Positive electrode sheet and preparation method therefor, and battery

Abstract

The present invention provides a positive electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer comprises a positive electrode active material, a conductive agent, and binders; the binders include a type A binder and a type B binder; the type A binder comprises a first binder; the type B binder comprises at least one of a second binder and a third binder; and the contents of the first binder, the second binder, and the third binder are α, β, and γ, respectively, and α, β, and γ satisfy: 1.0%≤α+β+γ≤3.0%, 0%<α<3.0%, 0%≤β≤1.0%, and 0%≤γ≤2.0%. In the present application, by controlling the mixing ratio of multiple binders, the solid content of a positive electrode mixture is increased, and the usage amount of a solvent is reduced, which facilitates subsequent extrusion forming of a film and effective lamination and bonding with the current collector, so that the positive electrode mixture can have good softness and tensile properties while it is ensured that the positive electrode active material layer can be laminated and bonded with the positive electrode current collector, thereby ensuring the manufacturability of subsequent extrusion and thinning, and a lamination process.

Description

A positive electrode sheet and its preparation method, and a battery Technical Field

[0001] This invention relates to the field of battery technology, specifically to a positive electrode sheet and its preparation method, and a battery. Background Technology

[0002] With the rapid increase in global demand for sustainable energy, secondary batteries, as a key component of energy storage solutions, have become a focus of research and development in terms of performance optimization and cost control. Existing secondary battery slurry preparation typically employs a wet process, requiring large amounts of solvent for stirring and dispersion, followed by drying to remove the solvent. This process not only consumes significant energy but also increases manufacturing costs. On the other hand, while dry electrode processes avoid the use of solvents, achieving ideal particle dispersion during solid-phase formulation is difficult. Furthermore, when the positive electrode active material is nanoparticles, such as lithium iron phosphate, dry electrode processes still present processing challenges, affecting battery performance. Therefore, overcoming these technical problems and shortcomings is a crucial issue that needs to be addressed. Summary of the Invention

[0003] To address the problem of unsatisfactory particle dispersion in dry electrode manufacturing processes, this invention provides a positive electrode sheet, its preparation method, and a battery.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] The first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising a positive active material, a conductive agent and a binder, the binder comprising a type A binder and a type B binder, the type A binder comprising a first binder, and the type B binder comprising at least one of a second binder and a third binder;

[0006] With the total mass of the positive electrode active material layer as 100%, the content of the first binder is α, the content of the second binder is β, and the content of the third binder is γ, and α, β, and γ satisfy the following relationship: 1.0% ≤ α + β + γ ≤ 3.0%, where 0% < α < 3.0%, 0% ≤ β ≤ 1.0%, and 0% ≤ γ ≤ 2.0%.

[0007] Optionally, the positive electrode active material, the conductive agent, and the binder are mixed to form a positive electrode mixture, and the positive electrode mixture forms the positive electrode active material layer on the surface of the positive electrode current collector. The solid content of the positive electrode mixture is X, and the value of X is in the range of 70% ≤ X < 100%.

[0008] Optionally, before forming the positive electrode mixture, the type A binder is prepared by mixing and fusing the first binder with a solvent.

[0009] Optionally, the positive electrode mixture is extruded to form a membrane, and the membrane is combined with the positive electrode current collector to obtain the positive electrode sheet. The tensile strength of the membrane is S MPa, and the value of S is in the range of 0.1 MPa ≤ S.

[0010] Optionally, X satisfies the following relationship with α, β, and γ: 70% ≤ (0.75α + 0.83β + 0.79γ) / (α + β + γ) ≤ X < 100%.

[0011] Optionally, S and α, β, γ satisfy the relationship: 0.1≤6α+3β+110γ≤S.

[0012] Optionally, the first adhesive includes one or more of rubber, modified rubber, polyvinylidene fluoride, modified polyvinylidene fluoride, polyimide, modified polyimide, polypropylene, modified polypropylene, polyacrylic acid, and modified polyacrylic acid.

[0013] Optionally, the second adhesive includes one or more of polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl butyral, modified polyvinyl butyral, polyacrylonitrile, and modified polyacrylonitrile.

[0014] Optionally, the third adhesive includes one or more of polytetrafluoroethylene and its modified polymers.

[0015] Optionally, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich manganese-based materials.

[0016] Or one or more of the following types of layered sodium cathodes and Prussian blue cathodes: sodium ferric sulfate, sodium ferric phosphate, sodium ferric pyrophosphate, sodium ferric pyrophosphate, sodium vanadium phosphate, sodium copper iron manganese oxide, sodium iron nickel manganese oxide, etc.

[0017] Optionally, the conductive agent includes one or more of the following: carbon black, acetylene black, Ketjen black, graphene microspheres, three-dimensional conductive metal-organic frameworks, porous spherical carbon, conductive nanotubes, nanofibers, graphene, and graphite flakes.

[0018] Optionally, the total mass of the positive electrode active material layer is 100%, the mass percentage of the positive electrode active material is 94.5% to 98.5%, the mass percentage of the conductive agent is 0.5% to 2.5%, and the mass percentage of the binder is 1.0% to 3.0%.

[0019] A second aspect of the present invention provides a method for preparing a positive electrode sheet, comprising the following steps:

[0020] (1) Positive electrode mixture pre-preparation: mix the formula amount of positive electrode active material, conductive agent and B type binder uniformly;

[0021] (2) Positive electrode mixture preparation: add A type binder to the mixture in step (1) and mix uniformly to obtain a positive electrode mixture; wherein the A type binder is prepared by mixing the first binder with a solvent;

[0022] (3) The positive electrode mixture in step (2) is extruded through a die to obtain a self-supporting film, and the film is compounded with a positive electrode current collector to obtain a positive electrode sheet.

[0023] Optionally, in step (3), the mass percentage of the solvent in the total mass of the positive electrode mixture is X1, and the value of X1 is in the range of 0 < X ≤ 30%.

[0024] The third aspect of the present application provides a battery comprising a negative electrode sheet, a separator and a positive electrode sheet as described above or a positive electrode sheet prepared by the preparation method of the positive electrode sheet as described above.

[0025] According to the positive electrode sheet provided by the present application, the binder is prepared by mixing multiple binders, and by controlling the mixing ratio of the multiple binders, the solid content of the positive electrode mixture can be increased, the amount of solvent used can be reduced, which is conducive to subsequent extrusion into a film and effective compounding and bonding with the current collector; while ensuring that the positive electrode active material layer can be compounded and bonded with the positive electrode current collector, the slurry has good softness and tensile properties, ensuring the manufacturability of subsequent extrusion, thinning and compounding processes. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0027] In the following examples, the test methods used are conventional methods unless otherwise specified; the materials, reagents, etc. used are commercially available reagents and materials unless otherwise specified.

[0028] The first aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, the positive active material layer comprising a positive active material, a conductive agent and a binder, wherein the binder is a type A binder and a type B binder, the type A binder comprising a first binder and the type B binder comprising at least one of a second binder and a third binder;

[0029] With the total mass of the positive electrode active material layer as 100%, the content of the first binder is α, the content of the second binder is β, and the content of the third binder is γ, and α, β, and γ satisfy the following relationship: 1.0% ≤ α + β + γ ≤ 3.0%, where 0% < α < 3.0%, 0% ≤ β ≤ 1.0%, and 0% ≤ γ ≤ 2.0%.

[0030] Specifically, the value range of α+β+γ is any single value or a range of any two values ​​selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%. In a preferred embodiment, the value range of α+β+γ is 1%-2%.

[0031] When the value of α+β+γ is in the range of 1.0%-3.0%, the positive electrode active material and the conductive agent can be effectively bonded together. When the value of α+β+γ is less than 1.0%, the cohesion between the positive electrode active material and the conductive agent is insufficient, resulting in poor composite effect between the positive electrode active material layer and the positive electrode current collector. When the value of α+β+γ is greater than 3.0%, the energy density of the battery will be affected because the binder does not provide electrochemical activity. On the other hand, as the binder content increases, the viscosity of the mixture will increase, which will affect the extrusion process of the membrane. Higher extrusion pressure is required, or further solvents need to be added to reduce the solid content. However, excessive solvents will lead to a longer drying time to remove the solvent, increasing the manufacturing cost.

[0032] Specifically, the content of the first adhesive is any one value or a range of any two values ​​selected from 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%; in a preferred embodiment, the content of the first adhesive is 1%-2%.

[0033] When the content of the first binder is 0% (excluding) to 3.0%, it can effectively bond the positive electrode active material and the conductive agent together; when the content of the first binder is greater than 3.0%, it will affect the energy density of the battery.

[0034] Specifically, the content of the second adhesive is any one value or a range of any two values ​​selected from 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%; in a preferred embodiment, the content of the second adhesive is 0.2%-0.5%.

[0035] When the content of the second binder is 0%-1.0%, it can increase the flexibility of the positive electrode active material and effectively bond the positive electrode active material and the conductive agent together; when the content of the second binder is greater than 1.0%, it will lead to an increase in battery impedance and affect the dynamic performance of the battery.

[0036] Specifically, the content of the third adhesive is any one value or a range of any two values ​​selected from 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%; in a preferred embodiment, the content of the third adhesive is 0.2%-1%.

[0037] When the content of the third binder is 0%-2.0%, it can increase the tensile strength of the positive electrode active material and effectively bond the positive electrode active material and the conductive agent together. When the content of the third binder is greater than 2.0%, it will cause the material after mixing the positive electrode active material, conductive agent and type B binder to a certain extent to agglomerate. This will affect the stability of the addition of type A binder during the generation process and have a negative impact on the consistency of the extruded film.

[0038] The binder in this application is prepared by mixing type A binder and type B binder. By controlling the mixing ratio of various binders, the solid content of the positive electrode mixture can be increased and the amount of solvent used can be reduced, which is beneficial to the subsequent extrusion into film and effective composite bonding with the current collector. While ensuring that the positive electrode active material layer can be compositely bonded with the positive electrode current collector, the slurry has good softness and tensile properties, ensuring the manufacturability of subsequent extrusion, thinning and composite processes.

[0039] In one embodiment, the positive electrode active material, the conductive agent, and the binder are mixed to form a positive electrode mixture. The positive electrode mixture forms the positive electrode active material layer on the surface of the positive electrode current collector. The solid content of the positive electrode mixture is X, and the value of X ranges from 70% to X < 100%.

[0040] Specifically, the value of X is any one point or a range of any two points selected from 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%; in a preferred embodiment, the value of X is 70%-95%.

[0041] This application uses a semi-dry method to prepare the membrane, where the value of X is in the range of 70% ≤ X < 100%. This method ensures uniform dispersion of the solid phase ingredients during mixing and reduces the subsequent drying time of the electrode, saving energy and manufacturing costs. When the value of X is less than 70%, the extruded membrane is difficult to form and cannot be effectively combined with the positive electrode current collector. At the same time, a low solid content requires an increase in the amount of solvent used and the energy consumption for baking, thus increasing manufacturing costs.

[0042] In one embodiment, prior to the formation of the positive electrode mixture, the type A binder is prepared by mixing and fusing the first binder with a solvent.

[0043] Specifically, the solvent includes one or more of N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylamide, tetrahydrofuran, acetone, perfluorohexanone, acetic acid, ethanol, ethyl acetate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. At room temperature, the first binder is solid. During use, the first binder is mixed with the solvent to dissolve the first binder in the solvent, resulting in a liquid Class A binder. The Class A binder mainly serves as a binder, ensuring that the positive electrode active material layer can be firmly bonded to the positive electrode current collector.

[0044] In one embodiment, the positive electrode mixture is extruded to form a membrane, and the membrane is combined with the positive electrode current collector to obtain the positive electrode sheet. The tensile strength of the membrane is S MPa, and the value of S is in the range of 0.1 MPa ≤ S.

[0045] In a preferred embodiment, the value of S is in the range of 0.5 MPa ≤ S. When the value of S is in the range of 0.5 MPa ≤ S, the membrane can achieve self-support without other support carriers and will not break. It can be thinned first and then combined with the current collector. When the value of S is in the range of 0.1 MPa ≤ S < 0.5 MPa, the membrane cannot achieve self-support. The extruded membrane needs to be combined with the current collector and then subjected to subsequent rolling thinning. When the tensile strength of the membrane is less than 0.1 MPa, the tensile strength of the extruded membrane is too poor to achieve the traction function. In this case, the positive electrode mixture needs to be directly extruded, coated or cast on the surface of the positive electrode current collector, which is the existing conventional wet process.

[0046] In one embodiment, X satisfies the following relationship with α, β, and γ: 70% ≤ (0.75α + 0.83β + 0.79γ) / (α + β + γ) ≤ X < 100%.

[0047] When the content of the first binder α, the content of the second binder β, the content of the third binder γ, and the solid content X of the positive electrode mixture satisfy 70% ≤ (0.75α + 0.83β + 0.79γ) / (α + β + γ) ≤ X < 100%, a mixture with a higher solid content can be prepared by combining and setting different proportions of different binders, reducing the amount of solvent used in the manufacturing process, thereby reducing manufacturing energy consumption. At the same time, the mixture with a higher solid content has better softness, which is beneficial to the subsequent extrusion process.

[0048] In one embodiment, S and α, β, γ satisfy the relationship: 0.1≤6α+3β+110γ≤S.

[0049] When the content of the first binder α, the content of the second binder β, the content of the third binder γ, and the tensile strength S of the film satisfy 0.1≤6α+3β+110γ≤SS, a mixture with a high solid content can be prepared by combining and setting different proportions of different binders. At the same time, the tensile strength of the extruded film can be controlled by adjusting the binder, ensuring that the obtained film has good processing and manufacturing performance.

[0050] In one embodiment, the first adhesive comprises one or more of rubber, modified rubber, polyvinylidene fluoride, modified polyvinylidene fluoride, polyimide, modified polyimide, polypropylene, modified polypropylene, polyacrylic acid, and modified polyacrylic acid.

[0051] The first type of adhesive is in liquid form and mainly serves as a binder, ensuring that the positive electrode active material layer can be firmly bonded to the positive electrode current collector.

[0052] In one embodiment, the second adhesive comprises one or more of polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl butyral, modified polyvinyl butyral, polyacrylonitrile, and modified polyacrylonitrile.

[0053] The second type of binder mainly increases the flexibility of the slurry, improves the processing characteristics of the positive electrode active material layer, and also increases the bonding strength between the positive electrode active material layer and the positive electrode current collector.

[0054] In one embodiment, the third adhesive comprises one or more of polytetrafluoroethylene and its modified polymers.

[0055] The third type of adhesive mainly increases the tensile properties of the positive electrode active material layer, improves the processing characteristics of the positive electrode active material layer, and also increases the bonding strength between the positive electrode active material layer and the positive electrode current collector.

[0056] In one embodiment, the positive electrode active material includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich manganese-based materials.

[0057] Or one or more of the following types of layered sodium cathodes and Prussian blue cathodes: sodium ferric sulfate, sodium ferric phosphate, sodium ferric pyrophosphate, sodium ferric pyrophosphate, sodium vanadium phosphate, sodium copper iron manganese oxide, sodium iron nickel manganese oxide, etc.

[0058] The positive electrode sheet of the present invention can be applied to lithium-ion batteries and sodium-ion batteries, and further, it can also be applied to other secondary batteries.

[0059] In one embodiment, the conductive agent includes one or more of the following: carbon black, acetylene black, Ketjen black, graphene microspheres, three-dimensional conductive metal-organic frameworks, porous spherical carbon, conductive nanotubes, nanofibers, graphene, and graphite flakes.

[0060] In one embodiment, the total mass of the positive electrode active material layer is 100%, the mass percentage of the positive electrode active material is 94.5% to 98.5%, the mass percentage of the conductive agent is 0.5% to 2.5%, and the mass percentage of the binder is 1.0% to 3.0%.

[0061] Specifically, the mass percentage content of the positive electrode active material is any one value or a range of any two values ​​selected from 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, or 98.5%; in a preferred embodiment, the mass percentage content of the positive electrode active material is 96%-97%.

[0062] Specifically, the mass percentage content of the conductive agent is any one value or a range of any two values ​​selected from 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%; in a preferred embodiment, the mass percentage content of the conductive agent is 1%-2%.

[0063] Specifically, the mass percentage of the adhesive is any one value or a range of any two values ​​selected from 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, and 3%; in a preferred embodiment, the mass percentage of the adhesive is 1.5%-2.5%.

[0064] A second aspect of the present invention provides a method for preparing a positive electrode sheet, comprising the following steps:

[0065] (1) Pre-preparation of positive electrode mixture: Mix the positive electrode active material, conductive agent and type B binder in the specified amounts evenly;

[0066] (2) Preparation of positive electrode mixture: Add type A binder to the mixture in step (1) and mix evenly to obtain positive electrode mixture; wherein, type A binder is prepared by mixing and fusing the first binder with a solvent;

[0067] (3) The positive electrode mixture in step (2) is extruded through a die to obtain a self-supporting membrane, and the membrane is combined with the positive electrode current collector to obtain a positive electrode sheet.

[0068] Specifically, the positive electrode active material, conductive agent, and Class B binder solid particles are mixed, which is beneficial to the uniformity of the distribution of the solid particle binder, positive electrode active material, and conductive agent. Then, Class A binder, which is in the form of a gel, is added and mixed with the positive electrode active material and conductive agent to form a clump-shaped positive electrode mixture. The positive electrode mixture is directly extruded through the die head of an extrusion die to obtain a membrane with a thickness of 100-500 μm. The membrane is then combined with the positive electrode current collector to obtain the positive electrode sheet.

[0069] By adding at least one of the third and second binders, the flexibility and tensile properties of the positive electrode mixture can be increased, the processing characteristics of the positive electrode active material layer can be improved, and the bonding strength between the membrane and the positive electrode current collector can also be increased.

[0070] The present invention uses a type A binder mixed with positive electrode active material, conductive agent and type B binder to form a clump-like positive electrode mixture, which is a semi-dry electrode preparation method. The present application uses the above method to make the positive electrode active material and conductive agent uniformly distributed, thereby improving the performance of the battery.

[0071] In one embodiment, in step (3), the total mass of the positive electrode mixture is 100%, and the mass percentage of the solvent is X1, wherein the value of X1 is in the range of 0 < X ​​≤ 30%.

[0072] Specifically, the value of X1 is any one point or a range of any two points selected from 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%; in a preferred embodiment, the value of X1 is 5%-30%.

[0073] This application uses a semi-dry method to prepare the membrane, where the value of X1 is in the range of 0 < X ​​≤ 30%. This ensures uniform dispersion of the solid phase ingredients during mixing and reduces the subsequent drying time of the electrode, saving energy and manufacturing costs. When the value of X1 is greater than 30%, the extruded membrane is difficult to form and cannot be effectively combined with the positive electrode current collector. At the same time, a low solid content requires an increase in the amount of solvent used and the energy consumption for baking, thus increasing manufacturing costs.

[0074] A third aspect of the present invention provides a battery comprising a negative electrode, a separator, and a positive electrode as described above or a positive electrode prepared by the method described above for preparing the positive electrode.

[0075] In one embodiment, the negative electrode sheet includes a negative electrode active material, which includes one or more of the following: graphite negative electrode material, hard carbon negative electrode material, soft carbon negative electrode material, silicon-oxygen negative electrode material, silicon-carbon negative electrode material, silicon negative electrode material, tin negative electrode material, tin oxide negative electrode material, tin alloy negative electrode material (Sn-Fe, Sn-Co, Sn-Cu, etc.), lithium metal negative electrode material, lithium alloy negative electrode material (Li-Ag, Li-Al, Li-Sn, Li-Mg, Li-Zn, Li-In, Li-Ga, etc.), and lithium-free negative electrode material.

[0076] The electrolyte of this invention can be used in high-voltage battery systems, matching high-voltage ternary cathodes and lithium-rich manganese cathodes, as well as graphite anodes, silicon-carbon anodes, silicon-oxygen anodes, and lithium metal anodes. It can be used to manufacture liquid, semi-solid stacked, wound, or cylindrical batteries. The electrolyte of this invention provides a stable cycle foundation for battery systems under high voltage conditions and improves the safety characteristics of batteries.

[0077] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, a conductive agent, a binder, and a thickener.

[0078] In some embodiments, the negative electrode conductive agent includes one or more of graphite, superconducting carbon, acetylene black, carbon black, carbon nanotubes, graphene, carbon nanofibers, metal powder, metal fibers, and polyphenylene derivatives.

[0079] In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, and polymethacrylic acid.

[0080] In some embodiments, the thickener includes one or more of sodium alginate, sodium carboxymethyl cellulose, and carboxymethyl chitosan.

[0081] In some embodiments, the mass percentage of each component in the negative electrode active material layer is: 96%-97% negative electrode active material, 0.5%-1.5% conductive agent, 1%-2% binder and 0.5%-1.5% thickener.

[0082] The negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes one or more of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0083] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically formed by coating a negative electrode slurry, consisting of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and any other components, onto a negative electrode current collector, followed by drying and cold pressing. The solvent can be an aqueous solvent, but is not limited to it.

[0084] Specifically, the diaphragm can be selected from one or more materials such as polypropylene (PP), polyethylene (PE), PP / PE / PP composite membrane, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ceramic diaphragm, ceramic polyamide (PI), aramid (AF), and non-woven fabric.

[0085] In a preferred embodiment, the battery is manufactured by comprising the following steps:

[0086] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrode and separator are then placed into a pre-formed aluminum-plastic film bag using a stacking method. The electrolyte, gel electrolyte, or solid electrolyte prepared above is injected into the baked and dried cell, and the battery is obtained after vacuum sealing, settling, and formation processes.

[0087] The beneficial effects of the present invention will be further illustrated below with reference to the embodiments.

[0088] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention is further described in detail below with reference to embodiments. However, it should be understood that the embodiments of this invention are merely for illustrative purposes and not for limiting the invention, and the embodiments are not limited to those given in the specification. Unless otherwise specified, specific experimental or operational conditions in the embodiments were prepared under conventional conditions or according to the conditions recommended by the material supplier.

[0089] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0090] In the following embodiments, the reagents, materials and instruments used, unless otherwise specified, are commercially available or can be obtained through synthesis methods known in the art.

[0091] Table 1 shows the design of the positive electrode sheets for Examples 1-11 and Comparative Examples 1-10;

[0092] Example 1

[0093] This embodiment illustrates the positive electrode sheet and battery disclosed in this invention; it includes the following operational steps:

[0094] Production of positive electrode sheets:

[0095] Lithium iron phosphate (CFP), carbon black (CSP), rubber (first binder), and polyvinyl alcohol (PVA) (second binder) were weighed in a mass ratio of 97.8:1.2:0.5:0.5. The CFP, CSP, and PVA were then mixed thoroughly. Finally, type A binder rubber was added to form a homogeneous CFP mixture. This mixture was extruded through a die to obtain a self-supporting membrane. The membrane was then combined with a CFP current collector to obtain the CFP electrode sheet.

[0096] Production of negative electrode plates:

[0097] Graphite anode material, conductive agent carbon black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose are mixed in a mass ratio of 95.4:1.5:1.6:1.5. The mixture is thoroughly stirred in a deionized water solvent to form a uniform anode slurry. This slurry is coated onto at least one side of a copper foil current collector, and after drying, rolling, and die-cutting, a suitable anode sheet is obtained.

[0098] Diaphragm fabrication:

[0099] PE porous polymer film is used as the membrane substrate;

[0100] Battery making:

[0101] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The positive electrode, separator, and negative electrode are repeatedly stacked to form the electrode core. The stacked electrode core is then placed in a pre-formed aluminum-plastic film bag. The electrolyte prepared above is injected into the baked and dried battery core. After vacuum sealing, settling, and formation processes, a battery with a capacity of 1.2Ah is obtained.

[0102] Example 2-11

[0103] Examples 2-11 illustrate the positive electrode and battery disclosed in this invention, including most of the operating steps in Example 1, with the following differences:

[0104] The positive electrode and the various components and contents in the battery are shown in Table 1.

[0105] Comparative Examples 1-10

[0106] Comparative Examples 1-10 are used to illustrate the positive electrode and battery disclosed in this invention, including most of the operating steps in Example 1, the difference being:

[0107] The positive electrode and the various components and contents in the battery are shown in Table 1.

[0108] Performance testing

[0109] The following performance tests were performed on the batteries prepared in Examples 1-11 and Comparative Examples 1-10:

[0110] (1) Discharge rate test:

[0111] Charging: At 25±2℃, charge the battery at a constant current rate of 0.5C to 3.65V, then switch to constant voltage charging. The cutoff condition is that the current is less than 0.05C.

[0112] Resting: 25±2℃, rest for 10 minutes after charging is complete;

[0113] Discharge: 25±2℃, then discharge at a constant current of 0.5C to 2.5V, and record the discharge capacity as C0;

[0114] Resting: 25±2℃, rest for 10 minutes after discharge;

[0115] Charging: At 25±2℃, charge the battery again at a constant current rate of 0.5C until it reaches 3.65V, then switch to constant voltage charging. The cutoff condition is that the current is less than 0.05C.

[0116] Resting: 25±2℃, rest for 10 minutes after charging is complete;

[0117] Discharge: 25±2℃, then discharge at a constant current of 2.0C to 2.5V, and record the discharge capacity as C1;

[0118] Discharge ratio: C1 / C0*100% is recorded as the 2C discharge ratio.

[0119] (2) DC resistance test:

[0120] To adjust to 50% SOC: At 25±2℃, charge the battery at a constant current rate of 0.5C to 3.65V, then switch to constant voltage charging. The cutoff condition is that the current is less than 0.05C. After charging is completed, let it rest for 10 minutes, and then discharge it at a constant current rate of 0.5C to 50% SOC.

[0121] DC resistance test: Let stand for 60 minutes, record the end voltage V1, then discharge with a current of 2C (2.4A) for 30 seconds, and record the end voltage V2.

[0122] DC internal resistance: (V1-V2) / 2.4*1000 is recorded as the measured DC internal resistance value;

[0123] (3) Cyclic performance test:

[0124] Charging: At 25±2℃, charge the battery at a constant current rate of 0.5C to 3.65V, then switch to constant voltage charging. The cutoff condition is that the current is less than 0.05C.

[0125] Resting: 25±2℃, rest for 10 minutes after charging is complete;

[0126] Discharge: 25±2℃, then discharge at a constant current of 0.5C to 2.5V, and record the discharge capacity as C1;

[0127] Resting: 25±2℃, rest for 10 minutes after discharge;

[0128] Cycle: Repeat the above steps 1000 times, and record the discharge capacity of the 1000th cycle as C1000;

[0129] Capacity retention rate: C1000 / C1*100% is the capacity retention rate corresponding to 1000 cycles.

[0130] The test results are shown in Table 2.

[0131] Table 2 Electrochemical performance of lithium batteries

[0132] As shown in Table 2, compared with Comparative Examples 1-5, when at least one of Type A and Type B binders is used in the preparation of Examples 1-3, the mixture can ensure that the positive electrode active material layer can be bonded to the positive electrode current collector while having better flexibility and tensile properties, ensuring the manufacturability of subsequent extrusion, thinning, and composite processes. When only Type A binder is used, the flexibility and tensile properties of the mixture are poor. When only at least one of Type B binders is used, the mixture cannot be agglomerated.

[0133] Compared with Comparative Examples 6-9, Examples 4-9 show that when α, β, and γ satisfy the following relationships: 1.0% ≤ α + β + γ ≤ 3.0%, and 0% < α < 3.0%, 0% ≤ β ≤ 1.0%, and 0% ≤ γ ≤ 2.0%, the positive electrode active material and the conductive agent can be effectively bonded together.

[0134] When α+β+γ<1.0%, it will lead to insufficient cohesion between the positive electrode active material and the conductive agent, resulting in poor composite effect between the positive electrode active material layer and the positive electrode current collector.

[0135] When α+β+γ > 3.0% or α > 3.0%, it will affect the energy density of the battery;

[0136] When β > 1.0%, it will lead to an increase in battery impedance and affect the battery's dynamic performance;

[0137] When γ > 2.0%, it will cause the material after mixing positive electrode active material, conductive agent and type B binder to a certain extent to agglomerate, which will affect the stability of type A binder added during the generation process and have a negative impact on the consistency of extruded film.

[0138] Compared with Comparative Example 10, Examples 9 and 10-11 show that when the value of X is in the range of 70% ≤ X < 100%, the solid phase ingredients can be evenly dispersed during the mixing process, and the subsequent drying time of the electrode is reduced, saving energy and manufacturing costs. When the value of X is less than 70%, the extruded film is difficult to form and cannot be effectively combined with the positive electrode current collector. At the same time, the low solid content requires an increase in the amount of solvent used and the energy consumption for baking, thus increasing the manufacturing cost.

[0139] In summary, the technical solution disclosed in this invention, which prepares positive electrode sheets under high solid content conditions through combinations of different binders, exhibits good manufacturability. The manufacturing process effectively reduces solvent usage, thereby lowering energy consumption and manufacturing costs. Furthermore, batteries fabricated using this method exhibit low DC internal resistance, high discharge ratio, and excellent cycle capacity retention. This demonstrates that this invention provides a low-cost, high-performance battery manufacturing solution, highly suitable for applications in power batteries and energy storage batteries.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A positive electrode plate, characterized in that: The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The positive active material layer includes a positive active material, a conductive agent, and a binder. The binder includes type A binders and type B binders. The type A binder includes a first binder, and the type B binder includes at least one of a second binder and a third binder. The total mass of the positive active material layer is 100%, the content of the first binder is α, and the content of the second binder is β. ； The content of the third adhesive is γ, and α, β, and γ satisfy the following relationship: 1.0% ≤ α + β + γ ≤ 3.0%, where 0% < α < 3.0%, 0% ≤ β ≤ 1.0%, and 0% ≤ γ ≤ 2.0%.

2. The positive electrode sheet according to claim 1, characterized in that: The positive electrode active material, the conductive agent, and the binder are mixed to form a positive electrode mixture. The positive electrode mixture forms a layer of the positive electrode active material on the surface of the positive electrode current collector. The solid content of the positive electrode mixture is X, and the value of X is in the range of 70% ≤ X < 100%.

3. The positive electrode sheet according to claim 2, characterized in that: Prior to the formation of the positive electrode mixture, the type A binder is prepared by mixing and fusing the first binder with a solvent.

4. The positive electrode sheet according to claim 2, characterized in that: The positive electrode mixture is extruded to form a membrane, and the membrane is combined with the positive electrode current collector to obtain the positive electrode sheet. The tensile strength of the membrane is S MPa, and the value of S is in the range of 0.1 MPa ≤ S.

5. The positive electrode sheet according to claim 2, characterized in that: The relationship between X and α, β, and γ is: 70% ≤ (0.75α + 0.83β + 0.79γ) / (α + β + γ) ≤ X < 100%.

6. The positive electrode sheet according to claim 4, characterized in that: The relationship between S and α, β, and γ is: 0.1≤6α+3β+110γ≤S.

7. The positive electrode sheet according to claim 1, characterized in that: The first adhesive includes one or more of rubber, modified rubber, polyvinylidene fluoride, modified polyvinylidene fluoride, polyimide, modified polyimide, polypropylene, modified polypropylene, polyacrylic acid, and modified polyacrylic acid.

8. The positive electrode sheet according to claim 1, characterized in that: The second adhesive includes one or more of polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl butyral, modified polyvinyl butyral, polyacrylonitrile, and modified polyacrylonitrile.

9. The positive electrode sheet according to claim 1, characterized in that: The third adhesive includes one or more of polytetrafluoroethylene and its modified polymers.

10. The positive electrode sheet according to claim 1, characterized in that: The positive electrode active material includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium-rich manganese-based materials. Or one or more of the following types of layered sodium cathodes and Prussian blue cathodes: sodium ferric sulfate, sodium ferric phosphate, sodium ferric pyrophosphate, sodium ferric pyrophosphate, sodium vanadium phosphate, sodium copper iron manganese oxide, sodium iron nickel manganese oxide, etc.

11. The positive electrode sheet according to claim 1, characterized in that: The conductive agent includes one or more of the following: carbon black, acetylene black, Ketjen black, graphene microspheres, three-dimensional conductive metal-organic frameworks, porous spherical carbon, conductive nanotubes, nanofibers, graphene, and graphite flakes.

12. The positive electrode sheet according to claim 1, characterized in that: The total mass of the positive electrode active material layer is 100%, the mass percentage of the positive electrode active material is 94.5% to 98.5%, the mass percentage of the conductive agent is 0.5% to 2.5%, and the mass percentage of the binder is 1.0% to 3.0%.

13. A method for preparing a positive electrode sheet according to any one of claims 1-12, characterized in that: Includes the following steps: (1) Pre-preparation of positive electrode mixture: Mix the positive electrode active material, conductive agent and type B binder in the specified amounts evenly; (2) Preparation of positive electrode mixture: Add type A binder to the mixture in step (1) and mix evenly to obtain positive electrode mixture; wherein, type A binder is prepared by mixing and fusing the first binder with a solvent; (3) The positive electrode mixture in step (2) is extruded through a die to obtain a self-supporting membrane, and the membrane is combined with the positive electrode current collector to obtain a positive electrode sheet.

14. The method for preparing the positive electrode sheet according to claim 13, characterized in that: In step (3), the total mass of the positive electrode mixture is 100%, and the mass percentage of the solvent is X1, wherein the value of X1 is 0 < X ​​≤ 30%.

15. A battery, characterized in that: The positive electrode includes a negative electrode sheet, a separator, and a positive electrode sheet prepared by the method described in any one of claims 1-12 or any one of claims 13-14.

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