Polymer electrolyte membrane, battery cell, battery device, and electric device

Abstract

A polymer electrolyte membrane, a battery cell, a battery device, and an electric device. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and the polymer electrolyte membrane. The polymer electrolyte membrane is located between the positive electrode sheet and the negative electrode sheet. The polymer electrolyte membrane comprises: a first lithium salt, wherein the first lithium salt comprises lithium ions and a carbon chain-containing anionic group, and the carbon chain-containing anionic group comprises a linear alkyl group having eight or more carbon atoms; a second lithium salt other than the first lithium salt; and a polymer.

Description

Polymer electrolyte membranes, battery cells, battery devices, and electrical devices

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application 202411777289.8, filed on December 5, 2024, entitled “Polymer electrolyte membrane, battery cell, battery device and power supply device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of batteries, specifically to a polymer electrolyte membrane, a battery cell, a battery device, and an electrical device. Background Technology

[0004] Concentration polarization during the charging and discharging process of individual battery cells, as well as short circuits that may be caused by dendrite growth, can adversely affect their performance. Therefore, reducing concentration polarization and slowing down dendrite growth have become urgent technical problems to be solved. Summary of the Invention

[0005] This disclosure provides a polymer electrolyte membrane, a battery cell, a battery device, and an electrical device. The polymer electrolyte membrane, when applied to a battery cell, can reduce concentration polarization and slow down dendrite growth in the battery cell.

[0006] In a first aspect, this disclosure provides a battery cell including a positive electrode, a negative electrode, and a polymer electrolyte membrane, wherein the polymer electrolyte membrane is located between the positive electrode and the negative electrode, and the polymer electrolyte membrane includes: a first lithium salt comprising lithium ions and an anionic group containing a carbon chain, wherein the anionic group containing a carbon chain includes a straight-chain alkyl group having 8 or more carbon atoms; a second lithium salt other than the first lithium salt; and a polymer.

[0007] The polymer electrolyte membrane of this embodiment includes a first lithium salt, a second lithium salt, and a polymer. The first lithium salt includes anionic groups containing carbon chains, which include straight-chain alkyl groups with 8 or more carbon atoms. The aforementioned anionic groups containing carbon chains are bound in the network framework formed by the polymer. The bound anionic groups containing carbon chains will repel other anions, reducing the migration rate of anions, thereby increasing the transference number of lithium ions, thereby reducing the concentration polarization of the battery cell and slowing down dendrite growth.

[0008] In some embodiments, the carbon-chain-containing anionic group includes a straight-chain alkyl group with a carbon number greater than or equal to 8 and less than or equal to 50.

[0009] The aforementioned carbon-chain-containing anionic groups have significant steric hindrance, which can improve the stability of the chain entanglement structure formed by the carbon-chain-containing anionic groups and the polymer network, further reducing the migration rate of the anionic groups and increasing the transference number of lithium ions. This can reduce the concentration polarization of the battery cells and slow down dendrite growth.

[0010] In some embodiments, the carbon-chain-containing anionic group includes anions covalently bonded to straight-chain alkyl groups.

[0011] In some embodiments, the anion includes -C6H4SO3 - -SO3 - -SO4 - -C6H4COO - -CO2 - -(SO2)N(SO2CF3) - -(SO2)N(SO2F) - -N(SO2F) - and -N(SO2CF3) - One or more of them.

[0012] The aforementioned anions can utilize electrostatic repulsion to further reduce the migration rate of anionic groups, thereby further increasing the lithium ion transference number, further reducing concentration polarization in battery cells, and slowing down dendrite growth.

[0013] In some embodiments, the first lithium salt includes one or more of lithium oleate, lithium stearate, lithium dodecyl benzoate, lithium hexadecyl benzoate, lithium dodecyl sulfate, lithium heptadecylfluoro-1-octylsulfonate, lithium laurate, lithium palmitate, and lithium dodecylbenzenesulfonate.

[0014] By selecting the aforementioned first lithium salt, the ion transference number of the polymer electrolyte membrane can be further increased, the concentration polarization of the battery cells can be reduced, and dendrite growth can be slowed down.

[0015] In some embodiments, the molar ratio of the first lithium salt to the second lithium salt is 1:99 to 80:20.

[0016] This allows for a balance between the lithium-ion transference number and ionic conductivity of the polymer electrolyte membrane, enabling the polymer electrolyte membrane to possess both a high lithium-ion transference number and a high ionic conductivity, thereby optimizing the effective lithium-ion conductivity.

[0017] In some embodiments, the thickness of the polymer electrolyte membrane is 10-100 μm. This allows the polymer electrolyte membrane to have good processability, as well as suitable electronic resistance and ion transport pathways.

[0018] In some embodiments, the second lithium salt comprises one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. This allows it to work in conjunction with the first lithium salt to increase the lithium-ion transference number of the polymer electrolyte membrane while simultaneously imparting high ionic conductivity.

[0019] In some embodiments, the polymer includes one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, polyacrylonitrile, polyamide, polyethylene glycol, polyurea, polyurethane, and their respective derivatives.

[0020] By selecting the aforementioned polymers, the polymer electrolyte membrane can possess good electrochemical stability. Furthermore, it can not only achieve good electrochemical stability but also exhibit excellent film-forming properties and mechanical properties.

[0021] In some embodiments, the polymer electrolyte membrane has an ionic conductivity of 10. -6 -10 -2 S / cm.

[0022] In some embodiments, the polymer electrolyte membrane further includes a plasticizer. The plasticizer can give the polymer electrolyte membrane good film-forming properties and mechanical properties.

[0023] In some embodiments, the plasticizer includes one or more of carbonate compounds, nitrile compounds, and ether compounds.

[0024] In some embodiments, the plasticizer includes one or more of tetraethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, vinylene carbonate, dipropyl carbonate, methyl ethyl carbonate, succinic acid, 1,3-dioxolane, and tetraethylene glycol dimethyl ether.

[0025] By selecting the aforementioned plasticizers, the ionic conductivity and flexibility of the polymer electrolyte membrane can be improved. These plasticizers are not easily volatile and possess good electrochemical stability.

[0026] In a second aspect, this disclosure provides a polymer electrolyte membrane, comprising: a first lithium salt comprising lithium ions and an anionic group containing a carbon chain, the anionic group containing a carbon chain comprising a straight-chain alkyl group having 8 or more carbon atoms; a second lithium salt other than the first lithium salt; and a polymer.

[0027] Thirdly, this disclosure provides a battery device including a battery cell according to the second aspect of this disclosure.

[0028] Fourthly, this disclosure provides an electrical device, including a battery cell according to the second aspect of this disclosure or a battery device according to the third aspect of this disclosure. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0030] Figure 1 is a schematic diagram of one embodiment of the battery cell of this disclosure.

[0031] Figure 2 is a schematic diagram of one embodiment of an electrical device that uses the battery device disclosed herein as a power source.

[0032] Figure 3 is a test diagram of the DC polarization curves of the polymer electrolyte membranes of Example 1 and Comparative Example 1 of this disclosure.

[0033] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0034] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the polymer electrolyte membrane, battery cell, battery device, and power-consuming device of this disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0035] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​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 disclosure, 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.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the content of this disclosure.

[0037] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the content of this disclosure.

[0038] Unless otherwise specified, all steps in this disclosure 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 method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0040] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0041] The battery cells mentioned in the embodiments of this disclosure are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and this disclosure does not limit this. Figure 1 shows a cuboid battery cell 5 as an example.

[0042] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0043] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0044] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0045] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0046] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0047] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0048] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0049] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0050] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0051] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, 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. Battery cells and battery devices are used to store or provide electrical energy.

[0052] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0053] The battery cell provided in the embodiments of this disclosure includes an electrode assembly and an outer packaging, the outer packaging being used to encapsulate the electrode assembly. The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0054] Polymer electrolyte membranes are mainly composed of polymers, lithium salts, and additives. Ion transport depends on the chain segment movement of the polymer. Due to the dissociation of the lithium salt, both anions and lithium ions migrate under the influence of an electric field. Furthermore, the polymer backbone has a strong complexing effect with lithium ions, resulting in a relatively low lithium ion transference number (around 0.2) in polymer electrolyte membranes. This low lithium ion transference number can cause concentration polarization during the charging and discharging process of individual battery cells.

[0055] In addition, according to Sand's equation, a lower lithium-ion transference number will accelerate dendrite growth in lithium metal battery cells, causing short circuits in lithium metal battery cells.

[0056] Sand's equation proposes the critical time from dendrite nucleation to growth:

[0057] Among them, z c Here, c0 is the cation charge number, c0 is the macroscopic salt concentration, F is the Faraday constant, J is the current density, and D is the current density. app It is the apparent diffusion coefficient.

[0058] In related technologies, single-ion conductors are mainly used to improve the lithium-ion transference number. However, the synthesis of single-ion conductors is complex, and their ionic conductivity is low, typically less than 10, at 25±5℃. -6 S / cm. Furthermore, polymer electrolyte membranes employing single-ion conductors are not conducive to industrialization.

[0059] In view of this, embodiments of the present disclosure provide a battery cell including a positive electrode, a negative electrode, and a polymer electrolyte membrane, wherein the polymer electrolyte membrane is located between the positive electrode and the negative electrode, and the polymer electrolyte membrane includes: a first lithium salt: the first lithium salt includes lithium ions and an anionic group containing a carbon chain, the anionic group containing a carbon chain including a straight-chain alkyl group having 8 or more carbon atoms; a second lithium salt other than the first lithium salt; and a polymer.

[0060] The migration rate of lithium ions is inversely proportional to their diameter, and their movement within the polymer is constrained by the polymer network. When the molecular chains of the first lithium salt are sufficiently long, they will form chain entanglement with the polymer network. Therefore, after introducing the first lithium salt into the polymer electrolyte membrane, the carbon-containing anionic groups in the first lithium salt can form chain entanglement with the polymer network, thus limiting the migration rate of the carbon-containing anionic groups.

[0061] The polymer electrolyte membrane of this embodiment includes a first lithium salt, a second lithium salt, and a polymer. The first lithium salt includes anionic groups containing carbon chains, which include straight-chain alkyl groups with 8 or more carbon atoms. The aforementioned anionic groups containing carbon chains are bound in the network framework formed by the polymer. The bound anionic groups containing carbon chains will repel other anions, reducing the migration rate of anions, thereby increasing the transference number of lithium ions, thereby reducing the concentration polarization of the battery cell and slowing down dendrite growth.

[0062] It should be noted that the anions repelled by the anionic groups mentioned above may include anions in the first lithium salt and anions in the second lithium salt.

[0063] The straight-chain alkyl group of the first lithium salt may contain branches, or one or more hydrogen atoms in the straight-chain alkyl group may be replaced by other atoms or groups, such as fluorine atoms, chlorine atoms, phenyl groups, cycloalkyl groups, etc.

[0064] In some embodiments, the carbon-chain-containing anionic group may include a straight-chain alkyl group with 8 or more carbon atoms and 50 or less. For example, it may include a straight-chain alkyl group with 8 carbon atoms, a straight-chain alkyl group with 9 carbon atoms, a straight-chain alkyl group with 10 carbon atoms, a straight-chain alkyl group with 11 carbon atoms, a straight-chain alkyl group with 12 carbon atoms, a straight-chain alkyl group with 16 carbon atoms, a straight-chain alkyl group with 20 carbon atoms, a straight-chain alkyl group with 30 carbon atoms, a straight-chain alkyl group with 40 carbon atoms, and a straight-chain alkyl group with 50 carbon atoms.

[0065] The aforementioned carbon-chain-containing anionic groups have significant steric hindrance, which can improve the stability of the chain entanglement structure formed by the carbon-chain-containing anionic groups and the polymer network, further reducing the migration rate of the anionic groups and increasing the transference number of lithium ions. This can reduce the concentration polarization of the battery cells and slow down dendrite growth.

[0066] In some embodiments, the carbon-chain-containing anionic group may include an anion covalently bonded to a straight-chain alkyl group.

[0067] In some embodiments, the anion may include -C6H4SO3 - -SO3 - -SO4 - -C6H4COO - -CO2 - -(SO2)N(SO2CF3) - -(SO2)N(SO2F) - -N(SO2F) - and -N(SO2CF3) - One or more of them.

[0068] The aforementioned anions can utilize electrostatic repulsion to further reduce the migration rate of anionic groups, thereby further increasing the lithium ion transference number, further reducing concentration polarization in battery cells, and slowing down dendrite growth.

[0069] In some embodiments, the first lithium salt may include one or more of lithium oleate, lithium stearate, lithium dodecyl benzoate, lithium hexadecyl benzoate, lithium dodecyl sulfate, lithium heptadecylfluoro-1-octylsulfonate, lithium laurate, lithium palmitate, and lithium dodecylbenzenesulfonate.

[0070] By selecting the aforementioned first lithium salt, the ion transference number of the polymer electrolyte membrane can be further increased, the concentration polarization of the battery cells can be reduced, and dendrite growth can be slowed down.

[0071] In some embodiments, the molar ratio of the first lithium salt to the second lithium salt can be from 1:99 to 80:20, for example, it can be 1:99, 10:90, 20:80, 30:70, 50:50, 60:40, 70:30, 80:20, or any range of two of the above values. A ratio of 10:90 to 30:70 is also possible.

[0072] By adjusting the molar ratio of the first lithium salt to the second lithium salt within the aforementioned range, the relationship between the lithium-ion transport number and ionic conductivity of the polymer electrolyte membrane can be balanced, enabling the polymer electrolyte membrane to possess both a high lithium-ion transport number and a high ionic conductivity, thereby optimizing the effective lithium-ion conductivity. In the embodiments of this application, "effective lithium-ion conductivity" refers to the product of ionic conductivity and lithium-ion transport number.

[0073] In some embodiments, the thickness of the polymer electrolyte membrane can be 10-100 μm, for example, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any range of two of the above values.

[0074] By adjusting the thickness of the polymer electrolyte membrane within the above range, the polymer electrolyte membrane can have good processing performance, as well as suitable electronic resistance and ion transport pathways.

[0075] In some embodiments, the second lithium salt may include one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium dioxolaneborate (LiBOB), lithium difluorooxolaneborate (LiBOB), lithium difluorophosphate, lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate, lithium difluorodioxolane phosphate, and lithium tetrafluorooxolane phosphate.

[0076] The dissociation of the first lithium salt is more difficult than that of the second lithium salt. In this embodiment of the present disclosure, by selecting the second lithium salt, it can work together with the first lithium salt to increase the lithium ion transference number of the polymer electrolyte membrane while giving it a higher ionic conductivity.

[0077] In some embodiments, the second lithium salt may include one or both of lithium bisfluorosulfonylimide (LiFSI) and lithium bistrifluoromethanesulfonylimide (LiTFSI). The aforementioned second lithium salt exhibits good electrochemical stability, and its larger anion size enhances the electrostatic repulsion between the anions in the second lithium salt and the anions in the first lithium salt. Furthermore, the high degree of dissociation of the second lithium salt further improves the ionic conductivity of the polymer electrolyte membrane.

[0078] In some embodiments, the polymer may include one or more of polyethylene oxide (PEO), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyamide (PA), polyethylene glycol, polyurea, polyurethane, and their respective derivatives.

[0079] Derivatives are products derived from polymers by replacing hydrogen atoms or groups of atoms with other atoms or groups of atoms.

[0080] By selecting the aforementioned polymers, the polymer electrolyte membrane can possess good electrochemical stability. Furthermore, it can not only achieve good electrochemical stability but also exhibit excellent film-forming properties and mechanical properties.

[0081] In some embodiments, the ionic conductivity of the polymer electrolyte membrane can be 10. -6 -10 -2 S / cm, for example, can be 10 -6 S / cm, 5×10 -6 S / cm, 10 -5 S / cm, 5×10 -5 S / cm, 10 -4 S / cm, 5×10 -4 S / cm, 10 -3 S / cm, 5×10 -3 S / cm, 10 -2 S / cm.

[0082] In some embodiments, the polymer electrolyte membrane may also include a plasticizer. The plasticizer can impart good film-forming properties and mechanical properties to the polymer electrolyte membrane.

[0083] In some embodiments, the mass ratio of the plasticizer to the sum of the masses of the first lithium salt and the second lithium salt can be (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1, or 5:1.

[0084] In some embodiments, the plasticizer may include one or more of carbonate compounds, nitrile compounds, and ether compounds.

[0085] In some embodiments, the plasticizer may include one or more of tetraethylene glycol dimethyl ether (G4), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), vinylene carbonate (VC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), succinic acid (SN), 1,3-dioxolane (DOL), and tetraethylene glycol dimethyl ether.

[0086] By selecting the aforementioned plasticizers, the ionic conductivity and flexibility of the polymer electrolyte membrane can be improved. These plasticizers are not easily volatile and possess good electrochemical stability.

[0087] The battery cells provided in the embodiments of this disclosure can be lithium-ion battery cells, metal battery cells, or negative electrode-free metal battery cells, such as lithium-ion battery cells, lithium metal battery cells, or negative electrode-free lithium metal battery cells.

[0088] Electrodeless lithium metal battery cells typically refer to battery cells manufactured without actively depositing a negative electrode active material layer on the negative electrode side. For example, during manufacturing, a negative electrode active material layer of carbonaceous materials is not applied or deposited at the negative electrode. During the first charge, ions gain electrons on the negative electrode side and deposit a metallic phase on the surface of the negative electrode current collector. During discharge, the metal transforms into metal ions and returns to the positive electrode, achieving cyclic charging and discharging. Compared to other battery cells, electrodeless lithium metal battery cells can achieve higher energy density due to the absence of a negative electrode active material layer.

[0089] In some embodiments, to improve the performance of a single battery cell, the negative electrode side of a lithium metal battery cell without a negative electrode can also contain some conventional materials that can be used as negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, because their content is small and they are not used as the main negative electrode active material in the battery cell, the battery cell constructed in this way can still be regarded as a lithium metal battery cell without a negative electrode. The CB value of a lithium metal battery cell without a negative electrode is usually very small; for example, in some embodiments, the CB value of a lithium metal battery cell without a negative electrode 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 a lithium metal battery cell without a negative electrode contains no or only a small amount of negative electrode active material, the capacity per unit area of ​​the negative electrode is small, and therefore the CB value is very small, for example, usually less than or equal to 0.1.

[0090] In some embodiments, the battery cell can be a lithium metal solid-state battery. Applying a polymer electrolyte membrane to the aforementioned battery cell can increase the lithium-ion transference number, reduce concentration polarization, and slow down dendrite growth.

[0091] [Polymer electrolyte membrane]

[0092] The polymer electrolyte membrane comprises: a first lithium salt, which includes lithium ions and carbon-chain anionic groups, the carbon-chain anionic groups including straight-chain alkyl groups with 8 or more carbon atoms; a second lithium salt other than the first lithium salt; and a polymer.

[0093] [Preparation method of polymer electrolyte membrane]

[0094] This disclosure also provides a method for preparing a polymer electrolyte membrane, which can prepare the above-mentioned polymer electrolyte membrane.

[0095] In some embodiments, the preparation method may include the following steps:

[0096] A mixture comprising a polymer, a first lithium salt, a second lithium salt, a plasticizer, and a solvent is provided;

[0097] After casting and drying, the mixture is used to obtain a polymer electrolyte membrane.

[0098] In some embodiments, the preparation method may further include mixing a first lithium salt and a second lithium salt to obtain a lithium salt mixture, then mixing the lithium salt mixture with a polymer, a plasticizer, and a solvent, and then casting and drying the mixture to obtain a polymer electrolyte membrane.

[0099] In some embodiments, the solvent may include one or more of tetrahydrofuran (THF), N-methylpyrrolidone (NMP), acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, ethylene glycol, dimethyl sulfoxide, and water.

[0100] [Positive electrode plate]

[0101] In some embodiments, the positive electrode may include a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, the positive electrode film layer including a positive active material. The positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0102] In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides and their modified forms, lithium phosphates and their modified forms, lithium titanate, sulfur, selenium, and tellurium.

[0103] Optionally, examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and lithium-rich manganese-based materials.

[0104] Optionally, examples of lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0105] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e A fOne or more of lithium transition metal oxides and their modified materials. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A may include one or more of N, F, S and Cl.

[0106] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and 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 0.83 Mn 0.08 Co 0.07 O2 (abbreviated as Ni83), LiNi 0.90 Mn 0.05 Co 0.05 O2 (abbreviated as Ni90), LiNi 0.94 Mn 0.03 Co 0.03 O2 (abbreviated as Ni94), LiNi 0.96 Co 0.02 Mn 0.02 O2 (abbreviated as Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2, LiFePO4, LiMnPO4 and their respective modified materials.

[0107] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content represents the initial state of the material, i.e., the state before material addition. As the positive electrode active material is applied to the battery cell, the molar Li content changes after charge-discharge cycles. Similarly, the molar O content in the examples of positive electrode active materials in this disclosure is only a theoretical value. Oxygen release from the crystal lattice causes changes in the molar O content, leading to fluctuations in the actual molar O content.

[0108] The modified materials for the above-mentioned positive electrode active materials can be doped and / or surface coated.

[0109] In some embodiments, the positive electrode film layer may further include a positive electrode binder, which may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0110] In some embodiments, the positive electrode film may further include a positive electrode conductive agent, which may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0111] In some embodiments, the positive current collector may be a metal foil or a composite current collector. Examples of metal foils include carbon-coated aluminum foil, aluminum foil, nickel foil, and titanium foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene.

[0112] [Negative electrode plate]

[0113] In some embodiments, the negative electrode may include one or more of lithium, lithium alloy, natural graphite, artificial graphite, mesophase micro carbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and metal oxides.

[0114] Optionally, the mass fraction of lithium in the lithium alloy can be above 90%.

[0115] Optionally, other elements in the lithium alloy may include, but are not limited to, one or more of In, Mg, Al, Zn, Sn, Ag, Au, Ga, Pt, and Fe.

[0116] Alternatively, the lithium alloy may include, but is not limited to, InLi alloy, Li-Mg alloy, Li-Al alloy, Li-Zn alloy, Li-Fe alloy, etc.

[0117] Optionally, the silicon-based material may include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.

[0118] Optionally, the tin-based material may include, but is not limited to, one or more of elemental tin, tin oxide, and tin alloy materials.

[0119] Optionally, the metal oxide may be one or more of TiO2, MoO2, In2O3, Al2O3, Cu2O, VO2, Ga2O3, Sb2O5, and Bi2O5.

[0120] In some embodiments, the negative electrode sheet can be a lithium sheet or a lithium alloy sheet.

[0121] In some embodiments, the negative electrode may include a negative current collector and a lithium-based metal layer located on at least one surface of the negative current collector. The negative current collector has two surfaces opposite each other in its thickness direction, and the lithium-based metal layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0122] In some embodiments, the lithium-based metal layer may be lithium or a lithium alloy.

[0123] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, the negative electrode film layer comprising a negative electrode active material. The negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0124] In some embodiments, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, mesophase micro carbon spheres, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and metal oxides.

[0125] In some embodiments, the negative electrode film layer may further include a negative electrode binder, which may include, but is not limited to, one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS), methyl vinyl silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), thermoplastic styrene-butadiene rubber (SBS), isoprene rubber, cis-butadiene rubber (BR), ethyl cellulose, fluororubber, and acrylate rubber.

[0126] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent, which may include, but is not limited to, one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, and vapor-grown carbon fibers (VGCF).

[0127] In some embodiments, the negative electrode may include a negative current collector but does not include a lithium-based metal layer or a negative electrode film layer. During the cyclic charging and discharging of a lithium metal battery cell without a negative electrode, lithium from the positive electrode will be deposited and stripped off as lithium metal on the negative electrode side. Optionally, a lithiophilic layer may also be provided on the surface of the negative current collector layer.

[0128] In some embodiments, the negative electrode current collector can be a metal foil, a three-dimensional porous current collector, or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, and aluminum foam. The composite current collector can include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer material substrates include, but are not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0129] The preparation methods for battery cells are well known.

[0130] In some embodiments, a positive electrode, a polymer electrolyte membrane, and a negative electrode can be assembled to obtain an electrode assembly, and the electrode assembly can be placed in an outer package to obtain a battery cell.

[0131] Example

[0132] The following examples describe the contents of this disclosure in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0133] Example 1

[0134] Preparation of polymer electrolyte membranes

[0135] Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 20:80 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0136] Preparation of lithium metal battery cells

[0137] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, positive electrode binder polyvinylidene fluoride (PVDF), lithium bis(trifluoromethanesulfonyl)imide, and positive electrode conductive agent acetylene black were mixed in a mass ratio of 8:1:0.5:0.5. Then, N-methylpyrrolidone was added and stirred to form a uniform positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of the current collector aluminum foil, achieving an areal density of 5 mg / cm³ for the positive electrode active material. 2 After drying and cold pressing, it is cut into rectangles of 42mm×49.5mm to serve as positive electrode sheets.

[0138] A 50μm thick lithium foil is combined with a copper foil by rolling, and then cut into a 53.5mm×51mm rectangle to serve as the negative electrode.

[0139] A positive electrode and a negative electrode are matched and separated by a polymer electrolyte membrane. Then, the electrode tabs are welded together, and the electrode is then wrapped in an aluminum-plastic film outer packaging bag for sealing. After that, it is hot-pressed at 70°C for 180 seconds and then left to stand at 25°C for 6 hours to obtain a lithium metal battery cell with a rated capacity of 20.79mAh.

[0140] Example 2

[0141] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0142] Preparation of polymer electrolyte membrane: Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 40:60 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0143] Example 3

[0144] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0145] Preparation of polymer electrolyte membrane: Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 60:40 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0146] Example 4

[0147] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0148] Preparation of polymer electrolyte membrane: Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 80:20 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0149] Example 5

[0150] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0151] Preparation of polymer electrolyte membrane: Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 5:95 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0152] Example 6

[0153] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0154] Preparation of polymer electrolyte membrane: Lithium dodecyl sulfate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 20:80 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0155] Example 7

[0156] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0157] Preparation of polymer electrolyte membrane: Lithium dodecyl sulfate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 40:60 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0158] Example 8

[0159] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0160] Preparation of polymer electrolyte membrane: Lithium dodecyl sulfate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 60:40 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0161] Example 9

[0162] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0163] Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 20:80 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:0.5 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0164] Example 10

[0165] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0166] Lithium stearate and lithium bisfluorosulfonyl imide (LiFSI) were mixed at a molar ratio of 20:80 to obtain a lithium salt mixture. The above lithium salt mixture, polyethylene oxide (PEO) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in acetonitrile. The mixture was cast and dried under a forced-air drying condition at 60°C to allow the acetonitrile to evaporate, thus preparing a polymer electrolyte membrane with a thickness of 80 μm.

[0167] Example 11

[0168] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0169] Lithium stearate and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were mixed at a molar ratio of 20:80 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0170] Example 12

[0171] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0172] Lithium stearate and lithium bis(fluorosulfonyl)imide (LiFSI) were mixed at a molar ratio of 20:80 to obtain a lithium salt mixture. The above lithium salt mixture, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and diethyl carbonate were mixed evenly at a mass ratio of 1:1.3:1 and dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0173] Comparative Example 1

[0174] Except for the following differences, the preparation method of the lithium metal battery cell is the same as that in Example 1.

[0175] Preparation of polymer electrolyte membrane: Lithium bis(fluorosulfonyl)imide (LiFSI), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and tetraethylene glycol dimethyl ether (G4) were mixed evenly in a mass ratio of 1:1.3:1 and then dissolved in tetrahydrofuran (THF). The mixture was cast and dried at 25°C to obtain a polymer electrolyte membrane with a thickness of 80 μm.

[0176] Test section

[0177] (1) Ionic conductivity test of polymer electrolyte membrane

[0178] Polymer electrolyte membranes were assembled into stainless steel / polymer electrolyte membrane / stainless steel symmetric blocking cells for electrochemical impedance spectroscopy (EIS) testing at a scan frequency of 10. 6 The frequency range is Hz-0.01Hz, with an amplitude of 10mV. The intersection of the imaginary and real parts represents the bulk resistance R, L is the thickness of the composite electrolyte membrane, and S is the electrode area. The ionic conductivity of the polymer electrolyte membrane is calculated using the following formula:

[0179] σ = L / SR.

[0180] (2) Lithium-ion transference number test of polymer electrolyte membrane

[0181] A Li / polymer electrolyte membrane / Li symmetric non-blocking battery was assembled using a polymer electrolyte membrane for DC polarization testing, with a DC polarization voltage of 10 mV. AC impedance (EIS) tests were performed before and after the DC polarization test, with an amplitude of 10 mV and a frequency of 10. 6 Hz-0.01Hz. Calculate the lithium-ion transference number of the polymer electrolyte membrane using the following formula.

[0182] Among them, I 0 and Is These represent the initial and steady-state currents, respectively; ΔV is the polarization voltage (10mV) applied to the Li-Li symmetric cell. and The figures represent the interfacial impedances between the polymer electrolyte membrane and lithium metal obtained by EIS testing before and after DC polarization.

[0183] (3) Cycle capacity retention of lithium metal battery cells

[0184] The lithium metal battery cells were cycled at 60°C using 0.1C (2mA) charging and 0.1C (2mA) discharging rates. Specifically, the lithium metal battery cells were charged at a constant current rate of 0.1C to 4.3V, followed by constant voltage charging until the current decayed to 0.05C; then discharged at a constant current rate of 0.1C to 2.8V to obtain the first discharge capacity. The same charge-discharge cycle was then performed for 100 cycles. The capacity retention rate was obtained by dividing the discharge capacity of the last cycle by the discharge capacity of the first cycle.

[0185] The test results of Examples 1-12 and the comparative examples are shown in Table 1.

[0186] Table 1

[0187] The test results above show that by adjusting the composition of the polymer electrolyte membrane, the lithium-ion transference number of the polymer electrolyte membrane can be increased, the concentration polarization of the lithium metal battery cells can be reduced, and dendrite growth can be slowed down.

[0188] Figure 3 shows the DC polarization curves of the polymer electrolyte membranes of Example 1 and Comparative Example 1. As can be seen from Figure 3, the rate of change of the curve of Example 1 is significantly lower than that of the curve of Comparative Example 1, that is, the lithium-ion transport number of Example 1 is higher than that of Comparative Example 1.

[0189] It should be noted that this disclosure 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 disclosure are included within the technical scope of this disclosure. 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, are also included within the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A battery cell, comprising a positive electrode, a negative electrode, and a polymer electrolyte membrane, wherein the polymer electrolyte membrane is located between the positive electrode and the negative electrode, wherein, The polymer electrolyte membrane comprises: First lithium salt: The first lithium salt includes lithium ions and anionic groups containing carbon chains, wherein the anionic groups containing carbon chains include straight-chain alkyl groups with 8 or more carbon atoms. The second lithium salt other than the first lithium salt; and polymer.

2. The battery cell according to claim 1, wherein, The carbon-chain-containing anionic group includes straight-chain alkyl groups with 8 or more carbon atoms and 50 or less.

3. The battery cell according to claim 1 or 2, wherein, The carbon-chain anionic group includes anions covalently bonded to the straight-chain alkyl group.

4. The battery cell according to claim 3, wherein, The anion includes -C6H4SO3 - -SO3 - -SO4 - -C6H4COO - -CO2 - -(SO2)N(SO2CF3) - -(SO2)N(SO2F) - -N(SO2F) - and -N(SO2CF3) - One or more of them.

5. The battery cell according to any one of claims 1-4, wherein, The first lithium salt includes one or more of lithium oleate, lithium stearate, lithium dodecyl benzoate, lithium hexadecyl benzoate, lithium dodecyl sulfate, lithium heptafluoro-1-octyl sulfonate, lithium laurate, lithium palmitate, and lithium dodecylbenzene sulfonate.

6. The battery cell according to any one of claims 1-5, wherein, The molar ratio of the first lithium salt to the second lithium salt is 1:99 to 80:

20.

7. The battery cell according to any one of claims 1-6, wherein, The thickness of the polymer electrolyte membrane is 10-100 μm.

8. The battery cell according to any one of claims 1-7, wherein, The second lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

9. The battery cell according to any one of claims 1-8, wherein, The polymers include one or more of polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, polyacrylonitrile, polyamide, polyethylene glycol, polyurea, polyurethane, and their respective derivatives.

10. The battery cell according to any one of claims 1-9, wherein, The polymer electrolyte membrane has an ionic conductivity of 10. -6 -10 -2 S / cm.

11. The battery cell according to any one of claims 1-10, wherein, The polymer electrolyte membrane also includes a plasticizer; Optionally, the plasticizer includes one or more of carbonate compounds, nitrile compounds, and ether compounds; Optionally, the plasticizer includes one or more of tetraethylene glycol dimethyl ether, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, vinylene carbonate, dipropyl carbonate, methyl ethyl carbonate, succinic acid, 1,3-dioxolane, and tetraethylene glycol dimethyl ether.

12. A polymer electrolyte membrane, wherein, include: First lithium salt: The first lithium salt includes lithium ions and anionic groups containing carbon chains, wherein the anionic groups containing carbon chains include straight-chain alkyl groups with 8 or more carbon atoms. The second lithium salt other than the first lithium salt; and polymer.

13. A battery device, wherein, It includes the battery cells described in any one of claims 1-11.

14. An electrical appliance, wherein, Includes the battery cell as described in any one of claims 1-11 or the battery device as described in claim 13.

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