Gel positive electrode sheet and preparation method therefor, secondary battery, and electrical apparatus

Abstract

A gel positive electrode sheet and a preparation method therefor, a secondary battery, and an electrical apparatus. The gel positive electrode sheet comprises a positive electrode current collector and a gel positive electrode active material layer; the gel positive electrode active material layer is arranged on one or more surfaces of the positive electrode current collector; the gel positive electrode active material layer comprises a gel electrolyte; the gel electrolyte comprises a nitrile additive, and the nitrile additive comprises a cyano group. Therefore, the high-temperature storage performance and the cycle performance of a secondary battery comprising the gel positive electrode sheet are effectively improved.

Description

Gel positive electrode sheet and preparation method thereof, secondary battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202410011372.8 filed on January 2, 2024, entitled “Gel positive electrode sheet and preparation method thereof, secondary battery and electrical device”, which is incorporated into this application in its entirety by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and in particular to a gel positive electrode sheet and a preparation method thereof, a secondary battery and an electrical device. Background Art

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] Due to their advantages such as high energy density, high voltage, and low self-discharge, secondary batteries are widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the advancement of technology, the pursuit of high-performance secondary batteries, such as those with high-temperature storage and cycle performance, has become of great practical significance.

[0006] Summary of the Invention

[0007] The present application provides a gel positive electrode plate and a preparation method thereof, a secondary battery and an electrical device, aiming to improve the high-temperature storage performance and cycle performance of the secondary battery containing the gel positive electrode plate.

[0008] In a first aspect of the present application, a gel positive electrode sheet is provided, comprising a positive electrode current collector and a gel positive electrode active material layer, wherein the gel positive electrode active material layer is arranged on one surface or multiple surfaces of the positive electrode current collector, and the gel positive electrode active material layer contains a gel electrolyte, the gel electrolyte contains a nitrile additive, and the nitrile additive contains a cyano group.

[0009] In the above-mentioned gel positive electrode sheet, the gel electrolyte can bind the nitrile additive containing a cyano group to a certain extent in the gel positive electrode active material layer, so that the nitrile additive is gradually released in the gel positive electrode sheet to exert its effect, effectively stabilizing the structure of the gel positive electrode sheet, improving the high-temperature storage performance of the gel positive electrode sheet, and reducing the gas production of the gel positive electrode sheet. In addition, the gel electrolyte can reduce the diffusion of the nitrile additive to the surface of the negative electrode sheet, reducing the damage of the nitrile additive to the negative electrode sheet, thereby improving the high-temperature storage performance and cycle performance of the secondary battery containing the gel positive electrode sheet.

[0010] In some embodiments, the mass proportion of the nitrile additive in the gel positive electrode active material layer is 0.00006%-0.009%, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0011] In some embodiments, the mass percentage of the nitrile additive in the gel positive electrode active material layer is 0.0012%-0.006%, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0012] In some embodiments, the nitrile additive includes one or more of acetonitrile, propionitrile, butyronitrile, pivalonitrile, capronitrile, malononitrile, succinonitrile, glutaronitrile, and adiponitrile. Thus, the high-temperature storage performance and cycle performance of a secondary battery containing the gel positive electrode sheet can be further improved.

[0013] In some embodiments, the gel electrolyte further comprises a polymer, the monomer of which includes one or more of vinylene carbonate, methyl methacrylate, polyethylene glycol diacrylate, styrene, methyl acrylate, ethyl acrylate, acrylic acid, trimethylsilyl methacrylate, acrolein dimethyl acetal, acrolein diethyl acetal, 2-phenoxyethyl acrylate, tridecafluoro-2-hydroxynonyl ester, trifluoroethyl methacrylate, propenyl-1,3-sultone, glycidyl methacrylate, acrylamide, trifluoroethyl acrylate, (acryloxymethyl) dimethylmethoxysilane, cyanoethyl acrylate, hydroxyethyl acrylate, triallyl trimesic acid ester, hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl) 2-hydroxypropyl acrylate, 1-vinyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, and pentafluorophenol acrylate. Thus, the high temperature storage performance and cycle performance of the secondary battery can be further improved.

[0014] In some embodiments, the gelled positive electrode active material layer further comprises a positive electrode active material, comprising one or more of lithium cobalt oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Nitrile additives can be slowly released from the gelled electrolyte onto the surface of these positive electrode active materials, reducing the dissolution and gassing of transition metal ions in the positive electrode active materials, thereby further improving the high-temperature storage performance and cycling performance of the secondary battery.

[0015] A second aspect of the present application provides a method for preparing a gel positive electrode sheet, comprising the following steps:

[0016] forming the gel positive electrode active material layer on one surface or multiple surfaces of the positive electrode current collector;

[0017] The gel positive electrode sheet includes the positive electrode current collector and the gel positive electrode active material layer. The gel positive electrode active material layer contains a gel electrolyte. The gel electrolyte contains a nitrile additive. The nitrile additive contains a cyano group.

[0018] Therefore, the gel positive electrode sheet can be prepared simply, which is conducive to the mass production of the gel positive electrode sheet.

[0019] In some embodiments, the step of forming the gel positive electrode active material layer on one surface or multiple surfaces of the positive electrode current collector includes:

[0020] Disposing a positive electrode slurry containing a positive electrode active material on one surface or multiple surfaces of the positive electrode current collector, and drying the positive electrode slurry to form a gel positive electrode active material layer intermediate;

[0021] The gel cathode active material layer intermediate is infiltrated with a gel precursor solution containing the nitrile additive, and the gel precursor solution is solidified to form the gel cathode active material layer.

[0022] In the gel positive electrode active material layer prepared in the above embodiment, the nitrile additive can act in situ on the surface of the positive electrode active material, which can stabilize the structure of the positive electrode active material, further improve the cycle stability of the secondary battery, and at the same time reduce the overall amount of nitrile additive in the battery, thereby improving the utilization efficiency of the nitrile additive.

[0023] In some embodiments, the mass proportion of the nitrile additive in the gel precursor solution is 0.1%-20%, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0024] In some embodiments, the mass proportion of the nitrile additive in the gel precursor solution is 0.5%-10%, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0025] In some embodiments, the gel precursor solution further comprises polymer monomers, with the polymer monomers accounting for 3% to 10% by weight of the gel precursor solution. This helps enhance the gel electrolyte's ability to bind nitrile additives, thereby further improving the secondary battery's cycling performance and high-temperature storage performance.

[0026] The third aspect of the present application provides a secondary battery comprising at least one of the gel positive electrode sheet described in the first aspect of the present application and the gel positive electrode sheet prepared by the preparation method described in the second aspect of the present application.

[0027] The secondary battery of the present application includes the gel positive electrode sheet provided by the present application, and thus has at least the same advantages as the gel positive electrode sheet.

[0028] The fourth aspect of the present application provides an electrical device comprising at least one of the gel positive electrode sheet described in the first aspect of the present application, the gel positive electrode sheet prepared by the preparation method described in the second aspect of the present application, and the secondary battery described in the third aspect of the present application.

[0029] The electric device of the present application includes at least one of the gel positive electrode sheet provided in the present application and the secondary battery provided in the present application, and thus has at least the same advantages as the gel positive electrode sheet or the secondary battery.

[0030] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0032] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0033] FIG. 2 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG. 1 .

[0034] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0035] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0036] FIG5 is an exploded view of the battery pack shown in FIG4 according to an embodiment of the present application.

[0037] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0038] Description of reference numerals:

[0039] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Battery cell; 5. Casing; 5. Electrode assembly; 5. Cover; 6. Electrical device. DETAILED DESCRIPTION

[0040] Below, some embodiments of the gel positive electrode sheet and its preparation method, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0041] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0042] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0045] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0046] In this application, in the open technical features or technical solutions described with words such as "contain", "include", and "include", unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that also include additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members". In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0047] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0048] With the advancement of technology, electric vehicles, mobile devices such as mobile phones and tablet batteries are in urgent need of high-performance secondary batteries as energy storage devices. Introducing appropriate additives into secondary battery systems is one of the most cost-effective methods to improve secondary battery performance. However, the introduction of additives that benefit the positive electrode may damage the negative electrode. How to make the additives work in the positive electrode while minimizing their impact on the negative electrode is a technical problem that needs to be solved urgently.

[0049] Based on this, the present application provides a gel positive electrode plate, comprising a positive electrode collector and a gel positive electrode active material layer, the gel positive electrode active material layer being arranged on one surface or multiple surfaces of the positive electrode collector, the gel positive electrode active material layer comprising a gel electrolyte, the gel electrolyte comprising a nitrile additive, and the nitrile additive comprising a cyano group; the gel electrolyte can bind the nitrile additive comprising a cyano group to a certain extent in the gel positive electrode active material layer, so that the nitrile additive is gradually released in the gel positive electrode plate to exert its effect, effectively stabilizing the structure of the gel positive electrode plate, improving the high-temperature storage performance of the gel positive electrode plate, reducing the gas production of the gel positive electrode plate, and the gel electrolyte can reduce the diffusion of the nitrile additive to the surface of the negative electrode plate, reducing the damage of the nitrile additive to the negative electrode plate, thereby improving the high-temperature storage performance and cycle performance of the secondary battery comprising the gel positive electrode plate.

[0050] Gel positive electrode

[0051] One embodiment of the present application provides a gel positive electrode sheet, including a positive electrode current collector and a gel positive electrode active material layer, the gel positive electrode active material layer is arranged on one surface or multiple surfaces of the positive electrode current collector, the gel positive electrode active material layer contains a gel electrolyte, the gel electrolyte contains a nitrile additive, and the nitrile additive contains a cyano group.

[0052] In the above-mentioned gel positive electrode sheet, the gel electrolyte can bind the nitrile additive containing a cyano group to a certain extent in the gel positive electrode active material layer, so that the nitrile additive is gradually released in the gel positive electrode sheet to exert its effect, effectively stabilizing the structure of the gel positive electrode sheet, improving the high-temperature storage performance of the gel positive electrode sheet, and reducing the gas production of the gel positive electrode sheet. In addition, the gel electrolyte can reduce the diffusion of the nitrile additive to the surface of the negative electrode sheet, reducing the damage of the nitrile additive to the negative electrode sheet, thereby improving the high-temperature storage performance and cycle performance of the secondary battery containing the gel positive electrode sheet.

[0053] Optionally, a high performance liquid chromatography detection method can be used to detect whether the gel electrolyte contains nitrile additives or the type of nitrile additives. Specifically, the detection can be carried out with reference to the provisions of the relevant detection method in GB / T 26792-2019.

[0054] In some embodiments, the mass proportion of the nitrile additive in the gel positive electrode active material layer is 0.00006%-0.009%. This can further improve the high-temperature storage performance and cycle performance of the secondary battery. It is understood that the mass proportion of the nitrile additive in the gel positive electrode active material layer includes but is not limited to: 0.00006%, 0.00008%, 0.0001%, 0.0003%, 0.0005%, 0.0007%, 0.0009%, 0.001%, 0.002%, 0.004%, 0.006%, and 0.009%. Optionally, the mass proportion of the nitrile additive in the gel positive electrode active material layer is 0.0012%-0.006%.

[0055] Alternatively, nuclear magnetic resonance spectroscopy (NMR) may be used to determine the mass proportion of the nitrile additive in the gel positive electrode active material layer. Specific detection may be performed with reference to the relevant detection method provisions in GB / T 34059-2017.

[0056] In some embodiments, the nitrile additive includes one or more of acetonitrile, propionitrile, butyronitrile, pivalonitrile, capronitrile, malononitrile, succinonitrile, glutaronitrile, and adiponitrile. Selecting the above-mentioned nitrile additives can further improve the high-temperature storage performance and cycle performance of the secondary battery containing the gel positive electrode sheet.

[0057] In some embodiments, the gel electrolyte further comprises a polymer, wherein the monomer of the polymer comprises one or more of vinylene carbonate, methyl methacrylate, polyethylene glycol diacrylate (PEGDA), styrene, methyl acrylate, ethyl acrylate, acrylic acid, trimethylsilyl methacrylate, acrolein dimethyl acetal, acrolein diethyl acetal, 2-phenoxyethyl acrylate, tridecafluoro-2-hydroxynonyl ester, trifluoroethyl methacrylate, allyl-1,3-sultone, glycidyl methacrylate, acrylamide, trifluoroethyl acrylate, (acryloxymethyl)dimethylmethoxysilane, cyanoethyl acrylate, hydroxyethyl acrylate, triallyl trimesic acid ester, hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl) 2-hydroxypropyl acrylate, 1-vinyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt, and pentafluorophenol acrylate.

[0058] In some embodiments, the gel electrolyte further includes an organic solvent and a first electrolyte salt.

[0059] In some embodiments, the organic solvent includes one or more of a carbonate organic solvent, a carboxylate organic solvent, and an ether organic solvent.

[0060] In some embodiments, the carbonate organic solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, and butylene carbonate.

[0061] In some embodiments, the carboxylate organic solvent includes one or more of propyl butyrate, propyl acetate, isopropyl acetate, ethyl propionate, propyl propionate, butyl propionate, isopropyl propionate, and ethyl butyrate.

[0062] In some embodiments, the ether organic solvent includes one or more of methyl ether, propyl ether, butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0063] In some embodiments, the first electrolyte salt includes a lithium salt. Optionally, the lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorooxalatoborate (LiDFOB), lithium perchlorate (LiClO4), and lithium trifluoromethanesulfonyl.

[0064] In some embodiments, the gel positive electrode active material layer further comprises a positive electrode active material, and the positive electrode active material comprises one or more of lithium cobalt oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds. Nitrile additives can be slowly released from the gel electrolyte to the surface of the positive electrode active material, reducing the dissolution and gas production of transition metal ions in the positive electrode active material, thereby further improving the high temperature storage performance and cycle performance of the secondary battery. Non-limiting examples of lithium cobalt oxide can include but are not limited to LiCoO2; non-limiting examples of lithium nickel manganese oxide can include but are not limited to LiNi 0.5 Mn 1.5 O4、LiNi 0.5 Mn 0.5 O2, etc.; non-limiting examples of lithium manganese oxides may include but are not limited to LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include but are not limited to LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc.; Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.8 Co 0.15 Al 0.05 O2.

[0065] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the gel positive electrode sheet is different when the battery is discharged to different states. In the list of positive electrode active materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode active material is applied to the gel positive electrode sheet in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode active material contained in the gel positive electrode sheet will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode active materials, and non-limiting examples include coating modification.

[0066] In the examples of positive electrode active materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0067] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the gel positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0068] 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 base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0069] In some embodiments, the gel cathode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0070] In some embodiments, the gel cathode active material layer may further include a conductive agent. As non-limiting examples, 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.

[0071] Another embodiment of the present application provides a method for preparing the gel positive electrode sheet of the present application, comprising the following steps:

[0072] A gel positive electrode active material layer is formed on one surface or multiple surfaces of the positive electrode current collector.

[0073] Therefore, the gel positive electrode sheet can be prepared simply, which is conducive to the mass production of the gel positive electrode sheet.

[0074] In some embodiments, the step of forming a gel positive electrode active material layer on one or more surfaces of the positive electrode current collector includes:

[0075] Disposing a positive electrode slurry containing a positive electrode active material on one or more surfaces of a positive electrode current collector, and drying the positive electrode slurry to form a gel positive electrode active material layer intermediate;

[0076] The gel positive electrode active material layer intermediate is infiltrated with a gel precursor solution containing a nitrile additive, and the gel precursor solution is solidified to form a gel positive electrode active material layer.

[0077] In the above embodiment, the gel precursor is in liquid form and can penetrate into the internal pores of the gel cathode active material layer intermediate by infiltration. After curing, a gel network can be formed to encapsulate the cathode active material. This gel network assumes the function of conducting active ions. The nitrile additive acts in situ on the surface of the cathode active material, which can stabilize the structure of the cathode active material, further improving the cycle stability of the secondary battery, while reducing the overall amount of nitrile additive in the battery and improving the utilization efficiency of the nitrile additive. It is understood that the active ions may include but are not limited to lithium ions.

[0078] In some embodiments, a gelled positive electrode active material layer intermediate can be prepared by dispersing the components used to prepare the gelled positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry on at least one side of a positive electrode current collector, and subjecting the mixture to drying, cold pressing, and other processes to obtain a gelled positive electrode active material layer intermediate. The type of solvent can be selected from, but not limited to, any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 15 mg / cm 2 -35mg / cm 2 The compacted density of the gel cathode active material layer intermediate can be 3.0 g / cm 3 -3.6g / cm 3 , optional 3.3g / cm 3 -3.5g / cm 3 .

[0079] In this application, the unit "mPa·s" refers to millipascal·second, and the unit "mg / cm 2 " refers to milligrams per square centimeter, the unit is "g / cm 3 ” refers to grams per cubic centimeter.

[0080] In some embodiments, the mass proportion of the nitrile additive in the gel precursor solution is 0.1%-20%. It is understood that the mass proportion of the nitrile additive in the gel precursor solution includes, but is not limited to, 0.1%, 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, and 20%. Alternatively, the mass proportion of the nitrile additive in the gel precursor solution is 0.5%-10%.

[0081] In some embodiments, the gel precursor solution further comprises polymer monomers, and the mass proportion of the polymer monomers in the gel precursor solution is 3%-10%. This is beneficial to improving the binding ability of the gel electrolyte to the nitrile additive, thereby further improving the cycle performance and high-temperature storage performance of the secondary battery. It is understood that the mass proportion of the polymer monomers in the gel precursor solution includes but is not limited to: 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%. Furthermore, the mass proportion of the polymer monomers in the gel precursor solution is 4%-6%.

[0082] In some embodiments, the gel precursor solution further includes an organic solvent, a first electrolyte salt, and an initiator.

[0083] In some embodiments, the mass proportion of the initiator in the gel precursor solution is 0.03%-0.4%. It is understood that the mass proportion of the initiator in the gel precursor solution includes but is not limited to: 0.03%, 0.05%, 0.07%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, and 0.4%.

[0084] In some embodiments, the mass ratio of the initiator to the monomer of the polymer is (0.01-0.04): 1. It is understood that the mass ratio of the initiator to the monomer of the polymer includes but is not limited to: 0.01: 1, 0.015: 1, 0.02: 1, 0.025: 1, 0.03: 1, 0.035: 1, 0.04: 1.

[0085] In some embodiments, the mass ratio of the organic solvent, the first electrolyte salt, the nitrile additive, and the monomer of the polymer is (70-80):(10-20):(0.5-10):(3-10).

[0086] In some embodiments, the initiator comprises an azo initiator. Alternatively, the azo initiator comprises one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, and azobisisoheptylonitrile.

[0087] Yet another embodiment of the present application provides a secondary battery, comprising the gel positive electrode sheet described above.

[0088] Another embodiment of the present application further provides an electrical device, comprising at least one of the gel positive electrode sheet and the secondary battery mentioned above.

[0089] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0090] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0091] Positive electrode

[0092] The gel positive electrode plate mentioned above in this application is used.

[0093] Negative electrode

[0094] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0095] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0096] 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 base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0097] In some embodiments, the negative electrode active material may adopt negative electrode active materials for batteries that are well known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional 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.

[0098] In some embodiments, the negative electrode active material layer may further 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).

[0099] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0101] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. 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 two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%-60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit surface density on a dry weight basis (excluding the solvent) can be 75g / m 2 -220g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 -1.8g / cm 3 .

[0102] In this application, the unit "g / m2 ” refers to grams per square meter.

[0103] electrolytes

[0104] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0105] In some embodiments, the electrolyte comprises an electrolyte solution comprising a second electrolyte salt and a solvent.

[0106] In some embodiments, the second electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0107] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0108] In some embodiments, the electrolyte may optionally include other additives. For example, the other additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0109] In some embodiments, other additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0110] Isolation film

[0111] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0112] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0113] In some embodiments, the isolation film has a thickness of 6 μm-40 μm, and optionally 12 μm-20 μm.

[0114] In this application, the unit "μm" means micrometer.

[0115] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0116] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0117] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0118] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0119] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0120] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 5 with a square structure as an example.

[0121] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0122] The secondary battery may be a battery module 4 or a battery pack 1 .

[0123] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0124] FIG3 shows an example battery module 4. Referring to FIG3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0125] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0126] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0127] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0128] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0129] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0130] Figure 6 shows an example of an electric device 6. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0131] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0132] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0133] In the following examples and comparative examples, PEGDA 300 means that the number of repeating structural units in PEDGA is 300.

[0134] Example 1

[0135] (1) Preparation of positive electrode intermediate

[0136] Lithium cobalt oxide (LiCoO2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone (NMP) solvent system in a weight ratio of 94:3:3, and then coated on both sides of the aluminum foil, dried, and cold pressed to obtain a positive electrode intermediate. The positive electrode intermediate contains a gel positive electrode active material layer intermediate, which is cut into corresponding sizes for use. The coating amount per unit area on both sides is 0.4g / 1540.25mm 2 In this application, the unit "g" refers to grams, and the unit "mm 2 ” refers to square millimeters.

[0137] (2) Preparation of basic electrolyte

[0138] Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were prepared in a mass ratio of 2:3:1 and stirred uniformly to obtain a basic electrolyte.

[0139] (3) Preparation of gel precursor solution

[0140] The succinonitrile additive, the polymer monomer PEGDA300 and the basic electrolyte were evenly mixed in a mass ratio of 5:5:90, and then 2% of the mass of the polymer monomer as the initiator azobisisobutyronitrile (AIBN) was added and stirred to dissolve to obtain a gel precursor solution.

[0141] (4) Preparation of gel positive electrode

[0142] The prepared positive electrode intermediate stack is placed in an aluminum-plastic film, and the gel precursor liquid is injected at an injection ratio of 1.5 grams per ampere hour (g / Ah). The negative pressure is pumped for 5 minutes (min), and then heat-sealed for 6 hours (h). After immersion, it is placed in an oven and heated to 70 degrees Celsius (℃) for 10 hours for curing. The aluminum-plastic film is removed to obtain a gelled gel positive electrode sheet, which includes a gel positive electrode active material layer.

[0143] (5) Preparation of negative electrode sheet

[0144] The negative electrode active material (graphite), conductive agent (acetylene black), and binder (carboxymethyl cellulose) were mixed in a mass ratio of 97wt%:2wt%:1wt%, and deionized water was added and stirred to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of the copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.13g / 1540.25mm 2 .

[0145] (6) Preparation of lithium-ion batteries

[0146] The gel positive electrode sheet, separator, and negative electrode sheet were stacked, with the separator positioned between the two sheets. A base electrolyte was injected at a rate of 1.2 g / Ah, and the electrolyte was allowed to soak for 12 hours to produce a lithium-ion battery. The separator comprised a base film and a first coating layer and a second coating layer located on both surfaces of the base film in the thickness direction. The first coating layer was an alumina ceramic layer, and the second coating layer was a polymer.

[0147] Example 2-15

[0148] The same as Example 1, except that the type of nitrile additive, the mass proportion of the nitrile additive in the gel positive electrode active material layer, the mass proportion of the nitrile additive in the gel precursor solution, the mass proportion of the polymer monomer in the gel precursor solution, and the mass ratio of the nitrile additive, the polymer monomer to the basic electrolyte in the gel precursor solution are changed, as shown in Table 1.

[0149] Comparative Example 1

[0150] (1) Preparation of positive electrode sheet

[0151] Lithium cobalt oxide (LiCoO2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed thoroughly in an N-methylpyrrolidone (NMP) solvent system at a weight ratio of 94:3:3, and then coated on both sides of the aluminum foil. The foil was dried and cold pressed to obtain a positive electrode sheet, which was then cut into corresponding sizes for later use. The coating amount per unit area on both sides was 0.4g / 1540.25mm 2 .

[0152] (2) Preparation of basic electrolyte

[0153] Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were prepared in a mass ratio of 2:3:1 and stirred uniformly to obtain a basic electrolyte.

[0154] (3) Preparation of negative electrode sheet

[0155] The negative electrode active material (graphite), conductive agent (acetylene black), and binder (carboxymethyl cellulose) were mixed in a mass ratio of 97wt%:2wt%:1wt%, and deionized water was added and stirred to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of the copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.13g / 1540.25mm 2 .

[0156] (4) Preparation of lithium-ion batteries

[0157] The positive electrode sheet, the separator and the negative electrode sheet are stacked so that the separator is located between the positive electrode sheet and the negative electrode sheet, and the basic electrolyte is injected at a rate of 1.2 g / Ah. The electrolyte is soaked for 12 hours to obtain a lithium-ion battery.

[0158] Comparative Example 2

[0159] The method is basically the same as Example 1, except that: in step (3), the polymer monomer PEGDA300 and the basic electrolyte are evenly mixed in a mass ratio of 5:95, and then 2% of the mass of the polymer monomer azobisisobutyronitrile (AIBN) is added and stirred to dissolve to obtain a gel precursor solution; that is, when preparing the gel precursor solution in step (3) of Comparative Example 2, no succinonitrile additive is added, and the gel positive electrode active material layer contains a gel electrolyte, but the succinonitrile additive is not present in the gel electrolyte.

[0160] Comparative Example 3

[0161] (1) Preparation of positive electrode sheet

[0162] Lithium cobalt oxide (LiCoO2), conductive agent acetylene black, binder polyvinylidene fluoride (PVDF), and succinonitrile additive are fully stirred and mixed in N-methylpyrrolidone (NMP) solvent system in a weight ratio of 94:3:2.997:0.003, and then coated on both sides of aluminum foil, dried, and cold pressed to obtain positive electrode sheets, which are cut into corresponding sizes for use. The coating amount per unit area on both sides is 0.4g / 1540.25mm 2 .

[0163] (2) Preparation of basic electrolyte

[0164] Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) were prepared in a mass ratio of 2:3:1 and stirred uniformly to obtain a basic electrolyte.

[0165] (3) Preparation of negative electrode sheet

[0166] The negative electrode active material (graphite), conductive agent (acetylene black), and binder (carboxymethyl cellulose) were mixed in a mass ratio of 97wt%:2wt%:1wt%, and deionized water was added and stirred to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of the copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.13g / 1540.25mm 2 .

[0167] (4) Preparation of lithium-ion batteries

[0168] The positive electrode sheet, the separator and the negative electrode sheet are stacked so that the separator is located between the positive electrode sheet and the negative electrode sheet, and the basic electrolyte is injected at a rate of 1.2 g / Ah. The electrolyte is soaked for 12 hours to obtain a lithium-ion battery.

[0169] Performance Testing

[0170] (1) High temperature storage test

[0171] At 60°C, the lithium-ion battery was charged to 4.5 volts (V) at a rate of 0.5C, then charged at a constant voltage until the current dropped below 0.05C. It was then discharged to 2.5V at a rate of 0.5C. The initial discharge capacity was recorded as C1. The lithium-ion battery was adjusted to 100% SOC and stored at 60°C. After 40 days, the charge and discharge cycle was repeated using the same procedure. The discharge capacity was recorded as C2.

[0172] High temperature storage capacity retention rate (%) = C2 / C1×100%.

[0173] (2) Cyclic performance test

[0174] At 25°C, charge the lithium-ion battery to 4.5V at a rate of 0.5C, then charge at a constant voltage until the current is less than 0.05C, and then discharge it to 2.5V at a rate of 1C. Perform a cycle test in this full-charge-discharge form until the discharge capacity of the lithium-ion battery decays to 80% of the initial capacity, and record the number of cycles at this time.

[0175] The product parameters and performance test results of each embodiment and each comparative example are shown in Table 1, wherein “ / ” represents the absence of the substance or parameter.

[0176] Table 1

[0177] As shown in Table 1, the gelled positive electrode active material layers of the gelled positive electrode sheets prepared in Examples 1-15 contain a gelled electrolyte and a nitrile additive. The positive electrode active material layer of the positive electrode sheet prepared in Comparative Example 1 contains neither a gelled electrolyte nor a nitrile additive. The gelled positive electrode active material layer of the gelled positive electrode sheet prepared in Comparative Example 2 contains a gelled electrolyte but no nitrile additive. The positive electrode active material layer of the positive electrode sheet prepared in Comparative Example 3 contains a nitrile additive but no gelled electrolyte. Compared with Comparative Examples 1-3, the batteries of Examples 1-15 exhibit higher high-temperature storage capacity retention rates and the number of cycles at which the discharge capacity at room temperature decays to 80% of the initial capacity. This indicates that the combination of the gelled electrolyte and the nitrile additive in the positive electrode active material layers of Examples 1-15 effectively improves the high-temperature storage and cycling performance of the batteries.

[0178] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0179] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A gel positive electrode sheet, comprising a positive current collector and a gel positive electrode active material layer, wherein the gel positive electrode active material layer is disposed on one surface or multiple surfaces of the positive current collector, the gel positive electrode active material layer contains a gel electrolyte, the gel electrolyte contains a nitrile additive, and the nitrile additive contains a cyano group.

2. The gel positive electrode sheet according to claim 1, wherein, The mass ratio of the nitrile additive in the gel positive electrode active material layer is 0.00006%-0.009%.

3. The gel positive electrode sheet according to claim 1 or 2, wherein, The mass ratio of the nitrile additive in the gel positive electrode active material layer is 0.0012%-0.006%.

4. The gel positive electrode sheet according to any one of claims 1 to 3, wherein, The nitrile additive includes one or more of acetonitrile, propionitrile, butyronitrile, pivalonitrile, hexanenitrile, malononitrile, succinonitrile, glutaronitrile, and adiponitrile.

5. The gel positive electrode sheet according to any one of claims 1 to 4, wherein, The gel electrolyte further contains a polymer, and the monomers of the polymer include one or more of vinylene carbonate, methyl methacrylate, polyethylene glycol diacrylate, styrene, methyl acrylate, ethyl acrylate, acrylic acid, trimethylsilyl methacrylate, acrolein dimethyl acetal, acrolein diethyl acetal, 2-phenoxyethyl acrylate, tridecafluoro-2-hydroxy nonyl ester, trifluoroethyl methacrylate, allyl-1,3-sultone, glycidyl methacrylate, acrylamide, trifluoroethyl acrylate, (acryloxymethyl) dimethyl methoxysilane, cyanoethyl acrylate, 2-hydroxyethyl acrylate, triallyl benzene-1,3,5-tricarboxylate, 2-hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl acrylate, 1-vinyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and pentafluorophenyl acrylate.

6. The gel positive electrode sheet according to any one of claims 1 to 5, wherein, The gel positive electrode active material layer further contains a positive electrode active material, and the positive electrode active material includes one or more of lithium cobalt oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

7. A preparation method of a gel positive electrode sheet, comprising the following steps: Forming a gel positive electrode active material layer on one surface or multiple surfaces of a positive current collector; The gel positive electrode sheet includes the positive current collector and the gel positive electrode active material layer, the gel positive electrode active material layer contains a gel electrolyte, the gel electrolyte contains a nitrile additive, and the nitrile additive contains a cyano group.

8. The preparation method according to claim 7, wherein, The step of forming the gel positive electrode active material layer on one surface or multiple surfaces of the positive current collector includes: Disposing a positive electrode paste containing a positive electrode active material on one surface or multiple surfaces of the positive current collector, and Drying the positive electrode paste to form an intermediate of the gel positive electrode active material layer; Infiltrating the intermediate of the gel positive electrode active material layer with a gel precursor solution containing the nitrile additive, and curing the gel precursor solution to form the gel positive electrode active material layer.

9. The preparation method according to claim 8, wherein The mass ratio of the nitrile additive in the gel precursor solution is 0.1%-20%.

10. The preparation method according to claim 8 or 9, wherein The mass ratio of the nitrile additive in the gel precursor solution is 0.5%-10%.

11. The preparation method according to any one of claims 8 to 10, wherein, The gel precursor solution further contains monomers of a polymer, and the mass percentage of the monomers of the polymer in the gel precursor solution is 3%-10%.

12. A secondary battery, comprising at least one of the gel positive electrode sheets described in any one of claims 1 to 6 and the gel positive electrode sheets prepared by the preparation method described in any one of claims 7 to 11.

13. An electrical device, comprising at least one of the gel positive electrode sheets described in any one of claims 1 to 6, the gel positive electrode sheets prepared by the preparation method described in any one of claims 7 to 11, and the secondary battery described in claim 12.

Images