Battery cell, method for producing the same, battery device, electric device, and energy storage device

Abstract

This application relates to the field of energy storage technology, providing a battery cell and its preparation method, battery device, power consumption device, and energy storage device. The battery cell includes: an electrode assembly comprising a negative electrode, a separator, and a positive electrode stacked together; a housing containing the electrode assembly; and an electrolyte containing the electrolyte within the housing. The positive electrode includes a current collector, a base coating, and an active layer. The base coating is located between the current collector and the active layer. The interface between the current collector and the base coating has Si-O-C covalent bonds, and the interface between the base coating and the active layer has amide bonds and a three-dimensional hydrogen bond network. The beneficial effects of this application include at least: a 5-8 times increase in the peel strength of the positive electrode, and no powder shedding during a 180° peel test of the adhesive / tape.

Description

Technical Field

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

[0002] Sodium-ion battery cathodes commonly use carbon-coated aluminum foil to improve conductivity and reduce costs (e.g., NVP or layered oxide cathode systems). A typical existing formulation is: 96.2 wt% active material (NVP or similar), 0.8 wt% SP, 0.5 wt% CNT (100% solid content), and 2.5 wt% PVDF (HSV900), coated onto carbon-coated aluminum foil. While the carbon coating in the aluminum foil improves conductivity, its hydrophobic surface and low polarity result in poor compatibility with PVDF slurry. Peel strength is typically <1 N / cm, leading to easy powder shedding and detachment of the electrode after rolling, and rapid capacity decay during cycling. Existing technologies often increase the PVDF content (>4 wt%) or replace it with ordinary aluminum foil, but these methods sacrifice the conductivity and energy density of the electrode. Summary of the Invention

[0003] This application provides a battery cell and its preparation method, battery device, power supply device and energy storage device, which at least helps to improve the peeling force of the positive electrode in the battery cell.

[0004] In a first aspect, this application provides a battery cell, comprising: An electrode assembly, comprising a negative electrode, a separator, and a positive electrode stacked together; Housing, wherein the electrode assembly is located within the housing; Electrolyte, wherein the electrolyte is located within the housing; The positive electrode includes a current collector, an undercoating layer, and an active layer. The undercoating layer is located between the current collector and the active layer. The interface between the current collector and the undercoating layer has Si-OC covalent bonds, and the interface between the undercoating layer and the active layer has amide bonds and a three-dimensional hydrogen bond network.

[0005] Optionally, the interface between the base coating and the active layer also has an interlocking structure, which is formed by the interpenetration of polymer molecular chains.

[0006] Optionally, the thickness of the base coating is 0.5μm to 2μm.

[0007] Optionally, the current collector may comprise a carbon-coated aluminum foil.

[0008] Secondly, this application provides a method for preparing a battery cell, comprising: An electrode assembly is obtained, the electrode assembly comprising a negative electrode, a separator, and a positive electrode stacked together; Obtain the housing, and place the electrode assembly inside the housing; Obtain the electrolyte and inject the electrolyte into the casing; A formation process is performed to obtain battery cells; The positive electrode includes a current collector, an undercoat, and an active layer. Si-OC covalent bonds are formed between the current collector and the undercoat, and amide bonds and a three-dimensional hydrogen bond network are formed between the undercoat and the active layer.

[0009] Optionally, the method for preparing the positive electrode includes: A current collector, a positive electrode active material slurry, and sodium polyacrylate modified with a silane coupling agent are obtained. The positive electrode active material slurry includes a binder, which includes at least one of sodium polyacrylate (PAA-Na) and sodium carboxymethyl cellulose (CMC-Na). After coating the surface of the current collector with the silane coupling agent-modified sodium polyacrylate, and then drying it, a base coating is formed on the surface of the current collector. After coating the surface of the base coating with the positive electrode active material slurry, the material is dried and rolled to obtain the positive electrode sheet.

[0010] CMC-Na can provide abundant carboxyl groups (-COOH), which ionize at pH 8-9, enhancing hydrogen bonding and electrostatic interactions with the base coating. Compared to polyvinylidene fluoride (PVDF), CMC-Na has better chemical stability, avoiding electrochemical defluorination reactions.

[0011] The mechanism of the base coating is as follows: the alkoxy group (-Si(OR)3) at one end of the silane coupling agent hydrolyzes to generate silanol groups (-Si-OH), which condense with the hydroxyl groups on the carbon coating surface to form Si-OC covalent bonds; the organic functional groups at the other end (methacryloyloxy group of KH-570, amino group of KH-550) react with the carboxyl groups on the PAA-Na molecular chain to form hydrogen bonds, thereby establishing chemical bond connections between the carbon coating and the active layer. By introducing amino functional groups onto the current collector surface through the silane coupling agent, they can form amide bonds and other chemical bonds with the carboxyl groups in the binder, thus constructing chemical bond forces between the current collector and the active layer.

[0012] Optionally, the preparation method of the silane coupling agent modified sodium polyacrylate includes: The silane coupling agent is hydrolyzed in an aqueous ethanol solution to obtain a silane hydrolysate; The sodium polyacrylate aqueous solution was mixed with the silane hydrolysate and reacted to obtain the silane coupling agent modified sodium polyacrylate.

[0013] Optionally, the silane coupling agent includes at least one of γ-(methacryloyloxy)propyltrimethoxysilane and γ-aminopropyltriethoxysilane.

[0014] Optionally, the volume fraction of ethanol in the ethanol-water solution is 85% to 95%, and the pH value of the ethanol-water solution is 4 to 5.

[0015] Optionally, the sodium polyacrylate aqueous solution has a mass fraction of 0.5% to 1%.

[0016] Optionally, the reaction temperature is 70℃~90℃.

[0017] Optionally, the sodium polyacrylate has a weight-average molecular weight of 100,000 to 500,000.

[0018] Optionally, the amount of the binder is 2.5wt to 3.5wt% of the total weight of the positive electrode active material slurry.

[0019] Optionally, the adhesive may also include polyvinylidene fluoride.

[0020] Optionally, the solid content of the positive electrode active material slurry is 45% to 55%.

[0021] Thirdly, this application provides a battery device, including a battery cell as described above, or a battery cell obtained by the preparation method described above, wherein the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0022] Fourthly, this application provides an electrical device, which includes a battery device as described above, the battery device being used to provide electrical energy.

[0023] Fifthly, this application provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0024] The beneficial effects of this application are that, The positive electrode sheet prepared in this application has significantly improved peel strength and no powder shedding. After rolling, bending and cycling, the adhesion remains above 95%. The capacity, rate and cycle performance of the battery cells prepared using this positive electrode sheet are slightly improved, and the risk of increased internal resistance and short circuit can be avoided. The preparation process of the positive electrode sheet is compatible with existing coating lines, the cost will not increase significantly, and the safety is significantly improved.

[0025] The battery cells provided in this application can be widely used in battery fields requiring high energy density and long cycle life, including high-end electric vehicle battery systems, portable electronic devices, and large-scale energy storage power stations. The battery cells provided in this application can achieve large-capacity energy storage, comprehensively improving energy density, cycle life, and safety performance. They can meet the needs of long-term energy storage, achieving 4 hours or more of long-term energy storage, for example, in energy storage scenarios of 5 hours, 6 hours, and 8 hours. Long-term energy storage refers to the ability to continuously discharge at rated power for 4 hours or even longer, or to achieve large-scale, low-cost energy storage for several days or months. Attached Figure Description

[0026] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart corresponding to the method for preparing a single battery cell provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the battery device provided in the embodiments of this application; Figure 3 for Figure 2 A schematic diagram of its breakdown.

[0028] In the diagram: 100, battery cell; 10, casing; 20, electrode assembly; 11, top cover; 12, outer shell. Detailed Implementation

[0029] As the background technology shows, the current structure of sodium-ion battery cathodes mainly includes a 16-20 μm thick aluminum foil substrate, a 1-2 μm thick carbon coating, and an active layer. The preparation method mainly includes: slurry preparation (high-speed stirring) → coating → drying (80℃~120℃) → rolling. The bonding between the active layer and the carbon coating relies on physical adsorption. There is no chemical bond between the carbon layer and the slurry interface, resulting in weak adhesion and extremely low peel strength (<1N / cm). The coating is prone to peeling off and powdering. At the same time, powder shedding during rolling / bending / cycling leads to increased internal resistance and safety hazards. Simply adding binder will sacrifice capacity and conductivity. In addition, there are other problems, such as the low surface polarity of the carbon layer, poor compatibility with aqueous / organic slurries, lack of chemical anchoring, and more obvious expansion / contraction of the sodium cathode (NVP system), which exacerbates powder shedding.

[0030] Increasing the amount of PVDF (>4wt%) or replacing it with ordinary aluminum foil to improve the peel strength of the electrode sheet will sacrifice the conductivity and energy density of the electrode sheet.

[0031] Therefore, some studies have used carbon-coated aluminum foil with conductive carbon black coating on both sides as the current collector, combined with modified PVDF as the adhesive, which can improve the peel strength and energy density of the battery to a certain extent. Other studies have used conductive agent composite materials containing carbon nanotubes and / or graphene to modify the surface of carbon-coated aluminum foil, which can also improve the peel strength of the electrode sheet to a certain extent.

[0032] However, the above methods have limited effect on improving the peeling force of the electrode sheet and still cannot completely solve the problem of the peeling force of the electrode sheet.

[0033] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined. Similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple pieces" refers to two or more pieces (including two pieces).

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

[0035] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0036] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of said other elements or features. Therefore, the term "below" may cover both above and below orientation depending on the context in which the term is used, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90°, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0037] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0038] In the description of embodiments of this application, the terms "about," "approximately," "roughly," or "about" for a numerical value referring to a specific parameter include the numerical value, and those skilled in the art will understand that the deviation from the numerical value is within the acceptable tolerance of the specific parameter. For example, "about" or "about" for a numerical value may include additional numerical values ​​that are in the range of 90.0% to 110.0% of the numerical value, such as in the range of 95.0% to 105.0%, 97.5% to 102.5%, 99.0% to 101.0%, 99.5% to 100.5%, or 99.9% to 100.1%.

[0039] In the accompanying drawings corresponding to the embodiments of this application, the thickness and / or area of ​​layers, films, panels, regions, etc., are enlarged for better understanding and ease of description. Throughout the specification, the same reference numerals denote the same elements. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0040] In the description of embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and may be further included. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be an intermediate component between the two components. Conversely, when describing a component on the surface of another component, or a component "directly" on another component, or a component surface on which another component is formed or disposed, it indicates that there is no intermediate component between the two components. For simplicity and clarity, various components may be drawn at any scale. In the drawings, some components may be omitted for simplicity.

[0041] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "the component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0042] The “components” mentioned above can refer to layers, membranes, regions, parts, plates, or structures, etc.

[0043] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0044] In a first aspect, this application provides a battery cell, comprising: An electrode assembly, comprising a negative electrode, a separator, and a positive electrode stacked together; Housing, wherein the electrode assembly is located within the housing; Electrolyte, wherein the electrolyte is located within the housing; The positive electrode includes a current collector, an undercoating layer, and an active layer. The undercoating layer is located between the current collector and the active layer. The interface between the current collector and the undercoating layer has Si-OC covalent bonds, and the interface between the undercoating layer and the active layer has amide bonds and a three-dimensional hydrogen bond network.

[0045] The positive electrode sheet prepared in this application exhibits significantly improved peel strength, exceeding 5 N / cm. No powder is shed during 180° peel / tape testing. After rolling, bending, and cycling, the adhesion remains above 95%. The capacity, rate capability, and cycle performance of battery cells prepared using this positive electrode sheet are slightly improved (500-cycle retention rate greater than 92%). Furthermore, it avoids the risks of increased internal resistance and short circuits. The preparation process of the positive electrode sheet is compatible with existing coating lines, and the cost will not increase significantly (not exceeding 0.1 yuan / Wh). Safety is significantly improved (reducing the risk of increased internal resistance and short circuits).

[0046] Specifically, the base layer is anchored to the carbon coating surface through Si-OC covalent bonds, while providing abundant active functional groups such as amino and carboxyl groups. The active layer and the base layer form a continuous molecular-level transition layer at the interface, eliminating the weak area at the phase interface.

[0047] Optionally, the interface between the base coating and the active layer also has an interlocking structure, which is formed by the interpenetration of polymer molecular chains. Through the entanglement of the polymer, the molecular chains interpenetrate to form a mechanical interlock.

[0048] Optionally, the thickness of the base coating is 0.5μm to 2μm.

[0049] Optionally, the current collector may comprise a carbon-coated aluminum foil.

[0050] Secondly, this application provides a method for preparing a battery cell, such as... Figure 1 As shown, it includes: S1. Obtain an electrode assembly, the electrode assembly comprising a negative electrode, a separator, and a positive electrode stacked together; S2. Obtain the housing and place the electrode assembly inside the housing; S3. Obtain the electrolyte and inject the electrolyte into the casing; S4. Perform the formation step to obtain battery cells; The positive electrode includes a current collector, an undercoat, and an active layer. Si-OC covalent bonds are formed between the current collector and the undercoat, and amide bonds and a three-dimensional hydrogen bond network are formed between the undercoat and the active layer.

[0051] Optionally, the method for preparing the positive electrode includes: A current collector, a positive electrode active material slurry, and a silane coupling agent modified sodium polyacrylate are obtained. The positive electrode active material slurry includes a binder, which includes at least one of sodium polyacrylate and sodium carboxymethyl cellulose. After coating the surface of the current collector with the silane coupling agent-modified sodium polyacrylate, and then drying it, a base coating is formed on the surface of the current collector. After coating the surface of the base coating with the positive electrode active material slurry, the material is dried and rolled to obtain the positive electrode sheet.

[0052] Optionally, the preparation method of the silane coupling agent modified sodium polyacrylate includes: The silane coupling agent is hydrolyzed in an aqueous ethanol solution to obtain a silane hydrolysate; The sodium polyacrylate aqueous solution was mixed with the silane hydrolysate and reacted to obtain the silane coupling agent modified sodium polyacrylate.

[0053] Optionally, the silane coupling agent includes at least one of γ-(methacryloyloxy)propyltrimethoxysilane and γ-aminopropyltriethoxysilane.

[0054] Optionally, the volume fraction of ethanol in the ethanol-water solution is 85% to 95%, and the pH value of the ethanol-water solution is 4 to 5.

[0055] Optionally, the sodium polyacrylate aqueous solution has a mass fraction of 0.5% to 1%.

[0056] Optionally, the reaction temperature is 70℃~90℃.

[0057] Optionally, the sodium polyacrylate has a weight-average molecular weight of 100,000 to 500,000.

[0058] Optionally, the amount of the binder is 2.5wt to 3.5wt% of the total weight of the positive electrode active material slurry.

[0059] Optionally, the adhesive may also include polyvinylidene fluoride.

[0060] Optionally, the solid content of the positive electrode active material slurry is 45% to 55%.

[0061] Optionally, the pH value of the positive electrode active material slurry is 8-9. At this pH value, carboxyl ionization can be promoted (increasing -COO). - This enhances electrostatic and hydrogen bonding interactions, promotes the condensation of silanol groups in the base coating, and inhibits the aggregation of conductive agents.

[0062] Optionally, the preparation method of the positive electrode active material slurry includes: After mixing the positive electrode active material, conductive agent and binder, the mixture is subjected to high-speed shearing and ultrasonic dispersion to obtain a slurry with a solid content of positive electrode active material.

[0063] The high-speed shearing rotation speed is 1500rpm~3000rpm, and the ultrasonic dispersion frequency is 40kHz.

[0064] Optionally, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material. As an example, the negative electrode current collector has two opposing surfaces, and the negative electrode film layer is disposed on either or both of the opposing surfaces of the negative electrode current collector.

[0065] The negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil may include, but is not limited to, copper foil. The composite current collector may include a base layer and a metal layer located on at least one surface of the base layer. For example, the base layer can be a polymer material, including but not limited to polypropylene (PP) base layer, polyethylene terephthalate (PET) base layer, polybutylene terephthalate (PBT) base layer, polystyrene (PS) base layer, or polyethylene (PE) base layer. The material of the metal layer may include, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, or silver alloys.

[0066] The negative electrode active material can be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material can be at least one of the following materials: carbon materials and tin-based materials. The carbon material can be soft carbon or hard carbon. The tin-based material can be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other materials that can be used as negative electrode active materials in battery cells can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0067] Optionally, the negative electrode film may also include a conductive agent. 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.

[0068] Optionally, the negative electrode film layer may also include a binder. 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).

[0069] Optionally, the negative electrode film may also include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0070] The membrane material can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. This application does not impose any particular limitation on the type of membrane; for example, a porous membrane with chemical and mechanical stability can be selected.

[0071] The separator can be a single-layer thin film or a multi-layer composite thin film; there are no particular restrictions. When the separator is a multi-layer composite thin film, the materials of each layer can be the same or different; there are no particular restrictions.

[0072] In some specific examples, the separator can include polypropylene (PP) separators, polyethylene (PE) separators, PP / PE / PP three-layer composite separators, ceramic-coated separators, high-strength polymer separators, or functionalized composite separators. PP and PE separators typically have a thickness of 12μm to 25μm and a porosity of 30% to 50%, exhibiting good mechanical strength and chemical stability. Ceramic-coated separators, with a coating of ceramic materials such as Al2O3, SiO2, and TiO2 (coating thickness 2μm to 5μm) on a polyolefin-based membrane, improve high-temperature resistance (thermal shut-off temperature >160℃) and puncture resistance. High-strength polymer separators (such as polyimide PI, polyethylene terephthalate PET, and aramid nanofiber separators) possess excellent mechanical properties and high-temperature resistance. Functionalized composite separators (such as separators containing solid electrolyte coatings or sodium-loving coatings) can further enhance sodium deposition stability.

[0073] Thirdly, this application provides a battery device such as Figure 2 and Figure 3 As shown, the battery device includes the battery cell as described above, or the battery cell obtained by the preparation method described above, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0074] Specifically, the battery cell 100 includes a housing 10 and an electrode assembly 20, the electrode assembly 20 being housed within the housing 10. The housing 10 provides space for the electrode assembly 20, and the housing 10 can have various structures.

[0075] In some embodiments, the housing 10 may include a top cover 11 and a shell 12, the top cover 11 and the shell 12 covering each other, the top cover 11 and the shell 12 together defining a receiving space for accommodating the electrode assembly 20. The shell 12 may be a hollow structure with one end open, and the top cover 11 may be a plate-like structure, the top cover 11 covering the open side of the shell 12 so that the top cover 11 and the shell 12 together define the receiving space; the top cover 11 and the shell 12 may also be hollow structures with one side open, the open side of the top cover 11 covering the open side of the shell 12. Of course, the housing 10 formed by the top cover 11 and the shell 12 may be of various shapes, such as a cylinder, a cuboid, etc.

[0076] In the battery cell 100, the electrode assembly 20 can be a single electrode assembly, or there can be two or more electrode assemblies 20, which are isolated from each other by an insulating film.

[0077] Fourthly, this application provides an electrical device, which includes a battery device as described above, the battery device being used to provide electrical energy.

[0078] Electrical devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0079] Fifthly, this application provides an energy storage device, which includes a battery device as described above, the battery device being used to store electrical energy.

[0080] Energy storage devices include, but are not limited to, residential energy storage cabinets, commercial energy storage cabinets, energy storage containers, energy storage racks, energy storage power stations, energy storage battery packs, or portable energy storage systems. Energy storage devices may also include energy management systems (EMS), battery management systems (BMS), and power conversion systems (PCS).

[0081] To verify the impact of the proposed design of the undercoat and active layer on the peel strength of the positive electrode, a series of embodiments and comparative examples were designed. The following details the selection of raw materials, the preparation of the positive electrode, battery assembly, and the analysis of results.

[0082] I. The materials used in the following embodiments and comparative examples are as follows.

[0083] The positive electrode current collector is selected from carbon-coated aluminum foil.

[0084] Silane coupling agents can be selected from γ-(methacryloyloxy)propyltrimethoxysilane and γ-aminopropyltriethoxysilane.

[0085] The binder can be sodium carboxymethyl cellulose, polyvinylidene fluoride, or sodium polyacrylate with a weight average molecular weight of 100,000 to 500,000.

[0086] The diaphragm can be a conventional commercially available three-layer PP / PE / PP composite diaphragm.

[0087] The positive electrode active material is sodium vanadium phosphate (NVP), the conductive agent is conductive carbon black and carbon nanotubes, and the binder is polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose.

[0088] Both the negative electrode and the electrolyte can use conventional products and formulations.

[0089] All of the above operations that are sensitive to water and oxygen were performed in an argon atmosphere glove box, where the water and oxygen content was controlled to be below 0.5 ppm.

[0090] II. Preparation of the positive electrode sheet.

[0091] The silane coupling agent was hydrolyzed in an aqueous ethanol solution with a volume fraction of 90% and a pH value of 4-5 to obtain a silane hydrolysate. The silane hydrolysate and a sodium polyacrylate aqueous solution with a mass fraction of 0.5%~1% were mixed at a mass ratio of 1:(0.2~0.5) and reacted at 80°C to obtain silane coupling agent modified sodium polyacrylate. Sodium polyacrylate modified with silane coupling agent was coated onto the surface of carbon-coated aluminum foil and dried to form a base coating with a thickness of 0.5μm~2μm. After mixing sodium vanadium phosphate, conductive agents (such as conductive carbon black and carbon nanotubes) and binders (such as sodium carboxymethyl cellulose and polyvinylidene fluoride, or sodium polyacrylate and polyvinylidene fluoride, or sodium carboxymethyl cellulose, sodium polyacrylate and polyvinylidene fluoride), the positive electrode active material slurry with a solid content of 45% to 55% is obtained by high-speed shearing and ultrasonic dispersion. The positive electrode active material slurry is coated onto the surface of the base coating layer, dried at 120°C, and then rolled to obtain the positive electrode sheet.

[0092] The mechanism of the base coating is as follows: the alkoxy group (-Si(OR)3) at one end of the silane coupling agent hydrolyzes to generate silanol groups (-Si-OH), which condense with the hydroxyl groups on the carbon coating surface to form Si-OC covalent bonds; the organic functional groups at the other end (methacryloyloxy in KH-570, amino in KH-550) react with the carboxyl groups on the sodium polyacrylate molecular chain or form hydrogen bonds, thereby establishing chemical bonds between the carbon coating and the active layer. By introducing amino functional groups onto the current collector surface through the silane coupling agent, they can form amide bonds and other chemical bonds with the carboxyl groups in the binder, thus building chemical bonding forces between the current collector and the active layer.

[0093] Typical adhesive combinations include: A. PVDF (such as HSV900) and CMC-Na (degree of substitution DS = 0.7~0.9) are mixed at a mass ratio of 8:2. The advantages of this combination are: CMC-Na can provide abundant carboxyl groups (-COOH), which ionize at pH = 8~9, enhancing hydrogen bonding and electrostatic interactions with the undercoating; CMC-Na has better chemical stability than polyvinylidene fluoride (PVDF), avoiding electrochemical defluorination reactions. The degree of substitution of CMC-Na is selected to be 0.7~0.9, which provides enough carboxyl functional groups to form a dense chemical bond and hydrogen bond network with the undercoating (improving peel strength), while ensuring processability in the NMP system (no gelation, no delamination), and avoiding the hygroscopicity and side reaction risks caused by excessively high degree of substitution, thus fully supporting the technical effects of "high peel strength, no powdering, and long cycle life" in this application.

[0094] The synergistic mechanism lies in: Taking KH550-modified sodium polyacrylate in the primer as an example, the amino group (-NH2) of KH-550 forms an amide bond (-CO-NH-) with the carboxyl group of CMC-Na; the carboxyl group of the primer PAA-Na forms extensive hydrogen bonds with the hydroxyl group of CMC-Na; the PAA-Na chain interweaves with the PVDF and CMC-Na chains to form a physical interlock.

[0095] B. Mixing ratio: PVDF and PAA-Na (weight average molecular weight 100,000 to 500,000) are mixed at a mass ratio of 7:3. The advantages of this combination are: PAA-Na has a strong interaction with the positive electrode material, which buffers the volume expansion; PAA-Na and the bottom coating are homologous, forming a "homogeneous and mutually soluble" interface transition layer.

[0096] The synergistic mechanism is as follows: both the base layer and the active layer contain PAA-Na, forming a continuous molecular-level transition at the interface and eliminating weak areas; the -NH2 of silane in the base layer condenses with the -COOH of PAA-Na in the active layer to form amide bonds; stress buffering: PVDF provides flexibility, and PAA-Na provides rigid anchoring, synergistically inhibiting cracking.

[0097] III. Battery Assembly: In this application, the embodiments and comparative examples use 3Ah~5Ah sodium-containing positive electrode / hard carbon stacked soft-pack batteries as a unified verification platform. The battery assembly adopts a single-layer stacked structure, in which the positive electrode, separator, and negative electrode are stacked in sequence, and after stacking, they are put into an aluminum-plastic composite film shell. After vacuum sealing, they are dried in an 80°C vacuum drying oven for 24 hours (dew point not higher than -40°C) to ensure that the internal moisture content of the battery is less than 50ppm.

[0098] The electrolyte injection is carried out in a dry room with a dew point not higher than -40°C. The amount of electrolyte injected is determined based on the electrode area and the amount of electrolyte absorbed by the diaphragm. After the electrolyte injection, the plate is left to stand for 24 hours to allow the electrolyte to fully wet the electrode and the interface layer.

[0099] IV. The formation process employs a stepped charging strategy: (1) Formation environment: The formation is carried out in a constant temperature formation cabinet at (45℃±2)℃, and the clamp pressure is 0.3MPa~0.5MPa (to ensure that the electrode and the diaphragm are in close contact and to inhibit sodium precipitation). The formation process is carried out in an argon atmosphere, and the system records voltage, current and time data throughout the process. (2) Formation process: Step 1 (Small Current Activation): Charge to 3.2V with a constant current of 0.05C and let stand for 1 hour (this stage is used for the initial formation of the SEI / CEI film; a small current is beneficial for forming a uniform and dense interface film). Step 2 (Main Formation): Charge at a constant current of 0.1C to 3.65V, then switch to constant voltage charging, with a cutoff current of 0.02C (this stage is for gas removal and interface film improvement). Step 3 (First Cycle Discharge): Discharge at a constant current of 0.2C to 2.5V to complete the first formation cycle; Step 4 (Activation Cycle): Then repeat the charge and discharge cycle twice at 0.2C (i.e., the 2nd and 3rd cycles) to complete battery activation; (3) Post-formation treatment: After the formation is completed, the battery is vacuumed and sealed under vacuum conditions of ≤-0.09MPa to remove the gases generated during the formation process (mainly CO, CO2 and a small amount of hydrocarbon gases). (4) Screening criteria: After formation, all batteries are tested for capacity and internal resistance. Batteries with capacity deviation within ±1% and DC internal resistance deviation within ±5% are retained for subsequent testing. Three parallel samples are set for each experimental condition. The average value of the three samples is used as the final report data, and the standard deviation is recorded at the same time.

[0100] Example 1 This embodiment provides a method for preparing a single battery cell, including: An electrode assembly is obtained, the electrode assembly comprising a negative electrode, a separator, and a positive electrode stacked together; Obtain the housing, and place the electrode assembly inside the housing; Obtain the electrolyte and inject the electrolyte into the casing; A formation process is performed to obtain battery cells; The methods for preparing the positive electrode include: γ-(methacryloyloxy)propyltrimethoxysilane (KH570) was hydrolyzed in an aqueous ethanol solution with a volume fraction of 90% and a pH of 4-5 to obtain a silane hydrolysate. The silane hydrolysate and a sodium polyacrylate aqueous solution with a mass fraction of 0.5%~1% were mixed and reacted at 80°C to obtain silane coupling agent modified sodium polyacrylate. Sodium polyacrylate modified with silane coupling agent was coated onto the surface of carbon-coated aluminum foil and dried to form a base coating with a thickness of 1.0 μm. Sodium vanadium phosphate, conductive carbon black, carbon nanotubes, and a composite binder (polyvinylidene fluoride and sodium carboxymethyl cellulose at a mass ratio of 8:2, with a degree of substitution of sodium carboxymethyl cellulose of 0.7~0.9) were mixed in NMP at mass percentages of 96.2%, 0.8%, 0.5%, and 2.5%, respectively. The mixture was then subjected to high-speed shearing (1500rpm~3000rpm, 30min) and ultrasonic dispersion (40kHz, 10min~15min) to obtain a positive electrode active material slurry with a solid content of 50% and a pH value of 8.5. The positive electrode active material slurry is coated onto the surface of the base coating, dried at 120℃, and then rolled until the compaction density is 2.8 g / cm³. 3 This yields the positive electrode sheet.

[0101] The negative electrode, separator, and electrolyte are all made of conventional materials, which will not be described in detail here.

[0102] In this application, the embodiments and comparative examples use 3Ah~5Ah lithium iron phosphate / graphite stacked soft-pack batteries as a unified verification platform. The battery assembly adopts a single-layer stacked structure, in which the positive electrode, separator, and negative electrode are stacked in sequence. After stacking, the battery is placed into an aluminum-plastic composite film shell, vacuum sealed, and dried in an 80°C vacuum drying oven for 24 hours (dew point not higher than -40°C) to ensure that the internal moisture content of the battery is less than 50ppm.

[0103] The electrolyte injection is carried out in a dry room with a dew point not higher than -40°C. The amount of electrolyte injected is determined based on the electrode area and the amount of electrolyte absorbed by the diaphragm. After the electrolyte injection, the plate is left to stand for 24 hours to allow the electrolyte to fully wet the electrode and the interface layer.

[0104] The formation adopts a tiered charging strategy: (1) Formation environment: The formation is carried out in a constant temperature formation cabinet at (45℃±2)℃, and the clamp pressure is 0.3MPa~0.5MPa (to ensure that the electrode and the diaphragm are in close contact and to inhibit sodium precipitation). The formation process is carried out in an argon atmosphere, and the system records voltage, current and time data throughout the process. (2) Formation process: Step 1 (Small Current Activation): Charge to 3.2V with a constant current of 0.05C and let stand for 1 hour (this stage is used for the initial formation of the SEI / CEI film; a small current is beneficial for forming a uniform and dense interface film). Step 2 (Main Formation): Charge at a constant current of 0.1C to 3.65V, then switch to constant voltage charging, with a cutoff current of 0.02C (this stage is for gas removal and interface film improvement). Step 3 (First Cycle Discharge): Discharge at a constant current of 0.2C to 2.5V to complete the first formation cycle; Step 4 (Activation Cycle): Then repeat the charge and discharge cycle twice at 0.2C (i.e., the 2nd and 3rd cycles) to complete battery activation; (3) Post-formation treatment: After the formation is completed, the battery is vacuumed and sealed under vacuum conditions of ≤-0.09MPa to remove the gases generated during the formation process (mainly CO, CO2 and a small amount of hydrocarbon gases). (4) Screening criteria: After formation, all batteries are tested for capacity and internal resistance. Batteries with capacity deviation within ±1% and DC internal resistance deviation within ±5% are retained for subsequent testing. Three parallel samples are set for each experimental condition. The average value of the three samples is used as the final report data, and the standard deviation is recorded at the same time.

[0105] In this embodiment, the amino group (-NH2) of KH-570 in the base coating forms an amide bond (-CO-NH-) with the carboxyl group of sodium carboxymethyl cellulose, and the carboxyl group of sodium polyacrylate in the base coating forms extensive hydrogen bonds with the hydroxyl / carboxyl groups of CMC-Na. The sodium polyacrylate chain interweaves with the PVDF and CMC-Na chains to form a physical interlock.

[0106] Example 2 The difference between this embodiment and Embodiment 1 is that the method for preparing the positive electrode sheet includes: γ-aminopropyltriethoxysilane was hydrolyzed in an aqueous ethanol solution with a volume fraction of 90% and a pH of 4-5 to obtain a silane hydrolysate. The silane hydrolysate and a sodium polyacrylate aqueous solution with a mass fraction of 0.5%~1% were mixed and reacted at 80°C to obtain silane coupling agent modified sodium polyacrylate. Sodium polyacrylate modified with silane coupling agent was coated onto the surface of carbon-coated aluminum foil and dried to form a base coating with a thickness of 1.5 μm. Sodium vanadium phosphate, conductive carbon black, and composite binder (polyvinylidene fluoride and sodium polyacrylate in a mass ratio of 7:3) were mixed in NMP at a mass ratio of 96.0%, 1.2%, and 2.8%, respectively. After high-speed shearing and ultrasonic dispersion, a positive electrode active material slurry with a solid content of 52% and a pH value of 8.8 was obtained. The positive electrode active material slurry is coated onto the surface of the base coating, dried at 120℃, and then rolled until the compaction density is 2.8 g / cm³. 3 This yields the positive electrode sheet.

[0107] Sodium polyacrylate has a strong interaction with the cathode material, which buffers volume expansion. At the same time, sodium polyacrylate and the base coating are homologous, forming a "homogeneous and mutually soluble" interface transition layer.

[0108] Both the base coat and the active layer contain sodium polyacrylate, forming a continuous molecular-level transition at the interface, eliminating weak areas. The -NH2 of silane in the base coat condenses with the -COOH of sodium polyacrylate in the active layer to form amide bonds. PVDF provides flexibility, while sodium polyacrylate provides rigid anchoring, forming stress buffer and synergistically inhibiting cracking.

[0109] Example 3 The difference between this embodiment and Embodiment 1 is that the method for preparing the positive electrode sheet includes: γ-(methacryloyloxy)propyltrimethoxysilane was hydrolyzed in an aqueous ethanol solution with a volume fraction of 90% and a pH of 4-5 to obtain a silane hydrolysate. The silane hydrolysate and a sodium polyacrylate aqueous solution with a mass fraction of 0.5%~1% were mixed and reacted at 80°C to obtain silane coupling agent modified sodium polyacrylate. Sodium polyacrylate modified with silane coupling agent was coated onto the surface of carbon-coated aluminum foil and dried to form a base coating with a thickness of 0.8 μm. The positive electrode active material (sodium vanadium phosphate and layered oxide in a 1:1 mass ratio), conductive carbon black, carbon nanotubes, and composite binder (polyvinylidene fluoride and sodium carboxymethyl cellulose in an 8:2 mass ratio) were mixed in NMP at a mass ratio of 96.2%, 0.8%, 0.5%, and 2.5%, respectively. After high-speed shearing and ultrasonic dispersion, a positive electrode active material slurry with a solid content of 48% and a pH of 8.2 was obtained. The layered oxide can be selected from P2-type Na... 0.67 Ni 0.33 Mn 0.67 O2; The positive electrode active material slurry is coated onto the surface of the base coating, dried at 120℃, and then rolled until the compaction density is 2.8 g / cm³. 3 This yields the positive electrode sheet.

[0110] Example 4 The difference between this embodiment and Embodiment 1 is that the method for preparing the positive electrode sheet includes: γ-(methacryloyloxy)propyltrimethoxysilane was hydrolyzed in an aqueous ethanol solution with a volume fraction of 90% and a pH of 4-5 to obtain a silane hydrolysate. The silane hydrolysate and a sodium polyacrylate aqueous solution with a mass fraction of 0.5%~1% were mixed and reacted at 80°C to obtain silane coupling agent modified sodium polyacrylate. Sodium polyacrylate modified with silane coupling agent was coated onto the surface of carbon-coated aluminum foil and dried to form a base coating with a thickness of 1.0 μm. Sodium vanadium phosphate, conductive carbon black, carbon nanotubes, and composite binder (polyvinylidene fluoride, sodium carboxymethyl cellulose, and sodium polyacrylate in a mass ratio of 6:2:2) were mixed in NMP at a mass ratio of 96.2%, 0.8%, 0.5%, and 2.5%, respectively. After high-speed shearing and ultrasonic dispersion, a positive electrode active material slurry with a solid content of 50% and a pH value of 8.5 was obtained. The positive electrode active material slurry is coated onto the surface of the base coating, dried at 120℃, and then rolled until the compaction density is 2.8 g / cm³. 3 This yields the positive electrode sheet.

[0111] Comparative Example 1 The difference between this comparative example and Example 1 is that no base coating is applied to the surface of the carbon-coated aluminum foil, and the preparation method of the positive electrode active material slurry includes: Sodium vanadium phosphate, conductive carbon black, carbon nanotubes, and polyvinylidene fluoride were mixed in NMP at mass percentages of 96.2%, 0.8%, 0.5%, and 2.5%, respectively. After stirring, a slurry of positive electrode active material was obtained.

[0112] Comparative Example 2 The difference between this comparative example and Example 1 is that sodium polyacrylate was used directly in the preparation of the primer layer without modification.

[0113] Comparative Example 3 The difference between this comparative example and Example 1 is that only sodium carboxymethyl cellulose was used as a binder in the positive electrode active material slurry.

[0114] Table 1

[0115] The peeling of the positive electrode sheets prepared in the various embodiments and comparative examples of this application, as well as the performance of the battery cells prepared using the corresponding positive electrode sheets, are shown in Table 1.

[0116] The peel strength of Example 1 (6.8 N / cm) was approximately 7.5 times higher than that of Comparative Example 1 (0.8 N / cm), and the peel strength improved from "severe powder shedding" to "no powder shedding," with the 500-cycle retention rate increasing from 78% to 93%. This is because in Comparative Example 1, the active layer was directly coated onto the surface of the carbon-coated aluminum foil, relying solely on physical adsorption for bonding, resulting in extremely low interfacial bonding energy and rapid failure under rolling pressure and cyclic stress. In contrast, Example 1 modified the PAA-Na undercoating with a silane coupling agent, constructing a triple synergistic interfacial bonding mechanism consisting of Si-OC covalent bonds (between the undercoating and carbon coating), amide bonds (between the undercoating and active layer), a three-dimensional hydrogen bond network, and physical entanglement of polymer chains, achieving a fundamental leap from physical adsorption to chemical bonding.

[0117] The peel strength of Comparative Example 2 (2.0 N / cm) was significantly lower than that of Example 1 (6.8 N / cm), and its 500-cycle retention rate (84%) was also significantly lower. The only difference between the two is that the PAA-Na in Comparative Example 2 was not modified with a silane coupling agent and could not form Si-OC covalent bonds with the carbon coating surface. The undercoat was anchored to the carbon coating only by physical adsorption and a small number of hydrogen bonds, and the undercoat / carbon coating interface failed first under stress. This indicates that Si-OC covalent bonds are the core prerequisite for achieving a firm anchorage of the undercoat.

[0118] The peel strength (2.5 N / cm) and 500-cycle retention rate (81%) of Comparative Example 3 were significantly lower than those of Example 1. Comparative Example 3 used only CMC-Na as a binder, lacking the long-chain polymer network provided by PVDF, which prevented sufficient molecular chain interpenetration and physical entanglement with the undercoat. Simultaneously, CMC-Na exhibited poor dispersibility in NMP, resulting in brittle film formation and insufficient cohesion in the active layer. This demonstrates that the physical entanglement structure of polymer chains is indispensable for buffering volumetric stress and maintaining interfacial integrity.

[0119] The peel strength (8.2 N / cm) of Example 2 (KH-550+PVDF / PAA-Na) is slightly higher than that of Example 1 (KH-570+PVDF / CMC-Na, 6.8 N / cm). This is because the reactivity of the amide bond between the amino group of KH-550 and the carboxyl group of PAA-Na is higher, and both the base coating and the active layer contain PAA-Na, forming a continuous molecular-level transition layer of "homogeneous solubility" at the interface, eliminating the weak region at the phase interface. The peel strength (7.5 N / cm) and cycle retention rate (92.5%) of Example 3 (hybrid cathode) are also excellent, indicating that the base coating and binder system of this application has good universality for different cathode materials.

[0120] Comparative Examples 1 to 3 lacked the key interfacial bonding elements of "Si-OC covalent bonds" (Comparative Example 1 had no base coating, and Comparative Example 2 had an unmodified base coating) and "physical entanglement of polymer chains" (Comparative Example 3 had no PVDF), respectively. Therefore, their peel strength and cycle performance were significantly lower than those of the examples. This system verifies that the synergistic effect of chemical bonding, hydrogen bond networks, and physical entanglement is a necessary condition for achieving high peel strength and long cycle life; all three are indispensable.

[0121] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A battery cell, characterized in that, include: An electrode assembly, comprising a negative electrode, a separator, and a positive electrode stacked together; Housing, wherein the electrode assembly is located within the housing; Electrolyte, wherein the electrolyte is located within the housing; The positive electrode includes a current collector, a base coating, and an active layer. The base coating is located between the current collector and the active layer. The interface between the current collector and the base coating has Si-OC covalent bonds, and the interface between the base coating and the active layer has amide bonds and a three-dimensional hydrogen bond network. The interface between the base coating layer and the active layer also has an interlocking structure, which is formed by the interpenetration of polymer molecular chains. The thickness of the base coating is 0.5μm~2μm; The current collector includes carbon-coated aluminum foil; The method for preparing the positive electrode includes: A current collector, a positive electrode active material slurry, and sodium polyacrylate modified with a silane coupling agent are obtained. The positive electrode active material slurry includes a binder, which includes polyvinylidene fluoride and at least one of sodium polyacrylate and sodium carboxymethyl cellulose. After coating the surface of the current collector with the silane coupling agent-modified sodium polyacrylate, and then drying it, a base coating is formed on the surface of the current collector. After coating the surface of the base coating with the positive electrode active material slurry, the material is dried and rolled to obtain the positive electrode sheet. The battery cell is a sodium-ion battery.

2. A method for preparing a single battery cell, characterized in that, include: An electrode assembly is obtained, the electrode assembly comprising a negative electrode, a separator, and a positive electrode stacked together; Obtain the housing, and place the electrode assembly inside the housing; Obtain the electrolyte and inject the electrolyte into the casing; A formation process is performed to obtain battery cells; The positive electrode includes a current collector, a base coating, and an active layer. Si-OC covalent bonds are formed between the current collector and the base coating, and amide bonds and a three-dimensional hydrogen bond network are formed between the base coating and the active layer. The interface between the base coating layer and the active layer also has an interlocking structure, which is formed by the interpenetration of polymer molecular chains. The thickness of the base coating is 0.5μm~2μm; The current collector includes carbon-coated aluminum foil; The method for preparing the positive electrode includes: A current collector, a positive electrode active material slurry, and sodium polyacrylate modified with a silane coupling agent are obtained. The positive electrode active material slurry includes a binder, which includes polyvinylidene fluoride and at least one of sodium polyacrylate and sodium carboxymethyl cellulose. After coating the surface of the current collector with the silane coupling agent-modified sodium polyacrylate, and then drying it, a base coating is formed on the surface of the current collector. After coating the surface of the base coating with the positive electrode active material slurry, the material is dried and rolled to obtain the positive electrode sheet. The battery cell is a sodium-ion battery.

3. The method for preparing a battery cell according to claim 2, characterized in that, The preparation method of the silane coupling agent modified sodium polyacrylate includes: The silane coupling agent is hydrolyzed in an aqueous ethanol solution to obtain a silane hydrolysate; The sodium polyacrylate aqueous solution was mixed with the silane hydrolysate and reacted to obtain the silane coupling agent modified sodium polyacrylate.

4. The method for preparing a single battery cell according to claim 3, characterized in that, The silane coupling agent includes at least one of γ-(methacryloyloxy)propyltrimethoxysilane and γ-aminopropyltriethoxysilane.

5. The method for preparing a single battery cell according to claim 3, characterized in that, The volume fraction of ethanol in the ethanol-water solution is 85% to 95%, and the pH value of the ethanol-water solution is 4 to 5.

6. The method for preparing a battery cell according to claim 3, characterized in that, The sodium polyacrylate aqueous solution has a mass fraction of 0.5% to 1%.

7. The method for preparing a single battery cell according to claim 3, characterized in that, The reaction temperature is 70℃~90℃.

8. The method for preparing a battery cell according to claim 2, characterized in that, The solid content of the positive electrode active material slurry is 45%~55%.

9. A battery device, characterized in that, The battery device includes the battery cell as described in claim 1, or the battery cell obtained by the preparation method as described in any one of claims 2 to 8, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

10. An electrical appliance, characterized in that, The electrical device includes the battery device as described in claim 9, the battery device being used to provide electrical energy.

11. An energy storage device, characterized in that, The energy storage device includes the battery device as described in claim 9, the battery device being used to store electrical energy.

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