Resin current collector for lithium-ion batteries and lithium-ion batteries

Abstract

To provide a resin current collector for a lithium ion battery which has high energy density and can suppress an increase in the internal resistance value of a battery caused by gas generated accompanying charge and discharge of a lithium ion battery.SOLUTION: A resin current collector for a lithium ion battery is composed of a resin composition containing a polyolefin resin, a conductive filler and gas adsorption particles, wherein a weight ratio of the gas adsorption particles is 5-20 wt.% based on the weight of the resin current collector for the lithium ion battery, and the gas adsorption particles are one or more selected from the group consisting of activated carbon, zeolite, silica and alumina.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a resin current collector for lithium-ion batteries and a lithium-ion battery. [Background technology]

[0002] As lithium-ion batteries undergo repeated charging and discharging cycles, side reactions occur between the electrolyte and the electrode active material, generating gas inside the battery. This gas can cause the battery to swell, leading to increased internal resistance and other degradation problems.

[0003] To solve this problem, various approaches have been considered, such as providing a space for gas venting inside the battery, installing a separate gas adsorption layer, or adding a gas adsorbent to the electrode active material layer, as described in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-227818 [Patent Document 2] Japanese Patent Publication No. 2020-149794 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in lithium-ion batteries, which require high capacity and high energy density, there was a problem in that adding a gas adsorbent to the electrode active material layer reduced the energy density.

[0006] The present invention has been made to solve the above problems, and aims to provide a resin current collector for lithium-ion batteries that has a high energy density and can suppress the increase in the internal resistance of the battery caused by gas generated during charging and discharging of the lithium-ion battery. [Means for solving the problem]

[0007] The inventors of this invention arrived at this present invention as a result of diligent research to solve these problems. In other words, the present invention relates to a resin current collector for a lithium-ion battery comprising a resin composition containing a polyolefin resin, a conductive filler, and gas-adsorbing particles, wherein the weight percentage of the gas-adsorbing particles is 5 to 20% by weight based on the weight of the resin current collector for the lithium-ion battery, and the gas-adsorbing particles are one or more selected from the group consisting of activated carbon, zeolite, silica, and alumina, and to a lithium-ion battery equipped with the resin current collector for the lithium-ion battery of the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin current collector for lithium-ion batteries that has a high energy density and can suppress the increase in the internal resistance of the battery caused by gas generated during the charging and discharging of the lithium-ion battery. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. This invention relates to a resin current collector for lithium-ion batteries and a lithium-ion battery. In this specification, the term "lithium-ion battery" includes lithium-ion rechargeable batteries.

[0010] The present invention relates to a resin current collector for lithium-ion batteries, comprising a resin composition containing a polyolefin resin, a conductive filler, and gas-adsorbing particles, wherein the weight percentage of the gas-adsorbing particles is 5 to 20% by weight based on the weight of the lithium-ion battery resin current collector, and the gas-adsorbing particles are one or more selected from the group consisting of activated carbon, zeolite, silica, and alumina.

[0011] In the resin current collector for lithium-ion batteries of the present invention, the above-mentioned type of gas adsorption particles are added to the current collector in the above-mentioned proportion. Therefore, in a lithium-ion battery made using the resin current collector for lithium-ion batteries of the present invention, the gas generated during charging and discharging of the lithium-ion battery can be adsorbed by the gas adsorption particles contained in the current collector. Therefore, it is possible to suppress the increase in the internal resistance of lithium-ion batteries caused by gas.

[0012] Furthermore, since the resin current collector for lithium-ion batteries of the present invention contains gas adsorption particles, sufficient gas can be adsorbed without adding gas adsorption particles to the electrode active material layer when manufacturing the lithium-ion battery. In other words, by using the resin current collector for lithium-ion batteries of the present invention, the need to add gas adsorption particles to the electrode active material layer is reduced. If the electrode active material layer does not contain gas adsorbed particles, the density of the active material in the electrode active material layer can be increased, thereby improving the energy density.

[0013] The resin current collector for lithium-ion batteries of the present invention preferably has a film thickness of 25 to 500 μm, and more preferably 30 to 60 μm. If the film thickness of the resin current collector for lithium-ion batteries is too thin, the resin current collector for lithium-ion batteries becomes more susceptible to damage. If the film thickness of the resin current collector for lithium-ion batteries is too thick, the proportion of the resin current collector will increase and the proportion of the electrode active material layer will decrease when manufacturing lithium-ion batteries using the resin current collector, resulting in a decrease in energy density. Therefore, it is preferable for the film thickness of the current collector for lithium-ion batteries to be as thin as possible, and a film thickness of 60 μm or less is even more preferable from the viewpoint of increasing energy density.

[0014] The resin current collector for lithium-ion batteries of the present invention can be used as both a positive electrode current collector and a negative electrode current collector.

[0015] Hereinafter, each component of the resin current collector for a lithium-ion battery of the present invention will be described in detail.

[0016] (Polyolefin resin) In the resin current collector for a lithium-ion battery of the present invention, the polyolefin resin is a resin (matrix resin) that constitutes the base of the resin current collector for a lithium-ion battery. Examples of the polyolefin resin include polyolefins [such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polycycloolefin (PCO), etc.]. More preferably, polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP) are included. In addition, the polyolefin resin in the present invention may be a modified product (hereinafter referred to as modified polyolefin) or a mixture of the above polyolefin resins.

[0017] Examples of the polyolefin resin that can be obtained from the market include the following. PE: "Novatech LL UE320" and "Novatech LL UJ960", both manufactured by Japan Polyethylene Corporation PP: "Sun Allomer PM854X", "Sun Allomer PC684S", "Sun Allomer PL500A", "Sun Allomer PC630S", "Sun Allomer PC630A", "Sun Allomer PB522M", "Quoaria CM688A", all manufactured by Sun Allomer Co., Ltd., "Prime Polymer J-2000GP", manufactured by Prime Polymer Co., Ltd., "Wintech WFX4T", manufactured by Nippon Polypro Co., Ltd. PMP: "TPX", manufactured by Mitsui Chemicals, Inc.

[0018] Examples of the modified polyolefin include those obtained by introducing polar functional groups into polyethylene, polypropylene, or their copolymers. Examples of the polar functional groups include carboxyl group, 1,3-dioxo-2-oxapropylene group, hydroxyl group, amino group, amide group, and imide group, etc.

[0019] Examples of modified polyolefins, which are polyethylene, polypropylene, or copolymers thereof, into which polar functional groups have been introduced, include the Admer series manufactured by Mitsui Chemicals, Inc., which are commercially available.

[0020] Furthermore, the matrix resin of the lithium-ion battery resin current collector of the present invention may contain resins other than polyolefin resin, such as polyamide (PA, e.g., nylon 6, nylon 6,6, etc.), polymethylpentene (PMP), polyethylene terephthalate (PET), polyethernitrile (PEN), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, and silicone resin.

[0021] The matrix resin is preferably one with a melting point of 150 to 230°C, and more preferably one with a melting point of 155 to 225°C.

[0022] In the lithium-ion battery resin current collector of the present invention, the weight percentage of the matrix resin is preferably 50 to 90% by weight, and more preferably 50 to 70% by weight, based on the weight of the lithium-ion battery resin current collector. If the weight percentage of the matrix resin is less than 50% by weight, the strength of the resin current collector for lithium-ion batteries may be weakened. When the weight percentage of the matrix resin exceeds 90% by weight, the relative weight percentage of the conductive filler decreases, which tends to reduce the conductivity of the resin current collector for lithium-ion batteries.

[0023] (Conductive filler) In the resin current collector for lithium-ion batteries of the present invention, the conductive filler is not particularly limited as long as it is a conductive material, but it is preferably at least one selected from the materials shown below. Specifically, examples include, but are not limited to, metals [nickel, aluminum, stainless steel (SUS), silver, copper, and titanium, etc.], carbon [graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal lamp black, etc.)], and mixtures thereof. These conductive fillers may be used individually or in combination of two or more. Alloys or metal oxides of these fillers may also be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium, and mixtures thereof are preferred, more preferably silver, aluminum, stainless steel, and carbon, and even more preferably carbon. These conductive fillers may also be made by coating a particulate ceramic material or resin material with a conductive material (a metallic material from among the conductive filler materials mentioned above) by plating or the like.

[0024] In the resin current collector for lithium-ion batteries of the present invention, the weight percentage of the conductive filler is preferably 10 to 40% by weight, and more preferably 15 to 20% by weight, based on the weight of the resin current collector for lithium-ion batteries. If the weight ratio of conductive filler is too low, the conductivity of the resin current collector for lithium-ion batteries tends to decrease. If the weight proportion of conductive filler is too high, the relative weight proportion of the matrix resin decreases, and the strength of the matrix resin's weight proportion weakens.

[0025] In the resin current collector for lithium-ion batteries of the present invention, the volume-average particle size of the conductive filler is preferably 1 to 15 μm, more preferably 3 to 10 μm, and even more preferably 5 to 8 μm. When the volume-average particle size of the conductive filler is within the above range, the conductivity of the resin current collector for lithium-ion batteries of the present invention becomes good.

[0026] In this specification, the volume-average particle diameter of particles (such as conductive fillers and gas-adsorbed particles described later) refers to the particle size at 50% of the integrated value in the particle size distribution determined by the microtrac method (laser diffraction / scattering method) (Dv50). The microtrac method is a method for determining the particle size distribution using scattered light obtained by irradiating particles with laser light. For measuring the volume-average particle diameter of particles, a microtrac manufactured by Nikkiso Co., Ltd. or similar can be used.

[0027] (Gas-adsorbed particles) In the resin current collector for lithium-ion batteries of the present invention, the gas adsorption particles are one or more selected from the group consisting of activated carbon, zeolite, silica, and alumina. Furthermore, the gas adsorption particles are porous. Gas adsorption particles made of these materials can effectively adsorb gases generated during the charging and discharging of lithium-ion batteries.

[0028] In the lithium-ion battery resin current collector of the present invention, the weight percentage of gas adsorbed particles is 5 to 20% by weight based on the weight of the lithium-ion battery resin current collector. This weight percentage is preferably 10 to 20% by weight, and more preferably 10 to 15% by weight. If the weight percentage of gas adsorbed particles is less than 5% by weight, it becomes difficult to adequately adsorb the gas generated during charging and discharging of the lithium-ion battery, which tends to increase the internal resistance of the lithium-ion battery. If the weight percentage of gas-adsorbed particles exceeds 20% by weight, the relative weight percentage of the matrix resin decreases, which can weaken the strength of the matrix resin.

[0029] In the resin current collector for lithium-ion batteries of the present invention, the volume-average particle diameter of the gas adsorbed particles is preferably 0.04 to 20 μm, and more preferably 0.04 to 8 μm. Gas adsorbed particles with a volume-average particle diameter of less than 0.04 μm are difficult to manufacture. When the volume-average particle size of gas adsorbed particles exceeds 20 μm, the matrix resin becomes less able to adhere the gas adsorbed particles to each other. As a result, the strength of the resin current collector for lithium-ion batteries tends to decrease.

[0030] In the resin current collector for lithium-ion batteries of the present invention, the specific surface area of ​​the gas adsorbed particles is 100 to 2000 m². 2 It is preferable that the amount be / g, and the amount is 300-900m 2 It is more preferable that it be / g. When the specific surface area of ​​the gas adsorbing particles is within the above range, gases generated during the charging and discharging of lithium-ion batteries can be effectively adsorbed. In this specification, the specific surface area of ​​gas-adsorbed particles is the value measured as BET specific surface area in accordance with "JIS Z8830 Method for Measuring Specific Surface Area of ​​Powders (Solids) by Gas Adsorption".

[0031] The lithium-ion battery resin current collector of the present invention may contain other components (dispersants, crosslinking accelerators, crosslinking agents, colorants, ultraviolet absorbers, plasticizers, etc.) in addition to polyolefin resin, conductive fillers, and gas adsorbing particles.

[0032] The method for manufacturing the resin current collector for lithium-ion batteries of the present invention is not particularly limited, but can be manufactured by, for example, the following method. A resin composition is obtained by mixing polyolefin resin, conductive filler, gas adsorbent particles, and other components as needed. Methods of mixing include obtaining a masterbatch of conductive filler and gas-adsorbing particles and then mixing it with the matrix resin, and mixing all raw materials together. The mixing can be carried out by mixing pelletized or powdered components using a suitable known mixer, such as a kneader, internal mixer, Banbury mixer, and rolls.

[0033] There are no particular restrictions on the order in which the components are added during mixing. The resulting mixture may be further pelletized or powdered using a pelletizer or the like.

[0034] A resin current collector for lithium-ion batteries can be obtained by molding the resulting resin composition into a film, for example. Known film molding methods include the T-die method, inflation method, and calendering method. However, resin current collectors for lithium-ion batteries can also be obtained by molding methods other than film molding.

[0035] [Lithium-ion battery] The lithium-ion battery of the present invention comprises a resin current collector for lithium-ion batteries of the present invention.

[0036] The resin current collector for lithium-ion batteries of the present invention can be applied to known lithium-ion batteries. In other words, known materials can be used as the positive electrode active material, negative electrode active material, electrolyte, separator, etc. Furthermore, the positive electrode active material may be a coated positive electrode active material in which the positive electrode active material is coated with a resin such as an acrylic resin, and the negative electrode active material may be a coated negative electrode active material in which the negative electrode active material is coated with a resin such as an acrylic resin.

[0037] In the lithium-ion battery of the present invention, it is sufficient to use the resin current collector for lithium-ion batteries of the present invention in at least one of the positive electrode current collector or the negative electrode current collector. Alternatively, both the positive electrode current collector and the negative electrode current collector may be the resin current collector for lithium-ion batteries of the present invention.

[0038] When the resin current collector for lithium-ion batteries of the present invention is used as either a current collector for the positive electrode or a current collector for the negative electrode, the other current collector may be a metal current collector or a resin current collector other than the resin current collector for lithium-ion batteries of the present invention. When using a metal current collector, the material of the current collector may be a metallic material such as copper, aluminum, titanium, stainless steel, nickel, or alloys thereof. [Examples]

[0039] The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples unless it deviates from the spirit of the invention. Unless otherwise specified, "parts" refers to parts by weight.

[0040] (Example 1) [Preparation of electrolyte solution] An electrolyte was prepared by dissolving LiFSI at a ratio of 2.0 mol / L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1:1).

[0041] [Fabrication of resin current collector for positive electrode] Using a twin-screw extruder, 65 parts of polypropylene [product name "Sun Allomer PL500A", manufactured by Sun Allomer Co., Ltd.] as a polyolefin resin, 20 parts of carbon black [product name: SuperP, manufactured by Timcal] as a conductive filler, 10 parts of zeolite 1 [product name "Zeoal 4A": average particle size 0.045 μm, manufactured by Nakamura Superhard Co., Ltd.] as gas adsorption particles, and 5 parts of dispersant [product name "Yumex 1001", manufactured by Sanyo Chemical Industries, Ltd.] were melt-kneaded at 200°C and 200 rpm to obtain a resin mixture. The obtained resin mixture was passed through a T-die extrusion film molding machine and stretched and rolled to obtain a conductive film for resin current collectors with a thickness of 30 μm. Next, the obtained conductive film for resin current collectors was cut to 17.0 cm × 17.0 cm, nickel deposition was applied to one side, and then terminals for current extraction (5 mm × 3 cm) were connected to obtain a resin current collector for positive electrode according to Example 1.

[0042] [Fabrication of coated cathode active material particles] 150 parts of DMF (N,N-dimethylformamide) were placed in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, and the temperature was raised to 75°C. Next, a monomer composition containing 91 parts acrylic acid, 9 parts methyl methacrylate, and 50 parts DMF, along with an initiator solution containing 0.3 parts 2,2'-azobis(2,4-dimethylvaleronitrile) and 0.8 parts 2,2'-azobis(2-methylbutyronitrile) dissolved in 30 parts DMF, were continuously added dropwise over 2 hours using a dropping funnel while blowing nitrogen into the four-necked flask under stirring to carry out radical polymerization. After the dropwise addition was complete, the reaction was continued at 75°C for 3 hours. Next, the temperature was raised to 80°C and the reaction was continued for 3 hours to obtain a copolymer solution with a resin concentration of 30%. The obtained copolymer solution was transferred to a Teflon® vat and dried under reduced pressure at 150°C and 0.01 MPa for 3 hours, and the DMF was removed by distillation to obtain the copolymer. This copolymer was coarsely ground with a hammer, and then further ground in a mortar to obtain a powdered polymer compound for coating. Next, one part of the coating polymer compound was dissolved in three parts of DMF to obtain a coating polymer compound solution. Cathode active material particles (LiNi 0.8 Co 0.15 Al 0.05 84 parts of O2 powder (volume average particle size 4 μm) were placed in a universal mixer high-speed mixer FS25 [(manufactured by Earth Technica Co., Ltd.)], and while stirring at room temperature and 720 rpm, 9 parts of the coating polymer compound solution were added dropwise over 2 minutes, and the mixture was stirred for a further 5 minutes. Next, while stirred, 3 parts of acetylene black [Denka Black®, manufactured by Denka Co., Ltd.], which is a conductive additive, and glass ceramic particles (product name "Lithium Ion Conductive Glass Ceramics LICGC") are added. TM PW-01 (1μm) [manufactured by Ohara Co., Ltd.] was added in four portions over a period of 2 minutes, and stirring was continued for 30 minutes. Subsequently, the pressure was reduced to 0.01 MPa while maintaining stirring, and then the temperature was raised to 140°C while maintaining stirring and reduced pressure. The stirring, reduced pressure, and temperature were maintained for 8 hours to remove volatile components by distillation. The obtained powder was classified using a sieve with a mesh size of 200 μm to obtain coated positive electrode active material particles according to Example 1.

[0043] [Fabrication of positive electrodes for lithium-ion batteries] 42 parts of electrolyte and 4.2 parts of carbon fiber [Donacarbo Milled S-243, manufactured by Osaka Gas Chemical Co., Ltd.: average fiber length 500 μm, average fiber diameter 13 μm: electrical conductivity 200 mS / cm] were mixed at 2000 rpm for 5 minutes using a planetary stirring type mixing and kneading device {Awatori Rentaro [manufactured by Shinky Co., Ltd.]}. Subsequently, 30 parts of the electrolyte and 206 parts of the coated positive electrode active material particles were added, and the mixture was further mixed at 2000 rpm for 2 minutes using the planetary stirring type mixing and kneading device. After adding another 20 parts of the electrolyte, the mixture was stirred at 2000 rpm for 1 minute using the planetary stirring type mixing and kneading device, and then 2.3 parts of the electrolyte was further added, and the mixture was stirred at 2000 rpm for 2 minutes using the planetary stirring type mixing and kneading device to prepare a slurry for the positive electrode active material layer. The obtained slurry for the positive electrode active material layer had a basis weight of 80 mg / cm³. 2 To achieve this, the resin current collector for the positive electrode was coated on one side, and pressed at a pressure of 1.4 MPa for approximately 10 seconds to produce a lithium-ion battery positive electrode (16.2 cm × 16.2 cm) according to Example 1 with a thickness of 340 μm.

[0044] [Fabrication of resin current collector for negative electrode] A resin mixture was obtained by melt-kneading 70 parts of polypropylene [product name "Sun Allomer PL500A", manufactured by Sun Allomer Co., Ltd.], 25 parts of carbon black [product name: SuperP, manufactured by Timcal], and 5 parts of dispersant [product name "Yumex 1001", manufactured by Sanyo Chemical Industries, Ltd.] in a twin-screw extruder at 200°C and 200 rpm. The obtained resin mixture was passed through a T-die extrusion film molding machine and stretched and rolled to obtain a conductive film for resin current collectors with a thickness of 100 μm. Next, the obtained conductive film for resin current collectors was cut to 17.0 cm × 17.0 cm, nickel deposition was applied to one side, and then terminals for current extraction (5 mm × 3 cm) were connected to obtain a negative electrode resin current collector according to Example 1.

[0045] [Fabrication of coated negative electrode active material particles] One part of the coating polymer compound was dissolved in three parts of DMF to obtain a coating polymer compound solution. 76 parts of negative electrode active material particles (hard carbon powder, volume average particle diameter 25 μm) were placed in a high-speed mixer FS25 [manufactured by Earth Technica Co., Ltd.], and while stirring at room temperature and 720 rpm, 9 parts of the polymer compound solution for coating were dropped over 2 minutes, and stirring was continued for another 5 minutes. Next, while stirring, 9 parts of acetylene black [Denka Black (registered trademark), manufactured by Denka Co., Ltd.], which is a conductive assistant, 2 parts of carbon nanofibers [manufactured by Teijin Limited], and glass ceramic particles (product name: "Lithium ion conductive glass ceramics LICGC TM PW-01 (1 μm)」 [manufactured by Ohara Corporation], (1 μm)) 4 parts were added in portions over 2 minutes while dividing, and stirring was continued for 30 minutes. Thereafter, while maintaining stirring, the pressure was reduced to 0.01 MPa, then while maintaining stirring and the degree of reduced pressure, the temperature was raised to 140 °C, and stirring, the degree of reduced pressure, and the temperature were maintained for 8 hours to distill off volatile components. The obtained powder was classified using a sieve with a mesh opening of 200 μm to obtain coated negative electrode active material particles according to Example 1.

[0046] [Fabrication of negative electrode for lithium ion battery] 42 parts of electrolyte solution and 4.2 parts of carbon fiber [Donacarb Mild S-243: average fiber length 500 μm, average fiber diameter 13 μm: electric conductivity 200 mS / cm, manufactured by Osaka Gas Chemical Co., Ltd.] were mixed at 2000 rpm for 5 minutes using a planetary stirring type mixing and kneading device {Awatori Renk太郎 [manufactured by Shinchi Co., Ltd.]}, and subsequently, after adding 30 parts of the above electrolyte solution and 206 parts of the above coated negative electrode active material particles, they were further mixed at 2000 rpm for 2 minutes using a planetary stirring type mixing and kneading device. After further adding 20 parts of the above electrolyte solution, stirring was performed at 2000 rpm for 1 minute using a planetary stirring type mixing and kneading device. After further adding 2.3 parts of the above electrolyte solution, stirring was mixed at 2000 rpm for 2 minutes using a planetary stirring type mixing and kneading device to prepare a slurry for negative electrode active material layer. The obtained slurry for negative electrode active material layer was applied to one side of the resin current collector for negative electrode so that the basis weight was 80 mg / cm 2 and pressed at a pressure of 1.4 MPa for about 10 seconds to fabricate a negative electrode for lithium ion battery (16.2 cm × 16.2 cm) according to Example 1 with a thickness of 340 μm.

[0047] [Manufacturing of lithium-ion batteries] The obtained positive electrode and negative electrode for lithium-ion batteries were combined via a separator (Cellguard #3501) to create a laminate cell, thereby producing the lithium-ion battery according to Example 1.

[0048] (Examples 2) to (Examples 18) and (Comparative Example 1) to (Comparative Example 3) Except for changing the type and proportion of polyolefin resin, conductive filler, and gas adsorbent particles used in the above [Preparation of Resin Current Collector for Positive Electrode], and the film thickness of the resin current collector for positive electrode, as shown in Table 1, the resin current collectors for positive electrode according to Examples 2 to 18 and Comparative Examples 1 to 3 were prepared in the same manner as in Example 1. A lithium-ion battery was fabricated using the resin current collector for the positive electrode. In Comparative Example 3, it was not possible to form a film on the resin current collector for the positive electrode. This is thought to be because the gas-adsorbing particle content was too high, resulting in a low content of the polyolefin resin, which is the matrix resin, making it impossible to adhere the gas-adsorbing particles, conductive fillers, etc.

[0049] (Example 19) A lithium-ion battery according to Example 19 was manufactured in the same manner as in Example 1, except that the following resin current collectors were used for the positive electrode and the negative electrode.

[0050] [Fabrication of resin current collector for positive electrode] A resin mixture was obtained by melt-kneading 70 parts of polypropylene [product name "Sun Allomer PL500A", manufactured by Sun Allomer Co., Ltd.], carbon black [product name: SuperP, manufactured by Timcal], and dispersant [product name "Yumex 1001", manufactured by Sanyo Chemical Industries, Ltd.] in a twin-screw extruder at 200°C and 200 rpm. The obtained resin mixture was passed through a T-die extrusion film molding machine and stretched and rolled to obtain a conductive film for resin current collectors with a thickness of 100 μm. Next, the obtained conductive film for resin current collectors was cut to 17.0 cm × 17.0 cm, nickel deposition was applied to one side, and then terminals for current extraction (5 mm × 3 cm) were connected to obtain a resin current collector for positive electrode according to Example 19.

[0051] [Fabrication of resin current collector for negative electrode] A resin mixture was obtained by melt-kneading 65 parts of polypropylene [product name "Sun Allomer PL500A", manufactured by Sun Allomer Co., Ltd.] as a polyolefin resin, 20 parts of carbon black [product name: SuperP, manufactured by Timcal] as a conductive filler, 10 parts of zeolite 2 [product name "Molecular Sieve 5A Powder": average particle size 8 μm, manufactured by Tomoe Engineering Co., Ltd.] as gas adsorption particles, and 5 parts of dispersant [product name "Yumex 1001", manufactured by Sanyo Chemical Industries, Ltd.] at 200°C and 200 rpm using a twin-screw extruder. The obtained resin mixture was passed through a T-die extrusion film molding machine and stretched and rolled to obtain a conductive film for resin current collectors with a thickness of 50 μm. Next, the obtained conductive film for resin current collectors was cut to 17.0 cm × 17.0 cm, nickel deposition was applied to one side, and then terminals for current extraction (5 mm × 3 cm) were connected to obtain a negative electrode resin current collector according to Example 19.

[0052] [Table 1]

[0053] The types of gas-adsorbed particles in Table 1 are as follows: Zeolite 1: Product name "Zeoal 4A", average particle size: 0.045 μm, Manufacturer: Nakamura Choko Co., Ltd. Zeolite 2: Product name "Molecular Sieve 5A Powder", average particle size: 8 μm, Manufacturer: Tomoe Engineering Co., Ltd. Zeolite 3: Product name "Molecular Sieve 5A Pellet", Average particle size: 20 μm, Manufacturer: Tomoe Engineering Co., Ltd. Zeolite 4: Product name "Molecular Sieve 13X Powder", average particle size: 8 μm, Manufacturer: Tomoe Engineering Co., Ltd. Zeolite 5: Product name "Molecular Sieve 5A Pellet", Average particle size: 40 μm, Manufacturer: Tomoe Engineering Co., Ltd. Silica 1: Product name "Silica Powder", average particle size: 9 μm, manufacturer: Maruto Co., Ltd. Silica 2: Product name "Silica gel", average particle size: 19 μm, manufacturer: Maruto Co., Ltd. Silica 3: Product name "Silica Powder", Average particle size: 38 μm, Manufacturer: Maruto Co., Ltd. Activated carbon: Product name "Powdered Activated Carbon KD-PWSSP", Average particle size: 4μm, Manufacturer: UES Co., Ltd. Alumina: Product name "Activated Alumina AA-101", Average particle size: 12 μm, Manufacturer: Nippon Light Metal Co., Ltd. Furthermore, "Zeolite 3," "Zeolite 5," "Silica 1," and "Silica 3" were crushed in a mortar and pestle, and the average particle size was adjusted using a sieve.

[0054] <Observation of film-forming properties of resin current collectors> The film-forming properties of the positive electrode resin current collectors in Examples 1-18 and Comparative Examples 1-3, and the negative electrode resin current collector in Example 19 were visually inspected. The evaluation criteria were as follows. The results are shown in Table 1. ○: Can form a film, with a film thickness of 30 μm or more and less than 70 μm. △: Can form a film, with a film thickness of 70 μm or more. ×: Film deposition failed.

[0055] <Measurement of internal resistance> The lithium-ion batteries obtained in each example and comparative example were charged to a voltage of 4.2V at 25°C using a charge / discharge measurement device "Battery Analyzer Model 1470" [manufactured by Toyo Technica Co., Ltd.] with a constant current of 0.05C, and then charged again at a constant voltage of 4.2V until the current value was 0.01C. After a 10-minute rest, the batteries were discharged to a voltage of 2.5V with a constant current of 0.01C, and then charged to a voltage of 4.2V with a constant current of 0.05C. The charged lithium-ion batteries were then stored in a 60°C environment. An impedance measuring device (HIOKI E.E. CORPORATION, Chemical Impedance Analyzer IM3590) was used to measure the internal resistance at a frequency of 1000 Hz after 0 days (immediately after full charge), after 7 days of storage, and after 14 days of storage. The results are shown in Table 1. The "rate of change" shown in Table 1 represents the percentage increase in the internal resistance value after 14 days compared to after 0 days.

[0056] As shown in Table 1, it was found that the internal resistance (Ω) of the lithium-ion batteries in each embodiment did not increase easily. This is thought to be because the positive electrode resin current collector or negative electrode resin current collector in each embodiment contains gas adsorption particles, which can adsorb gas generated during the charging and discharging of the lithium-ion battery, thereby preventing the battery from bulging due to gas. [Industrial applicability]

[0057] The resin current collector for lithium-ion batteries of the present invention is particularly useful as a resin current collector for lithium-ion batteries used in mobile phones, personal computers, hybrid vehicles, and electric vehicles.

Claims

1. A resin current collector for lithium-ion batteries, comprising a resin composition containing a polyolefin resin, a conductive filler, and gas-adsorbing particles, The weight percentage of the gas adsorbed particles is 5 to 20% by weight, based on the weight of the resin current collector for the lithium-ion battery. A resin current collector for lithium-ion batteries, characterized in that the gas adsorption particles are one or more selected from the group consisting of activated carbon, zeolite, silica, and alumina.

2. The resin current collector for a lithium-ion battery according to claim 1, wherein the volume-average particle diameter of the gas adsorbed particles is 0.04 to 20 μm.

3. The resin current collector for lithium-ion batteries according to claim 1 or 2, wherein the weight percentage of the conductive filler is 15 to 20% by weight based on the weight of the resin current collector for lithium-ion batteries.

4. The resin current collector for lithium-ion batteries according to any one of claims 1 to 3, wherein the film thickness of the resin current collector for lithium-ion batteries is 30 to 60 μm.

5. A lithium-ion battery comprising a resin current collector for a lithium-ion battery as described in any one of claims 1 to 4.

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