Lithium-ion secondary battery and preparation method therefor, and electric device

Abstract

Provided in the present application are a lithium-ion secondary battery and a preparation method therefor, and an electric device. The lithium-ion secondary battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive active material layer, and the positive active material layer comprises a lithium-containing phosphate and an inorganic material modified polyacrylate binder; the inorganic material modified polyacrylate binder comprises a polyacrylate polymer and inorganic particles, and at least part of the polyacrylate polymer is grafted on the surfaces of the inorganic particles; and the polyacrylate polymer comprises structural units derived from an acrylate monomer.

Description

Lithium-ion secondary batteries, their preparation methods, and electrical devices

[0001] Cross-references

[0002] This application claims priority to Chinese Patent Application No. 202411625264.6, filed on November 14, 2024, entitled "Lithium-ion Secondary Battery and Method for Preparation Thereof, and Electrical Device Thereof", which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to the field of secondary battery technology, and in particular to a lithium-ion secondary battery, its preparation method, and an electrical device thereof. Background Technology

[0004] In recent years, as the application scope of secondary batteries has become increasingly wide, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0005] Lithium-ion rechargeable batteries using lithium iron phosphate (LFP) and other lithium-containing phosphates as positive electrode active materials have advantages such as low cost and good safety, making them a popular area of ​​development for lithium-ion rechargeable batteries. PVDF (polyvinylidene fluoride) is commonly used as a binder in positive electrode sheets using lithium-containing phosphates as the positive electrode active material. However, due to concerns about persistent pollution risks and bioaccumulation hazards, the use of fluorinated PVDF binders needs to be limited. Polyacrylate binders, which have stronger adhesion and better stability, can usually be used instead of PVDF.

[0006] However, lithium-ion secondary batteries using lithium phosphate as the positive electrode active material and polyacrylate binder typically have a high internal resistance (DCR), resulting in poor kinetic performance. Therefore, reducing the internal resistance and improving the kinetic performance of these lithium-ion secondary batteries has become a key focus for those skilled in the art. Summary of the Invention

[0007] This application is made in view of the above-mentioned problems, and one of its objectives is to provide a lithium-ion secondary battery with low internal resistance and good kinetic performance, and correspondingly to provide a method for preparing the lithium-ion secondary battery and an electrical device thereon.

[0008] To achieve the above objectives, a first aspect of this application provides a lithium-ion secondary battery, including a positive electrode sheet, the positive electrode sheet including a positive active material layer, the positive active material layer including a polyacrylate binder containing lithium phosphate and inorganic materials.

[0009] The inorganic material modified polyacrylate binder comprises a polyacrylate polymer and inorganic particles, wherein at least a portion of the polyacrylate polymer is grafted onto the surface of the inorganic particles; the polyacrylate polymer comprises structural units derived from acrylate monomers.

[0010] By using the aforementioned inorganic material-modified polyacrylate binder, at least a portion of the polyacrylate polymer is grafted onto the surface of inorganic particles. This prevents the aggregation of inorganic particles, allowing them to be uniformly dispersed in the binder. The inorganic particles effectively inhibit the formation of a film by the polyacrylate binder on the surface of lithium phosphate-containing materials, reducing the density of the film and accelerating lithium-ion transport. This, in turn, reduces the internal resistance of the lithium-ion secondary battery and improves its kinetic performance.

[0011] In any embodiment, the acrylate monomer includes one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate.

[0012] In any embodiment, the structural units derived from acrylate monomers account for 60% to 80% by mass of the polyacrylate polymer.

[0013] In any embodiment, the polyacrylate polymer further includes structural units derived from a first monomer, which includes one or more of styrene or acrylonitrile. This is beneficial for improving the cohesiveness of the positive electrode.

[0014] In any embodiment, the structural units derived from nonpolar monomers account for 20% to 40% by mass of the polyacrylate polymer.

[0015] In any embodiment, the inorganic particles include one or more of titanium dioxide (TiO2), silicon dioxide (SiO2), calcium stearate, or aluminum oxide (Al2O3). This effectively inhibits the formation of polyacrylate binders on the surface of lithium phosphate materials, reduces film density, accelerates lithium-ion transport, and thus reduces battery internal resistance and improves battery kinetic performance. Furthermore, the aforementioned inorganic particles possess good inertness and will not negatively impact the positive electrode active material.

[0016] In any embodiment, the weight-average molecular weight of the polyacrylate polymer is between 150,000 and 400,000 Daltons. This is beneficial for improving the mechanical properties of the positive electrode sheet, such as adhesion and cohesion, and also improves the processability of the positive electrode slurry.

[0017] In any embodiment, the inorganic particles in the inorganic material modified polyacrylate binder have a mass fraction of 5% to 20%. This is beneficial for reducing the internal resistance of the battery, improving the battery's dynamic performance, while also taking into account the mechanical properties of the positive electrode.

[0018] In any embodiment, the inorganic particles in the inorganic material-modified polyacrylate binder have a mass fraction of 10% to 15%. This is beneficial for better balancing the battery's kinetic performance and the mechanical properties of the positive electrode. This allows the battery to have low internal resistance and good kinetic performance, while the positive electrode exhibits good mechanical properties.

[0019] In any embodiment, with the total mass of the positive electrode active material layer being 100%, the mass fraction of the inorganic material-modified polyacrylate binder is 1% to 2%. This is beneficial for the positive electrode slurry to have better dispersibility, improve the mechanical properties of the positive electrode sheet, and have a smaller adverse impact on the battery energy density.

[0020] In any embodiment, the positive electrode active material layer further includes a dispersant, which includes one or more of phosphate ester dispersants or styrene-ethylene / butene-styrene block copolymer (SEBS) dispersants. This is beneficial for improving the dispersibility of the positive electrode slurry and the flexibility of the positive electrode sheet.

[0021] In any embodiment, the mass fraction of the dispersant is 0.1% to 0.5%, based on the total mass of the positive electrode active material layer being 100%. This is beneficial for effectively improving the dispersibility of the positive electrode slurry.

[0022] In any embodiment, the mass fraction of the dispersant is 0.3% to 0.5%, based on the total mass of the positive electrode active material layer being 100%. This is beneficial for further improving the dispersibility of the positive electrode slurry.

[0023] In any embodiment, with the total mass of the positive electrode active material layer being 100%, the mass fraction of the lithium phosphate is 95% to 99%.

[0024] In any embodiment, the lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, or lithium manganese iron phosphate.

[0025] In any embodiment, the surface density of the coating of the positive electrode active material layer on one side of the positive electrode sheet is 15 mg / cm³. 2 ~30mg / cm 2By using the aforementioned inorganic material-modified polyacrylate binder in the positive electrode active material layer, this binder exhibits high adhesion and cohesive strength for lithium phosphate-containing positive electrode materials. This allows for a larger coating density in the positive electrode active material layer, which is beneficial for improving the energy density of the secondary battery.

[0026] In any embodiment, the compaction density of the positive electrode sheet is 2.4 g / cm³. 3 ~2.7g / cm 3 By using the aforementioned inorganic material-modified polyacrylate binder in the positive electrode active material layer, the positive electrode sheet can maintain good adhesion even under a large compaction density, which is beneficial to improving the energy density of the secondary battery.

[0027] The second aspect of this application provides a method for preparing a lithium-ion secondary battery, comprising the following steps:

[0028] A positive electrode slurry is obtained by mixing lithium phosphate, an inorganic material-modified polyacrylate binder, and a solvent; the inorganic material-modified polyacrylate binder comprises a polyacrylate polymer and inorganic particles, at least a portion of the polyacrylate polymer is grafted onto the surface of the inorganic particles; the polyacrylate polymer comprises structural units derived from acrylate monomers.

[0029] The positive electrode slurry is placed on the positive electrode current collector and dried to obtain the positive electrode sheet; and

[0030] The positive electrode, separator, and negative electrode are stacked together, with the separator disposed between the positive and negative electrode to obtain an electrode assembly, which is then used to manufacture a secondary battery.

[0031] By grafting polyacrylate polymers onto the surface of inorganic particles, the aggregation of inorganic particles can be avoided, allowing them to be uniformly dispersed in the binder. This enables the inorganic particles to effectively inhibit the film formation of polyacrylate binders on the surface of lithium phosphate-containing materials, reducing the density of the film formed by polyacrylate binders on the surface of lithium phosphate-containing materials, accelerating lithium-ion transport, thereby reducing the internal resistance of lithium-ion secondary batteries and improving the battery's dynamic performance.

[0032] In any embodiment, the preparation method of the inorganic material modified polyacrylate adhesive includes the following steps:

[0033] Inorganic particles were surface modified using silane coupling agents.

[0034] The surface-modified inorganic particles are mixed with acrylate monomers and initiators, and the inorganic material modified polyacrylate adhesive is obtained after reaction.

[0035] In this way, inorganic particles can be linked to polyacrylate polymer materials through chemical bonds, improving the compatibility between inorganic particles and polyacrylate polymer materials, enhancing the bonding force between inorganic particles and polyacrylate polymer materials, preventing the agglomeration of inorganic particles, allowing inorganic particles to be uniformly dispersed in the binder, and enabling inorganic particles to effectively inhibit the film formation of polyacrylate binders on the surface of lithium phosphate materials.

[0036] In any embodiment, the silane coupling agent comprises one or more of hexamethyldisilazane, γ-aminopropyltriethoxysilane, or γ-glycidoxypropyltrimethoxysilane.

[0037] In any embodiment, the initiator is a free radical polymerization initiator, which includes one or more of potassium persulfate, azobisisobutyronitrile, or benzoyl peroxide.

[0038] In any embodiment, the acrylate monomer includes one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate.

[0039] In any embodiment, the inorganic particles include one or more of titanium dioxide, silicon dioxide, calcium stearate, or aluminum oxide.

[0040] In any embodiment, the Dv50 particle size of the inorganic particles is 1 μm to 5 μm. This facilitates the thorough dispersion of the inorganic particles in the emulsion during the preparation of inorganic material-modified polyacrylate binders.

[0041] The third aspect of this application provides an electrical device, including one or more of the lithium-ion secondary batteries prepared by the preparation method of the lithium-ion secondary batteries of the first aspect of this application or the lithium-ion secondary batteries of the second aspect of this application.

[0042] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0043] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0044] Figure 1 is a schematic diagram of a battery cell according to an embodiment of this application;

[0045] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1;

[0046] Figure 3 is a schematic diagram of an electrical device using a lithium-ion secondary battery as a power source according to an embodiment of this application.

[0047] Explanation of reference numerals in the attached drawings: 5. Battery cell; 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0048] The following describes in detail, with appropriate reference to the accompanying drawings, embodiments of the lithium-ion secondary battery and its preparation method, as well as embodiments of the power-using 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 for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0049] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be included or excluded independently, and they can be combined arbitrarily; 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 also 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 "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0050] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] 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 or implementation 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. The term "implementation" as used herein has a similar understanding.

[0053] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] In this application, open-ended technical features or solutions described using terms such as "containing," "comprising," or "including" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3" and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0055] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0056] Currently, PVDF is commonly used as a binder in the positive electrode of batteries using lithium phosphate as the positive electrode active material. However, due to concerns about persistent pollution risks and bioaccumulation hazards, the use of fluorinated PVDF binders needs to be limited. Polyacrylate binders, which have stronger adhesion and better stability, can usually be used instead of PVDF. However, lithium-ion secondary batteries using lithium phosphate as the positive electrode active material and polyacrylate binders typically have relatively high internal resistance and poor kinetic performance.

[0057] Based on this, one embodiment of this application provides a lithium-ion secondary battery, which includes a positive electrode sheet, the positive electrode sheet including a positive active material layer, the positive active material layer including a lithium phosphate and an inorganic material modified polyacrylate binder; the inorganic material modified polyacrylate binder includes a polyacrylate polymer and inorganic particles, at least a portion of the polyacrylate polymer is grafted onto the surface of the inorganic particles; the polyacrylate polymer includes structural units derived from acrylate monomers.

[0058] Traditional positive electrode sheets using lithium phosphate as the positive electrode active material typically employ PVDF as a binder. However, in some batteries using PFAS (per- and polyfluoroalkyl substances), the use of PVDF needs to be limited due to concerns about persistent pollution risks and bioaccumulation hazards. For example, polyacrylate binders, which have stronger adhesion and better stability, can be used instead of PVDF. However, lithium-ion secondary batteries using polyacrylate binders exhibit higher internal resistance (DCR) and poorer kinetic performance. The main reason is that the polar groups in polyacrylate binders interact with polar sites (such as phosphate groups) on the surface of lithium phosphate, forming hydrogen bonds and other interactions. This results in a relatively dense binder film on the lithium phosphate surface. Furthermore, polyacrylate binders themselves have poor ion conductivity. This dense binder film encapsulating the surface of the lithium phosphate material leads to higher internal resistance and poorer kinetic performance in lithium-ion secondary batteries.

[0059] The aforementioned lithium-ion secondary battery incorporates an inorganic-modified polyacrylate binder in the positive electrode active material layer of the positive electrode sheet. By grafting at least a portion of the polyacrylate polymer onto the surface of the inorganic particles, agglomeration of the inorganic particles is avoided, resulting in better compatibility between the inorganic particles and the polyacrylate binder, and uniform dispersion within the binder. This allows the inorganic particles to effectively inhibit the formation of a polyacrylate binder film on the surface of the lithium phosphate-containing material, reducing the density of the film and accelerating lithium-ion transport. Consequently, this reduces the internal resistance of the lithium-ion secondary battery and improves its kinetic performance. The polyacrylate polymer is grafted onto the surface of the inorganic particles, for example, through chemical bonding.

[0060] It should be noted that inorganic material-modified polyacrylate polymers refer to polymers that link inorganic particles to polyacrylate polymers through physical or chemical methods, including but not limited to those methods. From a chemical perspective, this involves utilizing the active functional groups (such as carboxyl groups and hydroxyl groups) on the polyacrylate polymer molecular chain to react with the active sites on the surface of inorganic particles (such as hydroxyl groups on the surface of metal oxide particles), thereby firmly "grafting" the polymer chain onto the inorganic particles. From a physical perspective, in some cases, polymers and inorganic particles can also be tightly bound together through electrostatic interactions, adsorption, etc., allowing the polymer to adhere to the inorganic particles, achieving a similar grafting effect. Whether grafting has occurred between inorganic particles and polyacrylate binders in inorganic material-modified polyacrylate binders can be determined using Fourier transform infrared spectroscopy (FT-IR). Specifically, if a grafting reaction occurs between inorganic particles and polyacrylate binders, new chemical bonds will form, resulting in corresponding characteristic absorption peaks in the infrared spectrum, or changes in the position, intensity, or shape of some existing absorption peaks. For example, inorganic particles usually have hydroxyl groups on their surface. After grafting with polyacrylate, the absorption peak of the hydroxyl groups may shift or broaden. By comparing the infrared spectrum with that of polyacrylate adhesives that have not been grafted with inorganic particles, it can be determined whether the inorganic particles have undergone a grafting reaction with the polyacrylate adhesives.

[0061] Alternatively, it can be determined using scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS). Specifically, SEM allows observation of the sample's surface morphology. If inorganic particles are grafted onto a polyacrylate binder, the inorganic particles will be relatively uniformly dispersed within the binder and will have a good interface with it. Then, EDS can be used for qualitative and quantitative analysis of the elements on the sample surface. By detecting the distribution of inorganic elements, it can be determined whether inorganic particles have been grafted onto the polymer. If the inorganic elements are found to be uniformly distributed in the binder and there is no obvious separation at the interface, then grafting has occurred.

[0062] In some embodiments, inorganic particles are grafted onto polyacrylate polymers via silane coupling agents. This allows the polyacrylate polymers to be grafted onto the inorganic particles via silane coupling agents, enabling a chemical bond (such as a covalent bond) between the polymers and the particles. Specifically, the silane coupling agent and inorganic particles are first mixed in a solvent, and the reaction is stirred to graft the silane coupling agent onto the surface of the inorganic particles. Then, the surface-modified inorganic particles are added to acrylate monomers, and an initiator is added to initiate a copolymerization reaction. During the reaction, the silane coupling agent on the surface of the inorganic particles reacts with the polyacrylate polymer, thereby grafting the polyacrylate polymer onto the surface of the inorganic particles. In some embodiments, the acrylate monomers include one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate. Using the structural units of the aforementioned acrylate monomers in the binder provides good adhesion properties, which is beneficial for improving the mechanical properties of the electrode.

[0063] In some embodiments, the structural units derived from acrylate monomers constitute 60% to 80% of the mass of the polyacrylate polymer. It is understood that the mass percentage of the structural units derived from acrylate monomers in the polyacrylate polymer can be 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, or any value within the range formed by any two of the above values.

[0064] In some embodiments, the polyacrylate polymer further includes structural units derived from a first monomer, which includes one or more of styrene or acrylonitrile. Thus, by employing the aforementioned structural units derived from the first monomer in the polyacrylate polymer, where styrene contains a benzene ring structure and acrylonitrile contains a polar nitrile group, polymerization with acrylate monomers can increase the intermolecular interaction sites, thereby enhancing intermolecular attraction and making the polymer molecules more tightly bound, thus improving cohesive strength.

[0065] In some embodiments, the structural units derived from the first monomer constitute 20% to 40% of the mass of the polyacrylate polymer. It is understood that the mass percentage of the structural units derived from the first monomer in the polyacrylate polymer can be 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or any value within the range formed by any two of the above values.

[0066] In some embodiments, the inorganic particles include one or more of titanium dioxide, silicon dioxide, calcium stearate, or aluminum oxide. By modifying polyacrylate binders with the aforementioned inorganic particles, the film formation of polyacrylate binders on the surface of lithium phosphate materials can be effectively inhibited, lithium-ion transport can be accelerated, thereby reducing battery internal resistance and improving battery kinetic performance. Furthermore, the aforementioned inorganic particles exhibit good inertness in the positive electrode slurry, will not react with the positive electrode active material, and will not negatively affect the performance of the positive electrode active material.

[0067] In some embodiments, the weight-average molecular weight of the polyacrylate polymer is between 150,000 Daltons and 400,000 Daltons. Controlling the weight-average molecular weight of the polyacrylate polymer within this range is beneficial for improving the mechanical properties of the positive electrode sheet, and also provides better processability and reduces the likelihood of gelation.

[0068] It is understandable that the weight-average molecular weight of polyacrylate polymers can be 150,000 Daltons, 160,000 Daltons, 170,000 Daltons, 180,000 Daltons, 190,000 Daltons, 200,000 Daltons, 210,000 Daltons, 220,000 Daltons, 230,000 Daltons, 240,000 Daltons, 250,000 Daltons, 260,000 Daltons, 270,000 Daltons, 280,000 Daltons, 290,000 Daltons, 300,000 Daltons, 310,000 Daltons, 320,000 Daltons, 330,000 Daltons, 340,000 Daltons, 350,000 Daltons, 360,000 Daltons, 370,000 Daltons, 380,000 Daltons, 390,000 Daltons, 400,000 Daltons, or any value within any two of the above ranges. It is understood that 10,000 Daltons equals 10 kDa.

[0069] In some embodiments, the inorganic particle mass fraction in the inorganic material modified polyacrylate binder is 5% to 20%. Controlling the inorganic particle mass fraction in the inorganic material modified polyacrylate binder within the above range is beneficial for reducing the battery internal resistance, improving the battery dynamic performance, and also taking into account the mechanical properties of the positive electrode.

[0070] It is understood that the mass fraction of inorganic particles in inorganic material modified polyacrylate adhesives can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value within the range formed by any two of the above values.

[0071] In some embodiments, the inorganic particle mass fraction in the inorganic material modified polyacrylate binder is 10% to 15%. Controlling the inorganic particle mass fraction in the inorganic material modified polyacrylate binder within this range helps to better balance the battery's kinetic performance and the mechanical properties of the positive electrode. This allows the battery to have low internal resistance and good kinetic performance, while the positive electrode exhibits good mechanical properties.

[0072] In some embodiments, the mass fraction of the inorganic material-modified polyacrylate binder is 1% to 2%, based on the total mass of the positive electrode active material layer being 100%. Controlling the mass fraction of the inorganic material-modified polyacrylate binder in the positive electrode active material layer within the above range is beneficial for the positive electrode slurry to have better dispersibility, improve the mechanical properties of the positive electrode sheet, and will not have a significant impact on the energy density of the battery.

[0073] It is understood that, taking the total mass of the positive electrode active material layer as 100%, the mass fraction of the inorganic material modified polyacrylate binder can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any value within the range formed by any two of the above values.

[0074] In some embodiments, the mass fraction of the inorganic material-modified polyacrylate binder is 1% to 1.8% based on the total mass of the positive electrode active material layer (100%). Further controlling the mass fraction of the inorganic material-modified polyacrylate binder in the positive electrode active material layer within the above range is beneficial for better balancing the dispersibility of the positive electrode slurry, the mechanical properties of the positive electrode sheet, and the energy density of the battery.

[0075] In some embodiments, the positive electrode active material layer further includes a dispersant, including a flexible dispersant. By adding a dispersant to the positive electrode active material layer, the positive electrode slurry using inorganic material-modified polyacrylate binders is less prone to gelation and easier to process; by using a flexible dispersant, the positive electrode sheet using inorganic material-modified polyacrylate binders maintains good flexibility, which is more conducive to making the positive electrode slurry less prone to gelation and easier to process.

[0076] Understandably, flexible dispersants refer to dispersants that can improve the flexibility of the positive electrode sheet and promote the good dispersion of polyacrylate binders in the positive electrode slurry.

[0077] In some embodiments, the dispersant includes one or more of phosphate ester dispersants or styrene-ethylene / butene-styrene block copolymer (SEBS) dispersants. Phosphate ester dispersants and SEBS dispersants have a certain degree of flexibility and can effectively disperse inorganic material-modified polyacrylate binders, which is beneficial for improving the dispersibility of the positive electrode slurry and the flexibility of the positive electrode sheet.

[0078] Phosphate ester dispersants are a class of organic compounds containing phosphate ester functional groups (-OPO(OR)2), where R represents an organic group. SEBS (Styrene Ethylenebutylene Styrene) dispersants are linear triblock copolymers, consisting of polystyrene as the end block and an ethylene-butene copolymer obtained by hydrogenating polybutadiene as the middle elastic block. It is understood that both the aforementioned phosphate ester dispersants and SEBS dispersants can be commercially available products.

[0079] In some embodiments, the mass fraction of the dispersant is 0.1% to 0.5% based on the total mass of the positive electrode active material layer (100%). Controlling the mass fraction of the dispersant in the positive electrode active material layer within this range is beneficial for improving the dispersibility of the positive electrode slurry. It is understood that the mass fraction of the dispersant in the positive electrode active material layer can be 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, or any value within the range formed by any two of the above values.

[0080] In some embodiments, the mass fraction of the dispersant is 0.3% to 0.5% based on the total mass of the positive electrode active material layer (100%). Further controlling the mass fraction of the flexible dispersant in the positive electrode active material layer within the above range is beneficial for further improving the dispersibility of the positive electrode slurry.

[0081] In some embodiments, the mass fraction of lithium phosphate is 95% to 99% based on the total mass of the positive electrode active material layer (100%). The lithium phosphate may include one or more of lithium iron phosphate, lithium manganese phosphate, or lithium manganese iron phosphate.

[0082] In some embodiments, the coating surface density of the positive electrode active material layer on one side of the positive electrode sheet is 15 mg / cm². 2 ~30mg / cm2 The compaction density of the positive electrode sheet is 2.4 g / cm³. 3 ~2.7g / cm 3 A significant problem facing high-energy-density lithium-ion rechargeable batteries containing lithium phosphate is severe self-discharge. The battery capacity gradually decreases during storage, affecting its storage performance. This is primarily because high-energy-density lithium-ion rechargeable batteries typically require a high coating density and compaction density for the positive electrode film. To firmly bond the active materials, conductive agents, and other particles together, higher demands are placed on the adhesive strength and cohesive force of the binder used in the positive electrode film. Conventional binders, under high coating density and high compaction conditions, lack sufficient adhesion and cohesive force between the binder and the lithium phosphate material. This leads to powder shedding from the positive electrode film during die-cutting, winding, and hot pressing, causing self-discharge in the lithium-ion rechargeable battery.

[0083] In this application, a specific inorganic material modified polyacrylate binder is used in the positive electrode active material layer. This binder has high adhesion and cohesive force for lithium phosphate-containing positive electrode materials. When the coating surface density and compaction density of the positive electrode active material layer are large, it can play a good bonding role for the lithium phosphate in the positive electrode active material layer. This can reduce or avoid the problem of positive electrode film powder shedding that is easy to occur during the die-cutting, winding and hot pressing of the positive electrode sheet, thereby reducing battery self-discharge and improving battery storage performance.

[0084] It is understandable that the surface density of the coating of the positive electrode active material layer on one side of the positive electrode sheet can be, but is not limited to, 15 mg / cm³. 2 16mg / cm 2 17mg / cm 2 18mg / cm 2 19mg / cm 2 20mg / cm 2 21mg / cm 2 22mg / cm 2 23mg / cm 2 24mg / cm 2 25mg / cm 2 26mg / cm 2 27mg / cm 2 28mg / cm 2 29mg / cm 2 30mg / cm 2 And any value within the range formed by any two of the above values; the compaction density of the positive electrode sheet can be, but is not limited to, 2.4, 2.41, 2.42, 2.43, 2.44, 2.45 g / cm³.3 2.46 g / cm 3 2.47 g / cm 3 2.48 g / cm 3 2.49 g / cm 3 2.50g / cm 3 2.51g / cm 3 2.52g / cm 3 2.53g / cm 3 2.54 g / cm 3 2.55g / cm 3 2.56 g / cm 3 2.57g / cm 3 2.58g / cm 3 2.59g / cm 3 2.6g / cm 3 2.61 g / cm 3 2.62 g / cm 3 2.63 g / cm 3 2.64 g / cm 3 2.65g / cm 3 2.66 g / cm 3 2.67 g / cm 3 2.68g / cm 3 2.69 g / cm 3 2.7g / cm 3 And any value within the range formed by any two of the above values.

[0085] One embodiment of this application provides a method for preparing the above-mentioned lithium-ion secondary battery. The method includes the following steps: mixing lithium phosphate, an inorganic material-modified polyacrylate binder, and a solvent to obtain a positive electrode slurry; the inorganic material-modified polyacrylate binder includes a polyacrylate polymer and inorganic particles, with at least a portion of the polyacrylate polymer grafted onto the surface of the inorganic particles; the polyacrylate polymer includes structural units derived from acrylate monomers; placing the positive electrode slurry on a positive electrode current collector and drying it to obtain a positive electrode sheet; stacking the positive electrode sheet, a separator, and a negative electrode sheet, with the separator disposed between the positive and negative electrode sheets, to obtain an electrode assembly; and fabricating the electrode assembly into a lithium-ion secondary battery.

[0086] By grafting polyacrylate polymers onto the surface of inorganic particles, the aggregation of inorganic particles can be avoided, allowing them to be uniformly dispersed in the binder. This enables the inorganic particles to effectively inhibit the film formation of polyacrylate binders on the surface of lithium phosphate-containing materials, reducing the density of the film formed by polyacrylate binders on the surface of lithium phosphate-containing materials, accelerating lithium-ion transport, thereby reducing the internal resistance of lithium-ion secondary batteries and improving the battery's dynamic performance.

[0087] In some embodiments, the acrylate monomers include one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate.

[0088] In some embodiments, the preparation method of the above-mentioned inorganic material modified polyacrylate adhesive includes the following steps: first, surface modification treatment of inorganic particles is performed using a silane coupling agent; then, the surface-modified inorganic particles are mixed with acrylate monomers and an initiator, and the inorganic material modified polyacrylate adhesive is obtained after polymerization reaction.

[0089] Surface modification of inorganic particles using silane coupling agents, followed by polymerization to form polyacrylate binders, facilitates chemical bonding between the inorganic particles and polyacrylate polymers. This enhances their compatibility and adhesion, prevents particle agglomeration, and ensures uniform dispersion within the binder. Furthermore, the inorganic particles effectively inhibit film formation on lithium phosphate-containing materials. It is understood that commercially available products can also be used to modify these inorganic materials into polyacrylate binders.

[0090] In some embodiments, the silane coupling agent includes one or more of hexamethyldisilazane, γ-aminopropyltriethoxysilane, or γ-glycidoxypropyltrimethoxysilane. The initiator is a free radical polymerization initiator, including one or more of potassium persulfate, azobisisobutyronitrile, or benzoyl peroxide. The acrylate monomer includes one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate.

[0091] In some embodiments, the surface of nano-SiO2 particles is first modified with hexamethyldisilazane (HMDS), and then mixed with methyl methacrylate (MMA) and butyl acrylate (BA) emulsions to form a Pickering emulsion. The mixture is then reacted with potassium persulfate (KPS) as an initiator to prepare nano-SiO2 modified acrylate binder.

[0092] In some embodiments, the inorganic particles include one or more of titanium dioxide, silicon dioxide, calcium stearate, or aluminum oxide. Modifying polyacrylate binders with these inorganic particles helps to inhibit film formation of the polyacrylate binder on the surface of lithium phosphate-containing materials, accelerates lithium-ion transport, and thus reduces battery internal resistance and improves battery kinetic performance. Furthermore, these inorganic particles exhibit good inertness in the positive electrode slurry, do not react with the positive electrode active material, and do not negatively affect the performance of the positive electrode active material.

[0093] In some embodiments, the Dv50 particle size of the inorganic particles is 1 μm to 5 μm. Controlling the Dv50 particle size of the inorganic particles within this range is beneficial for ensuring that the inorganic particles are sufficiently dispersed in the emulsion during the preparation of inorganic material-modified polyacrylate binders, and prevents the filter element from clogging due to excessively large inorganic particle size. It is understood that the Dv50 particle size of the inorganic particles can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, or any value within the range formed by any two of the above values.

[0094] It should be noted that the Dv50 particle size, also known as the median particle size, refers to the particle size that corresponds to the cumulative particle size distribution percentage reaching 50% in a particle size distribution.

[0095] One embodiment of this application provides a positive electrode sheet, which includes a positive electrode active material layer. The positive electrode active material layer includes a lithium phosphate and an inorganic material modified polyacrylate binder. The inorganic material modified polyacrylate binder includes a polyacrylate polymer and inorganic particles, with at least a portion of the polyacrylate polymer grafted onto the surface of the inorganic particles.

[0096] By adding inorganic modified polyacrylate binders to the positive electrode active material layer of the positive electrode sheet, and by grafting polyacrylate polymers onto the surface of inorganic particles, the inorganic particles can be uniformly dispersed in the binder. This effectively inhibits the formation of polyacrylate binders on the surface of lithium phosphate materials, accelerates lithium-ion transport, thereby reducing the internal resistance of lithium-ion secondary batteries and improving the dynamic performance of the batteries.

[0097] In some embodiments, the positive electrode sheet further includes a positive current collector, and a layer of positive active material is disposed on at least one side surface of the positive current collector.

[0098] One embodiment of this application provides a positive electrode slurry, comprising lithium phosphate, an inorganic material modified polyacrylate binder, and an organic solvent; the inorganic material modified polyacrylate binder comprises a polyacrylate polymer and inorganic particles, wherein at least a portion of the polyacrylate polymer is grafted onto the surface of the inorganic particles.

[0099] In some embodiments, based on the dry weight of the positive electrode slurry (100%), the mass fraction of the inorganic material-modified polyacrylate binder is 0.5% to 2%, and the mass fraction of the dispersant is 0.1% to 0.5%.

[0100] According to one embodiment of this application, an electrical device is provided, which includes one or more of the lithium-ion secondary batteries described above or prepared by the method described above.

[0101] The lithium-ion secondary battery and power supply device of this application will be described below with appropriate reference to the accompanying drawings.

[0102] In one embodiment of this application, a lithium-ion secondary battery is provided.

[0103] Typically, a lithium-ion secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0104] The positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.

[0105] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0106] In some embodiments, the positive electrode 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0107] In some embodiments, the positive electrode active material includes lithium phosphate, and may also include other positive electrode active materials known in the art for use in batteries. Non-limiting examples of lithium phosphate may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites.

[0108] As a non-limiting example, other positive electrode active materials for batteries include lithium transition metal oxides and their modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and their modified compounds. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3 Co 1 / 3 Mn 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 0.1O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.1 Al 0.05 O2.

[0109] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0110] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0111] The weight ratio of the positive electrode active material in the positive electrode active material layer is 80% to 100% by weight, based on the total weight of the positive electrode active material layer.

[0112] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0% to 20% by weight of the positive electrode active material layer, based on the total weight of the positive electrode active material layer.

[0113] 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, wherein the solid content of the positive electrode slurry is 40wt% to 80wt%, the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s, the positive electrode slurry is coated on both sides of the positive current collector, dried and then cold-pressed by a cold rolling mill to form the positive electrode sheet.

[0114] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0115] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0116] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be obtained by forming a metal material on the polymer material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymer material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0117] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries.

[0118] As a non-limiting example, the negative electrode active material of a lithium-ion secondary battery may include one or more 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 include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more 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 batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0119] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may include one or more 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).

[0120] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0121] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0122] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of a negative electrode current collector, and obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s.

[0123] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0124] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0125] In some embodiments, the electrolyte salt of the lithium-ion secondary battery may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0126] In some embodiments, the solvent may include one or more of the following: fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0127] In some embodiments, the electrolyte may optionally include additives. For example, 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.

[0128] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0129] In some embodiments, the lithium-ion secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0130] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may 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 may be the same or different, without particular limitation.

[0131] In some embodiments, the thickness of the separator is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0132] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0133] In some embodiments, the lithium-ion secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0134] In some embodiments, the outer packaging of the lithium-ion secondary battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0135] A lithium-ion secondary battery includes at least one battery cell. A lithium-ion secondary battery may include one or more battery cells.

[0136] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0137] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0138] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a cover plate 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 cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 52 by a winding process or a 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.

[0139] In some embodiments, the battery cells 5 can be assembled into a battery module, and the number of battery cells 5 contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0140] In the battery module, multiple battery cells 5 can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be secured with fasteners.

[0141] Optionally, the battery module may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0142] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0143] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0144] In addition, this application also provides an electrical device, which includes at least one of the lithium-ion secondary battery, battery module, or battery pack provided in this application. The lithium-ion secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0145] As an electrical device, lithium-ion secondary batteries, battery modules, or battery packs can be selected according to their usage requirements.

[0146] Figure 3 shows an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the lithium-ion secondary battery for this electrical device, a battery pack or battery module can be used.

[0147] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0148] The following are some examples.

[0149] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0150] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0151] Example 1:

[0152] (1) Preparation of positive electrode sheet

[0153] (1.1) 0.19 g of hexamethyldisilazane (HMDS) and 0.95 g of SiO2 particles were stirred in anhydrous ethanol at 65 °C for 2.5 h to modify the surface of SiO2 particles. After drying, surface-modified SiO2 was obtained. Then, it was mixed with 9.5 g of styrene (st), 9.5 g of methyl methacrylate (MMA), and 9.5 g of butyl acrylate (BA) emulsion to form a Pickering emulsion. The Pickering emulsion was reacted at 80 °C for 1 h under the action of 0.532 g of potassium persulfate (KPS) initiator to prepare SiO2 modified polyacrylate binder.

[0154] The SiO2 particles have a Dv50 particle size of 1 μm; the SiO2 modified polyacrylate binder has a weight-average molecular weight of 150,000 Daltons and a SiO2 mass fraction of 5%.

[0155] (1.2) The positive electrode active material LiFePO4, conductive agent carbon black (Super P), the SiO2 modified polyacrylate binder and dispersant SEBS prepared above were mixed evenly in an appropriate amount of NMP at a mass ratio of 96.5:1:2:0.5 to obtain a positive electrode slurry. The positive electrode slurry was coated on both sides of the positive electrode current collector aluminum foil, and the positive electrode sheet was obtained through drying, cold pressing, slitting, and cutting. The solid content of the positive electrode slurry was 65%; the single-sided coating surface density of the positive electrode slurry was 25 mg / cm³. 2 The compaction density of the positive electrode sheet is 2.5 g / cm³. 3 .

[0156] (2) Preparation of negative electrode sheet

[0157] Artificial graphite (negative electrode active material), sodium carboxymethyl cellulose (thickener), styrene-butadiene rubber (binder), and carbon black (Super P) (conductive agent) were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto both sides of the copper foil used as the negative electrode current collector. After the copper foil was dried at room temperature, it was transferred to a 120°C oven for 1 hour. Then, it was cold-pressed and slit to obtain the negative electrode sheet. The solid content of the negative electrode slurry was 50%, and the surface density of the single-sided coating was 12 mg / cm³. 2 .

[0158] (3) Separating membrane

[0159] A 12μm thick polypropylene membrane was selected as the separator.

[0160] (4) Electrolyte

[0161] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a mass ratio of 30:70 to obtain an organic solvent. Fully dried LiPF6 was dissolved in the organic solvent to prepare an electrolyte with a LiPF6 concentration of 1 mol / L.

[0162] (5) Battery assembly

[0163] The positive electrode, negative electrode, and separator are made into an electrode assembly through a winding process. The electrode assembly is then placed into the battery packaging, baked at 80°C to remove water, injected with electrolyte, sealed, and subjected to processes such as standing, hot and cold pressing, formation, clamping, and capacity testing to obtain a lithium-ion secondary battery.

[0164] Example 2:

[0165] This embodiment is basically the same as Example 1, except that: in step (1.1), 0.19g of hexamethyldisilazane (HMDS) and 0.95g of TiO2 particles are stirred in anhydrous ethanol at 65°C for 2.5h to modify the surface of TiO2 particles, and then dried; then it is mixed with 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA) and 9.5g of butyl acrylate (BA) emulsion to form Pickering emulsion; the above Pickering emulsion is reacted at 80°C for 1h under the action of 0.532g of potassium persulfate (KPS) initiator to prepare TiO2 modified polyacrylate binder.

[0166] The TiO2 particles have a Dv50 particle size of 1 μm; the weight-average molecular weight of the polyacrylate in the TiO2-modified polyacrylate binder is 150,000 Daltons, and the mass fraction of TiO2 in the binder is 5%.

[0167] Example 3:

[0168] This embodiment is basically the same as Embodiment 1, except that: in step (1.1), the surface-modified SiO2 particles are mixed with 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA), and 9.5g of butyl acrylate (BA) emulsion to form a Pickering emulsion; the Pickering emulsion is reacted at 80°C for 1h under the action of 0.3g of potassium persulfate (KPS) initiator to prepare SiO2 modified polyacrylate binder.

[0169] The weight-average molecular weight of the polyacrylate in the SiO2-modified polyacrylate binder is 300,000 Daltons.

[0170] Example 4:

[0171] This embodiment is basically the same as Embodiment 1, except that: in step (1.1), the surface-modified SiO2 particles are mixed with 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA), and 9.5g of butyl acrylate (BA) emulsion to form a Pickering emulsion; the Pickering emulsion is reacted at 80°C for 1h under the action of 0.18g of potassium persulfate (KPS) initiator to prepare SiO2 modified polyacrylate binder.

[0172] The weight-average molecular weight of the polyacrylate in the SiO2-modified polyacrylate binder is 400,000 Daltons.

[0173] Example 5:

[0174] This embodiment is basically the same as Example 1, except that: in step (1.1), 0.38g of hexamethyldisilazane (HMDS) and 1.9g of SiO2 particles are stirred in anhydrous ethanol at 65°C for 2.5h to modify the surface of the SiO2 particles, and then dried; then it is mixed with 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA) and 9.5g of butyl acrylate (BA) emulsion to form a Pickering emulsion; the above Pickering emulsion is reacted at 80°C for 1h under the action of 0.532g of potassium persulfate (KPS) initiator to prepare SiO2 modified polyacrylate binder.

[0175] The SiO2-modified polyacrylate binder contains 10% SiO2 by mass.

[0176] Example 6:

[0177] This embodiment is basically the same as Example 1, except that: in step (1.1), 0.57g of hexamethyldisilazane (HMDS) and 2.85g of SiO2 particles are stirred in anhydrous ethanol at 65°C for 2.5h to modify the surface of the SiO2 particles, and then dried; then it is mixed with 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA) and 9.5g of butyl acrylate (BA) emulsion to form a Pickering emulsion; the above Pickering emulsion is reacted at 80°C for 1h under the action of 0.532g of potassium persulfate (KPS) initiator to prepare SiO2 modified polyacrylate binder.

[0178] The SiO2-modified polyacrylate binder contains 15% SiO2 by mass.

[0179] Example 7:

[0180] This embodiment is basically the same as Example 1, except that: in step (1.1), 0.76g of hexamethyldisilazane (HMDS) and 3.8g of SiO2 particles are stirred in anhydrous ethanol at 65°C for 2.5h to modify the surface of the SiO2 particles, and then dried; then it is mixed with 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA) and 9.5g of butyl acrylate (BA) emulsion to form a Pickering emulsion; the above Pickering emulsion is reacted at 80°C for 1h under the action of 0.532g of potassium persulfate (KPS) initiator to prepare SiO2 modified polyacrylate binder.

[0181] The SiO2-modified polyacrylate binder contains 20% SiO2 by mass.

[0182] Example 8:

[0183] This embodiment is basically the same as Embodiment 1, except that the Dv50 particle size of the SiO2 particles in step (1.1) is 5 μm.

[0184] Example 9:

[0185] This embodiment is basically the same as Embodiment 1, except that in step (1.2), the mass ratio of positive electrode active material LFP, conductive agent carbon black (Super P), SiO2 modified polyacrylate binder and dispersant SEBS is 96.5:1.2:1.8:0.5.

[0186] Example 10:

[0187] This embodiment is basically the same as Embodiment 1, except that in step (1.2), the mass ratio of positive electrode active material LFP, conductive agent carbon black (Super P), SiO2 modified polyacrylate binder and dispersant SEBS is 96.5:2:1:0.5.

[0188] Example 11:

[0189] This embodiment is basically the same as Embodiment 1, except that in step (1.2), the mass ratio of positive electrode active material LFP, conductive agent carbon black (Super P), SiO2 modified polyacrylate binder and dispersant SEBS is 96.5:1.2:2:0.3.

[0190] Example 12:

[0191] This embodiment is basically the same as Embodiment 1, except that in step (1.2), the mass ratio of the positive electrode active material LFP, the conductive agent carbon black (Super P), the SiO2 modified polyacrylate binder and the dispersant SEBS is 96.5:1.4:2:0.1.

[0192] Example 13:

[0193] This embodiment is basically the same as that of embodiment 1, except that the dispersant used in step (1.2) is BYK-110 phosphate ester dispersant.

[0194] Example 14:

[0195] This embodiment is basically the same as Embodiment 1, except that: in step (1.1), isooctyl acrylate is used instead of butyl acrylate to prepare the SiO2 modified polyacrylate binder; in step (1.2), lithium manganese iron phosphate (LiMn) is used. 0.6 Fe 0.4 PO4 replaces LiFePO4 as the positive electrode active material.

[0196] Comparative Example 1:

[0197] This comparative example is basically the same as Example 1, except that the preparation method of the positive electrode sheet in step (1) is as follows: the positive active material LiFePO4, conductive agent carbon black (Super P), polyacrylate binder and dispersant SEBS are mixed evenly in an appropriate amount of NMP at a mass ratio of 96.5:1:2:0.5 to obtain a positive electrode slurry, wherein the weight average molecular weight of the polyacrylate binder is 150,000; the above positive electrode slurry is coated on both sides of the positive current collector aluminum foil, and the positive electrode sheet is obtained by drying, cold pressing, slitting and cutting. The polyacrylate binder is prepared by mixing 9.5g of styrene (St), 9.5g of methyl methacrylate (MMA) and 9.5g of butyl acrylate (BA) to form an emulsion; the above emulsion is reacted at 80°C for 1h under the action of 0.532g of potassium persulfate (KPS) initiator.

[0198] Comparative Example 2:

[0199] This comparative example is basically the same as Example 1, except that: step (1.1) is not set; SiO2 modified polyacrylate binder is not used in the positive electrode slurry in step (1.2); positive electrode active material LFP, conductive agent carbon black (Super P), SiO2, polyacrylate binder and dispersant SEBS are mixed evenly in an appropriate amount of NMP at a mass ratio of 96.5:1:0.1:1.9:0.5 to obtain positive electrode slurry.

[0200] The polyacrylate adhesive is prepared by the following method: 9.5g of styrene (st), 9.5g of methyl methacrylate (MMA) and 9.5g of butyl acrylate (BA) emulsion are mixed and reacted at 80°C for 1h under the action of 0.532g of potassium persulfate (KPS) initiator to obtain the polyacrylate adhesive.

[0201] Test method:

[0202] (1) Electrode brittleness test

[0203] Take a 20mm × 100mm (longitudinal) sample of the prepared positive electrode sheet and sample it along the rolling direction. Place the pre-folded experimental electrode sheet on the experimental table and roll it with a 2kg cylindrical roller. After each rolling, observe whether the electrode sheet is translucent. Record the corresponding number of rolling cycles when the electrode sheet is translucent. The number of rolling cycles indicates the flexibility of the electrode sheet. The greater the number of rolling cycles, the better the flexibility.

[0204] (2) Electrode mechanical property testing

[0205] (2.1) Adhesion test

[0206] The prepared positive electrode sheet was cut into test specimens with dimensions of 20mm × 100mm and set aside. One side of the double-sided adhesive was pasted onto the surface of the steel plate, and the other side was pasted onto the positive electrode sheet to be tested. The plate was then pressed with a pressure roller to ensure complete adhesion to the electrode sheet. One end of the current collector was bent in the opposite direction at a bending angle of 180°. The test was conducted using a high-speed rail tensile testing machine. One end of the steel plate was fixed to the lower clamp of the tensile testing machine, and the bent end of the current collector was fixed to the upper clamp. The angle of the current collector was adjusted to ensure that the upper and lower ends were in a vertical position. The specimen was stretched at a speed of 50mm / min until the active material layer was completely peeled off from the surface of the current collector. The displacement and force during the process were recorded, and the force at which the forces were balanced was taken as the adhesion force of the electrode sheet.

[0207] (2.2) Cohesion Test

[0208] The prepared positive electrode sheet was cut into test specimens of 20mm×100mm size for later use. One side of the double-sided adhesive was pasted onto the surface of the steel plate, and the other side was pasted onto the positive electrode sheet to be tested. The positive electrode sheet was then pressed with a pressure roller to ensure complete adhesion to the electrode sheet. Cohesion test tape was pasted onto the other side of the electrode sheet and pressed with a pressure roller. One end of the cohesion test tape was bent in the opposite direction at a bending angle of 180°. The test was conducted using a high-speed rail tensile testing machine. One end of the steel plate was fixed to the lower clamp of the tensile testing machine, and the bent end of the current collector was fixed to the upper clamp. The angle of the current collector was adjusted to ensure that the upper and lower ends were in a vertical position. The specimen was then stretched at a speed of 50mm / min until the active material layer was completely peeled off from the surface of the current collector. The displacement and force during the process were recorded, and the force at which the forces were balanced was taken as the cohesion of the electrode sheet.

[0209] (3) Battery DCR test

[0210] The cell was left to stand for 10 minutes, then charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 0.05C and left to stand for 30 minutes; then discharged at 1C to 2.5V to obtain the capacity C1; left to stand for 30 minutes, then discharged at 1 / 3C to 0.5C1, and left to stand for 30 minutes before measuring the cell voltage V0; then discharged at 3C for 30 seconds before measuring the cell voltage V1, and the DCR was calculated as DCR=(V0-V1) / 3C.

[0211] (4) Battery rate performance test

[0212] The battery cell was allowed to rest for 10 minutes, then charged at a constant current of 1 / 3C to 3.65V, followed by a constant voltage of 0.05C, and allowed to rest for 30 minutes. It was then discharged at a 1 / 3C rate to 2.5V, yielding capacity C1. This process was repeated: charging at a constant current of 1 / 3C to 3.65V, then a constant voltage of 0.05C, and allowing to rest for 30 minutes. The cell was then discharged at a 1C rate to 2.5V, yielding capacity C2. Finally, charging at a constant current of 1 / 3C to 3.65V, then a constant voltage of 0.05C, and allowing to rest for 30 minutes. The cell was then discharged at a 2C rate to 2.5V, yielding capacity C3. The 1C capacity retention rate was calculated as C2 / C1 × 100%, and the 2C capacity retention rate was calculated as C3 / C1 × 100%.

[0213] (5) Test of the mass ratio of inorganic materials in inorganic modified polyacrylate adhesives

[0214] X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) were used to detect the characteristic elements of inorganic fillers in the binder and to quantitatively calculate the mass ratio of inorganic materials.

[0215] (6) Weight-average molecular weight test

[0216] The weight-average molecular weight of the polymer was determined using gel permeation chromatography.

[0217] (7) Dv50 particle size testing of inorganic materials

[0218] The Dv50 particle size of inorganic materials was tested using a laser particle size analyzer.

[0219] The battery parameters for each embodiment and comparative example are shown in Table 1, and the performance data are shown in Table 2. In the tables, the binder dosage refers to the mass fraction of the binder in the positive electrode active material layer; the inorganic particle content refers to the mass fraction of inorganic particles in the inorganic material modified polyacrylate binder. The weight-average molecular weight, inorganic particle content, and inorganic particle Dv50 in Table 1 are all rounded values.

[0220] Table 1

[0221] Table 2

[0222] As shown in Tables 1 and 2, the lithium-ion secondary batteries of the various embodiments of this application have low internal resistance and good kinetic performance. The lithium-ion secondary batteries of Comparative Examples 1 and 2 do not use inorganic-modified polyacrylate binders in their positive electrode slurries, resulting in higher internal resistance and poorer kinetic performance.

[0223] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0224] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium-ion secondary battery, comprising a positive electrode sheet, wherein the positive electrode sheet comprises a positive active material layer, and the positive active material layer comprises a polyacrylate binder containing lithium phosphate and inorganic materials; The inorganic material modified polyacrylate binder comprises a polyacrylate polymer and inorganic particles, wherein at least a portion of the polyacrylate polymer is grafted onto the surface of the inorganic particles; the polyacrylate polymer comprises structural units derived from acrylate monomers.

2. The lithium-ion secondary battery according to claim 1, wherein The acrylate monomers include one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate.

3. The lithium-ion secondary battery according to claim 2, wherein The structural units derived from acrylate monomers account for 60% to 80% of the mass of the polyacrylate polymer.

4. The lithium-ion secondary battery according to any one of claims 1 to 3, wherein The polyacrylate polymer further includes structural units derived from a first monomer, which includes one or more of styrene or acrylonitrile.

5. The lithium-ion secondary battery according to claim 4, wherein The structural units derived from the first monomer constitute 20% to 40% of the mass of the polyacrylate polymer.

6. The lithium-ion secondary battery according to any one of claims 1 to 5, wherein The weight-average molecular weight of the polyacrylate polymers is between 150,000 and 400,000 Daltons.

7. The lithium-ion secondary battery according to any one of claims 1 to 6, wherein The inorganic particles include one or more of titanium dioxide, silicon dioxide, calcium stearate, or aluminum oxide.

8. The lithium-ion secondary battery according to any one of claims 1 to 7, wherein The inorganic particles in the inorganic modified polyacrylate binder have a mass fraction of 5% to 20%.

9. The lithium-ion secondary battery according to claim 8, wherein The inorganic particles in the inorganic modified polyacrylate binder have a mass fraction of 10% to 15%.

10. The lithium-ion secondary battery according to any one of claims 1 to 9, wherein Based on the total mass of the positive electrode active material layer being 100%, the mass fraction of the inorganic material modified polyacrylate binder is 1% to 2%.

11. The lithium-ion secondary battery according to any one of claims 1 to 10, wherein The positive electrode active material layer also includes a dispersant, which includes one or more of phosphate ester dispersants or styrene-ethylene / butene-styrene block copolymer dispersants.

12. The lithium-ion secondary battery according to claim 11, wherein Based on the total mass of the positive electrode active material layer being 100%, the mass fraction of the dispersant is 0.1% to 0.5%.

13. The lithium-ion secondary battery according to claim 12, wherein Based on the total mass of the positive electrode active material layer being 100%, the mass fraction of the dispersant is 0.3% to 0.5%.

14. The lithium-ion secondary battery according to any one of claims 1 to 13, wherein Based on the total mass of the positive electrode active material layer as 100%, the mass fraction of the lithium phosphate is 95% to 99%.

15. The lithium-ion secondary battery according to any one of claims 1 to 14, wherein The lithium-containing phosphate includes one or more of lithium iron phosphate, lithium manganese phosphate, or lithium manganese iron phosphate.

16. The lithium-ion secondary battery according to any one of claims 1 to 15, wherein The coating surface density of the positive electrode active material layer on one side of the positive electrode tab is 15 mg / cm 2 ~ 30 mg / cm 2 .

17. The lithium-ion secondary battery according to any one of claims 1 to 16, wherein The compacted density of the positive electrode plate is 2.4 g / cm 3 ~ 2.7 g / cm 3 .

18. A method for preparing a lithium-ion secondary battery, comprising the following steps: A positive electrode slurry is obtained by mixing lithium phosphate, an inorganic material-modified polyacrylate binder, and a solvent; the inorganic material-modified polyacrylate binder comprises a polyacrylate polymer and inorganic particles, at least a portion of the polyacrylate polymer is grafted onto the surface of the inorganic particles; the polyacrylate polymer comprises structural units derived from acrylate monomers. The positive electrode slurry is placed on the positive electrode current collector and dried to obtain the positive electrode sheet; and The positive electrode, separator, and negative electrode are stacked together, with the separator disposed between the positive and negative electrode to obtain an electrode assembly, which is then used to manufacture a secondary battery.

19. The method of producing a lithium-ion secondary battery according to claim 18, wherein The preparation method of the inorganic material modified polyacrylate adhesive includes the following steps: Inorganic particles were surface modified using silane coupling agents. The surface-modified inorganic particles are mixed with acrylate monomers, a first monomer, and an initiator, and the resulting mixture is reacted to obtain the inorganic material-modified polyacrylate adhesive.

20. The method of producing a lithium-ion secondary battery according to claim 19, wherein The silane coupling agent includes one or more of hexamethyldisilazane, γ-aminopropyltriethoxysilane, or γ-glycidoxypropyltrimethoxysilane.

21. The method for producing a lithium-ion secondary battery according to any one of claims 19 to 20, wherein The initiator is a free radical polymerization initiator, which includes one or more of potassium persulfate, azobisisobutyronitrile, or benzoyl peroxide.

22. The method for producing a lithium-ion secondary battery according to any one of claims 19 to 21, wherein The acrylate monomers include one or more of methyl methacrylate, butyl acrylate, or isooctyl acrylate.

23. The method for producing a lithium-ion secondary battery according to any one of claims 19 to 22, wherein The first monomer includes one or more of styrene or acrylonitrile.

24. The method for producing a lithium-ion secondary battery according to any one of claims 18 to 23, wherein The inorganic particles include one or more of titanium dioxide, silicon dioxide, calcium stearate, or aluminum oxide.

25. The method for producing a lithium-ion secondary battery according to any one of claims 18 to 24, wherein The Dv50 particle size of the inorganic particles is 1μm to 5μm.

26. An electrical device comprising one or more of the lithium-ion secondary batteries according to any one of claims 1 to 17 or the lithium-ion secondary batteries prepared by the preparation method of any one of claims 18 to 25.

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