Secondary battery and preparation method therefor, and electric device

Abstract

A secondary battery and a preparation method therefor, and an electric device. The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a gel electrolyte, and a solid electrolyte membrane which is of a through hole-free structure; the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprises a positive electrode active material layer; the gel electrolyte is at least located between the positive electrode active material layer and the solid electrolyte membrane and in pores of the positive electrode active material layer; and the gel electrolyte comprises a nitrile additive. In this way, the high-temperature storage performance and the cycle performance of the secondary battery are effectively improved.

Description

Secondary battery, preparation method thereof, and power-consuming device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202410008423.1 filed on January 2, 2024, entitled “Secondary battery, preparation method thereof, 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 secondary battery, a preparation method thereof, and an electrical device thereof. Background Art

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

[0005] Secondary batteries, with their advantages of high operating voltage, no memory effect, high energy density, and light weight, have been widely used in electric vehicles, power tools, mobile phones, laptops, and other fields. With the continuous advancement of technology, the performance of secondary batteries must meet higher requirements. Therefore, further improving the high-temperature storage performance and cycle performance of secondary batteries is particularly important for enhancing the competitiveness of secondary battery products.

[0006] Summary of the Invention

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

[0008] In a first aspect of the present application, a secondary battery is provided, comprising a positive electrode sheet, a negative electrode sheet, a gel electrolyte, and a solid electrolyte membrane having a non-through-hole structure, wherein the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the gel electrolyte is located at least between the positive electrode active material layer and the solid electrolyte membrane and within the pores of the positive electrode active material layer, and the gel electrolyte contains a nitrile additive.

[0009] In the above-mentioned secondary battery, the nitrile additives in the gel electrolyte can effectively stabilize the structure of the positive electrode plate, reduce the dissolution of transition metal ions in the positive electrode plate, improve the high-temperature storage performance of the positive electrode plate, and reduce the gas production of the positive electrode plate. The gel electrolyte can limit the nitrile additives to a certain extent on the side of the solid electrolyte membrane close to the positive electrode plate. Since the solid electrolyte membrane has a non-through-hole structure, it can to a certain extent block the nitrile additives and the transition metal ions in the positive electrode plate from diffusing toward the negative electrode plate, thereby limiting the nitrile additives and transition metal ions to a greater extent on the side of the solid electrolyte membrane close to the positive electrode plate, reducing the diffusion of nitrile additives and transition metal ions to the surface of the negative electrode plate and damaging the negative electrode plate, thereby improving the protection effect on the negative electrode plate. In addition, the gel electrolyte arranged between the positive electrode active material layer and the solid electrolyte membrane can reduce the interface impedance between the two, thereby effectively improving the high-temperature storage performance and cycle performance of the secondary battery.

[0010] In some embodiments, the mass proportion of the nitrile additive in the gel electrolyte is 0.2%-15%, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0011] In some embodiments, the mass proportion of the nitrile additive in the gel electrolyte is 0.5%-10%, 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, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0013] In some embodiments, the thickness of the solid electrolyte membrane is 5 μm-40 μm. A thickness of the solid electrolyte membrane within the above range is conducive to higher capacity of the secondary battery and further improves the high temperature storage performance and cycle performance of the secondary battery.

[0014] In some embodiments, the thickness of the solid electrolyte membrane is 10 μm to 20 μm, thereby facilitating the secondary battery to achieve a higher capacity and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0015] In some embodiments, the tensile strength of the solid electrolyte membrane is 1 MPa-200 MPa. This ensures that the mechanical strength of the solid electrolyte membrane is within a reasonable range, which helps reduce the probability of thermal runaway of the secondary battery and facilitates the preparation of the secondary battery.

[0016] In some embodiments, the ionic conductivity of the solid electrolyte membrane is greater than 0.1 mS / cm, thereby facilitating the transport of active ions and further improving the cycle performance of the secondary battery.

[0017] In some embodiments, the thickness of the gel electrolyte between the positive electrode active material layer and the solid electrolyte membrane is 0.2 μm to 2 μm, thereby shortening the transmission path of active ions and improving the rate performance of the secondary battery.

[0018] In some embodiments, the gel electrolyte further comprises a first polymer, wherein the monomer of the first polymer comprises 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, 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, pentafluorophenol acrylate, and pentaerythritol triacrylate.

[0019] In some embodiments, the solid electrolyte membrane comprises a second polymer, a second electrolyte salt, and an inorganic filler. The inorganic filler in the solid electrolyte membrane can accelerate the dissolution of the second electrolyte salt, improve ionic conductivity, and enhance the tensile strength of the solid electrolyte membrane, thereby further improving the high-temperature storage performance and cycling performance of the secondary battery.

[0020] In some embodiments, the gel electrolyte is located in the pores of the positive electrode active material layer, and the gel electrolyte is wrapped around the surface of the positive electrode sheet.

[0021] In some embodiments, the positive electrode active material layer further comprises a positive electrode active material, wherein the positive electrode active material comprises 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, lithium nickel cobalt aluminum oxide, and modified compounds thereof. This can further improve the high-temperature storage performance and cycle performance of the secondary battery.

[0022] In a second aspect of the present application, a method for preparing a secondary battery is provided, comprising the following steps:

[0023] Infiltrating a positive electrode sheet with a gel precursor solution containing a nitrile additive, wherein the positive electrode sheet includes a positive electrode active material layer;

[0024] covering the surface of the positive electrode active material layer of the positive electrode plate soaked with the gel precursor solution with a solid electrolyte membrane having a non-through-porous structure, and curing the gel precursor solution to form a gel electrolyte containing the nitrile additive, wherein the gel electrolyte is located at least between the positive electrode active material layer and the solid electrolyte membrane and within the pores of the positive electrode active material layer, to obtain a composite intermediate;

[0025] The negative electrode sheet is bonded to the composite intermediate so that the negative electrode sheet is located on a side of the composite intermediate close to the solid electrolyte membrane.

[0026] Thus, the secondary battery can be prepared simply, which is beneficial to the mass production of the secondary battery.

[0027] In some embodiments, the mass percentage of the nitrile additive in the gel precursor solution is 0.2%-15%.

[0028] In some embodiments, the gel precursor solution further comprises a monomer of a first polymer, and the monomer of the first polymer accounts for 2% to 7% by weight in the gel precursor solution.

[0029] The third aspect of the present application provides an electrical device comprising at least one of the secondary battery described in the first aspect of the present application and the secondary battery prepared by the preparation method described in the second aspect of the present application.

[0030] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0031] 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

[0032] 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:

[0033] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0034] FIG. 2 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG. 1 .

[0035] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0036] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0037] FIG5 is an exploded view of the battery pack shown in FIG4 according to an embodiment of the present application.

[0038] 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.

[0039] Description of reference numerals:

[0040] 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

[0041] Below, some embodiments of the secondary battery, its preparation method, and the 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 are 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 the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0042] " 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.

[0043] 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.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] In order to expand the application areas of secondary batteries and improve the competitiveness of secondary battery products, it is urgent to improve the performance of traditional secondary batteries. At present, introducing suitable additives is one of the most cost-effective ways to improve the performance of traditional secondary batteries. However, although some additives can improve the performance of the positive electrode, such as stabilizing the structure of the positive electrode and reducing the dissolution of transition metal ions in the positive electrode, they may damage the surface and structure of the negative electrode, causing unnecessary capacity loss and affecting the cycle performance of the battery. Therefore, how to make these additives exist in the positive electrode and reduce the diffusion of positive electrode additives to the negative electrode is a challenge.

[0050] Based on this, the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, a gel electrolyte and a solid electrolyte membrane with a non-through-hole structure, the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the gel electrolyte is located at least between the positive electrode active material layer and the solid electrolyte membrane and in the pores of the positive electrode active material layer, the gel electrolyte contains a nitrile additive; the nitrile additive in the gel electrolyte can effectively stabilize the structure of the positive electrode sheet, reduce the dissolution of transition metal ions in the positive electrode sheet, improve the high-temperature storage performance of the positive electrode sheet, reduce the gas production of the positive electrode sheet, and the gel electrolyte can bind the nitrile additive to a certain extent. The degree of diffusion of nitrile additives and transition metal ions to the side of the solid electrolyte membrane close to the positive electrode sheet is limited; since the solid electrolyte membrane has a non-through-hole structure, it can block the diffusion of nitrile additives and transition metal ions in the positive electrode sheet to the negative electrode sheet to a certain extent, thereby limiting the nitrile additives and transition metal ions to a greater extent on the side of the solid electrolyte membrane close to the positive electrode sheet, reducing the diffusion of nitrile additives and transition metal ions to the surface of the negative electrode sheet and damaging the negative electrode sheet, thereby improving the protection effect on the negative electrode sheet. In addition, the gel electrolyte arranged between the positive electrode active material layer and the solid electrolyte membrane can reduce the interface impedance between the two, thereby effectively improving the high-temperature storage performance and cycle performance of the secondary battery.

[0051] secondary batteries

[0052] One embodiment of the present application provides a secondary battery, including a positive electrode sheet, a negative electrode sheet, a gel electrolyte, and a solid electrolyte membrane with a non-through-hole structure, wherein the solid electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet includes a positive electrode active material layer, the gel electrolyte is located at least between the positive electrode active material layer and the solid electrolyte membrane and within the pores of the positive electrode active material layer, and the gel electrolyte contains a nitrile additive.

[0053] In the above-mentioned secondary battery, the nitrile additives in the gel electrolyte can effectively stabilize the structure of the positive electrode plate, reduce the dissolution of transition metal ions in the positive electrode plate, improve the high-temperature storage performance of the positive electrode plate, and reduce the gas production of the positive electrode plate. The gel electrolyte can limit the nitrile additives to a certain extent on the side of the solid electrolyte membrane close to the positive electrode plate. Since the solid electrolyte membrane has a non-through-hole structure, it can to a certain extent block the nitrile additives and the transition metal ions in the positive electrode plate from diffusing toward the negative electrode plate, thereby limiting the nitrile additives and transition metal ions to a greater extent on the side of the solid electrolyte membrane close to the positive electrode plate, reducing the diffusion of nitrile additives and transition metal ions to the surface of the negative electrode plate and damaging the negative electrode plate, thereby improving the protection effect on the negative electrode plate. In addition, the gel electrolyte arranged between the positive electrode active material layer and the solid electrolyte membrane can reduce the interface impedance between the two, thereby effectively improving the high-temperature storage performance and cycle performance of the secondary battery.

[0054] Alternatively, a scanning electron microscope (SEM) can be used to observe the cross-section of the positive electrode sheet and the solid electrolyte membrane to determine the relative positions of the gel electrolyte, the positive electrode sheet, and the solid electrolyte membrane, as well as the thickness of each layer. High-performance liquid chromatography or nuclear magnetic resonance spectroscopy can be used to determine the type of nitrile additive in the gel electrolyte. Specific high-performance liquid chromatography can be tested in accordance with the relevant test methods in GB / T 26792-2019, and nuclear magnetic resonance spectroscopy can be tested in accordance with the relevant test methods in GB / T 34059-2017.

[0055] Optionally, whether the solid electrolyte membrane has a through-hole structure can be determined by detecting the air permeability of the solid electrolyte membrane. Specifically, the air permeability of the solid electrolyte membrane is tested using a Wang Yan type air permeability meter (Asahi Seiko model EG01-55-1MR): the solid electrolyte membrane is cut into 60 mm small disc samples and installed in the Wang Yan type air permeability meter to ensure sealing and fixity, the gas pressure is set to 1.21 kilopascals (kPa), and the time taken for 100 milliliters (mL) of air to pass through is recorded to obtain the air permeability of the solid electrolyte membrane. If the air permeability of the solid electrolyte membrane is greater than 1000 secs / 100cc, the solid electrolyte membrane has no through-hole structure, that is, the solid electrolyte membrane has a non-through-hole structure.

[0056] In this application, the unit "secs" refers to seconds, and the unit "cc" refers to cubic centimeters.

[0057] In some embodiments, the mass proportion of the nitrile additive in the gel electrolyte is 0.2%-15%. 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 electrolyte includes but is not limited to: 0.2%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%. Furthermore, the mass proportion of the nitrile additive in the gel electrolyte is 0.5%-10%.

[0058] Optionally, the mass proportion of the nitrile additive in the gel electrolyte can be determined by high performance liquid chromatography, and the specific detection method can be referred to the provisions of the relevant detection method in GB / T 26792-2019.

[0059] In some embodiments, the nitrile additive includes one or more of acetonitrile, propionitrile, butyronitrile, pivalonitrile, capronitrile, malononitrile, succinonitrile, glutaronitrile, and adiponitrile, thereby further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0060] In some embodiments, the thickness of the solid electrolyte membrane is 5μm-40μm. The thickness of the solid electrolyte membrane within the above range is conducive to the secondary battery to exert a higher capacity and further improve the high temperature storage performance and cycle performance of the secondary battery. It is understood that the thickness of the solid electrolyte membrane includes but is not limited to: 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm. Optionally, the thickness of the solid electrolyte membrane is 10μm-20μm.

[0061] In this application, the unit "μm" means micrometer.

[0062] In some embodiments, the tensile strength of the solid electrolyte membrane is 1MPa-200MPa. As a result, the mechanical strength of the solid electrolyte membrane is within a reasonable range, which is beneficial to reducing the probability of thermal runaway of the secondary battery and is beneficial to the preparation of the secondary battery. It is understood that the tensile strength of the solid electrolyte membrane includes but is not limited to: 1MPa, 5MPa, 10MPa, 30MPa, 50MPa, 70MPa, 100MPa, 130MPa, 150MPa, 170MPa, 200MPa. Furthermore, the tensile strength of the solid electrolyte membrane is 10MPa-50MPa.

[0063] In this application, the unit "MPa" refers to megapascals.

[0064] In some embodiments, the ionic conductivity of the solid electrolyte membrane is greater than 0.1mS / cm. The ionic conductivity of the solid electrolyte membrane within the above range is conducive to the transmission of active ions, thereby further improving the cycle performance of the secondary battery. It is understood that the ionic conductivity of the solid electrolyte membrane includes but is not limited to: 0.15mS / cm, 0.2mS / cm, 0.3mS / cm, 0.4mS / cm, 0.5mS / cm, 0.6mS / cm, 0.7mS / cm, 0.8mS / cm, 0.9mS / cm, 1mS / cm. Furthermore, the ionic conductivity of the solid electrolyte membrane is 0.3mS / cm-1mS / cm.

[0065] In this application, the unit "mS / cm" means millisiemens per centimeter.

[0066] In some embodiments, the thickness of the gel electrolyte located between the positive electrode active material layer and the solid electrolyte membrane is 0.2μm-2μm. This is beneficial to shorten the transmission path of active ions and improve the rate performance of the secondary battery. It can be understood that the thickness of the gel electrolyte located between the positive electrode active material layer and the solid electrolyte membrane includes but is not limited to: 0.2μm, 0.4μm, 0.6μm, 0.8μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm. Furthermore, the thickness of the gel electrolyte located between the positive electrode active material layer and the solid electrolyte membrane is 0.5μm-1μm.

[0067] In some embodiments, the gel electrolyte further comprises a first polymer, wherein the monomers of the first 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-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, pentafluorophenol acrylate, and pentaerythritol triacrylate.

[0068] In some embodiments, the gel electrolyte further includes a first organic solvent, a first electrolyte salt, and a first polymer.

[0069] In some embodiments, the first organic solvent includes one or more of a carbonate organic solvent, a carboxylate organic solvent, an ether organic solvent, and a sulfone organic solvent.

[0070] 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, butylene carbonate, fluorodimethyl carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, fluorodiethyl carbonate and fluoroethyl methyl carbonate.

[0071] 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.

[0072] 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.

[0073] In some embodiments, the sulfone organic solvent includes one or more of dimethyl sulfoxide, diphenyl sulfoxide, thionyl chloride, sulfolane, dipropyl sulfone, sulfoxide, thionyl chloride, sulfolane, and dipropyl sulfone.

[0074] In some embodiments, the first electrolyte salt includes a fluorine-containing lithium salt. Fluorine-containing lithium salts have high oxidative stability and better thermal and electrochemical stability in a high-voltage positive electrode active material system.

[0075] In some embodiments, the fluorine-containing lithium salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl imide), lithium bis(fluorosulfonyl imide), lithium bis(trifluoroethoxysulfonyl imide), and lithium bis(trifluoroisopropoxysulfonyl imide).

[0076] In some embodiments, the solid electrolyte membrane comprises a second polymer, a second electrolyte salt, and an inorganic filler. The inorganic filler in the solid electrolyte membrane can accelerate the dissolution of the second electrolyte salt, improve ionic conductivity, and enhance the tensile strength of the solid electrolyte membrane, thereby further improving the high-temperature storage performance and cycling performance of the secondary battery.

[0077] In some embodiments, the mass ratio of the second polymer, the second electrolyte salt, and the inorganic filler is (55-80):(15-40):(2-10). This can improve the tensile strength and ionic conductivity of the solid electrolyte membrane, thereby improving the rate performance of the secondary battery, and further improving the high-temperature storage performance and cycle performance of the secondary battery.

[0078] In some embodiments, the second polymer includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyacrylonitrile, polyethylene glycol, polyvinyl alcohol, polyvinyl chloride, and polypropylene carbonate.

[0079] In some embodiments, the second electrolyte salt includes a lithium salt. Optionally, the lithium salt includes one or more of lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate, lithium borate, lithium chloride, and lithium hexafluorophosphate.

[0080] In some embodiments, the inorganic filler includes SiO2, Al2O3, TiO2, ZnO, Li7La3Zr2O 12 , Li6PS5Cl and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of .

[0081] In some embodiments, the electrolyte includes a third electrolyte salt and a solvent.

[0082] In some embodiments, the third 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).

[0083] 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.

[0084] In some embodiments, the electrolyte may optionally include additives. For example, the 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.

[0085] In some embodiments, the gel electrolyte is located in the pores of the positive electrode active material layer, and the gel electrolyte is wrapped around the surface of the positive electrode sheet.

[0086] In some embodiments, the positive electrode sheet further includes a positive electrode current collector, and the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector, and the positive electrode active material layer contains a positive electrode active material.

[0087] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0088] In some embodiments, the 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 oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their respective modified compounds. Thereby, the high temperature storage performance and cycle performance of the secondary battery can be further improved. Non-limiting examples of lithium cobalt oxide may include but are not limited to LiCoO2; non-limiting examples of lithium nickel oxide may include but are not limited to LiNiO2; non-limiting examples of lithium manganese oxide may include but are not limited to LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt oxide may include but are not limited to LiNi 0.8 Co 0.2 O2; Non-limiting examples of lithium nickel manganese oxides may 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 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 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi0.6 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.

[0089] 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 positive electrode plate 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 content of Li is the initial state of the material. The positive electrode active material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the content of Li in the positive electrode active material contained in the positive electrode plate will usually change. Among them, the content of Li can be measured by molar content, but is not limited to this. Regarding "the content of Li 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.

[0090] 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.

[0091] 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.

[0092] In some embodiments, the positive electrode 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.

[0093] In some embodiments, the positive electrode 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.

[0094] In some embodiments, a positive electrode sheet can be prepared by dispersing the components for preparing the 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 performing drying, cold pressing, and other processes to obtain a positive electrode sheet. 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 compaction density of the positive electrode can be 3.0g / cm 3 -3.6g / cm 3 , optional 3.3g / cm 3 -3.5g / cm 3 .

[0095] In this application, the unit "mPa·s" refers to millipascal·second, and the unit "mg / cm 2 ” refers to mg / cm2.

[0096] In some embodiments, 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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).

[0101] 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.

[0102] 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)).

[0103] 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 .

[0104] In this application, the unit "g / m 2 " refers to grams per square meter, the unit is "g / cm 3 ” refers to grams per cubic centimeter.

[0105] Another embodiment of the present application provides a method for preparing the secondary battery described above, comprising the following steps:

[0106] Infiltrating the positive electrode sheet with a gel precursor solution containing a nitrile additive;

[0107] Covering the solid electrolyte membrane on the surface of the positive electrode active material layer of the positive electrode plate soaked with the gel precursor solution, and solidifying the gel precursor solution to form a gel electrolyte to obtain a composite intermediate;

[0108] The negative electrode sheet is laminated to the composite intermediate so that the negative electrode sheet is located on one side of the solid electrolyte membrane in the composite intermediate.

[0109] This allows for simple preparation of secondary batteries, facilitating their mass production. Furthermore, the positive electrode sheet, solid electrolyte membrane, and gel electrolyte in the composite intermediate can form an integrated structure, reducing the interfacial impedance between the positive electrode sheet and the solid electrolyte membrane. The close contact between the two also enhances adhesion between the positive electrode sheet and the solid electrolyte membrane, preventing displacement, thereby further improving the high-temperature storage and cycling performance of the secondary battery.

[0110] In some embodiments, the mass proportion of the nitrile additive in the gel precursor solution is 0.2%-15%. It is understood that the mass proportion of the nitrile additive in the gel precursor solution includes but is not limited to: 0.2%, 1%, 3%, 5%, 7%, 9%, 11%, 13%, and 15%.

[0111] In some embodiments, the gel precursor solution further comprises a monomer of a first polymer, and the weight percentage of the monomer of the first polymer in the gel precursor solution is 2%-7%. It is understood that the weight percentage of the monomer of the first polymer in the gel precursor solution includes, but is not limited to, 2%, 3%, 4%, 5%, 6%, and 7%.

[0112] In some embodiments, the gel precursor solution further includes a first organic solvent, a first electrolyte salt, and an initiator.

[0113] In some embodiments, the mass percentage of the initiator to the mass percentage of the monomers of the first polymer is 2%-5%. It is understood that the mass percentage of the initiator to the mass percentage of the monomers of the first polymer includes but is not limited to: 2.5%, 3%, 3.5%, 4%, 4.5%, 5%.

[0114] In some embodiments, the initiator includes one or more of an azo initiator and a peroxide initiator.

[0115] In some embodiments, the azo initiator includes one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, and azobisisoheptylonitrile. Alternatively, the peroxide initiator includes one or more of didodecanoyl peroxide and dibenzamide peroxide.

[0116] In some embodiments, the step of forming a solid electrolyte membrane includes:

[0117] mixing a second polymer, a second organic solvent, a second electrolyte salt, and an inorganic filler to obtain a mixed solution;

[0118] The mixed solution is applied and solidified to form a solid electrolyte membrane.

[0119] In some embodiments, the second organic solvent includes one or more of N,N-dimethylformamide, N-methylpyrrolidone, and acetonitrile.

[0120] Yet another embodiment of the present application provides an electrical device, comprising the secondary battery described above.

[0121] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0122] 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.

[0123] Positive electrode

[0124] The above-mentioned positive electrode plate of this application is used.

[0125] Negative electrode

[0126] The above-mentioned negative electrode sheet of this application is used.

[0127] Isolation film

[0128] The solid electrolyte membrane described above in this application is used.

[0129] electrolytes

[0130] The above-mentioned electrolyte of this application is used.

[0131] 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.

[0132] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0133] 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.

[0134] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] The secondary battery may be a battery module 4 or a battery pack 1 .

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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. The mixture was then applied to both sides of the aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet, which was then cut into the corresponding size for later use. The coating amount per unit area on both sides was 0.38g / 1540.25mm 2 In this application, the unit "g" refers to grams, and the unit "mm 2 ” refers to square millimeters.

[0152] (2) Preparation of solid electrolyte membrane

[0153] Polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene were mixed uniformly in a mass ratio of 2:1 to obtain a polymer matrix. The polymer matrix, lithium hexafluorophosphate, and nano-alumina inorganic filler were dissolved in N-methylpyrrolidone in a mass ratio of 62:30:8, with the solute mass fraction in the resulting solution controlled to be 91%, and the mixture was thoroughly stirred to ensure uniform mixing.

[0154] The mixed solution is evenly coated using a preparation device to form a film and then dried. The thickness of the solid electrolyte membrane after drying is controlled to be 20 μm, and the solid electrolyte membrane has no through-hole structure. The dried polymer solid electrolyte membrane is cut into corresponding sizes for later use.

[0155] (3) Preparation of gel precursor solution

[0156] Fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) are prepared in a mass ratio of 2:3:1 and stirred evenly to obtain a positive electrode base electrolyte. Succinonitrile additive is added to the positive electrode base electrolyte and mixed evenly to obtain a nitrile-containing positive electrode base electrolyte, and the mass proportion of succinonitrile in the nitrile-containing positive electrode base electrolyte is 8%. The nitrile-containing positive electrode base electrolyte, pentaerythritol triacrylate (monomer of the first polymer) and initiator azobisisobutyronitrile (AIBN) are mixed evenly in a mass ratio of 95:5:0.2 to obtain a nitrile-containing gel precursor solution. The mass proportion of pentaerythritol triacrylate (monomer of the first polymer) in the gel precursor solution is 5%.

[0157] (4) Preparation of composite intermediates

[0158] The stack of positive electrode sheets was placed in an aluminum-plastic film and injected with a prepared nitrile-containing gel precursor at a rate of 1.5 grams per ampere-hour (g / Ah). A slight negative pressure was applied for 10 minutes (min) to ensure that the nitrile-containing gel precursor fully penetrated the internal pores and surface of the positive electrode sheets. After 6 hours of infiltration, the stacked positive electrode sheets were removed and separated. The prepared solid-state electrolyte membrane was then applied to the positive active material layer of each positive electrode sheet soaked in the gel precursor. The membrane was then transferred to an aluminum-plastic film bag, which was then heat-sealed under negative pressure and infused for another 6 hours. The soaked aluminum-plastic film bag was then secured with a clamp under a pressure of 0.5 MPa to ensure close contact and smoothness between the positive electrode sheet and the solid-state electrolyte membrane. After high-temperature curing at 70 degrees Celsius (°C) for 10 hours, the composite layer of the positive electrode sheet and solid-state electrolyte membrane was removed and recorded as a composite intermediate. The gel electrolyte is located within the pores of the positive electrode active material layer and wrapped around the surface of the positive electrode sheet. The thickness of the gel electrolyte between the positive electrode active material layer and the solid electrolyte membrane is 0.8 μm. Succinonitrile accounts for 7.6% by weight of the gel electrolyte.

[0159] (5) Preparation of negative electrode sheet

[0160] A silicon-carbon composite negative electrode material (20% silicon content), a conductive agent (acetylene black), and a 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 a copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet. The coating amount per unit area on both sides was 0.117g / 1540.25mm 2 .

[0161] (6) Preparation of negative electrode electrolyte

[0162] Carbonate solvent ethylene carbonate (EC), carbonate solvent diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of EC:DEC:EMC=1:1:1, stirred evenly, and then 1.0 mol / L (mol / L) of lithium bis(trifluoromethylsulfonyl)imide was added to dissolve.

[0163] (7) Preparation of lithium-ion batteries

[0164] The composite intermediate and the negative electrode sheet were stacked, with the negative electrode sheet positioned on the side of the solid electrolyte membrane away from the positive electrode sheet. A negative electrolyte solution was injected at a rate of 1.0 g / Ah. The battery was sealed under negative pressure and allowed to soak for 12 hours to produce a lithium-ion battery.

[0165] Example 2-17

[0166] Basically the same as Example 1, except that: the type of nitrile additive, the mass proportion of the nitrile additive in the gel electrolyte, the mass proportion of the nitrile additive in the nitrile-containing positive electrode base electrolyte, the mass proportion of the first polymer monomer in the gel precursor solution, the thickness of the gel electrolyte located between the positive electrode active material layer and the solid electrolyte membrane, the thickness of the solid electrolyte membrane, the mass proportion of the inorganic filler in the solid electrolyte membrane, and the mass ratio of the polymer matrix, lithium hexafluorophosphate and the inorganic filler are changed, as shown in Table 1.

[0167] In Examples 2-7, when the mass proportion of nitrile additives in the gel electrolyte is changed, since the mass proportion of nitrile additives in the gel electrolyte is the same as the mass proportion of nitrile additives in the gel precursor, and in Examples 2-7, the nitrile-containing positive electrode base electrolyte, pentaerythritol triacrylate (monomer of the first polymer) and the initiator azobisisobutyronitrile (AIBN) are mixed in a mass ratio of 95:5:0.2 to prepare the nitrile-containing gel precursor, the mass proportion of nitrile additives in the nitrile-containing positive electrode base electrolyte can be calculated.

[0168] Comparative Example 1

[0169] (1) Preparation of positive electrode sheet

[0170] Lithium cobalt oxide, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed thoroughly in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3. The mixture was then coated on both sides of the aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet, which was then cut into the corresponding size for later use. The coating amount per unit area on both sides was 0.38g / 1540.25mm 2 .

[0171] (2) Isolation membrane

[0172] The isolation membrane is a polyolefin membrane coated with double-sided aluminum oxide layers.

[0173] (3) Preparation of basic electrolyte

[0174] Carbonate solvent ethylene carbonate (EC), carbonate solvent diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of EC:DEC:EMC=1:1:1, stirred evenly, and then 1.0 mol / L lithium bis(trifluoromethylsulfonyl)imide was added to dissolve.

[0175] (4) Preparation of negative electrode sheet

[0176] A silicon-carbon composite negative electrode material (20% silicon content), a conductive agent (acetylene black), and a 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 a copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet. The coating amount per unit area on both sides was 0.117g / 1540.25mm 2 .

[0177] (5) Preparation of lithium-ion batteries

[0178] The positive electrode sheet, separator, and negative electrode sheet were stacked and injected with a base electrolyte at a rate of 1.6 g / Ah. The battery was sealed under negative pressure and soaked for 12 hours to obtain a lithium-ion battery.

[0179] Comparative Example 2

[0180] (1) Preparation of positive electrode sheet

[0181] Lithium cobalt oxide, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed thoroughly in an N-methylpyrrolidone solvent system at a weight ratio of 94:3:3. The mixture was then coated on both sides of the aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet, which was then cut into the corresponding size for later use. The coating amount per unit area on both sides was 0.38g / 1540.25mm 2 .

[0182] (2) Preparation of solid electrolyte membrane

[0183] Polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene were mixed uniformly in a mass ratio of 2:1 to obtain a polymer matrix. The polymer matrix, lithium hexafluorophosphate, and nano-alumina inorganic filler were dissolved in N-methylpyrrolidone in a mass ratio of 62:30:8, with the solute mass fraction in the resulting solution controlled to be 91%, and the mixture was thoroughly stirred to ensure uniform mixing.

[0184] The mixed solution is evenly coated using a preparation device to form a film and then dried. The thickness of the solid electrolyte membrane after drying is controlled to be 20 μm, and the solid electrolyte membrane has no through-hole structure. The dried polymer solid electrolyte membrane is cut into corresponding sizes for later use.

[0185] (3) Preparation of negative electrode sheet

[0186] A silicon-carbon composite negative electrode material (20% silicon content), a conductive agent (acetylene black), and a 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 a copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet. The coating amount per unit area on both sides was 0.117g / 1540.25mm 2 .

[0187] (4) Preparation of electrolyte

[0188] The carbonate solvent ethylene carbonate (EC), the carbonate solvent diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:DEC:EMC = 1:1:1, stirred evenly, and then 1.0 mol / L lithium bis(trifluoromethylsulfonyl)imide was added to dissolve. Then, succinonitrile additive was added and stirred evenly to obtain an electrolyte containing a nitrile additive, wherein succinonitrile accounted for 8% by weight of the electrolyte.

[0189] (5) Preparation of lithium-ion batteries

[0190] The positive electrode sheet, solid electrolyte membrane, and negative electrode sheet were stacked, with the solid electrolyte membrane positioned between the positive and negative electrode sheets. Electrolyte was injected at a rate of 1.6 g / Ah. The battery was sealed under negative pressure and allowed to soak for 12 hours to produce a lithium-ion battery.

[0191] Performance Testing

[0192] (1) Tensile strength test of solid electrolyte membrane

[0193] For testing, the solid electrolyte membrane was cut into strips 1.5 cm wide and 20 cm long. The membrane was then secured to the fixture of a universal tensile machine to ensure uniform force across the transverse cross-section. The membrane's width and thickness were input, and a tensile rate of 10 mm / min was used. The relationship between tension and elongation was calculated, yielding a tensile strength curve. The maximum tensile strength was used as the reference standard.

[0194] (2) Ionic conductivity test of solid electrolyte membrane

[0195] The solid electrolyte membrane was punched into small discs with a diameter of 20 mm. Its thickness, d, was measured. The discs were then sandwiched on both sides with lithium sheets of the same size, with the diameter of the lithium sheets smaller than that of the discs, and placed in a buckle battery. Electrochemical impedance spectroscopy (EIS) was used to measure the Nyquist plots at a test voltage of 10 millivolts (mV) and a test frequency of 0.1 Hz to 100 kilohertz (kHz). The plots were analyzed using Zview software using the equivalent circuit curve fitting method. The intersection of the straight line and the horizontal axis was designated R. Ionic conductivity λ = d / R (where R represents the ionic resistance and S represents the area of ​​the lithium sheet).

[0196] (3) High temperature storage test

[0197] At 25°C, the lithium-ion battery is charged to 4.5 volts (V) at a rate of 0.33C, then charged at a constant voltage until the current is less than 0.05C, and then discharged to 2.5V at a rate of 0.33C. The initial discharge capacity is measured as C1. The lithium-ion battery is adjusted to a 100% charged state and then placed in a 60°C oven for high-temperature storage. After storage for 30 days, it is taken out and cooled to room temperature. It is then charged to 4.5V at a rate of 0.33C, then charged at a constant voltage until the current is less than 0.05C, and then discharged to 2.5V at a rate of 0.33C. The initial discharge capacity is measured as C2.

[0198] High temperature storage capacity retention rate (%) = C2 / C1×100%.

[0199] (4) Cyclic performance test

[0200] At 45°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 0.5C. 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.

[0201] 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.

[0202] Table 1

[0203] As can be seen from Table 1, compared with Comparative Examples 1-2, the high-temperature storage capacity retention rate of the battery of Example 1-17 is higher, and the number of cycles when the battery discharge capacity decays to 80% of the initial capacity is higher, indicating that the combination of the positive electrode sheet, the negative electrode sheet, the solid electrolyte membrane and the gel electrolyte containing nitrile additives in the battery of Example 1-17 effectively improves the high-temperature storage performance and cycle performance of the secondary battery.

[0204] 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.

[0205] 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 secondary battery includes a positive electrode plate, a negative electrode plate, a gel electrolyte, and a solid electrolyte membrane having a non-through hole structure. The solid electrolyte membrane is located between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a positive electrode active material layer. The gel electrolyte is at least located between the positive electrode active material layer and the solid electrolyte membrane and in the pores of the positive electrode active material layer. The gel electrolyte contains a nitrile additive.

2. The secondary battery according to claim 1, wherein, The mass ratio of the nitrile additive in the gel electrolyte is 0.2%-15%.

3. The secondary battery according to claim 1 or 2, wherein, The mass ratio of the nitrile additive in the gel electrolyte is 0.5%-10%.

4. The secondary battery 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, glutarodinitrile, and adiponitrile.

5. The secondary battery according to any one of claims 1 to 4, wherein, The thickness of the solid electrolyte membrane is 5 μm - 40 μm.

6. The secondary battery according to any one of claims 1 to 5, wherein, The thickness of the solid electrolyte membrane is 10 μm - 20 μm.

7. The secondary battery according to any one of claims 1 to 6, wherein, The tensile strength of the solid electrolyte membrane is 1 MPa - 200 MPa.

8. The secondary battery according to any one of claims 1 to 7, wherein, The ionic conductivity of the solid electrolyte membrane > 0.1 mS / cm.

9. The secondary battery according to any one of claims 1 to 8, wherein, The thickness of the gel electrolyte located between the positive electrode active material layer and the solid electrolyte membrane is 0.2 μm - 2 μm.

10. The secondary battery according to any one of claims 1 to 9, wherein, The gel electrolyte further contains a first polymer. The monomers of the first 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-sulfonic acid lactone, glycidyl methacrylate, acrylamide, trifluoroethyl acrylate, (acryloxymethyl)dimethylmethoxysilane, cyanoethyl acrylate, 2-hydroxyethyl acrylate, triallyl benzene-1,3,5-tricarboxylate, 2-hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl acrylate, pentafluorophenyl acrylate, and pentaerythritol triacrylate.

11. The secondary battery according to any one of claims 1 to 10, wherein, The solid electrolyte membrane contains a second polymer, a second electrolyte salt, and an inorganic filler.

12. The secondary battery according to any one of claims 1 to 11, wherein, The gel electrolyte is located in the pores of the positive electrode active material layer, and the gel electrolyte wraps the surface of the positive electrode plate.

13. The secondary battery according to any one of claims 1 to 12, wherein, The positive electrode active material layer further contains a positive electrode active material. The positive electrode active material includes 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, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

14. A method for preparing a secondary battery includes the following steps: Infiltrating a positive electrode plate including a positive electrode active material layer with a gel precursor solution containing a nitrile additive; Cover a solid electrolyte membrane with a non-through-hole structure on the surface of the positive electrode active material layer of the positive electrode sheet infiltrated with the gel precursor solution, and cure the gel precursor solution to form a gel electrolyte containing the nitrile additive. The gel electrolyte is at least located between the positive electrode active material layer and the solid electrolyte membrane and in the pores of the positive electrode active material layer to obtain a composite intermediate; Attach the negative electrode sheet to the composite intermediate, with the negative electrode sheet located on the side of the composite intermediate close to the solid electrolyte membrane.

15. The preparation method according to claim 14, wherein, The mass ratio of the nitrile additive in the gel precursor solution is 0.2%-15%.

16. The preparation method according to claim 14 or 15, wherein The gel precursor solution further contains a monomer of a first polymer, and the mass ratio of the monomer of the first polymer in the gel precursor solution is 2%-7%.

17. An electrical device, comprising at least one of the secondary batteries according to any one of claims 1 to 13 and the secondary batteries prepared by the preparation method according to any one of claims 14 to 16.

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