Lithium metal battery monomer, electrolyte, battery device and power utilization device

Abstract

The invention provides a lithium metal battery monomer, an electrolyte, a battery device and a power utilization device. The lithium metal battery monomer comprises an electrolyte, the electrolyte comprises a lithium salt, carbon quantum dots, an ether solvent and a diluent, and the ether solvent is used for dispersing and / or dissociating the lithium salt; the diluent is used for diluting the ether solvent; and the lithium salt and the diluent are immiscible. The lithium metal battery monomer has improved cycle life and dynamic performance; according to the electrolyte, the cycle life and the dynamic performance of the lithium metal battery monomer can be improved. The battery device and the power utilization device comprising the lithium metal battery cell at least have the above beneficial effects.

Description

Technical Field

[0001] This application belongs to the field of lithium metal battery cell technology, specifically relating to a lithium metal battery cell, electrolyte, battery device, and power supply device. Background Technology

[0002] With the rapid development of lithium batteries in electric vehicles, electric aviation, and other fields, the public's performance requirements for battery products are increasing due to the limitations of application scenarios. Attributable to the high theoretical specific capacity (3860 mAh g⁻¹) and low redox potential (-3.04 V vs. standard hydrogen electrode) of the lithium metal anode, the energy density of a single lithium metal battery cell can exceed 500 Wh / kg, making it one of the most promising next-generation battery systems. However, the anode sheet in a lithium metal battery cell undergoes significant volume changes during charge and discharge, and the solid electrolyte interphase (SEI) film at the interface between the anode sheet and the electrolyte repeatedly ruptures and regenerates during cycling, affecting the performance of the lithium metal battery cell.

[0003] Therefore, there is an urgent need to provide a lithium metal battery cell with good overall performance. Summary of the Invention

[0004] The purpose of this application is to provide a lithium metal battery cell that achieves improved cycle life and kinetic performance; the electrolyte of this application can further improve the cycle life and kinetic performance of the lithium metal battery cell. Battery devices and power-consuming devices incorporating this lithium metal battery cell have at least the aforementioned beneficial effects.

[0005] In a first aspect, embodiments of this application provide a lithium metal battery cell, which includes an electrolyte comprising lithium salt, carbon quantum dots, an ether solvent, and a diluent. The ether solvent is used to disperse and / or dissociate the lithium salt; the diluent is used to dilute the ether solvent; and the lithium salt and the diluent are immiscible.

[0006] In this embodiment, the electrolyte of the lithium metal battery cell includes lithium salt, ether solvent, and diluent. The lithium salt and diluent are immiscible. The ether solvent is used to disperse and / or dissociate the lithium salt. The diluent is used to dilute the ether solvent, forming an electrolyte with a locally high concentration of lithium salt anions. This electrolyte exhibits excellent compatibility with the negative electrode of the lithium metal battery. The lithium salt anions can form a solid electrolyte layer (SEI) dominated by anion derivatization on the lithium metal surface, promoting uniform lithium deposition and enhancing the stability of the solid electrolyte membrane. Compared with traditional electrolytes, this improves the cycle life of the lithium metal battery cell.

[0007] In the embodiments of this application, during the later stages of electrochemical cycling of a lithium metal battery cell, the electrolyte membrane at the interface between the negative electrode and the electrolyte exhibits a certain degree of polarization. The electrolyte membrane (SEI membrane) may be continuously damaged and reformed, affecting the cycle capacity stability and kinetic performance of the lithium metal battery cell. The electrolyte in this embodiment contains dispersed carbon quantum dots. Carbon quantum dots are zero-dimensional materials that participate in the formation of the SEI membrane. They possess abundant edge defects and can act as rapid diffusion channels for lithium ions within the SEI membrane, improving the ionic conductivity of the SEI membrane. This facilitates the passage of lithium ions through the SEI membrane and their uniform deposition on the negative electrode, mitigating the aforementioned polarization phenomenon and enhancing the kinetic performance of the lithium metal battery cell.

[0008] In summary, in the later stages of lithium metal battery cycling, compared to traditional electrolytes, electrolytes with locally high concentrations of lithium salt anions are prone to causing damage to the SEI film and polarization at the interface between the negative electrode and the electrolyte. The electrolyte system of this application incorporates graphene quantum dots, and the various components of the electrolyte work synergistically to comprehensively improve the cycle life and kinetic performance of lithium metal batteries, manifested in high rate capability and reversible capacity utilization throughout the entire life cycle.

[0009] In some optional embodiments, the mass concentration of carbon quantum dots in the electrolyte is 0.01 mg / mL to 2 mg / mL. The uniform attachment of carbon quantum dots to the ultrathin lithium metal battery cell electrochemical interface (SEI film) improves the cycle capacity retention and kinetic performance of the lithium metal battery cell.

[0010] In some optional embodiments, the mass concentration of carbon quantum dots in the electrolyte is 0.1 mg / mL to 1 mg / mL. Within this range, the mass concentration of carbon quantum dots can participate in the formation of the SEI film, increasing its ionic conductivity and promoting the uniform deposition of lithium ions through the SEI film on the negative electrode. This further improves the aforementioned polarization phenomenon and enhances the cycle capacity stability and kinetic performance of the lithium metal battery cell.

[0011] In some alternative embodiments, carbon quantum dots include one or more of graphene quantum dots, graphene oxide quantum dots, fluorinated graphene quantum dots, chlorinated graphene quantum dots, carboxylated graphene quantum dots, hydroxylated graphene quantum dots, and aminographene quantum dots.

[0012] In some optional embodiments, the lithium salt content in the electrolyte is 20% to 28% by mass.

[0013] When the lithium salt mass content is within the above range, side reactions and lithium loss can be reduced, the formation of "dead lithium" in the battery can be reduced, and the cycle capacity retention rate of lithium metal battery cells can be improved. It can also optimize the interfacial characteristics of the electrode and electrolyte, enhance the interfacial stability of the battery, and improve the service life of lithium metal battery cells.

[0014] In some optional embodiments, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0015] In some optional embodiments, the molar ratio of lithium salt, ether solvent, and diluent is 1:(0.4–3):(1–5). Controlling the amounts of lithium salt, ether solvent, and diluent within this range ensures a low impedance between the electrode and the electrolyte, which is beneficial for forming a stable and dense SEI layer on the surface of the negative electrode, thus improving the cycle capacity retention of the lithium metal battery cell. It also promotes uniform deposition of lithium ions on the negative electrode surface, suppresses dendrite formation, and improves the reliability of the lithium metal battery cell.

[0016] In some optional embodiments, the molar ratio of lithium salt, ether solvent, and diluent is 1:(1.2–2):(3–3.5). Therefore, the cycle capacity retention and reliability of lithium metal battery cells can be further improved.

[0017] In some optional embodiments, the ether solvent includes one or more of diethyl ether, dipropyl ether, ethylpropyl ether, methyl butyl ether, dibutyl ether, ethyl butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol diethyl ether, propylene glycol diethyl ether, butanediol dimethyl ether, butanediol diethyl ether, tetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxopentane, tetrahydropyran, 1,3-dioxane, and 1,4-dioxane.

[0018] In some optional embodiments, the diluent includes benzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl) ether, and bis(2,2-difluoroethyl) ether. One or more of the following: 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropylmethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, and bis(1,1,2,2-tetrafluoroethyl) ether.

[0019] In some optional embodiments, the electrolyte conductivity ranges from 1 mS / cm to 10 mS / cm. The electrolyte conductivity reflects the migration ability of lithium ions within the electrolyte. This conductivity can reduce the internal resistance of lithium metal battery cells, increase the charge transfer rate, improve kinetic performance, and enable lithium metal battery cells to maintain high energy output at high current densities. This conductivity also helps reduce current unevenness and improve the cycle life of lithium metal battery cells.

[0020] In some optional embodiments, the electrolyte conductivity ranges from 2 mS / cm to 8 mS / cm. This further improves the cycle life and kinetic performance of the lithium metal battery cell.

[0021] In some optional embodiments, the viscosity of the electrolyte is from 1 mPa·s to 10 mPa·s. The viscosity of the electrolyte affects the diffusion rate of lithium ions within the electrolyte. Electrolyte viscosities within the above range help to increase the lithium ion diffusion coefficient, thereby accelerating charge transfer and improving the kinetic performance of lithium metal battery cells. Electrolytes with the above viscosities also help to balance the lithium deposition process, reduce dendrite formation, and improve the stability and cycle life of lithium metal battery cells.

[0022] In some optional embodiments, the electrolyte viscosity is from 1.5 mPa·s to 8.5 mPa·s. This further improves the cycle life and kinetic performance of the lithium metal battery cell.

[0023] In some optional embodiments, the lithium metal battery cell includes a negative electrode sheet, the negative electrode sheet includes a composite lithium layer, the composite lithium layer includes lithium metal and carbon quantum dots, the lithium metal is a continuous phase and the carbon quantum dots are a dispersed phase.

[0024] In the embodiments of this application, the composite lithium layer of the negative electrode sheet contains lithium metal material and carbon quantum dots. Carbon quantum dots are a zero-dimensional material with abundant edge defects and lithium affinity. The carbon quantum dots uniformly dispersed in the lithium metal serve as uniform heterogeneous nucleation sites, which can also reduce the nucleation potential of lithium ions, which is beneficial to the deposition and solvation of lithium ions, thereby reducing the risk of lithium dendrite growth and improving the reliability of lithium metal batteries. The carbon quantum dots uniformly dispersed in the lithium metal can then uniformly attach to the ultrathin lithium metal battery electrochemical interface (SEI film), guiding the uniform and dense nucleation and deposition of lithium, reducing the polarization of the anode / electrolyte interface, and improving the cycle capacity retention rate of lithium metal batteries. During the electrochemical cycling process of lithium metal batteries, as metallic lithium is consumed, carbon quantum dots participate in the formation of the SEI film in situ, which can serve as a fast diffusion channel for lithium ions and enhance the ion conduction capacity of the SEI film, which is beneficial to improving the kinetic performance of lithium metal batteries.

[0025] Furthermore, in the later stages of electrochemical cycling of lithium metal batteries, the surface of the lithium metal anode still contains uniform carbon quantum dots, which allows for the regulation of lithium metal nucleation behavior throughout the entire life cycle of the lithium metal battery.

[0026] In some optional embodiments, the mass content of carbon quantum dots in the composite lithium layer is 0.01% to 10%. Therefore, carbon quantum dots can reduce the nucleation potential of lithium ions, which is beneficial to the deposition and solvation of lithium ions and improves the reliability of lithium metal batteries; the uniform attachment of carbon quantum dots to the ultrathin lithium metal battery electrochemical interface (SEI film) improves the cycle capacity retention and kinetic performance of lithium metal batteries.

[0027] In some optional embodiments, the mass content of carbon quantum dots in the composite lithium layer is 0.5% to 2%. This further improves the cycle capacity retention and kinetic performance of the lithium metal battery.

[0028] In some optional embodiments, the carbon quantum dots include one or more of graphene quantum dots, graphene oxide quantum dots, fluorinated graphene quantum dots, chlorinated graphene quantum dots, carboxylated graphene quantum dots, hydroxylated graphene quantum dots, and aminographene quantum dots. The above-mentioned types of carbon quantum dots can improve the reliability of lithium metal batteries, and enhance their cycle capacity retention and kinetic performance.

[0029] In some optional embodiments, the thickness of the composite lithium layer is 2–100 micrometers. When the thickness of the composite lithium layer is within this range and includes uniformly distributed carbon quantum dots, lithium can still be uniformly deposited during the charge-discharge process due to repeated lithium deposition and stripping, thus improving the cycle life and reliability of the lithium metal battery.

[0030] In some optional embodiments, the thickness of the composite lithium layer is 10–20 micrometers. This further improves the cycle life and reliability of the lithium metal battery.

[0031] In some alternative embodiments, the negative electrode includes a negative current collector and a composite lithium layer disposed on at least one side of the negative current collector. Therefore, this type of negative electrode is advantageous in balancing the energy density and kinetic performance of lithium metal batteries.

[0032] Secondly, embodiments of this application provide an electrolyte for lithium metal battery cells, comprising lithium salt, carbon quantum dots, ether solvent, and diluent, wherein the ether solvent is used to disperse and / or dissociate the lithium salt; the diluent is used to dilute the ether solvent; and the lithium salt and diluent are immiscible.

[0033] In this embodiment, the electrolyte of the lithium metal battery cell includes lithium salt, ether solvent, and diluent. The lithium salt and diluent are immiscible. The ether solvent is used to disperse and / or dissociate the lithium salt. The diluent is used to dilute the ether solvent, forming an electrolyte with a locally high concentration of lithium salt anions. This electrolyte exhibits excellent compatibility with the negative electrode of the lithium metal battery. The lithium salt anions contribute to the formation of a dense solid electrolyte membrane (SEI membrane), enhancing the stability of the SEI membrane and improving the cycle life of the lithium metal battery cell compared to traditional electrolytes.

[0034] In the embodiments of this application, during the later stages of electrochemical cycling of a lithium metal battery cell, the electrolyte membrane at the interface between the negative electrode and the electrolyte exhibits a certain degree of polarization. The electrolyte membrane (SEI membrane) may be continuously damaged and reformed, affecting the cycle capacity stability and kinetic performance of the lithium metal battery cell. The electrolyte in this embodiment contains dispersed carbon quantum dots. Carbon quantum dots are zero-dimensional materials that participate in the formation of the SEI membrane. They possess abundant edge defects and can act as rapid diffusion channels for lithium ions within the SEI membrane, improving the ionic conductivity of the SEI membrane. This facilitates the passage of lithium ions through the SEI membrane and their uniform deposition on the negative electrode, mitigating the aforementioned polarization phenomenon and enhancing the kinetic performance of the lithium metal battery cell.

[0035] In the later stages of lithium metal battery cycling, compared to traditional electrolytes, electrolytes with locally high concentrations of lithium salt anions are prone to causing damage to the SEI film and polarization at the interface between the negative electrode and the electrolyte. Therefore, graphene quantum dots are added to the electrolyte system of this application. The synergistic effect of the various electrolyte components comprehensively improves the cycle life and kinetic performance of lithium metal batteries, manifested in high rate capability and reversible capacity utilization throughout the entire life cycle.

[0036] Thirdly, embodiments of this application provide a battery device, including a lithium metal battery cell of the first aspect or a battery cell prepared using the electrolyte of the second aspect. The battery device of this application includes the lithium metal battery cell of the first aspect or a lithium metal battery cell prepared using the electrolyte of the second aspect, and therefore has at least the advantages of lithium metal battery cells or electrolytes.

[0037] Fourthly, embodiments of this application provide an electrical device that includes the battery device of the third aspect. The electrical device of this application includes the battery device of the third aspect, and therefore has at least the advantages corresponding to the battery device. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0039] Figure 1 A schematic diagram of one embodiment of the lithium metal battery cell of this application is shown.

[0040] Figure 2 It shows Figure 1 An exploded view of one embodiment of a lithium metal battery cell is shown.

[0041] Figure 3 A schematic diagram of the battery pack according to one embodiment of this application is shown.

[0042] Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0043] Figure 5 A schematic diagram of one embodiment of an electrical device incorporating the lithium metal battery cell of this application as a power source is shown.

[0044] The accompanying drawings are not necessarily drawn to scale. The reference numerals are as follows: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Lithium metal battery cell. Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the lithium metal battery cell, electrolyte, battery device, and power-consuming device of this application. 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 application and are not intended to limit the subject matter of the claims.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of 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 specific parameters, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, characterized in that a and b are both 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.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0049] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0050] Unless otherwise specified, in this application, the terms "first," "second," "third," "fourth," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0051] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a lithium metal battery cell, including but not limited to lithium ions.

[0052] In this application, "multiple" or "more than" refers to two or more items (including two). In this application, "several items" or "multiple items" refers to two or more items (including two).

[0053] The lithium metal battery cell mentioned in the embodiments of this application may be a lithium-ion lithium metal battery cell, a lithium metal battery cell, etc., and the embodiments of this application are not limited to this.

[0054] The battery device mentioned in the embodiments of this application may include one or more lithium metal battery cells as a single physical module to provide higher voltage and capacity. For example, the battery device mentioned in this application may include lithium metal battery cells, battery modules, or battery packs.

[0055] In some alternative embodiments, the battery device can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc. The battery device mentioned in the embodiments of this application may include one or more lithium metal battery cell assemblies for providing voltage and capacity. A lithium metal battery cell assembly may include multiple lithium metal battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0056] In some alternative embodiments, a lithium metal battery cell assembly is typically formed by arranging multiple lithium metal battery cells; as an example, a lithium metal battery cell assembly can be a battery module, which is formed by arranging and fixing multiple lithium metal battery cells into a single module. As an example, a battery module can be formed by bundling multiple lithium metal battery cells together with cable ties.

[0057] In some alternative embodiments, the battery device may be a battery pack, which may include a housing and one or more lithium metal battery cell assemblies housed within the housing. In some alternative 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.

[0058] As an example, a lithium metal battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0059] As an example, lithium metal battery cell assemblies can also be housed in a housing by directly fixing multiple lithium metal battery cells to the housing.

[0060] A lithium metal battery cell is the smallest unit that makes up a battery device, and it can independently perform the functions of charging and discharging. A lithium metal battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited to this. Figure 1 This is an example of a rectangular lithium metal battery cell 5.

[0061] When there are multiple lithium metal battery cells, the multiple lithium metal battery cells are connected in series, parallel, or mixed through a busbar. In some optional embodiments, the battery can be a battery module; when there are multiple lithium metal battery cells, the multiple lithium metal battery cells are arranged and fixed to form a battery module.

[0062] In some alternative embodiments, lithium metal battery cells can be assembled into battery modules, and the number of lithium metal battery cells contained in a battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module. Figure 2 This is a schematic diagram of battery module 4 as an example. Figure 2 As shown, in battery module 4, multiple lithium metal battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple lithium metal battery cells 5 can be fixed in place using fasteners.

[0063] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple lithium metal battery cells 5 are received.

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

[0065] Figure 3 and Figure 4 This is a schematic diagram of battery pack 1 as an example. Figure 3 and Figure 4 As shown, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0066] The lithium metal battery cells provided in the embodiments of this application can be secondary batteries, primary batteries, etc. A secondary battery is a lithium metal battery cell that can be recharged after discharge to activate the active materials and continue to be used.

[0067] The lithium metal battery cell provided in this application includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode and a negative electrode. The negative electrode can be a lithium metal negative electrode. The electrode assembly can be a wound structure or a stacked structure; this application does not limit this. In some embodiments, the electrode assembly further includes a separator disposed between the positive and negative electrode. In some embodiments, the separator is a separator membrane. This application does not have a particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected. In some embodiments, the electrode assembly may not have a separator, and the electrolyte may function as a separator.

[0068] Lithium metal battery cells may also include an outer packaging, which can be used to encapsulate electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of aluminum-plastic film, polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0069] Research has revealed that the solid electrolyte interphase (SEI) film at the interface between the negative electrode and the electrolyte in lithium metal battery cells repeatedly ruptures and regenerates during electrochemical cycling, triggering continuous reactions and consumption of active lithium and electrolyte, thus affecting the performance of the lithium metal battery cell. Furthermore, the accumulation of large amounts of electrolyte reaction products on the surface of the negative electrode causes severe polarization, further leading to a rapid deterioration in battery cycle stability and rate performance. Therefore, lithium metal battery cells using conventional electrolytes have extremely short cycle lives, which seriously hinders their practical application.

[0070] While reactions between the electrolyte and the negative electrode are difficult to avoid, the SEI film, acting as a nanoscale passivation layer between lithium metal and the electrolyte, can mitigate these ongoing reactions. Currently, many new electrolyte systems have been developed to form stable solid-state electrolyte interfacial films. However, a common problem faced by electrolytes is that in the later stages of cycling, the continuous reduction of anions leads to the accumulation of SEI components with low ionic conductivity, resulting in severe polarization of the negative electrode and a sharp drop in cell cycle and rate performance.

[0071] In view of this, embodiments of this application provide a lithium metal battery cell that improves the cycle life and rate performance of the lithium metal battery by designing an electrolyte to mitigate the continuous reaction between active lithium ions and the electrolyte, and by reducing the polarization of the negative electrode.

[0072] Electrolyte

[0073] This application provides a lithium metal battery cell, which includes an electrolyte.

[0074] In some optional embodiments, the electrolyte includes a lithium salt, carbon quantum dots, an ether solvent, and a diluent, wherein the ether solvent is used to disperse and / or dissociate the lithium salt; the diluent is used to dilute the ether solvent; and the lithium salt and the diluent are immiscible.

[0075] In this embodiment, the electrolyte of the lithium metal battery cell includes lithium salt, ether solvent, and diluent. The lithium salt and diluent are immiscible. The ether solvent is used to disperse and / or dissociate the lithium salt. The diluent is used to dilute the ether solvent, forming an electrolyte with a locally high concentration of lithium salt anions. This electrolyte exhibits excellent compatibility with the negative electrode of the lithium metal battery. The lithium salt anions contribute to the formation of a dense solid electrolyte membrane (SEI membrane), enhancing the stability of the SEI membrane and improving the cycle life of the lithium metal battery cell compared to traditional electrolytes.

[0076] In the embodiments of this application, during the later stages of electrochemical cycling of a lithium metal battery cell, the electrolyte membrane at the interface between the negative electrode and the electrolyte exhibits a certain degree of polarization. The electrolyte membrane (SEI membrane) may be continuously damaged and reformed, affecting the cycle capacity stability and kinetic performance of the lithium metal battery cell. The electrolyte in this embodiment contains dispersed carbon quantum dots. Carbon quantum dots are zero-dimensional materials that participate in the formation of the SEI membrane. They possess abundant edge defects and can act as rapid diffusion channels for lithium ions within the SEI membrane, improving the ionic conductivity of the SEI membrane. This facilitates the passage of lithium ions through the SEI membrane and their uniform deposition on the negative electrode, mitigating the aforementioned polarization phenomenon and enhancing the kinetic performance of the lithium metal battery cell.

[0077] In summary, during the later stages of electrochemical cycling in lithium metal battery cells, electrolytes with locally high concentrations of lithium salt anions are more prone to SEI film damage and interfacial polarization between the negative electrode and the electrolyte, compared to traditional electrolytes. Therefore, by adding graphene quantum dots to the electrolyte system of this application, the synergistic effect of the electrolyte components comprehensively improves the cycle life and kinetic performance of lithium metal batteries, manifested in high rate capability and reversible capacity utilization throughout the entire life cycle.

[0078] In some optional embodiments, the mass concentration of carbon quantum dots in the electrolyte is 0.01 mg / mL to 2 mg / mL. The uniform attachment of carbon quantum dots to the ultrathin lithium metal battery cell electrochemical interface (SEI film) improves the cycle capacity retention and kinetic performance of the lithium metal battery cell.

[0079] Optionally, the mass concentration of carbon quantum dots in the electrolyte can be any value or a range thereof from 0.01 mg / mL, 0.02 mg / mL, 0.03 mg / mL, 0.04 mg / mL, 0.05 mg / mL, 0.06 mg / mL, 0.07 mg / mL, 0.08 mg / mL, 0.09 mg / mL, 0.10 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, and 1.0 mg / mL.

[0080] In some optional embodiments, the mass concentration of carbon quantum dots in the electrolyte is 0.1 mg / mL to 1 mg / mL. Within this range, the mass concentration of carbon quantum dots can participate in the formation of the SEI film, increasing its ionic conductivity and promoting the uniform deposition of lithium ions through the SEI film on the negative electrode. This further improves the aforementioned polarization phenomenon and enhances the cycle capacity stability and kinetic performance of the lithium metal battery cell.

[0081] In some alternative embodiments, carbon quantum dots include one or more of graphene quantum dots, graphene oxide quantum dots, fluorinated graphene quantum dots, chlorinated graphene quantum dots, carboxylated graphene quantum dots, hydroxylated graphene quantum dots, and aminographene quantum dots.

[0082] For example, carboxyl-based graphene quantum dots, the carboxyl group can endow graphene quantum dots with strong electronegativity, giving them high lithium-ion affinity, which is beneficial to improving lithium-ion conductivity and enhancing the dynamic performance of lithium metal battery cells.

[0083] In some optional embodiments, carbon quantum dots include polar groups or polar atoms. Polar groups include one or more of carboxyl, amino, and hydroxyl groups. Polar atoms include one or more of oxygen and chlorine atoms. The abundant polar groups in carbon quantum dots allow for uniform dispersion in the electrolyte. Exemplarily, uniform dispersion of carbon quantum dots can be achieved using methods such as ultrasonication or stirring.

[0084] In some optional embodiments, the lithium salt content in the electrolyte is 20% to 28% by mass.

[0085] Optionally, the mass percentage of lithium salt in the electrolyte can be any value or range thereof from 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, and 28%. In some optional embodiments, the mass percentage of lithium salt in the electrolyte is 24% to 25%.

[0086] When the lithium salt mass content is within the above range, unnecessary side reactions or loss of active lithium ions can be reduced, the formation of "dead lithium" in the battery can be reduced, and the cycle capacity retention rate of lithium metal battery cells can be improved. It can also optimize the interfacial characteristics of the electrode and electrolyte, enhance the interfacial stability of the battery, and improve the service life of lithium metal battery cells.

[0087] In some optional embodiments, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalateborate, lithium difluorooxalateborate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The mass content of the lithium salt within the above range provides sufficient lithium ions to improve the ionic conductivity of the electrolyte, thereby enhancing the kinetic performance of the lithium metal battery cell. The lithium salt helps form a stable solid electrolyte interphase (SEI) layer on the electrode surface, protecting the electrode material, reducing side reactions, and improving the cycle life of the lithium metal battery cell. The lithium salt can improve the thermal stability of the electrolyte and enhance the reliability of the lithium metal battery cell.

[0088] In some optional embodiments, the molar ratio of lithium salt, ether solvent, and diluent is 1:(0.4–3):

[0089] (1-5).

[0090] Optionally, the following ratios are also possible: 1:0.4:1, 1:0.5:1, 1:0.6:1, 1:0.7:1, 1:0.8:1, 1:0.9:1, 1:1:1, 1:1.1:1, 1:1.2:1, 1:1.3:1, 1:1.4:1, 1:1.5:1, 1:1.6:1, 1:1.7:1, 1:1.8:1, 1:1.9:1, 1:2:1, and 1:2.1. The ratios of lithium salts, ether solvents, and diluents within the above ranges (e.g., 1:1, 1:2.2:1, 1:2.3:1, 1:2.4:1, 1:2.5:1, 1:2.6:1, 1:2.7:1, 1:2.8:1, 1:2.9:1, 1:3:1, 1:0.4:2, 1:0.5:3, 1:0.6:4, 1:0.7:5, 1:2:2, 1:3:3, 1:3:4, 1:3:5) can be controlled within these ranges. Maintaining the amounts of lithium salts, ether solvents, and diluents within these ranges ensures low impedance between the electrode and electrolyte, which is beneficial for forming a stable and dense SEI layer on the negative electrode surface, improving the cycle capacity retention of lithium metal battery cells. It also promotes uniform deposition of lithium ions on the negative electrode surface, suppresses dendrite formation, and improves the reliability of lithium metal battery cells.

[0091] In some optional embodiments, the molar ratio of lithium salt, ether solvent, and diluent is 1:(1.2–2):

[0092] (3~3.5). Therefore, the cycle capacity retention and reliability of lithium metal battery cells can be further improved.

[0093] In some optional embodiments, the ether solvent includes one or more of diethyl ether, dipropyl ether, ethylpropyl ether, methyl butyl ether, dibutyl ether, ethyl butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol diethyl ether, propylene glycol diethyl ether, butanediol dimethyl ether, butanediol diethyl ether, tetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxopentane, tetrahydropyran, 1,3-dioxane, and 1,4-dioxane.

[0094] In some optional embodiments, the diluent includes benzene (BZ), fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl) ether, bis(2,2-difluoroethyl) One or more of the following: ether, 1,1,2,3,3,3-hexafluoropropylethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropylmethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, and bis(1,1,2,2-tetrafluoroethyl) ether.

[0095] In some optional embodiments, the electrolyte may also include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of lithium metal battery cells, such as additives that improve the overcharge / fast charge performance of lithium metal battery cells, additives that improve the high-temperature performance of lithium metal battery cells, and additives that improve the low-temperature performance of lithium metal battery cells.

[0096] The preparation methods for electrolytes are well known. For example, an electrolyte salt (lithium salt), a solvent, and optional additives can be mixed evenly to obtain an electrolyte. There are no particular restrictions on the order in which the materials are added during the preparation process; they can be added simultaneously or in batches.

[0097] The components and their contents in the electrolyte can be determined using conventional methods in the field. For example, they can be detected using gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), inductively coupled plasma optical emission spectrometry (ICP-OES), infrared spectroscopy, Raman spectroscopy, nuclear magnetic resonance, and other methods.

[0098] As an example, compounds in an electrolyte can be identified using infrared spectroscopy, such as the characteristic peak of the sulfur-oxygen double bond in sulfoxide compounds at 1060 cm⁻¹. -1 -1040cm -1Within the specified range, high-resolution gas chromatography-high-resolution mass spectrometry (HPLC-MS) can separate different components in the electrolyte and obtain high-precision molecular weights, thereby determining the atomic composition; then, the specific molecular structure of each component can be confirmed by nuclear magnetic resonance (NMR) spectroscopy results.

[0099] As an example, ion chromatography (IC) can be used to test the content of electrolyte salts in an electrolyte solution, while gas chromatography-mass spectrometry (GC-MS) can be used to test the content of various components in an organic solvent.

[0100] Electrolyte can be obtained by sampling and analyzing during the preparation process, or by disassembling and centrifuging the prepared lithium metal battery cells after discharge.

[0101] In some alternative embodiments, the conductivity of the electrolyte is from 1 mS / cm to 10 mS / cm.

[0102] Optionally, the conductivity of the electrolyte can be any value or a range thereof from 1.0 mS / cm, 1.5 mS / cm, 2.0 mS / cm, 2.5 mS / cm, 3.0 mS / cm, 3.5 mS / cm, 4.0 mS / cm, 4.5 mS / cm, 5.0 mS / cm, 5.5 mS / cm, 6.0 mS / cm, 6.5 mS / cm, 7.0 mS / cm, 7.5 mS / cm, 8.0 mS / cm, 8.5 mS / cm, 9.0 mS / cm, 9.5 mS / cm, and 10.0 mS / cm. In some optional embodiments, the conductivity of the electrolyte is from 2 mS / cm to 8 mS / cm.

[0103] The conductivity of the electrolyte reflects the migration ability of lithium ions within the electrolyte. This conductivity can reduce the internal resistance of lithium metal battery cells, increase the charge transfer rate, improve kinetic performance, and enable lithium metal battery cells to maintain high energy output at high current densities. This conductivity also helps reduce uneven current distribution and improve the cycle life of lithium metal battery cells.

[0104] 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.

[0105] In some optional embodiments, the viscosity of the electrolyte is from 1 mPa·s to 10 mPa·s.

[0106] Optionally, the viscosity of the electrolyte can be any value or a range thereof from 1.0 mPa·s, 1.5 mPa·s, 2.0 mPa·s, 2.5 mPa·s, 3.0 mPa·s, 3.5 mPa·s, 4.0 mPa·s, 4.5 mPa·s, 5.0 mPa·s, 5.5 mPa·s, 6.0 mPa·s, 6.5 mPa·s, 7.0 mPa·s, 7.5 mPa·s, 8.0 mPa·s, 8.5 mPa·s, 9.0 mPa·s, 9.5 mPa·s, and 10.0 mPa·s. In some optional embodiments, the viscosity of the electrolyte is from 1.5 mPa·s to 8.5 mPa·s.

[0107] The viscosity of the electrolyte affects the diffusion rate of lithium ions within the electrolyte. Electrolyte viscosities within the aforementioned range help increase the lithium ion diffusion coefficient, thereby accelerating charge transfer and improving the kinetic performance of lithium metal battery cells. Electrolytes with these viscosities also help balance the lithium deposition process, reduce dendrite formation, and improve the stability and cycle life of lithium metal battery cells.

[0108] 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.

[0109] As an 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.

[0110] [Negative electrode plate]

[0111] In some optional embodiments, the lithium metal battery cell includes a negative electrode sheet, the negative electrode sheet includes a composite lithium layer, the composite lithium layer includes lithium metal and carbon quantum dots, the lithium metal is a continuous phase and the carbon quantum dots are a dispersed phase.

[0112] In the embodiments of this application, the composite lithium layer of the negative electrode sheet contains lithium metal material and carbon quantum dots. Carbon quantum dots are a zero-dimensional material with abundant edge defects and lithium affinity. The carbon quantum dots uniformly dispersed in the lithium metal serve as uniform heterogeneous nucleation sites, which can also reduce the nucleation potential of lithium ions, which is beneficial to the deposition and solvation of lithium ions, thereby reducing the risk of lithium dendrite growth and improving the reliability of lithium metal batteries. The carbon quantum dots uniformly dispersed in the lithium metal can then uniformly attach to the ultrathin lithium metal battery electrochemical interface (SEI film), guiding the uniform and dense nucleation and deposition of lithium, reducing the polarization of the anode / electrolyte interface, and improving the cycle capacity retention rate of lithium metal batteries. During the electrochemical cycling process of lithium metal batteries, as metallic lithium is consumed, carbon quantum dots participate in the formation of the SEI film in situ, which can serve as a fast diffusion channel for lithium ions and enhance the ion conduction capacity of the SEI film, which is beneficial to improving the kinetic performance of lithium metal batteries.

[0113] Furthermore, in the later stages of electrochemical cycling of lithium metal batteries, the surface of the lithium metal anode still contains uniform carbon quantum dots, which allows for the regulation of lithium metal nucleation behavior throughout the entire life cycle of the lithium metal battery.

[0114] In some optional embodiments, the mass content of carbon quantum dots in the composite lithium layer is 0.01% to 10%. Therefore, carbon quantum dots can reduce the nucleation potential of lithium ions, which is beneficial to the deposition and solvation of lithium ions and improves the reliability of lithium metal batteries; the uniform attachment of carbon quantum dots to the ultrathin lithium metal battery electrochemical interface (SEI film) improves the cycle capacity retention and kinetic performance of lithium metal batteries.

[0115] The mass content of carbon quantum dots in the composite lithium layer can be observed using a scanning electron microscope to examine the distribution of carbon quantum dots in the metal layer. Combined with energy-dispersive X-ray spectroscopy (EDS), the composition and mass of the particles can be determined.

[0116] Optionally, any value or a range of combinations thereof from 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, and 2.0%.

[0117] In some optional embodiments, the mass content of carbon quantum dots in the composite lithium layer is 0.5% to 2%. This further improves the cycle capacity retention and kinetic performance of the lithium metal battery.

[0118] In some optional embodiments, the carbon quantum dots include one or more of graphene quantum dots, graphene oxide quantum dots, fluorinated graphene quantum dots, chlorinated graphene quantum dots, carboxylated graphene quantum dots, hydroxylated graphene quantum dots, and aminographene quantum dots. The above-mentioned types of carbon quantum dots can improve the reliability of lithium metal batteries, and enhance their cycle capacity retention and kinetic performance.

[0119] In some alternative embodiments, the thickness of the composite lithium layer is 2 to 100 micrometers.

[0120] Optionally, any value or a range of combinations thereof from 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, and 100μm.

[0121] The thickness of the composite lithium layer is within the above range, and it includes uniformly distributed carbon quantum dots. During the charging and discharging process of the lithium metal battery, lithium can still be uniformly deposited due to repeated lithium deposition and stripping, which improves the cycle life and reliability of the lithium metal battery.

[0122] An exemplary test method for the thickness of the composite lithium layer is as follows: Take a sample with a length of 50 mm and a width of 10 mm; take 5 points evenly on the sample (for example, take one point every 5 mm along the length of the sample), and use a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to test the thickness of the composite lithium layer at the 5 different locations, and take the average value as the thickness of the composite lithium layer.

[0123] In some optional embodiments, the thickness of the composite lithium layer is 10–20 micrometers. This further improves the cycle life and reliability of the lithium metal battery.

[0124] In some optional embodiments, the thickness of the negative electrode sheet can be 2 to 200 micrometers, optionally 6 to 120 micrometers, or optionally 140 micrometers.

[0125] In some alternative embodiments, the negative electrode includes a negative current collector and a composite lithium layer disposed on at least one side of the negative current collector. Therefore, this type of negative electrode is advantageous in balancing the energy density and kinetic performance of lithium metal batteries.

[0126] In some optional embodiments, the thickness of the negative electrode current collector can be 0 to 20 micrometers, and optionally 4 to 12 micrometers.

[0127] The negative electrode current collector can be a metallic material, including but not limited to one or an alloy of copper, nickel, lithium, iron, or stainless steel. It is understood that any material can be used for the negative electrode current collector to support the composite lithium foil. In some optional embodiments, the negative electrode sheet is a composite lithium layer, which may not contain a negative electrode current collector.

[0128] In some alternative implementations, the negative electrode current collector includes one or more of elemental lithium and lithium alloys.

[0129] In some alternative 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, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, aluminum mesh, copper foam, nickel foam, and aluminum foam. A composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Examples of polymer substrates include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0130] This application provides a method for preparing a negative electrode sheet for lithium metal batteries, comprising:

[0131] Lithium metal and carbon quantum dots are heated in an inert atmosphere to form a mobile phase of lithium metal;

[0132] Carbon quantum dots are dispersed in the mobile phase of lithium metal to obtain a uniformly dispersed mixture;

[0133] The mixture is cold-pressed to obtain a composite lithium layer.

[0134] In this embodiment, the melting point of lithium metal is generally 180.5°C, while the melting point of carbon quantum dots is generally much higher than that of lithium metal. By dispersing carbon quantum dots in the mobile phase of lithium metal, carbon quantum dots can be uniformly dispersed in lithium metal to form a composite lithium layer. The preparation method of this application is simple, easy to operate, has good repeatability, low cost, and is environmentally friendly, making it suitable for industrial production.

[0135] Carbon quantum dots uniformly dispersed in lithium metal serve as uniform heterogeneous nucleation sites, reducing the nucleation potential of lithium ions and facilitating lithium ion deposition and solvation. This reduces the risk of lithium dendrite growth and improves the reliability of lithium metal batteries. Furthermore, these uniformly dispersed carbon quantum dots can subsequently adhere uniformly to the ultrathin electrochemical interface (SEI film) of lithium metal batteries, guiding uniform and dense lithium nucleation and deposition, reducing anode / electrolyte interface polarization, and improving the cycle capacity retention of lithium metal batteries. During electrochemical cycling, as metallic lithium is consumed, carbon quantum dots participate in the formation of the SEI film in situ, acting as a rapid diffusion channel for lithium ions and enhancing the ion conductivity of the SEI film, thus improving the kinetic performance of lithium metal batteries.

[0136] In some alternative embodiments, the inert atmosphere may include an inert gas, such as nitrogen or argon.

[0137] In some optional embodiments, the target heating temperature can be 180.5°C-220°C. Carbon quantum dots can be dispersed in the mobile phase of lithium metal by stirring or other operations. The stirring time can be 0.5-1.5 hours.

[0138] In some optional embodiments, before cold-pressing the mixture to obtain the composite lithium layer, the following steps are included:

[0139] Cool the mixture.

[0140] In some alternative embodiments, the mixture is cold-pressed to obtain a composite lithium layer, specifically including:

[0141] The mixture is cold-pressed on a precision roller press to obtain a composite lithium layer. The gap of the precision roller press can be 2-100 micrometers.

[0142] In some optional embodiments, the method for preparing the negative electrode sheet further includes:

[0143] The composite lithium layer is rolled and pressed with the negative electrode current collector to obtain the negative electrode sheet.

[0144] [Positive electrode plate]

[0145] In some alternative embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a positive active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0146] The type of positive electrode active material can be selected according to the type of lithium metal battery cell, and this application embodiment does not limit this.

[0147] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material is disposed on either or both of the two opposite surfaces of the positive current collector.

[0148] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0149] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphate include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0150] Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0151] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content represents the initial state of the material, i.e., the state before material addition. As the positive electrode active material is applied to the battery cell, the molar Li content changes after charge-discharge cycles. Similarly, the molar oxygen (O) content in the examples of positive electrode active materials in this disclosure is only a theoretical value. Lattice oxygen release causes changes in the molar O content, leading to fluctuations in the actual molar O content.

[0152] In some alternative embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, the surface of the foamed metal may or may not contain a positive electrode active material. As an example, a positive electrode active material is filled and / or deposited within the foamed metal.

[0153] In some alternative embodiments, the positive electrode film layer may also optionally 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.

[0154] In some alternative embodiments, the positive electrode film layer may also optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0155] In some alternative embodiments, the positive current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. 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).

[0156] 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, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0157] [Isolation Component]

[0158] In some embodiments, the electrode assembly further includes a spacer disposed between the positive electrode and the negative electrode.

[0159] In some embodiments, the separator can be a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0160] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. 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. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0161] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0162] The preparation methods of lithium metal battery cells are well known. In some optional embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a lithium 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 electrolyte. After vacuum sealing, settling, formation, and shaping processes, a lithium metal battery cell is obtained. Multiple lithium metal battery cells can be further connected in series, parallel, or a combination thereof to form a lithium metal battery cell module. Multiple lithium metal battery cell modules can also be connected in series, parallel, or a combination thereof to form a lithium metal battery cell pack. In some optional embodiments, multiple lithium metal battery cells can also be directly assembled into a lithium metal battery cell pack.

[0163] Electrical appliances

[0164] This application provides an electrical device, including the battery device described above.

[0165] Lithium metal battery cells can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices can be, but are not limited to, mobile devices (such as 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 trains, ships and satellites, energy storage systems, etc.

[0166] Electrical devices can be selected from lithium metal battery cells, lithium metal battery cell modules, or lithium metal battery cell packs according to their usage requirements.

[0167] Figure 5 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, lithium metal battery packs or lithium metal battery modules can be used.

[0168] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can utilize lithium metal battery cells as their power source.

[0169] Example

[0170] The following embodiments describe the disclosure of this application 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 the disclosure of this application. 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.

[0171] Example 1

[0172] Electrolyte preparation:

[0173] Preparation of electrolyte stock solution: Lithium salt LiFSI, dimethyl ether (DME), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) were mixed evenly in a molar ratio of 1:1.2:3 to form a locally highly concentrated stock solution 1, which is a mixture without carbon quantum dots. Then, 0.001g of carboxylated graphene quantum dots were mixed with stock solution 1 to prepare 10g of electrolyte. After thoroughly stirring and mixing the electrolyte, a light black transparent solution was formed.

[0174] Preparation of lithium metal batteries:

[0175] Positive electrode preparation: The positive electrode active material, lithium nickel cobalt manganese oxide (LiNiO), is prepared... 0.8 Co 0.1 Mn 0.1 O2(NCM 811 The conductive agent acetylene black and polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) solvent was added and stirred until the system was homogeneous to obtain the positive electrode slurry. The solid content of the positive electrode slurry was 70%. The positive electrode slurry was then weighed at an area density of 12.5 mg / cm³. 2 The load is evenly coated on both sides of the positive current collector aluminum foil, dried at room temperature, transferred to an oven for further drying, and then cut into 40mm*50mm rectangles as positive electrode sheets.

[0176] Separation membrane: Select a 12-micron thick polyethylene porous membrane and cut it into a 45mm*55mm rectangle for later use.

[0177] Negative electrode preparation: A 50μm lithium foil is rolled onto a 12μm copper foil and then cut into a 41mm*51mm rectangle as the negative electrode.

[0178] Assembly: A pre-cut positive electrode is matched with two pre-cut negative electrodes, separated by the aforementioned separator. The electrodes are then wrapped in an aluminum-plastic film bag to form a stacked dry cell. 0.3g of the prepared electrolyte is injected, and the aluminum-plastic film bag is vacuum-sealed using heat pressing. After standing at room temperature for at least 6 hours, cycle testing can begin. The rated capacity of the stacked battery prepared in this way is 70mAh.

[0179] Examples 2 to 5

[0180] Examples 2-5 are the same as Example 1, except that the mass content of carbon quantum dots in the electrolyte is different, as detailed in Table 2.

[0181] Examples 6-10

[0182] Examples 6-10 are the same as Example 1, except that the types of carbon quantum dots in the electrolyte are different, as detailed in Table 2.

[0183] Examples 11-18

[0184] Different electrolytes were prepared as mother liquors. The corresponding mother liquors were mixed with carbon quantum dots and stirred thoroughly to form a light black transparent substance, as shown in Table 1.

[0185] Table 1

[0186] name lithium salts ether solvents diluent Mole ratio Mother liquor 2 LiFSI DME TTE 1:1:3 Mother liquor 3 LiTFSI DME TTE 1:1.2:3 Mother liquor 4 LiFSI DEE TTE 1:1.2:3 Mother liquor 5 LiFSI DME Bz 1:1.2:3 Mother liquor 6 LiFSI DME Bz 1:1:3 Mother liquor 7 LiTFSI DME Bz 1:1.2:3 Mother liquor 8 LiFSI DEE Bz 1:1.2:3

[0187] Examples 11 to 18 differ from Example 1 in that the mother liquor used to prepare the electrolyte is different. The test results are shown in Table 2.

[0188] Example 19

[0189] Example 19 differs from Example 1 in that the preparation of the negative electrode sheet is different, and the composition of the negative electrode sheet is different. Preparation of the negative electrode sheet: a. Lithium metal and carboxylated graphene quantum dots are placed in an argon-protected reactor at a mass ratio of 99.5:0.5 and heated to 185°C, then stirred at a constant temperature until homogeneous;

[0190] b. Cool the stirred composite lithium metal;

[0191] c. The cooled composite lithium metal is cold-pressed into 50-micron composite lithium foil on a precision roller press;

[0192] d. The composite lithium foil and 12-micron copper foil were rolled together to form a negative electrode sheet, which was then cut into rectangles of 41mm*51mm for later use. The test results are shown in Table 3.

[0193] Example 20

[0194] Example 20 differs from Example 1 in that the negative electrode sheet is prepared differently, and the mass content of carboxylated graphene quantum dots in the composite lithium foil is 1%. The test results are shown in Table 3.

[0195] Comparative Example 1

[0196] This comparative example is the same as Example 1, except that only mother liquor 1 is used for lithium metal battery injection and subsequent testing, and no graphene quantum dots are added.

[0197] Test section

[0198] 1) Lithium metal battery cycle performance test

[0199] The fabricated stacked cells were used, and the ambient temperature was set to 25°C. Charge and discharge cycles were performed at a rate of 0.2C (14mA) and 1C (70mA). The cutoff voltages for charging and discharging were set to 4.3V and 2.8V, respectively. A constant current-constant voltage charging method was used. Specifically, after the 0.2C constant current charging reached the cutoff voltage of 4.3V, constant voltage charging at 4.3V was continued until the current decreased to 0.1C (7mA). The number of cycles when the discharge capacity decreased to 80% of the initial discharge capacity was considered the cycle life of the lithium metal battery.

[0200] 2) Initial rate test of lithium metal batteries

[0201] Take the fabricated laminated battery cells and set the ambient temperature to 25℃. Use a charging rate of 0.2C (14mA) and discharge rates of 0.2C (14mA), 0.5C (35mA), 1C (70mA), 2C (140mA), and 4C (280mA) for one charge-discharge cycle. Set the cutoff voltages for charging and discharging to 4.3V and 2.8V, respectively. Use a constant current-constant voltage charging method during the charging process, and use the capacity at the 4C discharge rate as the initial discharge capacity. Specifically, after the 0.2C constant current charging reaches the cutoff voltage of 4.3V, continue charging at 4.3V constant voltage until the current decays to 0.1C (7mA).

[0202] 3) Rate test of lithium metal battery after 200 cycles

[0203] Take the fabricated stacked cells and set the ambient temperature to 25℃. Perform 200 charge-discharge cycles at a rate of 0.2C (14mA) and 1C (70mA). Then, conduct a rate test, using a charging rate of 0.2C (14mA) and discharging rates of 0.2C (14mA), 0.5C (35mA), 1C (70mA), 2C (140mA), and 4C (280mA). The cutoff voltages for charging and discharging are set to 4.3V and 2.8V, respectively. A constant current-constant voltage charging method is used during the charging process. The capacity at the 4C discharge rate is taken as the discharge capacity after 200 cycles to evaluate the rate capability of the lithium metal battery. Specifically, after the 0.2C constant current charging reaches the cutoff voltage of 4.3V, the constant voltage charging is continued at 4.3V until the current decays to 0.1C (7mA).

[0204] The test results are shown in Table 2.

[0205]

[0206]

[0207] As shown in Table 2, compared with Comparative Example 1, Examples 1-5 demonstrate that carboxyl-based graphene quantum dots can effectively improve the cycle performance and rate performance in the later stages of lithium metal batteries. The reason for this is that there is less accumulation of electrolyte byproducts on the surface of the negative electrode in the battery cell, resulting in less polarization deterioration; therefore, the initial rate performance of the examples and the comparative example is basically the same. Furthermore, the content of carboxyl-based graphene quantum dots can be selected as 0.1 mg / mL.

[0208] As can be seen from Examples 6-10 and Comparative Example 1, the different types of carbon quantum dots used in this invention are also beneficial to the electrochemical performance of lithium metal batteries, and can improve the cycle performance and rate performance of lithium metal batteries.

[0209] As can be seen from Examples 11-18 and Comparative Example 1, the carbon quantum dots used in this invention have good compatibility with various local high-concentration electrolytes, which can ensure the long cycle and high-rate operation of lithium metal batteries.

[0210] Compared with Example 1, Examples 19-20 show that the negative electrode containing carbon quantum dots, when paired with different types of locally high-concentration electrolytes containing carbon quantum dots, all exhibit good compatibility, improving the cycle performance and high-rate capability of lithium metal batteries, and enhancing the electrochemical performance of lithium metal batteries.

[0211] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium metal battery cell, characterized in that, The electrolyte comprises a lithium salt, carbon quantum dots, an ether solvent for dispersing and / or dissociating the lithium salt, and a diluent for diluting the ether solvent; the lithium salt is immiscible with the diluent.

2. The lithium metal battery cell of claim 1, wherein, The electrolyte satisfies one or more of the following conditions: 1) the concentration of the carbon quantum dots in the electrolyte is 0.01 mg / mL to 2 mg / mL; 2) the mass percentage of the lithium salt in the electrolyte is 20% to 28%.

3. The lithium metal battery cell according to claim 1 or 2, c h a r a c t e r i z e d in that, The electrolyte satisfies one or more of the following conditions: 1) the concentration of the carbon quantum dots in the electrolyte is 0.1 mg / mL to 1 mg / mL; 2) the mass percentage of the lithium salt in the electrolyte is 24% to 25%.

4. The lithium metal battery cell according to any one of claims 1 to 3, characterized in that The molar ratio of the lithium salt, the ether solvent, and the diluent is 1:(0.4-3):(1-5).

5. The lithium metal battery cell according to any one of claims 1 to 4, characterized in that, The molar ratio of the lithium salt, the ether solvent, and the diluent is 1:(1.2-2):(3-3.5).

6. The lithium metal battery cell according to any one of claims 1 to 5, characterized in that, The electrolyte satisfies one or more of the following conditions: 1) the carbon quantum dots comprise one or more of graphene quantum dots, graphene oxide quantum dots, fluorinated graphene quantum dots, chlorinated graphene quantum dots, carboxylated graphene quantum dots, hydroxylated graphene quantum dots, and aminated graphene quantum dots; 2) the lithium salt comprises one or more of lithium bisfluorosulfonylimide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bisoxalate borate, lithium difluorobisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate; 3) the ether solvent comprises one or more of diethyl ether, dipropyl ether, ethyl propyl ether, methyl butyl ether, dibutyl ether, ethyl butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol methyl ethyl ether, propylene glycol diethyl ether, butylene glycol dimethyl ether, butylene glycol methyl ethyl ether, butylene glycol diethyl ether, tetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxolane, tetrahydropyran, 1,3-dioxane, and 1,4-dioxane. 4) the diluent comprises one or more of benzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluoromethylbenzene, trifluoromethoxybenzene, decafluoropentane, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-dimethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(difluoromethoxy)ethane, 1,2-bis(trifluoromethoxy)ethane, 1,2-diethoxy-1,1,2,2-tetrafluoroethane, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl) ether, bis(2,2-difluoroethyl) ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether, and bis(1,1,2,2-tetrafluoroethyl) ether.

7. The lithium metal battery cell according to any one of claims 1 to 6, characterized in that The electrolyte satisfies one or more of the following conditions: 1) the conductivity of the electrolyte is 1 mS / cm to 10 mS / cm; 2) the viscosity of the electrolyte is 1 mPa-s to 10 mPa-s.

8. The lithium metal battery cell according to any one of claims 1 to 7, characterized in that The electrolyte satisfies one or more of the following conditions: 1) the conductivity of the electrolyte is 2 mS / cm to 8 mS / cm; 2) the viscosity of the electrolyte is 1.5 mPa-s to 8.5 mPa-s.

9. The lithium metal battery cell of any one of claims 1-8, wherein, The lithium metal battery cell comprises a negative electrode sheet, the negative electrode sheet comprises a composite lithium layer, the composite lithium layer comprises lithium metal and additional carbon quantum dots, the lithium metal is a continuous phase, and the carbon quantum dots are a dispersed phase.

10. The lithium metal battery cell of claim 9, wherein, The composite lithium layer satisfies one or more of the following conditions: 1) the mass content of the carbon quantum dots in the composite lithium layer is 0.01% to 10%; 2) the thickness of the composite lithium layer is 0.2 to 100 microns.

11. The lithium metal battery cell of claim 9 or 10, wherein, The composite lithium layer satisfies one or more of the following conditions: 1) the mass content of the carbon quantum dots in the composite lithium layer is 0.5% to 2%; 2) the thickness of the composite lithium layer is 5 to 20 microns.

12. The lithium metal battery cell of any one of claims 9-11, wherein, The negative electrode sheet comprises a negative electrode current collector and the composite lithium layer disposed on at least one side of the negative electrode current collector.

13. An electrolyte for a lithium metal battery cell, comprising a lithium salt, carbon quantum dots, an ether solvent for dispersing and / or dissociating the lithium salt, and a diluent for diluting the ether solvent, wherein the lithium salt and the diluent are immiscible.

14. A battery device characterized by comprising: A lithium metal battery cell according to any one of claims 1 to 12 or a battery cell prepared by the electrolyte of claim 13.

15. An electrical device, comprising: A battery device according to claim 14.

Images