Positive pole piece and preparation method thereof, battery monomer, battery device and power utilization device

Abstract

The invention provides a positive pole piece, a preparation method of the positive pole piece, a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece, electrolyte and a negative pole piece, the positive pole piece comprises a positive current collector and a positive active layer arranged on at least one side of the positive current collector, the positive active layer comprises a positive active material and modified groups, and the modified groups comprise a first modified group and a second modified group; the first modification group comprises at least one of a phosphate group, a phosphite group and a borate group, the second modification group comprises R1R2R3Si-, and R1, R2 and R3 are independently selected from hydrogen atoms, C1-C5 alkyl groups or C1-C5 halogenated alkyl groups.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a positive electrode sheet and its preparation method, a battery cell, a battery device, and an electrical device. Background Technology

[0002] In recent years, existing technologies have flourished in consumer electronics, power batteries, and energy storage systems, driving explosive growth in the secondary battery industry, particularly the lithium battery industry. On the one hand, the energy density requirements for lithium rechargeable batteries are constantly increasing; on the other hand, the scarcity of lithium resources is becoming increasingly prominent. Lithium and sodium belong to the same Group 1 elements in the periodic table and have similar physicochemical properties. Sodium's reserves in the Earth's crust are more than a thousand times that of lithium, and its industrial application prospects are broad. Therefore, sodium rechargeable batteries are attracting increasing attention. Lithium / sodium secondary batteries can be divided into two categories: lithium / sodium-ion batteries and lithium / sodium metal batteries. Lithium / sodium-ion batteries belong to the "rocking chair" battery category, meaning that during charge-discharge cycles, active ions repeatedly insert and extract between the positive and negative electrodes via the electrolyte. Lithium / sodium metal batteries are characterized by a generally bare (or coated) negative electrode current collector. The lightweight electrode assembly allows for higher energy density. During charging, active ions extract from the positive electrode and deposit on the negative electrode current collector, forming a lithium / sodium metal negative electrode. During discharging, the metal deposited at the negative electrode dissolves and re-inserts into the positive electrode. Under operating conditions, side reactions inevitably occur between the electrolyte and the positive and negative electrode materials in lithium / sodium secondary batteries, producing gas. This not only leads to deterioration in power performance and lifespan but can also trigger thermal runaway, posing significant safety risks. When stored at high temperatures, lithium / sodium secondary batteries generally exhibit increased impedance and severe gas generation due to the decreased chemical / electrochemical stability of the electrolyte. This problem is particularly prominent in lithium / sodium metal batteries, where the lithium / sodium metal deposited on the negative electrode has high activity.

[0003] In secondary batteries, side reactions between the electrolyte composition and the positive and negative electrodes produce a large amount of combustible gases, including H2. The H2 mainly originates from two sources: first, trace amounts of water that cannot be completely removed from the battery are reduced and decomposed at the negative electrode to produce gas; second, the electrolyte solvent undergoes protonation during oxidation at the positive electrode and is reduced to produce gas at the negative electrode.

[0004] In general, lithium / sodium secondary batteries commonly suffer from internal gas generation issues across multiple stages, including formation, charging / discharging, and storage. Current strategies to suppress gas generation in secondary batteries mostly involve adding functional additives to the electrolyte. However, this requires consideration of physical compatibility and chemical matching with other electrolyte components and offers limited protection for electrode material surfaces. Therefore, new development approaches and technical solutions are needed to provide effective strategies for suppressing gas generation in secondary batteries. Summary of the Invention

[0005] This application provides a positive electrode sheet and its preparation method, a battery cell, a battery device, and an electrical device to solve the problem of gas generation from the side reaction between the electrolyte and the positive electrode material.

[0006] This application provides a battery cell comprising a positive electrode, an electrolyte, and a negative electrode. The positive electrode includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector. The positive active layer includes a positive active material and modifying groups. The modifying groups include a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

[0007] When the positive electrode active layer includes a first modifying group and a second modifying group, the first modifying group can participate in the formation of a more stable CEI film, reducing the probability of side reactions between the positive electrode active material surface and the electrolyte, leading to gas generation. The second modifying group can use chemical reactions to reduce the water content in the positive electrode sheet and the electrolyte, inhibiting HF generation and reducing the degree of side reactions and gas generation at the interface film, thereby achieving the effect of suppressing gas generation in individual battery cells and improving safety during use.

[0008] In any implementation of the first aspect, R 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

[0009] In any embodiment of the first aspect, the substance providing the modifying group includes one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

[0010] In any embodiment of the first aspect, the positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0011] In any embodiment of the first aspect, the positive electrode active material comprises a polyanionic compound.

[0012] In any embodiment of the first aspect, the polyanionic compound includes carbon-coated sodium iron pyrophosphate or carbon-coated sodium iron phosphate.

[0013] In any embodiment of the first aspect, modified groups are dispersed throughout the thickness of the positive electrode active layer.

[0014] In any embodiment of the first aspect, the electrolyte of the battery cell includes an organic solvent, which includes one or more of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents and sulfone solvents.

[0015] In any embodiment of the first aspect, the aforementioned ether solvent includes one or more of cyclic ethers and chain ethers. Cyclic ethers include cyclic ethers with 4 to 8 carbon atoms, and chain ethers include chain ethers with 4 to 10 carbon atoms. Ether solvents can participate in SEI film formation to regulate the sodium ion deposition morphology, obtaining a thin and dense inorganic SEI film, thereby inhibiting sodium dendrite growth. However, ether solvents have a relatively low oxidation window, are prone to oxidation at the CEI film, and are highly volatile, easily generating gas. By modifying the groups to protect the positive electrode active material, the degree of oxidation of the ether solvent can be significantly reduced, thereby reducing the amount of gas generated by ether solvent oxidation.

[0016] In any embodiment of the first aspect, the ether solvent includes fluorinated ether solvents, including 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and / or cyclic ethers include one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4-methyl-1,3-dioxolane; and / or chain ethers include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, and diethylene glycol dimethyl ether.

[0017] In any embodiment of the first aspect, the negative electrode sheet is a negative current collector or a negative current collector with a conductive layer on its surface.

[0018] A second aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive active layer disposed on at least one side of the positive current collector, wherein the positive active layer comprises a positive active material and modifying groups, the modifying groups comprising a first modifying group and a second modifying group, the first modifying group comprising at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups, and the second modifying group comprising R 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

[0019] In any implementation of the second aspect, R 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

[0020] In any embodiment of the second aspect, the substance providing the modifying group includes one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

[0021] In any embodiment of the second aspect, the mass content of silicon in the positive electrode active layer is 0.005% to 0.1%, and may be 0.008% to 0.08%.

[0022] In any embodiment of the second aspect, modified groups are dispersed throughout the entire thickness direction of the positive electrode active layer.

[0023] In any embodiment of the second aspect, the positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0024] In any embodiment of the second aspect, the positive electrode active material comprises a polyanionic compound.

[0025] In any embodiment of the second aspect, the positive electrode active material includes carbon-coated sodium iron phosphate pyrophosphate or sodium iron phosphate.

[0026] A third aspect of this application provides a method for preparing a positive electrode sheet. The method includes: coating a positive electrode slurry onto a positive electrode current collector, drying and cold pressing to obtain the positive electrode sheet. The positive electrode slurry includes a positive electrode material. The method further includes a process for preparing the positive electrode material, which includes: mixing a positive electrode active material with a modifier to coat the particle surface of the positive electrode active material. The modifier includes a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

[0027] Existing technologies typically address battery gas generation by adding electrode film-forming agents to the electrolyte. The aforementioned preparation method employs a different approach, focusing on the modification of the cathode material. By coating the surface of the cathode active material, first and second modifying groups are introduced into the cathode active layer, distributing the modifier throughout the entire layer. This improves the stability of the CEI film, effectively protecting the cathode, reducing the likelihood of side reactions on the cathode active material surface, and inhibiting gas generation from electrolyte solvent oxidation and decomposition. Simultaneously, the chemical reaction consumes impurity water, effectively reducing the water content in the cathode active material and electrolyte, thus minimizing water reduction gas generation. Furthermore, this preparation method is simple to operate and easy to implement, making it suitable for industrial production.

[0028] In any implementation of the third aspect, R 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

[0029] In any embodiment of the third aspect, the modifier includes one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

[0030] In any embodiment of the third aspect, the mass ratio of the modifier to the positive electrode active material is 0.1:100 to 1:100.

[0031] Within the aforementioned mass ratio range, sufficient modifier dosage is beneficial for the uniformity of modifier film formation on the surface of positive electrode active material particles, while avoiding the adverse effects of excessive modifier coating. Adding too much modifier results in an excessively thick coating layer, which is detrimental to the diffusion of active ions during the insertion / extraction process. Furthermore, excessive primary modifier groups remaining in the positive electrode active layer may react with residual water in the electrolyte to produce silanol (gaseous) or decompose to generate gas during charge-discharge cycles.

[0032] In any embodiment of the third aspect, the positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

[0033] In any embodiment of the third aspect, the positive electrode active material includes a polyanionic compound.

[0034] In any embodiment of the third aspect, the polyanionic compound includes carbon-coated sodium iron pyrophosphate or carbon-coated sodium iron phosphate.

[0035] In any embodiment of the third aspect, the positive electrode active material and the modifier are mixed in a solvent-free manner. In any embodiment of the third aspect, the modifier is coated onto the particle surface of the positive electrode active material by fluidized bed spray coating or mechanical mixing coating.

[0036] In any embodiment of the third aspect, a solvent is added when the positive electrode active material and the modifier are mixed to form a slurry, wherein the solvent includes one or more of N-methylpyrrolidone, ethanol, and methanol.

[0037] In any embodiment of the third aspect, the solid content of the slurry is 10% to 40%.

[0038] The fourth aspect of this application provides a battery device including a battery cell in any embodiment of the first aspect of this application.

[0039] Another aspect of this application provides an electrical device, including a battery cell or a battery device, wherein the battery cell includes the battery cell in any embodiment of the first aspect of this application, and the battery device includes the battery device provided in the fourth aspect of this application. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 Transmission electron microscope (TEM) image and EDS image of the cathode material prepared in Example 1 of this application.

[0042] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0043] Figure 3 yes Figure 2 An exploded view of a battery cell according to one embodiment of this application is shown.

[0044] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0045] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0046] Figure 6 yes Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0047] Figure 7This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0048] The accompanying drawings are not drawn to scale.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0051] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0052] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode material, its preparation method, the positive electrode sheet, the battery cell, the battery device, and the power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0053] The "range" disclosed in this application is defined by 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 a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, 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 a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" 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 "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0055] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0056] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may 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.

[0057] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0058] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0059] During the initial charge and discharge cycle, the electrolyte components come into contact with the surface of the positive electrode active material to form a passivation film, namely the positive electrode electrolyte interface film (CEI film). Since the CEI film is unstable during charge and discharge cycles, the electrolyte components undergo significant oxidation and gas generation, and the positive electrode active material is also susceptible to HF corrosion. Furthermore, water is unavoidable inside the battery. Not only may the electrolyte system contain highly hygroscopic components, but water molecules are also easily adsorbed into the micropores of porous electrode materials. Trace amounts of water remaining in the electrodes can easily lead to side reactions. For example, in lithium-ion batteries, it can react with lithium salts at the interface or in the electrolyte, resulting in gas generation; or in batteries without a negative electrode (sodium metal), the electrolyte solvent can be reduced by the sodium metal of the negative electrode to generate hydrogen gas, leading to a series of safety issues such as short circuits and thermal runaway in the battery cell, which is particularly evident during high-temperature storage or high-voltage cycling.

[0060] To address the problem of gas generation from the side reaction between the electrolyte and the positive electrode, a first embodiment of this application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector. The positive electrode active layer comprises a positive electrode active material and modifying groups. The modifying groups include a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

[0061] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0062] The positive electrode active layer of the positive electrode sheet of this application includes the aforementioned modified groups, and these modified groups are not only located on the surface of the positive electrode active layer but are dispersed throughout the entire thickness direction of the positive electrode active layer. The synergistic effect of the first and second modified groups can improve the stability of the interfacial film and thus reduce gas generation. On the one hand, the first modified group has a lower oxidation potential and preferentially undergoes oxidation compared to the electrolyte solvent, thereby participating in the formation of the CEI film on the surface of the positive electrode active layer. By complexing with the transition metal ions of the positive electrode active material, the first modified group can form a more stable CEI film, which can slow down the degree of oxidation of the electrolyte components and reduce the catalytic decomposition of the electrolyte components by the active sites on the surface of the positive electrode active layer, thus inhibiting gas generation. On the other hand, the second modified group can react with water, consuming trace amounts of water in the electrolyte neutralized by the positive electrode sheet, reducing HF generation, and also mitigating the gas generation problem caused by side reactions at the electrode-electrolyte interface.

[0063] Especially in high-temperature environments, increased temperature accelerates side reactions at the electrolyte / electrode interface. The aforementioned modified groups can suppress the intense gas generation at high temperatures. Simultaneously, they protect the positive electrode active material, reduce electrolyte decomposition, and decrease the loss of negative electrode active ions, thereby improving the cycle life of the battery cell. Furthermore, the reversible storage capacity of the battery cell is also significantly improved.

[0064] The first and second modifying groups mentioned above can be obtained by testing using the following methods:

[0065] First, the positive electrode sheet is thoroughly cleaned with dimethyl carbonate (DMC). After drying the positive electrode sheet, a sufficient amount of powder is scraped off from the surface of the positive electrode active layer. The element types are tested by ICP-OES (Inductively Coupled Plasma Emission Spectroscopy) and the functional groups are tested by FTIR (Fourier Transform Infrared Spectroscopy) to determine the first and second modified functional groups. Alternatively, X-ray photoelectron spectroscopy (XPS) can be used to determine the Si-O bond and the connection relationship between the first and second modified functional groups.

[0066] In some embodiments, R in the second modifying group 1 R 2 R 3 Each group can independently include methyl, ethyl, n-propyl, or isopropyl groups. For example, trimethylsilyl groups and triethylsilyl groups can react with water, thereby suppressing the production of hydrogen gas and improving battery safety.

[0067] In some embodiments, the substance providing the modifying group includes one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

[0068] In a single battery cell, the actual measured silicon content is significantly lower than the initial addition ratio due to oxidation or reaction of the modifier with water; however, silicon is still present after the reaction. In some embodiments, the mass content of silicon in the positive electrode active layer is 0.005% to 0.1%, optionally 0.008% to 0.08%.

[0069] The determination of the mass content of silicon in the positive electrode active layer can be performed using methods and equipment known in the art, such as referring to the EPA 6010D-2014 standard. Specifically, ICP-OES (elemental analysis-inductively coupled plasma atomic emission spectrometry) can be used. First, the positive electrode sheet is thoroughly cleaned with dimethyl carbonate (DMC), and after drying, a sufficient amount of powder is scraped off from the surface of the positive electrode active layer. The powder is then digested into a liquid with a strong acid, and the liquid is introduced into the ICP light source by atomization. The gaseous atoms to be measured are further ionized and excited in a strong magnetic field, and then recover from the excited state to the ground state. During the above process, energy is released and recorded as different characteristic spectral lines for trace element quantitative analysis.

[0070] In some embodiments, the positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. These positive electrode active materials are commonly used positive electrode material systems in lithium / sodium battery cells, and they generally suffer from side reactions with the electrolyte, especially under high-voltage cycling or high-temperature storage conditions, leading to decreased CEI film stability, accelerated electrolyte oxidation and decomposition, and consequently, severe gas production. Introducing a first modifying group and a second modifying group into the positive electrode active layer is beneficial for constructing a more stable CEI film, better maintaining the number of surface active sites and the overall structural integrity of the positive electrode active material, and suppressing side reactions between the positive electrode active material and the electrolyte, thereby inhibiting gas production.

[0071] In some embodiments, the battery cell is a sodium-ion battery, and the positive electrode active material can be any positive electrode active material known in the art for use in sodium-ion batteries. As examples, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc., and other conventional materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0072] For example, as an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0073] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, and tetrahedral structures. A class of compounds with an anionic unit. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, and Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+A class of compounds and optional halogen anions. Y can be at least one of P, S, and Si, and n represents the valence state of (YO4) n- ; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents the valence state of (ZO y ); m+ The halogen can be at least one of F, Cl, and Br. The polyanionic compound is, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM’PO4F (M’ is one or several of V, Fe, Mn, and Ni), and at least one of

[0074] As an optional technical solution of this application, the polyanionic compound can be , where the A element represents an alkali metal element that doped and replaced the Na element, the M element represents a metal element that replaced the V element, the D element represents a doping element that replaced the P element, the Q element represents a doping element that replaced the F element, the D element includes at least one of Si and S, and the Q element includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, the A element includes at least one of K and Li; the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0075] As an optional technical solution of this application, the polyanionic compound can be Na x R y (PO4)2P2O7, where x = 3.5 to 4.5, y = 2.75 to 3.25, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0076] As an optional technical solution of this application, the polyanionic compound can be ; where 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0077] In some embodiments, the aforementioned sodium transition metal oxides, polyanionic compounds, and Prussian blue-like compounds have a carbon coating layer on their surface. When a carbon coating layer is present, the modified groups are also dispersed within the carbon coating layer due to its porosity.

[0078] In some embodiments, the positive electrode active material includes a polyanionic compound; optionally, the polyanionic compound includes carbon-coated sodium iron pyrophosphate. Alternatively, carbon-coated sodium iron phosphate (NaFePO4 / C) can be used. Polyanionic compounds possess a stable sodium storage framework, and the tetrahedral anionic units, through a three-dimensional network structure formed by strong covalent bonds, provide abundant ion diffusion channels. They generally exhibit good cycle performance and safety. Sodium iron phosphate pyrophosphate and sodium iron phosphate are among the more outstanding electrochemical options.

[0079] Prussian blue compounds can contain sodium ions, transition metal ions, and cyanide ions. A class of compounds. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example,... Where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0080] In some embodiments, the positive electrode active material includes at least one of sodium-containing layered oxides, polyanionic sodium compounds, and Prussian blue sodium compounds.

[0081] In some embodiments, the sodium-containing layered oxide is an iron-manganese layered oxide, specifically including at least one of nickel-iron-manganese layered oxide and copper-iron-manganese layered oxide.

[0082] During the charging and discharging process, the battery produces active ions (Na+). + Due to the intercalation and deintercalation of Na, the molar content of Na varies when the battery is discharged to different states. In the examples of positive electrode active materials in this application, the molar content of Na refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Na will change after charge-discharge cycles.

[0083] In the examples of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of oxygen will fluctuate.

[0084] When the battery cell is a lithium-ion battery cell, as an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0085] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0086] In some embodiments, the positive electrode active layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0087] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0089] [Preparation method of positive electrode sheet]

[0090] The second embodiment of this application provides a method for preparing a positive electrode sheet. The method includes: coating a positive electrode slurry onto a positive electrode current collector, drying and cold pressing to obtain the positive electrode sheet. The positive electrode slurry includes a positive electrode material. The method further includes a process for preparing the positive electrode material, which includes: mixing a positive electrode active material with a modifier to coat the particle surface of the positive electrode active material with the modifier. The modifier includes a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

[0091] Existing technologies typically address battery gas generation by adding electrode film-forming agents to the electrolyte. The aforementioned preparation method employs a different approach, focusing on the modification of the cathode material. By coating the surface of the cathode active material, first and second modifying groups are introduced into the cathode active layer, distributing the modifier throughout the entire layer. This improves the stability of the CEI film, effectively protecting the cathode, reducing the likelihood of side reactions on the cathode active material surface, and inhibiting gas generation from electrolyte solvent oxidation and decomposition. Simultaneously, the chemical reaction consumes impurity water, effectively reducing the water content in the cathode active material and electrolyte, thus minimizing water reduction gas generation. Furthermore, this preparation method is simple to operate and easy to implement, making it suitable for industrial production.

[0092] In some embodiments, R in the second modifying group 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

[0093] In some embodiments, the modifier includes one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate. These modifiers are typically used as film-forming agents for the positive / negative electrodes and do not react with the electrode materials. When the modifier is mixed with the positive electrode active material, it can form a uniform film on the surface of the positive electrode active material. Specifically, the first modifying group reacts with trace amounts of water in the positive electrode active material, while the second modifying group and a small portion of the unreacted first modifying group can also stably coat the surface of the positive electrode active material particles during subsequent preparation of the positive electrode slurry and coating processes.

[0094] In some embodiments, the mass ratio of the modifier to the positive electrode active material is 0.1:100 to 1:100. Within this range, the amount of modifier is sufficient, which is beneficial to the uniformity of the film formed by the modifier on the surface of the positive electrode active material particles, while avoiding the adverse effects of excessive modifier coating. Adding too much modifier results in an excessively thick coating layer, which is not conducive to the diffusion of active ions during the insertion / extraction process. Furthermore, too many first modified groups remain in the positive electrode active layer, which may react with residual water in the electrolyte to produce silanol (gaseous) or decompose to produce gas during charge-discharge cycles.

[0095] The above preparation method can be widely applied to various positive electrode active systems, achieving significant results and providing ample protection for the positive electrode active material. In some embodiments, the positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. Further selection of the positive electrode active material can be referred to the above content and will not be elaborated here.

[0096] In some embodiments, the positive electrode active material includes a polyanionic compound, which may be carbon-coated sodium iron phosphate pyrophosphate or carbon-coated sodium iron phosphate. Among various positive electrode active materials for sodium battery cells, polyanionic compounds exhibit high structural stability and excellent cycle performance. Among these, carbon-coated sodium iron phosphate pyrophosphate or sodium iron phosphate has a comparative advantage in ion transport properties and has broad application prospects.

[0097] In some embodiments, the positive electrode active material and the modifier are mixed in a solvent-free manner. Solvent-free mixing is safer and simpler.

[0098] In some embodiments, fluidized bed spray coating or mechanical mixing coating can be used to coat the modifier onto the surface of the positive electrode active material particles. These methods are well-known to those skilled in the art and can be performed using conventional operating procedures; therefore, they will not be elaborated upon here. The key is to achieve a relatively thin and uniform coating of the modifier onto the surface of the positive electrode active material particles. It should be noted that "coating onto the surface of the positive electrode active material particles" does not imply a clear interface between the modifier and the particle surface. Because the surface of the positive electrode active material has pores, or its carbon coating layer has pores, the modifier can penetrate these pores to form a surface coating on the positive electrode active material. For details, please refer to [reference needed]. Figure 1 The results are shown.

[0099] In some embodiments, a solvent is added when mixing the positive electrode active material and the modifier to form a slurry. The solvent includes one or more of NMP, ethanol, and methanol. Both the modifier and the positive electrode active material can dissolve quickly in the solvent, allowing for uniform mixing and good volatility, which facilitates drying.

[0100] In some embodiments, the solid content of the slurry is 10% to 40%, which is beneficial for a more uniform distribution of the modifier and the positive electrode active material.

[0101] [Battery cell]

[0102] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery that can be used again after being discharged by recharging to activate the active materials.

[0103] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0104] A single battery cell typically includes an electrode assembly. This assembly comprises a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of the battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0105] To effectively suppress gas generation inside battery cells, a third embodiment of this application provides a battery cell including a positive electrode, an electrolyte, and a negative electrode. The positive electrode includes a positive active layer, wherein the positive active layer includes a positive active material and modifying groups. The modifying groups include a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

[0106] When the positive electrode active layer includes a first modifying group and a second modifying group, the first modifying group can participate in the formation of a more stable CEI film, reducing the probability of side reactions between the positive electrode active material surface and the electrolyte, leading to gas generation. The second modifying group can use chemical reactions to reduce the water content in the positive electrode sheet and the electrolyte, inhibiting HF generation and reducing the degree of side reactions and gas generation at the interface film, thereby achieving the effect of suppressing gas generation in individual battery cells and improving safety during use.

[0107] In the battery cell described above, the positive electrode can be any positive electrode provided in the first embodiment, which will not be elaborated further here.

[0108] Electrolyte

[0109] In some embodiments, the electrolyte includes an organic solvent, which includes one or more of ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

[0110] Sodium ions have a larger radius and mass compared to lithium ions. Therefore, there are significant differences between sodium-ion and lithium-ion battery cells in terms of the phase transition mechanism of active ion insertion / extraction in electrode materials and the interfacial reaction mechanism. Furthermore, sodium exhibits higher electrochemical activity than lithium. On the sodium metal surface of the negative electrode, whether it's the catalytic decomposition or electrochemical reaction of the electrolyte solvent, or the reduction of trace water molecules in the electrolyte by sodium metal, there will be vigorous and continuous gas release. Among the aforementioned organic solvents, ether solvents show good electrochemical compatibility with the negative electrode of sodium-ion battery cells.

[0111] In some embodiments, the ether solvent includes one or more of cyclic ethers and chain ethers, wherein the cyclic ethers include cyclic ethers having 4 to 8 carbon atoms, and the chain ethers include chain ethers having 4 to 10 carbon atoms.

[0112] Ether solvents can modulate the sodium ion deposition morphology by participating in SEI film formation, obtaining a thin and dense inorganic SEI film, thereby inhibiting sodium dendrite growth. However, ether solvents have a relatively low oxidation window, making them prone to oxidation at the CEI film, and they are also highly volatile, easily generating gas. By modifying the positive electrode active material with modified groups, the degree of oxidation of ether solvents can be significantly reduced, thus decreasing the amount of gas generated by ether solvent oxidation.

[0113] In some embodiments, the ether solvent includes fluorinated ether solvents, such as 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The introduction of fluorine can lower the HOMO and LUMO energies of the molecule, thus fluorinated ethers exhibit higher oxidative stability compared to their non-fluorinated counterparts. In addition, fluorinated ether solvents can also optimize the electrode-electrolyte interfacial compatibility.

[0114] In some embodiments, the cyclic ether comprises one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4-methyl-1,3-dioxolane. Cyclic ethers, as weakly soluble solvents, can provide inorganic SEI films with higher stability and mechanical strength.

[0115] In some embodiments, the chain ether includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, and diethylene glycol dimethyl ether. The chain ether solvent has low viscosity and strong solvation ability with sodium ions, which is beneficial for improving ionic conductivity.

[0116] In some embodiments, the electrolyte salt may be selected from at least one of sodium perchlorate (NaClO4), sodium hexafluorophosphate (NaPF6), sodium trifluoromethanesulfonate (NaCF3SO3), and sodium bis(trifluoromethanesulfonyl)imide [NaN(SO2CF3)2, NaTFSI].

[0117] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0118] [Negative electrode plate]

[0119] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative current collector.

[0120] As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0121] As an example, the negative electrode sheet may include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0122] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0123] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for battery cells may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0124] In some embodiments, the negative electrode can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0125] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0126] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0127] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0128] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0129] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0130] During long-term charge-discharge cycles, the negative electrode plate undergoes hard expansion due to the embedding of active ions in the negative electrode active material, and the mutual compression between the electrodes increases the internal stress of the battery.

[0131] Therefore, in some embodiments, the negative electrode sheet is a negative current collector or a negative current collector with a conductive layer on its surface. Since no active material is provided on the negative electrode side, and only a negative current collector or a negative current collector with a conductive layer on its surface is provided, there is no hard expansion caused by the volume expansion of the negative electrode active material in the negative electrode film layer. This effectively reduces the breakage failure problem and safety risks caused by the hard expansion of the electrode sheet.

[0132] The conductive layer helps reduce the overpotential required for sodium deposition during charging and improves the uniformity of active ion deposition after the first charge and discharge. In some embodiments, the conductive layer includes a conductive agent selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the negative electrode sheet can also be prepared by dispersing the conductive agent, binder and other arbitrary additives in a solvent to form a conductive slurry, then coating the conductive slurry onto the negative current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0134] [Isolation Component]

[0135] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0136] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0137] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0138] [Structure of the electrode assembly]

[0139] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0140] In some implementations, the electrode assembly is a stacked structure.

[0141] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0142] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0143] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0144] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0145] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0146] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0147] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0148] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0149] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0150] In some embodiments, the housing includes an end cap and a shell, the shell having an opening, and the end cap covering the opening. The shell may have one or more openings. The end cap may also be provided one or more times. In some embodiments, the shell has at least one electrode terminal, which is electrically connected to a tab. The electrode terminal may be directly connected to the tab or indirectly connected to the tab via a current collector. The electrode terminal may be located on the end cap or on the shell.

[0151] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0152] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0153] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0154] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0155] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0156] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0157] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0158] Figure 2 The example shown is a square-structured battery cell 5.

[0159] In some implementations, refer to Figure 3 The outer casing may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 via a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0160] [Battery Device]

[0161] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0162] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0163] As an example, a battery cell assembly can be a battery module, which consists of multiple battery cells arranged and fixed together to form a single module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0164] Figure 4 This is battery module 4 as an example. (See reference...) Figure 4 In the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0165] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0166] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0167] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module into the housing. Alternatively, the battery cell assembly can be housed in a housing by directly fixing multiple battery cells to the housing.

[0168] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0169] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0170] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0171] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0172] The technical solutions described in this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft. As for the aforementioned electrical devices, individual battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0173] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0174] [Example]

[0175] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0176] Example 1

[0177] Preparation of the positive electrode material: The powder raw material for the positive electrode active material is carbon-coated sodium iron pyrophosphate (represented as NFPP / C in Table 1). A solvent-free coating method is used. Under a pressure of 0.4 MPa, the carbon-coated sodium iron pyrophosphate is fluidized in a fluidized bed. The modifier tris(trimethylsilane) phosphate is atomized through a spray nozzle and contacts the fluidized powder raw material to form a film. The amount of positive electrode active material powder raw material used in a single spray coating is 100... The mass ratio of the modifier to the powder raw material of the positive electrode active material (denoted as a in Table 1) is 0.5:100, and the spraying speed is 0.5 kg. g / s; After the liquid spraying is complete, continue to introduce air for mixing for 30 minutes before discharging to obtain the positive electrode material. The positive electrode material is then tested, including... Figure 1 The left image shows a TEM image of the cathode material. Figure 1The right figure shows the EDS diagram of the cathode material. It can be seen that the surface layer of the cathode active material containing the carbon coating layer (corresponding to the left of the dashed line) has Si elements uniformly dispersed, which proves that the tris(trimethylsilane) phosphate of this application is coated on the NFPP / C surface.

[0178] Preparation of the positive electrode sheet: The positive electrode material prepared according to the above method is thoroughly mixed with conductive carbon black and binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) at a mass ratio of 90:5:5 to form a uniform positive electrode slurry. The positive electrode slurry is then coated on both sides of an aluminum foil with a primer coating, wherein the thickness of the aluminum foil with the primer coating is 15 μm. After drying, cold pressing, and die cutting, a positive electrode sheet with a thickness of 160 μm is obtained, wherein the coating weight of the positive electrode active layer of the positive electrode sheet is 200 mg / 1540.25 mm. 2 .

[0179] Preparation of negative electrode sheet: The conductive agent single-walled carbon nanotubes and the binder sodium carboxymethyl cellulose are dispersed in an aqueous solution at a mass ratio of 1:1, wherein the mass ratio of conductive agent to water is 1:200. The conductive slurry is continuously stirred to form a conductive slurry. The conductive slurry is then coated on a copper foil that serves as the negative electrode current collector. After drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0180] Preparation of the separator membrane: with a thickness of 20 A polyethylene film with a diameter of μm is used as a separator.

[0181] The electrolyte consists of a solvent and a sodium salt. The solvent is ethylene glycol dimethyl ether (DME) and ethylene glycol diethyl ether (DEE) in a mass ratio of 1:1. The sodium salt is NaPF6, and the concentration of sodium salt in the electrolyte is 1.0 mol / L.

[0182] The electrodes and separators prepared in the above steps are wound into a dry cell in the order of positive electrode, separator, negative electrode, and separator. Then, the electrolyte is added to form a soft-pack battery.

[0183] Example 2

[0184] The only difference between this embodiment and Embodiment 1 is that, in the preparation process of the positive electrode material, the mass ratio between the modifier and the powder raw material of the positive electrode active material is 0.1:100;

[0185] The remaining setup and preparation methods are the same as in Example 1.

[0186] Example 3

[0187] The only difference between this embodiment and Embodiment 1 is that in the preparation process of the positive electrode material, the mass ratio between the modifier and the powder raw material of the positive electrode active material is 1:100.

[0188] The remaining setup and preparation methods are the same as in Example 1.

[0189] Example 4

[0190] The only difference between this embodiment and Embodiment 1 is that in the preparation process of the positive electrode material, the mass ratio between the modifier and the powder raw material of the positive electrode active material is 2:100.

[0191] The remaining setup and preparation methods are the same as in Example 1.

[0192] Example 5

[0193] The only difference between this embodiment and Example 1 is that in the preparation of the positive electrode material, tris(trimethylsilane) phosphite is used as the modifier;

[0194] The remaining setup and preparation methods are the same as in Example 1.

[0195] Example 6

[0196] The only difference between this embodiment and Embodiment 1 is that in the preparation of the positive electrode material, tris(trimethylsilane)borate ester is used as the modifier;

[0197] The remaining setup and preparation methods are the same as in Example 1.

[0198] Example 7

[0199] The only difference between this embodiment and Embodiment 1 is that in the preparation of the positive electrode material, tris(triethylsilane) phosphate is used as the modifier;

[0200] The remaining setup and preparation methods are the same as in Example 1.

[0201] Example 8

[0202] The only difference between this embodiment and Embodiment 1 is that in the preparation process of the positive electrode material, the powder raw material of the positive electrode active material is carbon-coated sodium iron phosphate (represented as NFP / C in Table 1).

[0203] The remaining setup and preparation methods are the same as in Example 1.

[0204] Example 9

[0205] The only difference between this embodiment and Embodiment 1 is that, in the preparation process of the positive electrode material, the powder raw material for the positive electrode active material is NaNi. 0.2 Fe 0.3 Mn 0.4 Cu0.1 O2 (represented as NNFCM in Table 1);

[0206] The remaining setup and preparation methods are the same as in Example 1.

[0207] Example 10

[0208] The only difference between this embodiment and Embodiment 1 is that:

[0209] In the preparation process of the cathode material, the powder raw material for the cathode active material is spinel-type LiNi. 0.5 Mn 1.5 O4 (represented as LNM in Table 1); during the preparation of the negative electrode sheet, graphite is used as the conductive agent; and the solvent of the electrolyte includes ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 3:5:2, and NaPF6 is still used as the sodium salt, with a sodium salt concentration of 1.0 mol / L in the electrolyte.

[0210] The remaining setup and preparation methods are the same as in Example 1.

[0211] Example 11

[0212] The only difference between this embodiment and Embodiment 1 is that: in the preparation of the positive electrode material, the modifier and solvent are mixed and coated, and a mechanical high-speed mixing spray method is used. Specifically, the modifier tris(trimethylsilane) phosphate liquid is atomized through a spray head and sprayed from the top of the reaction tank. The bottom of the reaction tank is highly mixed by stirring, thereby achieving high mixing and contact between the liquid and powder raw materials to form a film.

[0213] The remaining setup and preparation methods are the same as in Example 1.

[0214] Example 12

[0215] The only difference between this embodiment and Embodiment 1 is that the positive electrode material is prepared by electrode spraying, thereby achieving the coating of the positive electrode active material. Tris(trimethylsilane) phosphate is atomized and sprayed out through a spray head to uniformly coat the electrode surface to form a film.

[0216] The remaining setup and preparation methods are the same as in Example 1.

[0217] In Comparative Examples 1-4, no modifier was used to modify the positive electrode active material, serving as a control.

[0218] Comparative Example 1

[0219] The only difference between this comparative example and Example 1 is that tris(trimethylsilane)phosphate is not used to modify the carbon-coated sodium iron pyrophosphate; all other settings and preparation methods are the same as in Example 1.

[0220] Comparative Example 2

[0221] The only difference between this comparative example and Example 8 is that tris(trimethylsilane)phosphate is not used to modify the carbon-coated sodium iron phosphate; all other settings and preparation methods are the same as in Example 8.

[0222] Comparative Example 3

[0223] The only difference between this comparative example and Example 9 is that tris(trimethylsilane)phosphate is not used for NaNi 0.2 Fe 0.3 Mn 0.4 Cu 0.1 O2; Modification was performed, and the remaining settings and preparation methods were the same as in Example 9.

[0224] Comparative Example 4

[0225] The only difference between this comparative example and Example 10 is that tris(trimethylsilane)phosphate is not used for spinel-type LiNi. 0.5 Mn 1.5 O4 was modified, and the rest of the settings and preparation methods were the same as in Example 10.

[0226] [Testing Method]

[0227] The mass content of silicon in the positive electrode active layer of the above embodiments can be tested using ICP-OES (elemental analysis-inductively coupled plasma atomic emission spectrometry). First, the positive electrode sheet is thoroughly cleaned with dimethyl carbonate (DMC), and after drying, a sufficient amount of powder is scraped off from the surface of the positive electrode active layer. The powder is then digested into a liquid with a strong acid, and the liquid is introduced into the ICP light source by atomization. The gaseous atoms to be measured are further ionized and excited in a strong magnetic field, and then recover from the excited state to the ground state. During the above process, energy is released and recorded as different characteristic spectral lines. Trace element quantitative analysis is performed to obtain the mass content of Si in the positive electrode active layer.

[0228] The battery gas production performance test can be conducted through the following steps: The pouch cells from the above embodiments and comparative examples are fully charged to 3.65V at 0.33C, at which point the battery is in a 100% SOC state. The initial volume is recorded using the water displacement method. The pouch cells with gas bags are placed in a 45°C constant temperature oven. Every 5 days, the pouch cells are removed, cooled to room temperature, and the volume after storage is recorded again using the water displacement method. After testing, the cells are returned to the constant temperature oven, and the above process is repeated to measure the change in battery gas production during storage.

[0229] In this application, the gas production volume of a pouch cell stored at 45°C for 60 days at 100% SOC is used as the evaluation index for the gas production performance of the battery, with the unit being mL / Ah.

[0230] Battery storage life testing can be conducted as follows:

[0231] (1) The soft-pack batteries in the above embodiments and comparative examples were left to stand at 25°C for 30 minutes, then discharged to 1.5V with DC at 0.33C, and then left to stand at 25°C for 30 minutes.

[0232] (2) Charge at a constant current of 0.33C to 3.65V and then charge at a constant voltage until the current reaches 0.05C, and then let stand at 25°C for 30 minutes;

[0233] (3) Discharge the soft-pack battery to 1.5V at 0.33C DC, and record the capacity value of the soft-pack battery at this time as C0. C0 is the initial capacity of the soft-pack battery. Then let it stand at 25°C for 30 minutes.

[0234] (4) Let it stand for 10 minutes, charge it at a constant current of 0.33C0 to 3.65V and then charge it at a constant voltage to 0.05C0. Recharge the soft pack battery to 100% SOC and let it stand for 1 hour.

[0235] (5) Store the soft pack battery in a 45°C constant temperature oven. Take it out every 10 days and record the current reversible capacity of the soft pack battery according to the operation of steps (1) to (4). You can find out how the remaining reversible capacity of the battery changes with the storage time under the 45°C storage condition.

[0236] In this application, the reversible capacity retention rate of a pouch cell stored at 45°C for 60 days at 100% SOC is used as the evaluation index for battery storage life. Let C be the reversible capacity measured after 60 days of storage at 45°C for a 100% SOC pouch cell. Correspondingly, the reversible capacity retention rate after 60 days of storage at 45°C is R = C / C0 × 100%.

[0237] The following parameters from the embodiments and comparative examples obtained by the above methods are recorded in Table 1: the mass content of Si element in the positive electrode active layer (hereinafter referred to as: mass content of Si in the positive electrode active layer), the gas production volume of the pouch battery stored at 45°C for 60 days at 100% SOC (hereinafter referred to as: gas production volume after 60 days of storage at 45°C), and the remaining reversible capacity retention rate of the pouch battery stored at 45°C for 60 days at 100% SOC (hereinafter referred to as: reversible capacity retention rate after 60 days of storage at 45°C).

[0238] Table 1

[0239]

[0240] The difference between Examples 1 to 4 lies in the mass ratio of the modifier tris(trimethylsilane) phosphate to the positive electrode active material during the preparation of the positive electrode material. According to the data in Table 1, compared to Comparative Example 1, where the surface of the positive electrode active material NFPP / C was not coated with the modifier tris(trimethylsilane) phosphate, Examples 1 to 4 showed significant improvements in both battery gas generation and reversible capacity retention. Furthermore, with the increase of the mass ratio of the two, the trends in battery gas generation and reversible capacity retention were non-monotonic; the volume of battery gas generation first decreased and then increased, while the reversible capacity retention first increased and then decreased. This may be because excessive tris(trimethylsilane) phosphate remaining in the positive electrode active layer could react with residual water in the electrolyte to generate more trimethylsilanol gas, or it might decompose itself to produce gas.

[0241] Examples 5 to 7 used different modifiers than Example 1. All modifiers used could provide the first and second modifying groups, and the mass ratio of the modifier to the positive electrode active material and other settings were kept the same. Tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, and tris(triethylsilane) phosphate all have the effect of improving battery gas production and storage life. However, under the premise that the mass ratio of the modifier to the positive electrode active material is the same, the improvement degree of the above modifiers is slightly lower than that of tris(trimethylsilane) phosphate.

[0242] Examples 8 to 10 used different positive electrode active materials than Example 1. The mass ratio of modifier to positive electrode active material and other settings remained the same. For cases where different positive electrode active materials were not coated, see Comparative Examples 1 to 4. Comparing the results of the above examples and comparative examples, it can be found that whether it is polyanionic sodium-ion positive electrode material, nickel-cobalt-manganese ternary positive electrode material, or nickel-manganese-based spinel positive electrode material, after modification with tris(trimethylsilane) phosphate, the side reactions between the positive electrode material and the electrolyte were significantly suppressed, improving the battery gas generation problem and increasing the reversible capacity retention rate of the battery.

[0243] Examples 11 and 12 respectively employed high-speed mixing spray and electrode spraying methods to coat and modify the positive electrode active material. Compared with the fluidized bed spray coating method, these methods can also achieve good results in controlling the gas production volume of the battery and extending the battery storage life.

[0244] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising a positive electrode, an electrolyte, and a negative electrode, wherein the positive electrode includes a positive current collector and a positive active layer disposed on at least one side of the positive current collector, wherein, The positive electrode active layer includes a positive electrode active material and modifying groups. The modifying groups include a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

2. The battery cell according to claim 1, wherein, R 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

3. The battery cell according to claim 1 or 2, wherein, The substances providing the modifying groups include one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

4. The battery cell according to any one of claims 1 to 3, wherein, The positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

5. The battery cell according to claim 4, wherein, The positive electrode active material includes a polyanionic compound.

6. The battery cell according to claim 5, wherein, The polyanionic compound includes carbon-coated sodium iron pyrophosphate or carbon-coated sodium iron phosphate.

7. The battery cell according to any one of claims 1 to 6, wherein, The modified groups are dispersed throughout the entire thickness direction of the positive electrode active layer.

8. The battery cell according to any one of claims 1 to 7, wherein, The electrolyte includes an organic solvent, which includes one or more of the following: ether solvents, nitrile solvents, carbonate solvents, carboxylic acid ester solvents, and sulfone solvents.

9. The battery cell according to claim 8, wherein, The ether solvent includes one or more of cyclic ethers and chain ethers, wherein the cyclic ethers include cyclic ethers with 4 to 8 carbon atoms, and the chain ethers include chain ethers with 4 to 10 carbon atoms.

10. The battery cell according to claim 9, wherein, The ether solvent includes fluorinated ether solvents, which include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and / or The cyclic ether comprises one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4-methyl-1,3-dioxolane; and / or The chain ethers include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, and diethylene glycol dimethyl ether.

11. The battery cell according to any one of claims 1 to 10, wherein, The negative electrode sheet is a negative current collector or a negative current collector with a conductive layer on its surface.

12. A positive electrode sheet, comprising a positive current collector and a positive active layer disposed on at least one side of the positive current collector, wherein, The positive electrode active layer includes a positive electrode active material and modifying groups. The modifying groups include a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

13. The positive electrode sheet according to claim 12, wherein, R 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

14. The positive electrode sheet according to claim 12 or 13, wherein, The substances providing the modifying groups include one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

15. The positive electrode sheet according to any one of claims 12 to 14, wherein, The silicon content in the positive electrode active layer is 0.005% to 0.1% by mass, and can be selected as 0.008% to 0.08%.

16. The positive electrode sheet according to any one of claims 12 to 15, wherein, The modified groups are dispersed throughout the entire thickness direction of the positive electrode active layer.

17. The positive electrode sheet according to any one of claims 12 to 16, wherein, The positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

18. The positive electrode sheet according to claim 17, wherein, The positive electrode active material includes a polyanionic compound.

19. The positive electrode sheet according to claim 18, wherein, The polyanionic compound includes carbon-coated sodium iron pyrophosphate or carbon-coated sodium iron phosphate.

20. A method for preparing a positive electrode sheet, the method comprising: A positive electrode slurry is coated onto a positive electrode current collector, and after drying and cold pressing, a positive electrode sheet is obtained. The positive electrode slurry includes a positive electrode material. The preparation method further includes a process for preparing the positive electrode material, which includes: A positive electrode active material is mixed with a modifier, causing the modifier to coat the surface of the positive electrode active material particles. The modifier includes a first modifying group and a second modifying group. The first modifying group includes at least one selected from phosphate ester groups, phosphite ester groups, and borate ester groups. The second modifying group includes R... 1 R 2 R 3 Si-, where R 1 R 2 R 3 Each is independently selected from hydrogen atoms, C1-C5 alkyl groups, or C1-C5 haloalkyl groups.

21. The preparation method according to claim 20, wherein, R 1 R 2 R 3 Each can independently include methyl, ethyl, n-propyl, or isopropyl.

22. The preparation method according to claim 20 or 21, wherein, The modifier includes one or more of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, tris(triethylsilane) phosphate, and tris(triethylsilane) borate.

23. The preparation method according to any one of claims 20 to 22, wherein, The mass ratio of the modifier to the positive electrode active material is 0.1:100 to 1:

100.

24. The preparation method according to any one of claims 20 to 23, wherein, The positive electrode active material includes one or more of the following: olivine-structured lithium phosphates, lithium transition metal oxides and their respective modified compounds, sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds.

25. The preparation method according to claim 24, wherein, The positive electrode active material includes a polyanionic compound.

26. The preparation method according to claim 25, wherein, The polyanionic compound includes carbon-coated sodium iron pyrophosphate or carbon-coated sodium iron phosphate.

27. The preparation method according to any one of claims 20 to 26, wherein, The method of mixing the positive electrode active material and the modifier is solvent-free mixing.

28. The preparation method according to claim 27, wherein, The modifier is coated onto the surface of the positive electrode active material particles by fluidized bed spray coating or mechanical mixing coating.

29. The preparation method according to any one of claims 20 to 26, wherein, When the positive electrode active material and the modifier are mixed, a solvent is added to form a slurry. The solvent includes one or more of N-methylpyrrolidone, ethanol, and methanol.

30. The preparation method according to claim 29, wherein, The solid content of the slurry is 10% to 40%.

31. A battery device comprising a battery cell according to any one of claims 1 to 11.

32. An electrical device comprising a single battery cell or a battery assembly, wherein, The battery cell includes any one of claims 1 to 11, and the battery device includes the battery device of claim 31.

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