematic diagram of a lithium-ion secondary battery electrode according to Embodiment A1, viewed from the thickness direction of the electrode. FIG. 2 is a schematic diagram of a cross section taken along line II-II in FIG. 1 . As shown in FIGS. 1 and 2 , the electrode 100 includes a current collector 110, multiple intermediate portions 120, and a composite layer 130. Although not shown, the electrode 100 for a lithium-ion secondary battery may also include a current collecting member, such as a lead or a current collecting tab, for collecting current from the current collector 110. Each of the multiple intermediate portions is arranged in an island-like manner on the current collector 110. Here, "the intermediate portions are arranged in an island-like manner" means that multiple intermediate portions are provided and are arranged discretely from one another. Furthermore, "the intermediate portions are arranged on the current collector" means that the intermediate portions are arranged in contact with the current collector, preferably directly.

[0020] In this embodiment, a plurality of intermediate portions 120 and a composite layer 130 are arranged on one surface 110U of the two main surfaces of current collector 110.

[0021] In another embodiment, an intermediate portion and a composite layer may be disposed on each of the two main surfaces of the current collector.

[0022] In this embodiment, the intermediate portions 120 are arranged in an island-like pattern throughout the entire electrode. However, in another embodiment, intermediate portions that are not arranged in an island-like pattern, i.e., continuously distributed, for example, in a strip-like pattern, may be formed in a portion of the electrode. Alternatively, intermediate portions that are arranged in an island-like pattern but whose average distance between the peripheries and / or area S are outside the ranges described below may be formed. In a lithium-ion secondary battery, the positive electrode and the negative electrode are typically arranged opposite each other. The portion of one electrode surface that does not face the other electrode typically does not significantly contribute to charge / discharge reactions. Therefore, in the portion of the electrode that does not face the other electrode, the intermediate portions do not need to be arranged in an island-like pattern, and intermediate portions whose average distance between the peripheries and / or area S are outside the ranges described below may be arranged. For example, continuously distributed intermediate portions or intermediate portions whose average distance between the peripheries and / or area S are outside the ranges described below may be arranged in the peripheral portion of the electrode. When the intermediate portions are continuously distributed along the peripheral edge of the electrode, it is possible to reduce the likelihood of the composite layer falling off from the peripheral edge during the electrode manufacturing process (e.g., cutting the raw electrode sheet). Similarly, when the intermediate portions are arranged along the peripheral edge of the electrode, the average distance between the peripheral edges is less than the lower limit described below or the area S exceeds the upper limit described below, it is possible to reduce the likelihood of the composite layer falling off from the peripheral edge during the electrode manufacturing process (e.g., cutting the raw electrode sheet).

[0023] It is preferable that an intermediate portion is formed in a surface of one electrode that faces the other electrode, the intermediate portion being arranged in an island shape and having an average distance between peripheries and an area S that falls within the ranges described below. Hereinafter, the intermediate portion being arranged in an island shape and having an average distance between peripheries and an area S that falls within the ranges described below will also be referred to as a predetermined intermediate portion.

[0024] However, an intermediate portion that does not fall under the specified intermediate portion may be formed on the surface of one electrode facing the other electrode. The ratio of the number of intermediate portions that do not fall under the specified intermediate portion to the number of specified intermediate portions is typically 15% or less, typically 0% or more, and may even be 0%, assuming the number of specified intermediate portions to be 100%.

[0025] <Intermediate portion> The shape of the intermediate portion as viewed in the thickness direction of the electrode is not particularly limited. Examples of the shape of the intermediate portion include a circle; an ellipse; and a polygon such as a triangle or a quadrangle (square, rectangle, diamond, etc.). As viewed in the thickness direction of the electrode, each of the multiple intermediate portions may have the same shape as one another or different shapes from one another. An example of intermediate portions arranged in an island shape is intermediate portions that have a substantially circular shape (dot shape) and are arranged on the current collector so that the distance between the peripheries of adjacent intermediate portions is approximately the same or the same.

[0026] Arranging multiple intermediate portions in an island-like configuration on the current collector can improve the rapid charging characteristics of a battery. The inventor speculates that the reason for this is as follows. The binder contained in the intermediate portions typically has low conductivity and typically acts as an insulator, so the intermediate portions present between the current collector and the composite layer prevent electrical conduction between the current collector and the composite layer. Therefore, the conductive path between the composite layer disposed on the intermediate portions and the current collector is created so as to avoid the intermediate portions. If the intermediate portions have a continuous shape (e.g., a strip-like or lattice-like shape) when viewed from the thickness direction of the electrode, i.e., if the intermediate portions are not arranged in an island-like configuration, it is believed that the conductive path connecting the composite layer disposed on the intermediate portions to the portion of the current collector on which no intermediate portions are disposed is not created in the direction in which the intermediate portions are continuous. For example, if the intermediate portions are formed in a strip-like configuration when viewed from the thickness direction of the electrode, it is believed that the direction of the conductive path when viewed from the thickness direction of the electrode is limited to directions other than the direction in which the intermediate portions extend. On the other hand, when multiple intermediate portions are arranged on the current collector in an island-like pattern as viewed in the thickness direction of the electrode, the multiple intermediate portions are arranged discretely on the current collector, so there is no specific direction in which the intermediate portions are continuous, and it is thought that a conductive path connecting the composite layer arranged on the intermediate portion to a portion of the current collector on which no intermediate portion is arranged is formed in all directions from the intermediate portion as viewed in the thickness direction of the electrode. As a result, it is thought that non-uniform reactions in the electrode are reduced, and the characteristics of the battery during fast charging can be improved.

[0027] When viewed in the thickness direction of the electrode, the average distance between the edges of the adjacent intermediate portions is usually 30 μm or more, preferably 40 μm or more, more preferably 50 μm or more, and usually 250 μm or less, preferably 180 μm or less, more preferably 150 μm or less. When the average distance between the edges is equal to or greater than the lower limit, the rapid charging characteristics and cycle characteristics are improved. When the average distance between the edges is equal to or less than the upper limit, the cycle characteristics are improved. In addition, the detachment of the composite layer from the current collector during the process of cutting and shredding the electrode can be suppressed.

[0028] Here, the intermediate portions adjacent to an arbitrary intermediate portion M1 are determined as follows. FIG. 3 is a schematic diagram illustrating intermediate portions adjacent to an arbitrary intermediate portion M1. As shown in FIG. 3, the distances between the peripheries of the intermediate portion M1 and the intermediate portions M2, M3, M4, M5, M6, M7, M8, and M9 are set to distances L2, L3, L4, L5, L6, L7, L8, and L9, respectively. Distance L2 is shorter than distance L7. Distance L3 is shorter than distance L9. Distance L5 is shorter than distance L4. Distance L6 is shorter than distance L8. The surface on which the intermediate portion M1 is located is divided into four quadrants Q1, Q2, Q3, and Q4 by two straight lines that intersect at right angles at the center of the arbitrary intermediate portion M1. Among the intermediate portions (intermediate portions M7 and M2 in FIG. 3 ) present in quadrant Q1, the intermediate portion (intermediate portion M2 in FIG. 3 ) having the shortest distance between its periphery and the intermediate portion M1 is considered to be adjacent to the intermediate portion M1. Similarly, among the intermediate portions (intermediate portions M3 and M9 in FIG. 3 ) present in quadrant Q2, the intermediate portion (intermediate portion M3 in FIG. 3 ) having the shortest distance between its periphery and the intermediate portion M1 is considered to be adjacent to the intermediate portion M1. Similarly, among the intermediate portions (intermediate portions M4 and M5 in FIG. 3 ) present in quadrant Q3, the intermediate portion (intermediate portion M5 in FIG. 3 ) having the shortest distance between its periphery and the intermediate portion M1 is considered to be adjacent to the intermediate portion M1. In this manner, intermediate portions M2, M3, M5, and M6 are selected relative to intermediate portion M1, and are considered to be intermediate portions adjacent to intermediate portion M1. In the examples described below, the intermediate portion of interest and the intermediate portions adjacent to it are identified in a similar manner. When dividing the surface on which intermediate portion M1 is located into four quadrants, the surface is divided so that the four intermediate portions (in the figure, intermediate portions M2, M3, M5, and M6) in order of shortest distance from their peripheries to intermediate portion M1 are included in one of the four quadrants.

[0029] The shortest distance among the distance L2 between the peripheries of the intermediate portion M1 and the intermediate portion M2, the distance L3 between the peripheries of the intermediate portion M1 and the intermediate portion M3, the distance L5 between the peripheries of the intermediate portion M1 and the intermediate portion M5, and the distance L6 between the peripheries of the intermediate portion M1 and the intermediate portion M6 is defined as the distance D Ｓ The longest distance is the distance D Ｌ Let's say.

[0030] The average distance between the peripheries of the adjacent intermediate portions is determined by randomly selecting 10 intermediate portions and determining the distance D Ｓ and distance D Ｌ The obtained 10 distances D Ｓ Average value D Ｓ (ave) and 10 distances D Ｌ Average value D Ｌ The fact that the average distance between the peripheries of the adjacent intermediate portions falls within the above range means that the average value D Ｓ (ave) and average value D Ｌ (ave) falls within the above range.

[0031] The area S of each intermediate portion as viewed from the thickness direction of the electrode is usually 5000 μm ２ More than 5000 μm, preferably 5000 μm ２ More preferably, 16,000 μm ２ More preferably, 20,000 μm or more ２ or more, usually 150,000 μm ２ Less than 100,000 μm, preferably ２ Less than or equal to 60,000 μm, more preferably ２ When the area S is equal to or greater than the lower limit, a lithium ion secondary battery including the electrode can have high cycle characteristics. When the area S is equal to or less than the upper limit, a lithium ion secondary battery including the electrode can have high rapid charging characteristics.

[0032] In an electrode, the average distance between the edges of adjacent intermediate portions and the area S of the intermediate portions each fall within the above ranges can be confirmed by using a sample including a current collector and multiple intermediate portions to identify the outlines of the intermediate portions as viewed in the thickness direction of the electrode and performing image analysis based on the identified outlines of the intermediate portions. A sample including a current collector and multiple intermediate portions can be obtained by removing the composite layer included in the electrode using an appropriate method while maintaining the shape, size, and positional relationship of the multiple intermediate portions as viewed in the thickness direction of the electrode. The outlines of the intermediate portions as viewed in the thickness direction of the electrode can be identified by observing the obtained sample including the current collector and multiple intermediate portions with a scanning electron microscope or by elemental analysis using energy dispersive X-ray analysis. A sample in which the shape, size, and positional relationship of the multiple intermediate portions is maintained can be obtained by a method in which adhesive tape is attached to the surface of the composite layer of the electrode and then peeled off the tape to remove the composite layer present in the areas where the intermediate portions of the current collector are not formed.

[0033] The area S of the intermediate portion can be determined by arbitrarily selecting 10 intermediate portions, measuring their areas S1 to S10, and calculating the arithmetic mean value of the areas S1 to S10.

[0034] The number of intermediate portions in the electrode is not particularly limited and can be any number depending on the area of ​​the electrode. The number of intermediate portions per unit area of ​​the electrode is, for example, 350 / cm. ２ or more, for example, 10,000 particles / cm ２ The following is the result.

[0035] The dimension of the intermediate portion in a direction parallel to the thickness direction of the electrode (thickness of the intermediate portion) is, for example, 0.6 μm or more and, for example, 5 μm or less.

[0036] (First Binder) The intermediate portion usually contains a binder. Here, the binder contained in the intermediate portion is also referred to as the first binder to distinguish it from the binder contained in the composite layer described later. The first binder is a material that can bind the composite layer and the current collector.

[0037] The first binder usually contains a polymer. Hereinafter, the polymer that can be contained in the first binder is also referred to as polymer (1). The polymer (1) can be particulate in the middle portion. Whether the middle portion is formed of particulate polymer (1) can be confirmed by measuring with an atomic force microscope that the elastic modulus of the middle portion is not uniform. When the middle portion is formed of particulate polymer (1), the grain boundaries of the particulate polymer (1) can be observed as a change in the elastic modulus.

[0038] The polymer (1) is not particularly limited, and any polymer can be used. As the polymer (1), a polymer that can provide excellent mechanical stability to the binder composition when it is made into a binder composition containing the polymer (1) and a solvent; or a polymer that can provide excellent tackiness to the intermediate portion when it is made into an intermediate portion containing the polymer (1). When the binder composition has excellent mechanical stability, the binder composition can be stably applied to the current collector, resulting in excellent electrode productivity. When the intermediate portion containing the polymer (1) has excellent tackiness, a composite layer can be formed at a high production rate on the current collector provided with the intermediate portion. Tackiness can be evaluated by a ball tack test (JIS Z0237), a probe tack test, or the like. The polymer (1) is preferably chemically and electrochemically stable so that good battery performance can be maintained when the electrode is used in a lithium ion secondary battery. Specific examples of the polymer (1) include (meth)acrylic polymers and aromatic vinyl-conjugated diene copolymers such as styrene-butadiene copolymers. The term "(meth)acrylic polymer" refers to a polymer containing a (meth)acrylic acid ester monomer unit. An example of a (meth)acrylic acid ester monomer unit is a (meth)acrylic acid alkyl ester monomer unit. In one embodiment, the polymer (1) is preferably a (meth)acrylic polymer. When the polymer (1) is a (meth)acrylic polymer, the polymer (1) preferably contains a (meth)acrylic acid alkyl ester monomer unit. In this specification, the alkyl bonded to the non-carbonyl oxygen atom of the (meth)acrylic acid alkyl ester may be a linear alkyl, a branched alkyl, or a cyclic alkyl. The term "(meth)acrylic acid alkyl ester monomer unit" refers to a structural unit having a structure formed by polymerizing a (meth)acrylic acid alkyl ester monomer. The term "(meth)acrylic acid alkyl ester monomer" also includes an acrylic acid alkyl ester monomer, a methacrylic acid alkyl ester monomer, and a combination thereof.Examples of the (meth)acrylic acid alkyl ester monomer include acrylic acid alkyl ester monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, cyclohexyl acrylate, and isobornyl acrylate. and alkyl methacrylate monomers such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate. Among these, alkyl (meth)acrylate monomers in which the alkyl group bonded to the non-carbonyl oxygen atom has 4 or more carbon atoms are preferred, and alkyl (meth)acrylate monomers in which the alkyl group bonded to the non-carbonyl oxygen atom has 6 to 20 carbon atoms are more preferred. Polymer (1) may contain one type of alkyl (meth)acrylate monomer unit alone, or two or more types may be contained in combination.

[0039] The proportion of (meth)acrylic acid alkyl ester monomer units in polymer (1) is preferably 35% by weight or more, more preferably 45% by weight or more, even more preferably 55% by weight or more, and is preferably 80% by weight or less, more preferably 75% by weight or less, even more preferably 70% by weight or less. The proportion of (meth)acrylic acid alkyl ester monomer units in polymer (1) usually corresponds to the weight ratio of the (meth)acrylic acid alkyl ester monomer to the total weight of the monomers used in producing polymer (1) (charge ratio of the (meth)acrylic acid alkyl ester monomer).

[0040] The polymer (1) preferably contains an aromatic monovinyl monomer unit. The aromatic monovinyl monomer unit refers to a structural unit having a structure formed by polymerizing an aromatic monovinyl monomer. Examples of the aromatic monovinyl monomer include styrene, α-methylstyrene, and vinyltoluene, and among these, styrene is preferred. The aromatic monovinyl monomer unit may be contained in the polymer (1) either alone or in combination of two or more types.

[0041] The proportion of aromatic monovinyl monomer units in polymer (1) is preferably 20% by weight or more, more preferably 25% by weight or more, even more preferably 27% by weight or more, and is preferably 50% by weight or less, more preferably 55% by weight or less. The proportion of aromatic monovinyl monomer units in polymer (1) usually corresponds to the weight ratio of aromatic monovinyl monomer to the total weight of monomers used in producing polymer (1) (feed ratio of aromatic monovinyl monomer).

[0042] The polymer (1) may contain a crosslinkable monomer unit from the viewpoint of reducing swelling of the intermediate portion in the presence of an electrolyte solution and improving the cycle characteristics of the battery. The crosslinkable monomer unit refers to a structural unit having a structure formed by polymerizing a crosslinkable monomer. The crosslinkable monomer refers to a monomer capable of forming a crosslinked structure upon polymerization. Examples of the crosslinkable monomer include a monomer having two or more reactive groups per molecule.

[0043] The polymer (1) may contain one type of crosslinkable monomer unit alone or a combination of two or more types.

[0044] When polymer (1) contains crosslinkable monomer units, the proportion of the crosslinkable monomer units is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and even more preferably 0.5% by weight or more, and from the viewpoint of improving the tackiness of the central portion, is preferably 10% by weight or less, more preferably 7% by weight or less, and even more preferably 6% by weight or less. The proportion of the crosslinkable monomer units in polymer (1) usually corresponds to the weight ratio of the crosslinkable monomer to the total weight of the monomers used in producing polymer (1) (charge ratio of the crosslinkable monomer).

[0045] Examples of the reactive group possessed by the crosslinkable monomer include an epoxy group, an N-methylol group, an oxetanyl group, an oxazoline group, an ethylenically unsaturated bond group, and combinations thereof. Among these, the epoxy group, the N-methylol group, and the ethylenically unsaturated bond group are preferred.

[0046] Specific examples of the crosslinkable monomer include an epoxy / N-methylol group-containing crosslinkable monomer having at least one of an epoxy group and an N-methylol group and one or more ethylenically unsaturated bonds; and a polyvalent ethylenically unsaturated crosslinkable monomer having neither an epoxy group nor an N-methylol group and two or more ethylenically unsaturated bonds.

[0047] Examples of the epoxy / N-methylol group-containing crosslinkable monomer having at least one of an epoxy group and an N-methylol group and one or more ethylenically unsaturated bonds include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether; diene or polyene monoepoxides such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, and 1,2-epoxy-5,9-cyclododecadiene; 3,4-epoxy-1-butene, 1,2-epoxy- glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl 4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl 4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexenecarboxylic acid, and glycidyl ester of 4-methyl-3-cyclohexenecarboxylic acid; and N-methylol-substituted (meth)acrylamides such as N-methylol(meth)acrylamide and N,N'-dimethylol(meth)acrylamide. Among these, allyl glycidyl ether, N-methylol(meth)acrylamide, and glycidyl (meth)acrylate are preferred, allyl glycidyl ether and N-methylol acrylamide are more preferred, and allyl glycidyl ether is even more preferred.

[0048] When polymer (1) contains the epoxy / N-methylol group-containing crosslinkable monomer units, the proportion of the epoxy / N-methylol group-containing crosslinkable monomer units is preferably 0.1 wt % or more, more preferably 0.2 wt % or more, and even more preferably 0.5 wt % or more. From the viewpoint of improving the tackiness of the intermediate portion, it is preferably 5 wt % or less, more preferably 4 wt % or less, and even more preferably 3 wt % or less. The epoxy / N-methylol group-containing crosslinkable monomer units refer to structural units having a structure formed by polymerizing epoxy / N-methylol group-containing crosslinkable monomers. The proportion of the epoxy / N-methylol group-containing crosslinkable monomer units in polymer (1) usually corresponds to the weight ratio of the epoxy / N-methylol group-containing crosslinkable monomer to the total weight of the monomers used in producing polymer (1) (the charge ratio of the epoxy / N-methylol group-containing crosslinkable monomer units).

[0049] Examples of polyvalent ethylenically unsaturated crosslinkable monomers having two or more ethylenically unsaturated bonds include allyl (meth)acrylate, ethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane-tri(meth)acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl ether, allyl or vinyl ethers of polyfunctional alcohols other than those mentioned above, triallylamine, methylenebisacrylamide, and divinylbenzene. Among these, ethylene glycol di(meth)acrylate and allyl (meth)acrylate are preferred, and allyl (meth)acrylate is more preferred.

[0050] When the polymer (1) contains the polyethylenically unsaturated crosslinkable monomer unit, the proportion of the polyethylenically unsaturated crosslinkable monomer unit is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and even more preferably 0.5% by weight or more. From the viewpoint of improving the tackiness of the central portion, it is preferably 10% by weight or less, more preferably 8% by weight or less, and even more preferably 5% by weight or less. The polyethylenically unsaturated crosslinkable monomer unit refers to a structural unit having a structure formed by polymerizing a polyethylenically unsaturated crosslinkable monomer. The proportion of the polyethylenically unsaturated crosslinkable monomer unit in the polymer (1) usually corresponds to the weight ratio of the polyethylenically unsaturated crosslinkable monomer to the total weight of the monomers used in producing the polymer (1) (the charge ratio of the polyethylenically unsaturated crosslinkable monomer).

[0051] Polymer (1) preferably contains an acid group-containing monomer unit in order to enhance the mechanical stability of the binder composition containing polymer (1) and a solvent and to more stably form an intermediate portion on the current collector. Examples of acid group-containing monomers that can form the acid group-containing monomer unit include monomers having a carboxylic acid group, monomers having a sulfo group, and monomers having a phosphate group. Examples of monomers having a carboxylic acid group include monocarboxylic acids and dicarboxylic acids. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of monomers having a sulfo group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid 2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, and p-styrenesulfonic acid. In this specification, "(meth)allyl" means allyl and / or methallyl. Furthermore, examples of monomers having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. These acid group-containing monomer units may be in the form of a salt in polymer (1). When polymer (1) is a polymer containing acid group-containing monomer units, some or all of the acid groups in the acid group-containing monomer units may be in the form of anions. Polymer (1) may be, for example, an alkali metal salt such as lithium salt, sodium salt, or potassium salt, or an alkaline earth metal salt such as magnesium salt or calcium salt. These acid group-containing monomers may be used alone or in combination of two or more in any ratio.

[0052] The proportion of acid group-containing acid monomer units in polymer (1) is preferably 0.1 wt% or more, more preferably 0.5 wt% or more, even more preferably 1 wt% or more, and preferably 30 wt% or less, more preferably 25 wt% or less, and even more preferably 20 wt% or less. The proportion of acid group-containing monomer units in polymer (1) usually corresponds to the weight ratio of the acid group-containing monomer to the total weight of the monomers used in producing polymer (1) (the charge ratio of the acid group-containing monomer). Polymer (1) may contain hydroxyl group-containing monomer units to improve adhesion between the intermediate portion and the current collector. The hydroxyl group-containing monomer refers to a monomer containing a hydroxyl group. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 4-hydroxybutyl acrylate.

[0053] The proportion of the hydroxyl group-containing monomer units in polymer (1) is preferably 20% by weight or less, more preferably 15% by weight or less, even more preferably 10% by weight or less, and usually 0% by weight or more, and may be 0% by weight, but is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and even more preferably 1% by weight or more. The proportion of the hydroxyl group-containing monomer units in polymer (1) usually corresponds to the weight ratio of the hydroxyl group-containing monomer to the total weight of the monomers used in producing polymer (1) (the charge ratio of the hydroxyl group-containing monomer).

[0054] The polymer (1) may contain any monomer unit other than the above-mentioned monomer units.

[0055] The polymer (1) may contain an α,β-ethylenically unsaturated nitrile monomer unit. The α,β-ethylenically unsaturated nitrile monomer unit refers to a structural unit having a structure formed by polymerizing an α,β-ethylenically unsaturated nitrile monomer. The α,β-ethylenically unsaturated nitrile monomer refers to a nitrile compound having an ethylenically unsaturated bond at the α-β position. Examples of the α,β-ethylenically unsaturated nitrile monomer include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile. The α,β-ethylenically unsaturated nitrile monomer unit may be contained in the polymer (1) either alone or in combination of two or more.

[0056] The proportion of the α,β-ethylenically unsaturated nitrile monomer units in polymer (1) is preferably 0% by weight or more, more preferably 1% by weight or more, even more preferably 3% by weight or more, and is preferably 50% by weight or less, more preferably 30% by weight or less, even more preferably 20% by weight or less. The proportion of the α,β-ethylenically unsaturated nitrile monomer units in polymer (1) usually corresponds to the weight ratio of the α,β-ethylenically unsaturated nitrile monomer to the total weight of the monomers used in producing polymer (1) (feed ratio of the α,β-ethylenically unsaturated nitrile monomer).

[0057] The polymer (1) may contain an ethylenically unsaturated amide monomer unit. The ethylenically unsaturated amide monomer unit refers to a structural unit having a structure formed by polymerizing an ethylenically unsaturated amide monomer. Examples of the ethylenically unsaturated amide monomer include (meth)acrylamide. The polymer (1) may contain one type of ethylenically unsaturated amide monomer unit alone, or two or more types of ethylenically unsaturated amide monomer units in combination.

[0058] The polymer (1) can be a homopolymer or a copolymer, and is preferably a copolymer. When the polymer (1) is a copolymer, the polymer (1) may be any of a block copolymer, a random polymer, and a random copolymer having a core / shell structure. When the polymer (1) has a core / shell structure, if the polymerization mode of at least the shell structure portion is random, the polymer (1) is said to be a random copolymer.

[0059] Whether polymer (1) is a random copolymer can be determined by confirming that polymer (1) has a single glass transition temperature, which can be measured using a differential scanning calorimeter in accordance with JIS K7121 at a temperature of −100° C. to 180° C. and a heating rate of 5° C. / min.

[0060] From the viewpoint of increasing the tackiness of the intermediate portion, the glass transition temperature of the polymer (1) is preferably 10°C or lower, more preferably 0°C or lower, and even more preferably -10°C or lower. The lower limit is not particularly limited, but it is usually -100°C or higher.

[0061] The first binder may contain any component in addition to the polymer (1), such as a surfactant, an emulsifier, a dispersion stabilizer, a polymerization initiator, a chain transfer agent, an antifoaming agent, an antioxidant, or a preservative, which are added during or after polymerization of the polymer.

[0062] The weight ratio of the first binder in the intermediate portion is preferably greater than the weight ratio of the second binder in the mixture layer described below.

[0063] (Optional Components Contained in the Intermediate Portion) The intermediate portion may contain an optional component in addition to the first binder. For example, the intermediate portion may contain a plasticizer, which is a low molecular weight compound, in addition to the first binder. Here, a low molecular weight compound generally refers to a compound having a molecular weight of 10,000 or less. The inclusion of a plasticizer can increase the molecular mobility of the polymer (1) and enhance the tackiness of the intermediate portion. The plasticizer is preferably selected from the viewpoint of compatibility with the polymer (1). When a plasticizer is used in the intermediate portion, the weight ratio of the plasticizer is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, and even more preferably 1 part by weight or more, per 100 parts by weight of the polymer (1), and is preferably 10 parts by weight or less, more preferably 5 parts by weight or less.

[0064] The intermediate portion may further contain an optional reinforcing material in addition to the first binder. A reinforcing material is a material that can enhance the mechanical strength of the intermediate portion. Examples of reinforcing materials include organic fillers and inorganic fillers. A specific example of an inorganic filler is carbon nanotubes. A specific example of an organic filler is cellulose nanofibers. When cellulose nanofibers are used in the intermediate portion, the weight ratio is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 0.5 parts by weight or more, and preferably 10 parts by weight or less, more preferably 5 parts by weight or less, relative to 100 parts by weight of polymer (1). When a particulate binder is used to form the intermediate portion, it is preferable to apply a heating operation to the resulting electrode after the pressure application step. The heating operation removes trace amounts of solvent present at the grain boundaries of the particulate binder and reduces voids at the grain boundaries between the particulate binders due to plasticization, thereby enhancing the mechanical strength of the intermediate portion. This is expected to improve the cycle characteristics of the battery.

[0065] <Current Collector> The current collector material is preferably a material that is electrically conductive and electrochemically durable. Specific examples of the current collector material include metals, carbon, and conductive polymers, with metals being preferred. Examples of metals include copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, and alloys thereof. Among these, copper, aluminum, and aluminum alloys are preferred in terms of conductivity and voltage resistance. When high voltage resistance is required, high-purity aluminum as disclosed in JP-A-2001-176757 can be preferably used. Among these, aluminum is preferred as the material for the current collector used for the positive electrode, and copper is preferred as the material for the current collector used for the negative electrode. These materials may be used alone or in combination of two or more.

[0066] The current collector generally has a film or sheet shape. The thickness of the current collector may be appropriately selected depending on the intended use, and is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0067] <Composition layer> The composite layer is disposed on the current collector and a plurality of intermediate portions. Disposing the composite layer on the current collector and the intermediate portions means that the composite layer is disposed so as to contact a part of the current collector where no intermediate portion is disposed, and so as to contact the intermediate portion. The plurality of intermediate portions are disposed between the current collector and the composite layer. When the composite layer is disposed on the current collector and a plurality of intermediate portions, the plurality of intermediate portions bond the composite layer to the current collector, and peeling between the composite layer and the current collector can be suppressed.

[0068] The composite layer typically contains at least an active material and a binder, preferably graphite and a binder. The composite layer may also contain a material such as a conductive material. The binder contained in the composite layer is also referred to as a second binder to distinguish it from the binder contained in the intermediate portion. The second binder is a material that can bind active material particles together. When graphite is used as the active material in the composite layer, the graphite can function as a negative electrode active material in a typical lithium ion secondary battery. Therefore, the lithium ion secondary battery electrode of this embodiment can function as a negative electrode.

[0069] The graphite contained in the composite layer has a ratio (I(110) / I(002)) of the peak intensity (I(110)) corresponding to the (110) plane in the crystal structure of graphite in an X-ray diffraction pattern to the peak intensity (I(002)) corresponding to the (002) plane in the crystal structure of graphite in an X-ray diffraction pattern, which is usually 0.0040 or more, preferably 0.0050 or more, and more preferably 0.0055 or more. The upper limit is not particularly limited, but is preferably 0.0150 or less, and more preferably 0.0115 or less.

[0070] The (002) plane in the crystal structure of graphite is the plane in the c-axis direction of the graphite crystal, and the (110) plane of graphite is the plane in the a-axis direction perpendicular to the (002) plane. When measuring the X-ray diffraction pattern of graphite, peaks attributable to diffraction lines from the (002) plane of graphite and peaks attributable to diffraction lines from the (110) plane of graphite are detected. The ratio (I(110) / I(002)) of the peak intensity (I(110)) corresponding to the (110) plane to the peak intensity (I(002)) corresponding to the (002) plane is a numerical value relating to the orientation of graphite, and a larger ratio (I(110) / I(002)) indicates a smaller orientation. Here, the orientation of graphite refers to the degree to which the (002) crystal plane of the graphite particle is aligned with the surface direction of the current collector.

[0071] When the ratio (I(110) / I(002)) is equal to or greater than the lower limit, the rapid charging characteristics of a lithium ion secondary battery including the electrode can be improved. The reason for this is presumed to be as follows.

[0072] Graphite is an anisotropic material and easily slides in the in-plane direction. Therefore, when a roll press is used to press a graphite-containing layer (composite layer) during the electrode manufacturing process to increase electrode density, the graphite particles in the composite layer tend to orient along the surface of the current collector. Strong orientation of graphite in the in-plane direction of the current collector increases the path (torture length) of voids within the composite layer from the electrode surface to the current collector. When the electrode's void structure is in this state, lithium ions are prevented from migrating from the surface of the electrode composite layer to the deeper part of the composite layer near the current collector during rapid charging. As a result, the charging reaction occurs intensively at the electrode surface, resulting in a reduced charge capacity. Furthermore, metallic lithium may precipitate on the electrode surface, causing irreversible capacity decay. In contrast, when the ratio (I(110) / I(002)) relating to the orientation is equal to or greater than the lower limit, i.e., when the orientation of the graphite particles in the current collector plane is limited, it becomes possible to shorten the path (tortuous path length) of the voids from the electrode surface to the deep part of the electrode near the current collector, thereby improving the charging performance during rapid charging.

[0073] The graphite ratio (I(110) / I(002)) contained in the composite layer can be adjusted by adjusting the graphite ratio (I(110) / I(002)) used as the material for the composite layer and the manufacturing conditions for the composite layer. For example, composite particles containing graphite and a binder are manufactured as a powder, and a layer of the powder composite particles is pressed to form a composite layer, thereby forming a composite layer having a graphite ratio (I(110) / I(002)) within the above range. Since the graphite contained in the composite particles is present in the composite particles in a state of low orientation, this can be used to form a composite layer on a current collector, and then a pressing step can be performed. A liquid composition containing graphite, a binder, and a solvent can be applied to a current collector, dried, and pressed to produce a composite layer and an electrode. The graphite ratio (I(110) / I(002)) in the above range cannot generally be obtained in conventional electrode manufacturing methods in which a liquid composition containing graphite, a binder, and a solvent is applied to a current collector, dried, and then pressed. Since the graphite particles are oriented to a certain extent on the current collector simply by applying and drying the liquid composition, the graphite ratio (I(110) / I(002)) in the above range can therefore indicate that the composite layer is formed using composite particles. The graphite ratio (I(110) / I(002)) can be changed, for example, by selecting a suitable method for manufacturing the composite particles. In particular, the orientation of graphite in the electrode can be reduced by selecting a spray-drying method, which can instantaneously form composite particles, as the method for manufacturing the composite particles.

[0074] The graphite ratio (I(110) / I(002)) can be measured by the following method. An X-ray diffraction pattern is obtained for the composite layer using an X-ray diffractometer. The obtained X-ray diffraction pattern is then compared with a known X-ray diffraction pattern of graphite to identify the peak due to the (110) plane of graphite and the peak due to the (002) plane of graphite in the X-ray diffraction pattern of the composite layer. The respective peak intensities I(110) and I(002) are obtained, and the ratio (I(110) / I(002)) can be determined. X-ray diffraction measurement can be performed, for example, by a focusing method under conditions of a tube voltage of 45 kV, a tube current of 200 mA, a measurement angle of 20° to 90°, and a scanning speed of 20° / min.

[0075] The graphite may be natural graphite, artificial graphite, etc. The shape of the graphite is not particularly limited, and any of flake graphite, flat graphite, and spherical graphite may be used, or two or more of these may be used in combination. The graphite may be surface-treated, for example, by coating with amorphous carbon.

[0076] The composite layer may contain any active material in addition to graphite as the active material. Examples of the optional active material include carbonaceous materials such as amorphous carbon, mesocarbon microbeads, and pitch-based carbon fibers; conductive polymers such as polyacenes; metals or alloys thereof such as silicon, tin, zinc, manganese, iron, and nickel; oxides or sulfates of the above metals or alloys; metallic lithium; lithium alloys such as Li—Al, Li—Bi—Cd, and Li—Sn—Cd; lithium transition metal nitrides; and silicon-containing active materials, as described below. The active material may also be in the form of a composite material with another material, for example, a composite material in which the surface of the active material is coated with conductive carbon. The composite material can be prepared, for example, by attaching a conductive material to the surface of active material particles, for example, by mechanical modification.

[0077] For example, the composite layer may contain a silicon-atom-containing active material from the viewpoint of increasing the capacity density of the electrode. The silicon-atom-containing active material is a material that contains silicon atoms and can function as an active material (particularly a negative electrode active material) in an electrode for a lithium ion secondary battery. Examples of silicon-atom-containing active materials include silicon and alloys containing silicon, and silicon oxide (SiO, SiOx: 0<x<2). When the composite layer contains a silicon-atom-containing active material in addition to graphite, the capacity density per unit area of ​​the portion where the negative electrode and positive electrode face each other in the lithium ion secondary battery is improved, thereby increasing the energy density. The silicon-atom-containing active material may be in the form of a composite material of the silicon-atom-containing material and another material, for example, a composite material in which the surface of the active material is coated with conductive carbon. Any active material that can be contained in addition to graphite may be used alone or in combination of two or more types.

[0078] When the composite layer contains a silicon atom-containing active material in addition to graphite, from the viewpoint of improving the discharge capacity per unit area of ​​the portion where the negative electrode and positive electrode face each other in the lithium ion secondary battery, the weight ratio of the silicon atom-containing active material to the graphite in the composite layer is preferably 1 wt % or more, more preferably 3 wt % or more, and even more preferably 5 wt % or more, and is usually 100 wt % or less, and preferably less than 100 wt %.

[0079] The second binder typically contains a polymer. The polymer contained in the second binder is also referred to as polymer (2). Polymer (2) may be the same polymer as polymer (1) or a different polymer. Polymer (2) may be used singly or in combination of two or more types. Polymer (2) may be a soluble polymer that is soluble in a solvent, a non-soluble polymer dispersed in an insoluble solvent, or a combination of a soluble polymer and a non-soluble polymer. A soluble polymer refers to a polymer that has an insoluble content of less than 0.5 wt% when 0.5 g of the polymer is dissolved in 100 g of solvent at 25°C. A non-soluble polymer refers to a polymer that has an insoluble content of 0.5 wt% or more when 0.5 g of the polymer is dissolved in 100 g of solvent at 25°C. When the solvent used for the soluble polymer and non-soluble polymer is water, they are referred to as water-soluble polymer and water-insoluble polymer, respectively. The soluble polymer may be a thickener. The thickener has the function of stably dispersing particles of the active material and the like.

[0080] Examples of the polymer (2) that can be contained in the second binder include water-soluble polymers or combinations of water-soluble and water-insoluble polymers. Commercially available thickeners may be used as the water-soluble polymer. Examples of water-soluble polymers include carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, polyvinyl alcohol, polymethacrylic acid, polyacrylic acid, and copolymers containing acrylamide monomer units and acrylic acid monomer units (e.g., acrylic acid-acrylamide copolymers, acrylamide / acrylic acid / N-hydroxyethyl acrylamide terpolymers). These may be used alone or in combination of two or more. These may be used in either an unneutralized or neutralized state. Among these, carboxymethyl cellulose and copolymers containing acrylamide monomer units and acrylic acid monomer units are preferred. Here, the second binder preferably contains a water-soluble polymer having a weight-average molecular weight Mw of 500,000 or more, more preferably 800,000 or more, and preferably 10,000,000 or less, and more preferably 8,000,000 or less. When the second binder contains a water-soluble polymer having a weight-average molecular weight equal to or greater than the lower limit, the dispersion stability of the slurry produced by the spray drying method can be further improved, and when the second binder contains a water-soluble polymer having a weight-average molecular weight equal to or less than the upper limit, the solids concentration of the slurry produced by the spray drying method can be further increased, thereby improving productivity.

[0081] The second binder preferably contains a water-insoluble polymer containing an acid group-containing monomer unit such as an ethylenically unsaturated carboxylic acid monomer unit, an aromatic vinyl monomer unit, and a diene-based monomer unit.

[0082] Examples of the acid group-containing monomer capable of forming the acid group-containing monomer unit that can be contained in the water-insoluble polymer as the binder include those exemplified as the acid group-containing monomer capable of forming the acid group-containing monomer unit that can be contained in the polymer (1) that constitutes the intermediate portion.

[0083] In the water-insoluble polymer serving as a binder, when the total monomer units contained in the water-insoluble polymer is taken as 100 parts by weight, the content of the acid group-containing monomer unit is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, even more preferably 1 part by weight or more, and preferably 30 parts by weight or less, more preferably 25 parts by weight or less, and even more preferably 20 parts by weight or less. If the content ratio of the acid group-containing monomer unit in the water-insoluble polymer serving as a binder is the above-mentioned lower limit or more, the stability of the slurry viscosity over time can be improved when producing composite particles by a spray drying method.

[0084] Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include styrene, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. The aromatic vinyl monomers may be used alone or in combination of two or more at any ratio, and among these, styrene is preferred.

[0085] In the water-insoluble polymer used as a binder, when the total monomer units contained in the water-insoluble polymer are taken as 100 parts by weight, the content of the aromatic vinyl monomer units is preferably 20 parts by weight or more, more preferably 25 parts by weight or more, even more preferably 30 parts by weight or more, and preferably 90 parts by weight or less, more preferably 80 parts by weight or less, and even more preferably 70 parts by weight or less. If the content of the aromatic vinyl monomer units in the water-insoluble polymer used as a binder is equal to or greater than the above-mentioned lower limit, stability during slurry preparation when producing composite particles by spray drying can be improved, thereby making it difficult for the slurry viscosity to increase. On the other hand, if the content of the aromatic vinyl monomer units in the water-insoluble polymer used as a binder is equal to or less than the above-mentioned upper limit, the swelling degree of the water-insoluble polymer in the electrolyte used in lithium-ion secondary batteries can be kept within a more suitable range.

[0086] Examples of diene monomers capable of forming diene monomer units include aliphatic conjugated diene monomers. Examples of aliphatic conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, chloroprene, and cyanobutadiene. The diene monomers may be used alone or in combination of two or more in any ratio. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred, in terms of ease of availability.

[0087] In the water-insoluble polymer used as a binder, when the total monomer units contained in the water-insoluble polymer are taken as 100 parts by weight, the content of the diene monomer units is preferably 20 parts by weight or more, more preferably 25 parts by weight or more, and even more preferably 30 parts by weight or more, and is preferably 85 parts by weight or less, more preferably 80 parts by weight or less, and even more preferably 70 parts by weight or less. If the content ratio of the diene monomer units in the water-insoluble polymer used as a binder is equal to or greater than the above-mentioned lower limit, the binding strength of the electrode can be increased. On the other hand, if the content ratio of the diene monomer units in the water-insoluble polymer used as a binder is equal to or less than the above-mentioned upper limit, the mechanical stability during slurry preparation when producing composite particles by a spray drying method can be improved.

[0088] The water-insoluble polymer may contain any monomer unit in addition to the above-mentioned monomer units. Monomers capable of forming the other optional monomer units constituting the water-insoluble polymer are not particularly limited, and examples thereof include monomers copolymerizable with diene monomers. Specific examples include hydroxyl group-containing monomer units and monomers having carbon-carbon unsaturated bonds other than the above-mentioned acid group-containing monomers and aromatic vinyl monomer units. Examples of such monomers having carbon-carbon unsaturated bonds include cyano group-containing vinyl monomers, amino group-containing vinyl monomers, pyridyl group-containing vinyl monomers, and alkoxyl group-containing vinyl monomers. The above-mentioned monomers copolymerizable with diene monomers may be used alone or in combination of two or more in any ratio. Examples of hydroxyl group-containing monomers capable of forming hydroxyl group-containing monomer units include the examples of hydroxyl group-containing monomers capable of forming hydroxyl group-containing monomer units that can be contained in the polymer (1).

[0089] The second binder may contain an optional component in addition to the polymer (2). Examples of the optional component include the same examples as the examples of the optional components that can be contained in the first binder.

[0090] The content of the second binder in the composite layer is preferably 0.3 wt % or more, more preferably 0.5 wt % or more, and even more preferably 1.0 wt % or more, and is preferably 20 wt % or less, more preferably 15 wt % or less, and even more preferably 10 wt % or less, based on 100 wt % of the weight of the composite layer.

[0091] The mixture layer may contain optional components in addition to the graphite and second binder, such as a dispersant and a conductive material.

[0092] Examples of conductive materials that can be contained in the composite layer include carbon black, carbon nanotubes, vapor-grown carbon fiber (VGCF (registered trademark)), graphene, and expanded graphite (excluding the above-mentioned graphite). Carbon black is an aggregate in which several layers of graphitic carbon microcrystals gather to form a turbostratic structure, and specific examples include acetylene black, ketjen black, furnace black, channel black, and thermal lamp black. Among carbon blacks, acetylene black, furnace black, and ketjen black are particularly preferred from the viewpoint of reducing resistance.

[0093] The mixture layer may contain no dispersant or may contain a dispersant. The dispersant may be used alone or in combination of two or more types.

[0094] The composite layer may or may not contain a conductive material. The conductive material may be used alone or in combination of two or more. The content of the conductive material in the composite layer is preferably 10 wt% or less, more preferably 5 wt% or less, and even more preferably 3 wt% or less, based on the weight of the composite layer being 100 wt%. The content of the conductive material in the composite layer is usually 0 wt% or more, and may be 0 wt%, preferably 0.01 wt% or more, more preferably 0.03 wt% or more, even more preferably 0.3 wt% or more, and even more preferably 0.5 wt% or more.

[0095] The weight (weight) of the composite layer per unit area is preferably high from the viewpoint of energy density. On the other hand, if the weight is too high, the input / output characteristics tend to deteriorate. Typically, the weight of the positive electrode is determined by the internal volume of the battery, the opposing area of ​​the positive electrode and the negative electrode in the battery, the capacity the battery should have, and the capacity per unit weight of the active material contained in the composite layer. The weight of the negative electrode is preferably set to a value that is equal to or greater than the capacity that can accept the designed amount of lithium ions supplied from the opposing positive electrode. Here, the weight (weight) per unit area of ​​the composite layer refers to the weight of one composite layer. In the case where a composite layer is formed on both sides of the electrode current collector and the electrode has two composite layers, it refers to the weight of one composite layer formed on one side of the current collector.

[0096] The electrode of this embodiment can achieve excellent rapid charging characteristics in a lithium-ion secondary battery even when the composite layer has a high basis weight. As described above, the electrode of this embodiment is manufactured by forming a composite layer on a current collector using, for example, composite particles and then pressing the composite layer. Because the graphite has low orientation in the composite layer, the tortuous path length from the electrode surface to the deep part of the electrode near the current collector is presumably shorter than that of a conventional electrode manufactured by applying a liquid composition containing graphite, a binder, and a solvent to a current collector, drying the composition, and then pressing the composition. This is presumably due to the increased uniformity of the charging reaction from the electrode surface to the deep part of the electrode near the current collector, as well as the appropriate size of the intermediate portions present on the current collector and the appropriate distance between the edges of adjacent intermediate portions.

[0097] The lithium ion secondary battery electrode of this embodiment can be produced by any method. From the viewpoint of effectively improving the rapid charging characteristics, the lithium ion secondary battery electrode of this embodiment is preferably produced by the production method according to embodiment P1 described below.

[0098] <2. Lithium-ion secondary battery> <2.1. Overview of lithium-ion secondary battery> A lithium-ion secondary battery according to one embodiment of the present invention includes the electrode according to the embodiment described above. Typically, such a lithium-ion secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte solution, and includes the electrode according to the embodiment described above as at least one of the positive electrode and the negative electrode. Preferably, in the lithium-ion secondary battery, the negative electrode is the electrode according to the embodiment described above. Hereinafter, a lithium-ion secondary battery in which the negative electrode is the electrode according to the embodiment described above will be described as an example.

[0099] 2.2. Lithium-ion secondary battery embodiment B1 The lithium-ion secondary battery according to embodiment B1 includes the electrode according to embodiment A1 described above as the negative electrode. The negative electrode is the same as the electrode according to embodiment A1, and therefore a description thereof will be omitted. The positive electrode included in the lithium-ion secondary battery according to embodiment B1 includes a current collector and a mixture layer (positive electrode mixture layer) containing a positive electrode active material and a binder. Examples of the positive electrode active material will be described later.

[0100] Examples of the current collector contained in the positive electrode include the examples described above in the electrode embodiments.

[0101] The binder contained in the positive electrode mixture layer typically contains a polymer. The polymer that can be contained in the binder may be one or more polymers selected from the group consisting of polymer (1) and polymer (2). For example, the positive electrode mixture layer may contain a (meth)acrylic polymer (acrylate polymer), a conjugated diene polymer, and / or a fluorine-based polymer, and preferably contains a meth(acrylic) polymer (acrylate polymer) and / or a fluorine-based polymer. The (meth)acrylic polymer (acrylate polymer) is a polymer containing a (meth)acrylic acid ester monomer unit. The conjugated diene polymer is a polymer containing a conjugated diene monomer unit. The conjugated diene monomer unit refers to a monomer unit having a structure formed by polymerizing a conjugated diene or a monomer unit having a structure formed by hydrogenating the conjugated diene. The fluorine-based polymer is a polymer containing a monomer unit containing a fluorine atom. Specific examples of fluorine-based polymers include polytetrafluoroethylene, polyvinylidene fluoride (PVDF), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and perfluoroethylene-propene copolymer.

[0102] The positive electrode can be manufactured by any method, for example, by a method including applying a slurry containing a positive electrode active material, a binder, and other optional components to a current collector in the form of a layer, drying the slurry, and then pressing the resulting layer.

[0103] The non-aqueous electrolyte solution may be, for example, an electrolyte solution in which a supporting electrolyte is dissolved in a non-aqueous solvent. The supporting electrolyte is preferably a lithium salt. For example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among them, LiPF6 is easily soluble in solvents and exhibits a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３ Li is preferred. The supporting electrolyte may be used alone or in combination of two or more. In general, the use of a supporting electrolyte with a higher degree of dissociation tends to result in higher ionic conductivity.

[0104] The concentration of the supporting electrolyte is preferably set in the range of 0.5 mol / L to 2.5 mol / L depending on the type of supporting electrolyte, since in this range, the ionic conductivity can be increased, thereby improving the charge and discharge characteristics of the lithium ion secondary battery.

[0105] The nonaqueous solvent used in the nonaqueous electrolyte solution is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of nonaqueous solvents include carbonate solvents such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); ester solvents such as γ-butyrolactone and methyl formate; ether solvents such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compound solvents such as sulfolane and dimethyl sulfoxide; and ionic liquids that are also used as supporting electrolytes. Among these, carbonate solvents are preferred because of their high dielectric constant and wide stable potential range. One type of nonaqueous solvent may be used alone, or two or more types may be used in combination. Generally, the lower the viscosity of the nonaqueous solvent, the higher the ionic conductivity, and the higher the dielectric constant, the higher the solubility of the supporting electrolyte. However, since there is a trade-off between the two, it is preferable to adjust the ionic conductivity by adjusting the type and mixing ratio of the solvent. The non-aqueous solvent may be used in combination with a solvent in which all or part of the hydrogen atoms are replaced with fluorine atoms, or the entire amount of the solvent may be used.

[0106] The non-aqueous electrolyte may contain any additive in combination with the supporting electrolyte and the non-aqueous solvent. Examples of the optional additive include carbonate compounds such as vinylene carbonate (VC); sulfur-containing compounds such as ethylene sulfite (ES); and fluorine-containing compounds such as fluoroethylene carbonate (FEC). One type of additive may be used alone, or two or more types may be used in combination.

[0107] The lithium ion secondary battery may further include a separator. Examples of the separator include a microporous membrane or nonwoven fabric formed from a resin such as a polyolefin resin or an aromatic polyamide resin; a porous resin-coated membrane containing an inorganic ceramic powder; and the like. Specific examples of the separator include a microporous membrane formed from a resin such as a polyolefin polymer (e.g., polyethylene, polypropylene, polybutene, polyvinyl chloride) or a mixture or copolymer thereof; a microporous membrane formed from a resin such as polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, polyaramid, nylon, or polytetrafluoroethylene; a fabric material woven from polyolefin resin fibers or a nonwoven fabric of the fibers; and an aggregate of insulating material particles. Among these, a microporous membrane formed from a polyolefin resin is preferred from the viewpoints of reducing the overall separator thickness and increasing the active material ratio in the lithium ion secondary battery to improve capacity per volume.

[0108] The separator may have a functional layer such as a heat-resistant layer or an adhesive layer. For example, if the separator has an adhesive layer, adhesiveness can be imparted to the separator, allowing for more efficient production of lithium-ion secondary batteries. Furthermore, for example, if the separator has a heat-resistant layer, heat resistance can be imparted to the separator, thereby improving the heat resistance of the lithium-ion secondary battery. The functional layer that the separator may have may be a layer having two or more functions, for example, a layer having both heat resistance and adhesiveness.

[0109] The thickness of the separator is preferably 1.0 μm or more, more preferably 3 μm or more, and is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less, from the viewpoint of reducing the internal resistance of the separator in the lithium ion secondary battery and from the viewpoint of excellent workability when producing the lithium ion secondary battery.

[0110] Examples of methods for manufacturing lithium ion secondary batteries include stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack according to the battery shape, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the container. Furthermore, if necessary, expandable metal; an overcurrent protection element such as a fuse or a PTC element; or a lead plate may be inserted to prevent pressure buildup within the battery and overcharging and discharging. The shape of the lithium ion secondary battery may be, for example, a coin type, button type, sheet type, cylindrical type, prismatic type, flat type, or the like. The battery container is preferably made of a material that prevents moisture from penetrating into the battery, such as a metal or a laminate of aluminum.

[0111] <Characteristics of Lithium Ion Secondary Battery> A lithium ion secondary battery including the electrode according to the above embodiment has excellent rapid charging characteristics and cycle characteristics.

[0112] (Rapid Charge Characteristics: Charge Rate) The rapid charge characteristics of a lithium-ion secondary battery can be evaluated by the percentage (charge rate) Rc of the battery capacity after charge, where the battery capacity before charge is taken as 100% when the lithium-ion secondary battery is charged at a 0.25-hour rate. Specifically, Rc can be calculated using the following method. After measuring the capacity after initialization to obtain the capacity (C0) at a 10-hour rate discharge, the lithium-ion secondary battery is left to stand at a temperature of 25°C for 1 hour at the lower limit cell voltage, and then charged to a cell voltage of 4.2 V using a constant current method at 4.0 C, i.e., a 0.25-hour rate. After leaving to stand for 30 minutes, the battery is discharged to the lower limit cell voltage using a constant current method at 0.2 C, i.e., a 5-hour rate, at 25°C. The battery capacity C1 at this time is measured. The charge rate Rc (%) can be calculated using the formula: Rc = (C1 / C0) x 100.

[0113] In one example, the higher the Rc, which indicates the rapid charging characteristics of a lithium ion battery, the better.

[0114] (Rapid Charge Characteristics: Rapid Charge-Discharge Cycle Characteristics) The lithium ion secondary battery has excellent rapid charge-discharge cycle characteristics. The rapid charge-discharge cycle characteristics of a lithium ion secondary battery can be evaluated, for example, by the cycle capacity retention rate in a rapid charge-discharge cycle test in which a 0.25 hour rate rapid charge and discharge cycle is performed multiple times (for example, 50 cycles). The higher the cycle capacity retention rate, the better the rapid charge cycle characteristics.

[0115] (Cycle Characteristics) The cycle characteristics of a lithium-ion secondary battery can be evaluated by the cycle capacity retention rate in a cycle test in which 200 charge and discharge cycles are performed at a temperature of 45°C. In one example, the cycle capacity retention rate of the lithium-ion secondary battery is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The upper limit is ideally 100%, but it may be 100% or less. The cycle capacity retention rate represents the ratio of the "discharge capacity at the 200th cycle" to the "discharge capacity at the first cycle" in the cycle test, and can be measured by the method described in the section "Evaluation Method" (Cycle Characteristics) in the Examples section described later.

[0116] (Discharge capacity per unit area) The discharge capacity per unit area is the ratio of the capacity when the battery is discharged at a 10-hour rate over a voltage range from the upper limit voltage to the discharge voltage to the total area of ​​the positive electrode facing the negative electrode. A higher discharge capacity per unit area is preferable from the perspective of energy density. The upper and lower limit voltages of a battery vary depending on the positive and negative electrode active materials used. If the battery specifications are known, it is preferable to set the upper and lower limit voltages of the battery according to those specifications. Furthermore, if the materials used are known, it is preferable to set the upper and lower limit voltages of the battery according to those materials. For example, if the positive electrode active material contains nickel-cobalt-manganese oxide or lithium cobalt oxide, the upper limit voltage of a battery cell is typically 4.2 V. If the positive electrode active material is lithium iron phosphate, the upper limit voltage of a battery cell is typically 3.8 V. When two or more positive electrode active materials are used, the upper limit voltage of a battery cell is determined based on the material that operates at the higher voltage. For new materials, technical literature may be consulted. The minimum voltage varies depending on the positive and negative electrode active materials. When nickel-cobalt-manganese oxide is used as the positive electrode active material and graphite is used as the negative electrode active material, the minimum voltage of a battery cell is typically 3.00 V. When lithium iron phosphate is used as the positive electrode active material, the minimum voltage of the battery is 2.40 V. Furthermore, when graphite and a silicon-containing active material are used in combination as the negative electrode active material, it is preferable to set the minimum voltage to a voltage lower than the above voltage value. If the active material used in the battery is unknown, the type of active material used can be determined from the diffraction pattern resulting from the crystalline structure of the active material by analyzing the battery using high-energy X-rays. If the minimum voltage is unknown, it is preferable to find the current value that reduces the voltage from the rated voltage to a voltage 0.1 V lower than the rated voltage over 30 minutes, continue discharging at that current value, and determine the point at which the slope of the voltage change with time (ΔV / Δt) is 15 times or more the slope of the voltage change with time from the rated voltage to a drop of 0.1 V. After determining the upper and lower limit voltages of the battery as described above, the discharge capacity of the battery at a 10-hour rate can be determined by changing the current value and charging and discharging within the range of the upper and lower limit voltages.When the opposing area of ​​the positive electrode and negative electrode is unknown, it can be obtained by determining the capacity of the battery by 10-hour rate discharge and then disassembling the battery, or by measuring the electrode dimensions inside the battery using X-ray CT.

[0117] When the lithium ion secondary battery is discharged at a 10-hour rate, the discharge capacity (battery capacity) per unit area of ​​the portion where the negative electrode and the positive electrode face each other is preferably 3.3 mAh / cm ２ More preferably, 3.5 mAh / cm ２ More preferably, 4.0 mAh / cm ２ The lithium ion secondary battery according to this embodiment can achieve excellent rapid charging characteristics and cycle characteristics even when the discharge capacity per unit area is equal to or greater than the lower limit.

[0118] For example, when the entire surface of the positive electrode faces a portion of the surface of the negative electrode, the "area of ​​the portion where the negative electrode and the positive electrode face each other" is equal to the area of ​​the positive electrode, specifically the area of ​​the positive electrode composite layer provided on the positive electrode. When one of the positive and negative electrodes (e.g., the negative electrode) of a lithium-ion secondary battery is an electrode in which a composite layer (e.g., a negative electrode composite layer) is formed on each of both surfaces of a current collector, the "area of ​​the portion where the negative electrode and the positive electrode face each other" is the sum (A1 + A2) of the area A1 of the portion where the composite layer formed on one surface of the current collector faces the composite layer (e.g., a positive electrode composite layer) provided on the other electrode (e.g., the positive electrode) and the area A2 of the portion where the composite layer formed on the other surface of the current collector faces the composite layer provided on the other electrode.

[0119] 3. Manufacturing Method of Electrode for Lithium-Ion Secondary Battery 3.1. Embodiment P1 Hereinafter, a manufacturing method of an electrode for a lithium-ion secondary battery according to embodiment P1 will be described. The electrode for a lithium-ion secondary battery manufactured by the manufacturing method of this embodiment includes a current collector, a plurality of intermediate portions arranged in an island shape on the current collector and containing a first binder, and a composite layer arranged on the current collector and the plurality of intermediate portions and containing an active material and a second binder, wherein, as viewed in the thickness direction of the electrode, the average distance between the peripheries of the plurality of intermediate portions adjacent to each other is 30 μm or more and 250 μm or less, and the area S of each of the plurality of intermediate portions is 5000 μm or less. ２150000 μm or more ２ The electrode for a lithium ion secondary battery manufactured by the manufacturing method of this embodiment can be a positive electrode or a negative electrode, and is preferably a negative electrode.

[0120] A method for manufacturing an electrode for a lithium ion secondary battery according to one embodiment of the present invention includes the following steps: (1) applying a binder composition containing the first binder onto the current collector in an island pattern to obtain a first intermediate body having the plurality of intermediate portions; (2) supplying composite particles containing the active material and the second binder onto the current collector and the plurality of intermediate portions of the first intermediate body to form a composite particle layer; and (3) applying pressure to the composite particle layer to form the composite layer and obtain the electrode. Typically, steps (1), (2), and (3) are performed in this order. Each of steps (1), (2), and (3) may or may not be repeated multiple times. A series of steps including steps (1), (2), and (3) may or may not be repeated multiple times (e.g., twice).

[0121] According to the manufacturing method of this embodiment, it is possible to manufacture an electrode that can realize a lithium ion secondary battery with excellent rapid charging characteristics and cycle characteristics. Furthermore, since composite particles containing an active material are used to form the mixture layer, the energy required for manufacturing can be reduced compared to manufacturing methods in which the mixture layer is formed from a slurry containing an active material and a large amount of solvent. Furthermore, continuous operation is easy, and yield can be increased.

[0122] <Step (1)> In step (1), a binder composition containing a first binder is coated onto a current collector in an island pattern to obtain a first intermediate body having a plurality of intermediate portions formed thereon. Coating refers to a method of applying a liquid composition to an object and drying and / or curing it as necessary to form a film of the liquid composition on the object. Furthermore, coating in an island pattern refers to partially coating the binder composition onto the current collector to provide a plurality of discrete, mutually separated coated portions on the current collector.

[0123] The binder composition can be applied to the current collector by any method. The coating in step (1) is performed by adjusting the conditions so that the intermediate portions in the lithium ion secondary battery electrode have a desired distance between the peripheries and an area S. That is, the coating in step (1) is performed so that, in the obtained lithium ion secondary battery electrode, the average distance between the peripheries of the plurality of intermediate portions adjacent to each other is 30 μm or more and 250 μm or less, and the area S of each of the plurality of intermediate portions is 5000 μm or more, as viewed in the thickness direction of the electrode. ２ Exceeding 150,000 μm ２ The coating conditions can be adjusted as follows: The coating conditions can be adjusted appropriately depending on the coating method used. For example, when coating is performed using a gravure coating method, the distance between the peripheries of the intermediate portions can be increased by widening the intervals between the recesses formed on the gravure roll.

[0124] The pattern of the intermediate portions on the current collector is not particularly limited as long as the above relationship is satisfied. It may be random, or may be, for example, a pattern in which the intermediate portions are arranged in a zigzag pattern, a pattern in which the intermediate portions are arranged along parallel straight lines, a pattern in which the intermediate portions are arranged at the center and vertices of a hexagon, or a pattern in which the intermediate portions are arranged at the intersections of the diagonals and vertices of a parallelogram (for example, a pattern in which the intermediate portions are arranged at the center and vertices of a rectangular parallelepiped, or a pattern in which the intermediate portions are arranged at the center and vertices of a square).

[0125] When the binder composition is applied to the current collector by gravure coating and dried to provide the intermediate portion, the recesses formed in the gravure roll preferably have an angle with respect to the width direction of the gravure roll in order to facilitate filling of the binder composition in the recesses and ensure stable coating. The angle of the recesses with respect to the width direction of the gravure roll is preferably 5° or more and 45° or less.

[0126] Examples of coating methods for forming the intermediate portion include gravure coating, inkjet printing, and flexographic printing. From the viewpoint of productivity, gravure coating and inkjet printing are preferred, and gravure coating, which allows high-speed coating and has excellent coating efficiency, is more preferred.

[0127] The step (1) can be carried out, for example, by a binder composition coating device described below.

[0128] The current collector is preferably long. When the current collector is long, the intermediate portion can be continuously formed while the current collector is being transported, resulting in excellent electrode production efficiency. Here, a "long" current collector refers to a current collector having a length that is 5 times or more its width, preferably 10 times or more its width, and specifically refers to a current collector having a length that can be wound into a roll for storage or transportation. There is no particular upper limit to the length of the current collector, and it can be, for example, 100,000 times or less its width.

[0129] The binder composition may contain a solvent. Here, the term "solvent" encompasses not only a medium that dissolves a solute but also a dispersion medium that disperses the solute. As the solvent, a conventionally known solvent can be used. Examples of solvents that the binder composition can contain include water and organic solvents. Among these, water or a solvent containing water (hereinafter also referred to as an aqueous solvent) is preferred because of its low environmental impact.

[0130] The first binder contained in the binder composition usually contains a polymer. The polymer that can be contained in the binder composition can usually be the polymer (1) that can be contained in the intermediate portion. The polymer (1) is preferably in the form of particles dispersed in a liquid binder composition containing a solvent. When the polymer (1) is in the form of particles dispersed in a liquid binder composition containing a solvent, the concentration of the first binder contained in the binder composition can be increased. This makes it possible to reduce the coating amount of the binder composition containing a solvent compared to the coating amount of the binder composition in which the polymer (1) is dissolved in a solvent in the step of forming the intermediate portion on the current collector, and the amount of solvent to be removed from the coating layer can be reduced. This reduces the drying equipment area and equipment installation costs, improves production speed, and reduces CO2 emissions. ２ The amount of the polymer (1) can be reduced. The polymer (1) obtained after the solvent has been removed from the binder composition may be deformed, but it is in the form of particles having grain boundaries. Hereinafter, the particulate polymer (1) will also be referred to as particulate polymer (1).

[0131] The particulate polymer (1) preferably has a median diameter within a specific range. Specifically, the median diameter D50 of the particulate polymer (1) is preferably 100 nm or more, more preferably 110 nm or more, even more preferably 120 nm or more, and is preferably 1000 nm or less, more preferably 800 nm or less, even more preferably 600 nm or less.

[0132] The median diameter D50 of the particulate polymer (1) can be measured in a wet state using a laser diffraction / light scattering particle size distribution analyzer. As a specific measuring method, the method described in the below-mentioned Examples (Method for measuring the median diameter D50 of a particulate polymer) can be adopted.

[0133] The polymer (1) can be produced by polymerizing a monomer corresponding to a monomer unit that can be contained in the polymer (1) by any method such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. When the polymer (1) is contained in the binder composition as a particulate polymer (1), the polymerization reaction may be carried out in a solvent in which the polymer (1) is insoluble or poorly soluble to obtain a dispersion of the particulate polymer (1), and the obtained composition containing the dispersion of the particulate polymer (1) and optional components may be used as the binder composition.

[0134] <Step (2)> In step (2), composite particles containing the active material and the second binder are supplied onto the current collector of the first intermediate body and the plurality of intermediate portions to form a composite particle layer. Typically, the composite particles are supplied as a powder. The composite particles are preferably supplied onto the current collector and the intermediate portions by dry coating, in which a dried powder is applied. Typically, composite particle powder is supplied onto the portions of the current collector where intermediate portions are not formed and the intermediate portions, to form a composite particle layer so as to cover the portions of the current collector where intermediate portions are not formed and the intermediate portions.

[0135] The composite particles can be supplied onto the first intermediate body by, for example, a composite particle supplying device described below.

[0136] (Composite particles) The composite particles contain an active material and a second binder. As the active material, a material that can function as an active material in an electrode for a lithium ion secondary battery can be used. The active material contained in the composite particles may be either a negative electrode active material or a positive electrode active material. When producing a negative electrode for a lithium ion secondary battery, composite particles containing a negative electrode active material are used, and when producing a positive electrode, composite particles containing a positive electrode active material are used.

[0137] As the positive electrode active material for a lithium ion secondary battery, an active material that can be doped and dedoped with lithium ions is used, and examples thereof include positive electrode active materials made of inorganic compounds, positive electrode active materials made of organic compounds, and composite materials that combine these.

[0138] Examples of the inorganic positive electrode active material include transition metal oxides, transition metal sulfides, and lithium-containing composite metal oxides containing lithium and a transition metal, such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

[0139] Examples of transition metal oxides include MnO and MnO ２ , V ２ O ５ , V ６ O １３ , TiO ２ , Cu ２ V ２ O ３ , amorphous V ２ O-P ２ O ５ , MoO ３ Among them, MnO, V are preferred in terms of cycle stability and capacity. ２ O ５ , V ６ O １３ and TiO ２ is preferred.

[0140] Examples of transition metal sulfides include TiS ２ , TiS ３ , amorphous MoS ２ , FeS, etc.

[0141] Examples of the lithium-containing composite metal oxide include lithium-containing composite metal oxides having a layered structure, lithium-containing composite metal oxides having a spinel structure, and lithium-containing composite metal oxides having an olivine structure. Examples of the lithium-containing composite metal oxides having a layered structure include lithium-containing cobalt oxide (LiCoO ２ ), lithium-containing nickel oxide (LiNiO ２ ), Co—Ni—Mn lithium composite oxide, Ni—Mn—Al lithium composite oxide, Ni—Co—Al lithium composite oxide, etc. Examples of lithium-containing composite metal oxides having a spinel structure include lithium manganate (LiMn ２ O ４ ), Li[Mn ３／２ M １ １／２ ]O ４ (Here, M １ represents a transition metal other than Mn, such as Cr, Fe, Co, Ni, or Cu. Examples of lithium-containing composite metal oxides having an olivine structure include Li Ｘ M ２ P.O. ４ (In the formula, M ２ represents at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B, and Mo, and X represents a number satisfying 0≦X≦2.

[0142] Examples of the positive electrode active material made of an organic compound include conductive polymers such as polyacetylene and poly-p-phenylene.

[0143] Alternatively, for example, an iron-based oxide may be reduced and fired in the presence of a carbon source to produce a composite material covered with a carbon material, and this composite material may be used as a positive electrode active material. Although iron-based oxides tend to have poor electrical conductivity, such a composite material can be used as a high-performance positive electrode active material.

[0144] The positive electrode active material may be used alone or in combination of two or more. Also, a mixture of the inorganic compound and the organic compound described above may be used as the positive electrode active material.

[0145] Examples of the negative electrode active material for a lithium ion secondary battery include graphite and the same examples as those given above as the optional active material that can be contained in the composite layer. The negative electrode active material may be used alone or in combination of two or more.

[0146] When obtaining an electrode for a lithium ion secondary battery having a composite layer containing graphite in which the ratio (I(110) / I(002)) is within a specific range, it is preferable to produce a lithium ion secondary battery by a production method including step (2). This makes it possible to obtain an electrode that can realize a lithium ion secondary battery with excellent rapid charging characteristics. Compared to wet-coating an active material composition containing graphite and a solvent as an active material onto a first intermediate to form a layer of the active material composition and then obtaining a composite layer from the layer of the active material composition, when a composite particle layer is formed by a dry process using composite particles containing graphite as an active material, as in step (2), it is thought that graphite is less likely to be oriented on the first intermediate. As a result, it is thought that graphite is less likely to be oriented in the composite layer of the electrode, and the ratio (I(110) / I(002)) for graphite in the composite layer falls within the specific range.

[0147] Typically, the active material may be particles formed from the materials described above. The active material preferably has a median diameter D50 within a specific range. Specifically, the median diameter D50 of the active material is preferably 0.1 μm or more and preferably 50 μm or less.

[0148] The median diameter D50 of the active material can be measured in a dry state using a laser diffraction / light scattering particle size distribution measuring device.

[0149] The amount of the active material relative to 100% by weight of the composite particles is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and is preferably 99% by weight or less, more preferably 98.5% by weight or less, even more preferably 98% by weight or less. When the amount of the active material is within this range, the rapid charging characteristics and cycle characteristics of the lithium ion secondary battery can be effectively improved.

[0150] The second binder contained in the composite particles may be the binder (second binder) usually contained in the composite layer. Examples of the second binder contained in the composite particles include the same examples as the examples of the second binder contained in the composite layer.

[0151] The composite particles may contain a dispersant as an optional component. The second binder contained in the composite particles may function as a dispersant. Examples of dispersants include cellulose-based polymers such as carboxymethyl cellulose and methyl cellulose, and ammonium salts or alkali metal salts thereof. These dispersants may be used alone or in combination.

[0152] The composite particles may contain a conductive material as an optional component. Examples of the conductive material include the same examples as those described above. These conductive materials may be used alone or in combination.

[0153] The composite particles can be produced by granulating the active material, the second binder, and any optional components that may be included as needed. Examples of the method for producing the composite particles are not particularly limited, and include known granulation methods such as fluidized bed granulation, spray-drying granulation, stirring granulation, tumbling granulation, and tumbling fluidized bed granulation.

[0154] Each composite particle is preferably in the form of a secondary particle formed by aggregating a plurality of primary particles, specifically, a plurality (preferably several to several tens) of active materials and optional components bound together by a second binder.

[0155] From the viewpoint of easily obtaining a composite layer of the desired thickness, the median diameter (D50) of the composite particles is preferably 30 μm or more, more preferably 50 μm or more, even more preferably 60 μm or more, and is preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 250 μm or less.

[0156] The median diameter D50 of the composite particles can be measured using a laser diffraction / light scattering particle size distribution analyzer. A specific measurement method that can be used is the method described in the Examples below (Method for measuring the median diameter D50 of the composite particles).

[0157] The step (2) may include a step (2-1) of leveling the composite particles supplied onto the first intermediate to form a composite particle layer. The step (2-1) can be performed, for example, by using a squeegee member described later.

[0158] <Step (3)> In step (3), the composite particle layer is pressurized to form the composite layer, thereby obtaining the electrode. The pressurization of the composite particle layer in step (3) can be performed, for example, by a composite particle layer pressurizing device described below.

[0159] <Optional Steps> The electrode manufacturing method according to this embodiment may include optional steps other than the steps described above. For example, the manufacturing method according to this embodiment may include a step of drying the intermediate portion formed on the first intermediate after step (1). For example, the current collector may be long, and step (1) may be performed while transporting the long current collector. The transport of the long current collector may be performed, for example, by a transport device described below. For example, the first intermediate may be long, and step (2) may be performed while transporting the long first intermediate. The transport of the long first intermediate may be performed, for example, by a transport device described below.

[0160] <Electrode Manufacturing Apparatus> The electrode manufacturing method according to this embodiment can be performed using any manufacturing apparatus. For example, the electrode manufacturing method can be performed using a manufacturing apparatus including a conveying device, a binder composition applicator, a composite particle supplying device, a squeegee member, and a composite particle layer pressurizing device. The conveying device is configured to convey the current collector, specifically, for example, a conveying roll. The binder composition applicator is configured to apply the binder composition onto the current collector, specifically, for example, a gravure coater. The composite particle supplying device is configured to supply the composite particles onto the first intermediate, specifically, for example, a hopper. The squeegee member is configured to level the layer of composite particles supplied onto the first intermediate, specifically, for example, a squeegee blade, a roller squeegee, or the like. The composite particle layer pressurizing device is configured to pressurize the composite particle layer, specifically, for example, a pair of pressure rolls. The manufacturing apparatus may further include any component, device, or other element.

[0161] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be practiced with any modifications within the scope of the claims of the present invention and their equivalents.

[0162] In the following description, the "%" and "parts" that represent amounts are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature (20°C ± 15°C) and atmospheric pressure (1 atm) unless otherwise specified.

[0163] In the following description, first, the evaluation methods are described. Then, the materials used in the manufacture of electrodes for lithium ion secondary batteries are described. Then, the manufacture of electrodes for lithium ion secondary batteries using these materials is described. Finally, the evaluation results of examples and comparative examples are described.

[0164] <Evaluation Method> (Glass Transition Temperature) An aqueous dispersion containing a polymer was dried for 3 days in an environment of 50% humidity and 23°C to 25°C to obtain a film having a thickness of 1±0.3 mm. This film was subjected to vacuum drying at 120°C for 10 hours. Thereafter, the glass transition temperature (°C) of the dried film was measured as a sample in accordance with JIS K7121 using a differential scanning calorimeter ("DSC6220", manufactured by SII NanoTechnology Inc.) at a measurement temperature of -100°C to 180°C and a heating rate of 5°C / min.

[0165] (Method for measuring median diameter D50 of particulate polymer) The median diameter of the particulate polymer (A) prepared in the examples and comparative examples was measured by a laser diffraction method. Specifically, an aqueous dispersion of the particulate polymer (A) adjusted to a solid content concentration of 0.1% by mass was used as a sample. Then, in the particle size distribution (volume basis) measured using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, Inc., product name "LS-13 320"), the particle diameter (D50) at which the cumulative frequency calculated from the small diameter side was 50% was taken as the median diameter D50 of the particulate polymer (A).

[0166] (Method for measuring the median diameter D50 of composite particles) The median diameter D50 of the composite particles was measured using a laser diffraction / scattering particle size distribution analyzer ("MT3200II" manufactured by Microtrac-Bell). Specifically, dry particle size measurement (volume basis) was performed by the laser diffraction / scattering method using the laser diffraction / scattering particle size distribution analyzer. The pressure of the dispersion air during measurement was set to 0.05 MPa. In the obtained measurement results, the particle diameter at which the cumulative frequency calculated from the smallest diameter side was 50% was taken as the median diameter D50.

[0167] (Initialization, Battery Capacity) After injecting the electrolyte, the lithium-ion secondary batteries obtained in the Examples and Comparative Examples were left standing at 25°C for 5 hours. Next, they were charged at 7 mA at 25°C using a constant current method to a cell voltage of 3.3 V, and then aged at 60°C for 12 hours. Then, they were charged at 15 mA at 25°C using a constant current-constant voltage method (upper limit cell voltage: 4.20 V) and discharged to 3.00 V using a constant current method of 15 mA. Next, they were again charged at 25°C using a constant current-constant voltage method at 15 mA to a cell voltage of 4.20 V, left standing for 10 minutes, and then again discharged at 15 mA using a constant current to a cell voltage of 3.00 V. This charge-discharge cycle at 15 mA over a cell voltage range of 4.20 V to 3.00 V was repeated twice to initialize the batteries. The discharge capacity after two charge-discharge cycles was 72 mAh. The discharge capacity of the battery at this time was 72 mAh, which was defined as the current value when discharging the battery in 1 hour, i.e., the current value at a 1-hour rate (1.0 C) was 72 mA. The battery was then charged to 4.20 V using a constant current-constant voltage charging method at a current value of 14 mA, and then discharged at a constant current value of 7.2 mA (10-hour rate) to a cell voltage of 3.00 V, resulting in a discharge capacity of 72 mAh (C0). The battery capacity per unit area of ​​the positive electrode (per unit area of ​​the portion where the negative electrode and positive electrode face each other) was then calculated.

[0168] (Rapid Charge Characteristics: Charge Rate at First Rapid Charge Cycle) The lithium ion secondary battery initialized as described above was left standing at 25°C for 1 hour, and then charged at 4.0 C, i.e., a constant current of 0.25 hour rate, to a cell voltage of 4.20 V. After leaving the battery standing for 30 minutes, the battery was discharged at 25°C and a constant current of 0.2 C (5 hour rate) to a cell voltage of 3.00 V. The discharge capacity (battery capacity) C1 at this time was measured. The charge rate Rc at 4.0 C, i.e., a 0.25 hour rate, was calculated according to the following formula: Rc (%) = (C1 / C0) × 100

[0169] (Cycle Characteristics) A battery cell different from the battery cell used to evaluate the rapid charge characteristics was prepared. This battery cell was initialized and then discharged at a 10-hour rate. This battery cell was left standing at 45°C for 1 hour, then charged to 4.20 V using a 1.0 C constant current-constant voltage charging method. After leaving standing for 10 minutes, it was discharged to 3.00 V using a 1.0 C constant current method at 45°C and left standing for 10 minutes. The discharge capacity at this time was designated as C0(45). The charge-discharge operation was repeated, and the capacity C200(45) after 200 cycles was measured. The capacity retention rate Rc(45) was calculated according to the following formula: Rc(45) (%) = (C200(45) / C0(45)) × 100. A higher value of this capacity retention rate Rc(45) indicates better cycle characteristics.

[0170] (Orientation) A battery cell separate from the battery cell used to evaluate the rapid charge characteristics or cycle characteristics was prepared. This battery cell was initialized, discharged at a 10-hour rate, and then disassembled. The negative electrode pieces were removed, repeatedly rinsed with DEC, and air-dried. The orientation of graphite in the negative electrode composite layer was evaluated using an X-ray diffractometer. Measurements were performed under the following conditions to obtain the intensity I(110) of the peak based on the (110) plane of graphite appearing near 77.3° and the intensity I(002) of the peak based on the (002) plane of graphite in the c-axis direction appearing near 26.4°. The ratio I(110) / I(002) was measured and used as an index of the orientation of graphite in the composite layer of the negative electrode. Measurement equipment: X-ray diffraction equipment "SmartLab" (manufactured by Rigaku Corporation) Measurement method: Focusing method Target element: Cu X-ray type: Kα Entrance slit: 1 / 2 Receiving slit 1: Open Receiving slit 2: 20.1 mm Scan method: 1D Primary beam: Standard Entrance monochromator: None Receiving monochromator: None Tube voltage: 45 kV Tube current: 200 mA Measurement angle: 20° to 90° Step width: 0.02 Scanning speed: 20° / min

[0171] (Measurement of the Distance Between Peripherals and Area S of Intermediate Portions) The distance between the peripheral edges of the intermediate portions was measured using the negative electrode whose orientation had been evaluated. A weak adhesive tape was attached to the surface of the composite layer provided on the negative electrode and then peeled off, thereby partially removing the composite layer from the electrode surface. This process was carefully repeated while being careful not to break the current collector, resulting in an electrode in which the composite layer remained only on the intermediate portions on the current collector. The surface of this sample was observed with a scanning electron microscope-energy dispersive X-ray analyzer (SEM-EDX), and it was confirmed that multiple intermediate portions remained on the current collector. The state in which the composite layer was present only on the intermediate portions on the current collector was equivalent to the state of the intermediate portions after the intermediate portion formation process in the electrode manufacturing process. The multiple intermediate portions were approximately rectangular. At an observation magnification of 60x, 10 intermediate portions were randomly selected, and the distance between the peripheral edges of the intermediate portions surrounding each intermediate portion was determined. For each of the 10 intermediate portions, adjacent intermediate portions were identified. For each of the 10 intermediate portions, the shortest distance D between the peripheries of the adjacent intermediate portions is Ｓ and the longest distance D Ｌ The distance D of the obtained 10 points was calculated. Ｓ The arithmetic mean value of Ｓ (ave), and the distance D Ｌ The arithmetic mean value of Ｌ In addition, 10 intermediate portions were arbitrarily selected from the observation range, and their areas S1 to S10 were measured, and the arithmetic mean value of the areas S1 to S10 was taken as the area S of the intermediate portion of the electrode.

[0172] <Production Example P1: Production of Particulate Polymer (A)> 70 parts of ion-exchanged water, 0.15 parts of polyoxyethylene lauryl ether (manufactured by Kao Chemical Corporation, "Emulgen (registered trademark) 120") as an emulsifier, and 0.5 parts of ammonium persulfate were supplied to a reactor (A) equipped with a stirrer, and the gas phase was replaced with nitrogen gas, followed by heating to 60°C. Meanwhile, in a separate vessel, 50 parts of ion-exchanged water, 0.5 parts of polyoxyethylene lauryl ether (manufactured by Kao Chemical Corporation, "Emulgen (registered trademark) 120") as an emulsifier, 65.6 parts of 2-ethylhexyl acrylate (2-EHA) as a (meth)acrylic acid alkyl ester monomer, 30 parts of styrene (ST) as an aromatic monovinyl monomer, 1.2 parts of allyl glycidyl ether (AGE) as an epoxy / N-methylol group-containing crosslinkable monomer, 0.2 parts of allyl methacrylate (AMA) as a polyvalent ethylenically unsaturated crosslinkable monomer, and 3 parts of acrylic acid as an ethylenically unsaturated carboxylic acid monomer unit were mixed to obtain a monomer composition. This monomer composition was continuously added to the reactor (A) over 4 hours to carry out polymerization. During the addition, the reaction was carried out at 70°C. After completion of the addition, the mixture was further stirred at 80°C for 3 hours to terminate the reaction, and an aqueous dispersion containing a particulate polymer (A) was obtained. The glass transition temperature of the obtained particulate polymer (A) was measured, and it was confirmed that the glass transition temperature was only observed at one point (-28°C), and that the particulate polymer (A) was a random copolymer. The median diameter D50 of the particulate polymer (A) was 160 nm.

[0173] <Production Example NE1: Production of Negative Electrode Composite Particles 1> (NE1-1) Preparation of Negative Electrode Slurry Composition 1 To a planetary mixer equipped with a disperser (manufactured by Primix Corporation, "Hivis Dispermix 3D-2 type"), 97.0 parts of artificial graphite, which is a carbonaceous material, and 0.8 parts in solids equivalent of a 4% aqueous solution of a lithium salt of acrylic acid-acrylamide copolymer (P(AA-Aam)-Li), which is a water-soluble polymer, were added as negative electrode active materials. Then, ion-exchanged water was added to this mixture to adjust the solids concentration to 65%, and then the mixture was mixed at 25°C for 60 minutes to obtain a mixed solution. Ion-exchanged water was added to the mixed solution, and the mixture was mixed for 3 minutes, and then diluted to a solids concentration of 60%. Next, 0.8 parts of a dispersion of acetylene black (DENKA BLACK (registered trademark), trade name "Li-100", manufactured by Denka Co., Ltd.) equivalent to DENKA BLACK Li-100 was added. The added dispersion contained 0.1 parts of sodium salt of carboxymethyl cellulose, a water-soluble polymer. Furthermore, ion-exchanged water was added and mixed for 3 minutes, and the mixture was diluted to a solids concentration of 58%. Next, 1.3 parts of a 40% aqueous dispersion of a styrene-butadiene-methacrylic acid copolymer, which is a water-insoluble conjugated diene polymer (SBR copolymer), equivalent to solids was added. Furthermore, ion-exchanged water was added to adjust the final solids concentration of the mixture to 50%, and then the mixture was mixed for another 10 minutes. Thereafter, the mixture was degassed under reduced pressure to obtain a negative electrode slurry composition 1.

[0174] (NE1-2) Preparation of Composite Particles 1 for Negative Electrode The obtained negative electrode slurry composition 1 was spray-dried using a spray dryer ODB-25 (tower diameter 2,500 mm) manufactured by Okawara Chemical Engineering Co., Ltd. under the conditions of atomizer: rotating disk type (diameter: 84 mm), rotation speed: 21,000 rpm, hot air temperature (outlet temperature): 90°C to prepare composite particles (spray drying step). Next, the obtained composite particles were classified using a sieve with a nominal mesh size of 150 μm (JIS Z8801-1) (classification step), to obtain composite particles 1 for negative electrode. The median diameter D50 of composite particles 1 for negative electrode was 80 μm.

[0175] <Production Example NE2: Production of Negative Electrode Composite Particles 2> (NE2-1) Preparation of Negative Electrode Slurry Composition 2 In (NE1-1) of Production Example NE1, the amount of artificial graphite was changed from 97.0 parts to 93.7 parts, and 3.3 parts of SiOx, a silicon atom-containing active material, was further added to the planetary mixer as the negative electrode active material. Except for the above, the same operation as in (NE1-1) was performed to obtain a negative electrode slurry composition 2.

[0176] (NE2-2) Preparation of Negative Electrode Composite Particles 2 In (NE1-2) of Production Example NE1, negative electrode slurry composition 2 was used instead of negative electrode slurry composition 1. Except for the above, the same operation as in (NE1-2) was performed to obtain negative electrode composite particles 2. The median diameter D50 of negative electrode composite particles 2 was 78 μm.

[0177] <Production Example NE3: Production of Negative Electrode Composite Particles 3> 94.5 parts of artificial graphite, which is a carbonaceous material, and 3.3 parts of SiOx, which is a silicon atom-containing active material, were charged into an agitation granulator (Eirich Intensive Mixer, manufactured by Nippon Eirich Co., Ltd.), as negative electrode active materials. 0.8 parts, in terms of solid content, of a 4% aqueous solution of a lithium salt of acrylic acid-acrylamide copolymer (P(AA-Aam)-Li), which is a water-soluble polymer, and a dispersion of acetylene black (DENKA BLACK (registered trademark) Li-10, manufactured by Denka Co., Ltd.) were then added. A mixture of 0.8 parts in terms of Li-100 equivalent (the added dispersion contained 0.1 parts of carboxymethyl cellulose sodium salt) and 1.3 parts in terms of solids equivalent of a 40% aqueous dispersion of a styrene-butadiene-methacrylic acid copolymer, a water-insoluble polymer, was added and stirred at a predetermined rotation speed to obtain a precursor of anode composite particle 3. Thereafter, the water contained in the precursor of anode composite particle 3 was removed by drying, and then the mixture was classified using a sieve with a nominal mesh size of 150 μm (JIS Z8801-1) (classification step) to obtain anode composite particle 3. The median diameter D50 of anode composite particle 3 was 80 μm.

[0178] <Production Example PE1: Production of Positive Electrode 1> (PE1-1) Preparation of Positive Electrode Slurry Composition 1 In a planetary mixer, NMC532 (LiNi) ０．５Mn ０．３ Co ０．２ O ２ ), 2.0 parts in solids equivalent of carbon black (manufactured by Denka Co., Ltd., trade name "Li-100") as a conductive material, 0.4 parts in solids equivalent of dispersant (manufactured by Zeon Corporation, trade name "BM-720H"), and 1.1 parts in solids equivalent of polyvinylidene fluoride (manufactured by Solvay, trade name "Solef5130") as an additional component were added and mixed, and N-methyl-2-pyrrolidone (NMP) was gradually added and mixed with stirring to obtain a positive electrode slurry composition 1. The viscosity of the positive electrode slurry composition 1 measured by a Brookfield viscometer was 3,600 mPa s at 60 rpm (rotor M4) and 25±3°C.

[0179] (PE1-2) Coating Step: The positive electrode slurry composition 1 was applied to a 15 μm thick aluminum foil current collector using a comma coater so that the weight of the mixture layer after drying was 20.5 mg / cm. ２ The slurry composition on the aluminum foil was dried to obtain a positive electrode blank having a positive electrode composite layer formed on the current collector. Thereafter, the positive electrode composite layer side of the prepared positive electrode blank was subjected to a roll press in an environment at a temperature of 25±3°C to obtain a positive electrode composite layer density of 3.40 g / cm. ３ A positive electrode 1 of the above formula was obtained.

[0180] <Production Example PE2: Production of Positive Electrode 2> In Production Example PE1 (PE1-1), NMC811 (LiNi) was used as the positive electrode active material instead of NMC532. ０．８ Mn ０．１ Co ０．１ O ２ In (PE1-2), the positive electrode slurry composition 2 was used, and the coating amount was 19.5 mg / cm ２ Except for the above, the same procedure as in Production Example PE1 was carried out to obtain a positive electrode 2.

[0181] <Production Example PE3: Production of Positive Electrode 3> In Production Example PE1 (PE1-1), NMC811 (LiNi) was used as the positive electrode active material instead of NMC532. ０．８ Mn ０．１ Co ０．１ O２ In (PE1-2), the positive electrode slurry composition 2 was used, and the coating amount was 21.4 mg / cm ２ Except for the above, the same procedure as in Production Example PE1 was carried out to obtain a positive electrode 3.

[0182] Example 1 (1-1) Preparation of Negative Electrode 1 An electrode manufacturing apparatus was prepared, equipped with a conveying device, a gravure coating / drying device equipped with a gravure roll, a hopper, a roller squeegee, and a pair of pressure rolls. Furthermore, water was added to the aqueous dispersion containing the particulate polymer (A) to adjust the concentration, thereby preparing a liquid binder composition. While a long negative electrode current collector (using copper foil with a thickness of 10 μm) was conveyed by the conveying device, the binder composition was coated in an island pattern on one side of the negative electrode current collector using a gravure coating / drying device, and then dried to form multiple binder-coated portions (intermediate portions) on the negative electrode current collector, thereby obtaining a first intermediate (step (1)). The pattern of recesses on the peripheral surface of the gravure roll was a dot-like pattern, such that multiple intermediate portions were arranged in an island shape on the negative electrode current collector, with the distance between the peripheries of adjacent intermediate portions being the distance shown in Table 1, and the area S of the intermediate portions being the value shown in Table 1. When the binder-coated portion (middle portion) formed on the negative electrode current collector was observed with an electron microscope (model name "JSM-7800F" manufactured by JEOL Ltd.), the binder-coated portion (middle portion) was found to be approximately rectangular and arranged in islands, specifically dots, on the current collector. Furthermore, analysis of the electron microscope observation image revealed that the area of ​​the binder-coated portion (middle portion) was 5,600 μm ２ In the conveyance direction of the negative electrode current collector, the distance between the peripheries of the binder-coated portions arranged in a dot pattern was 54 μm (D Ｓ (equivalent to ave) ~ 62 μm (D Ｌ (equivalent to ave).

[0183] Next, negative electrode composite particles 1 were supplied from a hopper onto the negative electrode current collector and the plurality of binder-coated portions (intermediate portions) of the obtained first intermediate, and then a roller squeegee was applied to the supplied powder of negative electrode composite particles 1 while rotating to level it, thereby forming a layer of negative electrode composite particles 1. By this operation, a second intermediate was obtained in which a layer of negative electrode composite particles 1 was formed on the first intermediate (step (2)).

[0184] Next, the second intermediate was passed through a gap between the peripheral surfaces of a pair of pressure rolls to press the second intermediate, thereby obtaining a first negative electrode raw sheet (step (3)). As a result, the layer of the negative electrode composite particles 1 contained in the second intermediate was pressed, and a first negative electrode composite layer was obtained. The basis weight of the first negative electrode composite layer was 12.5 mg / cm. ２ The first negative electrode substrate sheet included a negative electrode current collector, a plurality of intermediate portions arranged in an island shape on one surface of the negative electrode current collector, and a first negative electrode composite layer arranged on one surface of the negative electrode current collector and on the plurality of intermediate portions.

[0185] Furthermore, the same operations as those in the steps (1), (2), and (3) were repeated to form a plurality of intermediate portions and a second negative electrode composite layer on the other surface of the negative electrode current collector of the first negative electrode raw sheet, thereby obtaining a second negative electrode raw sheet.

[0186] The second negative electrode raw sheet was further compressed by a pressure roll to a density of 1.65 g / cm ３ A negative electrode 1 was prepared.

[0187] (1-2) Fabrication of Lithium-Ion Secondary Battery

[0046] A negative electrode piece was fabricated from the negative electrode 1 fabricated above. The negative electrode piece had a rectangular negative electrode composite layer measuring 4.0 cm × 3.0 cm, and a negative electrode composite layer non-forming portion was provided on the outer side of the edge of the negative electrode composite layer as a current collecting tab. The negative electrode piece was vacuum dried at 150°C for 4 hours.

[0188] Next, a positive electrode piece was produced from positive electrode 1, in which the positive electrode composite material layer was a rectangle of 3.8 cm x 2.8 cm and a positive electrode composite material layer non-forming portion was provided as a current collecting tab on the outer side of the edge of the positive electrode composite material layer.

[0189] A single-layer separator substrate made of polypropylene was prepared as the separator.

[0190] A positive electrode piece was laminated on both sides of the negative electrode piece with a separator interposed therebetween so that the surface on which the positive electrode composite layer was formed faced the surface on which the negative electrode composite layer was formed, to prepare a device. The area of ​​the portion where the negative electrode and the positive electrode faced each other, specifically, the portion where the positive electrode composite layer of the positive electrode faced the negative electrode composite layer, was 21.28 cm ２ After ultrasonic welding, terminals with sealant were welded to the current collecting tabs of the negative and positive electrode pieces, respectively, the element was placed in an aluminum packaging material, and the aluminum packaging material was then heat-sealed on three sides, leaving one side open, to produce a laminated lithium-ion secondary battery cell before electrolyte injection. The battery cell was then vacuum-dried at 60°C for 10 hours, and then a 1.0 M LiPF 600 was added as an electrolyte. ６ A solution (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2 volume % vinylene carbonate (solvent ratio)) was filled in. Furthermore, the opening of the aluminum packaging material was heat-sealed under reduced pressure to complete a stacked laminate-type lithium ion secondary battery (equivalent to an initial charge capacity of 78 mAh).

[0191] The resulting lithium ion secondary battery was initialized and evaluated by the same method. The discharge capacity of the battery after initialization at a 10-hour rate was 72 mAh, and the battery capacity per unit area of ​​the portion where the negative electrode and the positive electrode faced each other was 3.3 mAh / cm. ２ It was.

[0192] Examples 2 to 6 The gravure roll used in (1-1) of Example 1 was replaced with another gravure roll. This gravure roll had a pattern of recesses on its peripheral surface such that the distance between the peripheries of adjacent intermediate portions and the area S of the intermediate portions in the negative electrode of the resulting lithium-ion secondary battery were the values ​​shown in Table 1. Except for the above, the same procedure as in Example 1 was repeated to complete a stacked laminate-type lithium-ion secondary battery. The resulting lithium-ion secondary battery was initialized and evaluated using the method described above. The lithium-ion secondary batteries obtained in Examples 2 to 6 each had a discharge capacity of 72 mAh at a 10-hour rate after initialization, and a battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.3 mAh.

[0193] Example 7 (7-1) Fabrication of Negative Electrode In (1-1) of Example 1, the gravure roll was changed to the same gravure roll as used in Example 2. The negative electrode composite particles 2 were used instead of the negative electrode composite particles 1. The basis weight of each of the first negative electrode mixture layer and the second negative electrode mixture layer was 11.5 mg / cm. ２ Except for the above, the same procedure as in Example 1 (1-1) was carried out to prepare a negative electrode.

[0194] (7-2) Preparation of Lithium-Ion Secondary Battery In (1-2) of Example 1, the negative electrode prepared in (7-1) was used instead of the negative electrode 1, and the positive electrode 2 was used instead of the positive electrode 1.

[0195] Except for the above, the same procedure as in Example 1 (1-2) was followed to complete a stacked laminated lithium ion secondary battery. The obtained lithium ion secondary battery was initialized and evaluated in the same manner as described above, except that the lower limit voltage of the cell was changed to 2.50 V. The discharge capacity of the battery after initialization at a 10-hour rate discharge was 77 mAh, and the battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.6 mAh / cm. ２ It was.

[0196] Example 8 (8-1) Fabrication of Negative Electrode In (1-1) of Example 1, the gravure roll was changed to the same gravure roll as used in Example 2. The negative electrode composite particles 2 were used instead of the negative electrode composite particles 1. The basis weight of each of the first negative electrode mixture layer and the second negative electrode mixture layer was set to 13 mg / cm. ２ Except for the above, the same procedure as in Example 1 (1-1) was carried out to prepare a negative electrode.

[0197] (8-2) Preparation of Lithium-Ion Secondary Battery In (1-2) of Example 1, the negative electrode prepared in (8-1) was used instead of the negative electrode 1, and the positive electrode 3 was used instead of the positive electrode 1.

[0198] Except for the above, a stacked laminated lithium ion secondary battery was completed in the same manner as in (1-2) of Example 1. The lithium ion secondary battery obtained was initialized and evaluated in the same manner as above, except that the lower limit voltage of the battery was changed to 2.50 V. The discharge capacity of the battery after initialization at a 10-hour rate discharge was 86 mAh, and the battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 4.0 mAh / cm. ２ It was.

[0199] Example 9 (9-1) Fabrication of Negative Electrode In (1-1) of Example 1, the gravure roll was changed to the same gravure roll as used in Example 2. The negative electrode composite particles 3 were used instead of the negative electrode composite particles 1. The basis weight of each of the first negative electrode mixture layer and the second negative electrode mixture layer was 11.5 mg / cm. ２ Except for the above, the same procedure as in Example 1 (1-1) was carried out to prepare a negative electrode.

[0200] (9-2) Preparation of Lithium Ion Secondary Battery In (1-2) of Example 1, the negative electrode prepared in (9-1) was used instead of the negative electrode 1.

[0201] Except for the above, the same procedure as in Example 1 (1-2) was followed to complete a stacked laminated lithium ion secondary battery. The resulting lithium ion secondary battery was initialized and evaluated by the method described above. The discharge capacity of the battery after initialization was 78 mAh at a 10-hour rate discharge, and the battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.6 mAh / cm. ２ It was.

[0202] Comparative Examples 1 to 4 The gravure roll used in (1-1) of Example 1 was replaced with another gravure roll. This gravure roll had a pattern of recesses on its peripheral surface such that the distance between the peripheries of adjacent intermediate portions and the area S of the intermediate portions in the negative electrode of the resulting lithium-ion secondary battery were the values ​​shown in Table 3. Except for the above, the same procedure as in Example 1 was repeated to complete a stacked laminate-type lithium-ion secondary battery. The resulting lithium-ion secondary battery was initialized and evaluated using the method described above. The lithium-ion secondary batteries obtained in Comparative Examples 1 to 4 each had a discharge capacity of 72 mAh at a 10-hour rate after initialization, and a battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.3 mAh.

[0203] Comparative Example 5 The gravure roll used in (1-1) of Example 1 was replaced with a different gravure roll. This gravure roll had a pattern of recesses on its peripheral surface, in which multiple band-shaped intermediate portions extending at a 45° angle relative to the conveyance direction of the negative electrode current collector and portions without band-shaped intermediate portions extending at a 45° angle relative to the conveyance direction of the negative electrode current collector were alternately formed on the negative electrode current collector. Furthermore, the recesses of this gravure roll had a pattern such that, in the negative electrode of the resulting lithium-ion secondary battery, the spacing between the edges of adjacent band-shaped intermediate portions was the value shown in Table 3. Because the multiple intermediate portions formed by this gravure roll were band-shaped, they were not arranged discretely, i.e., in an island-like manner. A negative electrode was obtained in the same manner as in (1-1) of Example 1, except for the above-mentioned points. Using the resulting negative electrode, a lithium-ion secondary battery was obtained in the same manner as in (1-2), completing a stacked laminate-type lithium-ion secondary battery. The obtained lithium ion secondary battery was initialized by the above-mentioned method and evaluated. The lithium ion secondary battery obtained in Comparative Example 5 had a discharge capacity of 72 mAh at a 10-hour rate discharge after initialization, and a battery capacity per unit area of ​​the portion where the negative electrode and the positive electrode faced each other was 3.3 mAh.

[0204] Comparative Example 6 (C6-1) Preparation of Negative Electrode An electrode manufacturing apparatus equipped with a conveying device, a gravure coater / drying device equipped with a gravure roll, a comma-type coater for applying the binder composition, and a dryer was prepared. Furthermore, water was added to the aqueous dispersion containing the particulate polymer (A) to adjust the concentration, and a liquid binder composition was prepared. While a long negative electrode current collector (using copper foil with a thickness of 10 μm) was conveyed by the conveying device, the binder composition was applied in an island pattern to one side of the negative electrode current collector using a gravure coater, and then dried to form multiple binder-coated portions (intermediate portions) on the negative electrode current collector, thereby obtaining a first intermediate (step (C1)). The pattern of recesses on the peripheral surface of the gravure roll was a dot-like pattern such that multiple intermediate portions were arranged in an island shape on the negative electrode current collector, with the distance between the peripheries of adjacent intermediate portions being the distance shown in Table 4, and the area S of the intermediate portions being the value shown in Table 4.

[0205] The negative electrode slurry composition 1 was dried to a weight per unit area of ​​12.5 mg / cm ２ The surface on which the intermediate portion was formed was coated and dried to form an intermediate portion and a negative electrode composite layer on one surface of the current collector (step (C2)). Next, an intermediate portion and a composite layer were formed on the other surface of the current collector in the same manner as above, thereby producing a negative electrode raw sheet having an intermediate portion and a composite layer formed on both surfaces of the current collector. The obtained negative electrode raw sheet was compressed by applying pressure with a pressure roll to a density of 1.65 g / cm. ３ A negative electrode was fabricated.

[0206] (C6-2) Preparation of Lithium-Ion Secondary Battery The obtained negative electrode was used instead of negative electrode 1, and the same operation as in (1-2) of Example 1 was carried out to complete a stacked laminate type lithium-ion secondary battery. The obtained lithium-ion secondary battery was initialized by the method described above and evaluated. The obtained lithium-ion secondary battery had a discharge capacity of 72 mAh at a 10-hour rate discharge after initialization, and a battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.3 mAh.

[0207] Comparative Example 7 The gravure roll used in (C6-1) of Comparative Example 6 was replaced with another gravure roll. This gravure roll had a pattern of recesses on its circumferential surface such that the distance between the peripheries of adjacent intermediate portions and the area S of the intermediate portions in the negative electrode of the resulting lithium ion secondary battery were the values ​​shown in Table 4. The density of the negative electrode was 1.50 g / cm. ２ The coating amount of negative electrode slurry composition 1 was adjusted so that the coating amount of the negative electrode slurry composition 1 was 0.05g. Except for the above, the same operation as in Comparative Example 6 was performed to complete a stacked laminate type lithium ion secondary battery. The obtained lithium ion secondary battery was initialized by the above-mentioned method and evaluated. The obtained lithium ion secondary battery had a discharge capacity of 72 mAh at a 10-hour rate discharge after initialization, and a battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.3 mAh.

[0208] Comparative Example 8 The gravure roll used in (C6-1) of Comparative Example 6 was replaced with another gravure roll. This gravure roll had a pattern of recesses on its peripheral surface such that, in the negative electrode of the obtained lithium-ion secondary battery, the distance between the peripheries of adjacent intermediate portions and the area S of the intermediate portions were the values ​​shown in Table 4. Negative electrode slurry composition 1 was replaced with negative electrode slurry composition 2, and the basis weight per side was 11.5 mg / cm. ２ Otherwise, the same procedure as in Comparative Example 6 was carried out to complete a stacked laminated lithium ion secondary battery. The obtained lithium ion secondary battery was initialized and evaluated in the same manner as above, except that the lower limit voltage of the battery was changed to 2.50 V. The discharge capacity of the obtained lithium ion secondary battery after initialization was 78 mAh at a 10-hour rate discharge, and the battery capacity per unit area of ​​the portion where the negative electrode and positive electrode faced each other was 3.6 mAh.

[0209] <Evaluation Results> The evaluation results are shown in the table below. The abbreviations in the table have the following meanings: "Area capacity": Battery capacity (discharge capacity) per unit area of ​​the portion where the negative electrode and positive electrode face each other "Rapid charge characteristics: charge rate": Charge rate Rc at the first cycle of rapid charge "Cycle characteristics": Capacity retention rate "Dry type": Manufacturing method including step (2) "Wet type": Manufacturing method including step (C2)

[0210]

[0211]

[0212]

[0213] Table 3 Notes *1: Before 200 cycles had passed, the capacity retention rate fell below 60%, so the evaluation was discontinued at that point.

[0214]

[0215] The above results reveal the following: In the lithium ion secondary batteries according to Examples 1 to 9, the average distance D between the peripheries of the adjacent intermediate portions was Ｓ (ave) and D Ｌ(ave) is 30 μm or more and 250 μm or less, and the intermediate area S is 5000 μm ２ 150000 μm or more ２ or less, and an I(110) / I(002) ratio of 0.0040 or more is used. The negative electrodes according to Examples 1 to 9 were manufactured by a manufacturing method including a step (step (3)) of supplying composite particles containing the active material and the second binder onto a current collector of a first intermediate and the plurality of intermediate portions to form a composite particle layer. The lithium ion secondary batteries according to Examples 1 to 9 all had good rapid charge characteristics (charge rates at the first rapid charge cycle) of 37% or more, and good cycle characteristics (capacity retention rates) of 80% or more.

[0216] The negative electrodes used in the lithium ion secondary batteries according to Comparative Examples 1 to 8 do not satisfy at least one of the following conditions (1) to (3): (1) The average distance D between the peripheries of the adjacent intermediate portions is Ｓ (ave) and D Ｌ (2) The area S of the intermediate portion is 5000 μm. ２ 150000 μm or more ２ or less. (3) I(110) / I(002) is 0.0040 or more. Furthermore, the electrodes according to Comparative Examples 6 to 8 are not manufactured by a manufacturing method including the step (3). The lithium ion secondary batteries according to Comparative Examples 1 to 8 are defective because they do not achieve both rapid charging characteristics and cycle characteristics.

[0217] 100: Electrode 110: Current collector 110U: Surface 120: Intermediate portion 130: Composite material layer M1, M2, M3, M4, M5, M6, M7, M8, M9: Intermediate portion L2, L3, L4, L5, L6, L7, L8, L9: Distance

Claims

1. A lithium ion secondary battery electrode comprising a current collector, a plurality of intermediate portions arranged on the current collector in an island shape and including a first binder, and a composite layer arranged on the current collector and the plurality of intermediate portions, wherein, as viewed in the thickness direction of the electrode, the average distance between the peripheries of the plurality of intermediate portions adjacent to each other is 30 μm or more and 250 μm or less, and the area S of each of the plurality of intermediate portions is 5,000 μm or less. ２ More than 150000μm ２ the composite layer contains graphite and a second binder, and the graphite has an X-ray diffraction pattern in which a ratio of a peak intensity corresponding to a (110) plane to a peak intensity corresponding to a (002) plane is 0.0040 or more.

2. The electrode for a lithium ion secondary battery according to claim 1, wherein the mixture layer further contains a silicon atom-containing active material.

3. The electrode for a lithium ion secondary battery according to claim 1, which is a negative electrode.

4. A lithium ion secondary battery comprising the lithium ion secondary battery electrode according to claim 3 and a positive electrode.

5. In a 10-hour discharge, the discharge capacity per unit area of ​​the portion where the negative electrode for the lithium ion secondary battery electrode and the positive electrode face each other is 3.3 mAh / cm ２ The lithium ion secondary battery according to claim 4 .

6. A method for manufacturing an electrode for a lithium ion secondary battery, the electrode comprising: a current collector; a plurality of intermediate portions arranged in an island shape on the current collector and including a first binder; and a composite layer arranged on the current collector and the plurality of intermediate portions and including an active material and a second binder; when viewed in the thickness direction of the electrode, the average distance between the peripheries of the plurality of intermediate portions adjacent to each other is 30 μm or more and 250 μm or less; and the area S of each of the plurality of intermediate portions is 5,000 μm or less. ２ More than 150000μm ２ The manufacturing method of the present invention includes the steps of: (1) applying a binder composition containing the first binder onto the current collector in an island shape to obtain a first intermediate body having the plurality of intermediate portions; (2) supplying composite particles containing the active material and the second binder onto the current collector and the plurality of intermediate portions of the first intermediate body to form a composite particle layer; and (3) applying pressure to the composite particle layer to form the mixture layer and obtain the electrode.

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