Positive electrode sheet, method for manufacturing same, and battery

Abstract

The application relates to a positive electrode sheet, a preparation method and a battery, wherein the positive electrode sheet comprises a positive electrode active material, a conductive agent, a binder, a film-forming salt and a composite additive; the film-forming salt is an alkali metal salt which is stable to air and resistant to water; and the composite additive is a composite of an alkali metal salt of a nitrogen-containing carboxylic acid and a conductive medium. In the positive electrode sheet, the film-forming salt, the alkali metal salt of the nitrogen-containing carboxylic acid and the conductive medium cooperate to realize the multifunctional integration of alkali metal supplementing, conductive network construction and interface film forming, and the alkali metal supplementing process and the film forming process are completed synchronously in the same charging process without interference, so that the electrode preparation process is significantly simplified, and a new and efficient solution is provided for improving the initial coulomb efficiency, the rate performance and the cycle stability of the battery.

Description

Technical Field

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

[0002] With the rapid development of electric vehicles, energy storage power stations, and portable electronic devices, the market has placed increasingly stringent demands on the energy density, cycle life, and fast charging capabilities of alkali metal ion batteries such as lithium-ion, sodium-ion, and potassium-ion batteries. However, during the first charge of a battery, the formation of a solid electrolyte interface film on the negative electrode surface irreversibly consumes a large number of alkali metal ions from the positive electrode, resulting in a significant reduction in the battery's initial coulombic efficiency and limiting the improvement of battery energy density.

[0003] To compensate for this irreversible capacity loss, the industry commonly uses the addition of alkali metal additives to the positive electrode. Ideally, these additives should irreversibly decompose and release alkali metal ions at a specific potential during the first charge, remaining inert during subsequent normal charge-discharge cycles. However, most alkali metal additives have poor electronic conductivity, slow oxidation decomposition kinetics, incomplete decomposition, and low alkali metal addition efficiency. After decomposition, these additives often leave behind inactive solid products. If these products are unevenly distributed or have significant volume variations, they can easily damage the original conductive network inside the electrode, leading to deterioration of electronic contact between active particles. Especially under high-rate charge-discharge conditions, the limited electron transport paths significantly increase the battery's internal resistance, severely restricting its fast-charging performance. Existing alkali metal additives are typically designed for single alkali metal ion battery systems, and their molecular structure and decomposition characteristics are difficult to directly transfer to other alkali metal battery systems. There is a lack of a universal alkali metal additive that can be used for multiple alkali metal battery systems.

[0004] The stability of the cathode interface also affects the cycle life of alkali metal ion batteries. At high potentials, side reactions easily occur between the cathode material and the electrolyte, leading to transition metal dissolution, electrolyte decomposition, and increased battery internal resistance. Conventional interfacial film-forming additives (such as vinylene carbonate and fluorocarbonates) primarily act on the anode, offering limited protection to the cathode. While adding cathode film-forming salts alone can improve interfacial stability, most are extremely sensitive to moisture and air, requiring storage and handling in a strictly inert atmosphere, significantly increasing equipment investment and operating costs. Furthermore, in existing technologies, the alkali metal replenishment process and the interfacial film-forming process typically need to be handled separately, making it difficult to coordinate them within the same charging step, resulting in complex electrode fabrication processes and low production efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a positive electrode sheet, a preparation method, and a battery. By specifying the composition of the positive electrode sheet, it is possible to achieve multifunctional integration of alkali metal supplementation, conductive network construction, and interfacial film formation. Moreover, the alkali metal supplementation process and the film formation process can be completed simultaneously in the same charging process without interference, which significantly simplifies the electrode preparation process and provides a new and efficient solution for improving the first coulombic efficiency, rate performance, and cycle stability of the battery.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material, a conductive agent, a binder, a film-forming salt, and a composite additive;

[0008] The film-forming salt is an alkali metal salt that is stable to air and resistant to water.

[0009] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium.

[0010] In the positive electrode sheet described in this invention, the film-forming salt, nitrogen-containing carboxylic acid alkali metal salt, and conductive medium work together to achieve universal compatibility of the nitrogen-containing carboxylic acid alkali metal salt in lithium, sodium, and potassium battery systems. The conductive medium reduces the contact resistance and electrochemical polarization of the nitrogen-containing carboxylic acid alkali metal salt during oxidative decomposition, accelerates the oxidative decomposition efficiency of the nitrogen-containing sacrificial salt during charge and discharge, and achieves efficient utilization of the nitrogen-containing carboxylic acid alkali metal salt. After decomposition, the nitrogen-containing carboxylic acid alkali metal salt constructs a hierarchical conductive framework in situ, forming a continuous and stable electron transport network in synergy with the conductive medium, significantly improving conductivity under high-rate charge and discharge. In addition, the film-forming salt generates an interface protective film in situ during charging, effectively stabilizing the positive electrode / electrolyte interface. The synergistic effect of these three elements achieves multifunctional integration of alkali metal replenishment, conductive network construction, and interface film formation in the same electrode sheet. Moreover, the alkali metal replenishment process and the film formation process are completed synchronously in the same charging process without interference, significantly simplifying the electrode preparation process and providing a novel and efficient solution for improving the initial coulombic efficiency, rate performance, and cycle stability of batteries.

[0011] In some embodiments, the mass ratio of the positive electrode active material, conductive agent and binder is 70:(10~20):(10~20).

[0012] In some embodiments, the amount of the composite additive is 0.01wt% to 20wt% of the total mass of the positive electrode active material, conductive agent and binder.

[0013] In some embodiments, the amount of the film-forming salt is 1 wt% to 20 wt% of the total mass of the positive electrode active material, conductive agent and binder.

[0014] In some embodiments, the film-forming salt includes any one or a combination of at least two of MBOB, MDFOB, MBF4, or MNO3, wherein M is any one or a combination of at least two of Na, Li, or K.

[0015] In some embodiments, the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium in the composite additive is (70~90):(10~30).

[0016] In some embodiments, the nitrogen-containing carboxylic acid alkali metal salt includes at least two of a first nitrogen-containing carboxylic acid alkali metal salt, a second nitrogen-containing carboxylic acid alkali metal salt, and a third nitrogen-containing carboxylic acid alkali metal salt;

[0017] The first nitrogen-containing carboxylic acid alkali metal salt can be oxidized and decomposed to produce NC. - Nitrogen-carbon framework structure;

[0018] The second nitrogen-containing carboxylic acid alkali metal salt can be oxidized and decomposed to produce NC2. - Nitrogen-carbon framework structure;

[0019] The third nitrogen-containing alkali metal carboxylic acid salt can be oxidized and decomposed to produce NC3. - Nitrogen-carbon framework structure.

[0020] In some embodiments, the first nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of glycine salt, aspartic acid salt, glutamate salt, alanine salt, or lysine salt.

[0021] In some embodiments, the second nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of iminodiacetate, iminodisuccinate, ethylenediaminetetraacetate, ethylenediamine-N,N'-diacetate, or ethylenediamine-N,N'-diacetate.

[0022] In some embodiments, the third nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of nitrogen triacetate, diethylenetriaminepentaacetate, or triethylenetetraminehexaacetate.

[0023] In some embodiments, the molar ratio between any two nitrogen-containing carboxylic acid alkali metal salts among the first, second, and third nitrogen-containing carboxylic acid alkali metal salts is (0.5~1.5):(0.5~1.5).

[0024] In some embodiments, the conductive medium includes any one or a combination of at least two of conductive carbon, conductive polymer, Mxene, conductive boride, or metal carbide.

[0025] In a second aspect, the present invention provides a method for preparing a positive electrode sheet, the method comprising: mixing a positive electrode active material, a conductive agent, a binder, a film-forming salt and a composite additive to form a slurry, and then coating and drying the resulting slurry to obtain the positive electrode sheet described in the first aspect.

[0026] Thirdly, the present invention provides a battery comprising the positive electrode plate described in the first aspect.

[0027] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] In the positive electrode sheet described in this invention, the film-forming salt, nitrogen-containing carboxylic acid alkali metal salt, and conductive medium work together to achieve universal compatibility of the nitrogen-containing carboxylic acid alkali metal salt in lithium, sodium, and potassium battery systems. The conductive medium reduces the contact resistance and electrochemical polarization of the nitrogen-containing carboxylic acid alkali metal salt during oxidative decomposition, accelerates the oxidative decomposition efficiency of the nitrogen-containing sacrificial salt during charge and discharge, and achieves efficient utilization of the nitrogen-containing carboxylic acid alkali metal salt. After decomposition, the nitrogen-containing carboxylic acid alkali metal salt constructs a hierarchical conductive framework in situ, forming a continuous and stable electron transport network in synergy with the conductive medium, significantly improving conductivity under high-rate charge and discharge. In addition, the film-forming salt generates an interface protective film in situ during charging, effectively stabilizing the positive electrode / electrolyte interface. The synergistic effect of these three elements achieves multifunctional integration of alkali metal replenishment, conductive network construction, and interface film formation in the same electrode sheet. Moreover, the alkali metal replenishment process and the film formation process are completed synchronously in the same charging process without interference, significantly simplifying the electrode preparation process and providing a novel and efficient solution for improving the initial coulombic efficiency, rate performance, and cycle stability of batteries. Detailed Implementation

[0030] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0031] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0032] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0033] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0034] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0035] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0036] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0037] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0038] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0039] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0040] Traditional alkali metal supplements have limited functionality, adapting only to a single alkali metal-ion battery system. Existing alkali metal supplements are typically designed for specific alkali metal-ion batteries (such as sodium-ion batteries), and their molecular structure and decomposition characteristics are difficult to directly transfer to other alkali metal-ion battery systems. There is a lack of universal alkali metal supplement design schemes applicable to multiple alkali metal battery systems such as lithium, sodium, and potassium. Furthermore, the conductive network of existing alkali metal supplements suffers from limited electron transport paths during high-rate charge and discharge, easily leading to transport bottlenecks, increased internal battery impedance, and impacting fast-charging efficiency. In existing alkali metal-ion batteries, most film-forming salts (such as hexafluorophosphate) are extremely sensitive to water and air, requiring operation in a strictly inert atmosphere, increasing process difficulty and manufacturing costs. Simultaneously, in existing technologies, the alkali metal supplementation process and the interfacial film formation process usually need to be handled separately, making it difficult to complete them collaboratively in the same charging process. This results in complex electrode fabrication processes, low production efficiency, and difficulty in achieving the organic integration of the three functions of alkali metal supplementation, conductivity enhancement, and interfacial film formation.

[0041] In a first aspect, the present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material, a conductive agent, a binder, a film-forming salt, and a composite additive;

[0042] The film-forming salt is an alkali metal salt that is stable to air and resistant to water.

[0043] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium.

[0044] In the positive electrode sheet described in this invention, the film-forming salt, nitrogen-containing carboxylic acid alkali metal salt, and conductive medium work together to achieve universal compatibility of the nitrogen-containing carboxylic acid alkali metal salt in lithium, sodium, and potassium battery systems. The conductive medium reduces the contact resistance and electrochemical polarization of the nitrogen-containing carboxylic acid alkali metal salt during oxidative decomposition, accelerates the oxidative decomposition efficiency of the nitrogen-containing sacrificial salt during charge and discharge, and achieves efficient utilization of the nitrogen-containing carboxylic acid alkali metal salt. After decomposition, the nitrogen-containing carboxylic acid alkali metal salt constructs a hierarchical conductive framework in situ, forming a continuous and stable electron transport network in synergy with the conductive medium, significantly improving conductivity under high-rate charge and discharge. In addition, the film-forming salt generates an interface protective film in situ during charging, effectively stabilizing the positive electrode / electrolyte interface. The synergistic effect of these three elements achieves multifunctional integration of alkali metal replenishment, conductive network construction, and interface film formation in the same electrode sheet. Moreover, the alkali metal replenishment process and the film formation process are completed synchronously in the same charging process without interference, significantly simplifying the electrode preparation process and providing a novel and efficient solution for improving the initial coulombic efficiency, rate performance, and cycle stability of batteries.

[0045] In some embodiments, the mass ratio of the positive electrode active material, conductive agent and binder is 70:(10~20):(10~20).

[0046] The mass ratio of the positive electrode active material to the conductive agent is 70:10 to 70:20, for example, it can be 70:10, 70:12, 70:15, 70:16, 70:18 or 70:20, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] The mass ratio of the positive electrode active material to the binder is 70:10 to 70:20, for example, it can be 70:10, 70:12, 70:15, 70:16, 70:18 or 70:20, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Optionally, the positive electrode active material includes any one of lithium-ion battery positive electrode active materials, sodium-ion battery positive electrode active materials, or potassium-ion battery positive electrode active materials.

[0049] Optionally, the positive electrode active material of the lithium-ion battery includes any one or a combination of at least two of lithium manganese oxide, lithium iron phosphate, ternary materials, or lithium-rich manganese materials.

[0050] Optionally, the positive electrode active material of the sodium-ion battery includes any one or a combination of at least two of the following: polyanionic positive electrode material, Prussian blue positive electrode material, or oxide positive electrode material.

[0051] Optionally, the positive electrode active material for potassium-ion batteries includes any one or a combination of at least two of polyanionic positive electrode materials, Prussian blue positive electrode materials, or layered metal oxide positive electrode materials.

[0052] Optionally, the conductive agent includes any one or a combination of at least two of Super P, acetylene black, Ketjen black, or carbon nanotubes.

[0053] Optionally, the adhesive may include any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, or polyacrylic acid.

[0054] In some embodiments, the amount of the composite additive is 0.01wt% to 20wt% of the total mass of the positive electrode active material, conductive agent and binder. For example, it can be 0.01wt%, 0.1wt%, 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 16wt%, 18wt% or 20wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] In some embodiments, the amount of the film-forming salt is 1 wt% to 20 wt% of the total mass of the positive electrode active material, conductive agent and binder. For example, it can be 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 16 wt%, 18 wt% or 20 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] In some embodiments, the film-forming salt includes any one or a combination of at least two of MBOB, MDFOB, MBF4, or MNO3. Typical but non-limiting combinations include a combination of MBOB and MDFOB, a combination of MDFOB and MBF4, a combination of BMF4 and MNO3, or a combination of MBOB, MDFOB, MBF4, and MNO3.

[0057] Where M is any one or at least two of Na, Li, or K. Typical but non-limiting combinations include combinations of Na and Li, Na and K, Li and K, or Na, Li, and K.

[0058] The film-forming salt used in this invention is chemically inert to water and oxygen, allowing the coating and drying process to be completed at room temperature without the need for strict inert atmosphere protection, significantly reducing the requirements for production equipment and operating costs. This type of film-forming salt has low solubility in conventional solvents and is directly mixed with the positive electrode slurry in solid particle form for coating, enabling uniform distribution within the electrode sheet. During the electrochemical reaction of the battery's first charge, as the electrode potential increases, the film-forming salt particles undergo electrochemical oxidative decomposition, generating an in-situ interfacial protective film that uniformly covers the surface of the active material.

[0059] Composite additives can significantly improve the kinetic efficiency and uniformity of alkali metal replenishment. The conductive medium within them constructs a highly efficient electron transport network, greatly reducing the contact resistance and electrochemical polarization of nitrogen-containing polycarboxylic acid alkali metal salts during oxidative decomposition, ensuring the full release of alkali metal ions, thereby improving the utilization rate of the alkali metal replenishment agent and the first-cycle coulombic efficiency. Simultaneously, the conductive medium and the nitrogen-containing carbon-based framework generated from the decomposition of nitrogen-containing polycarboxylic acid alkali metal salts synergistically form a continuous and stable electron transport network. Furthermore, the conductive network can homogenize the electric field distribution on the electrode surface, suppressing localized overheating or high-voltage side reactions, thus improving the safety of the alkali metal replenishment process and the overall cycle stability of the battery.

[0060] In some embodiments, the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium in the composite additive is (70~90):(10~30), for example, it can be 70:30, 75:25, 80:20, 85:15 or 90:10, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. If the conductive medium is too little, it will lead to insufficient electron transport and incomplete salt decomposition. If the conductive medium is too much, it will dilute the capacity of the alkali metal and reduce the energy density.

[0061] Optionally, the nitrogen-containing alkali metal carboxylic acid salt and the conductive medium are ball-milled to obtain the composite additive; for example, the ball milling time is 10h~24h, such as 10h, 12h, 15h, 16h, 18h, 20h, 21h or 24h. If the ball milling time is too short, the nitrogen-containing polycarboxylic acid salt and the conductive medium will be mixed unevenly, the interface between the two will be weak and the particle size distribution will be wide, which will significantly reduce the sodium supplementation efficiency and the first-cycle coulombic efficiency, and at the same time, the batch repeatability will be poor. If the ball milling time is too long, it will cause energy waste and a decrease in process efficiency.

[0062] In some embodiments, the nitrogen-containing carboxylic acid alkali metal salt includes at least two of a first nitrogen-containing carboxylic acid alkali metal salt, a second nitrogen-containing carboxylic acid alkali metal salt, and a third nitrogen-containing carboxylic acid alkali metal salt;

[0063] The first nitrogen-containing carboxylic acid alkali metal salt can be oxidized and decomposed to produce NC. - Nitrogen-carbon framework structure;

[0064] The second nitrogen-containing carboxylic acid alkali metal salt can be oxidized and decomposed to produce NC2. - Nitrogen-carbon framework structure;

[0065] The third nitrogen-containing alkali metal carboxylic acid salt can be oxidized and decomposed to produce NC3. - Nitrogen-carbon framework structure.

[0066] Different nitrogen-containing carboxylic acid alkali metal salts decompose to form nitrogen-containing carbon-based frameworks (such as NC-, NC2-, and NC3- structures), enhancing the overall conductivity of the electrode. The conjugated framework structure (NC- / NC2- / NC3-) of nitrogen-containing carboxylic acid alkali metal salts promotes electron delocalization transport, significantly widening the electron transport path to reduce interfacial impedance. The proportions of different nitrogen-based carboxylic acid alkali metal salts can be adjusted according to the requirements of the conductive network. Through the compounding of various nitrogen-containing sacrificial salts, their oxidative decomposition during charge and discharge achieves the dual functions of alkali metal supplementation and conductive framework construction in different battery systems. The nitrogen-containing conjugated carbon framework generated in situ by nitrogen-containing carboxylic acid alkali metal salts, due to its active sites such as pyridine nitrogen and pyrrole nitrogen and its high-density defects, exhibits significantly increased catalytic activity for electrolyte oxidative decomposition after compounding with the conductive medium. This makes it more prone to initiating interfacial side reactions, leading to electrolyte consumption, gas production, and battery performance degradation. Adding film-forming salts (such as MDFOB and MBOB) physically isolates the electrolyte from the carbon skeleton by forming a dense interfacial protective film containing metal fluorides and boron oxides in situ on the carbon skeleton surface, preventing the adsorption and decomposition of solvent molecules and anions at the active sites.

[0067] In some embodiments, the first nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of glycine salt, aspartic acid salt, glutamate salt, alanine salt, or lysine salt, wherein the alkali metal element includes any one of Na, Li, or K.

[0068] In some embodiments, the second nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of iminodiacetate, iminodisuccinate, ethylenediaminetetraacetate, ethylenediamine-N,N'-diacetate, or ethylenediamine-N,N'-diacetate, wherein the alkali metal element includes any one of Na, Li, or K.

[0069] In some embodiments, the third nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of nitrogen triacetate, diethylenetriaminepentaacetate, or triethylenetetraminehexaacetate, wherein the alkali metal element includes any one of Na, Li, or K.

[0070] In some embodiments, the molar ratio between any two nitrogen-containing carboxylic acid alkali metal salts among the first, second, and third nitrogen-containing carboxylic acid alkali metal salts is (0.5~1.5):(0.5~1.5), for example, it can be 0.5:1.5, 1:1, or 1.5:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the conductive medium includes any one or a combination of at least two of conductive carbon, conductive polymer, Mxene, conductive boride, or metal carbide.

[0072] Optionally, the conductive carbon may include any one or a combination of at least two of conductive graphite, Super P, acetylene black, Ketjen black, carbon nanotubes, or graphene. Typical but non-limiting combinations include combinations of conductive graphite and Super P, combinations of acetylene black and Ketjen black, combinations of carbon nanotubes and graphene, or combinations of conductive graphite, Super P, acetylene black, Ketjen black, carbon nanotubes, or graphene.

[0073] Optionally, the conductive polymer may include any one or a combination of at least two of polyacetylene, polypyrrole, polyaniline, or polythiophene and its derivatives.

[0074] Optionally, Mxene may include any one or a combination of at least two of titanium-based Mxene, vanadium-based Mxene, or niobium-based Mxene. Typical but non-limiting combinations include combinations of titanium-based Mxene and vanadium-based Mxene, combinations of vanadium-based Mxene and niobium-based Mxene, or combinations of titanium-based Mxene, vanadium-based Mxene, and niobium-based Mxene.

[0075] Optionally, the conductive boride may include any one or a combination of at least two of titanium diboride, zirconium diboride, cerium hexaboride, or lanthanum hexaboride. Typical but non-limiting combinations include combinations of titanium diboride and zirconium diboride, combinations of zirconium diboride and cerium hexaboride, combinations of cerium hexaboride and lanthanum hexaboride, or combinations of titanium diboride, zirconium diboride, cerium hexaboride, and lanthanum hexaboride.

[0076] Optionally, the metal carbide may include any one or a combination of at least two of calcium carbide, tungsten carbide, silicon carbide or boron carbide. Typical but non-limiting combinations include combinations of calcium carbide and tungsten carbide, combinations of tungsten carbide and silicon carbide, combinations of silicon carbide and boron carbide, or combinations of calcium carbide, tungsten carbide, silicon carbide and boron carbide.

[0077] In a second aspect, the present invention provides a method for preparing a positive electrode sheet, the method comprising: mixing a positive electrode active material, a conductive agent, a binder, a film-forming salt and a composite additive to form a slurry, and then coating and drying the resulting slurry to obtain the positive electrode sheet described in the first aspect.

[0078] Thirdly, the present invention provides a battery comprising the positive electrode plate described in the first aspect.

[0079] Optionally, the positive electrode sheet is disposed on at least one side surface of the positive electrode current collector; the positive electrode current collector includes aluminum foil.

[0080] Example 1

[0081] This embodiment provides a positive electrode sheet, including a positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and composite additives.

[0082] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 70:30; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate and sodium alanine in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0083] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:20:10; the amount of the composite additive is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0084] This embodiment provides a method for preparing a positive electrode, including:

[0085] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0086] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0087] Example 2

[0088] This embodiment provides a positive electrode sheet, including a positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and composite additives.

[0089] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 70:30; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate and pentasodium diethylenetriaminepentaacetate in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0090] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:20:10; the amount of the composite additive is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0091] This embodiment provides a method for preparing a positive electrode, including:

[0092] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0093] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0094] Example 3

[0095] This embodiment provides a positive electrode sheet, including a positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and composite additives.

[0096] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 70:30; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate, sodium alanine and pentasodium diethylenetriaminepentaacetate in a molar ratio of 1:1:1; the conductive medium is carbon nanotubes.

[0097] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:20:10; the amount of the composite additive is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0098] This embodiment provides a method for preparing a positive electrode, including:

[0099] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0100] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0101] Example 4

[0102] This embodiment provides a positive electrode sheet, including a positive electrode active material (sodium vanadium phosphate, Na3V2(PO4)3), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and composite additives;

[0103] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 70:30; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate and sodium alanine in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0104] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:20:10; the amount of the composite additive is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0105] This embodiment provides a method for preparing a positive electrode, including:

[0106] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0107] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0108] Example 5

[0109] This embodiment provides a positive electrode sheet, including a positive electrode active material (lithium iron phosphate, LiFePO4), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and a composite additive;

[0110] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 70:30; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate and sodium alanine in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0111] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:20:10; the amount of the composite additive is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 10 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0112] This embodiment provides a method for preparing a positive electrode, including:

[0113] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0114] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0115] Example 6

[0116] This embodiment provides a positive electrode sheet, including a positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and composite additives.

[0117] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 80:20; the nitrogen-containing carboxylic acid alkali metal salt is composed of ethylenediaminetetraacetic acid tetrasodium salt and sodium alanine in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0118] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:15:15; the amount of the composite additive is 0.01 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 20 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0119] This embodiment provides a method for preparing a positive electrode, including:

[0120] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0121] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0122] Example 7

[0123] This embodiment provides a positive electrode sheet, including a positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), a conductive agent (Super P), a binder (PVDF), a film-forming salt (NaBOB), and composite additives.

[0124] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 90:10; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate and sodium alanine in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0125] The mass ratio of the positive electrode active material, conductive agent, and binder is 70:10:20; the amount of the composite additive is 20 wt% of the total mass of the positive electrode active material, conductive agent, and binder; and the amount of the film-forming salt is 1 wt% of the total mass of the positive electrode active material, conductive agent, and binder.

[0126] This embodiment provides a method for preparing a positive electrode, including:

[0127] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0128] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and film-forming salt, stir evenly to obtain a slurry, coat the obtained slurry on aluminum foil, and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0129] Comparative Example 1

[0130] This comparative example provides a positive electrode sheet that is identical to Example 1 except that no composite additives are used, including positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), conductive agent (Super P), binder (PVDF) and film-forming salt (NaBOB).

[0131] The mass ratio of the positive electrode active material, conductive agent and binder is 70:20:10; the amount of the film-forming salt is 10 wt% of the total mass of the positive electrode active material, conductive agent and binder.

[0132] This comparative example provides a method for preparing a positive electrode, including:

[0133] The positive electrode active material, conductive agent and binder are mixed, and then film-forming salt is added. The mixture is stirred evenly to obtain a slurry. The slurry is coated on aluminum foil and dried in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0134] Comparative Example 2

[0135] This comparative example provides a positive electrode sheet, which is the same as that in Example 1 except that no film-forming salt is used, including positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), conductive agent (Super P), binder (PVDF) and composite additives.

[0136] The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium; the mass ratio of the nitrogen-containing carboxylic acid alkali metal salt to the conductive medium is 70:30; the nitrogen-containing carboxylic acid alkali metal salt is composed of tetrasodium ethylenediaminetetraacetate and sodium alanine in a molar ratio of 1:1; the conductive medium is carbon nanotubes.

[0137] The mass ratio of the positive electrode active material, conductive agent and binder is 70:20:10; the amount of the composite additive is 10wt% of the total mass of the positive electrode active material, conductive agent and binder.

[0138] This comparative example provides a method for preparing a positive electrode, including:

[0139] S1. A composite additive is obtained by ball milling and mixing nitrogen-containing carboxylic acid alkali metal salts with a conductive medium for 24 hours.

[0140] S2. Mix the positive electrode active material, conductive agent and binder, then add composite additives and stir evenly to obtain a slurry. Coat the obtained slurry onto aluminum foil and dry it in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0141] Comparative Example 3

[0142] This comparative example provides a positive electrode sheet, which is the same as that in Example 1 except that no film-forming salt and composite additives are used, including positive electrode active material (sodium iron pyrophosphate, Na4Fe3(PO4)2P2O7), conductive agent (Super P) and binder (PVDF).

[0143] The mass ratio of the positive electrode active material, conductive agent and binder is 70:20:10.

[0144] This comparative example provides a method for preparing a positive electrode, including:

[0145] The positive electrode active material, conductive agent and binder are mixed and stirred evenly to obtain a slurry. The slurry is coated on aluminum foil and dried in a vacuum oven at 100°C for 8 hours to obtain the positive electrode sheet.

[0146] Performance Characterization

[0147] Using the electrode sheets provided in the above application examples and comparative application examples as positive electrodes, sodium-ion batteries were assembled (using a metallic sodium sheet as the counter electrode, a glass fiber membrane as the separator, and an organic electrolyte suitable for the phosphate positive electrode (the electrolyte solute was 1 mol / L NaPF6, and the solvent was a mixture of ethylene carbonate, dimethyl carbonate, and fluoroethylene carbonate in a volume ratio of 3:6:1)). Electrochemical tests were performed. The first-week charge specific capacity was recorded when charging to 4.5V at a current density of 0.2C. After three weeks of activation at a current density of 0.2C, the discharge specific capacity was recorded. Then, a rate performance test was conducted at 10C, where 1C = 100 mA / g. The results are shown in Table 1. The capacity retention rate is the percentage of the activated discharge specific capacity to the 10C discharge specific capacity.

[0148] Table 1

[0149]

[0150] The results of Examples 1 to 3, 6, and 7, and Comparative Examples 1 to 3, show that the use of a composite of nitrogen-containing polycarboxylic acid sodium salt and conductive medium in the sodium iron pyrophosphate cathode significantly improves the first-cycle charge-discharge specific capacity of the battery, and also significantly improves the fast-charging performance. The addition of NaBOB further optimizes the interfacial stability between the electrode and the electrolyte, contributing to the formation of a uniform and stable interfacial protective film, thereby improving the battery's cycle life. Examples 1 to 3, 6, and 7 also demonstrate that optimizing the composition ratio of the nitrogen-containing polycarboxylic acid alkali metal salt and conductive medium composite can further improve the rate performance of sodium-ion batteries, indicating that the structural design of this composite plays a crucial regulatory role in the overall electrochemical performance of the battery.

[0151] The results of Examples 1 and 4 show that the prepared composite of nitrogen-containing polycarboxylic acid sodium salt and conductive medium is well-suited for different types of sodium-ion battery cathode materials, such as sodium iron pyrophosphate and sodium vanadium pyrophosphate. Using this composite significantly improves the first-cycle charge-discharge specific capacity and rate performance of the battery. Furthermore, the addition of NaBOB during the coating process effectively enhances the battery's cycle stability.

[0152] The results of Examples 1 and 5 demonstrate that the prepared nitrogen-containing polycarboxylic acid alkali metal salt and conductive medium composite is not only suitable for sodium-ion battery systems but also well-suited for lithium-ion battery systems. Introducing this composite into the cathode of different alkali metal ion batteries significantly improved the first-cycle charge-discharge specific capacity and rate performance. Adding a suitable film-forming salt during coating further enhanced the battery's cycle stability. These results fully validate the good versatility and excellent electrochemical performance-enhancing effect of the composite and film-forming salt in different alkali metal ion battery systems.

[0153] In summary, the nitrogen-containing polycarboxylate / conductive medium composite of this invention can supplement alkali metal ions in different battery systems, regardless of the type of alkali metal ion used for coordination. Only the corresponding lithium, sodium, or potassium salts need to be prepared, and they can be applied to lithium, sodium, and potassium battery systems, respectively. The reaction mechanisms of different nitrogen-containing polycarboxylate / conductive medium composites are consistent during the electrochemical reaction process, achieving universal adaptability of the same technical solution to different battery systems. This eliminates the need for re-screening of alkali metal supplementation agents, significantly shortening the R&D cycle and reducing development costs, providing a universal solution for alkali metal supplementation technology in alkali metal batteries.

[0154] This invention uses nitrogen-containing polycarboxylic acid alkali metal salts combined with conductive media (such as carbon nanotubes, graphene, conductive carbon black, etc.). The conductive media constructs continuous electron transport channels between and on the surface of the alkali metal supplement particles, reducing the contact resistance and electrochemical polarization of the nitrogen-containing polycarboxylic acid alkali metal salts during oxidative decomposition. This ensures that the alkali metal supplement can fully and rapidly decompose and release alkali metal ions, thereby significantly improving the utilization rate of the alkali metal supplement and the coulombic efficiency of the battery in the first cycle.

[0155] This invention introduces water- and air-stabilized film-forming salts such as difluorooxalate borate. These salts are chemically inert to water vapor and oxygen, allowing for coating and drying at room temperature without the need for strict inert atmosphere protection, significantly reducing the requirements for production equipment and operating costs. These film-forming salts have low solubility in conventional solvents (especially sodium salts), and when directly mixed with the positive electrode slurry in solid particle form, they can be uniformly distributed within the electrode sheet. During the electrochemical reaction of the battery's first charge, as the electrode potential increases, the solid film-forming salt particles undergo electrochemical oxidation and decomposition, generating an in-situ interfacial protective film that uniformly covers the surface of the active material.

[0156] This invention establishes a composite additive system integrating three functions: alkali metal replenishment, conductivity enhancement, and interface stabilization. The three components have clearly defined roles and synergistic effects during electrode preparation and battery activation: the nitrogen-containing polycarboxylic acid alkali metal salt provides an alkali metal ion source to compensate for irreversible capacity loss and form a hierarchical conductive framework; the conductive medium provides an electron transport path to ensure the full decomposition of the alkali metal replenishment agent; and the water-resistant film-forming salt forms an in-situ interface protective film during charging. All three components coexist compatiblely within the same electrode sheet, and the alkali metal replenishment process and film formation process are completed simultaneously in the same charging step without interference, simplifying the electrode preparation process and improving the overall electrochemical performance of the battery.

[0157] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive electrode active material, a conductive agent, a binder, a film-forming salt, and a composite additive; The film-forming salt is an alkali metal salt that is stable to air and resistant to water. The composite additive is a complex of a nitrogen-containing carboxylic acid alkali metal salt and a conductive medium.

2. The positive electrode sheet according to claim 1, characterized in that, The mass ratio of the positive electrode active material, conductive agent and binder is 70:(10~20):(10~20); And / or, the amount of the composite additive is 0.01wt%~20wt% of the total mass of the positive electrode active material, conductive agent and binder; And / or, the amount of the film-forming salt is 1wt% to 20wt% of the total mass of the positive electrode active material, conductive agent and binder.

3. The positive electrode sheet according to claim 1 or 2, characterized in that, The film-forming salt includes any one or a combination of at least two of MBOB, MDFOB, MBF4, or MNO3, wherein M is any one or a combination of at least two of Na, Li, or K.

4. The positive electrode sheet according to claim 1 or 2, characterized in that, In the composite additive, the mass ratio of nitrogen-containing carboxylic acid alkali metal salt to conductive medium is (70~90):(10~30).

5. The positive electrode sheet according to claim 4, characterized in that, The nitrogen-containing carboxylic acid alkali metal salt includes at least two of a first nitrogen-containing carboxylic acid alkali metal salt, a second nitrogen-containing carboxylic acid alkali metal salt, and a third nitrogen-containing carboxylic acid alkali metal salt; The first nitrogen-containing carboxylic acid alkali metal salt can be oxidized and decomposed to produce NC. - Nitrogen-carbon framework structure; The second nitrogen-containing carboxylic acid alkali metal salt can be oxidized and decomposed to produce NC2. - Nitrogen-carbon framework structure; The third nitrogen-containing alkali metal carboxylic acid salt can be oxidized and decomposed to produce NC3. - Nitrogen-carbon framework structure.

6. The positive electrode sheet according to claim 5, characterized in that, The first nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of glycine salt, aspartic acid salt, glutamate salt, alanine salt, or lysine salt; And / or, the second nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of iminodiacetate, iminodisuccinate, ethylenediaminetetraacetate, ethylenediamine-N,N'-diacetate or ethylenediamine-N,N'-diacetate; And / or, the third nitrogen-containing carboxylic acid alkali metal salt includes any one or a combination of at least two of nitrogen triacetate, diethylenetriaminepentaacetate, or triethylenetetraminehexaacetate.

7. The positive electrode sheet according to claim 5, characterized in that, In the first nitrogen-containing carboxylic acid alkali metal salt, the second nitrogen-containing carboxylic acid alkali metal salt, and the third nitrogen-containing carboxylic acid alkali metal salt, the molar ratio between any two nitrogen-containing carboxylic acid alkali metal salts is (0.5~1.5):(0.5~1.5).

8. The positive electrode sheet according to claim 4, characterized in that, The conductive medium includes any one or a combination of at least two of conductive carbon, conductive polymer, Mxene, conductive boride, or metal carbide.

9. A method for preparing a positive electrode sheet, characterized in that, The preparation method includes: mixing positive electrode active material, conductive agent, binder, film-forming salt and composite additive to form a slurry, and coating and drying the resulting slurry to obtain the positive electrode sheet according to any one of claims 1 to 8.

10. A battery, characterized in that, The battery includes the positive electrode sheet as described in any one of claims 1 to 8.

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