Method for manufacturing self-supporting film for negative electrode of lithium secondary battery and self-supporting film for negative electrode of lithium secondary battery manufactured by method

Abstract

The present disclosure relates to a method for manufacturing a self-supporting film for a negative electrode, comprising the steps of: obtaining a negative electrode-forming powder by mixing and grinding a negative electrode-forming composition comprising a negative electrode active material, a conductive material, and a binder (S1); and forming a negative electrode active material layer by a film formation process using the negative electrode forming powder (S2). The adhesive includes a triblock copolymer including: a soft block including aliphatic or cycloaliphatic diene monomer units and exhibiting a rubber phase at room temperature; a first hard block connected to one end of the soft block, including an aromatic ring-containing ethylenically unsaturated monomer unit, and presenting a glass phase at room temperature; and a second hard block connected to the other end of the soft block, including an aromatic ring-containing ethylenically unsaturated monomer unit, and exhibiting a glass phase at room temperature, and the average particle diameter (D50) of the binder contained in the negative electrode-forming powder is smaller than the average particle diameter (D50) of the binder contained in the negative electrode-forming composition.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0155653, filed with the Korean Intellectual Property Office on November 5, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a method for manufacturing a self-supporting film for a lithium secondary battery anode by employing a triblock copolymer including soft and hard blocks, and the self-supporting film for a lithium secondary battery anode manufactured by this method. background

[0004] Since the first commercialization of lithium-ion batteries in the 1990s, they have been widely used and continue to receive attention as the most studied energy storage system. Due to their higher drive voltage, higher energy density, lower self-discharge rate, higher rate performance, and longer cycle stability, lithium-ion batteries are suitable as an energy source for electric vehicles.

[0005] However, lithium-ion batteries used in electric vehicles face three main challenges: stability, operating time, and cost. While stability and operating time can be addressed with all-solid-state batteries, cost remains a significant obstacle to their widespread adoption. Therefore, much research and exploration has focused on reducing the cost of lithium-ion batteries.

[0006] Reducing energy consumption or increasing electrode thickness are among the most effective methods to lower the manufacturing cost of lithium-ion batteries. Traditional electrode manufacturing techniques involve casting a slurry made by mixing electrode active materials, polymer binders, and conductive additives with water or organic solvents onto a current collector, drying the resulting product, and pressing it to form the electrode. In this case, the energy required to prepare the slurry and coat the current collector accounts for 50% of the total energy consumption in the entire manufacturing process. Therefore, research and exploration have been conducted on solvent-free dry electrode manufacturing processes to reduce the manufacturing cost of lithium-ion batteries. Representatively, as a dry electrode manufacturing process, there is a technique for dry manufacturing of lithium-ion battery cathodes using polytetrafluoroethylene (PTFE). PTFE can possess the lowest unoccupied molecular orbital (LUMO) energy level, thus readily accepting electrons. Therefore, PTFE is electrochemically unstable under negative potential conditions. Consequently, lithium-ion battery anodes manufactured using PTFE as a binder exhibit poor cycle stability. Furthermore, when using PTFE to manufacture anodes, the PTFE binder decomposes during the initial charging process, leading to a decrease in the initial efficiency of the lithium-ion battery.

[0007] Despite extensive research and exploration into dry electrode manufacturing techniques, the development of dry anode manufacturing technologies that produce anodes with superior physical properties in terms of formability, electrochemical stability, or tensile strength remains insufficient. Therefore, further research and development of this technology are necessary. Summary of the Invention

[0008] This disclosure aims to address the aforementioned problems in the prior art while fully preserving the advantages achieved by the prior art.

[0009] One aspect of this disclosure provides a self-supporting film for a lithium secondary battery, which is easy to form, remains stable even under negative potential, and is firmly bonded to a negative electrode active material by applying an adhesive comprising a triblock copolymer, the triblock copolymer comprising hard blocks that contribute to achieving excellent mechanical properties and soft blocks that are flexible, exhibiting excellent tensile strength and forming a three-dimensional network to firmly bond with the negative electrode active material and conductive material. This disclosure also provides a method for manufacturing the self-supporting film, a lithium secondary battery negative electrode comprising the negative electrode self-supporting film, and a lithium secondary battery.

[0010] The technical problems to be solved by this disclosure are not limited to those described above. Any other technical problems not mentioned herein will be clearly understood by those skilled in the art from the following description.

[0011] According to one aspect of this disclosure, a method for manufacturing a self-supporting negative electrode film is provided, comprising the following steps: mixing and grinding a negative electrode forming composition comprising a negative electrode active material, a conductive material, and a binder to obtain a negative electrode forming powder (S1); and forming a negative electrode active material layer using the negative electrode forming powder through a film-forming process (S2). The binder comprises a triblock copolymer, including a soft block, a first hard block, and a second hard block, wherein the soft block comprises aliphatic or alicyclic diene monomer units and exhibits a rubber phase at room temperature; the first hard block is connected to one end of the soft block, comprises an olefinically unsaturated monomer unit containing an aromatic ring, and exhibits a glass phase at room temperature; the second hard block is connected to the other end of the soft block, comprises an olefinically unsaturated monomer unit containing an aromatic ring, and exhibits a glass phase at room temperature, and the average particle size (D) of the binder contained in the negative electrode forming powder is... 50 The particle size is smaller than the average particle size (D) of the binder contained in the negative electrode forming composition. 50 ).

[0012] According to one aspect of this disclosure, the negative electrode self-supporting film comprises a variety of negative electrode active materials, a variety of conductive materials, and an adhesive. The adhesive comprises a triblock copolymer, the triblock copolymer comprising: a soft block comprising an aliphatic or alicyclic diene monomer unit and exhibiting a rubber phase at room temperature; a first hard block attached to one end of the soft block, comprising an olefinically unsaturated monomer unit containing an aromatic ring and exhibiting a glass phase at room temperature; and a second hard block attached to the other end of the soft block, comprising an olefinically unsaturated monomer unit containing an aromatic ring and exhibiting a glass phase at room temperature. The adhesive is in a discontinuous columnar shape, used to connect one of the various negative electrode active materials or one of the various conductive materials to another of the various negative electrode active materials or another of the various conductive materials. The average width of the adhesive perpendicular to its length direction is 50 nm or less. Attached Figure Description

[0013] The above and other objects, features and advantages of this disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings:

[0014] Figure 1 This is a schematic diagram showing the internal structure of the adhesive included in a self-supporting membrane for a negative electrode according to an embodiment of the present disclosure;

[0015] Figure 2 This is a schematic diagram illustrating a method for manufacturing a self-supporting membrane for a negative electrode according to an embodiment of the present disclosure;

[0016] Figure 3 This is a schematic diagram illustrating the adhesive variation mechanism in a method for manufacturing a self-supporting membrane for a negative electrode according to an embodiment of the present disclosure.

[0017] Figure 4 This is a schematic diagram showing the structure formed by the adhesive and the negative electrode active material in a self-supporting membrane for a negative electrode according to an embodiment of the present disclosure.

[0018] Figure 5 This is a schematic diagram showing the structure formed by the binder and the negative electrode active material in a conventional support membrane for the negative electrode that uses PTFE as a binder.

[0019] Figure 6 This is a diagram showing a SEM image of the powder formed from the negative electrode according to Example 1;

[0020] Figure 7 and Figure 8 This is a diagram showing a SEM image of a self-supporting membrane for a negative electrode according to Example 1;

[0021] Figure 9 This is a diagram showing a SEM image of the self-supporting membrane for the negative electrode according to Comparative Example 1;

[0022] Figure 10 This is a diagram showing SEM images of the self-supporting membrane for the negative electrode according to Comparative Example 2; and

[0023] Figure 11 This is a graph showing the data obtained from measuring the tensile strength of the self-supporting membrane for the negative electrode according to Example 1 and Comparative Examples 1 and 2. Detailed Implementation

[0024] To facilitate understanding of this disclosure, it will be described in more detail below. In this context, the terms or words used in this specification and claims should not be construed as having their common dictionary meaning, but rather should be interpreted in relation to the technical scope of this disclosure, based on the principle that the inventors can appropriately define the concepts of these terms to best interpret this disclosure.

[0025] In this disclosure, the term "monomer unit" can refer to a component, structure, or substance derived from a monomer. More specifically, a monomer unit can refer to a repeating unit of the polymer that is introduced into and participates in the polymerization reaction during polymer polymerization.

[0026] <Manufacturing Method of Self-Supporting Film for Negative Electrode>

[0027] This disclosure provides a method for manufacturing a self-supporting membrane for a negative electrode.

[0028] Traditionally, a dry-process technology has been used to manufacture lithium-ion battery cathodes using polytetrafluoroethylene (PTFE). PTFE possesses the lowest unoccupied molecular orbital (LUMO) energy level, making it prone to electron acceptance. Therefore, PTFE is electrochemically unstable under negative potential conditions. Consequently, lithium-ion battery anodes manufactured using PTFE as a binder exhibit poor cycle stability. Furthermore, when using PTFE to manufacture anodes, the PTFE binder decomposes during the initial charging operation, thereby reducing the initial efficiency of the lithium-ion battery.

[0029] Therefore, to obtain adhesives that exhibit electrochemical stability even at negative potentials, a technique employing triblock copolymers has been developed in recent years. This triblock copolymer comprises: a soft block derived from an aliphatic or alicyclic diene monomer and exhibiting a rubber phase at room temperature; a first hard block attached to one end of the soft block, derived from an aromatic ring-containing olefinically unsaturated monomer and exhibiting a glass phase at room temperature; and a second hard block attached to the other end of the soft block, derived from an aromatic ring-containing olefinically unsaturated monomer and exhibiting a glass phase at room temperature. However, according to this technique, the process for improving physical stability requires a longer time, and the self-supporting films manufactured for the negative electrode exhibit lower tensile strength.

[0030] This disclosure proposes using the aforementioned triblock copolymer as a binder, and mixing the negative electrode active material, conductive material and binder together using a grinding mill to shorten the entire process and improve the tensile strength of the manufactured self-supporting membrane for the negative electrode.

[0031] A method for manufacturing a self-supporting film for a negative electrode according to embodiments of the present disclosure includes the following steps: mixing and grinding a negative electrode forming composition comprising at least a negative electrode active material, a conductive material, and a binder to obtain a negative electrode forming powder (S1); and forming a negative electrode active material layer using the negative electrode forming powder through a film-forming process (S2). The binder comprises a triblock copolymer comprising: a soft block comprising an aliphatic or alicyclic diene monomer unit and exhibiting a rubber phase at room temperature; a first hard block attached to one end of the soft block comprising an olefinically unsaturated monomer unit containing an aromatic ring and exhibiting a glass phase at room temperature; and a second hard block attached to the other end of the soft block comprising an olefinically unsaturated monomer unit containing an aromatic ring and exhibiting a glass phase at room temperature. The average particle size (D) of the binder included in the negative electrode forming powder is... 50 Smaller than the average particle size (D) of the binder included in the negative electrode forming composition. 50 ).

[0032] The steps included in the method for manufacturing a self-supporting membrane for a negative electrode according to an embodiment of the present disclosure will be described in detail below.

[0033] 1. "S1"

[0034] A method for manufacturing a self-supporting film for a negative electrode may include the following steps: mixing and grinding a negative electrode forming composition comprising a negative electrode active material, a conductive material and a binder to obtain a negative electrode forming powder (S1).

[0035] According to one embodiment of this disclosure, the negative electrode active material may include at least one selected from carbon-based active materials, silicon-based active materials, metal-based active materials capable of forming alloys with lithium, and lithium-containing active materials.

[0036] According to one embodiment of this disclosure, the carbon-based active material may include, for example, graphite, hard carbon, soft carbon, or graphene. Graphite may be artificial graphite, natural graphite, a mixture of artificial and natural graphite, natural graphite coated with artificial graphite, or a combination thereof. The carbon-based active material exhibits minimal crystal structure changes during lithium-ion insertion and extraction, thus allowing for continuous and repeatable oxidation and reduction reactions, thereby achieving lithium-ion secondary batteries with higher capacity and longer lifespan.

[0037] According to one embodiment of this disclosure, the silicon-based active material may be, for example, Si or SiO. m, Si-C composite, Si-Q alloy, or a combination thereof. In addition, m satisfies 0 < m ≤ 2, Q is an alkali metal, alkaline earth metal, Group 13 to 16 element, transition metal, rare earth element, or a combination thereof, and Si is excluded from Q.

[0038] According to one embodiment of the present disclosure, the metal-based active material capable of alloying with lithium may be, for example, B, Al, Ga, In, Ge, Sn, Pb, P, As, Sb, Bi, Mg, Ca, Zn, Cd, Pd, Ag, Au, Pt, their alloys, or their oxides.

[0039] According to one embodiment of the present disclosure, the lithium-containing active material may be, for example, lithium-containing titanium composite oxide (LTO).

[0040] According to one embodiment of the present disclosure, the conductive material may include at least one selected from graphite, activated carbon, carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fibers.

[0041] According to one embodiment of the present disclosure, as Figure 1 shown, the binder may include a triblock copolymer, which includes: a soft block, which includes an aliphatic or alicyclic diene monomer unit and exhibits a rubber phase at room temperature; a first hard block, which is connected to one end of the soft block, includes an ethylenically unsaturated monomer unit containing an aromatic ring, and exhibits a glass phase at room temperature; and a second hard block, which is connected to the other end of the soft block, includes an ethylenically unsaturated monomer unit containing an aromatic ring, and exhibits a glass phase at room temperature.

[0042] According to one embodiment of the present disclosure, the soft block may impart excellent flexibility, extrusion molding property, and abrasion resistance to the triblock copolymer.

[0043] According to one embodiment of the present disclosure, the aliphatic or alicyclic diene monomer for forming the aliphatic or alicyclic diene monomer unit may be selected from at least one of butadienyl monomers, pentadienyl monomers, and hexadienyl monomers.

[0044] According to one embodiment of the present disclosure, the butadienyl monomer may include at least one selected from 1,2-butadiene, 1,3-butadiene, isoprene, and chloroprene.

[0045] According to one embodiment of this disclosure, the pentadienyl monomer may include a selection from 1,2-pentadiene, 1,3-pentadiene, 1,4-pentadiene, 2,3-pentadiene, 2-methyl-1,3-pentadiene, 2-methyl-1,4-pentadiene, 2-methyl-2,3-pentadiene, 2-methyl-2,4-pentadiene, 3-methyl-1,3-pentadiene, 3-methyl-1,4-pentadiene, 4-methyl-1,3-pentadiene, and 2-ethyl At least one of 1,3-pentadiene, 2-ethyl-1,4-pentadiene, 2-ethyl-2,4-pentadiene, 3-ethyl-1,3-pentadiene, 3-ethyl-1,4-pentadiene, 4-ethyl-1,3-pentadiene, 1-chloro-1,3-pentadiene, 1-chloro-2,4-pentadiene, 2-chloro-1,3-pentadiene, 3-chloro-1,3-pentadiene, 3-chloro-1,4-pentadiene, and 5-chloro-1,3-pentadiene.

[0046] According to one embodiment of this disclosure, the hexadienyl monomer may include a selection from 1,2-hexadiene, 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, 2,3-hexadiene, 2,4-hexadiene, 2,5-hexadiene, 3,5-hexadiene, 2-methyl-1,3-hexadiene, 2-methyl-1,4-hexadiene, 2-methyl-1,5-hexadiene, 2-methyl-2,3-hexadiene, 2-methyl-2,4-hexadiene, 3-methyl-1,2-hexadiene, 3-methyl-1,3-hexadiene, 3-methyl-1,4-hexadiene, 3-methyl At least one of 1,5-hexadiene, 3-methyl-2,4-hexadiene, 3-methyl-2,5-hexadiene, 4-methyl-1,3-hexadiene, 4-methyl-1,4-hexadiene, 4-methyl-2,3-hexadiene, 5-methyl-1,3-hexadiene, 5-methyl-1,4-hexadiene, 2-ethyl-1,3-hexadiene, 2-ethyl-1,4-hexadiene, 3-ethyl-1,2-hexadiene, 3-ethyl-1,3-hexadiene, 3-ethyl-1,4-hexadiene, 3-ethyl-1,4-hexadiene, and 3-ethyl-1,5-hexadiene.

[0047] According to one embodiment of this disclosure, the first hard block and the second hard block can impart higher strength properties to the triblock copolymer.

[0048] According to one embodiment, the aromatic ring in the olefinically unsaturated monomer used to form the aromatic ring-containing olefinically unsaturated monomer unit may be a substituted or unsubstituted benzene ring, or a substituted or unsubstituted naphthalene ring.

[0049] According to one embodiment of this disclosure, the aromatic ring may be attached to the main chain or side chain of the repeating unit of the first hard block and the second hard block, preferably to the side chain of the repeating unit of the first hard block and the second hard block.

[0050] According to one embodiment, the aromatic ring-containing olefinically unsaturated monomer used to form the aromatic ring-containing olefinically unsaturated monomer unit may be selected from at least one of styrene monomers and aromatic (meth)acrylic acid monomers.

[0051] According to one embodiment of this disclosure, the styrene monomer may include at least one selected from styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethoxystyrene, tert-butoxystyrene, p-acetoxystyrene, p-chlorostyrene, p-bromostyrene, 2,4-dimethylstyrene, 3,5-dimethylstyrene, and 2,4,6-trimethylstyrene.

[0052] According to one embodiment of this disclosure, the aromatic (meth)acrylic acid monomer may include at least one selected from benzyl acrylate, benzyl methacrylate, phenoxy acrylate, phenoxy methacrylate, phenyl acrylate, phenyl methacrylate, ethyl acrylate, and ethyl methacrylate.

[0053] According to one embodiment of this disclosure, the first and second hard blocks can be strongly bonded to the negative electrode active material or conductive material through π-π interactions based on the aromatic ring structure contained in the aromatic ring-containing olefinic unsaturated monomer unit. Furthermore, the first and second hard blocks can form crosslinks (connections) through physical bonding exhibiting relatively low binding energies. For example, the first and second hard blocks maintain their shape and size at or below the glass transition temperature, but are easily molded above the glass transition temperature. Therefore, when a self-supporting membrane for the negative electrode is manufactured at a temperature allowing the triblock copolymer to be molded, the individual hard blocks included in the triblock copolymer maintain their bond with the negative electrode active material or conductive material while being flexibly deformed. Thus, the binder portion provides physical crosslinking points (connection points) with a linear shape (discontinuous columnar or filamentous), and a robust three-dimensional network structure can be formed around the physical crosslinking points.

[0054] According to one embodiment of this disclosure, based on the total content of the triblock copolymer, the content of the first hard block and the second hard block can range from about 10 wt% to about 60 wt%, preferably from about 15 wt% to about 55 wt%, and more particularly from about 20 wt% to about 50 wt%. When the content of the first hard block and the second hard block meets this numerical range, the bonding force can be further improved through stronger interaction with the negative electrode active material or conductive material. Furthermore, the triblock copolymer can have suitable flexibility, thereby giving the triblock copolymer superior formability.

[0055] According to one embodiment of this disclosure, the weight-average molar mass of each of the first hard block and the second hard block can be in the range of about 9,000 g / mol to about 20,000 g / mol, preferably about 9,500 g / mol to about 20,000 g / mol, more preferably about 10,000 g / mol to about 20,000 g / mol. When the weight-average molar mass of each of the first hard block and the second hard block meets this range, the physical crosslinking force between the binder and the negative electrode active material or conductive material can be improved, thereby forming a more stable three-dimensional network, and the shape can be easily changed during electrode manufacturing, thereby further improving processability.

[0056] According to one embodiment of this disclosure, the glass transition temperature range of each of the first hard block and the second hard block can be from about 50°C to about 120°C. The glass transition temperature range of the soft block can be from about -120°C to about -50°C. Preferably, the glass transition temperature range of each of the first hard block and the second hard block can be from about 80°C to about 120°C. The glass transition temperature range of the soft block can be from about -120°C to about -80°C. More preferably, the glass transition temperature range of each of the first hard block and the second hard block can be from about 80°C to about 110°C. The glass transition temperature range of the soft block can be from about -110°C to about -80°C. Since the first hard block, the second hard block, and the soft block contained in the triblock copolymer all have glass transition temperatures within the above-mentioned numerical ranges, the composition for forming a lithium secondary battery anode containing a binder containing a triblock copolymer can be molded more reversibly, the durability and flexibility of the electrode manufactured from the composition can be better improved, and the shape of the electrode can be maintained more effectively.

[0057] According to one embodiment of this disclosure, the soft block, first hard block, and second hard block comprising the triblock copolymer can exhibit independent properties and are unaffected by each other. Therefore, the soft block provides flexibility to the final lithium-ion battery negative electrode self-supporting film, while the first and second hard blocks provide stronger adhesion to the negative electrode active material. Furthermore, since the soft block and the first and second hard blocks have different glass transition temperatures, the triblock copolymer is easily molded when the negative electrode self-supporting film is formed (calendered) at a temperature equal to or higher than the glass transition temperatures of the first and second hard blocks. Immediately after the self-supporting film is formed, exposing it to a temperature lower than the glass transition temperatures of the first and second hard blocks but equal to or higher than the glass transition temperature of the soft block, the triblock copolymer maintains both high strength and flexibility. Therefore, it is possible to prevent the lithium-ion battery negative electrode self-supporting film manufactured based on the triblock copolymer from easily breaking due to external stimuli.

[0058] According to one embodiment of this disclosure, the triblock copolymer is stable under negative potential, thereby suppressing side reactions. Therefore, when the triblock copolymer is used as a binder for the negative electrode of a lithium secondary battery, the electrode's lifetime characteristics can be improved.

[0059] According to one embodiment of this disclosure, the average particle size (D) of the binder contained in the negative electrode forming powder obtained by grinding in step "S1" is... 50 It can be smaller than the average particle size (D) of the binder contained in the negative electrode forming composition. 50 Therefore, as described below, the adhesive is easily dispersed during film formation and the average width of the columnar adhesive in the direction perpendicular to its length can be reduced.

[0060] According to one embodiment of this disclosure, the average particle size (D) of the binder (i.e., the binder before grinding) contained in the negative electrode forming composition is... 50 The average particle size of the binder before milling can be in the range of about 10 μm to about 50 μm. More specifically, the average particle size of the binder before milling can be at least about 12 μm, at least about 14 μm, at least about 16 μm, at least about 18 μm, or at least about 20 μm. Furthermore, the average particle size can be at most about 48 μm, at most about 46 μm, at most about 44 μm, at most about 42 μm, or at most about 40 μm. In this case, the average particle size of the binder (D...) 50 It can refer to the diameter corresponding to approximately 50% of the cumulative volume in the cumulative volume distribution measured by a laser diffraction / scattering particle size distribution measuring device.

[0061] According to one embodiment of this disclosure, the binder contained in the negative electrode forming composition is substantially spherical, and may be a true sphere or a near-true sphere. Specifically, the average sphericity may be in the range of about 0.7 to about 1.0, preferably about 0.8 to about 1.0, more preferably about 0.9 to about 1.0. In other words, prior to the preparation of the negative electrode self-supporting film, the binder particles in the lithium secondary battery negative electrode forming composition containing the binder can maintain a substantially spherical shape and be dispersed in the negative electrode forming composition.

[0062] In this case, the sphericity of the binder contained in the negative electrode forming composition is obtained by observing images of the binder particles through a scanning electron microscope (SEM), measuring the major and minor axes of 10 randomly selected binder particles, calculating the minor axis / major axis ratio of each particle, and then averaging the minor axis / major axis ratio. In this case, the closer the sphericity is to 1, the closer the shape of the binder is to a sphere.

[0063] According to one embodiment of this disclosure, in step “S1”, the mixing of the negative electrode active material, the conductive material and the binder can be carried out by a mill with a rotation speed of about 15,000 rpm to about 25,000 rpm, so mixing and milling can be carried out simultaneously.

[0064] According to one embodiment of this disclosure, step "S1" can be performed for a maximum of about 5 minutes. Specifically, step "S1" can be performed for a maximum of about 4 minutes, a maximum of about 3 minutes, a maximum of about 2 minutes, or a maximum of about 1 minute.

[0065] According to one embodiment of this disclosure, such as Figure 1 As shown, the particle size of the binder can be reduced as it is ground by the grinder. The average particle size (D) of the binder contained in the negative electrode forming powder (i.e., the binder abrasive) as a result of step "S1" is... 50 The average particle size can be in the range of about 1 μm to about 5 μm. More specifically, the average particle size of the binder abrasive can be at least about 1.1 μm, at least about 1.2 μm, at least about 1.3 μm, or at least about 1.4 μm. Furthermore, the average particle size can be at most about 4.5 μm, at most about 4 μm, at most about 3.5 μm, at most about 3 μm, or at most about 2 μm. Here, the average particle size of the binder (D...) 50 This refers to the diameter corresponding to approximately 50% of the cumulative volume in the cumulative volume distribution measured by a laser diffraction / scattering particle size distribution measuring device. Meanwhile, the grinding mill achieves a relatively low degree of fragmentation of the negative electrode active material and conductive material. Therefore, the particle size of the negative electrode active material and conductive material can remain almost unchanged.

[0066] As described above, because the binder is ground to a smaller particle size by a grinder, it can be better dispersed in the negative electrode forming powder. Therefore, the tensile strength of the prepared negative electrode self-supporting film can be enhanced.

[0067] 2. "S2"

[0068] According to one embodiment of the present disclosure, a method for manufacturing a negative electrode self-supporting film may include the following steps: using the negative electrode forming powder obtained in step “S1”, a negative electrode active material layer is formed by a film forming process (“S2”).

[0069] According to one embodiment of this disclosure, the film-forming process can be carried out using a dry method. In other words, the composition used in the film-forming process to form the negative electrode of a lithium secondary battery may virtually not contain a solvent. When a wet film-forming process is carried out, the presence of a liquid slurry limits the increase in electrode loading and makes it difficult to form a network structure between the binder and the active / conductive material. However, according to one embodiment of this disclosure, a dry film-forming process can increase the electrode loading, achieve higher energy density, and thereby manufacture a lithium secondary battery in which a network structure is effectively formed between the binder and the active material.

[0070] According to one embodiment of this disclosure, the film-forming process may include a calendering (rolling) process. In other words, as... Figure 3 As shown, a negative electrode active material layer can be formed by passing a composition comprising a negative electrode active material, a conductive material, and a binder for forming a negative electrode of a lithium secondary battery between a pair of rollers and pressing and rolling it. In this case, the diameter of the rollers can be from about 50 mm to about 1000 mm, preferably from about 100 mm to about 1000 mm, and more preferably from about 100 mm to about 500 mm.

[0071] According to one embodiment of this disclosure, the network structure between the adhesive and the active material is formed through a film-forming process. In this case, the network structure between the adhesive and the active material can refer to a discontinuous columnar network structure in which the adhesive connects the negative electrode active material or conductive material to another negative electrode active material or conductive material, such as... Figure 4 As shown. In other words, because discontinuous columnar (or filamentous) adhesives connect the outer surfaces of any one active material or conductive material to the outer surfaces of another, a composite with a mesh-like three-dimensional network structure can be formed (the active materials or conductive materials are located at the intersections, and the linear adhesives connect the active materials or conductive materials to each other). The formation of this three-dimensional network can be due to the strong π-π interactions between the first and second hard blocks contained in the triblock copolymer and the negative electrode active material or conductive material.

[0072] Furthermore, in the initial stage of the film-forming process, the adhesive containing the triblock copolymer comes into contact with the negative electrode active material or conductive material due to a large external force (shear or tensile force). Subsequently, as the external force decreases in the later stages of the film-forming process, the distance from the negative electrode active material or conductive material increases. Therefore, the adhesive containing the triblock copolymer in contact with the surface of the negative electrode active material or conductive material can flexibly change shape while maintaining its connection with the negative electrode active material or conductive material; thus, the adhesive can have a linear shape, such as a discontinuous columnar or filamentous form.

[0073] Furthermore, triblock copolymers can withstand pressure at temperatures permissible for film formation and transform into columnar structures, thus forming a three-dimensional network. The active material or conductive material is then interconnected with a discontinuous columnar binder to form this three-dimensional network, thereby producing a self-supporting lithium-ion battery anode membrane with excellent tensile strength.

[0074] Figure 5 This is a schematic diagram illustrating the structure formed by the binder and the negative electrode active material in a conventional negative electrode self-supporting membrane using PTFE as a binder. Figure 5 As shown, the adhesive is not connected to the negative electrode active material, which differs from the embodiment in this disclosure that uses a triblock copolymer as the adhesive. In other words, the difference between the conventional negative electrode self-supporting membrane and this disclosure is that the PTFE adhesive forms a network structure with connections between them, and the negative electrode active material is randomly overlapped and positioned on the network structure in a non-point contact manner (in this case, the portion partially obscured by the active particles shown as light lines in the figure corresponds to the network structure of the PTFE adhesive).

[0075] According to one embodiment of this disclosure, in step "S1" as described above, the binder contained in the negative electrode forming powder used in the film forming process is ground to an average particle size in the range of about 1 μm to about 5 μm. Therefore, the binder can be better dispersed in the negative electrode forming powder, thereby improving the tensile strength of the negative electrode self-supporting film.

[0076] Furthermore, since the average particle size of the binder contained in the negative electrode forming powder used in the film forming process is in the range of about 1 μm to about 5 μm, the binder in the negative electrode self-supporting film has a three-dimensional network structure and a discontinuous columnar shape that connects any one negative electrode active material or conductive material to another negative electrode active material or conductive material, and the average width of the binder perpendicular to the length direction is at most about 50 nm.

[0077] According to one embodiment of this disclosure, calendering can be 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. Specifically, calendering can be performed at a temperature of about 50°C to about 140°C, preferably about 80°C to about 140°C, and more preferably about 80°C to about 130°C. Therefore, the formability of the triblock copolymer containing the first hard block and the second hard block, and the adhesive containing the triblock copolymer, can be further improved.

[0078] According to one embodiment of this disclosure, an external force, such as shear force or tensile force, is applied by calendering, and a self-supporting film for the negative electrode of a lithium secondary battery can be prepared.

[0079] Specifically, the negative electrode active material layer manufactured by dry process can be a self-supporting negative electrode active material layer. This self-supporting negative electrode active material layer can be a film-like or thin-film negative electrode active material layer (i.e., a self-supporting film for negative electrodes), which is prepared to maintain a specific shape without being supported by other substrates. By preparing the above-mentioned self-supporting film for negative electrodes, the subsequent lamination process for manufacturing lithium secondary battery negative electrodes can be carried out smoothly.

[0080] <Self-supporting membrane for negative electrode>

[0081] This disclosure provides a negative electrode self-supporting membrane prepared by the above-described method for manufacturing a negative electrode self-supporting membrane.

[0082] According to one embodiment of this disclosure, the negative electrode self-supporting film comprises a variety of negative electrode active materials, a variety of conductive materials, and an adhesive. The adhesive comprises a triblock copolymer, which includes: a soft block comprising monomer units based on aliphatic or alicyclic dienes and exhibiting a rubber phase at room temperature; a first hard block connected to one end of the soft block and comprising olefinically unsaturated monomer units containing aromatic rings and exhibiting a glass phase at room temperature; and a second hard block connected to the other end of the soft block and comprising olefinically unsaturated monomer units containing aromatic rings and exhibiting a glass phase at room temperature. The adhesive is in a discontinuous columnar shape, connecting any one of the various negative electrode active materials or any one of the various conductive materials to another of the various negative electrode active materials or one of the various conductive materials, and the average width perpendicular to the length direction is approximately 50 nm or less.

[0083] The negative electrode active material, conductive material and adhesive contained in the negative electrode self-supporting film according to the embodiments of this disclosure have been described in the method for manufacturing the negative electrode self-supporting film, and therefore will not be repeated here.

[0084] According to one embodiment of this disclosure, the average width of the columnar adhesive contained in the negative electrode self-supporting film in the direction perpendicular to its length can be at most about 45 nm, at most about 40 nm, at most about 35 nm, at most about 30 nm, or at most about 25 nm, and at least about 5 nm, at least about 10 nm, at least about 15 nm, or at least about 20 nm. Since the adhesive particles are milled in "S1" prior to the film-forming process, the average width of the adhesive contained in the negative electrode self-supporting film in the direction perpendicular to its length can satisfy the above-mentioned range. Because the adhesive in the negative electrode self-supporting film is well dispersed, the above-mentioned three-dimensional structure is uniformly formed, thus the negative electrode self-supporting film exhibits excellent tensile strength in both the longitudinal (MD) and transverse (TD) directions.

[0085] According to one embodiment of this disclosure, when a negative electrode self-supporting film is irradiated with a 5.0 kV electron beam for at least 1 second to obtain a scanning electron microscope (SEM) image, a molten structure with an average width of approximately 30 nm perpendicular to the length direction is observed on the surface of the negative electrode active material or the conductive material. This molten structure may include a triblock copolymer comprising: a soft block comprising monomer units based on aliphatic or alicyclic dienes, exhibiting a rubber phase at room temperature; a first hard block connected to one end of the soft block, comprising an olefinically unsaturated monomer unit containing an aromatic ring, exhibiting a glass phase at room temperature; and a second hard block connected to the other end of the soft block, comprising an olefinically unsaturated monomer unit containing an aromatic ring, exhibiting a glass phase at room temperature.

[0086] According to one embodiment of this disclosure, when a negative electrode self-supporting film is irradiated with an electron beam of at least 5.0 kV to obtain a scanning electron microscope (SEM) image, the molten structure can refer to the portion of the adhesive melted on the surface of the negative electrode active material or the conductive material when the average width of the columnar adhesive contained in the negative electrode self-supporting film is about 30 nm or less. Therefore, since the composition of the molten structure is the same as the composition of the adhesive contained in the negative electrode self-supporting film, a detailed description of the composition of the molten structure will be omitted.

[0087] According to one embodiment of the present disclosure, the average thickness of the negative electrode self-supporting film can be from about 30 μm to about 500 μm, preferably in the range of about 50 μm to about 300 μm, and more preferably in the range of about 70 μm to about 200 μm.

[0088] <Lithium secondary battery anode>

[0089] According to another embodiment of this disclosure, a lithium secondary battery negative electrode is provided, which includes a current collector and a lithium secondary battery negative electrode self-supporting film disposed on the current collector.

[0090] When forming a self-supporting film for the negative electrode of a lithium-ion battery using a film-forming process, the self-supporting film can be placed on a current collector for lamination. Lamination can be performed using a lamination roller. In this case, the temperature of the lamination roller can be maintained between 80°C and 200°C. Through this lamination process, the self-supporting film for the negative electrode of the lithium-ion battery and the current collector can be bonded together.

[0091] The current collector is not particularly limited, as long as it has high conductivity and does not cause chemical changes in the battery. For example, the current collector may include stainless steel, aluminum, nickel, titanium, sintered carbon, copper, aluminum or alloys thereof, or materials obtained by surface treatment of stainless steel with carbon, nickel, titanium or silver.

[0092] <Lithium secondary batteries>

[0093] According to another embodiment of this disclosure, a lithium secondary battery is provided, including a lithium secondary battery negative electrode, a lithium secondary battery positive electrode, and an electrolyte.

[0094] The positive electrode of a lithium-ion secondary battery may contain at least one positive electrode active material selected from lithium, nickel, cobalt, manganese, iron, tin, silicon, aluminum, and mixtures thereof. More specifically, the positive electrode of a lithium-ion secondary battery may use, for example, LiCoO2, LiMnO2, LiFeO2, or Li(Ni)2. 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 O2, Li(Ni) 0.8 Mn 0.1 Co 0.1 O2, Li(Ni) 0.9 Mn 0.05 Co 0.05 O2, LiNi 0.6 Co 0.2 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiNi 0.85 Co 0.1 Al 0.05 O2, LiNi 0.88 Co 0.1 Al 0.02 Positive electrode active materials such as O2, LiMn2O4, and LiFePO4.

[0095] Electrolytes can be liquid electrolytes or solid electrolytes.

[0096] When the electrolyte is a liquid electrolyte, it may include lithium salts and non-aqueous organic solvents.

[0097] Lithium salts can include a variety of lithium salts, as long as they are commonly used in lithium secondary battery electrolytes. For example, lithium salts can include at least one compound selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(C2F5SO2)2, LiN(CF3SO2)2, CF3SO3Li, LiC(CF3SO2)3, LiC4BO8, LiTFSI, LiFSI, and LiClO4.

[0098] Non-aqueous organic solvents may include the types of organic solvents that can be used as non-aqueous electrolytes in the manufacture of typical lithium secondary batteries. In this case, the content of the non-aqueous organic solvent can be appropriately adjusted within the generally available range.

[0099] Specifically, non-aqueous organic solvents can include typical organic solvents such as cyclic carbonate solvents, linear carbonate solvents, ester solvents, or ketone solvents, which can be used as non-aqueous organic solvents for lithium secondary batteries. Non-aqueous organic solvents can not only contain these typical organic solvents, but also mixtures of at least two typical organic solvents.

[0100] Cyclic carbonate solvents may include at least one selected from ethylene carbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), propylene carbonate (PC), and butene carbonate (BC).

[0101] The linear carbonate solvent may include at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC).

[0102] The ester solvent may include at least one selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, and ε-caprolactone.

[0103] Ketone solvents may include polymethylvinyl ketone.

[0104] When the electrolyte is a liquid electrolyte, a lithium secondary battery may include a separator.

[0105] The diaphragm may comprise only commonly used porous polymer membranes prepared from, for example, polyolefin-based polymers (e.g., ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers), or may comprise porous polymer membranes laminated together. Alternatively, the diaphragm may employ common porous nonwoven fabrics, such as high-melting-point glass fibers or polyethylene terephthalate fibers, but this disclosure is not limited thereto. Furthermore, coated diaphragms containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in single-layer or multi-layer structures.

[0106] In this case, the pore size of the porous membrane is typically in the range of about 0.01 μm to about 50 μm, and the porosity is typically in the range of about 5% to about 95%. Furthermore, the thickness of the porous membrane is typically in the range of about 5 μm to about 300 μm.

[0107] Meanwhile, when the electrolyte is a solid electrolyte, it can be a polymer-based solid electrolyte, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or a mixture thereof.

[0108] Polymer-based solid electrolytes may include polyether-based polymers, polycarbonate-based polymers, acrylate polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene derivatives, alkylene oxide derivatives (e.g., polyethylene oxide), phosphate ester polymers, agitation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride and its derivatives, or polymers containing ionic dissociative groups. Furthermore, polymer electrolytes may include, for example, branched copolymers, comb-like polymers, and crosslinked polymers obtained by copolymerizing amorphous polymers as comonomers, such as PMMA, polycarbonate, polysiloxane, and / or phosphazene, with the main chain of polyethylene oxide (PEO), as polymer resins, and may include at least one of these.

[0109] Oxide-based solid electrolytes may include, for example, LLZO-based compounds and LLTO-based compounds (e.g., Li). 3x La 2 / 3- x TiO3), LISICON-based compounds (e.g., Li) 14 Zn(GeO4)4), LATP-based compounds (e.g., Li) 1.3 Al 0.3 Ti 1.7 (PO4)3), LAGP-based compounds (e.g., Li) 1+x Ge 2-x Al x (PO4)3) or LIPON-based compounds, but this disclosure is not limited thereto.

[0110] The sulfide-based solid electrolyte may include at least one of Li6PS5Cl, Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2SLi3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, or Li2S-GeS2-ZnS, but this disclosure is not limited thereto.

[0111] The embodiments of this disclosure will now be described in detail to enable those skilled in the art to readily reproduce them. However, this disclosure can be implemented in various forms and is not limited to the embodiments described herein.

[0112] Example 1

[0113] Under solvent-free conditions, graphite as the negative electrode active material, carbon as the conductive material, and SBS triblock copolymer (glass transition temperature of polystyrene block: 100℃, glass transition temperature of polybutadiene block: -100℃) as the binder are mixed at a mass ratio of 96:1:3 and then ground in a mill at a speed of 20,000 rpm or higher for one minute to obtain a negative electrode forming powder.

[0114] The obtained negative electrode forming powder is rolled using a twin-roll press heated to 120°C to manufacture a self-supporting membrane for the negative electrode.

[0115] Comparative Example 1

[0116] Graphite as the negative electrode active material, carbon as the conductive material, and SBS triblock copolymer (glass transition temperature of polystyrene block: 100℃, glass transition temperature of polybutadiene block: -100℃) as the binder were mixed at a mass ratio of 96:1:3 for 8 minutes under solvent-free conditions.

[0117] The mixed powder is rolled using a twin-roll press heated to 120°C to manufacture a self-supporting membrane for the negative electrode.

[0118] Comparative Example 2

[0119] Graphite (as the negative electrode active material), carbon (as the conductive material), and SBS triblock copolymer (glass transition temperature of polystyrene block: 100℃, glass transition temperature of polybutadiene block: -100℃) (as a binder) were mixed for 8 minutes at a mass ratio of 96:1:3 under solvent-free conditions. The mixed powder was then rolled using a twin-roll press heated to 120℃ to produce a self-supporting film to be ground.

[0120] The self-supporting membrane to be ground, formed by the film-forming process, is ground for 22 minutes by applying shear force using a grinding mill. The mixed powder produced by grinding is then put back into the rollers and subjected to a temperature of at least 100°C in the film-forming process to manufacture a self-supporting membrane for the negative electrode.

[0121] Experimental Example 1: SEM image of powder formed on the negative electrode

[0122] SEM images of the negative electrode powder formed according to Example 1 are shown below. Figure 6 As shown.

[0123] Experimental Example 2: SEM images of a self-supporting membrane used for the negative electrode

[0124] SEM images were obtained by irradiating the self-supporting films for negative electrodes manufactured according to Example 1, Comparative Example 1, and Comparative Example 2 with a 5.0 kV electron beam. The SEM images of the self-supporting films for negative electrodes manufactured according to Example 1, Comparative Example 1, and Comparative Example 2 are shown below. Figures 7 to 10 As shown.

[0125] refer to Figures 7 to 10 The self-supporting film for the negative electrode according to Example 1 was formed while the binder powder was being ground. It can be seen that the width of the columnar binder is 50 nm or less, which is finer than the width of the columnar binder in the self-supporting films for the negative electrode according to Comparative Examples 1 and 2 (where the binder powder was not ground).

[0126] Therefore, when SEM images of Example 1 were obtained by irradiating it with an electron beam of 5.0 kV for 2 seconds, columnar adhesives with a width of about 30 nm or less were observed to melt on the surface of the negative electrode active material or the conductive material under the action of the electron beam, thereby forming a molten structure. Meanwhile, the columnar adhesives of Comparative Examples 1 and 2 had a width in the range of about 0.2 μm to about 2 μm, which was significantly thicker than that of Example 1. Therefore, no molten structure formed by the electron beam was observed in the columnar adhesives of Comparative Examples 1 and 2.

[0127] Experimental Example 3: Measuring the tensile strength of a self-supporting membrane used for the negative electrode

[0128] The self-supporting membranes for the negative electrode manufactured according to Example 1, Comparative Example 1, and Comparative Example 2 were each stamped into pieces with a width of 2 cm and a length of 6 cm. Then, the tensile strength was measured using a UTM device at a rate of 5 mm / min, and the measured values ​​are shown in Table 1 below.

[0129] Table 1

[0130]

[0131] Referring to Table 1, it can be seen that, compared to the self-supporting films for the negative electrode according to Comparative Examples 1 and 2, the self-supporting film for the negative electrode according to Example 1 exhibits a shorter mixing time and increased tensile strength in both the MD and TD directions. Specifically, the self-supporting film for the negative electrode according to Example 1 exhibits increased tensile strength in the TD direction, which is confirmed by the significantly lower and unmeasurable tensile strength in the TD direction of Comparative Example 1, and the fact that the tensile strength in the TD direction of Comparative Example 2 is half that of Example 1.

[0132] In the method for manufacturing a self-supporting film for a negative electrode according to an embodiment of the present disclosure, a self-supporting film for a lithium secondary battery negative electrode, a lithium secondary battery negative electrode using the self-supporting film, and a lithium secondary battery can be manufactured. The self-supporting film is bonded to the negative electrode active material or conductive material through stronger interaction and is electrochemically stable under negative potential, while exhibiting excellent tensile strength and easy molding properties.

[0133] While this disclosure has been described above with reference to exemplary embodiments and accompanying drawings, it is not limited thereto, and various modifications and alterations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as claimed in the appended claims.

Claims

1. A method for manufacturing a self-supporting membrane for a negative electrode, the method comprising the following steps: Step S1: Obtaining negative electrode forming powder by mixing and grinding a negative electrode forming composition comprising a negative electrode active material, a conductive material, and a binder; and Step S2: Using the aforementioned negative electrode forming powder, a negative electrode active material layer is formed through a film-forming process. The adhesive comprises a triblock copolymer, the triblock copolymer comprising: The soft block comprises aliphatic or alicyclic diene monomer units and exhibits a rubber phase at room temperature; The first hard block, connected to one end of the soft block, comprises an olefinically unsaturated monomer unit containing an aromatic ring and exhibits a glassy phase at room temperature; and The second hard block, connected to the other end of the soft block, comprises an olefinically unsaturated monomer unit containing an aromatic ring and exhibits a glassy phase at room temperature; and The average particle size D of the binder contained in the negative electrode forming powder 50 Smaller than the average particle size D of the binder contained in the negative electrode forming composition 50 .

2. The method according to claim 1, wherein the binder included in the negative electrode forming composition is spherical and has an average sphericity in the range of 0.8 to 1.

0.

3. The method of claim 1, wherein the binder included in the negative electrode forming composition comprises an average particle size D 50 Particles in the range of 10 μm to 50 μm.

4. The method of claim 1, wherein step S1 is performed by a grinder, and wherein the rotational speed (RPM) of the grinder is in the range of 15,000 rpm to 25,000 rpm.

5. The method of claim 1, wherein the binder included in the negative electrode forming powder comprises an average particle size D 50 Particles in the range of 1 μm to 5 μm.

6. The method according to claim 1, wherein the film-forming process is performed using a dry method.

7. The method of claim 6, wherein the film-forming process includes calendering, and wherein the calendering is performed at a temperature equal to or higher than a first glass transition temperature and a second glass transition temperature corresponding to the first hard block and the second hard block, respectively.

8. The method of claim 1, wherein the glass transition temperature of each of the first hard segment and the second hard segment is in the range of 50°C to 120°C, and wherein the glass transition temperature of the soft segment is in the range of -120°C to -50°C.

9. The method according to claim 1, wherein the aliphatic or alicyclic diene monomer used to form the aliphatic or alicyclic diene monomer unit is at least one selected from butadienyl monomers, pentadienyl monomers, and hexadienyl monomers.

10. The method according to claim 1, wherein the aromatic ring-containing olefinically unsaturated monomer used to form the aromatic ring-containing olefinically unsaturated monomer unit is at least one selected from styrene monomers and aromatic (meth)acrylic acid monomers.

11. A self-supporting membrane for a negative electrode, the self-supporting membrane comprising: Various negative electrode active materials, various conductive materials and adhesives, The adhesive comprises a triblock copolymer, the triblock copolymer comprising: The soft block comprises aliphatic or alicyclic diene monomer units and exhibits a rubber phase at room temperature. The first hard block, which is connected to one end of the soft block, comprises an olefinic unsaturated monomer unit containing an aromatic ring and exhibits a glassy phase at room temperature; and The second hard block, which is connected to the other end of the soft block, comprises an olefinic unsaturated monomer unit containing an aromatic ring and exhibits a glassy phase at room temperature. The adhesive is in the form of discontinuous columns, connecting one of the plurality of negative electrode active materials or one of the plurality of conductive materials to another of the plurality of negative electrode active materials or another of the plurality of conductive materials. The average width of the adhesive perpendicular to its length direction is 50 nm or less.

12. The self-supporting film according to claim 11, wherein when the self-supporting film for the negative electrode is irradiated with an electron beam of 5.0 kV for at least 1 second to obtain a scanning electron microscope (SEM) image, the surface of the negative electrode active material or the surface of the conductive material comprises a molten structure with an average width perpendicular to the length direction of less than or equal to 30 nm, and The molten structure includes the triblock copolymer.

13. The self-supporting membrane of claim 11, wherein the glass transition temperature of each of the first hard segment and the second hard segment is in the range of 50°C to 120°C, and The glass transition temperature of the soft segment is in the range of -120°C to -50°C.

14. The self-supporting membrane according to claim 11, wherein the aliphatic or alicyclic diene monomer used to form the aliphatic or alicyclic diene monomer unit is at least one selected from butadienyl monomers, pentadienyl monomers and hexadienyl monomers.

15. The self-supporting membrane according to claim 11, wherein the aromatic ring-containing olefinically unsaturated monomer used to form the aromatic ring-containing olefinically unsaturated monomer unit is selected from at least one of styrene monomers and aromatic (meth)acrylic acid monomers.

16. A negative electrode for a lithium secondary battery, comprising: current collector; and The self-supporting membrane for the negative electrode according to any one of claims 11-15 is disposed on the current collector.

17. A lithium secondary battery, comprising: The negative electrode for a lithium secondary battery according to claim 16; Used as the positive electrode in lithium secondary batteries; as well as Electrolytes.

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