KR-20260067221-A - Method for Manufacturing of Free-Standing Film for Anode of Lithium Secondary Battery and Free-Standing Film for Anode of Lithium Secondary Battery Manufactured Thereby

KR20260067221AKR 20260067221 AKR20260067221 AKR 20260067221AKR-20260067221-A

Abstract

A method for manufacturing a self-standing film for a cathode according to one embodiment of the present invention comprises: a step (S1) of mixing and grinding a composition for forming a cathode, comprising a cathode active material, a conductive material, and a binder, to obtain a powder for forming a cathode; and a step (S2) of forming a cathode active material layer through a film-forming process using the powder for forming a cathode, wherein the binder comprises a soft block comprising an aliphatic or alicyclic diene-based monomer unit and exhibiting a rubbery state at room temperature; and a first hard block connected to one end of the soft block and comprising an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy state at room temperature. The composition comprises a ternary block copolymer including a second hard block connected to the other end of the soft block and containing an aromatic ring-containing ethylenically unsaturated monomer unit, which exhibits a glassy phase at room temperature, and the average particle size (D 50 ) of the binder included in the powder for forming the cathode may be smaller than the average particle size (D 50 ) of the binder included in the composition for forming the cathode.

Inventors

이병용
최익현
유효민
장주영

Assignees

현대자동차주식회사
기아 주식회사

Dates

Publication Date: 20260512
Application Date: 20241105

Claims (17)

A step (S1) of obtaining a cathode-forming powder by mixing and grinding a cathode-forming composition comprising a cathode active material, a conductive material, and a binder; and A method for manufacturing a self-supporting film for a cathode, comprising the step (S2) of forming a cathode active material layer through a film forming process using the above-mentioned powder for forming a cathode, The binder comprises a ternary block copolymer comprising: a soft block containing an aliphatic or alicyclic diene monomer unit and exhibiting a rubbery state at room temperature; a first hard block connected to one end of the soft block and containing an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy state at room temperature; and a second hard block connected to the other end of the soft block and containing an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy state at room temperature. A method for manufacturing a self-supporting cathode film, wherein the average particle size (D 50 ) of the binder included in the above-mentioned powder for forming the cathode is smaller than the average particle size (D 50 ) of the binder included in the above-mentioned composition for forming the cathode.
In paragraph 1, A method for manufacturing a self-supporting film for a cathode, wherein the binder included in the above cathode-forming composition is spherical and has an average sphericity of 0.8 or more and 1.0 or less.
In paragraph 1, A method for manufacturing a self-supporting film for a cathode, wherein the binder included in the above cathode-forming composition comprises particles having an average particle size (D 50 ) of 10㎛ or more and 50㎛ or less.
In paragraph 1, The above (S1) step is performed through a grinder, and A method for manufacturing a self-supporting film for a cathode, wherein the grinder has a rotational speed of 15,000 rpm or more and 25,000 rpm or less per minute.
In paragraph 1, A method for manufacturing a self-supporting film for a cathode, wherein the binder included in the above-mentioned powder for forming the cathode comprises particles having an average particle size (D 50 ) of 1 μm or more and 5 μm or less.
In paragraph 1, A method for manufacturing a self-supporting film for a cathode, wherein the above film-making process is performed dry.
In paragraph 6, The above film-forming process includes calendering, and A method for manufacturing a self-supporting film for a cathode, wherein the above calendering is performed at a temperature equal to or higher than the first glass transition temperature and the second glass transition temperature corresponding to the first hard block and the second hard block, respectively.
In paragraph 1, The glass transition temperature of each of the first hard block and the second hard block is 50°C or higher and 120°C or lower, and A method for manufacturing a self-supporting film for a cathode, wherein the glass transition temperature of the soft block is -120℃ or higher and -50℃ or lower.
In paragraph 1, A method for manufacturing a self-supporting film for a cathode, wherein the aliphatic or alicyclic diene monomer for forming the above aliphatic or alicyclic diene monomer unit is one or more selected from the group consisting of butadiene monomers, pentadiene monomers, and hexadiene monomers.
In paragraph 1, A method for manufacturing a self-supporting film for a cathode, wherein the aromatic ring-containing ethylene unsaturated monomer for forming the above-mentioned aromatic ring-containing ethylene unsaturated monomer unit is one or more selected from the group consisting of styrene-based monomers and aromatic (meth)acrylic-based monomers.
It includes a plurality of negative electrode active materials, a plurality of conductive materials and a binder, and The binder comprises a ternary block copolymer comprising: a soft block containing an aliphatic or alicyclic diene monomer unit and exhibiting a rubbery state at room temperature; a first hard block connected to one end of the soft block and containing an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy state at room temperature; and a second hard block connected to the other end of the soft block and containing an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy state at room temperature. The above binder has an intermittent columnar shape connecting one of the plurality of cathode active materials or one of the plurality of conductive materials and another of the plurality of cathode active materials or a conductive material among the plurality of conductive materials, and has an average width perpendicular to the length direction of 50 nm or less, and is a self-supporting film for a cathode.
In Paragraph 11, When an SEM image is obtained by irradiating the above-mentioned cathode self-supporting film with an electron beam of 5.0 kV for more than 1 second, A fusion having an average width of 30 nm or less perpendicular to the longitudinal direction is observed on the surface of the above-mentioned negative electrode active material or the surface of the conductive material, and A self-supporting membrane for a cathode comprising a ternary block copolymer including: a soft block comprising an aliphatic or alicyclic diene monomer unit and exhibiting a rubbery phase at room temperature; a first hard block connected to one end of the soft block and comprising an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy phase at room temperature; and a second hard block connected to the other end of the soft block and comprising an aromatic ring-containing ethylenically unsaturated monomer unit and exhibiting a glassy phase at room temperature.
In Paragraph 11, The glass transition temperature of the first hard block and the second hard block is 50°C or higher and 120°C or lower, and A self-supporting film for a cathode having a glass transition temperature of -120°C or higher and -50°C or lower of the soft block.
In Paragraph 11, A self-supporting film for a cathode, wherein the aliphatic diene monomer for forming the above aliphatic diene monomer unit is one or more selected from the group consisting of butadiene monomers, pentadiene monomers, and hexadiene monomers.
In Paragraph 11, A self-supporting film for a cathode, wherein the aromatic ring-containing ethylenedimethyl unsaturated monomer for forming the above aromatic ring-containing ethylenedimethyl unsaturated monomer unit is one or more selected from the group consisting of styrene-based monomers and aromatic (meth)acrylic-based monomers.
The whole house; and A negative electrode for a lithium secondary battery comprising a self-supporting film for a negative electrode according to any one of claims 11 to 15 disposed on the above-mentioned current collector.
Negative electrode for a lithium secondary battery according to claim 16; Anode for lithium secondary battery; and A lithium secondary battery containing an electrolyte.

Description

Method for Manufacturing of Free-Standing Film for Anode of Lithium Secondary Battery and Free-Standing Film for Anode of Lithium Secondary Battery Manufactured Thereby The present invention relates to a method for manufacturing a self-supporting film for a negative electrode of a lithium secondary battery using a binder comprising a ternary block copolymer comprising a soft block and a hard block, and to a self-supporting film for a negative electrode of a lithium secondary battery manufactured according to the same. Since first commercialized in the 1990s, lithium-ion batteries have been widely applied in the portable electronic device market and continue to receive attention as the most researched energy storage system. Due to the characteristics of lithium-ion batteries, such as high operating voltage, high energy density, low self-discharge rate, high rate performance, and long cycle stability, lithium-ion batteries meet the requirements for being a suitable energy source for electric vehicles. Nevertheless, lithium-ion batteries used in electric vehicles face three major issues: safety, operating time, and cost. While the issues of safety and operating time can be resolved through solid-state batteries, cost remains a hindering factor in the widespread application of lithium-ion batteries; consequently, much research is being conducted to reduce their costs. Reducing energy consumption required for manufacturing or increasing electrode thickness is one of the most effective ways to lower the manufacturing cost of lithium-ion batteries. Conventional electrode manufacturing technology forms electrodes by casting a slurry, prepared by mixing electrode active materials, polymer binders, and conductive additives in water or organic solvents, onto a current collector, and then drying and pressing it. Since the energy required to prepare the slurry and coat it onto the current collector accounts for approximately 50% of the total energy consumed in the manufacturing process, research has been conducted on solvent-free dry electrode manufacturing processes to reduce the manufacturing cost of lithium-ion batteries. A representative example is a technology for manufacturing the cathode of a lithium-ion battery dry using polytetrafluoroethylene (PTFE). However, because PTFE has a low LUMO (lowest unoccupied molecular orbitals) level and can easily accept electrons, it is electrochemically unstable in negative potential environments; consequently, lithium-ion batteries manufactured using PTFE as a binder exhibited poor cycle stability. In addition, when manufacturing the cathode using PTFE, there was also a problem where the initial efficiency of the lithium secondary battery decreased due to the decomposition of the PTFE binder during initial charging. Despite extensive research on dry electrode manufacturing technology, the development of dry cathode manufacturing technology for producing cathodes with good mechanical properties such as formability, electrochemical stability, and tensile strength remains insufficient, making further research and development necessary. FIG. 1 is a schematic diagram showing the internal structure of a binder included in a self-supporting film for a cathode according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing a method for manufacturing a self-supporting film for a cathode according to one embodiment of the present invention. FIG. 3 is a schematic diagram showing the change mechanism of the binder during the manufacturing process of a self-supporting film for a cathode according to one embodiment of the present invention. FIG. 4 is a schematic diagram showing the structure formed by the binder and the cathode active material in a self-supporting film for a cathode according to one embodiment of the present invention. Figure 5 is a schematic diagram showing the structure formed by the binder and the cathode active material in a conventional self-supporting film for a cathode using PTFE as a binder. Figure 6 is a diagram showing an SEM image of a powder for forming a cathode according to Example 1. Figures 7 and 8 are SEM images of a self-supporting film for a cathode according to Example 1. Figure 9 is a diagram showing an SEM image of a self-supporting film for a cathode according to Comparative Example 1. Figure 10 is a diagram showing an SEM image of a self-supporting film for a cathode according to Comparative Example 2. FIG. 11 is a graph showing the tensile strength of different self-supporting cathode films in Example 1, Comparative Examples 1 and 2. Hereinafter, the present invention will be described in more detail to aid in understanding the invention. In this case, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that