Negative pole piece for lithium battery, negative pole piece preparation method and battery monomer

Abstract

The invention discloses a negative pole piece for a lithium battery, a negative pole piece preparation method and a battery monomer. The negative pole piece comprises a negative current collector; and the artificial interface protection layer is positioned on at least one side of the negative electrode current collector and comprises a composite framework structure consisting of lithium fluoride and a lithiated carbon-based compound. The negative pole piece can fully utilize the advantages of low electrode potential and high theoretical specific capacity when metal lithium is used as a negative pole material, and the cycle performance and the safety performance of a battery monomer are improved on the basis.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a negative electrode sheet for lithium batteries, a method for preparing the negative electrode sheet, and a battery cell. Background Technology

[0002] In recent years, with the increasingly wide application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, and many other fields. For the future development of electronic devices and electric vehicles, higher requirements have been placed on the energy density and safety of secondary batteries.

[0003] Lithium metal possesses an extremely low electrode potential (−3.04 V vs. standard hydrogen electrode) and an extremely high theoretical specific capacity (3860 mAh g⁻¹). −1 It is an ideal negative electrode material for the next generation of high-energy-density secondary batteries.

[0004] However, when lithium metal is used as a negative electrode material in battery cells, it exhibits high reactivity and a lack of a "host". Due to its high reactivity, lithium metal is prone to irreversible side reactions with the electrolyte, forming an unstable solid electrolyte interphase (SEI) layer, which leads to capacity decay in the battery cell. Due to its lack of a "host", lithium metal is prone to uneven deposition during charging and discharging, which can easily form lithium dendrites that pierce the separator, causing short circuits or even thermal runaway in the battery cell. Repeated lithium deposition / stripping processes can also cause mechanical fatigue of lithium metal, leading to cracks and structural collapse inside the electrode, exacerbating the loss of active lithium in the battery cell and increasing the interfacial impedance of the battery cell, thereby reducing the cycle performance and safety performance of the battery cell. Summary of the Invention

[0005] This application provides a negative electrode sheet for lithium batteries, a method for preparing the negative electrode sheet, and a battery cell. The negative electrode sheet can suppress lithium dendrite growth and interfacial side reactions. The battery cell using the above-mentioned negative electrode sheet has good cycle performance and safety performance.

[0006] The first aspect of this application provides a negative electrode sheet for a lithium battery, including a negative current collector and an artificial interface protective layer located on at least one side of the negative current collector, the artificial interface protective layer including a composite framework structure composed of lithium fluoride and lithium carbon-based compounds.

[0007] Lithium fluoride has a low lithium-ion diffusion barrier, enabling rapid short-range ion transport; lithium-based carbon compounds facilitate long-range lithium-ion and electron transport along the carbon layer. The composite framework structure composed of lithium fluoride and lithium-based carbon compounds can achieve the synergistic effect of the two, which can significantly improve the lithium-ion transport kinetics at the negative electrode interface, increase the transport efficiency of lithium ions between metallic lithium and the electrolyte layer, and improve the cycle performance of the battery cell.

[0008] Furthermore, this composite framework structure enables uniform distribution of lithium fluoride, providing a stable microenvironment for lithium-ion deposition. This facilitates uniform nucleation of lithium on the surface, effectively suppresses the growth of lithium dendrites, prevents short circuits caused by lithium dendrites penetrating the separator, and improves the safety performance of the battery cell. Meanwhile, lithium fluoride and lithium-based carbon compounds, based on their chemical inertness, can effectively suppress interfacial side reactions, improve the chemical stability and mechanical strength of the negative electrode, and further enhance the cycle performance of the battery cell.

[0009] In addition, the high thermal stability of lithium fluoride and lithium carbon-based compounds helps to suppress thermal runaway behavior and further improve the safety performance of battery cells.

[0010] Therefore, the negative electrode sheet provided in this application can make full use of the advantages of low electrode potential and high theoretical specific capacity when lithium metal is used as a negative electrode material, and on this basis improve the cycle performance and safety performance of the battery cell.

[0011] In some embodiments, the negative electrode further includes a lithium-based metal film layer located between the negative electrode current collector and the artificial interface protective layer, the lithium-based metal film layer comprising elemental lithium.

[0012] By setting a lithium-based metal film layer containing elemental lithium between the negative electrode current collector and the artificial interface protective layer, the characteristics of the artificial interface protective layer can be utilized to further reduce the occurrence of interfacial side reactions and lithium dendrite formation, thereby improving the cycle performance and safety performance of the battery cell.

[0013] In some embodiments, the lithium-based metal film layer further includes a composite framework structure composed of lithium fluoride and lithium-based carbon compounds, which is dispersed within the lithium-based metal film layer. Based on a lithium-based metal film layer containing elemental lithium placed between the negative electrode current collector and the artificial interface protective layer, a composite framework structure composed of lithium fluoride and lithium-based carbon compounds can be added to the lithium-based metal film layer. This composite framework structure not only forms an interface protective layer on the surface of the lithium-based metal film layer, reducing interfacial side reactions and lithium dendrite formation, but also provides stress support for elemental lithium within the lithium-based metal film layer, promoting rapid transport of lithium atoms and vacancies, reducing negative electrode pulverization and cracking caused by lithium stripping or deposition. This helps the negative electrode to possess both good interfacial stability and mechanical properties, effectively improving the cycle performance of the battery cell.

[0014] In some embodiments, the lithium-based metal film layer further includes a Li-M alloy, where M includes one or more of silver, calcium, zinc, aluminum, magnesium, and tin.

[0015] In some embodiments, the lithium-based metal film layer further includes one or more of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride.

[0016] In some embodiments, the lithium-based metal film layer further includes one or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride.

[0017] In some implementations, the artificial interface protective layer also includes elemental lithium, with the composite framework structure dispersed within the elemental lithium.

[0018] In the negative electrode sheet, an additional lithium-based metal film layer can be eliminated. Instead, an artificial interface protective layer is set, which includes a composite framework structure composed of lithium fluoride and lithium-based carbon compounds, as well as elemental lithium. The composite framework structure is dispersed in the elemental lithium. That is, the artificial interface protective layer can serve as the negative electrode active material layer of the negative electrode sheet. The negative electrode active material layer can use the composite framework structure to further provide stress support for the elemental lithium, reduce the negative electrode pulverization and cracking caused by lithium stripping or deposition, improve the mechanical strength and structural stability of the negative electrode, and further improve the cycle performance of the battery cell.

[0019] In some embodiments, the artificial interface protective layer further includes a Li-M alloy, where M includes one or more of silver, calcium, zinc, aluminum, magnesium, and tin.

[0020] In some embodiments, the artificial interface protective layer further includes one or more of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride.

[0021] In some embodiments, the artificial interface protective layer further includes one or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride.

[0022] Li-M alloys help improve the transport rate of lithium atoms and vacancies inside the negative electrode, enhance the density and uniformity of lithium deposition, thereby suppressing the growth of lithium dendrites. They also help to further improve the electronic conductivity of the negative electrode, thus improving the cycle performance of the battery cell. In addition, Li-M alloys have good ductility, which helps to improve the mechanical strength of the negative electrode, further improving the cycle performance of the battery cell.

[0023] One or more nitrides selected from magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride help improve the ionic conductivity of the negative electrode. Furthermore, nitrides have high chemical inertness, which can further reduce the occurrence of interfacial side reactions and improve the cycle performance of the battery cell.

[0024] One or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride can help increase the density of metal nucleation sites on the negative electrode, improve the conductivity of the negative electrode, and inhibit the growth of lithium dendrites, thereby further improving the cycle performance and safety performance of the battery cell.

[0025] In some implementations, the thickness of the artificial interface protective layer is 1. 100 .

[0026] The thickness of the artificial interface protective layer is 1 100 This helps maintain the high energy density characteristics of the negative electrode without significantly increasing the overall weight or volume of the battery cell.

[0027] A second aspect of this application provides a method for preparing a negative electrode sheet, comprising: An interface protective layer slurry is provided, which includes fluorocarbon materials, alloy modifiers, and heteroatom modifiers. An interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, wherein the artificial interface protective layer includes a composite framework structure composed of lithium fluoride, lithium carbon-based compounds, lithium alloys, and heteroatoms.

[0028] In some embodiments, an interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, comprising: Lithium-based metal pastes, including elemental lithium, are provided; A lithium-based metal slurry is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. An interface protective layer slurry is coated onto the surface of a lithium-based metal film layer facing away from the negative electrode current collector to obtain a negative electrode sheet comprising a lithium-based metal film layer and an artificial interface protective layer, wherein the lithium-based metal film layer is located between the negative electrode current collector and the artificial interface protective layer.

[0029] In some embodiments, a lithium-based metal slurry is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector comprising a lithium-based metal film layer, including: We provide fluorocarbon materials, alloy modifiers, and heteroatom modifiers. A first molten mixture is obtained by melting and mixing lithium-based metal slurry, fluorinated carbon material, alloy modifier, and heteroatom modifier. The first molten mixture is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. The lithium-based metal film layer also includes a composite framework structure composed of lithium fluoride, lithium carbon-based compounds, lithium alloys, and heteroatoms. The composite framework structure is dispersed in the lithium-based metal film layer.

[0030] In some embodiments, an interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, comprising: Provides elemental lithium; Elemental lithium and interface protective layer slurry are melt-mixed to obtain a second melt mixture; The second molten mixture is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer; wherein the artificial interface protective layer also includes elemental lithium, and the composite framework structure is dispersed in the elemental lithium.

[0031] In some embodiments, the alloy modifier includes at least one of nano silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride.

[0032] In some embodiments, the heteroatom modifier includes at least one of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride.

[0033] In some embodiments, the fluorinated carbon material includes at least one of fluorinated graphite, fluorinated graphene, fluorinated carbon fiber, fluorinated carbon nanotubes, and fluorinated fullerene.

[0034] The third aspect of this application provides a battery cell, which includes an electrode assembly, an electrolyte, and a separator. The electrode assembly includes a positive electrode and a negative electrode, wherein the negative electrode is the negative electrode of the first aspect, or a negative electrode obtained by the method of the second aspect.

[0035] The fourth aspect of this application provides a battery device, which includes a negative electrode sheet of the first aspect, or a negative electrode sheet obtained by the method of the second aspect, or a battery cell of the third aspect.

[0036] The fifth aspect of this application provides an electrical device, which includes a negative electrode sheet of the first aspect, or a negative electrode sheet obtained by the method of the second aspect, or a battery cell of the third aspect, or a battery device of the fourth aspect. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced 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 these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of a negative electrode structure provided in an embodiment of this application.

[0039] Figure 2 This is a schematic diagram of another negative electrode structure provided in the embodiments of this application.

[0040] Figure 3 This is a schematic diagram of another negative electrode structure provided in the embodiments of this application.

[0041] Figure 4 This is a schematic diagram of another negative electrode structure provided in the embodiments of this application.

[0042] Figure 5 The image shows the C1s X-ray photoelectron spectra of the fluorinated graphite material and the negative electrode sheet provided in Example 1.

[0043] Figure 6 The image shows the F1s X-ray photoelectron spectra of the fluorinated graphite material and the negative electrode sheet provided in Example 1.

[0044] Figure 7 This is an SEM image of the negative electrode sheet provided in Example 1.

[0045] Figure 8 This is the EDS elemental distribution diagram of the negative electrode sheet provided in Example 1.

[0046] Figure 9 This is a schematic diagram of the cycle performance of the battery cell prepared in Example 1 at 25 °C and 0.1 C.

[0047] Figure 10 This is an SEM image of the negative electrode sheet provided in Example 2.

[0048] Figure 11 This is the EDS elemental distribution diagram of the negative electrode sheet provided in Example 2. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] The embodiments of this application will be described in detail below. These embodiments should not be construed as limiting the scope of this application.

[0051] As used in this application, the terms “comprising,” “containing,” and “including” are used in their open, non-restrictive sense.

[0052] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0053] In the detailed description and claims, a list of items connected by the terms "one or more of," "one or more of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0054] Lithium metal possesses an extremely low electrode potential (−3.04 V vs. standard hydrogen electrode) and an extremely high theoretical specific capacity (3860 mAh g⁻¹). −1Lithium metal is an ideal anode material for next-generation high-energy-density lithium-ion batteries. However, due to its high reactivity, lithium metal anodes are prone to irreversible side reactions with the electrolyte, forming an unstable solid-state electrolyte interface layer and causing capacity decay. Furthermore, due to the lack of a host cell in lithium metal anodes, uneven lithium deposition occurs during battery charging and discharging, easily forming lithium dendrites. These dendrites can pierce the separator, causing short circuits and even thermal runaway. Moreover, repeated lithium deposition / stripping processes can induce mechanical fatigue in lithium metal, leading to internal cracks and structural collapse, resulting in active lithium loss and increased interfacial impedance. These drawbacks have prevented the large-scale commercial application of lithium metal anodes to date.

[0055] To address these issues, researchers have proposed various strategies, including multidimensional frameworks, electrolyte design adjustments, solid-state electrolyte modifications, and the construction of artificial interface layers. Among these, constructing artificial interface layers is one of the most effective research directions. For example, introducing LiF-containing interface layers. LiF exhibits good chemical and mechanical stability, which can suppress interfacial side reactions and lithium dendrite growth. However, the ionic conductivity within LiF grains is extremely low (approximately 10⁻⁶). −13 S cm −1 The artificially coated large LiF crystal layer limits the interfacial ion transport efficiency and affects the cycle performance of the battery cell.

[0056] To address the aforementioned technical problems, this application provides a negative electrode sheet for lithium batteries, a method for preparing the negative electrode sheet, and a battery cell. This negative electrode sheet can fully utilize the advantages of low electrode potential and high theoretical specific capacity when lithium metal is used as the negative electrode material, and on this basis, improve the cycle performance and safety performance of the lithium metal battery cell.

[0057] The embodiments of this application will be described in detail below.

[0058] The first aspect of this application provides a negative electrode sheet for a lithium battery, including a negative electrode current collector and an artificial interface protective layer located on at least one side of the negative electrode current collector. The artificial interface protective layer includes a composite framework structure composed of lithium fluoride and lithium carbon-based compounds.

[0059] Lithium fluoride can be crystalline or amorphous. Crystalline and / or amorphous lithium fluoride has a lower lithium-ion diffusion barrier, enabling rapid short-range ion transport. Lithium-based carbon compounds help achieve long-range lithium-ion and electron transport along the carbon layer. Lithium fluoride and lithium-based carbon compounds form a composite framework structure, which can achieve the synergistic effect of the two, significantly improve the lithium-ion transport kinetics at the negative electrode interface, increase the transport efficiency of lithium ions between metallic lithium and the electrolyte layer, and improve the cycle performance of the battery cell.

[0060] Preferably, the lithium fluoride can be amorphous lithium fluoride, which has abundant lithium conduction pathways, can promote interfacial ion transport efficiency, and further improve the cycle performance of the battery cell.

[0061] Furthermore, this composite framework structure enables uniform distribution of lithium fluoride, providing a stable microenvironment for lithium-ion deposition. This facilitates uniform nucleation of lithium on the surface, effectively suppresses the growth of lithium dendrites, prevents short circuits caused by lithium dendrites penetrating the separator, and improves the safety performance of the battery cell. Meanwhile, lithium fluoride and lithium-based carbon compounds, based on their chemical inertness, can effectively suppress interfacial side reactions, improve the chemical stability and mechanical strength of the negative electrode, and further enhance the cycle performance of the battery cell.

[0062] Furthermore, compared to unevenly distributed lithium fluoride, lithium fluoride that is uniformly distributed along the carbon skeleton has a lower lithium-ion diffusion barrier, enabling more efficient short-range ion transport and thus further improving the cycle performance of the battery cell. The high thermal stability of lithium fluoride and lithium carbon-based compounds also helps to mitigate thermal runaway behavior, further enhancing the safety performance of the battery cell.

[0063] In this embodiment, the negative electrode sheet may further include a negative electrode active material layer, which may include elemental lithium, and the negative electrode active material layer may be disposed on the side of the artificial interface protective layer facing away from the negative electrode current collector, or on the side of the artificial interface protective layer facing the negative electrode current collector.

[0064] In one example, such as Figure 1 The diagram shown is a schematic diagram of a negative electrode structure provided in an embodiment of this application. The negative electrode may include at least a negative current collector and artificial interface protective layers on both sides of the negative current collector. In this example, a negative active material layer may be provided on the surface of the artificial interface protective layer facing the negative current collector and / or facing away from the negative current collector, thereby effectively utilizing the artificial interface protective layer to suppress lithium dendrite growth and interface side reactions, and improve the cycle performance and safety performance of the lithium metal battery.

[0065] In some embodiments, the negative electrode further includes a lithium-based metal film layer located between the negative electrode current collector and the artificial interface protective layer, the lithium-based metal film layer comprising elemental lithium.

[0066] A lithium-based metal film layer, including elemental lithium, can be set between the negative electrode current collector and the artificial interface protective layer to serve as the negative electrode active material layer. This allows the amorphous fluoride composed of lithium fluoride and lithium carbon-based compounds to form an interface protective layer on the surface of the negative electrode active material layer, thereby further reducing the occurrence of negative electrode interface side reactions and lithium dendrite formation, and improving the cycle performance and safety performance of the battery cell.

[0067] In one example, such as Figure 2 The diagram shown illustrates another negative electrode structure provided in this application embodiment. This negative electrode may include at least a negative current collector, an artificial interface protective layer located on both sides of the negative current collector, and a lithium-based metal film layer located between the negative current collector and the artificial interface protective layer. In this example, the artificial interface protective layer is disposed on the side of the lithium-based metal film layer facing away from the negative current collector, which can effectively reduce the occurrence of interfacial side reactions when the negative electrode contacts the electrolyte and reduce lithium dendrite formation, thereby improving the cycle performance and safety performance of the battery cell.

[0068] In some embodiments, the lithium-based metal film layer further includes a composite framework structure composed of lithium fluoride and lithium carbon-based compounds, the composite framework structure being dispersed within the lithium-based metal film layer.

[0069] A lithium-based metal film layer comprising elemental lithium can be disposed between the negative electrode current collector and the artificial interface protective layer. Furthermore, this lithium-based metal film layer also includes a composite framework structure composed of lithium fluoride and lithium-based carbon compounds. This composite framework structure is dispersed within the lithium-based metal film layer. This allows the composite framework structure, composed of lithium fluoride and lithium-based carbon compounds, to not only form an interface protective layer on the surface of the lithium-based metal film layer, reducing interfacial side reactions and lithium dendrite formation, but also to provide stress support for elemental lithium within the lithium-based metal film layer. This reduces negative electrode pulverization and cracking caused by lithium stripping or deposition, helping to give the negative electrode both good interfacial stability and mechanical properties, effectively improving the cycle performance of the battery cell. The lithium fluoride can be crystalline and / or amorphous lithium fluoride; preferably, it can be amorphous lithium fluoride, thus fully utilizing the lithium conduction pathway advantage of amorphous lithium fluoride to further improve the cycle performance of the battery cell.

[0070] In one example, such as Figure 3 The diagram shows another negative electrode structure provided in this application embodiment. This negative electrode may include at least a negative current collector, an artificial interface protective layer located on both sides of the negative current collector, and a lithium-based metal film layer located between the negative current collector and the artificial interface protective layer. In this example, the lithium-based metal film layer, in addition to containing elemental lithium, further includes a composite framework structure composed of lithium fluoride and lithium-based carbon compounds. The artificial interface protective layer is disposed on the side of the lithium-based metal film layer facing away from the negative current collector, which helps to give the negative electrode both good interface stability and mechanical properties, effectively improving the cycle performance of the battery cell.

[0071] In some embodiments, the lithium-based metal film layer further includes a Li-M alloy, where M includes one or more of silver, calcium, zinc, aluminum, magnesium, and tin.

[0072] In some embodiments, the lithium-based metal film layer further includes one or more of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride.

[0073] In some embodiments, the lithium-based metal film further includes one or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride.

[0074] In some embodiments, the artificial interface protective layer further includes elemental lithium, with the composite framework structure dispersed within the elemental lithium.

[0075] In the negative electrode sheet, there is no need to set an additional lithium-based metal film layer as the negative electrode active material layer. Instead, an artificial interface protective layer is set, which includes a composite framework structure and elemental lithium. The composite framework structure is dispersed in the elemental lithium. That is, the artificial interface protective layer can directly serve as the negative electrode active material layer of the negative electrode sheet. The negative electrode active material layer can use the composite framework structure to further provide stress support for the elemental lithium, reduce the negative electrode pulverization and cracking caused by lithium stripping or deposition, improve the mechanical strength and structural stability of the negative electrode, and further improve the cycle performance of the battery cell.

[0076] In one example, such as Figure 4 The diagram shown is a schematic diagram of another negative electrode structure provided in the embodiment of this application. The negative electrode may include at least a negative current collector and an artificial interface protective layer on both sides of the negative current collector. In this example, the artificial interface protective layer may further include elemental lithium on the basis of the composite framework structure, and the composite framework structure is dispersed in the elemental lithium, so that the composite framework structure can provide stress support for the elemental lithium on the basis of playing an interface protection role, thereby improving the mechanical strength and structural stability of the negative electrode.

[0077] In some embodiments, the artificial interface protective layer further includes a Li-M alloy, where M includes one or more of silver, calcium, zinc, aluminum, magnesium, and tin.

[0078] In some embodiments, the artificial interface protective layer further includes one or more of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride.

[0079] In some embodiments, the artificial interface protective layer further includes one or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride.

[0080] Li-M alloys help to increase the migration rate of lithium atoms and lithium vacancies in the negative electrode and provide lithium metal nucleation sites, thereby improving the density and uniformity of lithium deposition and inhibiting the growth of lithium dendrites. They also help to further improve the electronic conductivity of the negative electrode, thereby improving the cycle performance of the battery cell. In addition, Li-M alloys have good ductility and mechanical properties, which help to improve the mechanical strength of the negative electrode and further improve the cycle performance of the battery cell.

[0081] One or more nitrides selected from magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride help improve the ionic conductivity of the negative electrode. Furthermore, nitrides have high chemical inertness, which can further reduce the occurrence of interfacial side reactions and improve the cycle performance of the battery cell.

[0082] One or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride can help increase the density of metal nucleation sites on the negative electrode, improve the conductivity of the negative electrode, and inhibit the growth of lithium dendrites, thereby further improving the cycle performance and safety performance of the battery cell.

[0083] In some embodiments, the thickness of the artificial interface protective layer is 1. 100 .

[0084] The thickness of the artificial interface protective layer is 1 100 Preferably 10 50 This helps maintain the high energy density characteristics of the negative electrode without significantly increasing the overall weight or volume of the battery cell.

[0085] In some embodiments, the negative electrode current collector may include at least one of metal foil, metal foam current collector, metal mesh current collector, carbon felt current collector, carbon cloth current collector, carbon paper current collector, and composite current collector. Optionally, the metal foil may be copper foil, nickel foil, stainless steel foil, iron foil, zinc foil, titanium foil, etc.; the metal foam current collector may be copper foam, aluminum foam, zinc foam, nickel foam, etc.; and the metal mesh current collector may be copper mesh, stainless steel mesh, etc. The negative electrode current collector may also be a composite current collector formed by combining metal foil and metal foam, or a composite current collector formed by combining metal foil and metal mesh, or a composite current collector formed by combining metal foil and polymer base film; no limitation is made herein.

[0086] Secondly, embodiments of this application provide a method for preparing a negative electrode sheet, comprising: S101: Provides an interface protective layer slurry, which includes fluorocarbon materials, alloy modifiers, and heteroatom modifiers; S102: Deposit the interface protective layer slurry on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, wherein the artificial interface protective layer includes a composite framework structure composed of lithium fluoride, lithium carbon-based compound, lithium alloy and heteroatoms. The negative electrode active material of lithium metal batteries includes elemental lithium, while the interface protective layer slurry includes fluorinated carbon materials, alloy modifiers, and heteroatom modifiers. The fluorinated carbon materials can undergo in-situ chemical reactions with the elemental lithium in the negative electrode active material to generate an artificial interface protective layer with a composite framework structure composed of lithium fluoride and lithium carbon-based compounds.

[0087] The negative electrode prepared by the above method includes lithium fluoride and a lithium-carbon-based compound interface layer. The lithium fluoride can be crystalline and / or amorphous lithium fluoride. Crystalline and / or amorphous lithium fluoride has a lower lithium-ion diffusion barrier, enabling rapid short-range ion transport. The lithium-carbon-based compound facilitates long-range lithium-ion and electron transport along the carbon layer. The composite framework structure composed of lithium fluoride and the lithium-carbon-based compound achieves a synergistic effect, significantly improving the lithium-ion transport kinetics at the negative electrode interface, increasing the lithium-ion transport efficiency between the lithium metal and the electrolyte layer, and enhancing the cycle performance of the battery cell. Preferably, the lithium fluoride can be amorphous lithium fluoride, thereby fully utilizing the lithium conduction pathway advantage of amorphous lithium fluoride to further improve the cycle performance of the battery cell.

[0088] Furthermore, this composite framework structure enables uniform distribution of lithium fluoride, providing a stable microenvironment for lithium-ion deposition. This facilitates uniform nucleation of lithium on the surface, effectively suppresses the growth of lithium dendrites, prevents short circuits caused by lithium dendrites penetrating the separator, and improves the safety performance of the battery cell. Meanwhile, lithium fluoride and lithium-based carbon compounds, based on their chemical inertness, can effectively suppress interfacial side reactions, improve the chemical stability and mechanical strength of the negative electrode, and further enhance the cycle performance of the battery cell.

[0089] In addition, the high thermal stability of lithium fluoride and lithium carbon-based compounds helps to mitigate thermal runaway behavior and further improve the safety performance of battery cells.

[0090] The application of alloy modifiers helps to introduce lithiated alloys into the artificial interface protective layer. Lithiated alloys help to improve the lithium atom and lithium vacancy transport rate inside the negative electrode, improve the density and uniformity of lithium deposition, thereby inhibiting the growth of lithium dendrites. They also help to further improve the electronic conductivity of the negative electrode, thereby improving the cycle performance of the battery cell. In addition, lithiated alloys have good ductility, which helps to improve the mechanical strength of the negative electrode, further improving the cycle performance of the battery cell.

[0091] The application of heteroatom modifiers helps to introduce heteroatoms into the artificial interface protective layer, which helps to improve the ionic conductivity of the negative electrode. Moreover, heteroatoms generally have high chemical inertness, which can further reduce the occurrence of interfacial side reactions and improve the cycle performance of the battery cell.

[0092] In some embodiments, an interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, comprising: Lithium-based metal pastes, including elemental lithium, are provided; A lithium-based metal slurry is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. An interface protective layer slurry is coated onto the surface of a lithium-based metal film layer facing away from the negative electrode current collector to obtain a negative electrode sheet comprising a lithium-based metal film layer and an artificial interface protective layer, wherein the lithium-based metal film layer is located between the negative electrode current collector and the artificial interface protective layer.

[0093] After depositing a lithium-based metal slurry onto the surface of the negative electrode current collector to obtain a negative electrode current collector comprising a lithium-based metal film layer, an interface protective layer slurry is then coated onto the surface of the lithium-based metal film layer opposite to the negative electrode current collector, resulting in a negative electrode sheet. A lithium-based metal film layer comprising elemental lithium can be formed between the negative electrode current collector and the artificial interface protective layer to serve as the negative electrode active material layer. Furthermore, fluorinated carbon materials and elemental lithium can undergo an in-situ interfacial chemical reaction on the surface of the negative electrode active material layer, generating an artificial interface protective layer with a composite framework structure comprising lithium fluoride and lithium-based compounds. Thus, the characteristics of the artificial interface protective layer can be utilized to form interfacial protection on the surface of the negative electrode active material layer, further reducing the occurrence of interfacial side reactions and lithium dendrite formation, thereby improving the cycle performance and safety performance of the battery cell.

[0094] In some embodiments, a lithium-based metal slurry is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector comprising a lithium-based metal film layer, including: We provide fluorocarbon materials, alloy modifiers, and heteroatom modifiers. A first molten mixture is obtained by melting and mixing lithium-based metal slurry, fluorinated carbon material, alloy modifier, and heteroatom modifier. The first molten mixture is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. The lithium-based metal film layer also includes a composite framework structure composed of lithium fluoride, lithium carbon-based compounds, lithium alloys, and heteroatoms. The composite framework structure is dispersed in the lithium-based metal film layer.

[0095] Lithium-based metal slurry, fluorinated carbon material, alloy modifier, and heteroatom modifier are melt-mixed to obtain a first molten mixture. This first molten mixture is then deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. This allows elemental lithium to undergo a high-temperature in-situ chemical reaction with the fluorinated carbon material, alloy modifier, and heteroatom modifier, generating a composite framework structure composed of lithium fluoride, lithium-based carbon compounds, lithium alloys, and heteroatoms. This structure not only forms an interface protective layer on the surface of the lithium-based metal film layer to reduce interfacial side reactions and lithium dendrite formation, but also disperses within the lithium-based metal film layer to provide further stress support for elemental lithium, promoting rapid transport of lithium atoms and vacancies, and reducing negative electrode pulverization and cracking caused by lithium stripping or deposition. This helps the negative electrode to possess both good interfacial stability and mechanical properties, effectively improving the cycle performance of the battery cell. The lithium fluoride can be crystalline and / or amorphous lithium fluoride. Preferably, the lithium fluoride can be amorphous lithium fluoride, thereby making full use of the lithium conduction pathway advantage of amorphous lithium fluoride and further improving the cycle performance of the battery cell.

[0096] In some embodiments, an interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, comprising: Provides elemental lithium; Elemental lithium and interface protective layer slurry are melt-mixed to obtain a second melt mixture; The second molten mixture is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer; wherein the artificial interface protective layer also includes elemental lithium, and the composite framework structure is dispersed in the elemental lithium.

[0097] Elemental lithium and an interface protective layer slurry are melt-mixed to obtain a second molten mixture. This second molten mixture is then deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer. This allows the elemental lithium to undergo a high-temperature in-situ chemical reaction with the fluorinated carbon material in the interface protective layer slurry, generating a composite framework structure composed of lithium fluoride and lithium-based compounds. The resulting artificial interface protective layer simultaneously contains the composite framework structure and elemental lithium. This artificial interface protective layer can be directly used as the negative electrode active material layer of the negative electrode sheet. The negative electrode active material layer can utilize the composite framework structure to further provide stress support for the elemental lithium, reducing negative electrode pulverization and cracking caused by lithium stripping or deposition, improving the mechanical strength and structural stability of the negative electrode, and further enhancing the cycle performance of the battery cell.

[0098] In some embodiments, an interface protective layer slurry is coated onto the surface of the lithium-based metal film layer facing away from the negative electrode current collector to obtain a negative electrode sheet comprising a lithium-based metal film layer and an artificial interface protective layer, including: The interface protective layer slurry is dispersed in a fluorinated solvent to obtain a precursor solution; In an inert atmosphere, the precursor solution is coated on the surface of the lithium-based metal film layer facing away from the negative electrode current collector. The coated negative electrode current collector is left to stand to obtain a negative electrode sheet consisting of a lithium-based metal film and an artificial interface protective layer.

[0099] By preparing a precursor solution and coating it onto the surface of a lithium-based metal film layer facing away from the negative electrode current collector, an in-situ interfacial chemical reaction can be achieved between fluorinated carbon materials and elemental lithium. This results in a composite framework composed of lithium fluoride and lithium-based compounds forming an interfacial protective layer on the surface of the lithium-based metal film layer. This helps reduce the occurrence of negative electrode interfacial side reactions and lithium dendrite formation, thereby improving the cycle performance of the battery cell.

[0100] In some embodiments, a lithium-based metal slurry, a fluorocarbon material, an alloy modifier, and a heteroatom modifier are melt-mixed to obtain a first melt mixture, comprising: In an inert atmosphere, fluorinated carbon materials, alloy modifiers, heteroatom modifiers, and lithium-based metal slurry are added to a container and heated and stirred. After the temperature in the container rises to the target temperature range, it is stirred at a constant temperature to obtain the first molten mixture.

[0101] By combining the aforementioned precursor solution coating preparation method, the composite framework structure composed of lithium fluoride and lithium carbon-based compounds can not only form a coating layer on the surface of the lithium-based metal film, but also allow the fluoride material and elemental lithium to undergo a high-temperature in-situ chemical reaction in an inert atmosphere by heating and stirring. This yields lithium fluoride and lithium carbon-based compounds that constitute the composite framework structure, which are then dispersed in the lithium-based metal film. This helps to give the negative electrode both good interfacial / bulk structure stability and mechanical properties, effectively improving the cycle performance of the battery cell.

[0102] In some embodiments, elemental lithium is melt-mixed with an interface protective layer slurry to obtain a second melt mixture, comprising: In an inert atmosphere, the interface protective layer slurry and elemental lithium are added to a container and heated and stirred. After the temperature inside the container rises to the target temperature range, it is stirred at a constant temperature to obtain a second molten mixture.

[0103] In an inert atmosphere, a second molten mixture is obtained by stirring and melting an interfacial protective layer slurry comprising fluorinated carbon materials, alloy modifiers, heteroatom modifiers, and elemental lithium. This allows the fluorinated carbon materials and elemental lithium to undergo a high-temperature in-situ chemical reaction in an inert atmosphere through heating and stirring, resulting in lithium fluoride and lithium-based compounds that constitute a composite framework structure and are dispersed in the elemental lithium. This helps to further provide stress support in the negative electrode, reduce pulverization and cracking caused by negative electrode peeling or deposition, improve the mechanical strength and structural stability of the negative electrode, and further improve the cycle performance of the battery cell.

[0104] In some embodiments, the fluorinated solvent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, and 2,2,2-trifluoroethyl ether, preferably 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0105] The aforementioned fluorinated solvents have a good dispersing effect on fluorinated carbon materials, and are stable and volatile after being coated on the surface of lithium metal. This helps to reduce solvent residue on the negative electrode and avoid side reactions involving the solvent when fluorinated carbon materials and lithium undergo in-situ chemical reactions, thus helping to improve the stability of the negative electrode interface.

[0106] Preferably, the fluorinated solvent can be 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, the structure of which is shown in Formula 1.

[0107] Formula 1 In some embodiments, in the step of dispersing the interface protective layer slurry in a fluorinated solvent, the mass ratio of the fluorinated carbon material in the interface protective layer slurry to the fluorinated solvent is 1:5 to 1:20, preferably 1:10.

[0108] Controlling the mass ratio of fluorinated carbon material to fluorinated solvent within the above range is beneficial for achieving full dissolution of the fluorinated carbon material, avoiding agglomeration, and improving the fullness of the in-situ chemical reaction.

[0109] In some embodiments, the settling temperature is 20 ℃-50 ℃. This facilitates the full evaporation of the solvent and the formation of lithium fluoride, and avoids negative electrode cracking / roughness caused by excessively high or low temperatures.

[0110] In some embodiments, the settling time is 12 h to 36 h. This helps to achieve sufficient solvent evaporation and improve the completeness of the in-situ chemical reaction, preferably 24 h.

[0111] In some embodiments, the dispersion method used to disperse the interface protective layer slurry in the fluorinated solvent is ultrasonic dispersion, and the ultrasonic dispersion time is 1 h-12 h, preferably 3 h. This helps to avoid agglomeration and improve the completeness of the in-situ chemical reaction.

[0112] In some embodiments, the target temperature range is 200 °C–350 °C, preferably 250 °C. A target temperature that is too low may prevent some components from melting, while a target temperature that is too high may cause other side reactions. Setting the target temperature range as described above helps to improve the completeness of the in-situ chemical reaction and avoid the occurrence of side reactions.

[0113] In some embodiments, the isothermal stirring time is 30 min to 1000 min, preferably 600 min. This helps to improve the dispersion uniformity of the components in the negative electrode, thereby improving the mechanical strength of the negative electrode.

[0114] In some embodiments, in the steps of adding fluorinated carbon material, alloy modifier, heteroatom modifier and lithium-based metal slurry to a container for heating and stirring, or adding interface protective layer slurry and elemental lithium to a container for heating and stirring, the mass ratio of fluorinated carbon material to elemental lithium is 1:10 to 1:30, preferably 1:20.

[0115] Controlling the mass ratio of fluorinated carbon materials to elemental lithium within the above range helps to ensure the advantages of low electrode potential and high theoretical specific capacity of the negative electrode sheet, while improving the sufficiency of in-situ chemical reaction and the continuity of the composite framework.

[0116] In some embodiments, the alloy modifier includes at least one of nano silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride.

[0117] In some embodiments, the heteroatom modifier includes at least one of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride.

[0118] One or more of nano-silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride, and tin fluoride can help increase the density of metal nucleation sites on the negative electrode, improve the conductivity of the negative electrode, and inhibit the growth of lithium dendrites, thereby further improving the cycle performance and safety performance of the battery cell.

[0119] Furthermore, the application of the aforementioned alloy modifiers also facilitates the formation of Li-M alloys in the negative electrode, where M includes one or more of silver, calcium, zinc, aluminum, magnesium, and tin. This helps to increase the lithium atom and lithium vacancy transport rate within the negative electrode and provides nucleation sites, improving the density and uniformity of lithium deposition, thereby suppressing lithium dendrite growth. It also helps to further improve the electronic conductivity of the negative electrode, thus enhancing the cycle performance of the battery cell. The Li-M alloy also exhibits good ductility, which helps to improve the mechanical strength of the negative electrode, further enhancing the cycle performance of the battery cell.

[0120] One or more nitrides, such as magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride, help improve the ionic conductivity of the negative electrode. Furthermore, nitrides have high chemical inertness, which can further reduce the occurrence of interfacial side reactions and improve the cycle performance of the battery cell.

[0121] In some embodiments, the fluorinated carbon material includes at least one of fluorinated graphite, fluorinated graphene, fluorinated carbon fiber, fluorinated carbon nanotubes, and fluorinated fullerene.

[0122] Thirdly, embodiments of this application provide a battery cell including an electrode assembly, an electrolyte, and a separator. The electrode assembly includes a positive electrode and a negative electrode. The negative electrode includes a negative electrode as described in the first aspect, or a negative electrode obtained by the method described in the second aspect.

[0123] In embodiments of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector and including a positive active material.

[0124] It is understood that the positive electrode sheet can have a positive active material layer on one surface of the positive current collector, or it can have a positive active material layer on both surfaces of the positive current collector. This application does not make any special limitation on this.

[0125] The positive current collector can be a metal foil or a porous metal plate, such as foil or porous plate of metals or alloys thereof, such as aluminum, copper, nickel, titanium, iron, etc. In some embodiments of this application, the positive current collector is aluminum foil.

[0126] In some embodiments of this application, the positive electrode active material may be selected from at least one of the following: lithium manganese iron phosphate, lithium iron phosphate, lithium manganese phosphate, etc., olivine structure materials, NCM811, NCM622, NCM523, NCM333, etc., lithium cobalt oxide materials, lithium manganese oxide materials, and other metal oxides capable of lithium intercalation / deintercalation.

[0127] In some embodiments of this application, the positive electrode active material layer further includes an adhesive that enhances the bonding between the positive electrode active material particles and also enhances the bonding between the positive electrode active material and the current collector. Exemplarily, the adhesive may be selected from at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon.

[0128] In some embodiments of this application, the positive electrode active material layer further includes a conductive agent selected from at least one of carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. Exemplarily, the carbon-based material is selected from carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, or any combination thereof. The metal-based material is selected from metal powder, metal fibers, copper, nickel, aluminum, or silver. The conductive polymer is a polyphenylene derivative.

[0129] The positive electrode sheet in this application can be prepared according to conventional methods in the art. For example, active materials, conductive materials, and binders are dispersed and mixed in N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, cutting, slitting, and re-drying, the positive electrode sheet is obtained. Alternatively, it can be mixed with solid electrolyte powder to obtain a uniform positive electrode active material-solid electrolyte powder, which is then cold-pressed to form a composite solid positive electrode sheet.

[0130] In the embodiments of this application, the separator can be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer composite film thereof.

[0131] In some embodiments of this application, the separator is a single-layer separator or a multi-layer separator.

[0132] This application does not impose any particular limitations on the shape and thickness of the separator. The method for preparing the separator is a well-known method in the art and can be used to prepare separators for battery cells.

[0133] In the embodiments of the battery cell of this application, the electrolyte is the carrier of ion transport and can play a role in conducting ions between the positive electrode and the negative electrode, which is the guarantee for the battery cell to obtain good cycle performance and other advantages.

[0134] In the embodiments of this application, the electrolyte includes at least one of liquid electrolyte, inorganic solid electrolyte, polymer and composite solid electrolyte.

[0135] In the embodiments of this application, the liquid electrolyte includes at least one solvent such as ethylene carbonate, propylene carbonate (PC), fluoroethylene carbonate (FEC), dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, and 1,3-dioxolane. Ethyl carbonate and fluoroethylene carbonate can work synergistically to facilitate the formation of a stable SEI film on the surface of the negative electrode, thereby improving the high-temperature storage performance and high-temperature cycle performance of the battery cell.

[0136] In embodiments of this application, the inorganic solid electrolyte includes Li7La3Zr2O 12 Li 3x La 2 / 3−x TiO3, Li 1+ x Al x Ti 2−x (PO4)3, Li6PS5Cl, Li3YCl6, Li2ZrCl6, Li 10 GeP2S 12 Any one of them.

[0137] In the embodiments of this application, the polymer and the composite solid electrolyte include any one of polyethylene oxide (PEO), poly(1,3-dioxolane), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polymethyl methacrylate, polyacrylonitrile, etc., and their combination with any one of inorganic solid electrolytes.

[0138] In the embodiments of this application, while ensuring the cycle performance of the battery cell, it is also necessary to improve the charge and discharge performance of the battery cell. Therefore, the liquid electrolyte also includes lithium salt. The embodiments of this application do not specifically limit the specific material of the lithium salt, which can be a lithium salt commonly used in the art. For example, the lithium salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(oxalate-borate), and lithium di(fluorooxalate-borate).

[0139] Liquid electrolytes can be prepared using methods conventional in the art. For example, an organic solvent, a lithium salt, and optional additives can be mixed uniformly to obtain a liquid electrolyte, wherein there are no particular restrictions on the order in which the materials are added.

[0140] In some embodiments, the interface protective layer slurry can be coated onto the surface of the negative electrode current collector using a wet coating method to directly form an artificial interface protective layer on the surface of the negative electrode current collector.

[0141] In some embodiments, the interface protective layer slurry can be applied to the surface of the diaphragm using a wet coating method to directly form an artificial interface protective layer on the surface of the diaphragm.

[0142] Fourthly, embodiments of this application provide a battery device, which includes a negative electrode sheet according to the first aspect, or a negative electrode sheet obtained by the method of the second aspect, or a battery cell according to the third aspect.

[0143] Fifthly, embodiments of this application provide an electrical device, which includes a negative electrode sheet according to the first aspect, or a negative electrode sheet obtained by the method of the second aspect, or a battery cell according to the third aspect, or a battery device according to the fourth aspect.

[0144] In some embodiments, the electrical device provided in this application is applicable to various electrical devices that use solid-state battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Solid-state battery cells and battery devices are used to store or provide electrical energy.

[0145] Example 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 weight, 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.

[0146] Performance testing In the examples using liquid electrolytes, polymer solid electrolytes, and composite solid electrolytes, a 2032 coin cell battery was used for evaluation. The test conditions were as follows: any one of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide was used as the positive electrode material, with an areal capacity of 1.0 mAh / cm². 2 A negative electrode sheet with a thickness of 100 μm was used as the negative electrode, and the battery cycle life evaluation standard was calculated based on 80% capacity retention.

[0147] In the examples using inorganic solid-state electrolytes, a model battery was used for evaluation. The test conditions were as follows: any one of lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide was used as the positive electrode material, with an areal capacity of 1.0 mAh / cm². 2 A negative electrode sheet with a thickness of 100 μm is used as the negative electrode, and the battery cycle life evaluation standard is calculated based on a 70% capacity retention rate.

[0148] Specifically: Nickel-cobalt-manganese lithium oxide battery cell 25°C cycle test The examples and comparative examples were subjected to a 25°C cycle test on individual battery cells according to the following steps: Take the lithium metal battery after it has been capacitated and let it rest for more than 12 hours. First, activate it for 5 cycles at a constant current of 0.05 C within a voltage range of 2.8-4.3 V. Then, perform long-cycle charge-discharge cycles on the battery at a constant current of 0.2 C within a voltage range of 2.8-4.3 V.

[0149] In the various embodiments and comparative examples of this application, battery cells are prepared using the following methods, and the performance of the battery cells is tested.

[0150] Example 1 Preparation method of battery cell Preparation of negative electrode sheet 1) 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether was selected as the fluorination solvent. Fluorinated graphite (FG) was added to the fluorination solvent and ultrasonically treated for 1 h to obtain a precursor solution. The mass ratio of fluorinated graphite to 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether was 1:10.

[0151] 2) A lithium-based metal slurry including elemental lithium is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer.

[0152] 3) In an inert atmosphere, the precursor solution is coated onto the surface of the lithium-based metal film layer facing away from the negative electrode current collector. After coating, the film is left to stand at 25 °C for 3 h to obtain the negative electrode sheet.

[0153] Preparation of electrolytes 100 mg of Li6PS5Cl powder was placed in a mold, and a pressure of 360 MPa was applied to the lithium sulfide powder by a hydraulic press and held for 1 min to complete the room temperature pressing process of the electrolyte sheet, thus obtaining the lithium sulfide solid electrolyte.

[0154] Preparation of cathode materials LiNi 0.6 Co 0.2 Mn 0.2 O2 active material and Li6PS5Cl sulfide electrolyte powder are mixed at a mass ratio of 7:3 and ground for 15 min to obtain composite cathode material.

[0155] Assembly of battery cells First, the sulfide solid electrolyte is pressed into a mold battery, and then coated with approximately 1 mAh / cm³. 2The composite positive electrode material powder was then used to prepare the positive electrode-electrolyte layer by maintaining a pressure of 400 MPa for 5 min. Finally, the prepared negative electrode sheet was attached to the other surface of the electrolyte. The molded battery was then sealed and a pressure of 5 MPa was applied for subsequent electrochemical tests.

[0156] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 203.

[0157] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0158] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 52.

[0159] Example 2 The only difference between Example 2 and Example 1 is that: Preparation of negative electrode sheet 1) In an inert atmosphere, fluorinated graphite and elemental lithium are added to a crucible, heated and stirred continuously. After the temperature reaches the target temperature of 200 °C, the mixture is stirred at a constant temperature for 5 min to obtain a molten mixture. The mass ratio of fluorinated graphite to elemental lithium is 1:10.

[0160] 2) In an inert atmosphere, the molten mixture is added to the electrode mold and cooled to room temperature. After the molten mixture has completely solidified on the surface of the negative electrode current collector, it is demolded and rolled to obtain the negative electrode sheet.

[0161] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 183.

[0162] Comparative Example 2 The only difference between Comparative Example 2 and Example 2 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0163] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 36.

[0164] Example 3 The only difference between Example 3 and Example 1 is that: Preparation of negative electrode sheet 1) In an inert atmosphere, fluorinated graphite and elemental lithium are added to a crucible, heated and stirred continuously. After the temperature reaches the target temperature of 185 °C, the mixture is stirred at a constant temperature for 5 min to obtain a molten mixture. The mass ratio of fluorinated graphite to elemental lithium is 1:15.

[0165] 2) In an inert atmosphere, the molten mixture is added to the electrode mold and cooled to room temperature. After the first molten mixture has completely solidified on the surface of the negative electrode current collector, it is demolded to obtain the pre-modified negative electrode sheet.

[0166] 3) 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether was selected as the fluorination solvent. Fluorinated graphite (FG) was added to the fluorination solvent and ultrasonically treated for 3 h to obtain the precursor solution. The mass ratio of fluorinated graphite to 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether was 1:20.

[0167] 4) In an inert atmosphere, the precursor solution was coated onto the surface of the lithium-based metal film in the pre-modified negative electrode. After coating, the electrode was allowed to stand at 25 °C for 5 h to obtain the negative electrode.

[0168] Preparation of electrolytes Take 100 mg Li 10 GeP2S 12 The powder was placed in a mold, and a hydraulic press was used to apply a pressure of 400 MPa to the lithium sulfide powder and hold it for 1 min to complete the room temperature pressing process of the electrolyte sheet, thus obtaining Li. 10 GeP2S 12 Sulfide solid electrolyte.

[0169] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 173.

[0170] Comparative Example 3 The only difference between Comparative Example 3 and Example 3 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0171] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 14.

[0172] Example 4 The only difference between Example 4 and Example 1 is that: In preparing the precursor solution, fluorinated graphite, alloy modifier nano-silver, and heteroatom modifier magnesium nitride are added to a fluorinated solvent to obtain the precursor solution; wherein, the mass ratio of fluorinated graphite, alloy modifier nano-silver, and heteroatom modifier magnesium nitride is 8:1:1, and the total mass ratio of the three to the mass ratio of metallic lithium is 1:20.

[0173] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 186.

[0174] Comparative Example 4 The only difference between Comparative Example 4 and Example 4 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0175] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 34.

[0176] Example 5 The only difference between Example 5 and Example 2 is that: In preparing the molten mixture, fluorinated graphite, alloy modifier nano-silver, heteroatom modifier magnesium nitride, and elemental lithium are added together into a crucible to obtain the molten mixture; wherein the mass ratio of fluorinated graphite, alloy modifier nano-silver, and heteroatom modifier magnesium nitride is 7:3:2, and the total mass of the three is in the mass ratio of lithium metal to lithium metal is 1:25.

[0177] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 165.

[0178] Comparative Example 5 The only difference between Comparative Example 5 and Example 5 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0179] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 47.

[0180] Example 6 The only difference between Example 6 and Example 3 is that: In preparing the molten mixture, fluorinated graphite, alloy modifier nano-silver, heteroatom modifier magnesium nitride, and elemental lithium are added together into a crucible to obtain the molten mixture; wherein the mass ratio of fluorinated graphite, alloy modifier nano-silver, and heteroatom modifier magnesium nitride is 8:1:1, and the total mass ratio of the three to the mass ratio of metallic lithium is 20:1.

[0181] In preparing the precursor solution, fluorinated graphite, alloy modifier nano-silver, and heteroatom modifier magnesium nitride are added to the fluorinated solvent to obtain the precursor solution; wherein, the mass ratio of fluorinated graphite, alloy modifier nano-silver, and heteroatom modifier magnesium nitride is 8:1:1, and the mass ratio of the total mass of the three to the mass of the fluorinated solvent is 1:30.

[0182] Preparation of electrolytes The electrolyte is a polyvinylidene fluoride (PVDF) solid electrolyte. The preparation method involves uniformly dissolving PVDF, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalatoborate) in N,N-dimethylformamide at a mass ratio of 4:6:1, and stirring at 60°C for 6 hours to obtain an electrolyte slurry. Next, the electrolyte slurry is coated onto a glass substrate using a doctor blade, and then dried in a vacuum oven at 80°C for 24 hours to remove free N,N-dimethylformamide solvent. Finally, the electrolyte membrane is peeled off from the glass substrate and cut into sheets with a diameter of 19 mm to obtain the PVDF solid electrolyte.

[0183] Preparation of cathode materials LiNi 0.8 Co 0.1 Mn 0.1 O2 active material, conductive carbon black, and binder were mixed and dispersed in N,N-dimethylformamide at a mass ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was coated onto an aluminum foil current collector using a doctor blade and then dried in a vacuum oven at 80°C for 24 hours to remove free N,N-dimethylformamide solvent. Finally, the positive electrode was cut into sheets with a diameter of 13 mm to obtain LiNi. 0.8 Co 0.1 Mn 0.1 O2 positive electrode.

[0184] Assembly of battery cells The battery assembly is completed in the CR2032 battery without using an additional separator to separate the positive and negative electrodes. 3... The interface was wetted using L of liquid electrolyte (1 M LiPF6-FEC / DMC (volume ratio 1:4)).

[0185] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 412.

[0186] Comparative Example 6 The only difference between Comparative Example 6 and Example 6 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0187] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 148.

[0188] Example 7 The only difference between Example 7 and Example 6 is that fluorinated graphite is replaced with fluorinated carbon fiber.

[0189] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 408.

[0190] Comparative Example 7 The only difference between Comparative Example 7 and Example 7 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0191] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 142.

[0192] Example 8 The only difference between Example 8 and Example 1 is that fluorinated graphite is replaced with fluorinated carbon nanotubes.

[0193] Preparation of electrolytes The electrolyte is a poly(1,3-dioxopentane) electrolyte, which is prepared by dissolving 2 mol / L LiTFSI and 1 wt.% aluminum trifluoromethanesulfonate in 1,3-dioxopentane and 5 wt.% fluoroethylene carbonate to obtain the 1,3-dioxopentane electrolyte monomer.

[0194] Assembly of battery cells The battery assembly was completed in the CR2032 battery, and the positive and negative electrodes were separated using a PE separator. 50 The 1,3-dioxolane electrolyte monomer obtained above was placed in the battery casing and left to stand at room temperature for 24 h to allow aluminum trifluoromethanesulfonate to initiate the ring-opening polymerization of 1,3-dioxolane for subsequent testing.

[0195] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 423.

[0196] Comparative Example 8 The only difference between Comparative Example 8 and Example 8 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0197] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 162.

[0198] Example 9 The only difference between Example 9 and Example 8 is that, in preparing the precursor solution, fluorinated graphite and the heteroatom modifier magnesium nitride are added to the fluorinated solvent to obtain the precursor solution; wherein, the mass ratio of fluorinated graphite and the heteroatom modifier magnesium nitride is 9:1, and the total mass of the two is 1:15 with the mass ratio of lithium metal.

[0199] Preparation of negative electrode sheet In an inert atmosphere, the precursor solution was coated onto the surface of the PE separator. After coating, a current collector was added, and the membrane was left to stand at 25 °C for 5 h to obtain the treated negative electrode sheet.

[0200] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 353.

[0201] Comparative Example 9 The only difference between Comparative Example 9 and Example 9 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0202] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 119.

[0203] Example 10 The only difference between Example 10 and Example 8 is that, in preparing the precursor solution, fluorinated graphite and alloy modifier nano-silver are added to the fluorinated solvent to obtain the precursor solution; wherein, the mass ratio of fluorinated graphite and alloy modifier nano-silver is 9:1, and the total mass of the two is 1:15 with the mass ratio of lithium metal.

[0204] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 326.

[0205] Comparative Example 10 The only difference between Comparative Example 10 and Example 10 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0206] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 105.

[0207] Example 11 The only difference between Example 11 and Example 6 is that: In preparing the molten mixture, fluorinated graphite, heteroatom modifier magnesium nitride, and elemental lithium are added together to a crucible to obtain the molten mixture; wherein the mass ratio of fluorinated graphite and heteroatom modifier magnesium nitride is 9:1, and the total mass ratio of the two to the mass ratio of metallic lithium is 20:1.

[0208] Preparation of electrolytes The electrolyte is 0.8 mol / L lithium hexafluorophosphate-0.2 mol / L LiTFSI-FEC / DMC (volume ratio 1:4).

[0209] Assembly of battery cells The battery assembly was completed in the CR2032 battery, and the positive and negative electrodes were separated using a PE separator. 50 The electrolyte was placed in the battery casing and left to stand at room temperature for 24 hours for subsequent testing.

[0210] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 374.

[0211] Comparative Example 11 The only difference between Comparative Example 11 and Example 11 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0212] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 153.

[0213] Example 12 The only difference between Example 12 and Example 11 is that, in preparing the molten mixture, fluorinated graphite, alloy modifier nano-silver, and elemental lithium are added together to the crucible to obtain the molten mixture; wherein the mass ratio of fluorinated graphite and alloy modifier nano-silver is 14:1, and the mass ratio of their total mass to that of metallic lithium is 15:1.

[0214] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 421.

[0215] Comparative Example 12 The only difference between Comparative Example 12 and Example 12 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0216] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 143.

[0217] Example 13 The only difference between Example 13 and Example 1 is that the positive electrode material is 1 mAh / cm³. 2 Lithium iron phosphate.

[0218] The battery cycle voltage range is 2.5~4 V.

[0219] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 301.

[0220] Comparative Example 13 The only difference between Comparative Example 13 and Example 13 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0221] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 70% of the first discharge capacity was 61.

[0222] Example 14 The only difference between Example 14 and Example 11 is that the electrolyte is 1.0 mol / L lithium hexafluorophosphate-0.2 mol / L lithium bis(oxalate)borate-EC / DMC / FEC (volume ratio 1:3:1).

[0223] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 407.

[0224] Comparative Example 14 The only difference between Comparative Example 14 and Example 14 is that the negative electrode sheet only includes a negative current collector and a single-element lithium film layer coated on the surface of the negative current collector.

[0225] Test results: In the 25℃ cycle test, the number of charge-discharge cycles corresponding to the first drop in discharge capacity to 80% of the first discharge capacity was 71.

[0226] Figure 5 The C1s X-ray photoelectron spectra of the fluorinated graphite material and the negative electrode sheet provided in Example 1 are shown. Figure 6 The F 1s X-ray photoelectron spectra of the fluorinated graphite material and the negative electrode sheet provided in Example 1 are shown. Figure 7 The SEM image of the negative electrode sheet provided in Example 1 is shown. Figure 8 The EDS elemental distribution diagram of the negative electrode sheet provided in Example 1 is shown. Figure 9 A schematic diagram of the cycle performance of the battery cell prepared in Example 1 at 25 °C and 0.1 C is shown. Figure 10 The SEM image of the negative electrode sheet provided in Example 2 is shown. Figure 11The diagram shows the EDS elemental distribution of the negative electrode sheet provided in Example 2.

[0227] Combination Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 , Figure 11 As can be seen from the above embodiments and comparative examples, the negative electrode sheet provided in this application can make full use of the low electrode potential and high theoretical specific capacity advantages of lithium metal as a negative electrode material, and on this basis improve the cycle performance and safety performance of the battery cell.

[0228] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A negative electrode sheet for lithium batteries, characterized in that, include: Negative electrode current collector; An artificial interface protective layer is located on at least one side of the negative electrode current collector, and the artificial interface protective layer comprises a composite framework structure composed of lithium fluoride and lithium carbon-based compounds.

2. The negative electrode sheet according to claim 1, characterized in that, The negative electrode also includes a lithium-based metal film layer, which is located between the negative electrode current collector and the artificial interface protective layer, and the lithium-based metal film layer includes elemental lithium.

3. The negative electrode sheet according to claim 2, characterized in that, The lithium-based metal film also includes a composite framework structure composed of lithium fluoride and lithium carbon-based compounds, which is dispersed in the lithium-based metal film.

4. The negative electrode sheet according to claim 2, characterized in that, The lithium-based metal film layer satisfies one or more of the following conditions: (1) The lithium-based metal film layer further includes a Li-M alloy, wherein M includes one or more of silver, calcium, zinc, aluminum, magnesium and tin; (2) The lithium-based metal film layer further includes one or more of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride; (3) The lithium-based metal film layer also includes one or more of nano silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride and tin fluoride.

5. The negative electrode sheet according to claim 1, characterized in that, The artificial interface protective layer also includes elemental lithium, and the composite framework structure is dispersed within the elemental lithium.

6. The negative electrode sheet according to any one of claims 1-5, characterized in that, The artificial interface protective layer satisfies one or more of the following conditions: (1) The artificial interface protective layer further includes a Li-M alloy, wherein M includes one or more of silver, calcium, zinc, aluminum, magnesium and tin; (2) The artificial interface protective layer further includes one or more of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride and vanadium nitride; (3) The artificial interface protective layer also includes one or more of nano silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride and tin fluoride.

7. The negative electrode sheet according to claim 1, characterized in that, The thickness of the artificial interface protective layer is 1. 100 .

8. A method for preparing a negative electrode sheet, characterized in that, include: An interface protective layer slurry is provided, the interface protective layer slurry comprising fluorocarbon material, alloy modifier and heteroatom modifier; The interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, wherein the artificial interface protective layer includes a composite framework structure composed of lithium fluoride, lithium carbon-based compounds, lithium alloys, and heteroatoms.

9. The method according to claim 8, characterized in that, The interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain the negative electrode sheet including the artificial interface protective layer, comprising: Lithium-based metal pastes, including elemental lithium, are provided; The lithium-based metal slurry is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. The interface protective layer slurry is coated on the surface of the lithium-based metal film layer facing away from the negative electrode current collector to obtain a negative electrode sheet including the lithium-based metal film layer and the artificial interface protective layer, wherein the lithium-based metal film layer is located between the negative electrode current collector and the artificial interface protective layer.

10. The method according to claim 9, characterized in that, The lithium-based metal slurry is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer, comprising: We provide fluorocarbon materials, alloy modifiers, and heteroatom modifiers. The lithium-based metal slurry, fluorinated carbon material, alloy modifier, and heteroatom modifier are melt-mixed to obtain a first melt mixture; The first molten mixture is deposited on the surface of the negative electrode current collector to obtain a negative electrode current collector including a lithium-based metal film layer. The lithium-based metal film layer further includes a composite framework structure composed of lithium fluoride, lithium carbon-based compounds, lithium alloys, and heteroatoms, and the composite framework structure is dispersed in the lithium-based metal film layer.

11. The method according to claim 8, characterized in that, The interface protective layer slurry is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer, comprising: Provides elemental lithium; The elemental lithium is melt-mixed with the interface protective layer slurry to obtain a second melt mixture; The second molten mixture is deposited on at least one side of the negative electrode current collector to obtain a negative electrode sheet including an artificial interface protective layer; wherein the artificial interface protective layer further includes elemental lithium, and the composite framework structure is dispersed in the elemental lithium.

12. The method according to any one of claims 8-11, characterized in that, The method satisfies one or more of the following conditions: (1) The alloy modifier includes at least one of nano silver, silver fluoride, calcium fluoride, zinc fluoride, aluminum fluoride, magnesium fluoride and tin fluoride; (2) The heteroatom modifier includes at least one of magnesium nitride, boron nitride, aluminum nitride, lithium nitride, titanium nitride, chromium nitride, and vanadium nitride; (3) The fluorinated carbon material includes at least one of fluorinated graphite, fluorinated graphene, fluorinated carbon fiber, fluorinated carbon nanotubes and fluorinated fullerene.

13. A single battery cell, characterized in that, The battery cell includes an electrode assembly, an electrolyte, and a separator. The electrode assembly includes a positive electrode and a negative electrode. The negative electrode is the negative electrode as described in any one of claims 1-7, or a negative electrode prepared by the method described in any one of claims 8-12.

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