A negative electrode binder, a negative electrode sheet, a lithium ion battery, and a method for manufacturing the same

Abstract

The application discloses a negative electrode adhesive, a negative electrode sheet, a lithium ion battery and a preparation method thereof. The method comprises the following steps: carbonizing a first adhesive to obtain a conductive adhesive, wherein the first adhesive is a polymer rich in at least one of a hydroxyl group, a carboxyl group and an amino group; and mixing a second adhesive and the conductive adhesive to obtain the negative electrode adhesive, wherein the second adhesive comprises polyacrylic acid. The negative electrode adhesive, the negative electrode sheet, the lithium ion battery and the preparation method thereof can effectively solve the problem of volume expansion caused by a silicon-based negative electrode material as a negative electrode active material.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a negative electrode binder, a negative electrode sheet, a lithium-ion battery, and a method for preparing the same. Background Technology

[0002] Lithium-ion batteries possess advantages such as high operating voltage, light weight, small size, long cycle life, high energy density, and environmental friendliness, and are currently widely used in products such as mobile phones, tablets, laptops, and electric vehicles. As a new type of energy storage battery, in order to overcome its technological limitations and enable it to replace traditional energy sources, lithium-ion batteries need to possess higher energy density and faster charge / discharge performance to meet the development demands of high-energy-density lithium-ion batteries.

[0003] Novel silicon-based anode materials possess high capacity (4200 mAh / g) and a higher lithium intercalation platform than graphite, resulting in superior safety. However, during cycling, volume expansion leads to silicon particle pulverization, damaging the electrode structure and causing a sharp decline in lithium-ion battery capacity and poor cycle performance. The main function of anode binders is to bond and maintain the silicon-based anode material, stabilizing the electrode structure and mitigating the expansion or contraction of the silicon-based anode material during charging and discharging. In existing technologies, commonly used silicon-based anode binders, such as polyacrylic acid (PAA), have a linear structure and contain a large number of carboxyl groups, resulting in excessive hydrogen bonding that hinders the free rotation of molecular chains. This leads to poor electrode flexibility, making it difficult to withstand the stress generated by the volume expansion of nano-silicon particles. Therefore, using such silicon-based anode binders cannot solve the volume expansion problem caused by silicon-based anode materials as the active anode material.

[0004] Therefore, how to suppress the volume expansion caused by silicon-based anode materials as anode active substances has become a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] This application provides a negative electrode binder, a negative electrode sheet, a lithium-ion battery, and a method for preparing the same, to solve the problem of volume expansion caused by silicon-based negative electrode materials as negative electrode active materials in the prior art.

[0006] To solve one or more of the above-mentioned technical problems, the technical solution adopted in this application is:

[0007] In a first aspect, this application provides a method for preparing a negative electrode adhesive, the method comprising:

[0008] A conductive adhesive is obtained by carbonizing the first adhesive, wherein the first adhesive is a polymer rich in at least one of hydroxyl, carboxyl, and amino groups;

[0009] The negative electrode adhesive is obtained by mixing the second adhesive and the conductive adhesive, wherein the second adhesive comprises polyacrylic acid.

[0010] Furthermore, the first adhesive includes at least one of sodium carboxymethyl cellulose, sodium alginate, guar gum, konjac gum, gelatin, and k-carrageenan.

[0011] Furthermore, the carbonization temperature for the first adhesive is 120-450℃.

[0012] Furthermore, the carbonization time for the first adhesive is 0.5-16 hours.

[0013] Secondly, this application also provides a negative electrode adhesive, which is prepared by the above-mentioned method for preparing negative electrode adhesive.

[0014] Thirdly, corresponding to the aforementioned negative electrode binder, this application provides a method for preparing a negative electrode sheet, the method comprising:

[0015] A silicon-based anode material, anode conductive agent, the aforementioned anode binder, and solvent are mixed evenly to obtain anode slurry.

[0016] The negative electrode sheet is obtained by coating the negative electrode slurry onto the surface of the negative electrode current collector and then drying it.

[0017] Specifically, silicon-based anode material, anode conductive agent, anode binder and deionized water are mixed to form anode active material. After stirring for 0.5-4 hours, anode slurry is obtained. Then, deionized water is added to adjust the viscosity of the anode slurry to 3000-4000 cps.

[0018] Specifically, the negative electrode slurry is coated onto the surface of the negative electrode current collector and dried at 80-120°C to obtain the negative electrode sheet.

[0019] Furthermore, the mass of the silicon-based anode material is 85%-96% of the mass of the anode sheet.

[0020] Furthermore, the mass of the negative electrode conductive agent is 0.2%-5% of the mass of the negative electrode sheet.

[0021] Furthermore, the mass of the negative electrode adhesive is 1%-11.8% of the mass of the negative electrode sheet.

[0022] Furthermore, the negative electrode conductive agent includes at least one of acetylene black, carbon black, Ketjen black, carbon nanotubes, and carbon fibers.

[0023] Fourthly, this application also provides a negative electrode sheet, which is prepared by the above-mentioned method for preparing negative electrode sheets.

[0024] Furthermore, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector, the negative active material layer including the aforementioned negative electrode material, negative electrode conductive agent and negative electrode binder.

[0025] Optionally, the shape of the negative electrode current collector may include a foil shape, a plate shape, or a mesh shape.

[0026] Optionally, the negative electrode current collector includes any one of aluminum, copper, nickel, or zinc.

[0027] Optionally, the negative electrode current collector includes any one of aluminum, copper, nickel, or zinc alloy.

[0028] Fifthly, corresponding to the aforementioned negative electrode, this application provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a separator, an electrolyte, and the aforementioned negative electrode.

[0029] Furthermore, the positive electrode sheet includes a positive current collector and a positive active material layer covering the surface of the positive current collector.

[0030] Furthermore, the positive electrode current collector is made of copper, stainless steel, aluminum, nickel, titanium, or a metal current collector whose surface has been treated with carbon or other substances.

[0031] Furthermore, the positive current collector can typically have a thickness of 3 μm to 500 μm.

[0032] Furthermore, the positive electrode active material layer comprises a positive electrode active material.

[0033] Specifically, the positive electrode active material comprises a lithium transition metal composite oxide, which contains lithium and at least one other transition metal selected from the group consisting of nickel, cobalt, manganese and aluminum; preferably, it may contain lithium and transition metals such as nickel, cobalt or manganese.

[0034] Furthermore, the positive electrode active material layer may also include a positive electrode binder and / or a positive electrode conductive material.

[0035] According to the specific embodiments provided in this application, the following technical effects are disclosed:

[0036] This application provides a negative electrode binder, a negative electrode sheet, a lithium-ion battery, and a method for preparing the same. By introducing a conductive binder into the second binder, it addresses the volume expansion problem caused by using silicon-based negative electrode materials as the active negative electrode material in existing technologies. The conductive binder possesses excellent adhesion and conductivity, resulting in a synergistic effect between the second binder and the conductive binder. This improves the interfacial properties of the binder itself, enhances the flexibility and conductivity of the electrode sheet, and improves the adhesion and mechanical strength between the various materials of the negative electrode and between the materials of the negative electrode and the current collector. This effectively improves the cycle performance of the silicon-based negative electrode material.

[0037] Furthermore, since the conductive binder has good conductivity, it can reduce the use of conductive agents and increase the energy density of the electrode. In addition, the conductive binder has strong adhesion to silicon, which can ensure the structural stability of the negative electrode material and effectively improve the cycle performance of lithium-ion batteries.

[0038] Of course, any product implementing this application does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0039] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art are within the scope of protection of this application.

[0040] As described in the background section, commonly used silicon-based anode binders such as polyacrylic acid (PAA) have a linear structure and contain a large number of carboxyl groups, resulting in excessive hydrogen bonds that hinder the free rotation of molecular chains. The electrode's poor flexibility makes it difficult to withstand the stress caused by the volume expansion of nano-silicon particles. Using this type of silicon-based anode binder cannot solve the problem of volume expansion caused by silicon-based anode materials as anode active materials.

[0041] To address one or more of the aforementioned problems, this application creatively proposes a negative electrode binder, a negative electrode sheet, a lithium-ion battery, and a method for preparing the same. By introducing a conductive binder into the second binder, the volume expansion problem caused by using silicon-based negative electrode materials as the active negative electrode material in existing technologies is solved. The conductive binder possesses excellent adhesion and conductivity, resulting in a synergistic effect between the second binder and the conductive binder. This improves the interfacial properties of the binder itself, enhances the flexibility and conductivity of the electrode sheet, and improves the adhesion and mechanical strength between the various materials of the negative electrode and between the various materials of the negative electrode and the current collector, effectively improving the cycle performance of the silicon-based negative electrode material.

[0042] The following are optional technical solutions for this application, but are not intended to limit the technical solutions provided in this application. The technical objectives and beneficial effects of this application can be better achieved through the following optional technical solutions.

[0043] This application provides a negative electrode binder, comprising a conductive binder and a second binder, wherein the conductive binder is obtained by carbonization of the first binder, and the repeating unit of the molecular structure of the first binder includes at least one group selected from hydroxyl, carboxyl, and amino groups.

[0044] Understandably, carbonization refers to the process by which hydrogen and oxygen elements in organic compounds are removed due to the reaction at high temperatures under anaerobic or oxygen-deficient conditions.

[0045] The carbonization process of the first adhesive in this application is as follows: the first adhesive is placed in a processing device and carbonized at 120-450℃ for 0.5-16 hours. After carbonization is completed, the conductive adhesive is taken out.

[0046] In one embodiment, the conductive adhesive is a biomass adhesive.

[0047] In one embodiment, the conductive binder is at least one of sodium carboxymethyl cellulose, carboxymethyl cellulose, lithium carboxymethyl cellulose, biomass gum, sodium alginate, guar gum, konjac gum, gelatin, and k-carrageenan.

[0048] It is understandable that biomass gums, carboxymethyl cellulose and their derivatives contain abundant hydroxyl, carboxyl and amino groups, and these groups are highly reactive groups in the molecular structure.

[0049] The conductive binder obtained by carbonizing the first binder exhibits better adhesion, improving the adhesion and mechanical strength between the various materials of the negative electrode and between the materials of the negative electrode and the current collector, thereby effectively enhancing the cycle performance of the silicon-based negative electrode material. Furthermore, due to the excellent conductivity of this conductive binder, the amount of conductive agent used can be reduced, increasing the energy density of the electrode. Moreover, the strong adhesion between this conductive binder and the silicon substrate ensures the structural stability of the negative electrode material, effectively improving the cycle performance of the lithium-ion battery.

[0050] In a preferred embodiment, the second adhesive comprises polyacrylic acid (PAA).

[0051] It is understandable that the molecular structure of polyacrylic acid is as follows:

[0052]

[0053] Polyacrylic acid (PAA) is known as a binder, but due to its linear structure and the presence of numerous carboxyl groups, the hydrogen bonds in its structure hinder the free rotation of the molecular chains. This results in poor electrode flexibility and difficulty in withstanding the stress caused by the volume expansion of silicon nanoparticles. Therefore, using PAA alone cannot solve the problem of volume expansion caused by silicon-based anode materials as the active material. Furthermore, because PAA has a linear long-chain structure, the stress generated by the volume expansion of the active material can easily lead to chain breakage and deactivation of PAA.

[0054] To address this issue, this application introduces the aforementioned conductive adhesive into polyacrylic acid (PAA). The conductive adhesive possesses excellent adhesion and conductivity, resulting in a synergistic effect between PAA and the conductive adhesive. This improves the interfacial properties of the adhesive itself, enhances the flexibility and conductivity of the electrode, and improves the adhesion and mechanical strength between the various materials of the negative electrode and between the various materials of the negative electrode and the current collector. This effectively enhances the cycle performance of silicon-based negative electrode materials.

[0055] In one embodiment, the second adhesive is lithium-ionized polyacrylic acid.

[0056] It is understandable that lithium-ionized polyacrylic acid refers to a compound formed by replacing the hydrogen atoms of the carboxyl group (-COOH) in polyacrylic acid with lithium. The preparation of lithium-ionized polyacrylic acid can be achieved by introducing a basic lithium compound into polyacrylic acid and forming lithium-ionized polyacrylic acid through a neutralization reaction. However, the neutralization reaction should avoid the excessive use of basic lithium compounds, as excessive alkali leads to alkali residue, which affects the battery manufacturing process and electrochemical performance.

[0057] Preferably, the second adhesive is a mixture of lithium-ionized polyacrylic acid and polyacrylic acid.

[0058] In one embodiment, the molar ratio of lithium-ionized polyacrylic acid to polyacrylic acid is 1:1000-1000:1.

[0059] Compared to polyacrylic acid, lithium-ionized polyacrylic acid has higher polarity, which makes the battery manufacturing process easier, especially during the slurry process, as lithium-ionized polyacrylic acid can dissolve better in polar solvents.

[0060] Preferably, the molecular weight of the polyacrylic acid is 4,000-2,000,000, and more preferably, the molecular weight of the polyacrylic acid is 450,000-175,000.

[0061] Preferably, the molecular weight of the lithium-ionized polyacrylic acid is 4,000-2,000,000, and more preferably, the molecular weight of the polyacrylic acid is 450,000-175,000.

[0062] More preferably, the second adhesive comprises a variety of polyacrylic acids with different average molecular weights.

[0063] More preferably, the second adhesive comprises a variety of lithium-ionized polyacrylic acid with different average molecular weights.

[0064] More preferably, the second adhesive comprises polyacrylic acid and lithium-ionized polyacrylic acid with different numbers of repeating units.

[0065] More preferably, the average molecular weight of any two adhesives in the second adhesive is greater than 300,000.

[0066] If the molecular weight of polyacrylic acid and / or lithium-ionized polyacrylic acid is too large, the processing performance of the binder will decrease, and it will greatly affect the dispersion performance of the conductive binder; if the molecular weight is too small, it will affect the adhesion performance of the electrode and will not be conducive to the battery maintaining good cycle performance.

[0067] This application further provides a negative electrode, which includes a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material and a negative electrode binder.

[0068] Furthermore, the silicon-based anode material includes any one or a combination of at least two of elemental silicon, silicon alloys, silicon carbide compounds, or silicon oxide compounds; preferably, the silicon-based anode material is mixed with graphite.

[0069] It is understood that when the negative electrode active material is a mixture of silicon and graphite, this application does not particularly limit the specific ratio. Without departing from the inventive concept of this application, all known silicon-carbon composite active materials can be used in this application.

[0070] Meanwhile, silicon anode active materials exhibit a significant volume effect during use, especially during the first charge and discharge cycle; the expansion volume effect of silicon anodes is known.

[0071] Optionally, the negative electrode active material in the negative electrode active material layer may be doped with one or more conductive agents that provide an electron conduction path.

[0072] Conductive agents may include carbon-based materials, powdered nickel or other metal particles, or conductive polymers. Carbon-based materials may include particles such as carbon black, graphite, SuperP, acetylene black (e.g., KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, poly(3,4-ethylenedioxythiophene)polysulfonated styrene, etc.

[0073] Furthermore, the mass of the silicon-based anode material is 85%-96% of the mass of the anode active material layer, the mass of the conductive agent is 0.2%-5% of the mass of the anode active material layer, and the mass of the anode binder is 1%-11.8% of the mass of the anode active material layer.

[0074] Particularly preferably, due to the use of the conductive binder in this application, the mass of the conductive binder is 0.5-1.5 wt% of the negative electrode active material layer.

[0075] Specifically, the mass of the silicon-based anode material can be 85%, 88%, 90%, 92%, 94%, or 96% of the anode mass, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0076] Specifically, the mass of the negative electrode conductive agent can be 0.2%, 0.5%, 1%, 2%, 3%, 4% or 5% of the mass of the negative electrode sheet, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0077] Specifically, the mass of the negative electrode adhesive can be 1%, 3%, 5%, 7%, 9%, 11%, or 11.8% of the mass of the negative electrode sheet, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0078] In certain specific embodiments, the negative electrode active material layer may also include other additives. It is understood that, without departing from the inventive concept of this application, the use of additional additives, including but not limited to solid electrolytes, should still be considered within the scope of protection of this application.

[0079] This application does not specifically limit the negative electrode current collector. As long as it is conductive and does not cause chemical changes in the battery, it is acceptable without departing from the inventive concept of this application. This is merely an illustrative example and not a limitation on the scope of protection. The current collector can facilitate the flow of electrons between the negative electrode and the external circuit. The current collector may include metals, such as metal foil, metal grids or screens, or metal mesh. For example, the current collector may be formed of aluminum, stainless steel and / or nickel, or any other suitable conductive material known to those skilled in the art.

[0080] In one embodiment, the negative electrode active material layer can be a multilayer structure, wherein at least one layer includes a negative electrode active material, and the negative electrode active material is a silicon-based negative electrode active material and uses the binder described in this application.

[0081] It is understandable that when the negative electrode sheet has a multilayer structure, the ratio of the binder content of the silicon-containing layer to the negative electrode active material meets the requirements mentioned above when the negative electrode active material layer has a single-layer structure.

[0082] This application also provides a method for preparing a negative electrode adhesive, the method comprising:

[0083] S11: Carbonize the first adhesive to obtain a conductive adhesive, wherein the first adhesive is a polymer rich in at least one of hydroxyl, carboxyl, and amino groups.

[0084] In this embodiment, the first binder includes at least one selected from sodium carboxymethyl cellulose, sodium alginate, guar gum, konjac gum, gelatin, and k-carrageenan. The carbonization of the first binder can be carried out in a muffle furnace. Specifically, the carbonization temperature for the first binder is 120-450°C, and the carbonization time is 0.5-16 hours. The conductive binder obtained by carbonizing the first binder has better adhesion, which can improve the adhesion and mechanical strength between the various materials of the negative electrode and between the various materials of the negative electrode and the current collector, thereby effectively improving the cycle performance of the silicon-based negative electrode material. Furthermore, because this conductive binder has good conductivity, the use of conductive agents can be reduced, increasing the energy density of the electrode. Moreover, the conductive binder has strong adhesion to the silicon substrate, ensuring the structural stability of the negative electrode material and effectively improving the cycle performance of the lithium-ion battery.

[0085] S12: The negative electrode adhesive is obtained by mixing the second adhesive and the conductive adhesive, wherein the second adhesive comprises polyacrylic acid.

[0086] In this embodiment, the second adhesive comprises polyacrylic acid (PAA). Because PAA has a linear structure and contains numerous carboxyl groups, excessive hydrogen bonding hinders the free rotation of the molecular chains. This results in poor electrode flexibility, making it difficult to withstand the stress generated by the volume expansion of the silicon nanoparticles. Using PAA alone cannot solve the problem of volume expansion caused by silicon-based anode materials as the anode active material. Furthermore, because PAA has a linear long-chain structure, the stress generated by the volume expansion of the anode active material can easily lead to chain breakage and deactivation of the PAA.

[0087] To address this issue, this application introduces the aforementioned conductive adhesive into polyacrylic acid (PAA). The conductive adhesive provided in this application has excellent adhesion and conductivity, resulting in a synergistic effect between PAA and the conductive adhesive. This improves the interfacial properties of the adhesive itself, enhances the flexibility and conductivity of the electrode, and improves the adhesion and mechanical strength between the various materials of the negative electrode and between the various materials of the negative electrode and the current collector. This effectively improves the cycle performance of silicon-based negative electrode materials.

[0088] This application also provides a negative electrode adhesive, which is prepared by the above-mentioned method for preparing negative electrode adhesive. This negative electrode adhesive can solve the problem of volume expansion caused by silicon-based negative electrode materials as negative electrode active materials in the prior art.

[0089] Corresponding to the above-mentioned negative electrode binder, this application provides a method for preparing a negative electrode sheet, the method comprising:

[0090] S21: The negative electrode material, negative electrode conductive agent, negative electrode binder and solvent are mixed evenly to obtain a negative electrode slurry, wherein the negative electrode binder is the negative electrode binder mentioned above.

[0091] Specifically, silicon-based anode material, anode conductive agent, anode binder and deionized water are mixed to form anode active material. After stirring for 0.5-4 hours, anode slurry is obtained. Then, deionized water is added to adjust the viscosity of the anode slurry to 1000-7000 cps.

[0092] Furthermore, the silicon-based anode material comprises any one or a combination of at least two of elemental silicon, silicon alloys, silicon-carbon compounds, or silicon-oxygen compounds. The anode conductive agent comprises at least one of acetylene black, carbon black, Ketjen black, carbon nanotubes, and carbon fibers.

[0093] Furthermore, the mass of the silicon-based negative electrode material is 85%-96% of the mass of the negative electrode sheet, the mass of the negative electrode conductive agent is 0.2%-5% of the mass of the negative electrode sheet, and the mass of the negative electrode binder is 1%-11.8% of the mass of the negative electrode sheet.

[0094] Specifically, the mass of the silicon-based anode material can be 85%, 88%, 90%, 92%, 94%, or 96% of the mass of the anode sheet, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0095] Specifically, the mass of the negative electrode conductive agent can be 0.2%, 0.5%, 1%, 2%, 3%, 4% or 5% of the mass of the negative electrode sheet, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0096] Specifically, the mass of the negative electrode adhesive can be 1%, 3%, 5%, 7%, 9%, 11%, or 11.8% of the mass of the negative electrode sheet, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0097] S22: The negative electrode slurry is coated onto the surface of the negative electrode current collector and then dried to obtain the negative electrode sheet.

[0098] Specifically, the negative electrode slurry is coated onto the surface of the negative electrode current collector and dried at 80-120°C to obtain the negative electrode sheet.

[0099] This application does not impose any particular limitation on the negative electrode current collector. As long as it is conductive and does not cause chemical changes in the battery, it is acceptable, provided that it does not violate the inventive concept of this application.

[0100] This application further provides a battery, including a positive electrode, an electrolyte, and a negative electrode as described in this application.

[0101] This application does not specifically limit the positive electrode. Any known positive electrode structure and material can be used in this application without departing from the inventive concept. For example, the positive electrode sheet includes a positive current collector and a positive active material layer covering the surface of the positive current collector.

[0102] There are no particular limitations on the positive electrode current collector, as long as it is conductive and does not cause chemical changes in the battery. Specifically, copper, stainless steel, aluminum, nickel, titanium, or a metal current collector with a surface treated with carbon or other substances can be used.

[0103] The positive current collector can typically have a thickness of 3 μm to 500 μm.

[0104] The positive electrode current collector may have fine irregularities formed on its surface to improve the adhesion of the positive electrode active material. For example, positive electrode current collectors of various shapes such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics can be used.

[0105] The positive electrode active material layer may contain a positive electrode active material.

[0106] The positive electrode active material is a compound that enables reversible insertion and extraction of lithium. Specifically, it may contain a lithium transition metal composite oxide containing lithium and at least one other transition metal selected from the group consisting of nickel, cobalt, manganese and aluminum; preferably, it may contain lithium and transition metals such as nickel, cobalt or manganese.

[0107] More specifically, the lithium transition metal composite oxide can be a lithium manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium cobalt oxide (e.g., LiCoO2, etc.), a lithium nickel oxide (e.g., LiNiO2, etc.), or a lithium nickel manganese oxide (e.g., LiNiIl-yMnyO2 (where 0 < y < 1), LiMn 2-z Ni z O4 (where 0 < z < 2), etc.), lithium nickel cobalt oxides (e.g., LiNi 1-y1 Coy1 O2 (where 0 < y1 < 1), etc.), lithium manganese cobalt oxides (e.g., LiCo) 1-y2 Mn y2 O2 (where 0 < y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < z1 < 2), etc., lithium nickel manganese cobalt oxides (e.g., Li(Ni) p Co q Mn r1 O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1), or lithium nickel cobalt transition metal (M) oxides (e.g., Li(Ni) p2 Co q2 Mn r3 AS2)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, p2, q2, r3, and s2 are each atomic fractions of independent elements, and 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, p2 + q2 + r3 + s2 = 1), etc.), and may contain any one or more of these compounds. Among these, from the perspective of increasing battery capacity and stability, the lithium transition metal composite oxide can be LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni)O2), etc. 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 O2 or LiNi 0.8 Mn 0.1 Co 0.1 O2, or lithium nickel cobalt aluminum oxides (e.g., Li(Ni) 0.8 Co 0.15 Al 0.05 (O2, etc.) etc. When considering the significant improvement effect obtained by controlling the type and content ratio of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide can be Li(Ni) 0.6 Mn 0.2 Co 0.2 O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 O2, Li(Ni) 0.7 Mn 0.15 Co 0.15 O2 or Li(Ni) 0.8Mn 0.1 Co 0.1 O2, etc., and any one of them or a mixture of two or more of them can be used.

[0108] The amount of the positive electrode active material contained in the positive electrode active material layer can be from 80 wt% to 99 wt%, preferably from 92 wt% to 98.5 wt%.

[0109] In addition to containing the aforementioned positive electrode active material, the positive electrode active material layer may also contain a positive electrode binder and / or a positive electrode conductive material.

[0110] The positive electrode adhesive is used to bond the active material, conductive material, and current collector together. Specifically, it may contain at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber, with polyvinylidene fluoride being preferred.

[0111] The amount of positive electrode binder contained in the positive electrode active material layer can be from 1 wt% to 20 wt%, preferably from 1.2 wt% to 10 wt%.

[0112] The conductive material is primarily used to assist and improve the conductivity in secondary batteries, and is not particularly limited, as long as it is conductive without causing chemical changes. Specifically, the conductive material may include graphite, such as natural or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermally cracked carbon black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders, such as fluorocarbon powders, aluminum powders, and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxides; and polyphenylene derivatives, and preferably includes carbon black from the perspective of improving conductivity.

[0113] The specific surface area of ​​the positive electrode conductive material can be 80m². 2 / g to 200m 2 / g, preferably 100m 2 / g to 150m 2 / g.

[0114] The amount of positive electrode conductive material contained in the positive electrode active material layer can be from 1 wt% to 20 wt%, preferably from 1.2 wt% to 10 wt%.

[0115] The thickness of the positive electrode active material layer can be from 30 μm to 400 μm, preferably from 50 μm to 110 μm.

[0116] The positive electrode sheet can be manufactured by coating a positive electrode current collector with a positive electrode slurry containing a positive electrode active material and a selective positive electrode binder, a positive electrode conductive material and a positive electrode slurry forming solvent, followed by drying and rolling.

[0117] The solvent for forming the positive electrode slurry may contain an organic solvent, such as N-methyl-2-pyrrolidone (NMP), and the amount used may be such that a preferred viscosity is obtained when the positive electrode active material is included and positive electrode binder, positive electrode conductive material, etc. are selectively included. For example, the amount of the solvent for forming the positive electrode slurry contained in the positive electrode slurry may be such that the concentration of the solids containing the positive electrode active material and selectively containing the positive electrode binder and positive electrode conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

[0118] This application does not specifically limit the type of electrolyte; any known electrolyte material can be used in this application without departing from the inventive concept. As an illustrative example, the electrolyte can be a liquid electrolyte, a solid electrolyte, or a mixture of a solid electrolyte and a liquid electrolyte.

[0119] When a liquid electrolyte is used, a separator should also be installed in the battery system.

[0120] The primary function of the separator is to separate the negative and positive electrodes and provide a path for lithium ions to move. Any separator can be used without particular limitation, as long as it is a separator commonly used in secondary batteries. In particular, separators with excellent electrolyte wettability and low resistance to ion movement in the electrolyte are preferred. Specifically, porous polymer membranes can be used, for example, porous polymer membranes made from polyolefin polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures having two or more layers. Furthermore, typical porous nonwoven fabrics can be used, such as nonwoven fabrics formed from high-melting-point glass fibers, polyethylene terephthalate fibers, etc. In addition, coated separators containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0121] In addition, the electrolyte used in this invention can be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which can be used in the manufacture of secondary batteries, but is not limited to these.

[0122] Specifically, the electrolyte may contain an organic solvent and a lithium salt.

[0123] Any organic solvent can be used without particular limitation, as long as it can serve as a medium through which ions participating in the electrochemical reactions of the battery can move. Specifically, as said organic solvents, ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone and ε-caprolactone can be used; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R is a straight-chain, branched or cyclic C2-C20 hydrocarbon group and may contain double-bonded aromatic rings or ether bonds); amides such as dimethylformamide; dioxolane, such as 1,3-dioxolane; or sulfolane. Among the solvents described above, carbonate solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constant, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) that can increase the charge / discharge performance of the battery are even more preferred. In this case, when the cyclic carbonate and the linear carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte may be excellent.

[0124] Any compound can be used as the lithium salt without particular limitation, as long as it can provide lithium ions used in lithium secondary batteries. Specifically, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, LiB(C2O4)2, etc., can be used as the lithium salt. The concentration range of the lithium salt can be 0.1-2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has suitable conductivity and viscosity, thus exhibiting excellent performance, and lithium ions can move efficiently.

[0125] In one embodiment, the electrolyte can be a solid electrolyte, and the solid electrolyte particles may comprise one or more polymer components, oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, borate solid electrolytes, nitride solid electrolytes, or hydride solid electrolytes. When polymer particles are used, a lithium salt should be used for verification. In one embodiment, the polymer-based component may comprise one or more polymer materials selected from the group consisting of: polyethylene glycol, polyethylene oxide (PEO), poly(p-phenylene ether) (PPO), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride cohexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), and combinations thereof. It is understood that high ionic conductivity of the polymer material is advantageous to the overall performance of the solid electrolyte material; preferably, the polymer material should have an ionic conductivity greater than or equal to 10⁻⁴ S / cm.

[0126] In one embodiment, the oxide particles may comprise one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides, and perovskite-type ceramics. As an illustrative example, the garnet ceramic may be selected from the group consisting of: Li... 6.5 La3Zr 1.75 Te 0.25 O 12 Li7La3Zr2O 12 Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 Li 6.25 Al 0.25 La3Zr2O 12 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 and combinations thereof. LISICON-type oxides may be selected from the group consisting of: Li 14 Zn(GeO4)4, Li 3+x (P 1-x Si x O4 (where 0 < x < 1), Li3+x Ge x V 1-x O4 (where 0 < x < 1) and combinations thereof. NASICON-type oxides can be defined by LiMM′(PO4)3, where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. Preferably, NASICON-type oxides can be selected from the group consisting of: Li 1+x Al x Ge 2-x (PO4)3(LAGP) (where 0 ≤ x ≤ 2), Li 1+x Al x Ti 2-x (PO4)3(LATP) (where 0 ≤ x ≤ 2), Li 1+x Y x Zr 2-x (PO4)3(LYZP) (where 0≤x≤2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3, LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3, and combinations thereof. One or more perovskite ceramics may be selected from the group consisting of: Li 3.3 La 0.53 TiO3, LiSr 1.65 Zr 1.3 Ta 1.7 O9、Li 2x-y Sr 1-x Ta y Zr 1-y O3 (where x = 0.75y and 0.60 < y < 0.75), Li 3 / 8 Sr 7 / 16 Nb 3 / 4Zr 1 / 4 O3, Li 3x La(2 / 3-x)TiO3 (where 0 < x < 0.25) and combinations thereof. Preferably, one or more oxide-based materials may have an ionic conductivity greater than or equal to about 10⁻⁵ S / cm to less than or equal to about 10⁻¹ S / cm.

[0127] Sulfide solid electrolytes are selected from one or more sulfide-based materials including the group consisting of: Li₂S-P₂S₅, Li₂S-P₂S₅-MSx (where M is Si, Ge, and Sn and 0 ≤ x ≤ 2), Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O0.3 Li 9.6 P3S 12 Li7P3S 11 Li9P3S9O3, Li 10.35 Si 1.35 P 1.65 S 12 Li 9.81 Sn 0.81 P 2.19 S 12 Li 10 (Si 0.5 Ge 0.5 P2S 12 Li (Ge 0.5 Sn 0.5 P2S 12 Li(Si) 0.5 Sn 0.5 PS 12 Li 10 GeP2S 12 (LGPS), Li6PS5X (where X is Cl, Br, or I), Li7P2S8I, Li 10.35 Ge 1.35 P 1.65 S 12 Li 3.25 Ge 0.25 P 0.75 S4, Li 10 SnP2S 12 Li 10 SiP2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 C 10.3 (1-x)P2S 5-x Li₂S (where 0.5 ≤ x ≤ 0.7) and their combinations.

[0128] Halogen solid electrolytes may include one or more halide-based materials selected from the group consisting of: Li₂CdCl₄, Li₂MgCl₄, Li₂CdI₄, Li₂ZnI₄, Li₃OCl, LiI, Li₅ZnI₄, and Li₃OCl. 1-x Br x (where 0 < x < 1) and their combinations.

[0129] The borate solid electrolyte is selected from one or more borate-based materials including the group consisting of Li2B4O7, Li2O-(B2O3)-(P2O5), and combinations thereof.

[0130] The nitride solid electrolyte may be selected from one or more nitride-based materials including the group consisting of Li3N, Li7PN4, LiSi2N3, LiPON, and combinations thereof.

[0131] The hydride solid electrolyte may be selected from one or more hydride-based materials including the group consisting of: Li3AlH6, LiBH4, LiBH4-LiX (where X is one of Cl, Br and I), LiNH2, Li2NH, LiBH4-LiNH2 and combinations thereof.

[0132] As a particular implementation, the solid electrolyte can be a quasi-solid electrolyte comprising a mixture of the non-aqueous liquid electrolyte solution and the solid electrolyte system detailed above, for example, including one or more ionic liquids and one or more metal oxide particles (such as aluminum oxide (Al2O3) and / or silicon dioxide (SiO2)).

[0133] The embodiments of the present invention will be described in more detail below with reference to examples. However, the embodiments of the present invention are not limited to these examples.

[0134] Example 1

[0135] Sodium carboxymethyl cellulose (CMC) was carbonized in a muffle furnace at a temperature of 150°C for 3 hours. The resulting conductive adhesive, sodium carboxymethyl cellulose (CMC), was obtained after carbonization.

[0136] Take 1g of polyacrylic acid (molecular weight: 300,000) and 1g of conductive adhesive sodium carboxymethyl cellulose (CMC) and dry them in a drying oven until constant weight. Then, transfer the dried polyacrylic acid and conductive adhesive sodium carboxymethyl cellulose (CMC) to a mixer for dry mixing. Next, add the dry-mixed polyacrylic acid and conductive adhesive sodium carboxymethyl cellulose (CMC) to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0137] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0138] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0139] Example 2

[0140] Sodium carboxymethyl cellulose (CMC) was carbonized in a muffle furnace at a temperature of 250°C for 3 hours. The resulting conductive adhesive, sodium carboxymethyl cellulose (CMC), was obtained after carbonization.

[0141] Take 1g of polyacrylic acid (molecular weight: 300,000) and 1g of conductive adhesive sodium carboxymethyl cellulose (CMC) and dry them in a drying oven until constant weight. Then, transfer the dried polyacrylic acid and conductive adhesive sodium carboxymethyl cellulose (CMC) to a mixer for dry mixing. Next, add the dry-mixed polyacrylic acid and conductive adhesive sodium carboxymethyl cellulose (CMC) to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0142] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0143] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0144] Example 3

[0145] Sodium alginate was carbonized in a muffle furnace at a temperature of 250°C for 7 hours. The resulting conductive adhesive, sodium alginate, was obtained after carbonization.

[0146] Take 1g of lithium-ionized polyacrylic acid (molecular weight: 500,000) and 1g of conductive adhesive sodium alginate and dry them in a drying oven until constant weight. Then, transfer the lithium-ionized polyacrylic acid and conductive adhesive sodium alginate to a mixer for dry mixing. Next, add the dry-mixed lithium-ionized polyacrylic acid and conductive adhesive sodium alginate to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0147] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0148] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0149] Example 4

[0150] Sodium alginate was carbonized in a muffle furnace at a temperature of 250°C for 8 hours. The resulting conductive adhesive, konjac gum, was obtained after carbonization.

[0151] Take 1g of lithium-ionized polyacrylic acid (molecular weight: 120000) and 1g of conductive adhesive sodium alginate and dry them in a drying oven until constant weight. Then, transfer the lithium-ionized polyacrylic acid and conductive adhesive sodium alginate to a mixer for dry mixing. Next, add the dry-mixed lithium-ionized polyacrylic acid and conductive adhesive sodium alginate to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0152] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0153] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0154] Example 5

[0155] Sodium alginate was carbonized in a muffle furnace at a temperature of 250°C for 4 hours. The resulting conductive adhesive, k-carrageenan, was obtained after carbonization.

[0156] Take 0.5g of high molecular weight lithium-ionized polyacrylic acid (molecular weight: 160,000), 0.5g of low molecular weight lithium-ionized polyacrylate (molecular weight: 300,000), and 1g of conductive adhesive sodium alginate and dry them in a drying oven until constant weight. Then, transfer the dried high molecular weight lithium-ionized polyacrylic acid, low molecular weight lithium-ionized polyacrylate, and conductive adhesive sodium alginate to a mixer for dry mixing. Next, add the dry-mixed high molecular weight lithium-ionized polyacrylic acid, low molecular weight lithium-ionized polyacrylate, and conductive adhesive sodium alginate to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0157] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0158] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0159] Example 6

[0160] Sodium alginate adhesive was placed in a muffle furnace for carbonization. The carbonization temperature was set to 250℃ and the carbonization time was 5 hours. After carbonization, guar glue, a conductive adhesive, was obtained.

[0161] Take 0.5g of high molecular weight lithium-ionized polyacrylic acid (molecular weight: 160,000), 0.5g of low molecular weight lithium-ionized polyacrylate (molecular weight: 300,000), and 1g of conductive adhesive sodium alginate and dry them in a drying oven until constant weight. Then, transfer the dried high molecular weight lithium-ionized polyacrylic acid, low molecular weight lithium-ionized polyacrylate, and conductive adhesive sodium alginate to a mixer for dry mixing. Next, add the dry-mixed high molecular weight lithium-ionized polyacrylic acid, low molecular weight lithium-ionized polyacrylate, and conductive adhesive sodium alginate to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0162] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0163] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0164] Comparative Example 1

[0165] Sodium carboxymethyl cellulose (CMC) was carbonized in a muffle furnace at a temperature of 250°C for 3 hours. The resulting conductive adhesive, sodium carboxymethyl cellulose (CMC), was obtained after carbonization.

[0166] Take 2g of conductive adhesive sodium carboxymethyl cellulose (CMC) and dry it in a drying oven until constant weight. Then add the dried conductive adhesive sodium carboxymethyl cellulose (CMC) to 150g of deionized water and stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0167] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0168] The negative electrode is assembled into a button cell, and the cycle efficiency is tested after the button cell is cycled 100 times.

[0169] Comparative Example 2

[0170] Take 2g of polyacrylic acid and add it to 150g of deionized water. Stir at high speed to prepare a mixed solution to obtain the negative electrode adhesive.

[0171] Following the traditional wet homogenization process, 91g of negative electrode material and 2g of acetylene black were added to 60g of negative electrode binder. After stirring for 3 hours, deionized water was added to adjust the viscosity of the slurry to 3500cps. The slurry was then coated onto the surface of a copper foil and finally dried at 90℃ to obtain the negative electrode sheet.

[0172] Assemble the negative electrode into a button cell. After 100 cycles, test the cycle efficiency. Button cell installation method.

[0173] In a solid-state battery test mold with a diameter of 10 mm, a 50 μm LLZO solid electrolyte membrane is first added. 10 mg of positive electrode mixture is spread evenly on one side of the solid electrolyte membrane and pressed under a pressure of 400 MPa. Then, the battery mold is disassembled, and a negative electrode sheet with a thickness of 500 μm is attached to the other side of the composite electrolyte. The mold is then assembled, thus obtaining a solid-state battery.

[0174] The coin cell cycle test method involves subjecting the prepared battery to cycle testing using a Blue Electric test system. The voltage range is 3-4.3V, and the test temperature is 25℃. The first two cycles use a low rate of 0.05C, and from the third cycle onwards, the rate is adjusted to 0.3C. The capacity after 100 cycles is recorded. The cycle efficiency is obtained by dividing the capacity of the 100th cycle by the capacity of the 3rd cycle, which is used to evaluate the interfacial stability of the electrolyte system. The test results are shown in Table 1.

[0175] Table 1. Test results of the negative electrode sheets prepared in Examples 1-6 and Comparative Examples 1-2

[0176]

[0177]

[0178] As can be seen from the above, the embodiments of this application provide a negative electrode binder, a negative electrode sheet, a lithium battery and its preparation method, which can effectively solve the problem of volume expansion caused by silicon-based negative electrode materials as negative electrode active materials.

[0179] The foregoing has provided a detailed description of the negative electrode adhesive, negative electrode sheet, lithium-ion battery, and its preparation method. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a negative electrode adhesive, characterized in that, The method includes: A conductive adhesive is obtained by carbonizing the first adhesive, wherein the first adhesive is a polymer rich in at least one of hydroxyl, carboxyl, and amino groups; The negative electrode adhesive is obtained by mixing the second adhesive and the conductive adhesive, wherein the second adhesive comprises polyacrylic acid; wherein... The first adhesive includes at least one of sodium carboxymethyl cellulose, sodium alginate, guar gum, konjac gum, gelatin, and k-carrageenan; The carbonization temperature for the first adhesive is 120-450℃, and the carbonization time is 0.5-16h.

2. A negative electrode adhesive, characterized in that, The negative electrode adhesive is prepared according to the method described in claim 1.

3. A method for preparing a negative electrode sheet, characterized in that, The method includes: A silicon-based anode material, an anode conductive agent, the anode binder as described in claim 2, and a solvent are mixed evenly to obtain an anode slurry. The negative electrode slurry is coated onto the surface of the negative electrode current collector and then dried to obtain the negative electrode sheet; wherein... The mass of the silicon-based negative electrode material is 85%-96% of the mass of the negative electrode sheet, the mass of the negative electrode conductive agent is 0.2%-5% of the mass of the negative electrode sheet, and the mass of the negative electrode binder is 1%-11.8% of the mass of the negative electrode sheet.

4. The method for preparing the negative electrode sheet according to claim 3, characterized in that, The negative electrode conductive agent includes at least one of acetylene black, carbon black, Ketjen black, carbon nanotubes, and carbon fibers.

5. A negative electrode sheet, characterized in that, The negative electrode sheet is prepared by the method of any one of claims 3 or 4.

6. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode as described in claim 5, a separator, and an electrolyte.

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