Battery cell and preparation method therefor, battery and electric device

Abstract

The present application discloses a battery cell and a preparation method therefor, a battery, and an electric device. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte. The electrolyte comprises a first non-aqueous electrolyte solution close to the positive electrode sheet and a second gel electrolyte close to the negative electrode sheet. The first non-aqueous electrolyte solution comprises a first solvent and a first lithium salt, and the first solvent comprises a nitrile-based solvent. The second gel electrolyte comprises a polymer layer and a second non-aqueous electrolyte solution accommodated in the polymer layer. The second non-aqueous electrolyte solution comprises a second solvent and a second lithium salt, and the second solvent comprises a linear monoether solvent. The battery cell has long cycle life and good rate performance.

Description

Battery cell, preparation method thereof, battery and electric device

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410850368.0, filed on June 27, 2024, entitled “Battery cell, preparation method thereof, battery and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to a battery cell, a preparation method thereof, a battery and an electric device. BACKGROUND

[0004] The cycle life of a battery cell is crucial to its performance. Currently, the electrolyte of a battery cell usually adopts a carbonate-based electrolyte, and the carbonate-based electrolyte has a limited ionic conductivity during the long cycle of the battery cell. The nitrile-based electrolyte has a much higher ionic conductivity than the commercially available carbonate-based electrolyte, which is expected to greatly improve the performance of the battery cell. However, due to the problems of high intrinsic reduction reactivity and easy co-intercalation of nitrile-based molecules, the nitrile-based electrolyte is difficult to be compatible with the current anodes such as graphite, silicon-based materials, lithium metal, etc., thereby limiting the practical application of the nitrile-based electrolyte and failing to fully exert its high ionic conductivity advantage.

[0005] SUMMARY

[0006] The present application provides a battery cell, a preparation method thereof, a battery and an electric device, which can make the battery cell have a long cycle life and good rate performance.

[0007] In a first aspect, the present application provides a battery cell, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, the electrolyte comprising a first non-aqueous electrolyte close to the positive electrode sheet and a second gel electrolyte close to the negative electrode sheet; the first non-aqueous electrolyte comprises a first solvent and a first lithium salt, the first solvent comprising a nitrile-based solvent; the second gel electrolyte comprises a polymer layer and a second non-aqueous electrolyte contained in the polymer layer, the second non-aqueous electrolyte comprising a second solvent and a second lithium salt, the second solvent comprising a chain single ether solvent.

[0008] The first solvent includes a nitrile solvent, so that the first non-aqueous electrolyte has the characteristics of high ionic conductivity, thereby facilitating the efficient conduction of lithium ions and improving the rate performance and cycle life of the battery cell. The nitrile molecule has strong oxidation stability, and setting near the positive electrode can improve the stability of the positive electrode interface, that is, the first non-aqueous electrolyte and the positive electrode are better compatible. The second solvent includes a chain single ether solvent, and the chain single ether molecule has strong reduction stability, and setting near the negative electrode can improve the stability of the negative electrode interface, that is, the second gel electrolyte and the negative electrode are better compatible. Therefore, by setting the first non-aqueous electrolyte near the positive electrode plate and the second gel electrolyte near the negative electrode plate, the actual electrochemical window of the electrolyte can be widened, and the battery cell can have good positive and negative electrode stability. In addition, by setting the first non-aqueous electrolyte near the positive electrode plate and the second gel electrolyte near the negative electrode plate, the reduction decomposition side reaction of the nitrile molecule at the negative electrode side can be effectively reduced, and the oxidation decomposition side reaction of the chain single ether molecule at the positive electrode side can be effectively reduced.

[0009] The second non-aqueous electrolyte is contained in the polymer layer, so that the flow of the second non-aqueous electrolyte can be limited, and a gel electrolyte can be formed, thereby further separating the nitrile molecule from the negative electrode and effectively reducing the reduction decomposition side reaction of the nitrile molecule.

[0010] Therefore, the battery cell provided by the embodiments of the present application not only retains the advantages of high ionic conductivity and good oxidation stability of the nitrile electrolyte, but also makes the nitrile electrolyte compatible with the negative electrode, so that the battery cell can have long cycle life and good rate performance.

[0011] In some embodiments, the polymer layer includes one or more of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyimide, polyethersulfone, polyvinyl acetate, polymethyl methacrylate, polyethylene glycol, polyvinyl chloride, a copolymer of at least two of the foregoing polymers.

[0012] The material of the polymer layer is within the above range, which can not only contain the second non-aqueous electrolyte and limit the flow of the second non-aqueous electrolyte, but also make the formed second gel electrolyte have good ion conduction capacity.

[0013] In some embodiments, the thickness of the polymer layer is 1-20 μm.

[0014] The thickness of the polymer layer is within the above range, which can make the second gel electrolyte have high ionic conductivity, facilitate the improvement of the migration rate of lithium ions and the reduction of polarization, and thereby facilitate the improvement of the cycle performance and rate performance of the battery cell.

[0015] In some embodiments, the amount of the second non-aqueous electrolyte in the polymer layer is 2.0 μL / cm2 - 10.0 µL / cm 2 .

[0016] The amount of the second non-aqueous electrolyte is within the above range, which can make the second gel electrolyte have high ionic conductivity, be beneficial to improving the migration rate of lithium ions and reducing polarization, and thus be beneficial to improving the cycle performance and rate performance of the battery cell.

[0017] In some embodiments, the nitrile-based solvent includes one or more of C2 to C10 alkyl nitrile, C3 to C10 alkenyl nitrile, C3 to C10 alkynyl nitrile, C2 to C10 haloalkyl nitrile, C3 to C10 haloalkenyl nitrile, C3 to C10 haloalkynyl nitrile, C7 to C10 aryl nitrile, C3 to C10 epoxy nitrile. Optionally, the nitrile-based solvent includes one or more of acetonitrile, propionitrile, butyronitrile, malononitrile, succinonitrile, glutaronitrile, 2-methylene glutaronitrile, adiponitrile.

[0018] The nitrile-based solvent is within the above range, which can have strong molecular polarity and high dielectric constant, and also have good oxidation resistance, and thus can be used on the positive side of the battery cell to improve the positive interfacial stability of the battery cell.

[0019] In some embodiments, the chain single ether solvent includes C2 to C10 chain single ether solvent. Optionally, the chain single ether solvent includes one or more of diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, methyl propyl ether, methyl n-butyl ether, methyl t-butyl ether.

[0020] The chain single ether solvent is within the above range, which can have weak molecular polarity, low dielectric constant, and good reduction resistance, and thus can be used on the negative side of the battery cell, which can not only separate the nitrile molecules from the negative electrode to reduce the reduction decomposition side reaction of the nitrile molecules, but also improve the negative interfacial stability of the battery cell.

[0021] In some embodiments, the first lithium salt includes one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, lithium bisfluoroxalate borate.

[0022] The first lithium salt is within the above range, which can make the first non-aqueous electrolyte have strong dissociation ability and good electrochemical stability.

[0023] In some embodiments, the second lithium salt includes one or more of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, lithium bisfluoroxalate borate.

[0024] The second lithium salt is within the above range, which can make the second gel electrolyte have high ionic conductivity and good electrochemical stability.

[0025] In some embodiments, the lithium salt concentration of the first non-aqueous electrolyte is 0.5 mol / L-5 mol / L.

[0026] The lithium salt concentration of the first non-aqueous electrolyte in the above range can make the first non-aqueous electrolyte have high ionic conductivity, thereby being conducive to the wettability of the first non-aqueous electrolyte to the positive electrode sheet, the migration rate of lithium ions and the reduction of polarization, and thus being conducive to the improvement of the cycle performance and rate performance of the battery cell.

[0027] In some embodiments, the lithium salt concentration of the second non-aqueous electrolyte is 1 mol / L-3 mol / L.

[0028] The lithium salt concentration of the second non-aqueous electrolyte in the above range can make the second gel electrolyte have high ionic conductivity, thereby being conducive to the improvement of the migration rate of lithium ions and the reduction of polarization, and thus being conducive to the improvement of the cycle performance and rate performance of the battery cell.

[0029] In some embodiments, the first non-aqueous electrolyte further comprises a first additive, and the first additive comprises one or more of butylsulfolactone, propenyl-1,3-sulfolactone, trifluoromethyl ethyl sulfone, pentafluorophenoxy cyclotriphosphazene, triethyl phosphate, tris(trimethylsilyl) phosphate, triethyl borate, tris(trimethylsilyl) borate, fluoroethylene carbonate, lithium difluorophosphate, lithium bisfluorodi oxalate phosphate, lithium nitrate.

[0030] The first additive in the above range can further improve the interface stability of the first non-aqueous electrolyte to the positive electrode, thereby being conducive to the further improvement of the cycle performance and rate performance of the battery cell.

[0031] In some embodiments, the mass of the first additive is 0.5%-10% of the total mass of the first non-aqueous electrolyte.

[0032] The mass fraction of the first additive in the above range is conducive to the further improvement of the cycle performance and rate performance of the battery cell.

[0033] In some embodiments, the second non-aqueous electrolyte further comprises a second additive, and the second additive comprises one or more of 1,3-propane sultone, ethylene sulfate, 1,3-dioxolane, lithium nitrate, tetraethylammonium nitrate, tetrabutylammonium nitrate.

[0034] The second additive in the above range can further improve the interface stability of the second gel electrolyte to the negative electrode, thereby being conducive to the further improvement of the cycle performance and rate performance of the battery cell.

[0035] In some embodiments, the mass of the second additive is 0.5%-10% of the total mass of the second non-aqueous electrolyte.

[0036] The mass fraction of the second additive is in the above range, which is beneficial to further improve the cycle performance and rate performance of the battery cell.

[0037] In some embodiments, the positive electrode plate comprises one or more of lithium-containing phosphates, lithium transition metal oxides.

[0038] In some embodiments, the negative electrode plate comprises one or more of lithium titanate, carbon-based materials, silicon-based materials, tin-based materials, lithium metal.

[0039] In a second aspect, the present application provides a preparation method of a battery cell, comprising the following steps: providing a positive electrode plate, a separator, a negative electrode plate, a first non-aqueous electrolyte and a second non-aqueous electrolyte, the first non-aqueous electrolyte comprising a first solvent and a first lithium salt, the first solvent comprising a nitrile solvent, the second non-aqueous electrolyte comprising a second solvent and a second lithium salt, the second solvent comprising a chain mono-ether solvent; disposing a polymer layer on the outermost side of the negative electrode plate, and then impregnating the polymer layer with the second non-aqueous electrolyte to obtain a negative electrode plate formed with a second gel electrolyte; assembling the positive electrode plate, the separator and the negative electrode plate formed with the second gel electrolyte to obtain a to-be-liquid-injected battery cell, and injecting the first non-aqueous electrolyte into the to-be-liquid-injected battery cell to obtain a battery cell.

[0040] In a third aspect, the present application provides a battery comprising the battery cell of the first aspect of the present application or prepared by the preparation method of the second aspect of the present application.

[0041] In a fourth aspect, the present application provides an electric device comprising the battery of the third aspect of the present application.

[0042] The electric device of the present application comprises the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained according to the drawings without paying creative labor for those skilled in the art.

[0044] FIG. 1 is a schematic diagram of an embodiment of the battery cell of the present application.

[0045] FIG. 2 is a schematic diagram of an embodiment of the battery module of the present application.

[0046] FIG. 3 is a schematic diagram of an embodiment of the battery pack of the present application.

[0047] FIG. 4 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 3.

[0048] FIG. 5 is a schematic view of an embodiment of an electrical device including the battery of the present application as a power source.

[0049] In the drawings, the drawings are not necessarily drawn to scale.

[0050] Reference signs are explained as follows: 1, battery pack; 2, upper case; 3, lower case; 4, battery module; 5, battery cell. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the battery cell and the method for manufacturing the same, the battery, and the electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed explanations are omitted. For example, there can be cases where detailed explanations of matters that are well known, repeated explanations of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following explanations are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0052] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0054] If not particularly specified, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions shall be considered to be included in the disclosure of the present application.

[0055] If not particularly specified, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method also comprises step (c) as mentioned, which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0056] Unless otherwise specified, the terms used in the present application have the commonly understood meanings understood by those skilled in the art.

[0057] Unless otherwise specified, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, the test methods given in the examples of the present application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0058] The battery mentioned in the examples of the present application can comprise one or more battery cells to provide a single physical module with higher voltage and capacity. For example, the battery mentioned in the present application can comprise a battery cell, a battery module or a battery pack, etc.

[0059] The battery cell is the smallest unit that constitutes the battery, which can realize the function of charging and discharging by itself. The battery cell can be in the shape of a cylinder, a cuboid or other shapes, which are not limited in the examples of the present application. For example, FIG. 1 is a battery cell 5 in the shape of a cuboid as an example.

[0060] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in a mixed manner through a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which comprises a box body and battery cells, and the battery cells or the battery module are contained in the box body. In some embodiments, the box body can be part of the chassis structure of the vehicle. For example, part of the box body can be at least part of the floor of the vehicle, or part of the box body can be at least part of the cross beam and the longitudinal beam of the vehicle.

[0061] In some embodiments, the battery can be an energy storage device. The energy storage device comprises an energy storage container, an energy storage cabinet, etc.

[0062] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. FIG. 2 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 2, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be made. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0063] Optionally, the battery module 4 can also include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0064] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0065] FIGS. 3 and 4 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 3 and 4, the battery pack 1 can include a box body and a plurality of battery modules 4 arranged in the box body. The box body includes an upper box body 2 and a lower box body 3, the upper box body 2 is used to cover the lower box body 3, and forms a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the box body in any manner.

[0066] Embodiments of the present application provide a battery cell, which can be a lithium ion battery cell, a lithium metal battery cell, a negative electrode-free lithium metal battery cell, etc. A negative electrode-free lithium metal battery cell generally refers to a battery cell that is configured without a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery cell. For example, the negative electrode active material layer is not formed by applying or depositing a carbon-based active material layer on the negative electrode during the manufacturing process of the battery cell. During the first charging, ions obtain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal phase. During discharging, the metal can be converted into metal ions to return to the positive electrode, thereby realizing cyclic charging and discharging. Compared with other battery cells, the negative electrode-free lithium metal battery cell does not have a negative electrode active material layer, thereby achieving a higher energy density. In some embodiments, in order to improve the performance of the battery cell, some substances that can be used as negative electrode active materials, such as carbon materials, etc., can also be arranged on the negative electrode side of the negative electrode-free lithium metal battery cell. Although these substances have a certain capacity, due to their small amount and not being used as the main negative electrode active material in the battery cell, the battery cell thus configured can still be regarded as a negative electrode-free lithium metal battery cell. The CB value of the negative electrode-free lithium metal battery cell is generally very small, for example, in some embodiments, the CB value of the negative electrode-free lithium metal battery cell can be less than or equal to 0.1. The CB value is the capacity per unit area of the negative electrode divided by the capacity per unit area of the positive electrode in the battery cell. Since the negative electrode-free lithium metal battery cell does not contain or contains only a small amount of negative electrode active material, the capacity per unit area of the negative electrode is small, and thus the CB value is very small, for example, generally less than or equal to 0.1.

[0067] The battery cell provided by the embodiments of the present application comprises an electrode assembly and an electrolyte. The electrode assembly comprises a positive electrode sheet, a separator film, and a negative electrode sheet. The electrode assembly can be in a roll structure or a stack structure, which is not limited in the embodiments of the present application. The battery cell can further comprise an outer package, which can be used to encapsulate the electrode assembly and the electrolyte. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of aluminum plastic film, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0068] The electrolyte comprises a first non-aqueous electrolyte close to the positive electrode sheet and a second gel electrolyte close to the negative electrode sheet. The first non-aqueous electrolyte comprises a first solvent and a first lithium salt, and the first solvent comprises a nitrile-based solvent. The second gel electrolyte comprises a polymer layer and a second non-aqueous electrolyte contained in the polymer layer, and the second non-aqueous electrolyte comprises a second solvent and a second lithium salt, and the second solvent comprises a chain single ether solvent.

[0069] The first solvent includes a nitrile solvent, so that the first non-aqueous electrolyte has the characteristics of high ionic conductivity, thereby facilitating the efficient conduction of lithium ions, and facilitating the improvement of the rate performance and cycle life of the battery cell. The nitrile molecule has strong oxidation stability, and is arranged close to the positive electrode, so that the positive electrode interface stability can be improved, that is, the first non-aqueous electrolyte and the positive electrode are better compatible. The second solvent includes a chain single ether solvent, and the chain single ether molecule has strong reduction stability, and is arranged close to the negative electrode, so that the negative electrode interface stability can be improved, that is, the second gel electrolyte and the negative electrode are better compatible. Therefore, the first non-aqueous electrolyte is arranged close to the positive electrode plate, and the second gel electrolyte is arranged close to the negative electrode plate, so that the actual electrochemical window of the electrolyte can be widened, and the battery cell can have good positive and negative electrode stability. In addition, the first non-aqueous electrolyte is arranged close to the positive electrode plate, and the second gel electrolyte is arranged close to the negative electrode plate, which can effectively reduce the reduction decomposition side reaction of the nitrile molecule on the negative electrode side, and effectively reduce the oxidation decomposition side reaction of the chain single ether molecule on the positive electrode side.

[0070] The second non-aqueous electrolyte is contained in the polymer layer, so that the flow of the second non-aqueous electrolyte can be limited, and a gel electrolyte can be formed, thereby further separating the nitrile molecule from the negative electrode and effectively reducing the reduction decomposition side reaction of the nitrile molecule.

[0071] Therefore, the battery cell provided by the embodiments of the present application not only retains the advantages of high ionic conductivity and good oxidation stability of the nitrile electrolyte, but also makes the nitrile electrolyte compatible with the negative electrode, so that the battery cell can have long cycle life and good rate performance.

[0072] In some embodiments, the first non-aqueous electrolyte and the second non-aqueous electrolyte are separated.

[0073] The nitrile solvent refers to an organic solvent containing at least one nitrile group.

[0074] In some embodiments, the nitrile solvent can include one or more of C2 to C10 alkyl nitrile, C3 to C10 alkenyl nitrile, C3 to C10 alkynyl nitrile, C2 to C10 halogenated alkyl nitrile, C3 to C10 halogenated alkenyl nitrile, C3 to C10 halogenated alkynyl nitrile, C7 to C10 aryl nitrile, and C3 to C10 epoxy nitrile.

[0075] In some embodiments, the nitrile solvent can include one or more of acetonitrile, propionitrile, butyronitrile, malononitrile, succinonitrile, glutaronitrile, 2-methylene glutaronitrile, and adiponitrile.

[0076] The nitrile solvent in the above range can have strong molecular polarity and high dielectric constant, and also has good oxidation resistance, and is used on the positive side of the battery cell, so that the positive electrode interface stability of the battery cell can be improved.

[0077] Optionally, the nitrile solvent can include one or more of acetonitrile, malononitrile, succinonitrile, glutaronitrile, 2-methylene glutaronitrile, adiponitrile.

[0078] The nitrile solvent in the above range is also easy to cause phase separation of the first non-aqueous electrolyte and the second non-aqueous electrolyte.

[0079] In some embodiments, the relative dielectric constant of the nitrile solvent can be above 20, optionally above 24, above 28, above 32, above 35. The test temperature is 20-25°C.

[0080] The relative dielectric constant of the solvent has the meaning known in the art and can be tested by instruments and methods known in the art.

[0081] In some embodiments, the first lithium salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethyl)sulfonylimide (LiTFSI), lithium bisfluorooxalate borate (LiDFOB).

[0082] The first lithium salt in the above range can make the first non-aqueous electrolyte have strong dissociation ability and good electrochemical stability.

[0083] In some embodiments, the lithium salt concentration of the first non-aqueous electrolyte can be 0.5-5 mol / L, for example, can be 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, or a range consisting of any of the above values.

[0084] The lithium salt concentration of the first non-aqueous electrolyte in the above range can make the first non-aqueous electrolyte have high ionic conductivity, thereby being conducive to the first non-aqueous electrolyte wetting the positive electrode sheet, and being conducive to improving the migration rate of lithium ions and reducing polarization, thereby being conducive to improving the cycle performance and rate performance of the battery cell.

[0085] Optionally, the lithium salt concentration of the first non-aqueous electrolyte can be 0.8-3 mol / L, 0.8-2 mol / L, 0.8-1.5 mol / L.

[0086] In some embodiments, the first non-aqueous electrolyte can further include a first additive, which can include one or more of butyl sulfone (BS), propylene-1,3-sultone (PES), trifluoromethyl ethyl sulfone (FMES), pentafluorophenoxy cyclotriphosphazene (PFPN), triethyl phosphate (TEP), tris(trimethylsilyl) phosphate (TMSP), triethyl borate (TEB), tris(trimethylsilyl) borate (TMSB), fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFBP), lithium nitrate (LiNO3).

[0087] The first additive can be within the above range, which can further improve the interface stability of the first non-aqueous electrolyte to the positive electrode, and be conducive to further improving the cycle performance and rate performance of the battery cell.

[0088] In some embodiments, the mass of the first additive can be 0.5%-10% of the total mass of the first non-aqueous electrolyte, for example, can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any of the foregoing values.

[0089] The mass fraction of the first additive can be within the above range, which is conducive to further improving the cycle performance and rate performance of the battery cell.

[0090] Alternatively, the mass of the first additive can be 1%-8% of the total mass of the first non-aqueous electrolyte.

[0091] In some embodiments, the polymer layer can include one or more of polyethylene oxide, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyacrylonitrile, polyimide, polyether sulfone, polyvinyl acetate, polymethyl methacrylate, polyethylene glycol, polyvinyl chloride, a copolymer of at least two of the foregoing polymers.

[0092] The material of the polymer layer can be within the above range, which can not only accommodate the second non-aqueous electrolyte and limit the flow of the second non-aqueous electrolyte, but also enable the formed second gel electrolyte to have good ion conduction capability.

[0093] Alternatively, the polymer layer can include one or more of polyethylene oxide, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyacrylonitrile, and polymethyl methacrylate.

[0094] More alternatively, the polymer layer can include polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).

[0095] In some embodiments, the thickness of the polymer layer can be 1-20 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a range consisting of any of the aforementioned values.

[0096] The thickness of the polymer layer in the above range can make the second gel electrolyte have high ionic conductivity, which is conducive to improving the migration rate of lithium ions and reducing polarization, thereby being conducive to improving the cycle performance and rate performance of the battery cell.

[0097] Optionally, the thickness of the polymer layer can be 1-10 μm, 1-8 μm, 2-10 μm, 2-8 μm.

[0098] In some embodiments, the amount of the second non-aqueous electrolyte in the polymer layer can be 2.0-10.0 μL / cm 2 , for example, 2.0 μL / cm 2 , 2.2 μL / cm 2 , 2.4 μL / cm 2 , 2.6 μL / cm 2 , 2.8 μL / cm 2 , 3.0 μL / cm 2 , 3.2 μL / cm 2 , 3.4 μL / cm 2 , 3.6 μL / cm 2 , 3.8 μL / cm 2 , 4.0 μL / cm 2 , 4.2 μL / cm 2 , 4.4 μL / cm 2 , 4.6 μL / cm 2 , 4.8 μL / cm 2 , 5.0 μL / cm 2 , 5.2 μL / cm 2 , 5.4 μL / cm 2 , 5.6 μL / cm 2 , 5.8 μL / cm 2 , 6.0 μL / cm 2 , 6.2 μL / cm 2 , 6.4 μL / cm 2 , 6.6 μL / cm 2 , 6.8 μL / cm 2 , 7.0 μL / cm 2 , 7.2 μL / cm 27.2 μL / cm 2 7.4 μL / cm 2 7.6 μL / cm 2 7.8 μL / cm 2 8.0 μL / cm 2 8.2 μL / cm 2 8.4 μL / cm 2 8.6 μL / cm 2 8.8 μL / cm 2 9.0 μL / cm 2 9.2 μL / cm 2 9.4 μL / cm 2 9.6 μL / cm 2 9.8 μL / cm 2 10.0 μL / cm 2 , or a range composed of any of the above values.

[0099] The amount of the second non-aqueous electrolyte in the polymer layer refers to the amount of the second non-aqueous electrolyte corresponding to the polymer layer per 1 cm 2 area on average.

[0100] The amount of the second non-aqueous electrolyte is within the above range, which can make the second gel electrolyte have high ion conductivity, be conducive to improving the migration rate of lithium ions and reducing polarization, and thus be conducive to improving the cycle performance and rate performance of the battery cell.

[0101] The battery cell provided by the embodiments of the present application can include a lithium ion battery cell, a lithium metal battery cell, a negative electrode-free lithium metal battery cell, etc. The amount of the second non-aqueous electrolyte in the polymer layer will be different for different specific types of battery cells. For a lithium ion battery cell, the amount of the second non-aqueous electrolyte in the polymer layer can be 6.0 μL / cm 2 -10.0 μL / cm 2 , and can be 8.0 μL / cm 2 -10.0 μL / cm 2 . For a lithium metal battery cell or a negative electrode-free lithium metal battery cell, the amount of the second non-aqueous electrolyte in the polymer layer can be 2.0 μL / cm 2 -6.0 μL / cm 2 , and can be 3.0 μL / cm 2 -5.0 μL / cm 2 .

[0102] The chain single ether solvent refers to a chain ether solvent containing only one ether oxygen functional group in the molecular structure.

[0103] In some embodiments, the chain-like mono-ether solvent can include C2 to C10 chain-like mono-ether solvents. For example, the C2 to C10 chain-like mono-ether solvent can include one or more of C2 chain-like mono-ether solvent, C3 chain-like mono-ether solvent, C4 chain-like mono-ether solvent, C5 chain-like mono-ether solvent, C6 chain-like mono-ether solvent, C7 chain-like mono-ether solvent, C8 chain-like mono-ether solvent, C9 chain-like mono-ether solvent, and C10 chain-like mono-ether solvent. The chain-like mono-ether solvent can be a branched structure or a branched structure.

[0104] Optionally, the chain-like mono-ether solvent can include one or more of diethyl ether (DEE), dipropyl ether (DPE), dibutyl ether (DBE), dipentyl ether (DPeE), methyl propyl ether (MPE), methyl n-butyl ether (MBE), and methyl tert-butyl ether (MTBE).

[0105] The chain-like mono-ether solvent in the above range can have weak molecular polarity, low dielectric constant, and good resistance to reduction, and can be used on the negative side of the battery monomer, which can not only separate the nitrile molecules from the negative electrode and reduce the reduction decomposition side reaction of the nitrile molecules, but also can improve the stability of the negative electrode interface of the battery monomer.

[0106] Optionally, the chain-like mono-ether solvent can include one or more of diethyl ether (DEE), dipropyl ether (DPE), dibutyl ether (DBE), dipentyl ether (DPeE), methyl propyl ether (MPE), methyl n-butyl ether (MBE), and methyl tert-butyl ether (MTBE).

[0107] More optionally, the chain-like mono-ether solvent can include dibutyl ether (DBE).

[0108] In some embodiments, the relative dielectric constant of the chain-like mono-ether solvent can be 2-6, and optionally 2.5-5. The test temperature is 20-25°C.

[0109] In some embodiments, the second lithium salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis(trifluoromethyl) sulfonylimide (LiTFSI), and lithium bisfluorosulfoxyl borate (LiDFOB).

[0110] The second lithium salt in the above range can make the second gel electrolyte have high ionic conductivity and good electrochemical stability.

[0111] In some embodiments, the lithium salt concentration of the second non-aqueous electrolyte can be 1 mol / L-3 mol / L, for example, can be 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L, 3 mol / L, or a range consisting of any of the above values.

[0112] The lithium salt concentration of the second non-aqueous electrolyte in the above range can make the second gel electrolyte have high ion conductivity, which is conducive to improving the migration rate of lithium ions and reducing polarization, thereby being conducive to improving the cycle performance and rate performance of the battery cell.

[0113] Alternatively, the lithium salt concentration of the second non-aqueous electrolyte can be 1.5 mol / L-2.5 mol / L.

[0114] In some embodiments, the second non-aqueous electrolyte can further include a second additive, and the second additive can include one or more of 1,3-propanesultone (1,3-PS), vinyl sulfate (DTD), 1,3-dioxolane (DOL), lithium nitrate (LiNO3), tetraethylammonium nitrate (TEANO3), and tetrabutylammonium nitrate (TBANO3).

[0115] The second additive in the above range can further improve the interface stability of the second gel electrolyte to the negative electrode, which is conducive to further improving the cycle performance and rate performance of the battery cell.

[0116] In some embodiments, the mass of the second additive can be 0.5%-10% of the total mass of the second non-aqueous electrolyte, for example, can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any of the above values.

[0117] The mass fraction of the second additive in the above range is conducive to further improving the cycle performance and rate performance of the battery cell.

[0118] Alternatively, the mass of the second additive can be 1%-8% of the total mass of the second non-aqueous electrolyte.

[0119] [Positive electrode sheet]

[0120] In some embodiments, the positive electrode tab can include a positive current collector and a positive film layer disposed on at least one surface of the positive current collector, the positive film layer including a positive active material. For example, the positive current collector has two surfaces opposite in the thickness direction of the positive current collector, and the positive film layer is disposed on either one or both of the two opposite surfaces of the positive current collector.

[0121] The positive active material includes a material capable of deintercalating and intercalating lithium, and optionally, the positive active material can include, but is not limited to, one or more of lithium-containing phosphates, lithium transition metal oxides. Examples of the lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and respective modified compounds thereof. Examples of the lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel 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 respective modified compounds thereof.

[0122] In some embodiments, as an example, the positive active material can include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, and respective modified compounds thereof.

[0123] The modification compound of each of the above positive electrode active materials can be a doping modification and / or a surface coating modification of the positive electrode active material.

[0124] The battery cell will be accompanied by Li deintercalation and consumption during charging and discharging, and the molar content of Li element is different when the battery cell is discharged to different states. In the above enumeration of specific substances of positive electrode active materials, the molar content of Li element is the initial state, i.e. the state before feeding, and the positive electrode active material is applied to the battery cell. After charging and discharging cycle, the molar content of Li element may change. Similarly, in the above enumeration of specific substances of positive electrode active materials, the molar content of O element is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of O element to change, and the molar content of O element may fluctuate.

[0125] In some embodiments, the positive electrode film layer can further include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include, but is not limited to, one or more of super-p carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode film layer can further include a positive electrode binder. As an example, the positive electrode binder can include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylic ester resin.

[0127] In some embodiments, the positive electrode current collector can adopt a metal foil or a composite current collector. As an example of the metal foil, an aluminum foil can be adopted. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0128] The positive electrode film layer can be formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing and uniformly stirring the positive electrode active material, the positive electrode conductive agent, the positive electrode binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0129] [Negative electrode sheet]

[0130] Embodiments of the present application provide a battery cell, which can include a lithium ion battery cell, a lithium metal battery cell, a negative electrode-free lithium metal battery cell, etc. The specific type of battery cell can be different, and the structure and composition of the negative electrode sheet can be different.

[0131] In some embodiments, the negative electrode sheet can include a negative electrode current collector and a negative electrode film layer on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material, which can include one or more of lithium titanate, a carbon-based material, a silicon-based material, a tin-based material, and lithium metal.

[0132] Optionally, the carbon-based material can include, but is not limited to, one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and mesocarbon microbeads. Optionally, the silicon-based material can include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. Optionally, the tin-based material can include, but is not limited to, one or more of elemental tin, tin oxide, and tin alloy material.

[0133] In some embodiments, the negative electrode film layer can further include a negative electrode conductive agent. As an example, the negative electrode conductive agent can include, but is not limited to, one or more of super-conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0134] In some embodiments, the negative electrode film layer can further include a negative electrode binder. As an example, the negative electrode binder can include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0135] In some embodiments, the negative electrode film layer can further include other auxiliary agents, which can include, as an example, a thickening agent, such as carboxymethyl cellulose sodium (CMC), PTC thermistor material, etc.

[0136] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, a copper foil, a copper alloy foil, a nickel foil, or a nickel alloy foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0137] In some embodiments, the negative electrode tab can include a negative current collector and a lithium metal layer disposed on at least one surface of the negative current collector.

[0138] Since the theoretical gravimetric capacity of lithium metal is relatively high, and has a relatively low density and a relatively negative electrode potential, using lithium metal as the negative active material can significantly improve the energy density of the battery cell. In this case, the battery cell can be referred to as a lithium metal battery cell.

[0139] In some embodiments, the negative electrode tab can include a negative current collector and a lithium metal layer disposed on at least one surface of the negative current collector.

[0140] The second gel electrolyte contains a chain-like monoether solvent, which has high compatibility with the lithium metal negative electrode and can regulate the uniform deposition of lithium metal; the chain-like monoether molecule also has strong reduction stability, which can improve the lithium deposition and stripping efficiency, thereby enabling the lithium metal battery cell and the negative electrode-free lithium metal battery cell to have high energy density, long cycle life and good rate performance.

[0141] [Separator]

[0142] The separator is disposed between the positive electrode tab and the negative electrode tab, and mainly functions to prevent internal short circuit. The type of the separator is not particularly limited in the present application, and any known porous structure film having good chemical stability and mechanical stability can be selected. In some embodiments, the material of the separator can include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and polyimide. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0143] In some embodiments, the separator can further include a heat-resistant coating to improve the heat resistance of the separator. Optionally, the heat-resistant coating can include, but is not limited to, one or more of alumina, boehmite, silicon oxide, zirconium dioxide, magnesium oxide, titanium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, and magnesium nitride.

[0144] The present application also provides a method for preparing a battery cell, which can prepare the battery cell provided by the present application.

[0145] The preparation method of the battery cell comprises the following steps: providing a positive electrode sheet, a separator, a negative electrode sheet, a first non-aqueous electrolyte, and a second non-aqueous electrolyte, the first non-aqueous electrolyte comprising a first solvent and a first lithium salt, the first solvent comprising a nitrile solvent, the second non-aqueous electrolyte comprising a second solvent and a second lithium salt, the second solvent comprising a chain single ether solvent; disposing a polymer layer on the outermost side of the negative electrode sheet, and then impregnating the polymer layer with the second non-aqueous electrolyte to obtain a negative electrode sheet formed with a second gel electrolyte; assembling the positive electrode sheet, the separator, and the negative electrode sheet formed with the second gel electrolyte to obtain a to-be-liquid-injected battery cell; and injecting the first non-aqueous electrolyte into the to-be-liquid-injected battery cell to obtain the battery cell.

[0146] The preparation method of the to-be-liquid-injected battery cell is known. In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet formed with the second gel electrolyte can be wound and / or laminated to form an electrode assembly, and the electrode assembly can be placed in an outer package to obtain the to-be-liquid-injected battery cell.

[0147] The embodiments of the present application also provide a power utilization device comprising the battery provided by the embodiments of the present application. The battery can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0148] The power utilization device can select the type of the battery (such as a battery cell, a battery module, or a battery pack) according to the use requirement of the power utilization device.

[0149] FIG. 5 is a schematic diagram of a power utilization device as an example. The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the power utilization device, a battery pack or a battery module can be used.

[0150] The power utilization device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power utilization device usually requires thinning, and a battery cell can be used as a power supply.

[0151] Embodiments

[0152] The present application is described in more detail by the following examples, which are merely illustrative and not limiting the scope of the present application, since various modifications and changes will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used as received without further purification, and the instruments used in the examples are commercially available.

[0153] Example 1

[0154] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, a positive electrode conductive agent acetylene black, and a positive electrode binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 98:1:1, added to a solvent N-methyl pyrrolidone (NMP), and stirred until the system was uniformly dispersed to obtain a positive electrode slurry; the positive electrode slurry was uniformly coated on a positive electrode current collector aluminum foil, dried, transferred to an oven at 120°C for further drying, and then cut into a 40 mm x 50 mm rectangle as a positive electrode tab for standby.

[0155] A polyethylene porous film was cut into a 45 mm x 55 mm rectangle as a separator film for standby.

[0156] A first lithium salt lithium bisfluorosulfonylimide (LiFSI), a first solvent acetonitrile, a first additive fluoroethylene carbonate (FEC), and lithium difluorophosphate (LiPO2F2) were stirred uniformly to obtain a first non-aqueous electrolyte for standby. The concentration of LiFSI was 1.5 mol / L, the mass fraction of FEC in the first non-aqueous electrolyte was 5%, and the mass fraction of LiPO2F2 was 1%.

[0157] A second lithium salt lithium bisfluorosulfonylimide (LiFSI) and a second solvent dibutyl ether (DBE) were stirred uniformly to obtain a second non-aqueous electrolyte for standby. The concentration of LiFSI was 2 mol / L.

[0158] A lithium ribbon with a thickness of 20 μm was coated on a copper foil with a thickness of 12 μm by rolling, then cut into a 41 mm x 51 mm rectangle, and a layer of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) with a thickness of 5 μm was coated on the outer side of the lithium ribbon, and a second non-aqueous electrolyte was uniformly dropped on the surface of the lithium ribbon at a dosage of 4 μL / cm 2 The subsequent battery cell assembly process was started after the second non-aqueous electrolyte was fully infiltrated.

[0159] Take the cut positive electrode and the cut negative electrode to match, place the above-mentioned separator film in the middle to insulate the positive electrode and the negative electrode, get the electrode assembly, and then wrap it in an aluminum plastic film bag to form a lithium metal battery monomer to be injected; 0.2g of the first non-aqueous electrolyte is injected into the lithium metal battery monomer to be injected, and after the injection is completed, the aluminum plastic film bag is vacuum heat sealed and packaged, and placed at 45℃ for 10h, to obtain a lithium metal battery monomer, which can be subjected to subsequent cycle performance test. The rated capacity of the lithium metal battery monomer is 70mAh.

[0160] Take the above prepared lithium metal battery monomer, set the ambient temperature to 25℃, use 0.2C (i.e. 14mA) constant current charging to reach the cut-off voltage 4.3V, then continue to use 4.3V constant voltage charging until the current decays to 0.1C (i.e. 7mA); then discharge at 2C (i.e. 140mA) constant current to 2.8V to obtain the first cycle discharge capacity. Repeat the above charge and discharge cycle and record the discharge capacity after each cycle. When the discharge capacity decays to 80% of the first cycle discharge capacity, the lithium metal battery monomer is considered to have reached the end of life, and the number of cycles experienced by the lithium metal battery monomer at this time is recorded.

[0161] Example 2

[0162] The preparation method of the lithium metal battery monomer and the cycle performance test method are the same as those of Example 1, except that the composition of the first non-aqueous electrolyte is different.

[0163] The first lithium salt lithium bisfluorosulfonylimide (LiFSI) and lithium bisfluorooxalate borate (LiDFOB), and the first solvent acetonitrile are stirred uniformly to obtain the first non-aqueous electrolyte, which is ready for use. The concentration of LiFSI is 1.2mol / L, and the concentration of LiDFOB is 0.1mol / L.

[0164] Example 3

[0165] The preparation method of the lithium metal battery monomer and the cycle performance test method are the same as those of Example 1, except that the composition of the first non-aqueous electrolyte is different.

[0166] The first lithium salt lithium bisfluorosulfonylimide (LiFSI) and the first solvent acetonitrile are stirred uniformly to obtain the first non-aqueous electrolyte, which is ready for use. The concentration of LiFSI is 1.5mol / L.

[0167] Example 4

[0168] The preparation method of the lithium metal battery monomer and the cycle performance test method are the same as those of Example 1, except that the composition of the second non-aqueous electrolyte is different.

[0169] The second lithium salt lithium bisfluorosulfonylimide (LiFSI), the second solvent dibutyl ether (DBE), and the second additive tetraethylammonium nitrate (TEANO3) were stirred uniformly to obtain a second non-aqueous electrolyte, which was prepared for use. The concentration of LiFSI was 2 mol / L, and the mass fraction of TEANO3 in the second non-aqueous electrolyte was 5%.

[0170] Example 5

[0171] The preparation method of the lithium metal battery cell and the cycle performance test method were the same as those in Example 1, except that the composition of the second non-aqueous electrolyte was different.

[0172] The second lithium salt lithium bisfluorosulfonylimide (LiFSI), the second solvent dibutyl ether (DBE) and methyl n-butyl ether (MBE), and the second additive tetraethylammonium nitrate (TEANO3) were stirred uniformly to obtain a second non-aqueous electrolyte, which was prepared for use. The volume ratio of DBE and MBE was 80:20, the concentration of LiFSI was 2.5 mol / L, and the mass fraction of TEANO3 in the second non-aqueous electrolyte was 5%.

[0173] Example 6

[0174] The preparation method of the lithium metal battery cell and the cycle performance test method were the same as those in Example 1, except that the composition of the second non-aqueous electrolyte was different.

[0175] The second lithium salt lithium bisfluorosulfonylimide (LiFSI) and the second solvent dipropyl ether (DPE) were stirred uniformly to obtain a second non-aqueous electrolyte, which was prepared for use. The concentration of LiFSI was 2 mol / L.

[0176] Example 7

[0177] The preparation method of the lithium metal battery cell and the cycle performance test method were the same as those in Example 1, except that the composition of the second non-aqueous electrolyte was different.

[0178] The second lithium salt lithium bisfluorosulfonylimide (LiFSI) and the second solvent dipropyl ether (DPE) were stirred uniformly to obtain a second non-aqueous electrolyte, which was prepared for use. The concentration of LiFSI was 2 mol / L.

[0179] Example 8

[0180] The preparation method of the lithium metal battery cell and the cycle performance test method were the same as those in Example 1, except that the amount of the second non-aqueous electrolyte was different.

[0181] A lithium strip with a thickness of 20 μm was coated on a copper foil with a thickness of 12 μm by rolling, and then cut into a rectangle with a length of 41 mm and a width of 51 mm. A layer of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) with a thickness of 5 μm was coated on the outer side of the lithium strip, and 3 μL / cm2 The second non-aqueous electrolyte is added in a uniform amount, and after the second non-aqueous electrolyte is fully infiltrated, the subsequent battery cell assembly process is started.

[0182] Example 9

[0183] The preparation method and the cycle performance test method of the lithium metal battery cell are the same as those of Example 1, except that the type of the polymer layer outside the lithium strip of the negative electrode tab is different.

[0184] A lithium strip with a thickness of 20 pm is covered on a copper foil with a thickness of 12 pm by rolling, and then cut into a rectangle with a size of 41 mm x 51 mm. A polyacrylonitrile (PAN) layer with a thickness of 5 pm is coated on the outer side of the lithium strip, and 4 pL / cm2of the second non-aqueous electrolyte is uniformly added on the surface of the PAN layer. 2 The second non-aqueous electrolyte is added in a uniform amount, and after the second non-aqueous electrolyte is fully infiltrated, the subsequent battery cell assembly process is started.

[0185] Example 10

[0186] The lithium metal battery cell prepared in Example 1 is taken, the ambient temperature is set to 25°C, and after 0.2C (i.e., 14 mA) constant current charging is performed to reach a cutoff voltage of 4.3V, 4.3V constant voltage charging is continued until the current decays to 0.1C (i.e., 7 mA); then 5C (i.e., 350 mA) constant current discharging is performed to 2.8V to obtain the first cycle discharge capacity. The above charging and discharging cycle is repeated, and the discharge capacity after each cycle is recorded. When the discharge capacity decays to 80% of the first cycle discharge capacity, the lithium metal battery cell is considered to reach the end of life, and the number of cycles experienced by the lithium metal battery cell at this time is recorded.

[0187] Comparative Example 1

[0188] The preparation method and the cycle performance test method of the lithium metal battery cell are the same as those of Example 1, except that the second non-aqueous electrolyte is not used.

[0189] A lithium strip with a thickness of 20 pm is covered on a copper foil with a thickness of 12 pm by rolling, and then cut into a rectangle with a size of 41 mm x 51 mm. The cut negative electrode tab is taken and matched with the cut positive electrode tab, and the above-mentioned separator film is placed in the middle to separate the positive electrode tab and the negative electrode tab to obtain a laminated electrode assembly, which is then wrapped in an aluminum plastic film bag to form a lithium metal battery cell to be injected. 0.2 g of the first non-aqueous electrolyte is injected into the lithium metal battery cell to be injected, and after the injection is completed, the aluminum plastic film bag is vacuum heat sealed and packaged, and is placed at 45°C for 10 h to obtain the lithium metal battery cell.

[0190] Comparative Example 2

[0191] The preparation method of the lithium metal battery cell and the cycle performance test method are the same as those of Example 1 except that the first non-aqueous electrolyte is not used.

[0192] A lithium strip with a thickness of 20 μm was coated on a copper foil with a thickness of 12 μm by rolling, and then cut into a rectangle with a size of 41 mm x 51 mm as a negative electrode tab for standby. The cut positive electrode tab and the cut negative electrode tab were matched, the above-mentioned separator film was placed in the middle to separate the positive electrode tab and the negative electrode tab to obtain a laminated electrode assembly, and then the laminated electrode assembly was wrapped in an aluminum plastic film bag to form a lithium metal battery cell to be injected with a liquid; 0.2 g of the second non-aqueous electrolyte was injected into the lithium metal battery cell to be injected with a liquid, and after the injection was completed, the aluminum plastic film bag was vacuum heat-sealed and packaged, and then the lithium metal battery cell was obtained after being placed at 45 °C for 10 h.

[0193] It can be known from the test results of Examples 1 to 10 and Comparative Examples 1 to 2 that the lithium metal battery cell using the first non-aqueous electrolyte containing a nitrile-based solvent and the second gel electrolyte containing a chain-like mono-ether solvent has a long cycle life.

[0194] It can be known from the test results of Examples 1 to 3 that further adjusting the composition of the first non-aqueous electrolyte can further improve the positive electrode interface stability and further improve the cycle life of the lithium metal battery cell.

[0195] It can be known from the test results of Examples 1, Examples 4 to 9 that further adjusting the composition and / or amount of the second non-aqueous electrolyte can further improve the negative electrode interface stability and further improve the cycle life of the lithium metal battery cell.

[0196] It can be known from the test results of Examples 1 and Example 10 that the lithium metal battery cell using the first non-aqueous electrolyte containing a nitrile-based solvent and the second gel electrolyte containing a chain-like mono-ether solvent also has good rate performance and still has a long cycle life at a high rate discharge.

[0197] The above only takes the lithium metal battery cell as an example to verify that the lithium metal battery cell using the first non-aqueous electrolyte containing a nitrile-based solvent and the second gel electrolyte containing a chain-like mono-ether solvent has a long cycle life, and other battery cells such as lithium ion battery cells and anode-free lithium metal battery cells using the electrolyte provided in the present application can also have a long cycle life.

[0198] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments, or by combining part of the constituent elements of the embodiments, are also included in the scope of the present application without departing from the spirit of the present application.

Claims

1. A battery cell, comprising a positive electrode, a negative electrode, and an electrolyte, wherein, The electrolyte includes a first non-aqueous electrolyte near the positive electrode and a second gel electrolyte near the negative electrode; The first non-aqueous electrolyte includes a first solvent and a first lithium salt, wherein the first solvent includes a nitrile solvent; The second gel electrolyte includes a polymer layer and a second non-aqueous electrolyte contained in the polymer layer. The second non-aqueous electrolyte includes a second solvent and a second lithium salt. The second solvent includes a chain-like monoether solvent.

2. The battery cell according to claim 1, wherein, The polymer layer comprises one or more copolymers of at least two of the aforementioned polymers, including polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyimide, polyethersulfone, polyvinyl carbonate, polymethyl methacrylate, polyethylene glycol, polyvinyl chloride, and at least two of the aforementioned polymers.

3. The battery cell according to any one of claims 1-2, wherein, The thickness of the polymer layer is 1μm-20μm.

4. The battery cell according to any one of claims 1-3, wherein, The amount of the second non-aqueous electrolyte in the polymer layer is 2.0 μL / cm. 2 -10.0μL / cm 2 .

5. The battery cell according to any one of claims 1-4, wherein, The nitrile solvents include one or more of the following: C2 to C10 alkyl nitriles, C3 to C10 alkenyl nitriles, C3 to C10 alkynyl nitriles, C2 to C10 haloalkyl nitriles, C3 to C10 haloalkenyl nitriles, C3 to C10 haloalkynyl nitriles, C7 to C10 aryl nitriles, and C3 to C10 epoxy nitriles; and / or, The chain-like monoether solvents include C2 to C10 chain-like monoether solvents.

6. The battery cell according to claim 5, wherein, The nitrile solvents include one or more of acetonitrile, propionitrile, butyronitrile, malononitrile, succinic anion, glutaronitrile, 2-methyleneglutaronitrile, and adiponitrile; and / or, The chain-like monoether solvent includes one or more of diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, methyl propyl ether, methyl n-butyl ether, and methyl tert-butyl ether.

7. The battery cell according to any one of claims 1-6, wherein, The electrolyte satisfies one or more of the following conditions (1) to (4): (1) The first lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, and lithium bis(fluorooxalate borate); (2) The second lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethyl)sulfonylimide, lithium bis(trifluoromethyl)sulfonylimide, and lithium bis(fluorooxalate borate). (3) The lithium salt concentration of the first non-aqueous electrolyte is 0.5 mol / L-5 mol / L; (4) The lithium salt concentration of the second non-aqueous electrolyte is 1 mol / L-3 mol / L.

8. The battery cell according to any one of claims 1-7, wherein, The first non-aqueous electrolyte further includes a first additive, which comprises one or more of the following: butyl sulfonate lactone, propenyl-1,3-sulfonate lactone, trifluoromethyl ethyl sulfone, pentafluorophenoxycyclotriphosphazene, triethyl phosphate, tris(trimethylsilane) phosphate, triethyl borate, tris(trimethylsilane) borate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorodioxalate phosphate, and lithium nitrate; and / or, The second non-aqueous electrolyte also includes a second additive, which includes one or more of 1,3-propanesulfonic acid lactone, vinyl sulfate, 1,3-dioxolane, lithium nitrate, tetraethylammonium nitrate, and tetrabutylammonium nitrate.

9. The battery cell according to claim 8, wherein, The mass of the first additive is 0.5%-10% of the total mass of the first non-aqueous electrolyte; and / or, The mass of the second additive is 0.5%-10% of the total mass of the second non-aqueous electrolyte.

10. The battery cell according to any one of claims 1-9, wherein, The positive electrode sheet comprises one or more of lithium phosphate and lithium transition metal oxide; and / or, The negative electrode includes one or more of lithium titanate, carbon-based materials, silicon-based materials, tin-based materials, and lithium metal.

11. A method for preparing a single battery cell, comprising the following steps: A positive electrode, a separator, a negative electrode, a first non-aqueous electrolyte, and a second non-aqueous electrolyte are provided. The first non-aqueous electrolyte includes a first solvent and a first lithium salt. The first solvent includes a nitrile solvent. The second non-aqueous electrolyte includes a second solvent and a second lithium salt. The second solvent includes a chain-like monoether solvent. A polymer layer is disposed on the outermost side of the negative electrode sheet, and then the polymer layer is wetted with the second non-aqueous electrolyte to obtain a negative electrode sheet with a second gel electrolyte formed. The positive electrode, the separator, and the negative electrode with the second gel electrolyte are assembled to obtain a battery cell to be injected with electrolyte. The first non-aqueous electrolyte is then injected into the battery cell to obtain the battery cell.

12. A battery comprising a battery cell according to any one of claims 1-10 or a battery cell prepared by the preparation method according to claim 11.

13. An electrical device comprising the battery of claim 12.

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