Negative electrode sheet, and preparation method therefor and use thereof

Abstract

A negative electrode sheet, and a preparation method therefor and a use thereof. The negative electrode sheet comprises: a current collector, wherein the current collector comprises a first side and a second side which are opposite to each other; and a first active material layer, a second active material layer and a first artificial SEI layer, wherein the first active material layer, the second active material layer and the first artificial SEI layer are sequentially arranged on the first side of the current collector in a direction away from the current collector, the first active material layer comprises metal lithium, the second active material layer comprises a metal lithium alloy, and the first artificial SEI layer comprises a lithium compound. The use of the negative electrode sheet can avoid the problems of continuous thickening of an SEI film, continuous growth of lithium dendrites, dead lithium, piercing of a separator by the lithium dendrites, etc., thereby improving the cycling stability of a lithium metal battery using the negative electrode sheet.

Description

Negative electrode sheet and its preparation method and application

[0001] This application claims priority and benefits of patent application No. 202311572833.0 filed with the State Intellectual Property Office of China on November 22, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0002] The present invention belongs to the technical field of batteries, and in particular relates to a negative electrode plate and a preparation method and application thereof. Background Art

[0003] Compared with the theoretical specific capacity of 372mAh / g of graphite negative electrode, metallic lithium has an ultra-high theoretical specific capacity of 3860mAh / g and the most negative standard reduction potential (-3.04V). It also has the characteristics of low density and small ion radius. Using metallic lithium as the active material of the battery negative electrode can further improve the energy density of the battery.

[0004] Because lithium ions have a high diffusion barrier, they react with the electrolyte / electrolyte, consuming the lithium metal anode and electrolyte, resulting in capacity loss. Furthermore, unlike commercial graphite anodes, the lithium metal anode's lithium ion storage mechanism is not intercalation, but rather serves as a lithium source itself, resulting in a significant volume expansion of the lithium metal anode. Whether using lithium metal anodes in solid or liquid systems, they face technical challenges such as the high chemical reactivity of lithium metal, the infinite volume change rate leading to SEI film thickening, lithium dendrite growth, dead lithium, and lithium dendrites piercing the separator.

[0005] Summary of the Invention

[0006] The present invention aims to at least partially address one of the technical problems in the related art. To this end, one object of the present invention is to provide a negative electrode sheet, a method for preparing the same, and applications thereof. The negative electrode sheet can avoid problems such as continuous thickening of the SEI film, continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the separator, thereby improving the cycling stability of lithium metal batteries using the negative electrode sheet.

[0007] In a first aspect of the present invention, the present invention provides a negative electrode plate. According to an embodiment of the present invention, the negative electrode plate includes:

[0008] a current collector comprising opposing first and second sides;

[0009] A first active material layer, a second active material layer and a first artificial SEI layer, wherein the first active material layer, the second active material layer and the first artificial SEI layer are sequentially arranged on the first side of the current collector in a direction away from the current collector, the first active material layer includes metallic lithium, the second active material layer includes a metallic lithium alloy, and the first artificial SEI layer includes a lithiation.

[0010] According to the negative electrode sheet of the above embodiment of the present invention, a first active material layer, a second active material layer and a first artificial SEI layer are sequentially arranged on the first side of the current collector in a direction away from the current collector. The first active material layer includes metallic lithium, which can be used as a supplementary lithium source to improve the cycle life of the battery. The second active material layer includes a metallic lithium alloy. On the one hand, it can avoid direct contact between the metallic lithium with high reactivity in the first active material layer and the electrolyte or electrolyte. On the other hand, it can enable the metallic lithium to undergo alloying reaction with the metallic lithium alloy in the second active material layer during the charge and discharge process of the battery, which is beneficial to the metallic lithium. The uniform deposition of metal lithium can effectively avoid the growth of lithium dendrites caused by uneven deposition of metal lithium, as well as the problems such as continuous thickening of SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by infinite volume change rate. The first artificial SEI layer includes a lithium compound, which can further avoid the direct contact of metal lithium with high reactivity in the first active material layer with the electrolyte or electrolyte on the one hand, and promote the rapid migration of lithium ions on the other hand, thereby effectively avoiding the growth of lithium dendrites caused by untimely deintercalation of lithium ions at the negative electrode, as well as the problems such as continuous thickening of SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by infinite volume change rate. Therefore, the use of the negative electrode plate of the present invention can improve the interface problem of metal lithium in secondary battery applications, avoid the problems such as continuous thickening of SEI film, continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the diaphragm, thereby helping to improve the cycle stability of the lithium metal battery using the negative electrode plate.

[0011] In addition, the negative electrode sheet according to the above embodiment of the present invention may also have the following additional technical features:

[0012] In some embodiments of the present invention, the current collector is a composite current collector.

[0013] In some embodiments of the present invention, the current collector is a metal foil current collector, and the metal foil current collector includes at least one of copper, aluminum, zinc, nickel and chromium.

[0014] In some embodiments of the present invention, the thickness of the current collector is 1 μm-10 μm.

[0015] In some embodiments of the present invention, the current collector includes a base film, a first conductive layer disposed on one side of the base film, and a second conductive layer disposed on the other side opposite to the base film.

[0016] In some embodiments of the present invention, the first conductive layer and the second conductive layer each independently include at least one of copper, aluminum, zinc, nickel, and chromium, thereby improving the conductivity of the current collector.

[0017] In some embodiments of the present invention, the thickness of the first conductive layer and the second conductive layer are independently 0.3 μm-10 μm.

[0018] In some embodiments of the present invention, the base film includes at least one of polyethylene, polyethylene terephthalate, polyimide, polypropylene, polyamide, polyphenylene sulfide, and polyethylene naphthalate.

[0019] In some embodiments of the present invention, the base film has a thickness of 1 μm-10 μm.

[0020] In some embodiments of the present invention, the negative electrode plate further includes a third active material layer, which is disposed on the second side of the current collector and includes a metal lithium alloy.

[0021] In some embodiments of the present invention, the first active material layer is disposed on the first conductive layer, and the third active material layer is disposed on the second conductive layer.

[0022] In some embodiments of the present invention, the negative electrode sheet further includes a second artificial SEI layer, which is disposed on a side of the third active material layer away from the current collector, and includes a lithium compound.

[0023] In some embodiments of the present invention, the above-mentioned negative electrode sheet also includes a fourth active material layer and a third artificial SEI layer, and the fourth active material layer and the third artificial SEI layer are arranged in sequence on the second side of the current collector in a direction away from the current collector, the fourth active material layer includes metallic lithium, and the third artificial SEI layer includes lithium compound and metallic lithium alloy.

[0024] In some embodiments of the present invention, the first active material layer is disposed on the first conductive layer, and the fourth active material layer is disposed on the second conductive layer.

[0025] In some embodiments of the present invention, the above-mentioned negative electrode plate also includes a fifth active material layer and a sixth active material layer, and the fifth active material layer and the sixth active material layer are arranged in sequence on the second side of the current collector in a direction away from the current collector, the fifth active material layer includes metallic lithium, and the sixth active material layer includes a metallic lithium alloy.

[0026] In some embodiments of the present invention, the first active material layer is disposed on the first conductive layer, and the fifth active material layer is disposed on the second conductive layer.

[0027] In some embodiments of the present invention, the negative electrode sheet further includes a fourth artificial SEI layer, which is disposed on a side of the sixth active material layer away from the current collector, and the fourth artificial SEI layer includes a lithium compound.

[0028] In some embodiments of the present invention, the metal lithium alloy comprises an alloy formed by metal lithium and at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth. This can address issues such as uneven deposition of metal lithium on the negative electrode surface, resulting in lithium dendrite growth, continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm during lithium metal battery cycling.

[0029] In some embodiments of the present invention, the lithium content of the metallic lithium alloy is 0.1 atm% to 99.9 atm%. This can solve the problems of lithium dendrite growth, continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the diaphragm caused by uneven deposition of metallic lithium on the negative electrode surface during the cycle of lithium metal batteries.

[0030] In some embodiments of the present invention, the thickness of the first active material layer, the second active material layer, and the third active material layer are independently 0.1 μm-100 μm.

[0031] In some embodiments of the present invention, the thickness of the fourth active material layer is 0.1 μm-100 μm.

[0032] In some embodiments of the present invention, the thickness of the fifth active material layer and the sixth active material layer are independently 0.1 μm-100 μm.

[0033] In some embodiments of the present invention, the lithium compound comprises a compound of lithium and at least one of halogen, oxygen, nitrogen, sulfur, and phosphorus. This effectively avoids problems such as lithium dendrite growth caused by untimely lithium ion deintercalation at the negative electrode, continuous SEI film thickening due to an infinite volume change rate, dead lithium, and lithium dendrites piercing the separator.

[0034] In some embodiments of the present invention, the metal lithium alloy in the third artificial SEI layer includes Li-M, wherein M includes at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, silver, tin and bismuth, and the molar ratio of the lithium compound in the third artificial SEI layer to the Li-M is (0.1-10):1.

[0035] In some embodiments of the present invention, the thickness of the first artificial SEI layer and the second artificial SEI layer are independently 0.1 μm-1 μm.

[0036] In some embodiments of the present invention, the thickness of the third artificial SEI layer is 0.1 μm-1 μm.

[0037] In some embodiments of the present invention, the thickness of the fourth artificial SEI layer is 0.1 μm-1 μm.

[0038] In a second aspect of the present invention, a method for preparing a negative electrode sheet is provided. According to an embodiment of the present invention, the method comprises:

[0039] providing a current collector comprising opposing first and second sides;

[0040] forming a first active material layer on a first side of the current collector, wherein the first active material layer includes metallic lithium;

[0041] forming a second active material layer on a side of the first active material layer away from the current collector, wherein the second active material layer comprises a metallic lithium alloy;

[0042] A first artificial SEI layer is formed on a side of the second active material layer away from the first active material layer, wherein the first artificial SEI layer includes a lithium compound.

[0043] According to the method for preparing the negative electrode sheet of the above embodiment of the present invention, a current collector including a first side and a second side relative to each other is provided, and a first active material layer is formed on the first side of the current collector, a second active material layer is formed on the side of the first active material layer away from the current collector, and a first artificial SEI layer is formed on the side of the second active material layer away from the first active material layer. The first active material layer includes metallic lithium, which can be used as a supplementary lithium source to improve the cycle life of the battery. The second active material layer includes a metallic lithium alloy, which can avoid direct contact between the metallic lithium with high reactivity in the first active material layer and the electrolyte or electrolyte on the one hand, and on the other hand, can prevent the metallic lithium from contacting the second active material layer during the charge and discharge process of the battery. The metal lithium alloy in the active material layer undergoes an alloying reaction, which is beneficial to the uniform deposition of metal lithium, thereby effectively avoiding the uneven deposition of metal lithium causing the growth of lithium dendrites, as well as the problems such as the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by the infinite volume change rate. The first artificial SEI layer includes a lithiate, which can further avoid the direct contact of the highly reactive metal lithium in the first active material layer with the electrolyte or electrolyte on the one hand, and promote the rapid migration of lithium ions on the other hand, thereby effectively avoiding the untimely deintercalation of lithium ions at the negative electrode causing the growth of lithium dendrites, as well as the problems such as the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by the infinite volume change rate. Therefore, the negative electrode plate obtained by the method for preparing the negative electrode plate of the present invention can improve the interface problem of metal lithium in the application of secondary batteries, avoid the problems such as the continuous thickening of the SEI film, the continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the diaphragm, thereby helping to improve the cycle stability of the lithium metal battery using the negative electrode plate.

[0044] In addition, the method for preparing a negative electrode sheet according to the above embodiment of the present invention may also have the following additional technical features:

[0045] In some embodiments of the present invention, the method further includes forming a fourth active material layer on the second side of the current collector, the fourth active material layer comprising metallic lithium; and forming a third artificial SEI layer on the side of the fourth active material layer away from the current collector, the third artificial SEI layer comprising a lithiation and a metallic lithium alloy. This can improve the cycling stability of lithium metal batteries.

[0046] In some embodiments of the present invention, the method further includes: forming a fifth active material layer on the second side of the current collector, the fifth active material layer comprising metallic lithium; forming a sixth active material layer on a side of the fifth active material layer away from the current collector, the sixth active material layer comprising a metallic lithium alloy; and forming a fourth artificial SEI layer on a side of the sixth active material layer away from the fifth active material layer, the fourth artificial SEI layer comprising a lithiation. This can improve the cycling stability of lithium metal batteries.

[0047] In its third aspect, the present invention provides a lithium metal battery. According to an embodiment of the present invention, the lithium metal battery includes the aforementioned negative electrode sheet or a negative electrode sheet obtained using the aforementioned method for preparing a negative electrode sheet. As a result, the lithium metal battery exhibits high cycling stability.

[0048] In addition, the lithium metal battery according to the above embodiment of the present invention may also have the following additional technical features:

[0049] In some embodiments of the present invention, the lithium metal battery includes a liquid battery, a semi-solid battery and an all-solid battery.

[0050] In some embodiments of the present invention, the lithium metal battery includes a liquid battery and a semi-solid battery, and the liquid battery and the semi-solid battery include an electrolyte, and the electrolyte includes a lithium salt and a solvent.

[0051] In some embodiments of the present invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonyl-n-perfluorobutylsulfonylimide, lithium fluorosulfonyl-n-perfluorobutylsulfonylimide, lithium bis(oxalatoborate) and tris(trifluoromethylsulfonyl)methyllithium.

[0052] In some embodiments of the present invention, the solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyl-tetrahydrofuran, dimethoxydimethyl ether, 1,2-dimethoxyethane, 1,3-dioxolane and acetonitrile.

[0053] In some embodiments of the present invention, the electrolyte further includes additives, and the additives include at least one of film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, water and HF content control additives, low-temperature additives and negative electrode stabilizers.

[0054] In some embodiments of the present invention, the lithium metal battery includes a semi-solid-state battery and an all-solid-state battery, and the semi-solid-state battery and the all-solid-state battery include an electrolyte, and the electrolyte includes at least one of an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte, and the inorganic solid electrolyte includes at least one of an oxide solid electrolyte, a sulfide solid electrolyte and a halide solid electrolyte.

[0055] In a fourth aspect of the present invention, a method for preparing a lithium metal battery is provided. According to an embodiment of the present invention, the method includes: providing a negative electrode plate, the negative electrode plate including a current collector having a first side and a second side opposite to each other, the first side of the current collector being sequentially provided with a first active material layer, a second active material layer, and a first artificial SEI layer along a direction away from the current collector, the first active material layer including metallic lithium, the second active material layer including a metallic lithium alloy, and the first artificial SEI layer including a lithiate, and the second side of the current collector being sequentially provided with a fourth active material layer and a metal compound layer along a direction away from the current collector, the fourth active material layer including metallic lithium; assembling the negative electrode plate into a battery and charging the battery so that the metal compound layer forms a third artificial SEI layer in situ during the battery charging process, the third artificial SEI layer including a lithiate and a metallic lithium alloy, wherein the metal compound layer includes a compound of at least one of halogen, oxygen, nitrogen, sulfur, and phosphorus and M, and M including at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, silver, tin, and bismuth. Therefore, the lithium metal battery obtained by this method has high cycle stability and effectively avoids the process complexity caused by multi-layer deposition.

[0056] In its fifth aspect, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device comprises the aforementioned lithium metal battery or a lithium metal battery obtained by the aforementioned method for preparing a lithium metal battery. The electrical device and the aforementioned lithium metal battery or the aforementioned method for preparing a lithium metal battery have the same advantages over the prior art and are not further elaborated here.

[0057] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0059] FIG1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present invention;

[0060] FIG2 is a schematic structural diagram of a current collector according to an embodiment of the present invention;

[0061] FIG3 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present invention;

[0062] FIG4 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present invention;

[0063] FIG5 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present invention;

[0064] FIG6 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present invention;

[0065] FIG7 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present invention;

[0066] FIG8 is a schematic structural diagram of a negative electrode sheet according to another embodiment of the present invention;

[0067] FIG9 is a schematic flow chart of a method for preparing a negative electrode sheet according to one embodiment of the present invention.

[0068] Reference numerals:

[0069] 1000-negative electrode; 10-current collector; 11-base film; 12-first conductive layer; 13-second conductive layer; 20-first active material layer; 30-second active material layer; 40-first artificial SEI layer; 50-third active material layer; 60-second artificial SEI layer; 70-fourth active material layer; 80-third artificial SEI layer; 90-fifth active material layer; 100-sixth active material layer; 110-fourth artificial SEI layer. DETAILED DESCRIPTION

[0070] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0071] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0072] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0073] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0074] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0075] In a first aspect, the present invention provides a negative electrode sheet. According to an embodiment of the present invention, referring to FIG1 , the negative electrode sheet 1000 includes a current collector 10 , a first active material layer 20 , a second active material layer 30 , and a first artificial SEI (solid electrolyte membrane) layer 40 .

[0076] According to an embodiment of the present invention, the current collector 10 includes a first side and a second side that are opposite to each other. It should be noted that the specific type and thickness of the current collector 10 are not particularly limited and can be selected by those skilled in the art based on actual needs. For example, the current collector 10 can be a metal foil current collector or a composite current collector, and the thickness of the current collector 10 can be 1 μm to 10 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. The thickness of the metal foil current collector is preferably 4 μm to 10 μm.

[0077] According to a specific embodiment of the present invention, the current collector 10 is a metal foil current collector, which may include at least one of copper, aluminum, zinc, nickel, and chromium. Optionally, the metal foil current collector includes at least one of copper, nickel, a copper-nickel alloy, and a copper-zinc alloy.

[0078] According to a specific embodiment of the present invention, referring to FIG. 2 , the current collector 10 is a composite current collector, including a base film 11 , a first conductive layer 12 , and a second conductive layer 13 .

[0079] According to a specific embodiment of the present invention, the base film 11 is made of a polymer. The base film 11 is made of a polymer and has a lower density than metal foils such as copper foil. Therefore, the current collector 10 prepared using the polymer also has a lower density than current collectors made of metal foils such as copper foil, thereby improving the energy density of the battery.

[0080] It should be noted that the specific type of the above-mentioned base film 11 is not particularly limited. Those skilled in the art can select it according to actual needs. For example, it can include at least one of polyethylene (PE), polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), polyamide (PA), polyphenylene sulfide (PPS), and polyethylene naphthalate (PEN). Optionally, the base film 11 includes at least one of PET, PP, and PI; alternatively, the base film 11 includes PI and / or PPS. PI and PPS have flame retardant effects, thereby reducing the fire problem caused by lithium dendrites piercing the film and short-circuiting.

[0081] According to a specific embodiment of the present invention, the thickness of the base film 11 may be 1 μm-10 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0082] According to a specific embodiment of the present invention, referring to FIG. 2 , the first conductive layer 12 is disposed on one side of the base film 11 . By disposing the first conductive layer 12 on one side of the base film 11 , the conductivity of the current collector 10 can be improved.

[0083] It should be noted that the material and thickness of the first conductive layer 12 are not particularly limited. Those skilled in the art can choose according to actual needs, as long as it has excellent conductivity and mechanical properties. For example, the material of the first conductive layer 12 may include at least one of copper, aluminum, zinc, nickel and chromium, and the thickness of the first conductive layer 12 can be 0.3μm-10μm, for example, 0.3μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc.

[0084] According to a specific embodiment of the present invention, referring to FIG. 2 , the second conductive layer 13 is disposed on the other side opposite to the base film 11 . By disposing the second conductive layer 13 on the other side opposite to the base film 11 , the conductivity of the current collector 10 can be further improved.

[0085] It should be noted that the material and thickness of the second conductive layer 13 are not particularly limited. Those skilled in the art can choose according to actual needs, as long as it has excellent conductivity and mechanical properties. For example, the material of the second conductive layer 13 may include at least one of copper, aluminum, zinc, nickel and chromium, and the thickness of the second conductive layer 13 can be 0.3μm-10μm, for example, 0.3μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc.

[0086] According to a specific embodiment of the present invention, the first conductive layer 12 and the second conductive layer 13 can be independently prepared by physical vapor deposition (PVD), chemical vapor deposition (CVD) or water electroplating. For example, when copper is used as the first conductive layer 12 or the second conductive layer 13, it can be prepared on the base film 11 by a one-step method, a two-step method or a three-step method, wherein the one-step method includes a chemical deposition one-step method, a vacuum magnetron sputtering one-step method and a vacuum evaporation one-step method. The chemical deposition one-step method deposits the copper layer by chemical reaction, the vacuum magnetron sputtering one-step method deposits the copper layer by repeated magnetron sputtering, and the vacuum evaporation one-step method deposits the copper layer by repeated evaporation. The two-step method is to first use magnetron sputtering to prime, and then use water electroplating to thicken the copper layer. The three-step method is to first use magnetron sputtering to prime, then use vacuum evaporation, and finally use water electroplating to thicken the copper layer.

[0087] Therefore, the negative electrode plate 1000 of the present invention can improve the mechanical strength and mechanical properties of the negative electrode plate 1000 by adopting a composite current collector as the current collector 10. On the other hand, compared with metal foil current collectors such as copper foil, the composite current collector has the characteristics of low manufacturing cost, high safety and good compatibility. On the other hand, the density of the composite current collector is lower than that of metal foil current collectors such as copper foil (weight reduction of more than 60%), which can improve the energy density of the battery.

[0088] According to an embodiment of the present invention, referring to FIG1 , a first active material layer 20, a second active material layer 30, and a first artificial SEI layer 40 are sequentially arranged on a first side of the current collector 10 in a direction away from the current collector 10. The first active material layer 20 includes metallic lithium, the second active material layer 30 includes a metallic lithium alloy, and the first artificial SEI layer 40 includes a lithium compound. The inventors have discovered that by sequentially arranging the first active material layer 20, the second active material layer 30, and the first artificial SEI layer 40 on the first side of the current collector 10 in a direction away from the current collector 10, the first active material layer 20 includes metallic lithium, which can be used as a supplementary lithium source to improve the cycle life of the battery. The second active material layer 30 includes a metallic lithium alloy. On the one hand, this can prevent the metallic lithium with high reactivity in the first active material layer 20 from directly contacting the electrolyte or the electrolyte. On the other hand, this can allow the metallic lithium to undergo an alloying reaction with the metallic lithium alloy in the second active material layer 30 during the charge and discharge process of the battery, which is beneficial to the uniform deposition of metallic lithium, thereby effectively avoiding the metal. The uneven deposition of lithium causes the growth of lithium dendrites, and the infinite volume change rate causes the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm. The first artificial SEI layer 40 includes a lithium compound. On the one hand, it can further avoid the direct contact between the highly reactive metallic lithium in the first active material layer 20 and the electrolyte or electrolyte. On the other hand, it can promote the rapid migration of lithium ions, effectively avoiding the untimely deintercalation of lithium ions at the negative electrode causing the growth of lithium dendrites, as well as the infinite volume change rate causes the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm. This is beneficial to improving the cycle stability of the lithium metal battery using the negative electrode sheet 1000.

[0089] According to a specific embodiment of the present invention, referring to FIG. 3 , the first active material layer 20 may be disposed on the first conductive layer 12 .

[0090] It should be noted that the thicknesses of the first active material layer 20, the second active material layer 30, and the first artificial SEI layer 40 are not particularly limited and can be selected by those skilled in the art according to actual needs. As a preferred embodiment, the thicknesses of the first active material layer 20 and the second active material layer 30 can each independently be 0.1 μm to 100 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc., and the thickness of the first artificial SEI layer 40 can be 0.1 μm to 1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0091] According to a specific embodiment of the present invention, the specific composition of the metal lithium alloy is not particularly limited, and those skilled in the art can select it according to actual needs. For example, it can include an alloy formed by metal lithium and at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth. Specifically, the content of lithium element in the above-mentioned metal lithium alloy can be 0.1atm%-99.9atm%, for example, it can be 0.1atm%, 1atm%, 2atm%, 5atm%, 15atm%, 25atm%, 35atm%, 45atm%, 55atm%, 65atm%, 75atm%, 85atm%, 95atm%, 99.9atm%, etc. In this way, the problems of lithium dendrite growth caused by uneven deposition of metal lithium on the negative electrode surface during the cycle of lithium metal batteries, continuous thickening of SEI film, dead lithium, and lithium dendrites piercing the diaphragm can be solved.

[0092] According to a specific embodiment of the present invention, the specific type of the lithium compound is not particularly limited and can be selected by those skilled in the art according to actual needs. For example, the lithium compound may include a compound of at least one of halogen (such as fluorine), oxygen, nitrogen, sulfur, and phosphorus with lithium. Alternatively, the lithium compound may include at least one of lithium fluoride (LiF), lithium oxide (Li2O), lithium sulfide (Li2S), lithium nitride (Li3N), lithium phosphide (Li3P), and lithium phosphorus oxynitride (LiPON).

[0093] According to a specific embodiment of the present invention, referring to FIG4 , the negative electrode plate 1000 further includes a third active material layer 50 , which is disposed on the second side of the current collector 10 and includes a metallic lithium alloy. By disposing the third active material layer 50 including a metallic lithium alloy on the second side of the current collector 10 , an alloying reaction can occur between the metallic lithium and the metallic lithium alloy in the third active material layer 50 during the battery charge and discharge process, further facilitating the uniform deposition of metallic lithium and avoiding the growth of lithium dendrites caused by uneven deposition of metallic lithium, as well as problems such as continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the separator caused by an infinite volume change rate. This further improves the cycling stability of the lithium metal battery using the negative electrode plate 1000 . Specifically, the third active material layer 50 can be disposed on the second conductive layer 13 .

[0094] It should be noted that the thickness of the third active material layer 50 is not particularly limited and can be selected by those skilled in the art according to actual needs. As a preferred embodiment, the thickness of the third active material layer 50 can be 0.1 μm-100 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc.

[0095] According to a specific embodiment of the present invention, referring to FIG5 , the negative electrode sheet 1000 further includes a second artificial SEI layer 60, which is disposed on a side of the third active material layer 50 away from the current collector 10. The second artificial SEI layer 60 includes a lithium compound. Providing the second artificial SEI layer 60 including a lithium compound on a side of the third active material layer 50 away from the current collector 10 further facilitates the rapid migration of lithium ions, thereby effectively preventing the growth of lithium dendrites caused by untimely lithium ion deintercalation at the negative electrode, as well as problems such as continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the separator caused by an infinite volume change rate. This further improves the cycling stability of lithium metal batteries using the negative electrode sheet 1000.

[0096] It should be noted that the thickness of the second artificial SEI layer 60 is not particularly limited and can be selected by those skilled in the art according to actual needs. As a preferred embodiment, the thickness of the second artificial SEI layer 60 can be 0.1 μm to 1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0097] According to a specific embodiment of the present invention, referring to FIG6 , the negative electrode sheet 1000 further includes a fourth active material layer 70 and a third artificial SEI layer 80. The fourth active material layer 70 and the third artificial SEI layer 80 are sequentially arranged on the second side of the current collector 10 in a direction away from the current collector 10. The fourth active material layer 70 includes metallic lithium, and the third artificial SEI layer 80 includes a lithium compound and a metallic lithium alloy. By sequentially arranging the fourth active material layer 70 and the third artificial SEI layer 80 on the second side of the current collector 10 in a direction away from the current collector 10, the fourth active material layer 70 includes metallic lithium, which can serve as a supplementary lithium source to improve the cycle life of the battery. The third artificial SEI layer 80 includes a lithium compound and a metallic lithium alloy. On the one hand, the third artificial SEI layer 80 can prevent the highly reactive metallic lithium in the fourth active material layer 70 from directly contacting the electrolyte or the electrolyte. On the other hand, the lithium compound in the third artificial SEI layer 80 can further facilitate the rapid migration of lithium ions, thereby effectively avoiding the lithium ion In the case of untimely lithium dendrite growth caused by the negative electrode deintercalation, and the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by the infinite volume change rate, on the other hand, the metal lithium alloy in the third artificial SEI layer 80 can react with the metal lithium during the battery charge and discharge process, which is further conducive to the uniform deposition of metal lithium, effectively avoiding the uneven deposition of metal lithium causing lithium dendrite growth, and the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by the infinite volume change rate, thereby further improving the cycle stability of the lithium metal battery using the negative electrode plate 1000. Specifically, the fourth active material layer 70 can be provided on the second conductive layer 13.

[0098] According to a specific embodiment of the present invention, in the third artificial SEI layer 80, the lithiation may include a compound of at least one of halogen, oxygen, nitrogen, sulfur and phosphorus and lithium, and the metal lithium alloy may include Li-M, wherein M includes at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, silver, tin and bismuth, and the molar ratio of the lithiation to Li-M in the third artificial SEI layer 80 may be (0.1-10):1, for example, it may be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, 10:1, etc.

[0099] It should be noted that the thickness of the fourth active material layer 70 and the third artificial SEI layer 80 is not particularly limited and can be selected by those skilled in the art according to actual needs. As a preferred embodiment, the thickness of the fourth active material layer 70 can be 0.1 μm-100 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc. The thickness of the third artificial SEI layer 80 can be 0.1 μm-1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0100] According to a specific embodiment of the present invention, referring to Figure 7, the above-mentioned negative electrode sheet 1000 also includes a fifth active material layer 90 and a sixth active material layer 100, and the fifth active material layer 90 and the sixth active material layer 100 are sequentially arranged on the second side of the current collector 10 in a direction away from the current collector 10, the fifth active material layer 90 includes metallic lithium, and the sixth active material layer 100 includes a metallic lithium alloy. By sequentially disposing a fifth active material layer 90 and a sixth active material layer 100 on the second side of the current collector 10 in a direction away from the current collector 10, the fifth active material layer 90 includes metallic lithium, which can serve as a supplementary lithium source to improve the cycle life of the battery, and the sixth active material layer 100 includes a metallic lithium alloy. On the one hand, this can prevent the highly reactive metallic lithium in the fifth active material layer 90 from directly contacting the electrolyte or electrolyte. On the other hand, it can cause the metallic lithium and the metallic lithium alloy in the sixth active material layer 100 to undergo an alloying reaction during the battery charge and discharge process, which is conducive to the uniform deposition of metallic lithium, thereby effectively avoiding the growth of lithium dendrites caused by uneven deposition of metallic lithium, as well as the problems of continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the separator caused by an infinite volume change rate, thereby improving the cycle stability of the lithium metal battery using the negative electrode sheet 1000. Specifically, the fifth active material layer 90 can be disposed on the second conductive layer 13.

[0101] It should be noted that the thickness of the fifth active material layer 90 and the sixth active material layer 100 is not particularly limited and can be selected by those skilled in the art according to actual needs. As a preferred embodiment, the thickness of the fifth active material layer 90 and the sixth active material layer 100 can be independently 0.1 μm-100 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc.

[0102] According to a specific embodiment of the present invention, referring to FIG8 , the negative electrode sheet 1000 further includes a fourth artificial SEI layer 110. The fourth artificial SEI layer 110 is disposed on a side of the sixth active material layer 100 away from the current collector 10, and the fourth artificial SEI layer 110 includes a lithium compound. Providing the fourth artificial SEI layer 110 including a lithium compound on a side of the sixth active material layer 100 away from the current collector 10 further facilitates the rapid migration of lithium ions, thereby effectively preventing the growth of lithium dendrites caused by untimely lithium ion deintercalation at the negative electrode, as well as problems such as continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the separator caused by an infinite volume change rate. This further improves the cycling stability of lithium metal batteries using the negative electrode sheet 1000.

[0103] It should be noted that the thickness of the fourth artificial SEI layer 110 is not particularly limited and can be selected by those skilled in the art according to actual needs. As a preferred embodiment, the thickness of the fourth artificial SEI layer 110 can be 0.1 μm to 1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0104] According to a specific embodiment of the present invention, the first active material layer 20, the second active material layer 30, the third active material layer 50, the fourth active material layer 70, the fifth active material layer 90 and the sixth active material layer 100 can be independently prepared by rolling (i.e., rolling the metal strip as the active material layer to the surface of the current collector or other active material layer) or physical vapor deposition (PVD, such as magnetron sputtering, vacuum evaporation, etc.), preferably physical vapor deposition method, thereby helping to reduce the thickness of the active material layer and achieve uniform deposition, thereby reducing the amount of active material used and reducing battery cost. Optionally, the metal lithium alloy Li-M can be magnetron sputtered to sputter the metal M onto the surface of the metal Li layer to form an active material layer including a metal lithium alloy. Alternatively, the metal lithium alloy Li-M can be deposited by vacuum evaporation, that is, metal Li and metal M in the shape of bars, blocks, etc. are placed in containers (such as evaporation boats, crucibles, etc.), respectively. Considering the melting points of metal Li and metal M, different evaporation methods (such as resistance heating, electron beam evaporation, high-frequency heating, laser heating, etc.) and different evaporation temperatures can be used to control the composition and deposition rate of the metal lithium alloy under the premise of setting a reasonable evaporation chamber pressure and substrate temperature.

[0105] According to a specific embodiment of the present invention, the first artificial SEI layer 40, the second artificial SEI layer 60, and the fourth artificial SEI layer 110 can be independently formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), or other methods to directly form a layer of a compound formed by metallic lithium with a halogen, oxygen, nitrogen, sulfur, or phosphorus, such as lithium fluoride, lithium oxide, lithium nitride, lithium sulfide, or lithium phosphide. Furthermore, lithium phosphate (Li3PO4) can be magnetron sputtered under a nitrogen atmosphere to form a lithium phosphorus oxynitride (LiPON). Furthermore, a compound formed by lithium with a halogen, oxygen, nitrogen, sulfur, or phosphorus, such as at least one of lithium fluoride (LiF), lithium oxide (Li2O), lithium sulfide (Li2S), lithium nitride (Li3N), lithium phosphide (Li3P), or lithium phosphorus oxynitride (LiPON), can also be directly applied to the negative electrode surface using dry coating or wet coating methods.

[0106] According to a specific embodiment of the present invention, the third artificial SEI layer 80 can be generated by an in-situ method, that is, a metal compound layer including a compound of at least one of halogen, oxygen, nitrogen, sulfur and phosphorus and M is formed on the fourth active material layer 70 including metallic lithium, so that the metal compound layer reacts with lithium atoms from the positive electrode to generate lithium compounds and metallic lithium alloys during battery charging.

[0107] Therefore, the use of the negative electrode plate 1000 of the present invention can improve the interface problems of metallic lithium in secondary battery applications, avoid problems such as continuous thickening of the SEI film, continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the diaphragm, thereby helping to improve the cycle stability of the lithium metal battery using the negative electrode plate 1000.

[0108] In a second aspect of the present invention, a method for preparing a negative electrode sheet is provided. According to an embodiment of the present invention, referring to FIG9 , the method comprises:

[0109] S100: Providing a current collector, the current collector including a first side and a second side opposite to each other

[0110] In this step, a current collector 10 is provided, comprising a first side and a second side opposite to each other. It should be noted that the specific method for preparing the current collector 10 is not particularly limited and may, for example, include forming a first conductive layer 12 on one side of a base film 11 and forming a second conductive layer 13 on a side of the base film 11 away from the first conductive layer 12. Forming the first conductive layer 12 on one side of the base film 11 improves the conductivity of the current collector 10, while forming the second conductive layer 13 on the opposite side of the base film 11 further improves the conductivity of the current collector 10.

[0111] S200: forming a first active material layer on the first side of the current collector, the first active material layer including metallic lithium

[0112] In this step, a first active material layer 20 comprising metallic lithium is formed on the first side of the current collector 10. The inventors have discovered that forming the first active material layer 20 comprising metallic lithium on the first side of the current collector 10 can serve as a supplementary lithium source to improve the cycle life of the battery.

[0113] According to a specific embodiment of the present invention, the first active material layer 20 may be formed on the first conductive layer 12 .

[0114] S300: forming a second active material layer on the first active material layer away from the current collector, the second active material layer including a metal lithium alloy

[0115] In this step, a second active material layer 30 is formed on the side of the first active material layer 20 away from the current collector 10, and the second active material layer 30 includes a metallic lithium alloy. The inventors have discovered that by forming the second active material layer 30 including a metallic lithium alloy on the side of the first active material layer 20 away from the current collector 10, on the one hand, direct contact between the highly reactive metallic lithium in the first active material layer 20 and the electrolyte or electrolyte can be avoided, and on the other hand, an alloying reaction can occur between the metallic lithium and the metallic lithium alloy in the second active material layer 30 during the charge and discharge process of the battery, which is conducive to the uniform deposition of metallic lithium, avoids the growth of lithium dendrites caused by uneven deposition of metallic lithium, and avoids problems such as continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by an infinite volume change rate, thereby improving the cycle stability of the lithium metal battery.

[0116] S400: forming a first artificial SEI layer on the side of the second active material layer away from the first active material layer, the first artificial SEI layer including lithium

[0117] In this step, a first artificial SEI layer 40 is formed on the side of the second active material layer 30 away from the first active material layer 20. The first artificial SEI layer 40 includes a lithium compound. The inventors have discovered that by forming the first artificial SEI layer 40 including a lithium compound on the side of the second active material layer 30 away from the first active material layer 20, on the one hand, it can further prevent the highly reactive metallic lithium in the first active material layer 20 from directly contacting the electrolyte or electrolyte. On the other hand, it can promote the rapid migration of lithium ions, effectively avoiding the growth of lithium dendrites caused by the untimely deintercalation of lithium ions at the negative electrode, as well as problems such as the continuous thickening of the SEI film, dead lithium, and lithium dendrites piercing the separator caused by an infinite volume change rate, thereby improving the cycle stability of lithium metal batteries.

[0118] Therefore, the negative electrode plate obtained by the method for preparing the negative electrode plate of the present invention can improve the interface problem of metallic lithium in the application of secondary batteries, avoid the problems of continuous thickening of SEI film, continuous growth of lithium dendrites, dead lithium, lithium dendrites piercing the diaphragm, etc., thereby helping to improve the cycle stability of lithium metal batteries.

[0119] It should be noted that the materials and thicknesses of the base film 11, the first conductive layer 12, the second conductive layer 13, the first active material layer 20, the second active material layer 30 and the first artificial SEI layer 40, as well as the preparation methods of the first conductive layer 12, the second conductive layer 13, the first active material layer 20, the second active material layer 30 and the first artificial SEI layer 40 have been described in detail above and will not be repeated here.

[0120] According to a specific embodiment of the present invention, the above method further includes: forming a fourth active material layer 70 on the second side of the current collector 10, the fourth active material layer 70 including metallic lithium; forming a third artificial SEI layer 80 on the side of the fourth active material layer 70 away from the current collector 10, the third artificial SEI layer 80 including a lithium compound and a metallic lithium alloy. By forming the fourth active material layer 70 including metallic lithium on the second side of the current collector 10, it can be used as a supplementary lithium source to improve the cycle life of the battery. By forming the third artificial SEI layer 80 including a lithium compound and a metallic lithium alloy on the side of the fourth active material layer 70 away from the current collector 10, on the one hand, the third artificial SEI layer 80 can prevent the metallic lithium with high reactivity in the fourth active material layer 70 from directly contacting the electrolyte or the electrolyte, and on the other hand, the lithium compound in the third artificial SEI layer 80 can further facilitate the rapid migration of lithium ions, thereby effectively avoiding the occurrence of lithium ion stagnation. On the other hand, the metal lithium alloy in the third artificial SEI layer 80 can react with the metal lithium to form an alloy during the battery charging and discharging process, which is further beneficial to the uniform deposition of metal lithium, effectively avoiding the growth of lithium dendrites caused by uneven deposition of metal lithium, as well as the continuous thickening of SEI film, dead lithium, and lithium dendrites piercing the diaphragm caused by the infinite volume change rate, thereby further improving the cycle stability of lithium metal batteries.

[0121] According to a specific embodiment of the present invention, the above method also includes: forming a fifth active material layer 90 on the second side of the current collector 10, the fifth active material layer 90 includes metallic lithium; forming a sixth active material layer 100 on the side of the fifth active material layer 90 away from the current collector 10, the sixth active material layer 100 includes a metallic lithium alloy; forming a fourth artificial SEI layer 110 on the side of the sixth active material layer 100 away from the fifth active material layer 90, the fourth artificial SEI layer 110 includes a lithium compound. The inventors found that by forming a fifth active material layer 90 including metallic lithium on the second side of the current collector 10, it can be used as a supplementary lithium source to further improve the cycle life of the battery; by forming a sixth active material layer 100 including a metallic lithium alloy on the side of the fifth active material layer 90 away from the current collector 10, on the one hand, the metallic lithium with high reactivity in the fifth active material layer 90 can be prevented from directly contacting the electrolyte or electrolyte, and on the other hand, the metallic lithium and the metallic lithium alloy in the sixth active material layer 100 can be alloyed during the charge and discharge process of the battery, which is further conducive to the uniform deposition of metallic lithium, and avoids the growth of lithium dendrites caused by uneven deposition of metallic lithium, as well as infinite The volume change rate causes the SEI film to continue to thicken, dead lithium, lithium dendrites piercing the diaphragm and other problems; by forming a fourth artificial SEI layer 110 including a lithium compound on the side of the sixth active material layer 100 away from the fifth active material layer 90, on the one hand, it can further avoid the direct contact between the highly reactive metallic lithium in the fifth active material layer 90 and the electrolyte or electrolyte, and on the other hand, it can further facilitate the rapid migration of lithium ions, effectively avoiding the growth of lithium dendrites caused by the untimely deintercalation of lithium ions at the negative electrode, as well as the problems of the SEI film to continue to thicken, dead lithium, lithium dendrites piercing the diaphragm caused by the infinite volume change rate, thereby further helping to improve the cycle stability of lithium metal batteries.

[0122] It should be noted that the materials, thicknesses and preparation methods of the fourth active material layer 70 , the fifth active material layer 90 , the sixth active material layer 100 , the third artificial SEI layer 80 and the fourth artificial SEI layer 110 have been described in detail above and will not be repeated here.

[0123] In its third aspect, the present invention provides a lithium metal battery. According to an embodiment of the present invention, the lithium metal battery comprises the aforementioned negative electrode sheet or a negative electrode sheet obtained using the aforementioned method for preparing a negative electrode sheet. As a result, the lithium metal battery exhibits high cycling stability. It should be noted that the features and advantages described above for the negative electrode sheet also apply to this lithium metal battery and will not be further elaborated here.

[0124] According to an embodiment of the present invention, the lithium metal battery may include a liquid battery, a semi-solid battery and an all-solid battery.

[0125] According to a specific embodiment of the present invention, the lithium metal battery may include a liquid battery and a semi-solid battery, and the liquid battery and the semi-solid battery include an electrolyte.

[0126] According to a specific embodiment of the present invention, the above-mentioned lithium metal battery may include the above-mentioned negative electrode sheet or the negative electrode sheet obtained by the above-mentioned method for preparing the negative electrode sheet, a positive electrode sheet, a separator and an electrolyte, which are composed of a liquid laminated soft-pack battery, a liquid wound battery or a liquid cylindrical battery.

[0127] According to a specific embodiment of the present invention, the above-mentioned lithium metal battery may also include a semi-solid laminated soft-pack battery, a semi-solid wound battery or a semi-solid cylindrical battery consisting of the above-mentioned negative electrode sheet or the negative electrode sheet obtained by the above-mentioned method for preparing the negative electrode sheet, a positive electrode sheet and a gel electrolyte.

[0128] According to a specific embodiment of the present invention, the above-mentioned lithium metal battery may also include a semi-solid laminated soft-pack battery, a semi-solid wound battery or a semi-solid cylindrical battery consisting of the above-mentioned negative electrode sheet or the negative electrode sheet obtained by the above-mentioned method for preparing the negative electrode sheet, a positive electrode sheet, a gel electrolyte and an optional 0.5wt%-50wt% additive.

[0129] According to a specific embodiment of the present invention, the above-mentioned electrolyte mainly includes a lithium salt, a solvent and an optional additive. Specifically, the solvent may include carbonates (such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (BL)), ethers (such as tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (2-Me-THF), dimethoxydimethyl ether (DMM), 1,2-dimethoxyethane (DME)), 1,3-dioxolane (DOL), nitriles (such as acetonitrile (AN)), etc.; lithium salts may include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), other organic lithium salts (such as lithium trifluoromethylsulfonate (LiCF3SO), difluoromethanesulfonate (DMF ... Lithium trifluoromethanesulfonyl imide (LiTFSI), lithium bisfluorosulfonyl imide (LiFSI), lithium trifluoromethanesulfonyl-perfluorobutylsulfonyl imide (LiTNFSI), lithium fluorosulfonyl-perfluorobutylsulfonyl imide (LiFNFSI), lithium bisoxalatoborate (LiBOB), tris(trifluoromethylsulfonyl)methyllithium (LiC(SO2CF3)3), etc.); additives may include film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, water and HF content control additives (i.e., additives for controlling the water and HF content in the electrolyte), low-temperature additives (i.e., general additives for improving low-temperature performance), and may also include negative electrode stabilizers, i.e., additives for improving the interface stability of the metallic lithium negative electrode (e.g., fluoroethylene carbonate (FEC), lithium nitrate (LiNO3), etc.).

[0130] According to a specific embodiment of the present invention, the above-mentioned lithium metal battery may include a semi-solid-state battery and an all-solid-state battery, and the semi-solid-state battery and the all-solid-state battery include an electrolyte, and the electrolyte may include at least one of an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte.

[0131] According to a specific embodiment of the present invention, the above-mentioned lithium metal battery may also include a solid-state laminated soft-pack battery, a solid-state wound battery or a solid-state cylindrical battery consisting of the above-mentioned negative electrode sheet or the negative electrode sheet obtained by the above-mentioned method for preparing the negative electrode sheet, a positive electrode sheet and a solid-state electrolyte.

[0132] According to a specific embodiment of the present invention, the specific types of the above-mentioned positive electrode sheet and its positive electrode active material are not particularly limited, and those skilled in the art can select according to actual needs. For example, the positive electrode sheet can be a positive electrode sheet using a metal foil current collector, or a positive electrode sheet using a composite current collector, and its positive electrode active material can include lithium nickel cobalt manganese oxide (LiN x M y C zO2, x+y+z=1), lithium manganese iron phosphate (LiFe a Mn b PO4, a+b=1), at least one of lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickelate, lithium-rich manganese-based positive electrode material, lithium nickel manganate (LMNO) and lithium vanadium phosphate (Li3V2(PO4)3, LiVOPO4).

[0133] According to a specific embodiment of the present invention, the separator may include polypropylene (PP) and / or polyethylene (PE).

[0134] According to a specific embodiment of the present invention, the above-mentioned solid electrolyte may include an inorganic solid electrolyte (such as an oxide solid electrolyte, a sulfide solid electrolyte, a halide solid electrolyte), a polymer solid electrolyte and a composite solid electrolyte (such as a composite solid electrolyte based on a polymer matrix and an inorganic filler). Specifically, the oxide solid electrolyte may include a NASICON type (stable structure, such as LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3)、LAGP(Li 1.5 Al 0.5 Ge 1.5 P3O 12 ), perovskite type, garnet type (highest conductivity, 10 -3 S / cm, which has good stability to metallic lithium, such as lithium lanthanum zirconium oxide (LLZO); sulfide solid electrolytes can include binary compounds (such as Li2S-SiS2 and Li2S-P2S5, Li2S-GeS2, etc.), ternary compounds (such as Li2S-MS2-P2S5 (M=Si, Ge, Sn, Al, etc.), and Li6PS5X (X=F, Cl, Br, I); halide solid electrolytes can include Li a MX4 type (X represents halogen elements, such as Li2MnCl4, Li2ZnCl4 formed by divalent metal ions, and halide electrolytes formed by trivalent and other valence metal ions M, such as LiYbF4, LiAlF4), Li a MX6 (such as Li3YCl6 (LYC) and Li3BrCl6 (LYB)) and Li aMX8 type (such as Li6CoCl8). The polymer solid electrolyte can include polyethylene oxide (PEO), polycarbonate, polytrimethylene carbonate (PTMC), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoroethylene copolymer, lithium polyacrylate (PAL) and other polymer matrices, LATP, lithium lanthanum zirconium oxide (LLZO), aluminum oxide (Al2O3), metal organic frameworks (MOFs) and other inorganic fillers and LiAsF6, lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4) and other lithium salts. Specifically, the gel electrolyte can include at least one of the above solid electrolytes and at least one of the above electrolytes.

[0135] In a fourth aspect of the present invention, a method for preparing a lithium metal battery is provided. According to an embodiment of the present invention, the method includes: providing a negative electrode plate, the negative electrode plate including a current collector having a first side and a second side opposite to each other, the first side of the current collector being provided with a first active material layer, a second active material layer, and a first artificial SEI layer in sequence along a direction away from the current collector, the first active material layer comprising metallic lithium, the second active material layer comprising a metallic lithium alloy, the first artificial SEI layer comprising a lithiation, the second side of the current collector being provided with a fourth active material layer and a metal compound layer in sequence along a direction away from the current collector, the fourth active material layer comprising metallic lithium; The negative electrode sheets are assembled into a battery and charged so that the metal compound layer forms a third artificial SEI layer in situ during the battery charging process, and the third artificial SEI layer includes a lithiate and a metallic lithium alloy (i.e., the third artificial SEI layer including a lithiate and a metallic lithium alloy is generated by an in-situ method), wherein the metal compound layer includes a compound of at least one of halogen, oxygen, nitrogen, sulfur and phosphorus and M, and M includes at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, silver, tin and bismuth.

[0136] Specifically, the battery assembled with the above-mentioned negative electrode sheets can be charged under the conditions of 0.01C-50C.

[0137] According to a specific embodiment of the present invention, the metal compound layer may include M x+ F - x (i.e. the compound of fluorine and M), during the battery charging process, M x+ F - x Reacts with lithium atoms from the positive electrode during battery charging to generate M and lithium fluoride (LiF). M can react with metallic lithium to form Li-M alloy. The reactions involved are as follows: Mx+ F - x +x Li=M+x LiF, M+Li=Li-M.

[0138] According to a specific embodiment of the present invention, the metal compound layer may include M x+ O 2- x / 2 (i.e., a compound of oxygen and M). During battery charging, M x+ O 2- x / 2 Reacts with lithium atoms from the positive electrode during battery charging to generate M and lithium oxide (Li2O). M can react with metallic lithium to form Li-M alloy. The reactions involved are as follows: M x+ O 2- x / 2 +x Li=M+x / 2Li2O, M+Li=Li-M.

[0139] It should be noted that M x+ O 2- x / 2 It can be a conductive metal oxide or a non-conductive metal oxide. Among them, the conductive metal oxide can be divided into n-type conductive oxides (such as indium tin oxide (ITO), aluminum zinc oxide (AZO), fluorine-doped tin dioxide (FTO), indium tin zinc oxide (ITZO), zinc tin oxide (ZTO), zinc indium tin oxide (ZITO), etc.) and p-type conductive oxides (such as copper oxide (CuO), CuM'O (M'=Al, In, Ga, Mg), etc.); non-conductive metal oxides can be magnesium oxide (MgO), aluminum oxide (Al2O3), zinc oxide (ZnO), silicon oxide (SiO x ), tin oxide (SnO), manganese oxide, zirconium oxide ZrO, etc.

[0140] According to a specific embodiment of the present invention, the metal compound layer may include M x+ S 2- x / 2 (i.e., a compound of sulfur and M), during battery charging, M x+ S 2- x / 2 Reacts with lithium atoms from the positive electrode during battery charging to generate M and lithium sulfide (Li2S). M can alloy with metallic lithium to form Li-M alloy. The reactions involved are as follows: M x+ S 2- x / 2 +x Li=M+x / 2Li2S, M+Li=Li-M.

[0141] According to a specific embodiment of the present invention, the metal compound layer may include M x+ N 3- x / 3 (i.e., a compound of nitrogen and M), during battery charging, M x+ N 3- x / 3 Reacts with lithium atoms from the positive electrode during battery charging to form M and lithium nitride (Li3N). M can alloy with metallic lithium to form Li-M alloy. The reactions involved are as follows: M x+ N 3- x / 3 +x Li=M+x / 3Li3N, M+Li=Li-M.

[0142] According to a specific embodiment of the present invention, the metal compound layer may include M x+ P 3- x / 3 (i.e., a compound of phosphorus and M). During the battery charging process, M x+ P 3- x / 3 Reacts with lithium atoms from the positive electrode during battery charging to form M and lithium phosphide (Li3P). M can alloy with metallic lithium to form Li-M alloy. The reactions involved are as follows: M x+ P 3- x / 3 +x Li=M+x / 3Li3P, M+Li=Li-M.

[0143] Therefore, the lithium metal battery obtained by the method for preparing a lithium metal battery of the present invention has high cycle stability and effectively avoids the process complexity caused by multi-layer deposition.

[0144] In its fifth aspect, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device comprises the aforementioned lithium metal battery or a lithium metal battery obtained by the aforementioned method for preparing a lithium metal battery. The electrical device and the aforementioned lithium metal battery or method for preparing a lithium metal battery have the same advantages over the prior art and are not further elaborated here.

[0145] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0146] Example 1

[0147] A negative electrode sheet, referring to FIG8 , includes a current collector 10 , a first active material layer 20 , a second active material layer 30 , a first artificial SEI layer 40 , a fifth active material layer 90 , a sixth active material layer 100 and a fourth artificial SEI layer 110 .

[0148] The current collector 10 includes a first side and a second side relative to each other. The current collector 10 includes a base film 11, a first conductive layer 12 and a second conductive layer 13. The first conductive layer 12 is arranged on the surface of one side of the base film 11, and the second conductive layer 13 is arranged on the surface of the other side opposite to the base film 11. The base film 11 is made of polypropylene with a thickness of 1 μm, the first conductive layer 12 is made of copper with a thickness of 0.3 μm, and the second conductive layer 13 is made of copper with a thickness of 0.3 μm.

[0149] The first active material layer 20, the second active material layer 30, and the first artificial SEI layer 40 are sequentially arranged on the first side of the current collector 10 along a direction away from the current collector 10. The first active material layer 20 includes metallic lithium, the second active material layer 30 includes an alloy formed by metallic lithium and magnesium, and the lithium content is 2 atm%. The first artificial SEI layer 40 includes lithium fluoride; the fifth active material layer 90, the sixth active material layer 100, and the fourth artificial SEI layer 110 are sequentially arranged on the second side of the current collector 10 along a direction away from the current collector 10. The fifth active material layer 90 includes metallic lithium, the sixth active material layer 100 includes an alloy formed by metallic lithium and magnesium, and the lithium content is 2 atm%. The fourth artificial SEI layer 110 includes lithium fluoride. The thickness of the first active material layer 20, the second active material layer 30, the fifth active material layer 90, and the sixth active material layer 100 are all 100 μm, and the thickness of the first artificial SEI layer 40 and the fourth artificial SEI layer 110 are both 1 μm.

[0150] The negative electrode sheet of Example 1 is used to assemble a liquid battery:

[0151] 1. Preparation of positive electrode sheet

[0152] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are prepared into positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2, Super P and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil and dried at 85°C and then cold pressed. Then, it is trimmed, cut and striped, and dried under vacuum conditions at 85°C for 4 hours to make the positive electrode sheet.

[0153] 2. Preparation of electrolyte

[0154] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), the fully dried electrolyte salt LiTFSI was dissolved in a mixed solvent (the mixed solvent included 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME), and 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) were mixed in a volume ratio of 50:50), and after mixing evenly, an electrolyte solution with a concentration of 1 mol / L was obtained.

[0155] 3. Isolation film

[0156] A 16 μm polyethylene film was used as the separator.

[0157] 4. Preparation of lithium metal batteries

[0158] The positive electrode sheet, the isolation film, and the negative electrode sheet of Example 1 are stacked in order, so that the isolation film is placed between the positive and negative electrode sheets to isolate the positive and negative electrodes. The bare battery cell is wound and the tabs are welded. The bare battery cell is placed in an outer package, and the electrolyte prepared above is injected into the dried battery cell. The battery cell is packaged, allowed to stand, formed, shaped, and capacity tested to complete the preparation of the lithium metal battery.

[0159] The cycle performance of the lithium metal battery obtained from the negative electrode sheet of Example 1 was characterized.

[0160] Cycling performance test method for lithium metal batteries

[0161] The battery was charged at a constant current of 0.2C at 25°C±2°C until the battery voltage reached 4.2V. The battery was then switched to constant voltage charging until the charging current dropped to 0.05C and charging was stopped. The battery was allowed to stand for 30 minutes after charging and discharged at a current of 0.3C until the battery voltage reached 2.6V. After 50 cycles of the above charge and discharge process, the battery was disassembled and the negative electrode of Example 1 was tested by scanning electron microscope (SEM).

[0162] From the obtained SEM image, it can be seen that the surface of the negative electrode sheet of Example 1 is uniform and relatively flat, and no obvious growth of lithium dendrites is observed.

[0163] It can be seen from Example 1 that the use of the negative electrode plate of the present invention can improve the interface problems of metallic lithium in secondary battery applications, avoid problems such as continuous thickening of the SEI film, continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the diaphragm, thereby helping to improve the cycle stability of the lithium metal battery using the negative electrode plate.

[0164] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0165] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A negative electrode plate, characterized in that: include: a current collector comprising opposing first and second sides; A first active material layer, a second active material layer and a first artificial SEI layer, wherein the first active material layer, the second active material layer and the first artificial SEI layer are sequentially arranged on a first side of the current collector in a direction away from the current collector, the first active material layer comprises metallic lithium, the second active material layer comprises a metallic lithium alloy, and the first artificial SEI layer comprises a lithium compound.

2. The negative electrode sheet according to claim 1, characterized in that: The current collector is a composite current collector.

3. The negative electrode sheet according to claim 1, characterized in that: The current collector is a metal foil current collector, and the metal foil current collector includes at least one of copper, aluminum, zinc, nickel and chromium.

4. The negative electrode sheet according to claim 3, characterized in that: The thickness of the current collector is 1 μm-10 μm.

5. The negative electrode sheet according to claim 2, characterized in that: The current collector includes a base film, a first conductive layer disposed on one side of the base film, and a second conductive layer disposed on the other side opposite to the base film.

6. The negative electrode sheet according to claim 5, characterized in that: The first conductive layer and the second conductive layer each independently include at least one of copper, aluminum, zinc, nickel and chromium.

7. The negative electrode sheet according to claim 5 or 6, characterized in that: The thickness of the first conductive layer and the second conductive layer are independently 0.3 μm-10 μm.

8. The negative electrode sheet according to claim 5, characterized in that: The base film includes at least one of polyethylene, polyethylene terephthalate, polyimide, polypropylene, polyamide, polyphenylene sulfide, and polyethylene naphthalate.

9. The negative electrode sheet according to claim 5 or 8, characterized in that: The base film has a thickness of 1 μm-10 μm.

10. The negative electrode sheet according to claim 5, characterized in that: The device further includes a third active material layer, which is disposed on the second side of the current collector and includes a metal lithium alloy.

11. The negative electrode sheet according to claim 10, characterized in that: The first active material layer is disposed on the first conductive layer, and the third active material layer is disposed on the second conductive layer.

12. The negative electrode sheet according to claim 10, characterized in that: The method further comprises a second artificial SEI layer, wherein the second artificial SEI layer is arranged on a side of the third active material layer away from the current collector, and the second artificial SEI layer comprises a lithium compound.

13. The negative electrode sheet according to claim 5, characterized in that: It also includes a fourth active material layer and a third artificial SEI layer, which are arranged in sequence on the second side of the current collector in a direction away from the current collector, the fourth active material layer includes metallic lithium, and the third artificial SEI layer includes a lithium compound and a metallic lithium alloy.

14. The negative electrode sheet according to claim 13, characterized in that: The first active material layer is disposed on the first conductive layer, and the fourth active material layer is disposed on the second conductive layer.

15. The negative electrode sheet according to claim 5, characterized in that: It also includes a fifth active material layer and a sixth active material layer, which are sequentially arranged on the second side of the current collector in a direction away from the current collector, the fifth active material layer includes metallic lithium, and the sixth active material layer includes a metallic lithium alloy.

16. The negative electrode sheet according to claim 15, characterized in that: The first active material layer is disposed on the first conductive layer, and the fifth active material layer is disposed on the second conductive layer.

17. The negative electrode sheet according to claim 15, characterized in that: The method further comprises a fourth artificial SEI layer, wherein the fourth artificial SEI layer is arranged on a side of the sixth active material layer away from the current collector, and the fourth artificial SEI layer comprises a lithium compound.

18. The negative electrode sheet according to claim 1 or 10 or 13 or 15, characterized in that: The metal lithium alloy includes an alloy formed by metal lithium and at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

19. The negative electrode sheet according to claim 18, characterized in that: The content of lithium element in the metal lithium alloy is 0.1 atm%-99.9 atm%.

20. The negative electrode sheet according to claim 10 or 12, characterized in that: The thickness of the first active material layer, the second active material layer and the third active material layer are independently 0.1 μm to 100 μm.

21. The negative electrode sheet according to claim 13, characterized in that: The thickness of the fourth active material layer is 0.1 μm-100 μm.

22. The negative electrode sheet according to claim 15 or 17, characterized in that: The thickness of the fifth active material layer and the sixth active material layer are independently 0.1 μm to 100 μm.

23. The negative electrode plate according to claim 1 or 12 or 13 or 17, characterized in that: The lithium compound includes a compound of lithium and at least one of halogen, oxygen, nitrogen, sulfur and phosphorus.

24. The negative electrode sheet according to claim 13, characterized in that: The metal lithium alloy in the third artificial SEI layer includes Li-M, wherein M includes at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, silver, tin and bismuth, and the molar ratio of the lithium compound in the third artificial SEI layer to the Li-M is (0.1-10):

1.

25. The negative electrode plate according to claim 12, characterized in that: The thickness of the first artificial SEI layer and the second artificial SEI layer are independently 0.1 μm-1 μm.

26. The negative electrode plate according to claim 13, characterized in that: The thickness of the third artificial SEI layer is 0.1 μm-1 μm.

27. The negative electrode plate according to claim 17, characterized in that: The thickness of the fourth artificial SEI layer is 0.1 μm-1 μm.

28. A method for preparing a negative electrode sheet, characterized in that: include: providing a current collector comprising opposing first and second sides; forming a first active material layer on a first side of the current collector, wherein the first active material layer includes metallic lithium; forming a second active material layer on a side of the first active material layer away from the current collector, wherein the second active material layer comprises a metal lithium alloy; A first artificial SEI layer is formed on a side of the second active material layer away from the first active material layer, wherein the first artificial SEI layer includes a lithium compound.

29. The method according to claim 28, characterized in that Also includes: forming a fourth active material layer on the second side of the current collector, wherein the fourth active material layer includes metallic lithium; A third artificial SEI layer is formed on a side of the fourth active material layer away from the current collector, wherein the third artificial SEI layer includes a lithium compound and a metal lithium alloy.

30. The method according to claim 28, characterized in that Also includes: forming a fifth active material layer on the second side of the current collector, wherein the fifth active material layer includes metallic lithium; forming a sixth active material layer on a side of the fifth active material layer away from the current collector, wherein the sixth active material layer comprises a metal lithium alloy; A fourth artificial SEI layer is formed on a side of the sixth active material layer away from the fifth active material layer, wherein the fourth artificial SEI layer includes a lithium compound.

31. A lithium metal battery, characterized in that: A negative electrode sheet comprising the negative electrode sheet described in any one of claims 1 to 27 or a negative electrode sheet obtained by the method described in any one of claims 28 to 30.

32. The lithium metal battery according to claim 31, characterized in that The lithium metal batteries include liquid batteries, semi-solid batteries and all-solid batteries.

33. The lithium metal battery according to claim 32, characterized in that The lithium metal battery includes a liquid battery and a semi-solid battery, and the liquid battery and the semi-solid battery include an electrolyte, and the electrolyte includes a lithium salt and a solvent.

34. The lithium metal battery according to claim 33, characterized in that The lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonyl-perfluorobutylsulfonylimide, lithium fluorosulfonyl-perfluorobutylsulfonylimide, lithium bis(oxalatoborate) and tris(trifluoromethylsulfonyl)methyllithium.

35. The lithium metal battery according to claim 33 or 34, characterized in that: The solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, tetrahydrofuran, 2-methyl-tetrahydrofuran, dimethoxydimethyl ether, 1,2-dimethoxyethane, 1,3-dioxolane and acetonitrile.

36. The lithium metal battery according to claim 35, characterized in that The electrolyte further includes an additive, and the additive includes at least one of a film-forming additive, a conductive additive, a flame retardant additive, an overcharge protection additive, an additive for controlling water and HF content, a low-temperature additive, and a negative electrode stabilizer.

37. The lithium metal battery according to claim 31, characterized in that The lithium metal battery includes a semi-solid battery and an all-solid battery, and the semi-solid battery and the all-solid battery include an electrolyte, and the electrolyte includes at least one of an inorganic solid electrolyte, a polymer solid electrolyte and a composite solid electrolyte, and the inorganic solid electrolyte includes at least one of an oxide solid electrolyte, a sulfide solid electrolyte and a halide solid electrolyte.

38. A method for preparing a lithium metal battery, characterized in that: include: Providing a negative electrode plate, the negative electrode plate comprising a current collector having a first side and a second side opposite to each other, the first side of the current collector being provided with a first active material layer, a second active material layer and a first artificial SEI layer in sequence along a direction away from the current collector, the first active material layer comprising metallic lithium, the second active material layer comprising a metallic lithium alloy, the first artificial SEI layer comprising a lithium compound, and the second side of the current collector being provided with a fourth active material layer and a metal compound layer in sequence along a direction away from the current collector, the fourth active material layer comprising metallic lithium; The negative electrode plates are assembled into a battery and charged so that the metal compound layer forms a third artificial SEI layer in situ during the battery charging process, wherein the third artificial SEI layer includes a lithium compound and a metal lithium alloy. The metal compound layer includes a compound of at least one of halogen, oxygen, nitrogen, sulfur and phosphorus and M, and M includes at least one of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, silver, tin and bismuth.

39. An electrical device, characterized in that: A lithium metal battery comprising the lithium metal battery described in any one of claims 31-37 or a lithium metal battery obtained by the method of claim 38.

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