METHOD FOR PRODUCEING A FREESTANDING FILM FOR AN ANOD OF A LITHIUM SECONDARY BATTERY AND FREESTANDING FILM FOR AN ANOD OF A LITHIUM SECONDARY BATTERY PRODUCED BY THE SAME METHOD

Abstract

Method for producing a freestanding foil for an anode of a lithium secondary battery and freestanding foil for an anode of a lithium secondary battery produced by the same, wherein the method comprises: obtaining powders for forming the anode by mixing and grinding an anode-forming composition comprising an anode active material, a conductive material and a binder (S1), and forming an anode active material layer by a foil-forming process using the anode-forming powders (S2).The binder comprises a triblock copolymer comprising: a soft block having an aliphatic or cycloaliphatic diene monomer unit and exhibiting a rubbery phase at room temperature; a first hard block connected to one end of the soft block, having an ethylene unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature; and a second hard block connected to the other end of the soft block, having an ethylene unsaturated monomer unit containing an aromatic ring and exhibiting the glassy phase at room temperature; and an average particle diameter (D. 50 ) of the binder contained in the powders for forming the anode is smaller than an average particle diameter (D 50 ) of the binder contained in the composition for forming the anode.

Description

TECHNICAL AREA

[0001] The present disclosure / invention relates to a method for producing a freestanding film for an anode of a lithium secondary battery by inserting a triblock copolymer comprising a soft block and a hard block, and a freestanding film for an anode of a lithium secondary battery produced by the same. BACKGROUND

[0002] Lithium-ion batteries have been widely used since their commercialization in the 1990s and remain a highly researched energy storage device. Lithium-ion batteries meet certain requirements for use as an energy source in electric vehicles due to their higher operating voltage, higher energy density, lower self-discharge rate, higher power output, and longer cycle stability. However, lithium-ion batteries used in electric vehicles face three major challenges: stability, operating time, and cost. Stability and operating time can be improved by solid-state batteries (SSBs).The challenges of developing all-solid-state batteries (e.g., lithium-ion batteries) can be solved, but cost is a factor hindering (e.g., preventing) the widespread adoption of lithium-ion batteries. Accordingly, much study and research has been conducted to reduce the cost of lithium-ion batteries. Reducing the energy consumption required to manufacture or increase the thickness of an electrode is one of the most effective ways to lower the manufacturing costs of lithium-ion batteries. According to a conventional electrode manufacturing technology, a slurry, produced by mixing an electrode active material, a polymer binder, and a conductive additive with water or an organic solvent, is poured onto a current collector, and the resulting mixture is dried and compacted to form an electrode.In this case, the energy required to produce the slurry and coat the current collector accounts for 50% of the total energy consumed in the entire manufacturing process. Accordingly, studies and research have been conducted on a dry, solvent-free electrode manufacturing process to reduce the manufacturing costs of the lithium secondary battery. As an example of a dry electrode manufacturing process, a technology for producing a lithium secondary battery cathode using polytetrafluoroethylene (PTFE) has been developed. PTFE can possess the lowest unoccupied molecular orbitals (LUMOs) to readily accept electrons. Consequently, PTFE is electrochemically unstable in a negative potential environment.Accordingly, an anode of a lithium secondary battery manufactured using PTFE as a binder exhibits poorer cycle stability. Furthermore, if the anode is manufactured using PTFE, the PTFE binder degrades during initial charging, thus reducing the initial efficiency of the lithium secondary battery.

[0003] Although much study and research has been conducted on a dry electrode manufacturing technology, the development of a dry anode manufacturing technology capable of producing an anode with excellent physical properties such as malleability, electrochemical stability, or tensile strength remains insufficient. Therefore, further studies and research on this technology are needed. EXPLANATION OF INVENTION

[0004] The present disclosure / invention has been made to solve the above-mentioned problems that arise in the prior art, while retaining the advantages of the prior art.

[0005] One aspect of the present disclosure / invention provides a freestanding film (e.g., a freestanding layer) for a lithium secondary battery, which is capable of being easily formed, stabilized even at negative potential, and strongly bonded to an anode-active material by inserting a binder comprising a triblock copolymer having a hard block contributing to excellent mechanical properties and a soft block providing flexibility, and which is strongly bonded to the anode-active material and the conductive material by exhibiting excellent tensile strength and forming a three-dimensional network, and a method for producing the same, an anode for the lithium secondary battery comprising the freestanding film for the anode, and the lithium secondary battery.

[0006] The technical problems to be solved by the present disclosure / invention are not limited to the aforementioned problems, and any other technical problems not mentioned herein will be clearly understood by those skilled in the field to which the present disclosure / invention relates from the following description.

[0007] According to one aspect of the present disclosure / invention, a method for producing a freestanding film for an anode comprises: obtaining powders for forming the anode by mixing and milling an anode-forming composition containing an anode-active material, a conductive material, and a binder (S1), and forming an anode-active material layer by a film-forming process using the powders for forming the anode (S2). The binder comprises a triblock copolymer having a soft block containing an aliphatic or cycloaliphatic diene monomer unit and a rubber-like phase at room temperature (e.g.,a rubber-elastic phase), a first hard block connected to one end of the soft block, having an ethylene-unsaturated monomer unit containing an aromatic ring, and exhibiting a glassy phase at room temperature, and a second hard block connected to another end of the soft block, having an ethylene-unsaturated monomer unit containing an aromatic ring, and exhibiting the glassy phase at room temperature, and an average particle diameter (D. 50 ) of the binder contained in the powders for forming the anode is smaller than an average particle diameter (D 50 ) of the binder contained in the composition for forming the anode.

[0008] According to one aspect of the present disclosure / invention, a freestanding film for an anode comprises several anode-active materials, several conductive materials, and a binder. The binder comprises a triblock copolymer having a soft block containing an aliphatic or cycloaliphatic diene monomer unit and exhibiting a rubber-like phase at room temperature; a first hard block, bonded to one end of the soft block, having an ethylene-unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature; and a second hard block, bonded to another end of the soft block, having an ethylene-unsaturated monomer unit containing an aromatic ring and exhibiting the glassy phase at room temperature.The binder has an intermittent columnar shape to bond one anode-active material from the set of multiple anode-active materials, or one conductive material from the set of multiple conductive materials, to another anode-active material from the set of multiple anode-active materials, or to another conductive material from the set of multiple conductive materials. The binder has an average width of 50 nm perpendicular to a longitudinal direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other objectives, features and advantages of the present disclosure / invention will become clearer from the following detailed description in conjunction with the accompanying drawings: Fig. Figure 1 is a view schematically representing an internal structure of a binder contained in a freestanding film for an anode according to an embodiment of the present disclosure / invention. Fig. 2 is a view that schematically illustrates a method for producing a freestanding foil for an anode according to an embodiment of the present disclosure / invention, Fig. Figure 3 is a view that schematically depicts a mechanism for changing a binder in a manufacturing process of a freestanding film for an anode according to an embodiment of the present disclosure / invention. Fig. Figure 4 is a view schematically representing a structure in which a binder and an anode active material are formed in a freestanding film for an anode according to an embodiment of the present disclosure / invention. Fig. Figure 5 is a view that schematically represents a structure in which a binder and an anode active material are formed in a conventional freestanding film for an anode, using PTFE as the binder. Fig.Figure 6 is a view showing an SEM image of (e.g., of) powder(s) for forming an anode according to embodiment 1. Fig. 7 and Fig. 8 are a view (e.g., views) that represent an SEM image (e.g., SEM images) for a freestanding film for an anode according to embodiment 1, Fig. Figure 9 is a view showing a REM image for a freestanding film for an anode according to comparison example 1. Fig. Figure 10 is a view that represents a REM image for a freestanding film for an anode according to comparison example 2, and Fig. Figure 11 is a graph representing data obtained by measuring a tensile force of a freestanding foil for an anode according to embodiment 1 and comparative examples 1 and 2. DETAILED DESCRIPTION

[0010] The present disclosure / invention is described in more detail below for the purpose of understanding it. In this case, terms or words used in the present description and claims should not be interpreted according to their generally accepted dictionary meanings, but rather as relevant to the technical scope of the present disclosure / invention, based on the fact that the inventor can correctly define the concept of the terms to best explain the present disclosure / invention.

[0011] In the present disclosure / invention, the term "monomer unit" can refer to a component, structure, or material thereof that is derived from a monomer. More specifically, the monomer unit can refer to a repeating unit that forms a polymer, since a monomer is introduced to participate in a polymerization reaction when the polymer is polymerized. <Verfahren zum Herstellen einer freistehenden Folie für eine Anode>

[0012] The present disclosure / invention provides a method for producing a freestanding foil for an anode.

[0013] Traditionally, a dry electrode manufacturing process was used to produce the cathode of a lithium secondary battery using polytetrafluoroethylene (PTFE). PTFE can have a low LUMO level, making it readily accepting electrons. However, this property also makes PTFE electrochemically unstable in a negative potential environment. Consequently, a lithium secondary battery anode manufactured using PTFE as a binder exhibits poorer cycle stability. Furthermore, if the anode is manufactured using PTFE, the PTFE binder degrades during initial charging, thus reducing the initial efficiency of the lithium secondary battery.

[0014] Accordingly, a technology for incorporating a triblock copolymer was recently developed for a binder that is electrochemically stable even at negative potential. This copolymer consists of a soft block derived from an aliphatic or cycloaliphatic diene monomer, exhibiting a rubber-like phase at room temperature; a first hard block connected to one end of the soft block, derived from an ethylene-unsaturated monomer containing an aromatic ring, exhibiting a glassy phase at room temperature; and a second hard block connected to the other end of the soft block, also derived from an ethylene-unsaturated monomer containing an aromatic ring, exhibiting a glassy phase at room temperature. However, a process for improving a physical seal (e.g.,(a physical property) according to this technology a longer time and the freestanding foil for the anode that is produced shows a lower tensile force.

[0015] The present disclosure / invention proposes to use the above-described triblock copolymer as a binder and to mix an anode active material, a conductive material and the binder together by means of a mill (e.g. a grinding mill) in order to reduce the overall processes and improve the tensile strength of the freestanding film for the anode which has been produced.

[0016] The method for producing the freestanding foil for the anode according to an embodiment of the present disclosure / invention comprises the steps of obtaining powders for forming the anode by mixing and grinding compositions for forming the anode, comprising at least an anode active material, a conductive material and a binder (S1), and forming an anode active material layer by a foil-forming process using the powders for forming the anode (S2).The binder comprises a triblock copolymer, including a soft block containing an aliphatic or cycloaliphatic diene monomer unit and exhibiting a rubbery phase at room temperature; a first hard block, bonded to one end of the soft block, containing an ethylene-unsaturated monomer unit with an aromatic ring and exhibiting a glassy phase at room temperature; and a second hard block, bonded to the other end of the soft block, containing an ethylene-unsaturated monomer unit with an aromatic ring and exhibiting a glassy phase at room temperature. The average particle diameter (D. 50 ) of the binder contained in the powders for forming the anode is smaller than the average particle diameter (D 50 ) a binder contained in a composition for forming the anode.

[0017] The following describes in detail the steps of the method for producing the freestanding foil for the anode according to an embodiment of the present disclosure / invention. 1. ,S1'

[0018] The process for producing the freestanding foil for the anode may include the step of obtaining powders for forming the anode by mixing and grinding compositions for forming the anode, comprising the anode active material, the conductive material and the binder (S1).

[0019] According to one embodiment of the present disclosure / invention, the anode active material may comprise at least one selected from the group consisting of a carbon-based active material, a silicon-based active material, a metal-based active material enabling alloying with lithium, and a lithium-containing active material.

[0020] According to one embodiment of the present disclosure / invention, the carbon-based active materials can be, for example, graphite, hard carbon, soft carbon, or graphene. The graphite can be synthetic graphite, natural graphite, a mixture of synthetic and natural graphite, natural graphite coated with synthetic graphite, or a combination thereof. The carbon-based active material enables successive and repeated oxidation and reduction reactions because the crystal structure is less altered during the insertion and extraction of a lithium ion, thereby realizing a lithium secondary battery with higher capacity and longer lifespan. According to one embodiment of the present disclosure / invention, the silicon-based active material can be, for example, Si or SiO₂. m, a Si-C complex, a Si-Q alloy, or a combination thereof. Furthermore, ,m' satisfies 0 < m ≤ 2, ,Q' is an alkali metal, an alkaline earth metal, an element of group 13 to 16, a transition metal, a rare earth element, or a combination thereof, and Si is excluded from ,Q'.

[0021] According to one embodiment of the present disclosure / invention, the metal-based active material that allows alloying with lithium can be, for example, B, Al, Ga, In, Ge, Sn, Pb, P, As, Sb, Bi, Mg, Ca, Zn, Cd, Pd, Ag, Au, Pt, the alloy thereof (e.g. their alloy) or the oxide thereof (e.g. their oxide).

[0022] According to one embodiment of the present disclosure / invention, the lithium-containing active material can, for example, be a lithium-containing titanium composite oxide (LTO).

[0023] According to one embodiment of the present disclosure / invention, the conductive material may comprise at least one selected from the group consisting of graphite, activated carbon, carbon black, acetylene black, Ketjen black, a carbon nanotube, graphene and a carbon fiber.

[0024] According to one embodiment of the present disclosure / invention, as described in Fig.As shown in Figure 1, the binder can comprise a triblock copolymer comprising a soft block having an aliphatic or cycloaliphatic diene monomer unit and exhibiting a rubber-like phase at room temperature; a first hard block, connected to one end of the soft block, having an ethylene-unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature; and a second hard block, connected to the other end of the soft block, having an ethylene-unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature. According to one embodiment of the present disclosure / invention, the soft block can impart excellent flexibility, extrusion formability, and wear resistance to the triblock copolymer.

[0025] According to one embodiment of the present disclosure / invention, the aliphatic or cycloaliphatic diene-based monomer for forming the aliphatic or cycloaliphatic diene-based monomer unit can be at least one selected from the group consisting of a butadiene-based monomer, a pentadiene-based monomer, and a hexadiene-based monomer. According to one embodiment of the present disclosure / invention, the butadiene-based monomer can comprise at least one selected from the group consisting of 1,2-butadiene, 1,3-butadiene, isoprene, and chloroprene.

[0026] According to one embodiment of the present disclosure / invention, the pentadiene-based monomer may comprise at least one selected from the group consisting of 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, 2-ethyl-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.

[0027] According to one embodiment of the present disclosure / invention, the hexadiene-based monomer may comprise at least one selected from the group consisting of 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-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.According to one embodiment of the present disclosure / invention, the first hard block and the second hard block can impart a higher strength characteristic to the triblock copolymer.

[0028] According to one embodiment, an aromatic ring of an ethylene unsaturated monomer, which serves as the aromatic ring to form an ethylene unsaturated monomer unit containing an aromatic ring, can be a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring (e.g., an ethylene unsaturated monomer can have a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring as a structural element).

[0029] According to one embodiment of the present disclosure / invention, the aromatic ring can be associated with a main chain or a side chain of a repeating unit of the first hard block and the second hard block, and preferably with the side chain of the repeating unit of the first hard block and the second hard block.

[0030] According to one embodiment, the aromatic ring of the ethylene unsaturated monomer containing the aromatic ring can be formed by at least one selected from the group consisting of a styrene-based monomer and an aromatic (meth)acrylic monomer.

[0031] According to one embodiment of the present disclosure / invention, the styrene-based monomer may comprise at least one selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethoxystyrene, μ-butoxystyrene, p-acetoxystyrene, p-chlorostyrene, p-bromostyrene, 2,4-dimethylstyrene, 3,5-dimethylstyrene and 2,4,6-trimethylstyrene.

[0032] According to one embodiment of the present disclosure / invention, the aromatic (meth)acrylic monomer may comprise at least one selected from the group consisting of benzyl acrylate, benzyl methacrylate, phenoxyacrylate, phenoxymethacrylate, phenyl acrylate, phenyl methacrylate, phenyl ethyl acrylate and phenyl ethyl methacrylate.

[0033] According to one embodiment of the present disclosure / invention, the first hard block and the second hard block can be strongly bonded to the anode-active material or the conductive material by a pi-pi interaction based on the structure of the aromatic ring contained in the ethylene-unsaturated monomer unit that contains the aromatic ring. Furthermore, the first hard block and the second hard block can form a cross-link (connection) by physical bonding, exhibiting a relatively low bond energy. For example, the first hard block and the second hard block retain their shape and size at or below a glass transition temperature, but are easily deformed above the glass transition temperature.Accordingly, if the freestanding anode film is manufactured at a temperature that allows the triblock copolymer to be deformed, each hard block contained within the triblock copolymer retains its bond with the anode active material or the conductive material, allowing it to be flexibly reshaped. Thus, the binder segment provides a physical crosslinking point (connection point) with a linear shape (intermittent column or wire-like form), and a robust three-dimensional network structure can be formed around this physical crosslinking point.

[0034] According to one embodiment of the present disclosure / invention, the content of the first hard block and the second hard block can be in a range of about 10 wt% to about 60 wt%, preferably from about 15 wt% to about 55 wt%, and particularly from about 20 wt% to about 50 wt%, based on the total content of the triblock copolymer. If the content of the first hard block and the second hard block meets the numerical range of values, the bond strength can be improved by the stronger interaction with the anode active material or the conductive material. Furthermore, the triblock copolymer can exhibit reasonable flexibility, resulting in even better formability.

[0035] According to one embodiment of the present disclosure / invention, each of the first hard block and the second hard block can have a weight-average molar mass in the range of about 9,000 g / mol to about 20,000 g / mol, preferably from about 9,500 g / mol to about 20,000 g / mol, and more preferably from about 10,000 g / mol to about 20,000 g / mol. If the weight-average molar mass of the first hard block and the second hard block meets the numerical range of values, the physical crosslinking force between the binder and the anode active material or the conductive material can be improved to form a more stable three-dimensional network, and the shape can be easily modified when the electrode is fabricated, thus improving processability.

[0036] According to one embodiment of the present disclosure / invention, each of the first hard block and the second hard block can have a glass transition temperature in the range of about 50 °C to about 120 °C. The soft block can have a glass transition temperature in the range of about -120 °C to about -50 °C. Preferably, each of the first hard block and the second hard block can have a glass transition temperature in the range of about 80 °C to about 120 °C. The soft block can have a glass transition temperature in the range of about -120 °C to about -80 °C. More preferably, each of the first hard block and the second hard block can have a glass transition temperature in the range of about 80 °C to about 110 °C. The soft block can have a glass transition temperature in the range of about -110 °C to about -80 °C.Since each of the first hard block, the second hard block, and the soft block included in the triblock copolymer has a glass transition temperature within the numerical range, a composition for forming the anode of the lithium secondary battery, which includes the binder and the triblock copolymer, can be shaped more reversibly, the durability and flexibility of the electrode produced from the composition can be improved, and the shape of the electrode can be maintained more effectively.

[0037] According to one embodiment of the present disclosure / invention, the soft block, the first hard block, and the second hard block contained in the triblock copolymer can exhibit independent properties without influencing one another. Accordingly, the soft block can impart flexibility to the freestanding anode foil of a lithium secondary battery, which is an end product, and the first hard block and the second hard block can impart (e.g., a) stronger bond strength to the anode active material of the freestanding anode foil. Since the soft block, as well as the first and second hard blocks, have different glass transition temperatures, the triblock copolymer can also be easily deformed when the freestanding anode foil is formed (calendered) at the glass transition temperature or higher of the first and second hard blocks.Immediately after the freestanding film is formed, it is exposed to a temperature lower than the glass transition temperatures of the first and second hard blocks and equal to or higher than the glass transition temperature of the soft block (e.g., so that the triblock copolymer has flexibility while maintaining higher strength). Accordingly, the freestanding film for the anode of the lithium secondary battery, manufactured based on the triblock copolymer, can be prevented from being easily fractured by external stimulation.

[0038] According to one embodiment of the present disclosure / invention, the triblock copolymer is stabilized at a negative potential to suppress a side reaction. Accordingly, if the triblock copolymer is used as a binder for the anode of the lithium secondary battery, the lifetime characteristic of the electrode may be improved.

[0039] According to one embodiment of the present disclosure / invention, the average particle size (D 50 ) of the binder contained in the powders for forming the anode, by grinding in 'S1' be smaller than the average particle size (D 50) of the binder contained in the composition for forming the anode. Accordingly, the binder, as described below, can be easily dispersed in the foil-forming process, and an average width perpendicular to a longitudinal direction of the binder, which has a columnar shape, can be reduced.

[0040] According to one embodiment of the present disclosure / invention, the binder (i.e., the binder prior to grinding) contained in the composition for forming the anode can determine (e.g., an) average particle diameter (D). 50) in a range of approximately 10 µm to approximately 50 µm. In particular, the average particle diameter of the binder before milling can be at least approximately 12 µm, at least approximately 14 µm, at least approximately 16 µm, at least approximately 18 µm, or at least approximately 20 µm. Furthermore, the average particle diameter can be at most approximately 48 µm, at most approximately 46 µm, at most approximately 44 µm, at most approximately 42 µm, or at most approximately 40 µm. In this case, the average particle diameter (D) can be 50 ) of the binder to a diameter that corresponds to approximately 50% of the cumulative volume in the cumulative volume distribution measured by a laser diffraction / scattering type particle size distribution measuring device.

[0041] According to one embodiment of the present disclosure / invention, the binder contained in the anode-forming composition has a substantially spherical shape (e.g., substantially a spherical shape), a true spherical shape, or a nearly true spherical shape. In particular, the average sphericity can be in the range of about 0.7 to about 1.0, preferably about 0.8 to about 1.0, and more preferably about 0.9 to about 1.0. In other words, the particles of the binder in the anode-forming composition of the lithium secondary battery containing the binder can retain a substantially spherical shape and can be dispersed in the anode-forming composition before the freestanding foil for the anode is produced.

[0042] In this case, the sphericity of the binder contained in the anode composition is a value derived as the average of the shorter / longer diameter ratios of 10 randomly selected binder particles. This is calculated by measuring the longer and shorter diameters of each particle based on an image obtained through a scanning electron microscope (SEM). The ratio of the shorter / longer diameter of each particle is then calculated. In this case, it can be determined that the binder approximates the shape of a sphere, as the sphericity approaches the value 1.

[0043] According to one embodiment of the present disclosure / invention, in 'S1' the anode active material, the conductive material and the binder can be mixed by a mill rotating at a speed in the range of about 15,000 rpm to about 25,000 rpm, so that the mixing and grinding can be carried out simultaneously.

[0044] According to one embodiment of the present disclosure / invention, 'S1' can be performed for a maximum of approximately 5 minutes. In particular, 'S1' can be performed for a maximum of approximately 4 minutes, a maximum of approximately 3 minutes, a maximum of approximately 2 minutes, or a maximum of approximately 1 minute.

[0045] According to one embodiment of the present disclosure / invention, as described in Fig. As shown in Figure 1, the particle diameter of the binder can be reduced because it is ground by the mill. The average particle diameter (D 50The average particle diameter (D) of the binder (i.e., the ground binder) contained in the powders for forming the anode, which are a result in 'S1', can be in a range of approximately 1 µm to approximately 5 µm. Specifically, the average particle diameter of the ground binder can be at least approximately 1.1 µm, at least approximately 1.2 µm, at least approximately 1.3 µm, or at least approximately 1.4 µm. Furthermore, the average particle diameter can be at most approximately 4.5 µm, at most approximately 4 µm, at most approximately 3.5 µm, at most approximately 3 µm, or at most approximately 2 µm. 50The diameter of the binder here refers to a diameter that corresponds to approximately 50% of the cumulative volume in the cumulative volume distribution measured using a laser diffraction / scattering type particle size distribution device. Meanwhile, the anode active material and the conductive material are ground less finely (e.g., less comminuted) by the mill. Accordingly, the particle diameter of the anode active material and the conductive material can remain almost unchanged.

[0046] As described above, since the binder is milled to achieve a smaller particle diameter, it can be better dispersed in the powders used to manufacture the anode. Consequently, the tensile strength of the free-standing foil for the manufactured anode can be improved. 2. S2'

[0047] According to one embodiment of the present disclosure / invention, the method for producing the freestanding foil for the anode can include the step of forming the anode-active material layer by the foil-forming process using energies (e.g., powders) for anode formation obtained in 'S1' (S2). According to one embodiment of the present disclosure / invention, the foil-forming process can be carried out in a dry manner. In other words, the composition for forming the anode of the lithium secondary battery used in the foil-forming process need not contain any solvent. The foil-forming process carried out in a wet manner has a limitation in increasing the amount of charge on an electrode and has a difficulty in forming a network structure between the binder and an active / conductive material due to the liquid-phase slurry.However, according to one embodiment of the present disclosure / invention, the film-forming process, which is carried out in a dry manner, makes it possible to increase the charging quantity of the electrode in order to achieve a higher energy density, thereby producing a lithium secondary battery which has an effectively formed network structure between the binder and the active material.

[0048] According to one embodiment of the present disclosure / invention, the film-forming process can include a calendering (rolling) process. In other words, as in Fig.As shown in Figure 3, the anode-active material layer can be formed by allowing the composition for forming the anode of the lithium secondary battery, which comprises the anode-active material, the conductive material, and the binder, to pass between a pair of rollers, and pressing and rolling the composition. In this case, the roller can have a diameter in the range of about 50 mm to about 1000 mm, preferably in the range of about 100 mm to about 1000 mm, and even more preferably in the range of about 100 mm to about 500 mm.

[0049] According to one embodiment of the present disclosure / invention, the network structure between the binder and the active material is formed by the film-forming process. In this case, the network structure between the binder and the active material can be an intermittent columnar network structure in which the binder connects one anode-active material or a conductive material and another anode-active material or a conductive material, as shown in Fig.Figure 4 illustrates this. In other words, since the binder, which has the form of a non-continuous column (or wire), connects an outer surface of one active or conductive material to another, a complex three-dimensional network structure with a net-like shape can be formed (the active or conductive material is positioned at an intersection point, and a linear binder connects the active or conductive materials). Such a three-dimensional network can be formed due to the stronger pi-pi interaction between the first and second hard blocks, which the triblock copolymer exhibits, and the anode active or conductive material.

[0050] Furthermore, the binder comprising the triblock copolymer comes into contact with the anode active material or the conductive material during the initial phase of the film formation process due to higher external forces (shear or tensile). Therefore, as the external force decreases in the later phase of the film formation process, the distance between the binder and the anode active material or conductive material increases. Consequently, the binder comprising the triblock copolymer, which is in contact with the surface of the anode active material or conductive material, can flexibly change its shape while maintaining contact with the anode active material or conductive material. Thus, the binder can have a linear form, such as an intermittent column or a wire shape.

[0051] Furthermore, the triblock copolymer can be subjected to pressure and altered at a temperature that enables the film-forming process, allowing it to be brought into a columnar shape and thus forming the three-dimensional network. The active or conductive material and the binder, which has the intermittent columnar shape, are bonded together to form the three-dimensional network, thereby producing the freestanding film for the anode of the lithium secondary battery, which has excellent tensile strength.

[0052] Fig. Figure 5 is a view that schematically represents the structure formed by the binder and the anode active material in the conventional freestanding anode foil that uses PTFE as the binder. As shown in Fig.As shown in Figure 5, the binder is not bonded to the anode active material, which differs from an embodiment of the present disclosure / invention which uses the triblock copolymer as the binder. In other words, the conventional freestanding film for the anode differs from the present disclosure / invention in that a bond is formed between the PTFE binders to create a network structure (e.g., a PTFE network structure), and the anode active material is randomly overlapped and positioned on the network structure without point contact (in this case, a section shown as faint lines partially obscured by the active particles corresponds to the network structure of the PTFE binder).

[0053] According to one embodiment of the present disclosure / invention, the binder contained in the anode-forming powders used in the foil-forming process is milled to obtain an average particle diameter in the range of about 1 µm to about 5 µm in 'S1', as described above. Accordingly, the binder in the anode-forming powders can be dispersed even more effectively, thereby improving the tensile strength of the freestanding foil for the anode.

[0054] Furthermore, since the average particle diameter of the binder contained in the powders for forming the anode used in the foil-forming process covers the range of about 1 µm to about 5 µm, the binder can have the three-dimensional network structure in the freestanding foil for the anode and the intermittent column shape to connect any anode active material or conductive material, and any other anode active material or conductive material can have an average width of at most about 50 nm perpendicular to the longitudinal direction.

[0055] According to one embodiment of the present disclosure / invention, calendering can be carried out 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. In particular, calendering can be carried out at a temperature in the range of about 50 °C to about 140 °C, preferably from about 80 °C to about 140 °C, and even more preferably from about 80 °C to about 130 °C. Accordingly, the formability of the triblock copolymer comprising the first hard block and the second hard block, and of the binder comprising the same, can be further improved.

[0056] According to one embodiment of the present disclosure / invention, an external force, such as a shear force or an external force, is applied by calendering, whereby the freestanding foil for the anode of the lithium secondary battery can be produced in the final stage.

[0057] In particular, the dry-processed anode active material layer can be a freestanding anode active material layer. This freestanding anode active material layer (i.e., a freestanding anode foil) can be a membrane or film designed to maintain a specific shape independently, without being supported (e.g., carried) on another base. The freestanding anode foil described above facilitates the subsequent lamination process for manufacturing the anode for the lithium secondary battery. <Freistehende Folie für Anode>

[0058] The present disclosure / invention provides a freestanding foil for an anode, which is produced by the method of producing the freestanding foil for the anode.

[0059] According to one embodiment of the present disclosure / invention, the freestanding film for the anode comprises several anode active materials, several conductive materials, and a binder, and the binder comprises a triblock copolymer comprising a soft block containing a diene-based aliphatic or cycloaliphatic monomer unit and exhibiting a rubber-like phase at room temperature, a first hard block bonded to one end of the soft block comprising an ethylene unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature, and a second hard block bonded to another end of the soft block comprising an ethylene unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature.The binder has an intermittent column shape to connect any anode-active material from the multiple anode-active materials or any conductive material from the multiple conductive materials and another anode-active material from the multiple anode-active materials or a conductive material from the multiple conductive materials, and has an average width of about 50 nm perpendicular to the longitudinal direction.

[0060] The anode active materials, the conductive material and the binder contained in the freestanding foil for the anode according to one embodiment of the present disclosure / invention have already been described in the description of the method for producing the freestanding foil for the anode, so details thereof are omitted.

[0061] According to one embodiment of the present disclosure / invention, the binder, which has a columnar shape and is contained in the freestanding anode foil, can have an average width perpendicular to the longitudinal direction that is in a range of at most about 45 nm, at most about 40 nm, at most about 35 nm (e.g., 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. The binder contained in the freestanding anode foil can have an average width perpendicular to the longitudinal direction that meets the aforementioned range because the binder particles are milled in 'S1' prior to the foil-forming process.Since the binder is excellently dispersed in the freestanding film for the anode, so that the three-dimensional structure described above is formed uniformly, the freestanding film for the anode is excellent in terms of both tensile strength in a machine direction (MD) and tensile strength in a transverse direction (TD).

[0062] According to one embodiment of the present disclosure / invention, when an electron beam of 5.0 kV is directed onto the freestanding foil for the anode for at least one second in order to obtain a scanning electron microscopy (SEM) image, a molten structure with an average width of about 30 nm, perpendicular to the longitudinal direction, is observed on the surface of the anode active material or the surface of the conductive material.The molten structure can have a triblock copolymer comprising a soft block containing an aliphatic or cycloaliphatic diene-based monomer unit and exhibiting a rubbery phase at room temperature, a first hard block connected to one end of the soft block, comprising an ethylene unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature, and a second hard block connected to the other end of the soft block, comprising an ethylene unsaturated monomer unit containing an aromatic ring and exhibiting a glassy phase at room temperature.

[0063] According to one embodiment of the present disclosure / invention, when the electron beam of at least 5.0 kV is directed onto the freestanding anode foil to obtain the scanning electron microscopy (SEM) image, the molten structure can be described as part of the binder that is fused onto the surface of the anode active material or the surface of the conductive material, since a portion of the binder, having an average width of about 30 nm or less and in the form of a column, and contained in the freestanding anode foil, is melted by the electron beam. Accordingly, since the molten structure has the same composition as the binder contained in the freestanding anode foil, the details of the composition of the molten structure are omitted.According to one embodiment of the present disclosure / invention, the average thickness of the freestanding foil for the anode can be in a range of about 30 µm to about 500 µm, preferably in a range of about 50 µm to about 300 µm and more preferably in a range of about 70 µm to about 200 µm. <Anode für Lithium-Sekundärbatterie>

[0064] According to a further embodiment of the present disclosure / invention, an anode for a lithium secondary battery is provided, which has a current collector and a freestanding foil for the anode of the lithium secondary battery, which is provided on the current collector.

[0065] Once the free-standing foil for the lithium secondary battery anode is formed through the foil-forming process, it can be applied to the current collector to be laminated. Lamination can be carried out using a laminating roller. In this case, the laminating roller can be kept at a temperature of 80°C to 200°C. The free-standing foil for the lithium secondary battery anode and the current collector can then be bonded together through this lamination process.

[0066] The pantograph is not particularly limited as long as it has high conductivity without causing any chemical changes in the battery. The pantograph can be made of, for example, stainless steel, aluminum, nickel, titanium, sintered carbon, copper, aluminum, or an alloy thereof, or a material obtained by surface-treating a stainless steel surface with carbon, nickel, titanium, or silver. <Lithium-Sekundärbatterie>

[0067] According to another embodiment of the present disclosure / invention, a lithium secondary battery is provided which has an anode for the lithium secondary battery, a cathode for the lithium secondary battery and an electrolyte.

[0068] The cathode for the lithium secondary battery can comprise at least one cathode active material selected from the group consisting of lithium, nickel, cobalt, manganese, iron, tin, silicon, aluminum, and a mixture thereof. In particular, the cathode for the lithium secondary battery can be formed from a cathode active material such as 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 0Al 0,2 O2, LiNi 0,7 Co 0,2 0Al 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 O2, LiMn2O4, LiFePO4.

[0069] The electrolyte can be a liquid electrolyte or a solid electrolyte.

[0070] If the electrolyte is a liquid electrolyte, it may contain a lithium salt and a non-aqueous organic solvent.

[0071] The lithium salt can contain various lithium salts, as long as these different lithium salts are commonly used as electrolytes in lithium secondary batteries. For example, the lithium salt can contain at least one compound selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(C2F5SO2)2, LiN(CF3SO2)2, CF3SO3Li, LiC(CF3SO2)3, LiC4BO8, LiTFSI, LiFSI, and LiClO4.

[0072] The non-aqueous organic solvent may be of a type suitable for use as a non-aqueous solvent in the manufacture of a typical lithium secondary battery. In this case, the concentration of the non-aqueous organic solvent can be appropriately adjusted within a typical usable range.

[0073] In particular, the non-aqueous organic solvent can contain typical organic solvents, such as a cyclic carbonate solvent, a linear carbonate solvent, an ester solvent, or a ketone solvent, which can be used as a non-aqueous organic solvent in lithium secondary batteries. The non-aqueous organic solvent can also contain a mixture of at least two of these typical organic solvents.

[0074] The cyclic carbonate solvent may include at least one selected from the group consisting of ethylene carbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC), propylene carbonate (PC) and butylene carbonate (BC).

[0075] The linear carbonate solvent may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC) and ethyl propyl carbonate (EPC).

[0076] The ester solvent may include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone and ε-caprolactone.

[0077] The ketone solvent may contain polymethyl vinyl ketone.

[0078] If the electrolyte is a liquid electrolyte, the lithium secondary battery may have a separator.

[0079] The separator may comprise (e.g., only) a porous polymer film, commonly used and manufactured using, for example, a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene-butene copolymer, an ethylene-hexene copolymer, or an ethylene methacrylate copolymer, or it may comprise porous polymer films laminated together. Alternatively, the separator may utilize an ordinary porous nonwoven fabric, such as a higher melting point glass fiber or a polyethylene terephthalate fiber, the present disclosure / invention being no longer limited to such applications. Furthermore, a coated separator containing ceramic components or polymeric materials may be used to ensure heat resistance or mechanical strength, and it may optionally be implemented in a single-layer or multi-layer structure.

[0080] In this case, the pore diameter of the porous separator typically ranges from approximately 0.01 µm to approximately 50 µm, and the porosity ranges from approximately 5% to approximately 95%. Furthermore, the thickness of the porous separator typically ranges from approximately 5 µm to approximately 300 µm.

[0081] However, if 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.

[0082] The polymer-based solid electrolyte can be a polyether-based polymer, a polycarbonate-based polymer, an acrylate polymer, a polysiloxane-based polymer, a phosphagen-based polymer, a polyethylene derivative, an alkylene oxide derivative such as polyethylene oxide, a phosphoric acid ester polymer, polydiation lysine, a polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride and a derivative thereof, or a polymer with an ionic dissociation group. Furthermore, the polymer electrolyte can, for example, be a branched copolymer, a comb-like polymer, or a cross-linked polymer obtained by copolymerization of an amorphous polymer such as PMMA, polycarbonate, polysiloxane, and / or phosphazene, which serves as a comonomer to a polyethylene oxide (PEO) backbone as a polymer resin, and may include at least one of these.

[0083] The solid oxide-based electrolyte can, for example, be an LLZO-based compound or an LLTO-based compound such as Li 3x La 2 / 3-x TiO3, a LISICON-based compound like Li 14 Zn(GeO4)4, a LATP-based compound such as Li 1,3 Al 0,3 Ti 1,7 (PO4)3, a LAGP-based compound such as (Li 1+x Ge 2-x Al x (PO4)3) or a LIPON-based compound, but the present disclosure / invention is not limited thereto.

[0084] The sulfide-based solid electrolyte can comprise at least one of the following: Li6PS5Cl, Li2S-P2S5, Li2S-Lil-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 the present disclosure / invention is not limited thereto. An embodiment of the present disclosure / invention is described in detail below so that those skilled in the art can easily reproduce the embodiment of the present disclosure / invention. However, the present disclosure / invention can be implemented in various forms and is (e.g., not) limited to the embodiments described herein. Example 1

[0085] Graphite, serving as the anode active material, carbon, serving as the conductive material, and an SBS triblock copolymer, serving as the binder (glass transition temperature of a polystyrene block: 100 °C, glass transition temperature of a polybutadiene block: -100 °C), having a mass ratio of 96:1:3, were mixed and milled without solvent at 20,000 rpm or more for one minute using a mill, yielding powders for forming the anode.

[0086] The resulting powder for forming the anode was rolled using a two-roll press heated to 120 °C to produce the freestanding foil for the anode. Comparative example 1

[0087] Graphite, serving as the anode active material, carbon, serving as the conductive material, and an SBS triblock copolymer, serving as the binder (glass transition temperature of a polystyrene block: 100 °C, glass transition temperature of a polybutadiene block: -100 °C), which have a mass ratio of 96:1:3, were mixed without solvent for eight minutes.

[0088] The mixed powder was rolled using a two-roll press heated to 120 °C to produce the freestanding foil for the anode. Comparative example 2

[0089] Graphite, serving as the anode active material, carbon, serving as the conductive material, and an SBS triblock copolymer, serving as the binder (glass transition temperature of a polystyrene block: 100 °C, glass transition temperature of a polybutadiene block: -100 °C), having a mass ratio of 96:1:3, were mixed for eight minutes without solvent. The mixed powder was rolled using a two-roll press heated to 120 °C to produce the freestanding film to be milled.

[0090] The freestanding foil to be ground, which was formed by the foil-forming process, was ground for 22 minutes using a mill to apply shear forces, mixed forces (e.g. mixed powders) produced by the grinding were put back into a roller, and a temperature of at least 100 °C was applied to the result while the foil-forming process was carried out to produce the freestanding foil for the anode. Experimental example 1: SEM image taken for powder used to form the anode

[0091] The SEM image for powder used to form the anode according to Example 1 is in Fig. 6 shown. Experimental example 2: SEM image taken for a freestanding film for an anode

[0092] SEM images were obtained by irradiating the freestanding anode foils, which were prepared according to Example 1 and Comparative Examples 1 and 2, with a 5.0 kV electron beam. The SEM images of the freestanding anode foils, which were prepared according to Example 1 and Comparative Examples 1 and 2, were in Fig. Numbers 7 to 10 are shown.

[0093] Referring to Fig.From 7 to 10, the freestanding anode foil according to Example 1 was formed in the state where the binder powders were milled. Accordingly, it can be seen that the width of the columnar binder was 50 nm or less, which is thinner than the width of the columnar binders in the freestanding anode foils according to Comparative Examples 1 and 2, where the binder powders were not milled. Therefore, it can be observed that the columnar binder with a width of approximately 30 nm or less is melted on the surface of the anode active material or the surface of the conductive material by the electron beam to form the molten structure when the SEM image is obtained by irradiation with a 5.0 kV electron beam for two seconds according to Example 1.Meanwhile, the binder, which has the column shape according to comparative examples 1 and 2, has a width in the range of approximately 0.2 µm to approximately 2 µm, which is significantly thicker than example 1. Accordingly, the molten structure formed by the electron beam is not observed in the binder, which has the column shape according to comparative examples 1 and 2.

[0094] Experimental Example 3: Measured Tensile Force of the Freestanding Anode Foil. Each of the freestanding anode foils produced according to Example 1 and Comparative Examples 1 and 2 was die-cut and prepared to a width of 2 cm and a length of 6 cm. The resulting tensile force was then measured at a rate of 5 mm / min using UTM equipment, and the measured value is shown in Table 1 below. Table 1 Classification Loading amount (mg / cm³) 2 ) Binder content (wt.%) Mixing time (min) Tensile force (MPa) MD direction TD direction Example 1 20 3 1 1,68 1,01 Comparative example 1 8 0,73 Immeasurable Comparative example 2 30 1,50 0,51

[0095] Referring to Table 1, it can be seen that the freestanding anode foil according to Example 1 showed a shorter mixing time and improved tensile strength in the MD and TD directions compared to the freestanding anode foils according to Comparison Examples 1 and 2. In particular, the freestanding anode foil according to Example 1 showed improved tensile strength in the TD direction, which can be determined by the fact that the tensile strength in the TD direction according to Comparison Example 1 was significantly lower and not measurable, and the tensile strength in the TD direction according to Comparison Example 2 was half the tensile strength in the TD direction according to Example 1.

[0096] In the method for producing the freestanding foil for the anode according to an example of the present disclosure / invention, the freestanding foil for the anode of the lithium secondary battery, the anode for the lithium secondary battery which uses the same, and the lithium secondary battery can be produced in which the freestanding foil is bound to the anode active material or the conductive material by the stronger interaction and is electrochemically stabilized at a negative potential, while exhibiting excellent tensile strength and a property of easy formability.

[0097] Although the present disclosure / invention has been described with reference to exemplary examples and the accompanying drawings, the present disclosure / invention is not limited thereto, but can be modified and altered in various ways by those skilled in the field to which the present disclosure / invention relates, without deviating from the idea and scope of the present disclosure / invention as claimed in the following claims.

Claims

[1] Method for producing a freestanding foil for an anode, wherein the method comprises: Obtaining powders for forming the anode by mixing and grinding an anode-forming composition comprising an anode active material, a conductive material and a binder (S1), and Formation of an anode active material layer by a foil-forming process that uses the powders to form the anode, (S2), wherein the binder comprises a triblock copolymer, wherein the triblock copolymer comprises: a soft block that has an aliphatic or cycloaliphatic diene monomer unit and exhibits a rubbery phase at room temperature, a first hard block, which is connected to one end of the soft block, has an ethylene-unsaturated monomer unit containing an aromatic ring, and exhibits a glassy phase at room temperature, and a second hard block connected to another end of the soft block, has an ethylene unsaturated monomer unit containing an aromatic ring, and exhibits the glassy phase at room temperature, and where an average particle diameter (D 50 ) of the binder contained in the powders for forming the anode is smaller than an average particle diameter (D 50 ) of the binder contained in the composition for forming the anode. [2] Method according to claim 1, wherein the binder included in the composition for forming the anode has a spherical shape and an average sphericity in a range of 0.8 to 1.

0. [3] Method according to claim 1 or 2, wherein the binder included in the composition for forming the anode comprises a particle having an average particle diameter (D 50) in a range of 10 µm to 50 µm. [4] Method according to any one of claims 1 to 3, wherein 'S1' is carried out by a mill and wherein the mill has a rotational speed (rpm) in the range of 15 000 rpm to 25 000 rpm. [5] Method according to any one of claims 1 to 4, wherein the binder contained in the powders for forming the anode comprises a particle having an average particle diameter (D 50 ) in a range of 1 µm to 5 µm. [6] Method according to any one of claims 1 to 5, wherein the film-forming process is carried out in a dry manner. [7] Method according to claim 6, wherein the film-forming process comprises calendering, and wherein the calendering is carried out at a temperature which is equal to or higher than a first glass transition temperature and a second glass transition temperature which correspond to the first hard block and the second hard block respectively. [8] Method according to any one of claims 1 to 7, wherein each of the first hard block and the second hard block has a glass transition temperature in a range of 50 °C to 120 °C, and wherein the soft block has a glass transition temperature in a range of -120 °C to -50 °C. [9] Method according to any one of claims 1 to 8, wherein an aliphatic or cycloaliphatic diene monomer for forming the aliphatic or cycloaliphatic diene monomer unit is selected from the group consisting of a butadiene-based monomer, a pentadiene-based monomer and a hexadiene-based monomer. [10] Method according to any one of claims 1 to 9, wherein an ethylene unsaturated monomer containing the aromatic ring is selected from the group consisting of a styrene-based monomer and an aromatic (meth)acrylic monomer for forming the ethylene unsaturated monomer unit containing the aromatic ring. [11] Freestanding foil for an anode, wherein the freestanding foil has: several anode active materials, several conductive materials and a binder, wherein the binder comprises a triblock copolymer, wherein the triblock copolymer comprises: a soft block which has an aliphatic or cycloaliphatic diene monomer unit and exhibits a rubbery phase at room temperature, a first hard block, which is connected to one end of the soft block, has an ethylene-unsaturated monomer unit containing an aromatic ring, and exhibits a glassy phase at room temperature, and a second hard block, which is connected to another end of the soft block, has an ethylene unsaturated monomer unit containing an aromatic ring, and shows the glassy phase at room temperature, wherein the binder has an intermittent column shape to connect one anode active material from the multiple anode active materials or one conductive material from the multiple conductive materials to another anode active material from the multiple anode active materials or another conductive material from the multiple conductive materials, and the binder has an average width of 50 nm perpendicular to a longitudinal direction. [12] Freestanding film according to claim 11, wherein a surface of the anode active material or a surface of the conductive material has a molten structure perpendicular to the longitudinal direction of the surface having an average width of less than or equal to 30 nm when an electron beam of 5.0 kV is directed onto the freestanding film for the anode for at least one second to obtain a scanning electron microscope (SEM) image, and wherein the molten structure comprises the Triblock copolymer. [13] Freestanding film according to claim 11 or 12, wherein each of the first hard block and the second hard block has a glass transition temperature in a range of 50 °C to 120 °C, and wherein the soft block has a glass transition temperature in a range of -120 °C to -50 °C. [14] Freestanding film according to any one of claims 11 to 13, wherein an aliphatic diene monomer for forming the aliphatic diene monomer unit is selected from the group consisting of a butadiene-based monomer, a pentadiene-based monomer and a hexadiene-based monomer. [15] Freestanding film according to any one of claims 11 to 14, wherein an ethylene unsaturated monomer containing the aromatic ring is selected from the group consisting of a styrene-based monomer and an aromatic (meth)acrylic monomer for forming the ethylene unsaturated monomer unit containing the aromatic ring. [16] Anode for a lithium secondary battery, which has: a current collector, and a freestanding film for the anode according to any one of claims 11 to 15, which is provided on the current collector. [17] Lithium secondary battery, which features: an anode for the lithium secondary battery according to claim 16, a cathode for the lithium secondary battery, and an electrolyte.

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