Metal battery cell, battery apparatus, and electric apparatus

Abstract

A metal battery cell, a battery apparatus, and an electric apparatus. The metal battery cell comprises an electrode assembly and an electrolyte, wherein the electrode assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator, and the separator is located between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material and a first lithium salt; the electrolyte comprises a second lithium salt, an organic solvent, and a diluent; a ratio of a mass of the electrolyte to a capacity of the metal battery cell is 1.1 g / Ah to 1.6 g / Ah; and a charge-discharge cycling temperature of the metal battery cell is 30° C to 80° C. The metal battery cell has both high energy density and good cycling performance.

Description

Metal battery cells, battery devices and electrical appliances

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese patent application 202510191624.4, filed on February 20, 2025, entitled “Metal Battery Cell, Battery Device and Power Consumption Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a metal battery cell, 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 requirements of future high-range electric vehicles and electric aircraft, it is necessary to develop metal battery cells using lithium metal anodes. Lithium metal has 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 very 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. In addition, to further improve the energy density of metal battery cells, a feasible strategy is to reduce the mass of the electrolyte. However, reducing the mass of the electrolyte will affect the cycle life of the metal battery cells. How to improve the energy density of metal battery cells while giving them better cycle performance is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] This disclosure provides a metal battery cell, a battery device, and an electrical device, wherein the metal battery cell has both high energy density and 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, with the separator located between the positive and negative electrode.

[0007] The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material and a first lithium salt. 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.

[0008] 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.

[0009] The ratio of electrolyte mass to the capacity of the metal battery cell is 1.1 g / Ah-1.6 g / Ah; the cycle charge / discharge temperature of the metal battery cell is 30℃-80℃.

[0010] The metal battery cell disclosed herein satisfies that the ratio of electrolyte mass to metal battery cell capacity is less than or equal to 1.6 g / Ah, thereby enabling the metal battery cell to possess high energy density. Simultaneously, the metal battery cell of this disclosure also satisfies that the ratio of electrolyte mass to metal battery cell capacity is greater than or equal to 1.1 g / Ah, thereby ensuring sufficient electrolyte wetting of the electrode assembly. Because the ratio of electrolyte mass to metal battery cell capacity is relatively small, the second lithium salt in the electrolyte is continuously consumed during the cyclic charging and discharging of the metal battery cell. Since the organic solvent is not significantly consumed, the electrolyte concentration continuously decreases. By pre-setting the first lithium salt in the positive electrode film layer, during cyclic charging and discharging, the first lithium salt can gradually dissolve into the electrolyte to dynamically 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, thus maintaining a good solvation structure during the cycling process, ensuring high oxidation-reduction resistance of the electrolyte, and ultimately improving the cycle performance of the metal battery cell. This disclosure improves the electrolyte wettability of the positive electrode when the ratio of electrolyte mass to the capacity of the metal battery cell is low by setting the cycle charge / discharge temperature of the metal battery cell to 30℃-80℃. This reduces the polarization problem of the metal battery cell, thereby enabling the metal battery cell to have high energy density and long cycle life. Therefore, this disclosure enables the metal battery cell to possess both high energy density and good cycle performance by adjusting the composition of the positive electrode film, the electrolyte composition, the electrolyte dosage, and the cycle charge / discharge temperature.

[0011] In some embodiments, the ratio of electrolyte mass to the capacity of the metal battery cell is 1.2 g / Ah to 1.4 g / Ah. This allows the metal battery cell to better combine high energy density and good cycle performance.

[0012] In some embodiments, the cycle charge / discharge temperature of the metal battery cell is 45°C-65°C. This allows the metal battery cell to have better cycle performance.

[0013] In some embodiments, the sum of the mass of the first lithium salt in the positive electrode film 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, and the first lithium salt in the positive electrode film can gradually dissolve into the electrolyte under the wetting effect of the electrolyte to dynamically 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, ensuring high oxidation-reduction resistance of the electrolyte, and ultimately enabling the metal battery cell to have better cycle performance.

[0014] In some embodiments, the mass percentage of the first lithium salt in the positive electrode film is 0.5%-10%, optionally 1%-5%. Within this range, the first lithium salt provides more of the first lithium salt to better dynamically replenish the consumption of the second lithium salt without affecting the positive electrode impedance or increasing positive electrode polarization. This allows the metal battery cell to better maintain the solvation structure of the electrolyte during cycling, maintain high oxidation-reduction resistance, and thus improve the cycle performance of the metal battery cell. Furthermore, as the first lithium salt gradually dissolves from the positive electrode film, the porosity of the film increases. This increases the spacing between the positive electrode active material particles, lengthens ion and electron transport paths, and affects the charge-discharge performance of the metal battery cell. Setting the mass percentage of the first lithium salt within the above range also helps the positive electrode film maintain high ion and electron transport capabilities during charge-discharge cycles, further contributing to better cycle performance of the metal battery cell.

[0015] In some embodiments, the porosity of the positive electrode film is 15%-30%, optionally 15%-25%. By setting the porosity of the positive electrode film within the above range, it is beneficial for the electrolyte to wet the positive electrode film and for the positive electrode film to maintain a high ion transport capacity and electron transport capacity during cyclic charging and discharging, thereby contributing to better cycle performance of the metal battery cell.

[0016] In some embodiments, the positive electrode film layer includes a positive electrode conductive agent, and the mass percentage of the positive electrode conductive agent in the positive electrode film layer is 0.8%-3%.

[0017] In some embodiments, the positive electrode film layer includes a positive electrode conductive agent, which includes one or more of carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0018] 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.

[0019] In some embodiments, R1 and R2 each independently include a fluorine atom or a trifluoromethyl group.

[0020] 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.

[0021] In some embodiments, R3 and R4 independently include a fluorine atom or a trifluoromethyl group.

[0022] In some embodiments, the molar ratio of the second lithium salt, organic solvent, and diluent in the electrolyte is 1:(1-2):(1-3). This forms a locally high-concentration electrolyte, which can give the electrolyte a good solvation structure and good resistance to oxidation and reduction, thereby giving the metal battery cell good cycle performance. It can also give the electrolyte both high ionic conductivity and low viscosity, which is beneficial to improving the electrolyte wettability of the electrode assembly. It also facilitates the better dissolution of the first lithium salt in the positive electrode film into the electrolyte during cyclic charging and discharging to dynamically replenish the consumption of the second lithium salt, thereby better improving the cycle performance of the metal battery cell.

[0023] 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.

[0024] In some embodiments, the diluent includes one or more of fluoroether diluents, aromatic diluents, and fluoroaromatic diluents.

[0025] 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.

[0026] In some embodiments, the positive electrode active material includes one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds.

[0027] 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.

[0028] Secondly, this disclosure provides a battery device comprising a plurality of metal battery cells according to the first aspect of this disclosure.

[0029] 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. Attached Figure Description

[0030] 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.

[0031] Figure 1 shows a schematic diagram of a metal battery cell provided in some embodiments of this disclosure.

[0032] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure. Detailed Implementation

[0033] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the metal 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

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

[0040] 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.

[0041] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0042] 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.

[0043] 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.

[0044] In some embodiments, the battery cell assembly is typically formed by arranging multiple metal battery cells.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple metal battery cells to the housing.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The metal battery cells provided in the embodiments of this disclosure may include lithium metal battery cells or negative electrode-free lithium metal battery cells.

[0055] 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.

[0056] High energy density and long cycle life are common goals for lithium metal battery cells. Increasing 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 resistance to redox reactions, thereby improving the coulombic efficiency of the lithium metal battery cell.

[0057] However, during the charging and discharging process of the metal battery cell, the SEI film undergoes continuous damage and regeneration, primarily consuming lithium salt rather than organic solvent. This leads to a continuous decrease in electrolyte concentration during the metal battery cell cycle, making it difficult to maintain the initial solvation structure. Consequently, the electrolyte's oxidation-reduction resistance decreases during the cycle, and the cycle life of the metal battery cell still cannot meet higher usage requirements. A higher initial electrolyte concentration is more conducive to maintaining the solvation structure; however, the electrolyte concentration is already close to its limit, and it is currently difficult to maintain the solvation structure by further increasing the electrolyte concentration.

[0058] Furthermore, since the SEI film's continuous damage and regeneration during the charging and discharging of a metal battery cell primarily consumes lithium salt rather than organic solvents, achieving a long cycle life for metal battery cells often requires a higher electrolyte dosage (e.g., the ratio of electrolyte mass to metal battery cell capacity is typically greater than or equal to 2 g / Ah). This significantly sacrifices the energy density of the metal battery cell. While reducing the electrolyte mass-to-metal battery cell capacity ratio can increase the energy density, insufficient lithium salt is available for SEI film regeneration and repair during charging and discharging, thus affecting the cycle life of the metal battery cell.

[0059] In view of this, the present disclosure provides a metal battery cell and a battery device and an electrical device comprising the same, which can achieve both high energy density and good cycle performance by adjusting the composition of the positive electrode film, the composition of the electrolyte, the amount of electrolyte, and the cyclic charge and discharge temperature.

[0060] 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.

[0061] The electrode assembly can be a wound structure or a stacked structure, and the embodiments disclosed herein are not limited to this.

[0062] The number of electrode components contained in a metal battery cell can be one or more, and this disclosure does not limit this.

[0063] 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).

[0064] The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material and a first lithium salt. 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.

[0065] 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 (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. R3 and R4 each independently comprise a fluorine atom or a C1-C6 fluoroalkyl group.

[0066] The ratio of electrolyte mass to the capacity of the metal battery cell is 1.1 g / Ah-1.6 g / Ah; the cycle charge / discharge temperature of the metal battery cell is 30℃-80℃.

[0067] The metal battery cell disclosed herein satisfies the requirement that the ratio of electrolyte mass to the capacity of the metal battery cell is less than or equal to 1.6 g / Ah, thereby enabling the metal battery cell to possess high energy density. Simultaneously, the metal battery cell of this disclosure also satisfies the requirement that the ratio of electrolyte mass to the capacity of the metal battery cell is greater than or equal to 1.1 g / Ah, thereby ensuring sufficient electrolyte wetting of the electrode assembly. When the ratio of electrolyte mass to the capacity of the metal battery cell is less than 1.1 g / Ah, the wetting effect of the electrode assembly is poor, the ion transport path is long, and the unwetted portions of the electrode cannot participate in the electrochemical reaction, thus affecting the energy density and cycle performance of the metal battery cell.

[0068] Because the ratio of electrolyte mass to the capacity of a single metal battery cell is relatively small, the second lithium salt in the electrolyte is continuously consumed as the metal battery cell cycles through charge and discharge. Since the organic solvent is not significantly consumed, the electrolyte concentration continuously decreases. By pre-setting the first lithium salt in the positive electrode film, the first lithium salt can gradually dissolve into the electrolyte during the cycle to dynamically replenish the consumption of the second 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 of the electrolyte, thereby improving the cycle performance of the metal battery cell.

[0069] Furthermore, due to the relatively small ratio of electrolyte mass to the capacity of the metal battery cell, the electrolyte wettability of the positive electrode is poor (compared to a larger ratio, such as ≥2 g / Ah). In this case, pre-setting the first lithium salt in the positive electrode film makes the metal battery cell more prone to polarization. Polarization reduces the actual operating voltage of the metal battery cell and increases the positive electrode impedance, hindering lithium-ion ion transport during charge and discharge, reducing the reversible capacity of the positive electrode, and affecting the cycle life of the metal battery cell. This disclosure improves the electrolyte wettability of the positive electrode when the electrolyte mass-to-capacity ratio is small by setting the cycle charge / discharge temperature of the metal battery cell to 30℃-80℃, thereby reducing polarization and enabling the metal battery cell to have high energy density and long cycle life. In addition, if the cyclic charge-discharge temperature of a metal battery cell is higher than 80°C, it will intensify the side reactions at the interface of the positive and negative electrodes, thereby aggravating the gas production and capacity decay of the metal battery cell, and consequently reducing the cycle life of the metal battery cell.

[0070] Therefore, by adjusting the composition of the positive electrode film, the composition of the electrolyte, the amount of electrolyte, and the cyclic charge-discharge temperature, this disclosure enables metal battery cells to possess both high energy density and good cycle performance.

[0071] The ratio of electrolyte mass to the capacity of a single metal battery cell is 1.1 g / Ah to 1.6 g / Ah, for example, 1.12 g / Ah, 1.14 g / Ah, 1.16 g / Ah, 1.18 g / Ah, 1.2 g / Ah, 1.22 g / Ah, 1.24 g / Ah, 1.26 g / Ah, 1.28 g / Ah, 1.3 g / Ah, 1.32 g / Ah, etc. g / Ah, 1.34 g / Ah, 1.36 g / Ah, 1.38 g / Ah, 1.4 g / Ah, 1.42 g / Ah, 1.44 g / Ah, 1.46 g / Ah, 1.48 g / Ah, 1.5 g / Ah, 1.52 g / Ah, 1.54 g / Ah, 1.56 g / Ah, 1.58 g / Ah, 1.6 g / Ah, or any range of the above values.

[0072] Optionally, the ratio of electrolyte mass to the capacity of the metal battery cell can be 1.1 g / Ah-1.5 g / Ah, 1.1 g / Ah-1.48 g / Ah, 1.1 g / Ah-1.46 g / Ah, 1.1 g / Ah-1.44 g / Ah, 1.1 g / Ah-1.42 g / Ah, 1.1 g / Ah-1.4 g / Ah, 1.14 g / Ah-1.5 g / Ah, 1.14 g / Ah-1.48 g / Ah, 1.14 g / Ah-1.46 g / Ah, 1.14 g / Ah-1.44 g / Ah, 1.14 g / Ah-1.42 g / Ah, 1.14 g / Ah-1.42 g / Ah, or 1.14 g / Ah. g / Ah-1.4g / Ah, 1.18g / Ah-1.5g / Ah, 1.18g / Ah-1.48g / Ah, 1.18g / Ah-1.46g / Ah, 1.18g / Ah-1.44g / Ah, 1.18g / Ah-1.42g / Ah, 1.18g / A h-1.4g / Ah, 1.2g / Ah-1.5g / Ah, 1.2g / Ah-1.48g / Ah, 1.2g / Ah-1.46g / Ah, 1.2g / Ah-1.44g / Ah, 1.2g / Ah-1.42g / Ah, 1.2g / Ah-1.4g / Ah.

[0073] This allows metal battery cells to better combine high energy density and good cycle performance.

[0074] The cyclic charge and discharge temperature of a single metal battery cell is 30℃-80℃, for example, it can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, or any combination of the above values.

[0075] Optionally, the cyclic charge / discharge temperature of the metal battery cell can be 35℃-75℃, 35℃-70℃, 35℃-65℃, 40℃-75℃, 40℃-70℃, 40℃-65℃, 45℃-75℃, 45℃-70℃, or 45℃-65℃.

[0076] This allows metal battery cells to have better cycle performance.

[0077] The mass of the electrolyte can be tested as follows: Weigh the metal battery cell and record the mass as m0; then disassemble the metal battery cell, centrifuge to separate the electrolyte, immerse all the disassembled solid components in acetonitrile solution, remove them after 2 hours, air dry at room temperature, then transfer them to a 60℃ oven to bake for at least 4 hours, and weigh them again, recording the mass as m1. The difference between the mass of m0 and m1 is taken as the mass of the electrolyte.

[0078] The capacity of a metal battery cell can be tested as follows: At 25°C, the metal battery cell is left to stand for 5 minutes, then discharged at a constant current of 0.33C to the lower cutoff voltage; after standing for 5 minutes, it is charged at a constant current of 0.33C to the upper cutoff voltage, and then charged at a constant voltage at the upper cutoff voltage until the current is 0.1C; after standing for 5 minutes, it is discharged at a constant current of 0.33C to the lower cutoff voltage, and the discharge capacity at this time is recorded, which is the capacity of the metal battery cell.

[0079] The upper and lower cutoff voltages can be the charge / discharge voltages recommended in the product specifications of the metal battery cells.

[0080] For example, positive electrode active materials include 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 0.02 O2(Ni96), LiNi 0.80 Co 0.15 Al 0.05 In O2, the upper limit cutoff voltage of a single metal battery cell can be 4.3V, and the lower limit cutoff voltage can be 2.8V.

[0081] The cycle charge / discharge temperature of a metal battery cell refers to its actual operating temperature. In some embodiments, a heating module can be installed on the outside of the metal battery cell to regulate its cycle charge / discharge temperature.

[0082] In some embodiments, the sum of the mass of the first lithium salt in the positive electrode film and the mass of the second lithium salt in the electrolyte is greater than the saturated solubility in the organic solvent and diluent.

[0083] That is, if all the first lithium salt set in the positive electrode film is added to the electrolyte, lithium salt will be deposited.

[0084] By ensuring that the sum of the mass of the first lithium salt in the positive electrode film 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 positive electrode film can gradually dissolve into the electrolyte under the wetting effect of the electrolyte to dynamically 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.

[0085] [Positive electrode plate]

[0086] The positive electrode includes a positive current collector and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material and a first lithium salt. 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.

[0087] 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.

[0088] Optionally, R1 and R2 may each independently include a fluorine atom or a trifluoromethyl group.

[0089] Alternatively, R1 and R2 may both be fluorine atoms.

[0090] 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.

[0091] In some embodiments, the first lithium salt may include a lithium salt having the structure shown in Formula 1.

[0092] 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.

[0093] Optionally, the first lithium salt may include one or a combination of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0094] Alternatively, the first lithium salt may include lithium bisfluorosulfonylimide (LiFSI).

[0095] 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.

[0096] In some embodiments, the mass percentage of the first lithium salt in the positive electrode film layer can be 0.5%-10%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of the above values.

[0097] When the mass percentage of the first lithium salt is within the aforementioned range, the positive electrode film can provide more first lithium salt to better dynamically replenish the consumption of the second lithium salt without affecting the positive electrode impedance or increasing positive electrode polarization. This allows the metal battery cell to better maintain the solvation structure of the electrolyte during cycling, maintain high oxidation-reduction resistance of the electrolyte, and thus improve the cycle performance of the metal battery cell. Furthermore, as the first lithium salt gradually dissolves from the positive electrode film, the porosity of the positive electrode film increases. This increases the spacing between the positive electrode active material particles, lengthens the ion and electron transport paths, and consequently affects the charge-discharge performance of the metal battery cell. By setting the mass percentage of the first lithium salt within the aforementioned range, it is also beneficial for the positive electrode film to maintain high ion and electron transport capabilities during charge-discharge cycles, further contributing to better cycle performance of the metal battery cell.

[0098] Optionally, in the positive electrode film layer, the mass percentage of the first lithium salt can be 1%-8%, 1%-7%, 1%-6%, 1%-5%, 2%-8%, 2%-7%, 2%-6%, 2%-5%, 3%-8%, 3%-7%, 3%-6%, or 3%-5%.

[0099] This can further improve the cycle performance of metal battery cells.

[0100] The mass percentage of the first lithium salt in the positive electrode film can be tested as follows: Disassemble the positive electrode sheet from the metal battery cell, take a single-sided coated positive electrode sheet (if it is a double-sided coated positive electrode sheet, wipe off the positive electrode film on one side first), soak the positive electrode sheet in a known mass of ethylene glycol dimethyl ether (DME) for a period of time, take out the positive electrode sheet, weigh the mass of ethylene glycol dimethyl ether again, the difference between the two weighings is the mass of the first lithium salt, and the mass percentage of the first lithium salt in the positive electrode film can be calculated.

[0101] 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 positive electrode film may have dissolved out, which will lead to a significant deviation in the test results.

[0102] 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.

[0103] In some embodiments, the porosity of the positive electrode film can be 15%-30%, for example, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any combination of the above values.

[0104] Increased porosity of the positive electrode film facilitates electrolyte wetting. However, as the first lithium salt gradually dissolves from the positive electrode film, its porosity further increases. This leads to larger spacing between the positive electrode active material particles, lengthening ion and electron transport paths, which in turn affects the charge-discharge performance of the metal battery cell. By setting the porosity of the positive electrode film within the aforementioned range, it is beneficial for both electrolyte wetting and maintaining high ion and electron transport capabilities during charge-discharge cycles, thus resulting in better cycle performance for the metal battery cell.

[0105] Optionally, the porosity of the positive electrode film can be 15%-25%.

[0106] The porosity of the positive electrode film can be tested as follows: Disassemble the positive electrode sheet from the metal battery cell. Take a single-sided coated positive electrode sheet (if it is a double-sided coated positive electrode sheet, wipe off the positive electrode film layer on one side first) and cut it into small circular samples of a certain area. Calculate the apparent volume V1 of the positive electrode sheet. Referring to GB / T 24586-2009, use an inert gas (such as helium or nitrogen) as the medium and employ the gas displacement method to measure the true volume V2 of the positive electrode sheet using a true density meter. The porosity of the positive electrode film = (V1-V2) / V1×100%. Multiple samples (e.g., 30 pieces) with good appearance and no powder shedding at the edges can be tested, and the average value of the results can be taken to improve the accuracy of the test results. A Micromeritics AccuPyc II 1340 true density meter can be used for testing.

[0107] 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 positive electrode film may have dissolved out, which will lead to an overestimation of the porosity of the positive electrode film.

[0108] In some embodiments, the positive electrode film layer includes a positive electrode conductive agent, and the mass percentage of the positive electrode conductive agent in the positive electrode film layer can be 0.8%-3%.

[0109] Optionally, the positive electrode conductive agent may include one or more of carbon black (such as Super P), acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

[0110] In some embodiments, the positive electrode film layer further includes 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, polyacrylic acid (PAA), polymethacrylic acid (PMAA), lithium polyacrylate (PAALi), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0111] In some embodiments, the positive electrode active material may include one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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 0.02 O2(Ni96), LiNi0.80 Co 0.15 Al 0.05 One or more of O2 and LiFePO4.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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).

[0120] The positive electrode film can be formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, positive electrode conductive agent, positive electrode binder, and first lithium salt in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0121] Electrolyte

[0122] 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.

[0123] 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.

[0124] Alternatively, R3 and R4 may each independently include a fluorine atom or a trifluoromethyl group.

[0125] Alternatively, R3 and R4 may both be fluorine atoms.

[0126] 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.

[0127] In some embodiments, the second lithium salt may include a lithium salt having the structure shown in Formula 2.

[0128] 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.

[0129] Optionally, the second lithium salt may include one or a combination of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0130] Alternatively, the second lithium salt may include lithium bis(fluorosulfonyl)imide (LiFSI).

[0131] 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.

[0132] The electrolyte is a locally high-concentration electrolyte. This type of electrolyte is produced by adding a diluent that is miscible with organic solvents but has very poor lithium salt dissolution ability. The addition of the diluent does not affect the unique solvation structure of the high-concentration electrolyte and can improve its viscosity and ionic conductivity. This improves the electrolyte wettability of the electrode components and facilitates better dissolution of the first lithium salt in the positive electrode film into the electrolyte during charge-discharge cycles, dynamically replenishing the consumption of the second lithium salt. Ultimately, this enhances the cycle performance of the metal battery cell.

[0133] In some embodiments, the molar ratio of the second lithium salt, organic solvent, and diluent in the electrolyte can be 1:(1-2):(1-3).

[0134] This results in a locally high-concentration electrolyte, which gives the electrolyte a good solvation structure and excellent resistance to oxidation and reduction, thus enabling the metal battery cell to have good cycle performance. It also allows the electrolyte to have both high ionic conductivity and low viscosity, which is beneficial for improving the electrolyte wettability of the electrode assembly. Furthermore, it facilitates the better dissolution of the first lithium salt in the positive electrode film into the electrolyte during charge and discharge cycles to dynamically replenish the consumption of the second lithium salt, thereby further improving the cycle performance of the metal battery cell.

[0135] The molar ratio of the second lithium salt to the organic solvent can be 1:(1-2), for example, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, or any range of the above values.

[0136] The molar ratio of the second lithium salt to the diluent can be 1:(1-3), for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, or any range of the above values.

[0137] In some embodiments, the organic solvent includes ether compounds. This is because ether compounds are more compatible with lithium metal anodes.

[0138] 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.

[0139] In some embodiments, the diluent may include one or more of fluoroether diluents, aromatic diluents, and fluoroaromatic diluents.

[0140] 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.

[0141] In some embodiments, the viscosity of the electrolyte at 25°C can be 2 mPa·s-50 mPa·s, preferably 2 mPa·s-15 mPa·s. This contributes to the long cycle life of the metal battery cell.

[0142] 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.

[0143] 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.

[0144] In some embodiments, the ionic conductivity of the electrolyte at 25°C can be 0.5 mS / cm-15 mS / cm, and can be selected as 2 mS / cm-8 mS / cm.

[0145] The ionic 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 ionic conductivity of each sample can be measured using a conductivity meter at 25°C. The average value of the test results is then taken as the ionic conductivity of the electrolyte. A DDS-307 conductivity meter can be used as the testing instrument.

[0146] The electrolyte can be prepared using methods known in the art.

[0147] [Negative electrode plate]

[0148] 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%.

[0149] 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.

[0150] 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.

[0151] [Isolation membrane]

[0152] 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.

[0153] 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.

[0154] 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.

[0155] Methods for preparing metal battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a metal battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with an electrolyte. After vacuum sealing and settling, a metal battery cell is obtained.

[0156] Example

[0157] 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.

[0158] Example 1

[0159] (1) Preparation of positive electrode sheet

[0160] 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) are mixed in a mass ratio of 98:1:1. Then, lithium bis(fluorosulfonyl)imide (LiFSI) is added and mixed thoroughly. Next, N-methylpyrrolidone (N-methylpyrrolidone) is added as a solvent and stirred until homogeneous to obtain the positive electrode slurry. The positive electrode slurry is evenly coated onto aluminum foil used as the positive electrode current collector, air-dried at room temperature, and then transferred to a 120°C oven for further drying. Finally, it is cold-pressed and cut into 40mm × 50mm rectangles for later use. The areal capacity of the positive electrode is 3.5 mAh / cm². 2 The first lithium salt accounts for 5% of the mass of the positive electrode film.

[0161] (2) Preparation of negative electrode sheet

[0162] A 20μm 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.

[0163] (3) Preparation of electrolyte

[0164] An organic solvent, ethylene glycol dimethyl ether (DME), and a diluent, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), were mixed to obtain a mother liquor. Then, a second lithium salt, lithium bis(fluorosulfonyl)imide (LiFSI), was added, and the mixture was stirred thoroughly to form a colorless and transparent electrolyte. The molar ratio of LiFSI, DME, and TTE was 1:1.2:3.

[0165] (4) Preparation of the separating membrane

[0166] Polyethylene porous membrane was selected as the separator and cut into rectangles of 45mm×55mm for later use.

[0167] (5) Preparation of lithium metal battery cells

[0168] 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.

[0169] 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 0.33C to 2.8V; after standing for 5 minutes, charge it at a constant current of 0.33C 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 0.33C 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 140mAh.

[0170] The ratio of electrolyte mass to lithium metal battery cell capacity is 1.4 g / Ah.

[0171] Weight energy density test: Weigh the lithium metal battery cell W using an electronic scale. At 25℃, charge the lithium metal battery cell at a constant current of 0.33C 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 0.33C to 2.8V to obtain the discharge energy of the lithium metal battery cell. Repeat the test 3 times and take the average value to obtain the average discharge energy E of the lithium metal battery cell. The weight energy density of the lithium metal battery cell (Wh / Kg) = E / W.

[0172] Cyclic performance test: At 50℃, the lithium metal battery cell is charged at a constant current of 0.2C (i.e., 28mA) to 4.3V, and then charged at a constant voltage of 4.3V to a current of 0.1C (i.e., 14mA); after standing for 5 minutes, the lithium metal battery cell is discharged at a constant current of 1C (i.e., 140mA) to 2.8V to obtain the first discharge capacity; the cycle charge and discharge is performed according to the above method. When the discharge capacity after the cycle decays to 80% of the first discharge capacity, the life of the lithium metal battery cell is considered to have ended, and the number of cycles is recorded.

[0173] Examples 2 to 5

[0174] Except for the different cycle charge-discharge temperatures, the preparation method, gravimetric energy density, and cycle performance testing method of the lithium metal battery cells are the same as those in Example 1. The cycle charge-discharge temperature parameters are detailed in Table 1.

[0175] Examples 6 to 8

[0176] Except for the ratio of electrolyte mass to lithium metal battery cell capacity, the preparation method, gravimetric energy density, and cycle performance testing methods for the lithium metal battery cells are the same as in Example 1. The parameters for the ratio of electrolyte mass to lithium metal battery cell capacity are detailed in Table 1. Adjusting the electrolyte mass can adjust the ratio of electrolyte mass to lithium metal battery cell capacity.

[0177] Comparative Example 1

[0178] Except that the positive electrode film does not contain the first lithium salt, the preparation method, weight energy density and cycle performance test method of the lithium metal battery cell are the same as those in Example 1.

[0179] Comparative Example 2

[0180] Except that the positive electrode film layer does not contain the first lithium salt and the ratio of electrolyte mass to lithium metal battery cell capacity is 2.0 g / Ah, the preparation method, gravimetric energy density, and cycle performance testing method of the lithium metal battery cell are the same as in Example 1. Adjusting the electrolyte mass can adjust the ratio of electrolyte mass to lithium metal battery cell capacity.

[0181] Comparative Example 3

[0182] Except that the positive electrode film does not contain the first lithium salt and the cycle charge-discharge temperature is 25°C, the preparation method, weight energy density and cycle performance test method of the lithium metal battery cell are the same as those in Example 1.

[0183] Comparative Example 4

[0184] Except for the cyclic charge-discharge temperature of 25°C, the preparation method, gravimetric energy density, and cycle performance testing method of the lithium metal battery cell are the same as those in Example 1.

[0185] Table 1

[0186] As can be seen from the above test results, by setting a first lithium salt in the positive electrode film layer and adjusting the cycle charge and discharge temperature of the lithium metal battery cell to 30℃-80℃, this disclosure can achieve high energy density and good cycle performance of the lithium metal battery cell by reducing the amount of electrolyte (the ratio of electrolyte mass to lithium metal battery cell capacity is 1.1g / Ah-1.6g / Ah).

[0187] The test results from Examples 1 to 5 also show that further adjusting the cycle charge and discharge temperature of the lithium metal battery cell can further improve the cycle performance of the lithium metal battery cell.

[0188] The test results from Examples 1, 6 to 8 also show that further adjusting the ratio of electrolyte mass to lithium metal battery cell capacity can enable lithium metal battery cells to better combine high energy density and good cycle performance.

[0189] Compared with Comparative Example 1, Comparative Example 2 can improve the cycle performance of lithium metal battery cells by increasing the electrolyte mass, but it greatly sacrifices the energy density of lithium metal battery cells, making it impossible for lithium metal battery cells to have both high energy density and good cycle performance.

[0190] The test results of Comparative Examples 3 and 4 also show that when the cycle charge-discharge temperature is low and the ratio of electrolyte mass to the capacity of the lithium metal battery cell is small, setting a high content of the first lithium salt in the positive electrode film is not conducive to improving the cycle performance of the lithium metal battery cell. This is because the lithium metal battery cell is prone to polarization at this time. Polarization will reduce the actual operating voltage of the lithium metal battery cell and increase the positive electrode impedance, which will hinder the ion transport of lithium ions during charge and discharge, reduce the reversible capacity of the positive electrode, and affect the cycle performance of the lithium metal battery cell.

[0191] Examples 1-1 to 1-4

[0192] Except for the different mass ratio of the first lithium salt in the positive electrode film, the preparation method, weight energy density and cycle performance test method of the lithium metal battery cell are the same as those in Example 1. The mass ratio parameters of the first lithium salt in the positive electrode film are detailed in Table 2.

[0193] Table 2

[0194] The test results above show that further adjusting the mass ratio of the first lithium salt in the positive electrode film can further improve the cycle performance of lithium metal battery cells.

[0195] Examples 2-1 to 2-3

[0196] Except for the difference in porosity of the positive electrode film, the preparation method, weight energy density and cycle performance test method of the lithium metal battery cell are the same as those in Example 1. The porosity parameters of the positive electrode film are detailed in Table 3.

[0197] The porosity of the positive electrode film can be adjusted by regulating the compaction density of the positive electrode film.

[0198] Porosity test of the positive electrode film: The positive electrode film layer on one side of the positive electrode sheet was wiped off to obtain a single-sided coated positive electrode sheet, which was then cut into small circular samples of a certain area. The apparent volume V1 of the positive electrode sheet was calculated. Referring to GB / T 24586-2009, using inert helium as the medium, the true volume V2 of the positive electrode sheet was measured using a gas displacement method and a true density meter. The porosity of the positive electrode film layer = (V1-V2) / V1×100%. Thirty samples with good appearance and no powder shedding at the edges were tested, and the average value was taken. The testing instrument used was a Micromeritics AccuPyc II 1340 true density meter.

[0199] Table 3

[0200] The test results above show that further adjusting the porosity of the positive electrode film can further improve the cycle performance of lithium metal battery cells.

[0201] Examples 3-1 to 3-2

[0202] Except for the different electrolyte composition, the preparation method, weight energy density and cycle performance test method of the lithium metal battery cell are the same as those in Example 1. The electrolyte composition is detailed in Table 4.

[0203] Table 4

[0204] The test results above show that further adjusting the composition of the electrolyte can adjust its viscosity. During the cyclic charging and discharging process, this facilitates the better dissolution of the first lithium salt in the positive electrode film into the electrolyte, thereby better dynamically replenishing the consumption of the second lithium salt and further improving the cycle performance of the lithium metal battery cell.

[0205] 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 and a positive electrode film layer located on at least one side of the positive current collector. The positive electrode film layer includes a positive active material and a first lithium salt. 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 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. The ratio of the mass of the electrolyte to the capacity of the metal battery cell is 1.1 g / Ah - 1.6 g / Ah; The cycle charge / discharge temperature of the metal battery cell is 30℃-80℃.

2. The metal battery cell according to claim 1, wherein, The ratio of the mass of the electrolyte to the capacity of the metal battery cell is 1.2 g / Ah to 1.4 g / Ah.

3. The metal battery cell according to any one of claims 1-2, wherein, The cycle charge / discharge temperature of the metal battery cell is 45℃-65℃.

4. The metal battery cell according to any one of claims 1-3, wherein, The sum of the mass of the first lithium salt in the positive electrode film and the mass of the second lithium salt in the electrolyte is greater than the saturated solubility in the organic solvent and the diluent.

5. The metal battery cell according to any one of claims 1-4, wherein, In the positive electrode film layer, the mass percentage of the first lithium salt is 0.5%-10%.

6. The metal battery cell according to claim 5, wherein, In the positive electrode film layer, the mass percentage of the first lithium salt is 1%-5%.

7. The metal battery cell according to any one of claims 1-6, wherein, The porosity of the positive electrode film is 15%-30%.

8. The metal battery cell according to claim 7, wherein, The porosity of the positive electrode film is 15%-25%.

9. The metal battery cell according to any one of claims 1-8, wherein, The positive electrode film layer includes a positive electrode conductive agent, and the positive electrode conductive agent accounts for 0.8%-3% of the mass of the positive electrode film layer.

10. The metal battery cell according to any one of claims 1-9, wherein, The positive electrode film layer includes a positive electrode conductive agent, which includes one or more of carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon nanofibers.

11. The metal battery cell according to any one of claims 1-10, wherein, The first lithium salt comprises a lithium salt having the structure shown in Formula 1; and / or, The second lithium salt includes a lithium salt having the structure shown in Formula 2.

12. The metal battery cell according to any one of claims 1-11, wherein, R1 and R2 each independently include a fluorine atom or a trifluoromethyl group; and / or, R3 and R4 each independently include a fluorine atom or a trifluoromethyl group.

13. The metal battery cell according to any one of claims 1-12, wherein, In the electrolyte, the molar ratio of the second lithium salt, the organic solvent, and the diluent is 1:(1-2):(1-3).

14. The metal battery cell according to any one of claims 1-13, wherein, The organic solvent includes ether compounds; and / or, The diluent includes one or more of fluoroether diluents, aromatic diluents, and fluorinated aromatic diluents.

15. The metal battery cell according to claim 14, 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.

16. The metal battery cell according to any one of claims 1-15, 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.

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

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

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