Positive electrode sheet, metal battery cell and manufacturing method therefor, battery device, and electric device

Abstract

The present disclosure provides a positive electrode sheet, a metal battery cell and a manufacturing method therefor, a battery device, and an electric device. The metal battery cell comprises an electrode assembly and an electrolyte; the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator; the positive electrode sheet comprises a positive electrode current collector, a positive electrode film layer located on at least one side of the positive electrode current collector and comprising a positive electrode active material, and a lithium salt layer located between the positive electrode current collector and the positive electrode film layer; the lithium salt layer comprises a first lithium salt, a first conductive agent, and a first binder; the first lithium salt includes one or more of a lithium salt having a structure represented by formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro(dioxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate; and R1 and R2 are each independently selected from a fluorine atom or a C1-C6 fluoroalkyl group. The metal battery cell of the present disclosure has good cycle performance.

Description

Positive electrode sheet, metal battery cell and its preparation method, battery device, electrical device

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510192233.4, filed on February 20, 2025, entitled “Positive electrode sheet, metal battery cell and preparation method thereof, battery device, power device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a positive electrode sheet, a metal battery cell and its preparation method, a battery device, and an electrical device. Background Technology

[0004] Lithium-ion battery cells have been widely used in consumer electronics, electric vehicles, and energy storage technologies, but their energy density is approaching its theoretical limit. To meet the higher energy density demands of future high-range electric vehicles and electric aircraft, it is necessary to develop metal battery cells using lithium metal anodes. Lithium metal possesses a high theoretical specific capacity (3860 mAh / g) and a low redox potential (-3.04 V vs. standard hydrogen electrode), making metal battery cells one of the most promising next-generation battery systems. However, lithium metal is highly reactive and spontaneously reacts with the electrolyte to form a solid electrolyte interphase (SEI) film with poor mechanical strength and chemical stability. During discharge, this SEI film is easily broken and difficult to reuse; furthermore, the continuous side reactions between lithium metal and the electrolyte lead to continuous electrolyte consumption and increased polarization of the metal battery cell, resulting in a rapid decline in the cycle life of the metal battery cell. The above statements are for providing background information related to this disclosure only and do not necessarily constitute prior art. Summary of the Invention

[0005] This disclosure provides a positive electrode sheet, a metal battery cell, a method for preparing the same, a battery device, and an electrical device. The metal battery cell has good cycle performance.

[0006] In a first aspect, this disclosure provides a metal battery cell, including an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The positive electrode includes a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer includes a first lithium salt, a first conductive agent, and a first binder. The first lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R1 and R2 each independently include fluorine atoms or C1-C6 fluoroalkyl groups.

[0007] As the metal battery cell cycles through charging and discharging, the lithium salt in the electrolyte is continuously consumed. Since the organic solvent is not significantly consumed, the electrolyte concentration decreases continuously. The first lithium salt in the lithium salt layer of the positive electrode can gradually dissolve into the electrolyte to replenish the consumed lithium salt. This allows the electrolyte to maintain a high concentration during the cycle of the metal battery cell, thus maintaining a good solvation structure and high oxidation-reduction resistance, thereby improving the cycle performance of the metal battery cell.

[0008] In some embodiments, the first lithium salt comprises a lithium salt having the structure shown in Formula 1. The lithium salt having the structure shown in Formula 1 has a wide electrochemical window, high thermal stability, and high ionic conductivity, thereby providing less electrolyte high-pressure decomposition and faster ion transport rates.

[0009] In some embodiments, R1 and R2 each independently include a fluorine atom or a trifluoromethyl group.

[0010] In some embodiments, the first lithium salt accounts for 40%-98% of the mass of the lithium salt layer; the first conductive agent accounts for 1%-30% of the mass of the lithium salt layer; and the first binder accounts for 1%-30% of the mass of the lithium salt layer.

[0011] The first conductive agent imparts good electronic conductivity and low resistance to the lithium salt layer, while the first binder bonds the first lithium salt and the first conductive agent to the positive electrode current collector. When the mass percentage of the first lithium salt is within the aforementioned range, it allows the lithium salt layer to provide more first lithium salt without affecting the positive electrode impedance or increasing positive electrode polarization. This enables the metal battery cell to better maintain the solvation structure of the electrolyte during cycling, maintain high oxidation-reduction resistance of the electrolyte, and ultimately improve the cycle performance of the metal battery cell.

[0012] Optionally, in the lithium salt layer, the first lithium salt accounts for 70%-90% of the mass; in the lithium salt layer, the first conductive agent accounts for 5%-15% of the mass; and in the lithium salt layer, the first binder accounts for 5%-15% of the mass.

[0013] In some embodiments, the thickness of the lithium salt layer is 1 μm-20 μm. Within this range, the lithium salt layer provides more first lithium salt without affecting the positive electrode impedance or increasing positive electrode polarization. This allows the solvation structure of the electrolyte to be better maintained during the cycling process of the metal battery cell, ensuring the electrolyte maintains high oxidation-reduction resistance, and thus enabling the metal battery cell to have better cycle performance. Furthermore, as the first lithium salt is consumed, the first conductive agent and the first binder deform under the clamping force, causing the lithium salt layer to continuously thin. Therefore, within the aforementioned range, the thickness of the lithium salt layer can also alleviate, to some extent, the irreversible volume expansion caused by the accumulation of electrolyte decomposition products during the cyclic charging and discharging of the metal battery cell.

[0014] In some embodiments, the compaction density of the lithium salt layer is 2 g / cm³. 3 -5g / cm 3 The compaction density of the lithium salt layer within the above range is beneficial for the subsequent coating of the cathode slurry, improves the coating quality of the cathode film, and also improves the cycle performance of the metal battery cell.

[0015] In some embodiments, the electrolyte comprises a second lithium salt, an organic solvent, and a diluent. The second lithium salt comprises one or more of the following: lithium salt having the structure shown in Formula 2, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R3 and R4 each independently comprise a fluorine atom or a C1-C6 fluoroalkyl group.

[0016] In some embodiments, the second lithium salt comprises a lithium salt having the structure shown in Formula 2. The lithium salt having the structure shown in Formula 2 has a wide electrochemical window, high thermal stability, and high ionic conductivity, thereby providing less electrolyte high-pressure decomposition and faster ion transport rates.

[0017] In some embodiments, R3 and R4 each independently include a fluorine atom or a trifluoromethyl group.

[0018] In some embodiments, the molar ratio of the second lithium salt, organic solvent, and diluent in the electrolyte is 1:(0.8-3):(0.5-5). This forms a locally highly concentrated electrolyte, which can give the electrolyte a good solvation structure, good oxidation-reduction resistance, and thus good cycle performance of the metal battery cell.

[0019] In some embodiments, the organic solvent includes ether compounds. This is because ether compounds are more compatible with lithium metal anodes.

[0020] Optionally, the organic solvent includes one or more of methyl n-butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,2-dimethoxypropane, 1,3-dimethoxypropane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0021] In some embodiments, the diluent includes one or more of fluoroether diluents, aromatic diluents, and fluoroaromatic diluents.

[0022] Optionally, the diluent includes 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl, 1-(1,1,2,2-tetrafluoroethoxy)propane, 1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 2,2, One or more of the following: 3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ester, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,3,3,3-pentafluoropropyl difluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, benzene, 3-fluorobenzene, m-difluorobenzene, 1,3,5-trifluorobenzene, and anisole.

[0023] In some embodiments, the sum of the mass of the first lithium salt in the lithium salt layer and the mass of the second lithium salt in the electrolyte is greater than the saturated solubility in the organic solvent and diluent. During the cycling of the metal battery cell, the second lithium salt in the electrolyte is continuously consumed. The first lithium salt in the lithium salt layer of the positive electrode can gradually dissolve into the electrolyte under the wetting effect of the electrolyte to replenish the consumption of the second lithium salt. This allows the electrolyte to maintain a high concentration during the cycling of the metal battery cell, thereby maintaining a good solvation structure during the cycling process and ensuring high oxidation-reduction resistance of the electrolyte. Consequently, the metal battery cell can have better cycle performance.

[0024] In some embodiments, the positive electrode active material includes one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds.

[0025] In some embodiments, the negative electrode sheet includes a negative current collector and a lithium metal layer located on at least one side of the negative current collector. The lithium metal layer includes elemental lithium metal or an alloy formed by lithium metal and other metal elements and / or non-metal elements. Alternatively, the negative electrode sheet includes a negative current collector but does not include a lithium metal layer.

[0026] In a second aspect, this disclosure provides a battery device comprising a plurality of metal battery cells according to the first aspect of this disclosure.

[0027] Thirdly, this disclosure provides an electrical device that includes a metal battery cell according to the first aspect of this disclosure or a battery device according to the second aspect of this disclosure.

[0028] Fourthly, this disclosure provides a method for preparing a metal battery cell, comprising the following steps: providing an electrode assembly and an electrolyte, the electrode assembly including a positive electrode, a negative electrode, and a separator, the separator being located between the positive and negative electrode, the positive electrode including a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer, the lithium salt layer including a first lithium salt, a first conductive agent, and a first binder, the first lithium salt including one or more of lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate, R1 and R2 respectively independently including fluorine atoms or C1-C6 fluoroalkyl groups.

[0029] The electrode assembly is placed in an outer packaging with a receiving cavity, the electrolyte is injected into the receiving cavity, and after sealing and standing, a metal battery cell is obtained.

[0030] Fifthly, this disclosure provides a positive electrode sheet, comprising a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and comprising a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer comprises a first lithium salt, a first conductive agent, and a first binder. The first lithium salt comprises one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R1 and R2 each independently comprise fluorine atoms or C1-C6 fluoroalkyl groups. Attached Figure Description

[0031] 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.

[0032] Figure 1 shows a schematic diagram of a metal battery cell provided in some embodiments of this disclosure.

[0033] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure. Detailed Implementation

[0034] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode sheet, metal battery cell, preparation method thereof, 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 for the purpose of enabling 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 as included in the disclosure 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 disclosure 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 mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0039] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0040] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0041] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0042] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0043] The metal battery cells mentioned in the embodiments of this disclosure can independently perform the functions of charging and discharging. The metal battery cells may be cylindrical, cuboid, or other shapes, and the embodiments of this disclosure are not limited in this respect. Figure 1 shows a cuboid metal battery cell 5 as an example.

[0044] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly may include multiple metal battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0045] In some embodiments, the battery cell assembly is typically formed by arranging multiple metal battery cells.

[0046] As an example, a battery cell assembly can be a battery module, which consists of multiple metal battery cells arranged and fixed together to form a single module. As another example, a battery module can be formed by bundling multiple metal battery cells together with cable ties.

[0047] 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.

[0048] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0049] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple metal battery cells to the housing.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The technical solutions described in this disclosure are applicable to various electrical devices that use metal battery cells or battery devices, including but not limited to mobile devices (such as consumer electronics, mobile phones, tablets, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric aircraft, electric trains, ships and satellites, energy storage systems, etc. Metal battery cells and battery devices are used to store or provide electrical energy.

[0054] 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.

[0055] The metal battery cells provided in the embodiments of this disclosure may include lithium metal battery cells or lithium metal battery cells without a negative electrode.

[0056] A negative electrode-free lithium metal battery cell typically refers to a battery cell in which no negative electrode active material layer is actively formed on the negative electrode side during the battery cell manufacturing process. For example, the negative electrode active material layer is not formed at the negative electrode through coating or deposition processes, or it is formed by a carbonaceous active material layer (such as graphite). During the first charge, lithium ions gain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form lithium metal. During discharge, the lithium metal can be converted back into lithium ions and return to the positive electrode, achieving cyclic charging and discharging. Therefore, a negative electrode-free lithium metal battery cell can be considered a battery cell using a metallic lithium negative electrode. Compared to other battery cells, a negative electrode-free lithium metal battery cell can achieve a higher energy density due to the absence of a negative electrode active material layer. In some embodiments, to improve battery cell performance, conventional materials that can be used as negative electrode active materials, such as carbon materials, can also be placed on the negative electrode side of the negative electrode-free lithium metal battery cell. Although these materials possess a certain capacity, their content is low, and they are not used as the primary negative electrode active material in the battery cell. Therefore, a battery cell constructed in this way can still be considered a negative electrode-free lithium metal battery cell. The CB (Cell Balance) value of a negative electrode-free lithium metal battery cell is typically very small; for example, in some embodiments, the CB value of a negative electrode-free lithium metal battery cell can be less than or equal to 0.1. The CB value is the area capacity per unit area of ​​the negative electrode divided by the area capacity per unit area of ​​the positive electrode in the battery cell. Because a negative electrode-free lithium metal battery cell contains no or only a small amount of negative electrode active material, the area capacity per unit area of ​​the negative electrode is small, and consequently, the CB value is very small, typically less than or equal to 0.1.

[0057] Increasing the electrolyte concentration is one of the effective means to improve the cycle life of lithium metal battery cells. Currently, high-concentration electrolytes (HCE) or locally concentrated high-concentration electrolytes (LHCE) are often used to match lithium metal anodes. This electrolyte can form a relatively dense SEI film at the anode, reducing side reactions at the anode interface. Due to its unique solvation structure, this electrolyte has good redox resistance, thereby improving the coulombic efficiency of the lithium metal battery cell. However, during the charge and discharge process of the lithium metal battery cell, the continuous damage and regeneration of the SEI film mainly consumes lithium salts rather than organic solvents. This leads to a continuous decrease in electrolyte concentration during battery cell cycling, making it difficult to maintain the initial solvation structure. Consequently, the redox resistance of the electrolyte continuously decreases during battery cell cycling, and the cycle life of the lithium metal battery cell still cannot meet higher application requirements. The higher the initial concentration of the electrolyte, the better it is to maintain the solvation structure of the electrolyte. However, the electrolyte concentration is already close to the limit, and it is currently difficult to maintain the solvation structure by further increasing the electrolyte concentration.

[0058] In view of this, the present disclosure provides a metal battery cell and a battery device and a power device containing the same. From the perspective of the positive electrode, the present disclosure enables the metal battery cell and the battery device and power device containing the metal battery cell to have good cycle performance by providing a lithium salt layer on the surface of the positive current collector of the positive electrode.

[0059] The metal battery cell provided in this embodiment includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrode.

[0060] The electrode assembly can be a wound structure or a stacked structure, and the embodiments disclosed herein are not limited to this.

[0061] The number of electrode components contained in a metal battery cell can be one or more, and this disclosure does not limit this.

[0062] Metal battery cells also include an outer packaging for encapsulating the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The flexible package can be made of plastic, such as aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0063] The positive electrode sheet provided in this embodiment includes a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive electrode active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer includes a first lithium salt, a first conductive agent, and a first binder. The first lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiOTF), lithium difluorophosphate (LiDFP), lithium dioxolane borate (LiBOB), lithium difluorooxolane borate (LiDFOB), lithium difluorodioxolane phosphate, and lithium tetrafluorooxolane phosphate. R1 and R2 each independently include fluorine atoms or C1-C6 fluoroalkyl groups.

[0064] As the metal battery cell cycles through charging and discharging, the lithium salt in the electrolyte is continuously consumed. Since the organic solvent is not significantly consumed, the electrolyte concentration decreases continuously. The first lithium salt in the lithium salt layer of the positive electrode can gradually dissolve into the electrolyte to replenish the consumed lithium salt. This allows the electrolyte to maintain a high concentration during the cycle of the metal battery cell, thus maintaining a good solvation structure and high oxidation-reduction resistance, thereby improving the cycle performance of the metal battery cell.

[0065] By placing the first lithium salt in the lithium salt layer, the solvents in the slurry (such as water, N-methylpyrrolidone, etc.) can easily evaporate completely during the preparation process, thereby reducing the impact of residual solvents on the cycle performance of metal battery cells.

[0066] The positive electrode sheet disclosed herein has a simple structure, a simple and easy-to-operate preparation method, good repeatability, low cost, and is suitable for industrial production.

[0067] R1 and R2 each independently include a fluorine atom or a C1-C6 fluoroalkyl group. A C1-C6 fluoroalkyl group means that at least one hydrogen atom in the C1-C6 alkyl group is replaced by a fluorine atom, or all hydrogen atoms can be replaced by fluorine atoms, such as trifluoromethyl, pentafluoroethyl, heptafluoropropyl, etc.

[0068] Optionally, R1 and R2 may each independently include a fluorine atom or a trifluoromethyl group.

[0069] Alternatively, R1 and R2 may both be fluorine atoms.

[0070] In some embodiments, the first lithium salt may include a lithium salt having the structure shown in Formula 1 and at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiOTF), lithium difluorophosphate (LiDFP), lithium dioxolane borate (LiBOB), lithium difluorooxolane borate (LiDFOB), lithium difluorodioxolane phosphate, and lithium tetrafluorooxolane phosphate.

[0071] In some embodiments, the first lithium salt may include a lithium salt having the structure shown in Formula 1.

[0072] Lithium salts with the structure shown in Formula 1 have a wide electrochemical window, high thermal stability and high ionic conductivity, thereby providing less electrolyte high-pressure decomposition and faster ion transport rate.

[0073] Optionally, the first lithium salt may include one or a combination of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0074] Alternatively, the first lithium salt may include lithium bisfluorosulfonylimide (LiFSI).

[0075] FSI - It has better compatibility with lithium metal and can form a better SEI film on the surface of lithium metal, thereby further improving the cycle performance of metal battery cells.

[0076] In some embodiments, the first conductive agent may be one or more of carbon black (such as Super P), acetylene black, Ketjen black, carbon nanotubes, graphene, carbon quantum dots, graphene quantum dots, conductive carbon fibers, conductive graphite, hard carbon, and soft carbon.

[0077] In some embodiments, the first adhesive 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, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polymethacrylic acid (PMAA), lithium polyacrylate (PAA-Li), sodium polyacrylate, polyacrylonitrile (PAN), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0078] In some embodiments, the mass percentage of the first lithium salt in the lithium salt layer can be 40%-98%, for example, it can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, or any range of the above values.

[0079] In some embodiments, the mass percentage of the first conductive agent in the lithium salt layer can be 1%-30%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any range of the above values.

[0080] In some embodiments, the mass percentage of the first binder in the lithium salt layer can be 1%-30%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any range of the above values.

[0081] The first conductive agent imparts good electronic conductivity and low resistance to the lithium salt layer, while the first binder bonds the first lithium salt and the first conductive agent to the positive electrode current collector. When the mass percentage of the first lithium salt is within the aforementioned range, it allows the lithium salt layer to provide more first lithium salt without affecting the positive electrode impedance or increasing positive electrode polarization. This enables the metal battery cell to better maintain the solvation structure of the electrolyte during cycling, maintain high oxidation-reduction resistance of the electrolyte, and ultimately improve the cycle performance of the metal battery cell.

[0082] Optionally, in the lithium salt layer, the mass percentage of the first lithium salt can be 50%-98%, 60%-98%, 70%-98%, 50%-96%, 60%-96%, 70%-96%, 50%-94%, 60%-94%, 70%-94%, 50%-92%, 60%-92%, 70%-92%, 50%-90%, 60%-90%, or 70%-90%.

[0083] Optionally, in the lithium salt layer, the mass percentage of the first conductive agent can be 1%-25%, 1%-20%, 1%-15%, 2%-25%, 2%-20%, 2%-15%, 3%-25%, 3%-20%, 3%-15%, 4%-25%, 4%-20%, 4%-15%, 5%-25%, 5%-20%, or 5%-15%.

[0084] Optionally, in the lithium salt layer, the mass percentage of the first binder can be 1%-25%, 1%-20%, 1%-15%, 2%-25%, 2%-20%, 2%-15%, 3%-25%, 3%-20%, 3%-15%, 4%-25%, 4%-20%, 4%-15%, 5%-25%, 5%-20%, or 5%-15%.

[0085] The mass ratio of the first lithium salt, the first conductive agent, and the first binder in the lithium salt layer can be tested as follows: The positive electrode sheet is disassembled from the metal battery cell, the positive electrode film layer is wiped away, exposing the positive current collector with the lithium salt layer; then, the positive current collector is soaked in a known mass of dimethyl ethylene glycol (DME) for a period of time, the positive current collector is removed, and the mass of DME is weighed again. The difference between the two weighings is the mass of the first lithium salt, and the mass ratio of the first lithium salt is calculated; the removed positive current collector is baked at a certain temperature and time (e.g., 400℃ for more than 2 hours) to separate the first conductive agent and the first binder in the lithium salt layer, and the mass ratio of the first conductive agent and the first binder is calculated.

[0086] In the above tests, the metal battery cell refers to a fresh metal battery cell, such as a factory-issued metal battery cell or a metal battery cell assembled in an electrical device with fewer than 10 cycles. When the number of cycles for a metal battery cell is high, a large amount of the first lithium salt in the lithium salt layer of the positive electrode may have dissolved out, which will lead to a significant deviation in the test results.

[0087] In some embodiments, the thickness of the lithium salt layer can be 1μm-20μm, for example, it can be 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or any range of the above values.

[0088] Within the aforementioned thickness range, the lithium salt layer can provide more first lithium salt without affecting the positive electrode impedance or increasing positive electrode polarization. This allows the electrolyte to better maintain its solvation structure during battery cell cycling, ensuring high oxidation-reduction resistance and ultimately improving the battery cell's cycle performance. Furthermore, as the first lithium salt is consumed, the first conductive agent and first binder deform under clamping forces, continuously thinning the lithium salt layer. Therefore, maintaining the lithium salt layer thickness within the aforementioned range can also mitigate, to some extent, the irreversible volume expansion caused by the accumulation of electrolyte decomposition products during battery cell cycling.

[0089] Optionally, the thickness of the lithium salt layer can be 2μm-20μm, 3μm-20μm, 4μm-20μm, or 5μm-20μm.

[0090] In some embodiments, the compaction density of the lithium salt layer can be 2 g / cm³. 3 -5g / cm 3 For example, it can be 2g / cm 3 2.2g / cm 3 2.4g / cm 3 2.6g / cm 3 2.8g / cm 3 3g / cm 3 3.2g / cm 3 3.4g / cm 3 3.6g / cm 3 3.8g / cm 3 4g / cm 3 4.2g / cm 3 4.4g / cm 3 4.6g / cm 3 4.8g / cm 3 5g / cm 3 or a range consisting of any of the above values.

[0091] The compaction density of the lithium salt layer is within the above range, which is beneficial to the subsequent coating of the positive electrode slurry, to improving the coating quality of the positive electrode film, and also to improving the cycle performance of the metal battery cell.

[0092] The positive electrode 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 electrode current collector.

[0093] The positive electrode film layer includes a positive electrode active material, which in some embodiments may include one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds.

[0094] 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 their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures.

[0095] Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and one or more of their respective modified compounds.

[0096] In some embodiments, to further improve the energy density of a metal battery cell, the positive electrode active material may include materials with the general formula Li. a Ni b Co c M d O e D f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0097] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2 O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.96 Co 0.02 Mn 0.02O2(Ni96), LiNi 0.80 Co 0.15 Al 0.05 One or more of O2 and LiFePO4.

[0098] During the charging and discharging process of a metal battery cell, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the embodiments described in this disclosure regarding the positive electrode active material, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to a metal battery cell, the molar Li content may change after charge-discharge cycles.

[0099] In the examples of positive electrode active materials disclosed in this disclosure, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0100] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0101] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments, the positive electrode film layer may further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0103] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0104] In some embodiments, the method for preparing the positive electrode sheet may include the following steps: stirring a first lithium salt, a first conductive agent, a first binder, and a first solvent to obtain a slurry, wherein the solvent may be water or N-methylpyrrolidone (NMP), but is not limited thereto; coating the slurry onto the surface of the positive electrode current collector, and drying and cold pressing to obtain a positive electrode current collector having a lithium salt layer; coating the slurry including the positive electrode active material onto the lithium salt layer, and drying and cold pressing to obtain the positive electrode sheet.

[0105] The method for preparing the positive electrode sheet disclosed herein is simple, easy to operate, highly reproducible, low in cost, and suitable for industrial production.

[0106] Electrolyte

[0107] In some embodiments, the electrolyte includes a second lithium salt, an organic solvent, and a diluent.

[0108] The second lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 2, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiOTF), lithium difluorophosphate (LiDFP), lithium dioxolane borate (LiBOB), lithium difluorooxolane borate (LiDFOB), lithium difluorodioxolane phosphate, and lithium tetrafluorooxolane phosphate, wherein R3 and R4 each independently include a fluorine atom or a C1-C6 fluoroalkyl group.

[0109] R3 and R4 each independently include a fluorine atom or a C1-C6 fluoroalkyl group. A C1-C6 fluoroalkyl group means that at least one hydrogen atom in the C1-C6 alkyl group is replaced by a fluorine atom, or all hydrogen atoms can be replaced by fluorine atoms, such as trifluoromethyl, pentafluoroethyl, heptafluoropropyl, etc.

[0110] Alternatively, R3 and R4 may each independently include a fluorine atom or a trifluoromethyl group.

[0111] Alternatively, R3 and R4 may both be fluorine atoms.

[0112] In some embodiments, the second lithium salt may include a lithium salt having the structure shown in Formula 2 and at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiOTF), lithium difluorophosphate (LiDFP), lithium dioxolane borate (LiBOB), lithium difluorooxolane borate (LiDFOB), lithium difluorodioxolane phosphate, and lithium tetrafluorooxolane phosphate.

[0113] In some embodiments, the second lithium salt may include a lithium salt having the structure shown in Formula 2.

[0114] Lithium salts with the structure shown in Formula 2 have a wide electrochemical window, high thermal stability and high ionic conductivity, thereby providing less electrolyte high-pressure decomposition and faster ion transport rate.

[0115] Optionally, the second lithium salt may include one or a combination of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0116] Alternatively, the second lithium salt may include lithium bisfluorosulfonylimide (LiFSI).

[0117] FSI - It has better compatibility with lithium metal and can form a better SEI film on the surface of lithium metal, thereby further improving the cycle performance of metal battery cells.

[0118] In some embodiments, the sum of the mass of the first lithium salt in the lithium salt layer and the mass of the second lithium salt in the electrolyte is greater than the saturated solubility in the organic solvent and diluent.

[0119] That is, when all the first lithium salt in the lithium salt layer is added to the electrolyte, lithium salt will precipitate out.

[0120] By ensuring that the sum of the mass of the first lithium salt in the lithium salt layer and the mass of the second lithium salt in the electrolyte exceeds the saturated solubility in organic solvents and diluents, the second lithium salt in the electrolyte is continuously consumed during the cycling process of the metal battery cell. The first lithium salt in the lithium salt layer of the positive electrode can gradually dissolve into the electrolyte under the wetting effect of the electrolyte to replenish the consumption of the second lithium salt. This allows the electrolyte to maintain a high concentration during the cycling process of the metal battery cell, thereby maintaining a good solvation structure and high oxidation-reduction resistance of the electrolyte, ultimately resulting in better cycle performance of the metal battery cell.

[0121] In some embodiments, the electrolyte is a locally high-concentration electrolyte. A locally high-concentration electrolyte is a high-concentration electrolyte with the addition of a diluent that is miscible with organic solvents but does not dissolve lithium salts or has extremely poor lithium salt dissolving ability. The addition of the diluent does not affect the unique solvation structure of the high-concentration electrolyte and can improve the viscosity and ionic conductivity of the electrolyte, thereby improving the electrolyte wettability of the electrode components. It also facilitates better dissolution of the first lithium salt into the electrolyte during charge-discharge cycles to replenish the consumption of the second lithium salt, thus better improving the cycle performance of the metal battery cell.

[0122] In some embodiments, the molar ratio of the second lithium salt, organic solvent, and diluent in the electrolyte can be 1:(0.8-3):(0.5-5).

[0123] This results in a locally high-concentration electrolyte, which gives the electrolyte a good solvation structure, good resistance to oxidation and reduction, and consequently, good cycle performance of the metal battery cells.

[0124] The molar ratio of the second lithium salt to the organic solvent can be 1:(0.8-3), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, or any range of the above values. Optionally, the molar ratio of the second lithium salt to the organic solvent can be 1:(0.9-2).

[0125] The molar ratio of the second lithium salt to the diluent can be 1:(0.5-5), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.3, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or any range of the above values.

[0126] In some embodiments, the organic solvent includes ether compounds. This is because ether compounds are more compatible with lithium metal anodes.

[0127] Optionally, the organic solvent may include one or more of the following: methyl n-butyl ether (MBE), tetrahydrofuran (THF), dimethyl ethylene glycol (DME), tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether (DEE), 1,2-dimethoxypropane (DMP1), 1,3-dimethoxypropane (DMP2), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0128] In some embodiments, the diluent may include one or more of fluoroether diluents, aromatic diluents, and fluoroaromatic diluents.

[0129] Optionally, the diluent may include, but is not limited to, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl (TFE), 1-(1,1,2,2-tetrafluoroethoxy)propane (TFEPE), 1,1,2,2-tetrafluoroethyl ether (ETE), bis(2,2,2-trifluoroethyl) ether (BTFE), difluoromethyl 2,2,3,3-tetrafluoropropyl ether, heptafluoropropyl 1, One or more of the following: 2,2,2-tetrafluoroethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ester, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,3,3,3-pentafluoropropyl difluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, benzene (BZ), 3-fluorobenzene, m-difluorobenzene, 1,3,5-trifluorobenzene, and anisole.

[0130] In some embodiments, the viscosity of the electrolyte at 25°C can be 2 mPa·s-50 mPa·s, optionally 3 mPa·s-15 mPa·s. This contributes to the long cycle life of the metal battery cell.

[0131] The viscosity of the electrolyte can be tested using a viscometer. When the rotor rotates continuously at a constant speed in the sample, the shear force it experiences causes the spring to generate torque. The torque is proportional to the viscosity, thus yielding the viscosity value of the sample.

[0132] For example, the viscosity of the electrolyte can be tested as follows: Under ambient humidity <80%, take a 30mL sample and keep it at a constant temperature of 25℃ in a water bath for at least 30 minutes. Place the rotor (e.g., a No. 18 rotor) into the sample cup, add the sample to about 0.3cm from the rim, start the connected viscometer, select a speed of 70RPM and rotate for 5 minutes to obtain the viscosity value. Ten data points can be collected during the test, and the average value is taken. The testing instrument can be a Bollerfeld DV-2TLV viscometer.

[0133] In some embodiments, the conductivity of the electrolyte at 25°C can be 1 mS / cm-15 mS / cm, and can be selected as 2 mS / cm-8 mS / cm.

[0134] The conductivity of the electrolyte can be obtained by testing with a conductivity meter. For example, a suitable amount of electrolyte can be taken, divided into three equal portions, and then the conductivity of each sample can be measured using a conductivity meter at 25°C. The average of the test results is then taken as the conductivity of the electrolyte. A DDS-307 conductivity meter can be used as the testing instrument.

[0135] The electrolyte can be prepared using methods known in the art.

[0136] [Negative electrode plate]

[0137] In some embodiments, the negative electrode includes a negative current collector and a lithium metal layer located on at least one side of the negative current collector, thereby enabling the assembly of a lithium metal battery cell. The lithium metal layer includes elemental lithium or an alloy of lithium metal with other metallic and / or non-metallic elements. Other metallic elements may include one or more of Sn, Zn, Al, Mg, Ag, Au, Ga, In, and Pt. Non-metallic elements may include one or more of B, C, and Si. Optionally, the total mass percentage of other metallic and / or non-metallic elements in the lithium metal layer may be less than or equal to 5%, preferably less than or equal to 3%.

[0138] In some embodiments, the negative electrode may include a negative current collector but not a lithium metal layer, thereby enabling the assembly of a negative electrode-free lithium metal battery cell. Optionally, the surface of the negative current collector of the negative electrode-free lithium metal battery cell may also be provided with an interface modification layer that can improve lithium metal deposition behavior.

[0139] In some embodiments, the negative electrode current collector may include 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, and nickel alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, copper foam, and nickel foam. The composite current collector may 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, 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 (PS), and polyethylene.

[0140] [Isolation membrane]

[0141] The separator is located between the positive and negative electrodes and primarily serves to prevent internal short circuits. This disclosure does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0142] In some embodiments, the material of the separator may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, polyimide, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0143] The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. Inorganic particle coatings, organic particle coatings, or organic / inorganic composite coatings can also be applied to the surface of the separator.

[0144] This disclosure also provides a method for preparing a metal battery cell, which can prepare the metal battery cell provided in this disclosure.

[0145] The preparation method of a metal battery cell includes the following steps: providing an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The positive electrode includes a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer includes a first lithium salt, a first conductive agent, and a first binder. The first lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiOTF), lithium difluorophosphate (LiDFP), lithium dioxolaneborate (LiBOB), lithium difluorooxolaneborate (LiDFOB), lithium difluorodioxolane phosphate, and lithium tetrafluorooxolane phosphate. R1 and R2 each independently include fluorine atoms or C1-C6 fluoroalkyl groups.

[0146] The electrode assembly is placed in an outer packaging with a receiving cavity, the electrolyte is injected into the receiving cavity, and after sealing and standing, a metal battery cell is obtained.

[0147] Optionally, the positive electrode, separator, and negative electrode can be fabricated into an electrode assembly through a winding process and / or a stacking process.

[0148] Example

[0149] The following embodiments describe the contents of this disclosure in more detail. These embodiments 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 embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0150] Example 1

[0151] (1) Preparation of positive electrode sheet

[0152] A slurry was prepared by mixing acetylene black (first conductive agent), polyvinylidene fluoride (PVDF) (first binder), and lithium bis(fluorosulfonyl)imide (LiFSI) (first lithium salt) in a mass ratio of 10:10:80 with N-methylpyrrolidone (NMP) solvent. The slurry was then transferred onto both surfaces of a positive electrode current collector aluminum foil. After drying and cold pressing, a positive electrode current collector with a lithium salt layer was obtained. The lithium salt layer had a thickness of 5 μm and a compaction density of 3 g / cm³. 3 .

[0153] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, acetylene black (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) were mixed in a mass ratio of 98:1:1. N-methylpyrrolidone (N-methylpyrrolidone) was added as solvent and stirred until homogeneous, yielding a positive electrode slurry with a solid content of approximately 70%. The positive electrode slurry was then subjected to a reaction at approximately 12.5 mg / cm³. 2 The coating weight is applied to the lithium salt layer, and after drying at room temperature, it is transferred to an oven for further drying. Then, it is cold-pressed and cut into rectangles of 40mm×50mm for later use.

[0154] (2) Preparation of negative electrode sheet

[0155] A 50μm lithium foil is rolled onto a 12μm copper foil surface to serve as the negative electrode. The negative electrode is then cut into a 41mm×51mm rectangle for later use.

[0156] (3) Preparation of electrolyte

[0157] The organic solvent ethylene glycol dimethyl ether (DME) and the diluent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) were mixed at a mass ratio of 1:7 to obtain a mother liquor. 2g of the second lithium salt, lithium bis(fluorosulfonyl)imide (LiFSI), was added to 8g of the prepared mother liquor and stirred thoroughly to form a colorless and transparent electrolyte.

[0158] (4) Preparation of the separating membrane

[0159] Polyethylene porous membrane was selected as the separator and cut into rectangles of 45mm×55mm for later use.

[0160] (5) Preparation of lithium metal battery cells

[0161] Take one cut positive electrode sheet and two cut negative electrode sheets, separate them with a separator, and wrap them in an aluminum-plastic film bag to form a stacked electrode assembly; inject electrolyte, vacuum heat-press the aluminum-plastic film bag, and let it stand at room temperature for at least 6 hours before capacity and cycle performance testing can begin.

[0162] The capacity of a single lithium metal battery cell can be tested as follows: At 25°C, allow the lithium metal battery cell to stand for 5 minutes, then discharge it at a constant current of 0.1C to 2.8V; after standing for 5 minutes, charge it at a constant current of 0.1C to 4.3V, then charge it at a constant voltage of 4.3V to a current of 0.1C; after standing for 5 minutes, discharge it at a constant current of 0.1C to 2.8V. Record the discharge capacity at this point; this is the capacity of the single lithium metal battery cell. The capacity of the single lithium metal battery cell is 70mAh.

[0163] The ambient temperature was set to 25℃. The lithium metal battery cell was charged at a constant current of 0.2C (i.e., 14mA) to 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.1C (i.e., 7mA). After standing for 5 minutes, the lithium metal battery cell was discharged at a constant current of 1C (i.e., 70mA) to 2.8V to obtain the first discharge capacity. The same charge and discharge cycle was performed. When the discharge capacity after the cycle decayed to 80% of the first discharge capacity, the life of the lithium metal battery cell was considered to have ended, and the number of cycles was recorded.

[0164] Examples 2 to 11

[0165] The preparation method and cycle performance testing method of the lithium metal battery cell are the same as those in Example 1. The difference is that the types of the first conductive agent, the first binder or the first lithium salt in the lithium salt layer of the positive electrode are different. For specific parameters, please refer to Table 1.

[0166] In Table 1, SBR is styrene-butadiene rubber, PAA is polyacrylic acid, PAA-Li is lithium polyacrylate, PAN is polyacrylonitrile, LiTFSI is lithium bis(trifluoromethanesulfonyl)imide, LiOTF is lithium trifluoromethanesulfonate, and LiPF6 is lithium hexafluorophosphate.

[0167] Comparative Example 1

[0168] The preparation method and cycle performance testing method of the lithium metal battery cell are the same as those in Example 1, except that the prepared positive electrode does not contain a lithium salt layer.

[0169] Comparative Example 2

[0170] Except for the following differences, the preparation method of the lithium metal battery cell and the test method of its cycle performance are the same as those in Example 1.

[0171] (1) Preparation of positive electrode sheet

[0172] Acetylene black (the first conductive agent) and polyvinylidene fluoride (PVDF) (the first binder) were added to N-methylpyrrolidone (NMP) solvent at a mass ratio of 50:50 and stirred until homogeneous to obtain a slurry. The slurry was then transferred onto both surfaces of the positive electrode current collector aluminum foil, and dried and cold-pressed to obtain a positive electrode current collector with a conductive layer. The conductive layer had a thickness of 5 μm and a compaction density of 3 g / cm³. 3 .

[0173] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, acetylene black (positive electrode conductive agent), and polyvinylidene fluoride (PVDF) (positive electrode binder) were mixed in a mass ratio of 98:1:1. N-methylpyrrolidone (N-methylpyrrolidone) was added as solvent and stirred until homogeneous, yielding a positive electrode slurry with a solid content of approximately 70%. The positive electrode slurry was then subjected to a reaction at approximately 12.5 mg / cm³. 2 The coating weight is applied to the conductive layer, and after drying at room temperature, it is transferred to an oven for further drying. Then, it is cold-pressed and cut into 40mm×50mm rectangles for later use.

[0174] Table 1

[0175] As can be seen from the test results of Examples 1 to 11 and Comparative Examples 1 to 2, this disclosure provides a lithium salt layer between the positive electrode film layer and the positive electrode current collector. The first lithium salt in the lithium salt layer can gradually dissolve into the electrolyte to replenish the consumption of the second lithium salt. This allows the electrolyte to maintain a high concentration during the cycling process of the lithium metal battery cell, thereby maintaining a good solvation structure during the cycling process of the lithium metal battery cell and maintaining high oxidation-reduction resistance of the electrolyte, which in turn improves the cycling performance of the lithium metal battery cell.

[0176] The test results from Examples 1 and 9 to 11 show that using LiFSI as the first lithium salt in the lithium salt layer can improve the cycle performance of lithium metal battery cells. This is because FSI... - It has better compatibility with lithium metal and can form a better SEI film on the lithium metal surface.

[0177] Examples 1-1 to Examples 1-4

[0178] The preparation method and cycle performance testing method of the lithium metal battery cell are the same as those in Example 1. The difference is that the mass ratio of each component in the lithium salt layer of the positive electrode is different. For specific parameters, please refer to Table 2.

[0179] Table 2

[0180] The test results above show that further adjusting the mass ratio of the first lithium salt can further improve the cycle performance of lithium metal battery cells.

[0181] Examples 2-1 to 2-5

[0182] The preparation method and cycle performance testing method of the lithium metal battery cell are the same as those in Example 1. The difference is that the thickness of the lithium salt layer of the positive electrode is different. For specific parameters, please refer to Table 3.

[0183] Table 3

[0184] The test results above show that further adjusting the thickness of the lithium salt layer can further improve the cycle performance of lithium metal battery cells.

[0185] Examples 3-1 to 3-2

[0186] The preparation method and cycle performance testing method of the lithium metal battery cell are the same as those in Example 1. The difference is that the compaction density of the lithium salt layer of the positive electrode is different. For specific parameters, please refer to Table 4.

[0187] Table 4

[0188] The test results above show that cold pressing can make the surface of the lithium salt layer smoother, which is beneficial for the subsequent coating of the positive electrode slurry and also helps to improve the cycle performance of lithium metal battery cells.

[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 essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in 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 in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A metal battery cell, comprising an electrode assembly and an electrolyte, wherein the electrode assembly includes a positive electrode, a negative electrode, and a separator, the separator being located between the positive electrode and the negative electrode, wherein, The positive electrode includes a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer includes a first lithium salt, a first conductive agent, and a first binder. The first lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R1 and R2 each independently include fluorine atoms or C1-C6 fluoroalkyl groups.

2. The metal battery cell according to claim 1, wherein, The first lithium salt includes a lithium salt having the structure shown in Formula 1.

3. The metal battery cell according to any one of claims 1-2, wherein, R1 and R2 each independently include a fluorine atom or a trifluoromethyl group.

4. The metal battery cell according to any one of claims 1-3, wherein, In the lithium salt layer, the mass percentage of the first lithium salt is 40%-98%; In the lithium salt layer, the mass percentage of the first conductive agent is 1%-30%; In the lithium salt layer, the first binder accounts for 1%-30% by mass.

5. The metal battery cell according to claim 4, wherein, In the lithium salt layer, the mass percentage of the first lithium salt is 70%-90%; In the lithium salt layer, the mass percentage of the first conductive agent is 5%-15%; In the lithium salt layer, the first binder accounts for 5%-15% of the mass.

6. The metal battery cell according to any one of claims 1-5, wherein, The thickness of the lithium salt layer is 1μm-20μm.

7. The metal battery cell according to any one of claims 1-6, wherein, The compaction density of the lithium salt layer is 2 g / cm³. 3 -5g / cm 3 .

8. The metal battery cell according to any one of claims 1-7, wherein, The electrolyte comprises a second lithium salt, an organic solvent, and a diluent. The second lithium salt comprises one or more of the following: lithium salt having the structure shown in Formula 2, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R3 and R4 each independently comprise a fluorine atom or a C1-C6 fluoroalkyl group.

9. The metal battery cell according to claim 8, wherein, The second lithium salt includes a lithium salt having the structure shown in Formula 2.

10. The metal battery cell according to any one of claims 8-9, wherein, R3 and R4 each independently include a fluorine atom or a trifluoromethyl group.

11. The metal battery cell according to any one of claims 8-10, wherein, In the electrolyte, the molar ratio of the second lithium salt, the organic solvent, and the diluent is 1:(0.8-3):(0.5-5).

12. The metal battery cell according to any one of claims 8-11, wherein, The organic solvent includes ether compounds; and / or, The diluent includes one or more of fluoroether diluents, aromatic diluents, and fluorinated aromatic diluents.

13. The metal battery cell according to claim 12, wherein, The organic solvent includes one or more of methyl n-butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,2-dimethoxypropane, 1,3-dimethoxypropane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; and / or, The diluent includes 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl, 1-(1,1,2,2-tetrafluoroethoxy)propane, 1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, heptafluoropropyl 1,2,2,2-tetrafluoroethyl ether, 2,2,3 One or more of the following: 3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ester, bis-(1,2,2,2-tetrafluoroethyl) ether, 1,1,2,3,3,3-pentafluoropropyl difluoromethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, benzene, 3-fluorobenzene, m-difluorobenzene, 1,3,5-trifluorobenzene, and anisole.

14. The metal battery cell according to any one of claims 8-13, wherein, The sum of the mass of the first lithium salt in the lithium salt layer and the mass of the second lithium salt in the electrolyte is greater than the saturated solubility in the organic solvent and the diluent.

15. The metal battery cell according to any one of claims 1-14, wherein, The positive electrode active material includes one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds; and / or, The negative electrode sheet includes a negative current collector and a lithium metal layer located on at least one side of the negative current collector. The lithium metal layer includes elemental lithium metal or an alloy formed by lithium metal and other metal elements and / or non-metal elements. Alternatively, the negative electrode sheet includes a negative current collector but does not include a lithium metal layer.

16. A battery device comprising a plurality of metal battery cells as described in any one of claims 1-15.

17. An electrical device comprising a metal battery cell as described in any one of claims 1-15 or a battery device as described in claim 16.

18. A method for preparing a metal battery cell, comprising the following steps: An electrode assembly and an electrolyte are provided. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The positive electrode includes a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer includes a first lithium salt, a first conductive agent, and a first binder. The first lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R1 and R2 each independently include fluorine atoms or C1-C6 fluoroalkyl groups. The electrode assembly is placed in an outer packaging with a receiving cavity, the electrolyte is injected into the receiving cavity, and after sealing and standing, a metal battery cell is obtained.

19. A positive electrode plate, wherein, The positive electrode includes a positive current collector, a positive electrode film layer located on at least one side of the positive current collector and including a positive active material, and a lithium salt layer located between the positive current collector and the positive electrode film layer. The lithium salt layer includes a first lithium salt, a first conductive agent, and a first binder. The first lithium salt includes one or more of the following: lithium salt having the structure shown in Formula 1, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. R1 and R2 each independently include fluorine atoms or C1-C6 fluoroalkyl groups.

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