Lithium ion battery and manufacturing method therefor, and electric device

Abstract

A lithium ion battery and a manufacturing method therefor, and an electric device, relating to the technical field of secondary batteries. The lithium ion battery comprises a positive electrode sheet, an electrolyte, and a negative electrode sheet; the positive electrode sheet comprises a positive electrode active material layer; the positive electrode active material layer comprises a gel; the gel comprises an electrolyte salt, a solvent, and a polymer; and the solvent and the electrolyte salt can form an eutectic electrolyte. The lithium ion battery has an excellent cycle life.

Description

Lithium-ion batteries, their preparation methods, and electrical equipment

[0001] Priority information

[0002] This application claims priority and benefit to patent application 202411662439.0, filed with the China National Intellectual Property Administration on November 19, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of secondary batteries, specifically relating to a lithium-ion battery and its preparation method and electrical equipment. Background Technology

[0004] Secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0005] During battery cycling, the contact between the positive electrode active material particles and the solid electrolyte particles inside the positive electrode sheet faces the problem of poor contact caused by the volume expansion and contraction of the positive electrode active material. This will increase the interfacial impedance and seriously affect the cycle performance of the lithium-ion battery. Summary of the Invention

[0006] In view of the technical problems existing in the background art, this application provides a lithium-ion battery, which aims to improve the cycle performance of lithium-ion batteries.

[0007] To achieve the above objectives, the first aspect of this application proposes a lithium-ion battery, the lithium-ion battery comprising a positive electrode, an electrolyte, and a negative electrode, the positive electrode comprising a positive active material layer, the positive active material layer comprising a gel, the gel comprising an electrolyte salt, a solvent, and a polymer, wherein the solvent and the electrolyte salt can form a eutectic electrolyte.

[0008] This application includes at least the following beneficial effects: In the lithium-ion battery of this application, the eutectic electrolyte formed by the solvent and the electrolyte salt can serve as a wetting agent for the solid-solid interface of the positive electrode active material, thereby reducing the interfacial impedance. The polymer can confine the eutectic electrolyte within the positive electrode sheet to form a gel, which can improve the cycle performance of the lithium-ion battery containing it.

[0009] In some embodiments, the mass ratio of the electrolyte salt to the solvent is (3-7):(3-7). The electrolyte salt and the solvent can form a eutectic electrolyte within a certain mass ratio range.

[0010] In some embodiments, the mass ratio of the electrolyte salt, the solvent, and the polymer is (27-67.9):(27-67.9):(3-10). Thus, the polymer network can bind the eutectic electrolyte composed of the electrolyte salt and solvent, forming a gel and inhibiting its flow to maintain good interfacial wetting properties.

[0011] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. Thus, the lithium salt and solvent form a eutectic electrolyte, promoting the dissociation of the lithium salt and generating lithium ions that participate in ion conduction, thereby constructing a lithium ion percolation network and improving interfacial contact.

[0012] In some embodiments, one or more of the following conditions are met: the solvent has a melting point of 30°C-120°C under standard atmospheric pressure; the eutectic electrolyte has a melting point of -30°C-20°C under standard atmospheric pressure; and the functional groups of the solvent include one or more of cyano, sulfone, carbonyl, amide, or ether groups. Thus, the solvent can dissociate lithium salts to form solvated lithium ions, constructing a percolating lithium-conducting network, which can improve the cycle performance of lithium-ion batteries containing it.

[0013] In some embodiments, the solvent includes one or more of sulfolane, dibutyl sulfone, dimethyl sulfone, diethyl sulfone, methyl sulfone, succinic acid, ethylene glycol dimethyl ether oligomer, acetamide, trifluoromethanesulfonamide, or ethylene carbonate.

[0014] In some embodiments, the polymer has a weight-average molecular weight of 5,000-15,000. Thus, the polymer network formed by in-situ gelation can confine the eutectic electrolyte within the positive electrode active layer to maintain good interfacial ion contact.

[0015] In some embodiments, the polymer includes one or more of acrylate polymers or polyolefins.

[0016] In some embodiments, one or more of the following conditions are met: the acrylate polymer includes one or more of polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate or polybutyl methacrylate; the polyolefin includes one or more of polyethylene, polypropylene, polybutene or polystyrene.

[0017] In some embodiments, the positive electrode active material layer further includes a positive electrode active material, a conductive agent, and a binder.

[0018] In some embodiments, based on the total mass of the positive electrode active material layer, the mass percentages of each component are as follows: positive electrode active material 70%-90%, conductive agent 1.5%-3%, binder 1%-2%, and gel 5%-20%; wherein the gel comprises the electrolyte salt, the solvent, and the polymer. Thus, the gel forms a lithium-conducting permeation network within the positive electrode active layer, improving solid-solid interface contact, reducing interfacial impedance, and enhancing the cycle performance of the lithium-ion battery containing it.

[0019] In some embodiments, the positive electrode active material comprises one or more of lithium phosphates or lithium transition metal oxides with an olivine structure.

[0020] In some embodiments, one or more of the following conditions are met: the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers; the binder includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0021] In some embodiments, the positive electrode active material layer further includes a solid electrolyte. Thus, the solid electrolyte can serve as an additional lithium-conducting medium, participating in the construction of the lithium-conducting network within the active layer, thereby improving the cycle performance of lithium-ion batteries containing it.

[0022] In some embodiments, the mass percentage of the solid electrolyte is less than or equal to 10% based on the total mass of the positive electrode active material layer.

[0023] In some embodiments, the electrolyte includes a solid electrolyte.

[0024] In some embodiments, the positive electrode has a loading capacity of 2.5 mAh / cm³. 2 -3.5mAh / cm 2 .

[0025] In some embodiments, the negative electrode sheet includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, or lithium metal.

[0026] In some embodiments, the negative electrode comprises lithium metal.

[0027] In a second aspect, this application proposes a method for preparing a lithium-ion battery, comprising: preparing a positive electrode active material layer to obtain a positive electrode sheet, wherein the positive electrode active material layer comprises a gel, the gel comprises an electrolyte salt, a solvent, and a polymer, wherein the solvent and the electrolyte salt can form a eutectic electrolyte; and assembling the positive electrode sheet, the electrolyte, and the negative electrode sheet to obtain a lithium-ion battery. Therefore, the lithium-ion battery prepared in this application exhibits excellent cycle performance.

[0028] In some embodiments, the positive electrode sheet is prepared by the following method: mixing an electrolyte salt, a solvent, a polymer monomer, a crosslinking agent, and an initiator, and compounding them onto at least one side of a positive current collector to obtain a positive electrode sheet precursor; and polymerizing the polymer monomer into a polymer to obtain the positive electrode sheet.

[0029] In some embodiments, polymerizing the monomers of the polymer into a polymer includes heating or irradiating the positive electrode precursor with ultraviolet light to polymerize the monomers of the polymer into a polymer.

[0030] In some embodiments, one or more of the following conditions are met: the heating temperature is 50°C-80°C; the heating time is 8h-15h; and the ultraviolet light irradiation time is 5s-30s.

[0031] In some embodiments, one or more of the following conditions are met: the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, or benzophenone; the crosslinking agent includes one or more of ethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, or trimethylolpropane trimethacrylate; and the mass ratio of the polymer monomer, the crosslinking agent, and the initiator is (60-70):(39-25):(1-5).

[0032] In a third aspect of this application, this application proposes an electrical device comprising the lithium-ion battery described in the first aspect of this application, or a lithium-ion battery prepared using the method described in the second aspect.

[0033] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0035] Figure 1 is a schematic diagram of a battery according to one embodiment of this application.

[0036] Figure 2 is an exploded view of the battery according to one embodiment of this application shown in Figure 1.

[0037] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0038] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0039] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0040] Figure 6 is a schematic diagram of an electrical device in which a battery is used as a power source according to an embodiment of this application.

[0041] Explanation of reference numerals in the attached drawings: 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Battery module; 3. Battery pack; 31. Upper casing; 32. Lower casing.

[0042] Detailed description of the invention

[0043] The embodiments of the technical solution of this application are described in detail below. These embodiments are only used to more clearly illustrate the technical solution of this application, and are therefore merely examples and should not be used to limit the scope of protection of this application.

[0044] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0045] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Currently, judging from market trends, the application of rechargeable batteries is becoming increasingly widespread. Rechargeable batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace, among other fields.

[0050] During battery cycling, the contact between the positive electrode active material particles and the solid electrolyte particles inside the positive electrode sheet faces the problem of poor contact caused by the volume expansion and contraction of the positive electrode active material. This will increase the interfacial impedance and seriously affect the cycle performance of the lithium-ion battery.

[0051] In some embodiments, an ionic liquid electrolyte can be added as a wetting agent to improve solid-solid contact. However, the cations of ionic liquids include lithium ions and large cations (such as quaternary ammonium salt ions, imidazole salt ions, pyrrole salt ions, etc.). Large cations can greatly hinder the migration of lithium ions, which is not conducive to the migration of lithium ions inside the positive electrode active layer, resulting in greater interfacial impedance.

[0052] In the lithium-ion battery of this application embodiment, due to the interaction force between the electrolyte salt and the solvent in the positive electrode active material layer, the solvent and electrolyte salt can form a eutectic electrolyte. The eutectic electrolyte is liquid at room temperature and pressure and can act as a wetting agent for the solid-solid interface contact of the positive electrode active material, maintaining good ion contact at the interface, reducing interfacial impedance, and achieving fast ion conduction. Compared with ionic liquids, the eutectic electrolyte of this application does not have the effect of large cations hindering lithium-ion migration, which makes the lithium-ion battery have excellent cycle performance. In addition, the eutectic electrolyte has fluidity, and it is easy to be partially squeezed out of the positive electrode active material layer under the action of internal stress caused by battery expansion during battery cycling. This application embodiment uses a polymer to solidify the eutectic electrolyte in the positive electrode active layer to form a gel, thereby reducing its fluidity and reducing the risk of it being squeezed out of the positive electrode active material layer by battery expansion volume changes. This is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge inside the positive electrode active material layer, thereby further improving the cycle performance of the battery.

[0053] The lithium-ion batteries disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0054] The first aspect of this application discloses a lithium-ion battery, including a positive electrode, an electrolyte, and a negative electrode. The positive electrode includes a gel, the gel includes a positive active material layer, and the positive active material layer includes an electrolyte salt, a solvent, and a polymer, wherein the solvent and the electrolyte salt can form a eutectic electrolyte.

[0055] In the lithium-ion battery of this application embodiment, due to the interaction force between the electrolyte salt and the solvent in the positive electrode active material layer, the solvent and electrolyte salt can form a eutectic electrolyte. The eutectic electrolyte is liquid at room temperature and pressure and can act as a wetting agent for the solid-solid interface contact of the positive electrode active material, maintaining good ion contact at the interface, reducing interfacial impedance, and achieving fast ion conduction. Compared with ionic liquids, the eutectic electrolyte of this application does not have the effect of large cations hindering lithium-ion migration, resulting in excellent cycle performance of the lithium-ion battery. In addition, considering that the eutectic electrolyte has fluidity, it is easy to be partially squeezed out of the positive electrode active material layer during battery cycling under the action of internal stress caused by battery expansion. This application embodiment uses a polymer to solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity and forming a gel. This reduces the risk of it being squeezed out of the positive electrode active material layer due to battery expansion volume changes, which is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge inside the positive electrode active material layer, thereby further improving the cycle performance of the battery.

[0056] It is understood that in the embodiments of this application, a eutectic electrolyte refers to a mixture where both the electrolyte salt and solvent are solids at room temperature and standard atmospheric pressure, but can be converted into a liquid at room temperature. Its freezing point is significantly lower than the melting points of each pure component, with the mixture having the lowest melting point. Whether the solvent and electrolyte salt form a eutectic electrolyte can be determined by the following methods:

[0057] The battery is disassembled to obtain the positive electrode. The fluid dynamic eutectic electrolyte inside the positive electrode is squeezed out and collected by extrusion. Infrared spectroscopy characterization is performed, and characteristic vibration peak signals are detected to determine the composition of the eutectic electrolyte.

[0058] It is understandable that a gel refers to a polymer molecule that, under certain conditions, connects to form a three-dimensional network structure, with the voids filled with a liquid (eutectic electrolyte) serving as the dispersion medium. The gel in the positive electrode can be determined using the following methods:

[0059] The battery is disassembled to obtain the positive electrode sheet. The morphology and elemental composition of the surface and cross-section of the positive electrode sheet are characterized by scanning electron microscopy combined with energy dispersive spectroscopy. The gel network structure and its composition can be observed.

[0060] Electrolyte salts are salts that can conduct active metal ions; therefore, the electrolyte salt is a lithium salt. The electrolyte salt and solvent in the positive electrode can be determined using the following methods:

[0061] The battery is disassembled to obtain the positive electrode. The fluid dynamics of the eutectic electrolyte inside the positive electrode are extruded and collected through compression. Infrared spectroscopy characterization is performed, and characteristic vibrational peak signals are detected to determine the solvent composition of the eutectic electrolyte. Inductively coupled plasma atomic emission spectrometry (ICP-AES) is used to detect the signals of metal ions in this eutectic electrolyte to distinguish the active metal ions of different secondary batteries, such as lithium ions and sodium ions.

[0062] In some embodiments of this application, the mass ratio of the electrolyte salt to the solvent is (3-7):(3-7). For example, the mass ratio can be 3:7, 4:6, 5:5, 6:4, 7:3, etc. Specifically, by controlling the mass ratio of the electrolyte salt to the solvent within the above range, the two can better form a eutectic electrolyte. The eutectic electrolyte can act as a wetting agent for the solid-solid interface contact of the positive electrode active material, maintaining good ion contact at the interface, reducing interface impedance, and achieving fast ion conduction, thus enabling the lithium-ion battery to have excellent cycle performance.

[0063] In some embodiments of this application, the mass ratio of the electrolyte salt, the solvent, and the polymer is (27-67.9):(27-67.9):(3-10). For example, the mass ratio of the three can be 27:63:10, 29.1:67.9:3, 63:27:10, 67.9:29.1:3, 50:45:5, etc. By controlling the mass ratio of the three within the above range, the electrolyte salt and solvent form a eutectic electrolyte, which is sufficient to improve the wetting performance between the positive electrode active materials and enhance their solid-solid interface contact. Furthermore, the polymer is sufficient to solidify the eutectic electrolyte within the positive electrode active layer to form a gel, thereby reducing its fluidity. This further enhances the effects of the three components and further improves the cycle performance of the lithium-ion battery.

[0064] It is understood that the "mass ratio of electrolyte salt, solvent, and polymer" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0065] The battery was disassembled to obtain the positive electrode sheet, and the positive electrode active material layer was scraped to obtain powder. The mass ratio of each component was determined by mass spectrometry.

[0066] In some embodiments of this application, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate. These electrolyte salts exhibit excellent lithium-ion conductivity and readily form eutectic electrolytes with solvents, improving the wetting properties between positive electrode active materials, enhancing solid-solid interface contact, maintaining good ion contact at the interface, reducing interfacial impedance, and achieving fast ion conduction, thus enabling lithium-ion batteries to possess excellent cycle performance.

[0067] In some embodiments of this application, the melting point of the solvent is 30℃-120℃ under standard atmospheric pressure. For example, the melting point of the solvent under standard atmospheric pressure can be 30℃-1119℃, 40℃-110℃, 50℃-100℃, 60℃-90℃, 70℃-80℃, etc. Standard atmospheric pressure refers to the air pressure at sea level under standard atmospheric conditions, which is 101.325 kPa. Controlling the melting point of the solvent within the above range makes the melting point of the formed eutectic electrolyte even lower, which facilitates the formation of a eutectic electrolyte with the electrolyte salt. This can improve the wetting performance between the positive electrode active materials, enhance their solid-solid interface contact, maintain good ion contact at the interface, reduce interface impedance, achieve fast ion conduction, and enable the lithium-ion battery to have excellent cycle performance.

[0068] In some embodiments of this application, the melting point of the eutectic electrolyte is -30°C to 20°C under standard atmospheric pressure. For example, the melting point of the eutectic electrolyte can be -30°C to 19°C, -25°C to 15°C, -20°C to 10°C, -10°C to 0°C, etc. This can improve the wetting performance between the positive electrode active materials, enhance their solid-solid interface contact, maintain good ion contact at the interface, reduce interface impedance, achieve fast ion conduction, and enable the lithium-ion battery to have excellent cycle performance.

[0069] It is understood that the melting points of solvents and eutectic electrolytes are well-known definitions in the art and can be determined using methods known in the art, such as the following methods:

[0070] The melting point is obtained by testing the thermogravimetric analysis of the solvent or eutectic electrolyte using a differential scanning calorimeter (model DSC600).

[0071] In some embodiments of this application, the functional groups of the solvent include one or more of cyano, sulfone, carbonyl, amide, or ether groups. These groups contain lone pairs of electrons and can combine with active metal ions such as lithium ions. At the same time, the anions of the electrolyte salt can interact with the HC of the solvent, thereby dissociating the lithium salt and forming a low-co-solubility electrolyte, which makes the lithium-ion battery have excellent cycle performance.

[0072] In some embodiments of this application, the solvent includes one or more of sulfolane, dibutyl sulfone, dimethyl sulfone, diethyl sulfone, methyl sulfone, succinic acid, ethylene glycol dimethyl ether oligomer, acetamide, trifluoromethanesulfonamide, or ethylene carbonate. Specifically, the above solvents can form a eutectic electrolyte with electrolyte salts such as lithium salts, which can improve the wetting performance between positive electrode active materials, enhance their solid-solid interface contact, maintain good ion contact at the interface, reduce interfacial impedance, achieve fast ion conduction, and enable lithium-ion batteries to have excellent cycle performance.

[0073] In some embodiments of this application, the weight-average molecular weight of the polymer is 5000-15000. For example, the weight-average molecular weight of the polymer can be 5000-14000, 6000-13000, 7000-12000, 8000-11000, 9000-10000, etc. Controlling the weight-average molecular weight of the polymer within the above range is beneficial for the polymer to form a gel. The polymer is sufficient to solidify the eutectic electrolyte within the positive electrode active layer, forming a gel, thereby reducing its fluidity and the risk of it being squeezed out of the positive electrode active material layer due to battery expansion volume changes. This is beneficial for improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge within the positive electrode active material layer, thereby further improving the cycle performance of the battery.

[0074] It is understood that "weight-average molecular weight of polymer" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0075] The "weight-average molecular weight of the polymer" can be tested using gel permeation chromatography.

[0076] In some embodiments of this application, the polymer includes one or more of acrylate polymers or polyolefins. The gel formed by the polymer is sufficient to solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity and forming a gel. This reduces the risk of the eutectic electrolyte being squeezed out of the positive electrode active material layer due to battery expansion and volume changes, which is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge inside the positive electrode active material layer, thereby further improving the cycle performance of the battery.

[0077] In some embodiments of this application, the acrylate polymer includes one or more of polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, or polybutyl methacrylate. The gel formed by these polymers is sufficient to solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity and the risk of it being squeezed out of the positive electrode active material layer due to battery expansion. This improves the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge within the positive electrode active material layer, further enhancing the battery's cycle performance.

[0078] In some embodiments of this application, the polyolefin includes one or more of polyethylene, polypropylene, polybutene, or polystyrene. The gel formed by the above polymers is sufficient to solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity and the risk of it being squeezed out of the positive electrode active material layer due to battery expansion volume changes. This is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge within the positive electrode active material layer, thereby further improving the cycle performance of the battery.

[0079] In some embodiments of this application, the positive electrode active material layer further includes a positive electrode active material, a conductive agent, and a binder. Thus, the positive electrode active material can provide active metal ions (such as lithium ions), the conductive agent can improve the conductivity of the positive electrode sheet, and the binder can improve the adhesion of the positive electrode active material layer.

[0080] In some embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of each component is as follows: positive electrode active material 70%-90%, conductive agent 1.5%-3%, binder 1%-2%, gel 5%-20%; wherein, the gel includes the electrolyte salt, the solvent, and the polymer. As an example, based on the total mass of the positive electrode active material layer, the mass percentage of the positive electrode active material can be 70%-89%, 75%-85%, 77%-80%, etc.; the mass percentage of the conductive agent can be 1.5%-2.9%, 1.8%-2.7%, 2%-2.5%, etc.; the mass percentage of the binder can be 1%-1.9%, 1.1%-1.8%, 1.2%-1.7%, 1.3%-1.6%, 1.4%-1.5%, etc.; and the mass percentage of the gel can be 5%-19%, 7%-17%, 10%-15%, etc. By controlling the content of each component within the above ranges, the electrolyte salt and solvent form a eutectic electrolyte, which is sufficient to improve the wetting performance between the positive electrode active materials and enhance their solid-solid interface contact. Furthermore, the polymer is sufficient to solidify the eutectic electrolyte within the positive electrode active layer to form a gel, thereby reducing its fluidity. This can further enhance the effects of the three components and further improve the cycle performance of the lithium-ion battery.

[0081] It is understood that "the mass percentage of each component based on the total mass of the positive electrode active material layer" is a well-known definition in the art and can be determined using methods known in the art. For example, the following methods can be used for determination:

[0082] The battery was disassembled to obtain the positive electrode sheet, and the positive electrode active material layer was scraped to obtain powder. The mass ratio of each component was determined by mass spectrometry.

[0083] In some embodiments of this application, the positive electrode active material includes one or more of lithium phosphates or lithium transition metal oxides with an olivine structure.

[0084] In some embodiments of this application, the conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0085] In some embodiments of this application, the adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0086] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active metal ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0087] In some embodiments of this application, the positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector.

[0088] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0089] In some embodiments of this application, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0090] In some embodiments of this application, when the battery is a lithium secondary battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries.

[0091] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The modified compounds of the above materials may be for doping modification and / or surface coating modification of the materials.

[0092] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Li content changes when the positive electrode active material is applied to the battery system.

[0093] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0094] In some embodiments of this application, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0095] In some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0096] In some embodiments of this application, the positive electrode active material layer further includes a solid electrolyte. The solid electrolyte can improve the ionic conductivity of the positive electrode active material layer, and as an additional lithium-conducting medium, participate in the construction of the lithium-conducting network inside the active layer, thereby further improving the cycle performance of the lithium-ion battery.

[0097] In some embodiments of this application, based on the total mass of the positive electrode active material layer, the mass percentage of the solid electrolyte is less than or equal to 10%, for example, it can be 0.1%-9.9%, 1%-9%, 2%-8%, 3%-7%, 4%-6%, etc. Controlling the content of solid electrolyte in the positive electrode active material layer within the above range is sufficient to improve the ionic conductivity of the positive electrode active material layer without adding too much and affecting the energy density of the lithium-ion battery.

[0098] This application does not limit the type of solid electrolyte. As an example, solid electrolyte may include at least one of oxide solid electrolyte, sulfide solid electrolyte, polymer solid electrolyte, and composite solid electrolyte.

[0099] As an example, oxide solid electrolytes may include at least one of NASICON-type solid electrolytes, garnet-type solid electrolytes, and perovskite-type solid electrolytes. NASICON-type solid electrolytes may include lithium aluminum titanium phosphorus oxide (LATP), garnet-type solid electrolytes may include lithium lanthanum zirconium oxide (LLZO), and perovskite-type solid electrolytes may include lithium lanthanum titanium oxide (LLTO). Sulfide solid electrolytes, such as Li... 10 GeP2S 12 (LGPS), Li3PS4, and polymer solid electrolytes such as polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF).

[0100] In some embodiments of this application, the loading capacity of the positive electrode is 2.5 mAh / cm³. 2 -3.5mAh / cm 2 For example, it could be 2.5mAh / cm³. 2 -3.4mAh / cm 2 2.6mAh / cm 2 -3.3mAh / cm 2 2.7mAh / cm 2 -3.2mAh / cm 2 2.8mAh / cm 2 -3.1mAh / cm 2 2.9mAh / cm 2 -3mAh / cm 2 As can be understood, the charge loading of the positive electrode usually refers to the amount of charge that the electrode can carry per unit area. This can be achieved by adjusting the load of the positive electrode active material in the positive electrode. By controlling the charge loading of the positive electrode within the above range, lithium-ion batteries have better cycle performance and energy density.

[0101] It is understood that "the loading of the positive electrode" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0102] Disassemble the battery, obtain the positive electrode sheet, cut it into circular pieces of a certain area, assemble it with the separator and negative electrode material to form a coin cell, inject liquid electrolyte, charge it, obtain the capacity, and the areal load can be obtained according to the calculation formula: areal load = capacity / (gram capacity × area).

[0103] In some embodiments of this application, the positive electrode sheet can be prepared by the following method: the components used to prepare the positive electrode sheet, such as positive active material, conductive agent, binder, gel, solid electrolyte and any other components, are mixed evenly by shearing, then rolled into a film by a roller press, and then hot-pressed together with the positive current collector to obtain the positive electrode sheet.

[0104] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

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

[0106] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0107] In some embodiments of this application, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, titanates, lithium metal, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. When the battery is a lithium-ion battery, the titanate includes lithium titanate; when the battery is a sodium-ion battery, the titanate includes sodium titanate. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0108] In some embodiments of this application, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0109] In some embodiments of this application, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments of this application, the negative electrode active material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0111] In some embodiments of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0112] In some embodiments of this application, the lithium-ion battery is a lithium metal battery, that is, the negative electrode active material includes lithium metal. In this way, in conjunction with the positive electrode sheet of the embodiments of this application, the cycle performance of the battery can be further improved.

[0113] In some embodiments of this application, the active material layer comprises an alloy formed of an active metal, and the lithium metal battery comprises a lithium metal alloy with the chemical formula LiR, wherein R comprises at least one of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, platinum, boron, carbon, or silicon.

[0114] In some embodiments of this application, when a lithium metal negative electrode sheet is used, the preparation method is as follows: lithium foil or lithium metal alloy is coated onto the current collector by single-sided rolling, and then cut into negative electrode sheets.

[0115] In some embodiments of this application, the electrolyte includes solid electrolytes and electrolyte salts. Generally, the electrolyte plays a role in conducting ions between the positive and negative electrode plates. This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. The electrolyte can be in a gel state (semi-solid) or a solid state.

[0116] In some embodiments of this application, the electrolyte includes a solid electrolyte. In this case, the lithium-ion battery includes a solid battery. Since the contact between the positive electrode active material particles and the solid electrolyte particles inside the positive electrode sheet of the solid battery is a solid-solid rigid contact, the problem of poor contact caused by the volume expansion and contraction of the positive electrode active material is more prominent during battery cycling. This application improves the solid-solid interface contact more significantly by setting a gel in the positive electrode sheet, which can significantly improve the cycle performance of the solid battery.

[0117] The solid electrolyte has been described in detail above and will not be repeated here.

[0118] In some embodiments of this application, when the battery is a lithium-ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

[0119] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0120] In a second aspect, this application proposes a method for preparing a lithium-ion battery, comprising:

[0121] S1: Prepare a positive electrode active material layer to obtain a positive electrode sheet, wherein the positive electrode active material layer includes a gel, the gel includes an electrolyte salt, a solvent and a polymer, wherein the solvent and the electrolyte salt can form a eutectic electrolyte;

[0122] S2: Assemble the positive electrode, electrolyte and negative electrode to obtain a lithium-ion battery.

[0123] In the lithium-ion battery prepared by the method of the embodiments of this application, the eutectic electrolyte formed by the solvent and the electrolyte salt can be used as a wetting agent for the solid-solid interface of the positive electrode active material to reduce the interfacial impedance. The polymer can confine the eutectic electrolyte within the positive electrode sheet to form a gel, which can improve the cycle performance of the lithium-ion battery containing it.

[0124] In some embodiments of this application, the positive electrode sheet is prepared by the following method:

[0125] S11: Mix electrolyte salt, solvent, polymer monomer, crosslinking agent and initiator, and compound them onto at least one side of the positive electrode current collector to obtain a positive electrode precursor;

[0126] S12: The monomers of the polymer are polymerized into a polymer to obtain a positive electrode sheet.

[0127] Specifically, the polymer monomers are first added during the preparation of the positive electrode active material layer, and then polymerized and cross-linked in situ to form a polymer. This facilitates the full entry of the eutectic electrolyte formed by the electrolyte salt and solvent into the polymer interior, where it is bound by the polymer network structure to form a gel. This reduces the occurrence of insufficient entry of the eutectic electrolyte into the polymer interior caused by direct polymer addition. The polymer can better solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity and the risk of it being squeezed out of the positive electrode active material layer due to battery expansion volume changes. This is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge within the positive electrode active material layer, thereby further improving the battery's cycle performance.

[0128] In some embodiments of this application, step S12 includes:

[0129] S121: The positive electrode precursor is heated or irradiated with ultraviolet light to polymerize the monomers of the polymer into a polymer.

[0130] Specifically, using thermally initiated or ultraviolet light-initiated polymerization and cross-linking of polymer monomers facilitates the full penetration of the eutectic electrolyte formed by the electrolyte salt and solvent into the polymer interior. The eutectic electrolyte is then bound by the polymer's network structure, allowing the polymer to better solidify the eutectic electrolyte within the positive electrode active layer. This reduces its fluidity and the risk of it being squeezed out of the positive electrode active material layer due to battery expansion. It also enhances the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge within the positive electrode active material layer, thereby further improving the battery's cycle performance.

[0131] In some embodiments of this application, when heating is used to initiate the monomer polymerization of the polymer, the heating temperature is 50°C-80°C. For example, the heating temperature can be 50°C-79°C, 55°C-75°C, 60°C-70°C, etc. Controlling the heating temperature within the above range is beneficial to controlling the weight-average molecular weight of the obtained polymer, making the monomer polymerization of the polymer into a gel state, solidifying the eutectic electrolyte in the positive electrode active layer, and improving the cycle performance of the lithium-ion battery.

[0132] In some embodiments of this application, the heating time is 8h-15h, for example, the heating time can be 8h-14h, 9h-13h, 10h-12h, etc. Controlling the heating time within the above range is beneficial to control the weight-average molecular weight of the obtained polymer, so that the monomer polymerization of the polymer is in a gel state, and the eutectic electrolyte is solidified in the positive electrode active layer, thereby improving the cycle performance of the lithium-ion battery.

[0133] In some embodiments of this application, when ultraviolet light irradiation is used to initiate the monomer polymerization of the polymer, the irradiation time is 5s-30s, for example, 5s-29s, 10s-25s, 15s-20s, etc. Controlling the irradiation time within the above range is beneficial to controlling the weight-average molecular weight of the obtained polymer, making the monomer polymerization of the polymer into a gel state, solidifying the eutectic electrolyte in the positive electrode active layer, and improving the cycle performance of the lithium-ion battery.

[0134] In some embodiments of this application, the initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, or benzophenone. Specifically, the above-mentioned initiator can effectively initiate the monomer polymerization of the polymer and control the weight-average molecular weight of the obtained polymer, so that the monomer polymerization of the polymer is gel-like, solidifying the eutectic electrolyte in the positive electrode active layer and improving the cycle performance of the lithium-ion battery.

[0135] It is understood that when heating is used to initiate the monomer polymerization of the polymer, the initiator may include at least one of azobisisobutyronitrile and benzoyl peroxide, and when ultraviolet light is used to initiate the monomer polymerization of the polymer, the initiator may include benzophenone.

[0136] In some embodiments of this application, the crosslinking agent includes one or more of ethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, or trimethylolpropane trimethacrylate. These crosslinking agents can promote the crosslinking polymerization of polymer monomers into a network structure, which can better solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity, forming a gel, and reducing the risk of it being squeezed out of the positive electrode active material layer due to battery expansion volume changes. This is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge within the positive electrode active material layer, thereby further improving the battery's cycle performance.

[0137] In some embodiments of this application, the mass ratio of the polymer monomer, the crosslinking agent, and the initiator is (60-70):(39-25):(1-5), for example, it can be 60:39:1, 65:32:3, 70:25:5, etc. By controlling the mass ratio of the three components within the above range, the resulting polymer can solidify the eutectic electrolyte within the positive electrode active layer, thereby reducing its fluidity and forming a gel. This reduces the risk of the eutectic electrolyte being squeezed out of the positive electrode active material layer due to battery expansion and volume changes, which is beneficial to improving the effectiveness of the eutectic electrolyte as a solid-solid interface ion contact bridge inside the positive electrode active material layer, thereby further improving the cycle performance of the battery.

[0138] The secondary batteries of this application include single-cell battery forms, battery module forms, and battery pack forms. The following description, with appropriate reference to the accompanying drawings, will illustrate the single-cell battery, battery module, and battery pack of this application.

[0139] In some embodiments of this application, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0140] In some embodiments of this application, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0141] In some embodiments of this application, the outer packaging of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0142] It is understood that the secondary battery mentioned above in this application is a single battery cell.

[0143] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 1 as an example.

[0144] In some embodiments of this application, referring to FIG2, the outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. The electrolyte is filled in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 1 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0145] In some embodiments of this application, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0146] Figure 3 shows a battery module 2 as an example. Referring to Figure 3, in battery module 2, multiple battery cells 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 1 can be fixed in place using fasteners.

[0147] Optionally, the battery module 2 may also include a housing with a receiving space in which multiple battery cells 1 are received.

[0148] In some embodiments of this application, the battery modules described above can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0149] Figures 4 and 5 show an example battery pack 3. Referring to Figures 4 and 5, the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper box 31 and a lower box 32, with the upper box 31 covering the lower box 32 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0150] In addition, this application also provides an electrical device, which includes the lithium-ion battery provided in the first aspect of this application and the lithium-ion battery prepared using the method described in the second aspect. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0151] As the electrical equipment, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0152] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0153] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0154] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0155] Example 1

[0156] 1. Preparation of positive electrode sheet

[0157] NCM positive electrode active material 811 The conductive agent Super P, binder polytetrafluoroethylene (PTFE), and solid electrolyte (lithium aluminum titanium phosphate LATP) are stirred and mixed evenly. Then, a pre-prepared gel component (lithium salt LiFSI, solvent sulfolane, monomer methyl acrylate, crosslinking agent ethylene glycol dimethacrylate, initiator azobisisobutyronitrile, with a mass ratio of methyl acrylate, crosslinking agent ethylene glycol dimethacrylate, and initiator azobisisobutyronitrile of 70:25:5) is added and mixed evenly. The mixture is then calendered into a film and composited with an Al foil current collector with a thickness of 13 μm to obtain the positive electrode precursor. The obtained positive electrode precursor is heated at 70 °C for 10 h to carry out an in-situ polymerization reaction, resulting in a gelled semi-solid dry electrode, i.e., the positive electrode sheet, with a positive electrode loading of 3 mAh / cm³. 2 .

[0158] In the positive electrode active material layer, the mass percentages of each component are as follows: positive electrode active material 82%, conductive agent 2%, binder 1%, gel 10%, solid electrolyte 5%, and in the gel, the mass ratio of electrolyte salt, solvent and polymer is 50:45:5.

[0159] 2. Preparation of negative electrode sheet

[0160] A lithium metal sheet with a thickness of 50 micrometers was used as the negative electrode.

[0161] 3. Preparation of electrolytes

[0162] PVDF, lithium salt LiTFSI, plasticizer (ionic liquid), and oxide solid electrolyte LLZO were melt-mixed uniformly in an internal mixer at a mass ratio of 4:3:2:1, and a semi-solid electrolyte membrane was prepared by extrusion coating.

[0163] 4. Preparation of lithium-ion batteries

[0164] The above-mentioned positive electrode sheet, polymer electrolyte membrane, and lithium metal are assembled and packaged, and then hot-pressed at 60°C and 2000Pa for 10 minutes to improve the interface contact, thus obtaining a lithium-ion battery.

[0165] Example 2

[0166] It is basically the same as Example 1, except that the positive electrode active material is lithium iron phosphate and the solid electrolyte is polyethylene oxide.

[0167] The preparation methods of the lithium-ion batteries in Examples 3-22 and Comparative Examples 3-9 are the same as those in Example 1, except that the process of preparing the positive electrode sheet is different, as shown in Table 1.

[0168] In Example 7, benzophenone was used as the initiator. After the positive electrode precursor was prepared, it was irradiated with ultraviolet light for 15 seconds to polymerize the polymer monomers. In Examples 12-14, the monomers were replaced with the monomers corresponding to the polymers in each example. The difference between Comparative Example 1 and Example 1 is that no electrolyte salt, solvent, or polymer was added to the positive electrode. The difference between Comparative Example 2 and Example 2 is that no electrolyte salt, solvent, or polymer was added to the positive electrode.

[0169] Table 1

[0170] The cycle performance of the lithium-ion batteries of Examples 1-22 and Comparative Examples 1-9 was characterized, and the characterization results are shown in Table 2.

[0171] Battery cycle count test

[0172] At 60℃, a lithium-ion battery is charged at a constant current and constant voltage of 0.1C to the cutoff voltage, with a cutoff current of 0.05C. After resting for 5 minutes, it is discharged at a constant current of 0.1C to the cutoff voltage. The resulting capacity is recorded as the initial capacity D0. The above steps are repeated for the same battery, and the discharge capacity Dn of the battery after the nth cycle is recorded. The battery capacity retention rate after each cycle is Pn = Dn / D0 × 100%, until the capacity retention rate is less than 80%. The nth cycle is then the battery cycle number.

[0173] If the positive electrode active material is NCM 811 If the positive electrode active material is lithium iron phosphate, the cycle voltage is 4.3V-2.8V; if the positive electrode active material is lithium iron phosphate, the cycle voltage is 3.8V-2.0V.

[0174] Table 2

[0175] As can be seen from Table 2, in Examples 1-22 of this application, the eutectic electrolyte formed by the solvent and the electrolyte salt can be used as a wetting agent for the solid-solid interface of the positive electrode active material to reduce the interfacial impedance. The polymer can confine the eutectic electrolyte within the positive electrode sheet to form a gel, which can improve the cycle performance of the lithium-ion battery containing it.

[0176] Compared with Examples 1-22, Comparative Examples 1-9, Comparative Examples 1 and 2 do not include gel, Comparative Examples 3-4 and 6-9 do not form eutectic electrolyte, Comparative Example 5 lacks polymer and no gel is formed in the positive electrode active material layer, and the cycle performance of the battery is significantly reduced. It can be seen that by setting gel in the positive electrode active material layer and using eutectic electrolyte, the cycle performance of lithium-ion batteries containing it can be improved.

[0177] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium-ion battery, wherein, Includes positive electrode, electrolyte, and negative electrode. The positive electrode sheet includes a positive active material layer, the positive active material layer includes a gel, the gel includes an electrolyte salt, a solvent and a polymer, wherein the solvent and the electrolyte salt can form a eutectic electrolyte.

2. The lithium-ion battery according to claim 1, wherein, The mass ratio of the electrolyte salt to the solvent is (3-7):(3-7).

3. The lithium-ion battery according to claim 1 or 2, wherein, The mass ratio of the electrolyte salt, the solvent, and the polymer is (27-67.9):(27-67.9):(3-10).

4. The lithium-ion battery according to any one of claims 1-3, wherein, The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

5. The lithium-ion battery according to any one of claims 1-4, wherein, One or more of the following conditions must be met: Under standard atmospheric pressure, the melting point of the solvent is 30℃-120℃; Under standard atmospheric pressure, the melting point of the eutectic electrolyte is -30℃ to 20℃; The functional groups of the solvent include one or more of cyano, sulfone, carbonyl, amide, or ether groups.

6. The lithium-ion battery according to any one of claims 1-5, wherein, The solvent includes one or more of sulfolane, dibutyl sulfone, dimethyl sulfone, diethyl sulfone, methyl sulfone, succinic acid, ethylene glycol dimethyl ether oligomer, acetamide, trifluoromethanesulfonamide, or ethylene carbonate.

7. The lithium-ion battery according to any one of claims 1-6, wherein, The weight-average molecular weight of the polymer is 5000-15000.

8. The lithium-ion battery according to any one of claims 1-7, wherein, The polymer includes one or more of acrylate polymers or polyolefins.

9. The lithium-ion battery according to claim 8, wherein, One or more of the following conditions must be met: The acrylate polymers include one or more of polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate or polybutyl methacrylate; The polyolefin includes one or more of polyethylene, polypropylene, polybutene, or polystyrene.

10. The lithium-ion battery according to any one of claims 1-9, wherein, The positive electrode active material layer also includes a positive electrode active material, a conductive agent, and a binder.

11. The lithium-ion battery according to claim 10, wherein, Based on the total mass of the positive electrode active material layer, the mass percentage of each component is as follows: Positive electrode active material 70%-90%, conductive agent 1.5%-3%, binder 1%-2%, gel 5%-20%.

12. The lithium-ion battery according to claim 10 or 11, wherein, The positive electrode active material includes one or more of lithium phosphates or lithium transition metal oxides with an olivine structure.

13. The lithium-ion battery according to any one of claims 10-12, wherein, One or more of the following conditions must be met: The conductive agent includes one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers. The adhesive includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

14. The lithium-ion battery according to any one of claims 1-13, wherein, The positive electrode active material layer also includes a solid electrolyte.

15. The lithium-ion battery according to claim 14, wherein, Based on the total mass of the positive electrode active material layer, the mass percentage of the solid electrolyte is less than or equal to 10%.

16. The lithium-ion battery according to any one of claims 1-15, wherein, The positive electrode has a loading capacity of 2.5 mAh / cm³. 2 -3.5mAh / cm 2 .

17. The lithium-ion battery according to any one of claims 1-16, wherein, The electrolyte includes a solid electrolyte.

18. The lithium-ion battery according to any one of claims 1-17, wherein, The negative electrode sheet includes one or more of the following: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, or lithium metal.

19. The lithium-ion battery according to claim 18, wherein, The negative electrode sheet comprises lithium metal.

20. A method for preparing a lithium-ion battery, wherein, include: A positive electrode active material layer is prepared to obtain a positive electrode sheet, wherein the positive electrode active material layer includes a gel, the gel includes an electrolyte salt, a solvent and a polymer, wherein the solvent and the electrolyte salt can form a eutectic electrolyte; The positive electrode, electrolyte, and negative electrode are assembled to obtain a lithium-ion battery.

21. The method according to claim 20, wherein, The positive electrode sheet is prepared by the following method: An electrolyte salt, solvent, polymer monomer, crosslinking agent and initiator are mixed and compounded onto at least one side of the positive electrode current collector to obtain a positive electrode precursor. The monomers of the polymer are polymerized into a polymer to obtain a positive electrode sheet.

22. The method according to claim 21, wherein, The polymerization of the monomers of the polymer into a polymer includes: The positive electrode precursor is heated or irradiated with ultraviolet light to polymerize the monomers of the polymer into a polymer.

23. The method according to claim 22, wherein, One or more of the following conditions must be met: The heating temperature is 50℃-80℃; The heating time is 8-15 hours; The duration of ultraviolet light irradiation is 5s-30s.

24. The method according to any one of claims 21-23, wherein, One or more of the following conditions must be met: The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, or benzophenone; The crosslinking agent includes one or more of ethylene glycol dimethacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, or trimethylolpropane trimethacrylate; The mass ratio of the monomer of the polymer, the crosslinking agent and the initiator is (60-70):(39-25):(1-5).

25. An electrical appliance, wherein, The lithium-ion battery includes any one of claims 1-19, or a lithium-ion battery prepared by any one of claims 20-24.

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