Negative pole piece as well as preparation method and application thereof

Abstract

The invention discloses a negative pole piece as well as a preparation method and application thereof. The negative pole piece comprises a current collector, wherein the current collector comprises a first side and a second side which are opposite to each other; a first active material layer, a second active material layer and a first artificial SEI layer, 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 the direction away from the current collector, the first active material layer comprises metal lithium, and the second 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. By adopting the negative pole piece, the problems of continuous thickening of an SEI film, continuous growth of lithium dendrites, lithium death, diaphragm piercing by the lithium dendrites and the like can be avoided, so that the cycle stability of the lithium metal battery applying the negative pole piece is favorably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a negative electrode sheet, a preparation method thereof, and an application thereof. Background Art

[0002] Compared with the theoretical specific capacity of 372 mAh / g of the graphite negative electrode, metallic lithium has an ultra-high theoretical specific capacity of 3860 mAh / g and the most negative standard reduction potential (-3.04 V), and also has the characteristics of low density and small ionic radius. Using metallic lithium as the negative electrode active material of the battery can further improve the energy density of the battery.

[0003] Since lithium ions have a high diffusion barrier and will react with the electrolyte / electrolyte, consuming the metallic lithium negative electrode and the electrolyte, resulting in capacity loss; in addition, different from the commercial graphite negative electrode, the storage mechanism of lithium ions in the metallic lithium negative electrode is not an intercalation type, but itself also serves as a lithium source, so it causes a huge volume expansion of the metallic lithium negative electrode. Whether the metallic lithium negative electrode is applied in a solid state system or a liquid state system, it faces technical problems such as the thickening of the SEI film, the growth of lithium dendrites, dead lithium, and the piercing of the separator by lithium dendrites caused by the high chemical reactivity of metallic lithium and the infinite volume change rate. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the present invention is to provide a negative electrode sheet, a preparation method thereof, and an application thereof. Using this negative electrode sheet can avoid problems such as the continuous thickening of the SEI film, the continuous growth of lithium dendrites, dead lithium, and the piercing of the separator by lithium dendrites, thereby being beneficial to improving the cycle stability of the lithium metal battery using this negative electrode sheet.

[0005] In the first aspect of the present invention, the present invention provides a negative electrode sheet. According to an embodiment of the present invention, the negative electrode sheet includes:

[0006] A current collector, the current collector including opposite first and second sides;

[0007] A first active material layer, a second active material layer, and a first artificial SEI layer, 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 along the direction away from the current collector. The first active material layer includes metallic lithium, the second active material layer includes a lithium alloy, and the first artificial SEI layer includes a lithium compound.

[0008] According to the negative electrode sheet of the above embodiment of the present invention, by sequentially arranging a first active material layer, a second active material layer, and a first artificial SEI layer 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 serve 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 prevent the highly reactive metallic lithium in the first active material layer from directly contacting the electrolyte or the electrolyte. On the other hand, during the charge and discharge process of the battery, an alloying reaction occurs between the metallic lithium and the metallic lithium alloy in the second active material layer, which is beneficial to the uniform deposition of metallic lithium, thereby effectively avoiding problems such as the growth of lithium dendrites caused by uneven deposition of metallic lithium and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate. The first artificial SEI layer includes lithium compounds. On the one hand, it can further prevent the highly reactive metallic lithium in the first active material layer from directly contacting the electrolyte or the electrolyte. On the other hand, it can promote the rapid migration of lithium ions, thereby effectively avoiding problems such as the growth of lithium dendrites caused by the untimely insertion and extraction of lithium ions at the negative electrode and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate. Thus, by using the negative electrode sheet of the present invention, the interface problem of metallic lithium in the application of secondary batteries can be improved, and problems such as the continuous thickening of the SEI film, the continuous growth of lithium dendrites, dead lithium, and the piercing of the separator by lithium dendrites can be avoided, which is beneficial to improving the cycle stability of the lithium metal battery using this negative electrode sheet.

[0009] In addition, the negative electrode sheet according to the above embodiment of the present invention may further have the following additional technical features:

[0010] In some embodiments of the present invention, the current collector is a composite current collector.

[0011] 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.

[0012] In some embodiments of the present invention, the thickness of the current collector is 1 μm - 10 μm.

[0013] 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.

[0014] 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. Thus, the conductivity of the current collector can be improved.

[0015] In some embodiments of the present invention, the thicknesses of the first conductive layer and the second conductive layer are each independently 0.3 μm - 10 μm.

[0016] 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.

[0017] In some embodiments of the present invention, the thickness of the base film is 1 μm - 10 μm.

[0018] In some embodiments of the present invention, the above-mentioned negative electrode sheet further includes a third active material layer, the third active material layer is disposed on the second side of the current collector, and the third active material layer includes a lithium metal alloy.

[0019] 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.

[0020] In some embodiments of the present invention, the above-mentioned negative electrode sheet further includes a second artificial SEI layer, the second artificial SEI layer is disposed on the side of the third active material layer away from the current collector, and the second artificial SEI layer includes a lithium compound.

[0021] In some embodiments of the present invention, the above-mentioned negative electrode sheet further includes a fourth active material layer and a third artificial SEI layer, the fourth active material layer and the third artificial SEI layer are sequentially disposed on the second side of the current collector along the direction away from the current collector, the fourth active material layer includes lithium metal, and the third artificial SEI layer includes a lithium compound and a lithium metal alloy.

[0022] 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.

[0023] In some embodiments of the present invention, the above-mentioned negative electrode sheet further includes a fifth active material layer and a sixth active material layer, the fifth active material layer and the sixth active material layer are sequentially disposed on the second side of the current collector along the direction away from the current collector, the fifth active material layer includes lithium metal, and the sixth active material layer includes a lithium metal alloy.

[0024] 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.

[0025] In some embodiments of the present invention, the above-mentioned negative electrode sheet further includes a fourth artificial SEI layer, the fourth artificial SEI layer is disposed on the side of the sixth active material layer away from the current collector, and the fourth artificial SEI layer includes a lithium compound.

[0026] In some embodiments of the present invention, the metallic lithium alloy includes an alloy formed by metallic 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. Thus, problems such as lithium dendrite growth, continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator caused by uneven deposition of metallic lithium on the negative electrode surface during the cycling of the lithium metal battery can be solved.

[0027] In some embodiments of the present invention, the content of lithium element in the metallic lithium alloy is 0.1 atm% - 99.9 atm%. Thus, problems such as lithium dendrite growth, continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator caused by uneven deposition of metallic lithium on the negative electrode surface during the cycling of the lithium metal battery can be solved.

[0028] In some embodiments of the present invention, the thicknesses of the first active material layer, the second active material layer, and the third active material layer are each independently 0.1 μm - 100 μm.

[0029] In some embodiments of the present invention, the thickness of the fourth active material layer is 0.1 μm - 100 μm.

[0030] In some embodiments of the present invention, the thicknesses of the fifth active material layer and the sixth active material layer are each independently 0.1 μm - 100 μm.

[0031] In some embodiments of the present invention, the lithium compound includes a compound of at least one of halogen, oxygen element, nitrogen element, sulfur element, and phosphorus element and lithium element. Thus, problems such as lithium dendrite growth caused by untimely deintercalation of lithium ions from the negative electrode and continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator brought about by an infinitely large volume change rate can be effectively avoided.

[0032] In some embodiments of the present invention, the metallic lithium alloy in the third artificial SEI layer includes Li-M, where 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 Li-M is (0.1 - 10):1.

[0033] In some embodiments of the present invention, the thicknesses of the first artificial SEI layer and the second artificial SEI layer are each independently 0.1 μm - 1 μm.

[0034] In some embodiments of the present invention, the thickness of the third artificial SEI layer is 0.1 μm - 1 μm.

[0035] In some embodiments of the present invention, the thickness of the fourth artificial SEI layer is 0.1 μm - 1 μm.

[0036] In a second aspect of the present invention, the present invention provides a method for preparing a negative electrode plate. According to an embodiment of the present invention, the method includes:

[0037] Providing a current collector, the current collector including opposite first and second sides;

[0038] Forming a first active material layer on the first side of the current collector, the first active material layer including metallic lithium;

[0039] Forming a second active material layer on a side of the first active material layer away from the current collector, the second active material layer including a metallic lithium alloy;

[0040] Forming a first artificial SEI layer on a side of the second active material layer away from the first active material layer, the first artificial SEI layer including a lithium compound.

[0041] According to the method for preparing a negative electrode plate of the above embodiment of the present invention, by providing a current collector including opposite first and second sides, forming a first active material layer on the first side of the current collector, forming a second active material layer on a side of the first active material layer away from the current collector, and forming a first artificial SEI layer on a side of the second active material layer away from the first active material layer, the first active material layer including metallic lithium can serve 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 prevent the highly reactive metallic lithium in the first active material layer from directly contacting the electrolyte or the electrolyte. On the other hand, it can enable an alloying reaction between the metallic lithium and the metallic lithium alloy in the second active material layer during the charge and discharge process of the battery, which is beneficial to the uniform deposition of metallic lithium, thereby effectively avoiding problems such as the growth of lithium dendrites caused by uneven deposition of metallic lithium and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate. The first artificial SEI layer includes a lithium compound. On the one hand, it can further prevent the highly reactive metallic lithium in the first active material layer from directly contacting the electrolyte or the electrolyte. On the other hand, it can promote the rapid migration of lithium ions, thereby effectively avoiding problems such as the growth of lithium dendrites caused by untimely deintercalation and insertion of lithium ions at the negative electrode and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate. Thus, the negative electrode plate obtained by using the method for preparing a negative electrode plate of the present invention can improve the interfacial problems of metallic lithium in the application of secondary batteries, avoid problems such as the continuous thickening of the SEI film, the continuous growth of lithium dendrites, dead lithium, and the piercing of the separator by lithium dendrites, thereby being beneficial to improving the cycle stability of the lithium metal battery using the negative electrode plate.

[0042] In addition, the method for preparing a negative electrode plate according to the above embodiment of the present invention may further have the following additional technical features:

[0043] In some embodiments of the present invention, the above method further includes: forming a fourth active material layer on the second side of the current collector, the fourth active material layer including metallic lithium; forming a third artificial SEI layer on a side of the fourth active material layer away from the current collector, the third artificial SEI layer including lithium compounds and metallic lithium alloy. Thereby, the cycle stability of the lithium metal battery can be improved.

[0044] In some embodiments of the present invention, the above method further includes: forming a fifth active material layer on the second side of the current collector, the fifth active material layer including 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 including metallic lithium alloy; 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 including lithium compounds. Thereby, the cycle stability of the lithium metal battery can be improved.

[0045] In a third aspect of the present invention, the present invention provides a lithium metal battery. According to an embodiment of the present invention, the lithium metal battery includes the above negative electrode sheet or a negative electrode sheet obtained by using the method for preparing the negative electrode sheet as described above. Thereby, the lithium metal battery has high cycle stability.

[0046] In addition, the lithium metal battery according to the above embodiments of the present invention may further have the following additional technical features:

[0047] In some embodiments of the present invention, the lithium metal battery includes a liquid battery, a semi-solid battery, and a solid-state battery.

[0048] In some embodiments of the present invention, the lithium metal battery includes a liquid battery and a semi-solid battery, the liquid battery and the semi-solid battery include an electrolyte, and the electrolyte includes a lithium salt and a solvent.

[0049] 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 trifluoromethylsulfonyl-n-perfluorobutanesulfonylimide, lithium fluorosulfonyl-n-perfluorobutanesulfonylimide, lithium bis(oxalato)borate, and lithium tris(trifluoromethylsulfonyl)methyl.

[0050] 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.

[0051] In some embodiments of the present invention, 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 the content of water and HF, a low-temperature additive, and a negative electrode stabilizer.

[0052] In some embodiments of the present invention, the lithium metal battery includes a semi-solid battery and a solid-state battery. The semi-solid battery and the 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. The inorganic solid electrolyte includes at least one of an oxide solid electrolyte, a sulfide solid electrolyte, and a halide solid electrolyte.

[0053] 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 opposite first and second sides, a first active material layer, a second active material layer, and a first artificial SEI layer are sequentially disposed 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 lithium compound. A fourth active material layer and a metal compound layer are sequentially disposed on the second side of the current collector in a direction away from the current collector. The fourth active material layer includes metallic lithium; assembling the negative electrode plate into a battery and charging it so that the metal compound layer forms a third artificial SEI layer in-situ during the charging process of the battery. The third artificial SEI layer includes a lithium compound and a metallic lithium alloy, wherein the metal compound layer includes a compound of at least one of halogen, oxygen element, nitrogen element, sulfur element, and phosphorus element 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. Thus, the lithium metal battery obtained by this method has high cycle stability and effectively avoids the process complexity caused by multi-layer deposition.

[0054] In a fifth aspect of the present invention, an electrical device is provided. According to an embodiment of the present invention, the electrical device includes the above-mentioned lithium metal battery or the lithium metal battery obtained by the above-mentioned method for preparing a lithium metal battery. The advantages of the electrical device relative to the prior art are the same as those of the above-mentioned lithium metal battery or the above-mentioned method for preparing a lithium metal battery, and will not be elaborated herein.

[0055] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0057] Figure 1 is a schematic structural view of a negative electrode plate according to an embodiment of the present invention;

[0058] Figure 2 is a schematic structural view of a current collector according to an embodiment of the present invention;

[0059] Figure 3 is a schematic structural view of a negative electrode plate according to another embodiment of the present invention;

[0060] Figure 4 is a schematic structural view of a negative electrode plate according to yet another embodiment of the present invention;

[0061] Figure 5 is a schematic structural view of a negative electrode plate according to yet another embodiment of the present invention;

[0062] Figure 6 is a schematic structural view of a negative electrode plate according to yet another embodiment of the present invention;

[0063] Figure 7 is a schematic structural view of a negative electrode plate according to yet another embodiment of the present invention;

[0064] Figure 8 is a schematic structural view of a negative electrode plate according to yet another embodiment of the present invention;

[0065] Figure 9 is a schematic flow chart of a method for preparing a negative electrode plate according to an embodiment of the present invention.

[0066] Reference numerals:

[0067] 1000 - negative electrode plate; 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 of the Embodiments

[0068] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0069] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is 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 thus should not be construed as a limitation to the present invention.

[0070] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0071] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0073] In the first aspect of the present invention, the present invention provides a negative electrode plate. According to an embodiment of the present invention, with reference to Figure 1 , the negative electrode plate 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 interface) layer 40.

[0074] According to an embodiment of the present invention, the current collector 10 includes opposite first and second sides. It should be noted that the specific type and thickness of the current collector 10 are not particularly limited, and those skilled in the art can select according to 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 - 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. Among them, the thickness of the metal foil current collector is preferably 4 μm - 10 μm.

[0075] According to a specific embodiment of the present invention, the current collector 10 is a metal foil current collector, and the metal foil current collector can include at least one of copper, aluminum, zinc, nickel, and chromium. Optionally, the metal foil current collector includes at least one of copper, nickel, copper-nickel alloy, and copper-zinc alloy.

[0076] According to a specific embodiment of the present invention, referring to Figure 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.

[0077] According to a specific embodiment of the present invention, the material of the base film 11 is a polymer. The material of the base film 11 is a polymer, which has a lower density than metal foils such as copper foils. Therefore, the current collector 10 prepared therefrom also has a lower density than metal foil current collectors such as copper foils, thereby improving the energy density of the battery.

[0078] It should be noted that the specific type of the above base film 11 is not particularly limited, and those skilled in the art can select 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, and PI and PPS have a flame retardant effect, thereby reducing the fire problem caused by the short circuit of lithium dendrites piercing the thin film.

[0079] According to a specific embodiment of the present invention, the thickness of the above base film 11 can be 1 μm - 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.

[0080] According to a specific embodiment of the present invention, referring to Figure 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.

[0081] It should be noted that the material and thickness of the first conductive layer 12 are not particularly limited, and those skilled in the art can select according to actual needs, as long as it has excellent electrical conductivity and mechanical properties. For example, the material of the first conductive layer 12 can include at least one of copper, aluminum, zinc, nickel, and chromium, and the thickness of the first conductive layer 12 can be 0.3 μm - 10 μm, such as 0.3 μm, 0.5 μm, 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 Figure 2 , the second conductive layer 13 is disposed on the opposite side of the base film 11. By disposing the second conductive layer 13 on the opposite side of the base film 11, the electrical conductivity of the current collector 10 can be further improved.

[0083] It should be noted that the material and thickness of the second conductive layer 13 are not particularly limited, and those skilled in the art can select according to actual needs, as long as it has excellent electrical conductivity and mechanical properties. For example, the material of the second conductive layer 13 can include at least one of copper, aluminum, zinc, nickel, and chromium, and the thickness of the second conductive layer 13 can be 0.3 μm - 10 μm, such as 0.3 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0084] 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 electroplating. For example, when using copper 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. Among them, the one-step method includes a one-step chemical deposition method, a one-step vacuum magnetron sputtering method, and a one-step vacuum evaporation method. The one-step chemical deposition method deposits a copper layer through a chemical reaction, the one-step vacuum magnetron sputtering method deposits a copper layer through repeated magnetron sputtering, and the one-step vacuum evaporation method deposits a copper layer through repeated evaporation; the two-step method first uses magnetron sputtering for underlaying and then uses electroplating to thicken the copper layer; the three-step method first uses magnetron sputtering for underlaying, then uses vacuum evaporation, and finally uses electroplating to thicken the copper layer.

[0085] Thus, by using the composite current collector as the current collector 10 in the negative electrode sheet 1000 of the present invention, on the one hand, the mechanical strength and mechanical properties of the negative electrode sheet 1000 can be improved. On the other hand, compared with a current collector made of a metal foil 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 a current collector made of a metal foil such as copper foil (weight reduction of more than 60%), which can improve the energy density of the battery.

[0086] According to an embodiment of the present invention, with reference to Figure 1 , the first active material layer 20, the second active material layer 30, and the first artificial SEI layer 40 are sequentially disposed 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, 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 found that by sequentially disposing 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, and the first active material layer 20 includes metallic lithium, it can serve 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, it can prevent the highly reactive metallic lithium in the first active material layer 20 from directly contacting the electrolyte or the solid electrolyte. On the other hand, during the charge and discharge process of the battery, alloying reaction occurs between the metallic lithium and the metallic lithium alloy in the second active material layer 30, which is beneficial to the uniform deposition of metallic lithium, thereby effectively avoiding problems such as lithium dendrite growth caused by non-uniform deposition of metallic lithium and continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator due to an infinitely large volume change rate. The first artificial SEI layer 40 includes a lithium compound. 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 the solid electrolyte. On the other hand, it can promote the rapid migration of lithium ions, effectively avoiding problems such as lithium dendrite growth caused by untimely insertion and extraction of lithium ions at the negative electrode and continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator due to an infinitely large volume change rate, thereby being beneficial to improving the cycle stability of the lithium metal battery using the negative electrode sheet 1000.

[0087] According to a specific embodiment of the present invention, with reference to Figure 3 , the first active material layer 20 may be disposed on the first conductive layer 12.

[0088] 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 those skilled in the art can select according to actual needs. As a preferred solution, the thicknesses of the first active material layer 20 and the second active material layer 30 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., and the thickness of the first artificial SEI layer 40 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.

[0089] According to specific embodiments of the present invention, the specific composition of the lithium metal alloy is not particularly limited, and those skilled in the art can select according to actual needs. For example, it may include an alloy formed by lithium metal 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 lithium metal alloy can be 0.1 atm% - 99.9 atm%, for example, it can be 0.1 atm%, 1 atm%, 2 atm%, 5 atm%, 15 atm%, 25 atm%, 35 atm%, 45 atm%, 55 atm%, 65 atm%, 75 atm%, 85 atm%, 95 atm%, 99.9 atm%, etc. Thus, problems such as lithium dendrite growth, continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator caused by uneven deposition of lithium metal on the negative electrode surface during the cycling of the lithium metal battery can be solved.

[0090] According to specific embodiments of the present invention, the specific type of the lithium compound is not particularly limited, and those skilled in the art can select according to actual needs. For example, it may include a compound of at least one of halogen (such as fluorine element), oxygen element, nitrogen element, sulfur element, and phosphorus element and lithium element. Optionally, the lithium compound may include at least one of lithium fluoride (LiF), lithium oxide (Li 2 O), lithium sulfide (Li 2 S), lithium nitride (Li 3 N), lithium phosphide (Li 3 P), and lithium phosphorus oxynitride compound (LiPON).

[0091] According to specific embodiments of the present invention, referring to Figure 4 , the negative electrode sheet 1000 further includes a third active material layer 50. The third active material layer 50 is disposed on the second side of the current collector 10, and the third active material layer 50 includes a lithium metal alloy. By disposing the third active material layer 50 including the lithium metal alloy on the second side of the current collector 10, an alloying reaction can occur between lithium metal and the lithium metal alloy in the third active material layer 50 during the charge and discharge process of the battery, which is further beneficial to the uniform deposition of lithium metal, avoiding problems such as lithium dendrite growth caused by uneven deposition of lithium metal, and continuous thickening of the SEI film, dead lithium, and lithium dendrite piercing the separator brought about by an infinitely large volume change rate. Thus, it is further beneficial to improve the cycling stability of the lithium metal battery applying the negative electrode sheet 1000. Specifically, the third active material layer 50 can be disposed on the second conductive layer 13.

[0092] It should be noted that the thickness of the third active material layer 50 is not particularly limited, and those skilled in the art can select it according to actual needs. As a preferred solution, the thickness of the third active material layer 50 can be 0.1 μm - 100 μm, for example, it can be 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.

[0093] According to a specific embodiment of the present invention, referring to Figure 5 , the above-mentioned negative electrode sheet 1000 further includes a second artificial SEI layer 60, and the second artificial SEI layer 60 is disposed on the side of the third active material layer 50 away from the current collector 10. The second artificial SEI layer 60 includes a lithium compound. By disposing the second artificial SEI layer 60 including a lithium compound on the side of the third active material layer 50 away from the current collector 10, it can further facilitate the rapid migration of lithium ions, thereby effectively avoiding problems such as the growth of lithium dendrites caused by the untimely insertion and extraction of lithium ions from the negative electrode, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thereby further facilitating the improvement of the cycle stability of the lithium metal battery using the negative electrode sheet 1000.

[0094] It should be noted that the thickness of the second artificial SEI layer 60 is not particularly limited, and those skilled in the art can select it according to actual needs. As a preferred solution, the thickness of the second artificial SEI layer 60 can be 0.1 μm - 1 μm, for example, it can be 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.

[0095] According to a specific embodiment of the present invention, referring to Figure 6, the above-mentioned 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 along the direction away from the current collector 10. The fourth active material layer 70 includes metallic lithium, and the third artificial SEI layer 80 includes lithium compounds and metallic lithium alloys. 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 along the direction away from the current collector 10, and the fourth active material layer 70 includes metallic lithium, it can serve as a supplementary lithium source to improve the cycle life of the battery. The third artificial SEI layer 80 includes lithium compounds and metallic lithium alloys. 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 compounds in the third artificial SEI layer 80 can further facilitate the rapid migration of lithium ions, thereby effectively avoiding problems such as the growth of lithium dendrites caused by the untimely insertion and extraction of lithium ions at the negative electrode, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate. On the other hand, the metallic lithium alloy in the third artificial SEI layer 80 can undergo an alloying reaction with metallic lithium during the charge and discharge process of the battery, further facilitating the uniform deposition of metallic lithium, effectively avoiding problems such as the growth of lithium dendrites caused by the non-uniform deposition of metallic lithium, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thereby further facilitating the improvement of the cycle stability of the lithium metal battery using the negative electrode sheet 1000. Specifically, the fourth active material layer 70 can be arranged on the second conductive layer 13.

[0096] According to a specific embodiment of the present invention, in the third artificial SEI layer 80, the lithium compound can include a compound of at least one of halogen, oxygen element, nitrogen element, sulfur element, and phosphorus element and lithium element, and the metallic lithium alloy can include Li-M, where 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. The molar ratio of the lithium compound to Li-M in the third artificial SEI layer 80 can be (0.1 - 10):1, for example, it can be 0.1:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 8:1, 10:1, etc.

[0097] It should be noted that the thicknesses of the fourth active material layer 70 and the third artificial SEI layer 80 are not particularly limited, and those skilled in the art can select according to actual needs. As a preferred solution, the thickness of the fourth active material layer 70 can be 0.1 μm - 100 μm, such as 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 third artificial SEI layer 80 can be 0.1 μm - 1 μm, such as 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.

[0098] According to a specific embodiment of the present invention, referring to Figure 7 , the above-mentioned negative electrode sheet 1000 further includes a fifth active material layer 90 and a sixth active material layer 100. 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 along the 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 arranging the fifth active material layer 90 and the sixth active material layer 100 on the second side of the current collector 10 along the direction away from the current collector 10, and the fifth active material layer 90 includes metallic lithium, it can serve as a supplementary lithium source to improve the cycle life of the battery. The sixth active material layer 100 includes a metallic lithium alloy. On the one hand, it can prevent the highly reactive metallic lithium in the fifth active material layer 90 from directly contacting the electrolyte or the electrolyte. On the other hand, it can enable the metallic lithium in the battery to undergo an alloying reaction with the metallic lithium alloy in the sixth active material layer 100 during the charge and discharge process of the battery, which is beneficial to the uniform deposition of metallic lithium, thereby effectively avoiding problems such as the growth of lithium dendrites caused by the uneven deposition of metallic lithium, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thus being beneficial to improving the cycle stability of the lithium metal battery using the negative electrode sheet 1000. Specifically, the fifth active material layer 90 can be arranged on the second conductive layer 13.

[0099] It should be noted that the thicknesses of the fifth active material layer 90 and the sixth active material layer 100 are not particularly limited, and those skilled in the art can select according to actual needs. As a preferred solution, the thicknesses of the fifth active material layer 90 and the sixth active material layer 100 can be independently 0.1 μm - 100 μm, such as 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.

[0100] According to a specific embodiment of the present invention, referring toFigure 8 Specifically, the negative electrode sheet 1000 further includes a fourth artificial SEI layer 110 disposed on the 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. By providing the fourth artificial SEI layer 110 including a lithium compound on the side of the sixth active material layer 100 away from the current collector 10, it is further conducive to the rapid migration of lithium ions, thereby effectively avoiding problems such as the growth of lithium dendrites caused by the untimely insertion and extraction of lithium ions from the negative electrode, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thus further facilitating the improvement of the cycle stability of the lithium metal battery using the negative electrode sheet 1000.

[0101] It should be noted that the thickness of the fourth artificial SEI layer 110 is not particularly limited, and those skilled in the art can select it according to actual needs. As a preferred solution, the thickness of the fourth artificial SEI layer 110 can be 0.1 μm - 1 μm, for example, it can be 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.

[0102] According to specific embodiments 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 a metal strip as the active material layer onto the surface of the current collector or other active material layers) or physical vapor deposition (PVD, such as magnetron sputtering, vacuum evaporation, etc.). The physical vapor deposition method is preferred. Thus, it is conducive to reducing the thickness of the active material layer, achieving uniform deposition, thereby reducing the amount of active material used and lowering the battery cost. Optionally, the metal lithium alloy Li-M can be formed by magnetron sputtering a metal M onto the surface of the metal Li layer to form an active material layer including the metal lithium alloy. Alternatively, the metal lithium alloy Li-M can be prepared by vacuum evaporation. That is, metal Li and metal M in the form of strips, blocks, etc. are respectively placed in a container (such as an evaporation boat, crucible, etc.). 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.

[0103] According to specific embodiments of the present invention, the first artificial SEI layer 40, the second artificial SEI layer 60, and the fourth artificial SEI layer 110 can independently adopt physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), etc. to directly form a layer of a compound formed by metallic lithium and halogen, oxygen element, nitrogen element, sulfur element, phosphorus element, etc., such as lithium fluoride, lithium oxide, lithium nitride, lithium sulfide, lithium phosphide, etc. Further, lithium phosphate (Li 3 PO 4 ) is subjected to magnetron sputtering in a nitrogen atmosphere to generate a lithium phosphorus oxygen nitrogen compound (LiPON). In addition, methods such as dry coating and wet coating can also be used to directly coat a compound formed by lithium element and halogen, oxygen element, nitrogen element, sulfur element, phosphorus element onto the surface of the negative electrode, such as lithium fluoride (LiF), lithium oxide (Li 2 O), lithium sulfide (Li 2 S), lithium nitride (Li 3 N), lithium phosphide (Li 3 P), and at least one of lithium phosphorus oxygen nitrogen compound (LiPON).

[0104] According to specific embodiments 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 element, nitrogen element, sulfur element, and phosphorus element and M is formed on the fourth active material layer 70 including metallic lithium, and the metal compound layer reacts with lithium atoms derived from the positive electrode during the charging process of the battery to generate a lithium compound and a metallic lithium alloy.

[0105] Thus, by using the negative electrode tab 1000 of the present invention, interface problems of metallic lithium in secondary battery applications can be improved, problems such as continuous thickening of the SEI film, continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the separator can be avoided, thereby being beneficial to improving the cycle stability of the lithium metal battery applying the negative electrode tab 1000.

[0106] In the second aspect of the present invention, the present invention proposes a method for preparing a negative electrode tab. According to an embodiment of the present invention, referring to Figure 9 , the method includes:

[0107] S100: Providing a current collector, the current collector including opposite first and second sides

[0108] In this step, a current collector 10 is provided, and the current collector 10 includes opposite first and second sides. It should be noted that the specific method for preparing the current collector 10 is not particularly limited. For example, it may include: forming a first conductive layer 12 on one side of a base film 11; forming a second conductive layer 13 on the side of the base film 11 away from the first conductive layer 12. By forming the first conductive layer 12 on one side of the base film 11, the conductivity of the current collector 10 can be improved. At the same time, by forming the second conductive layer 13 on the opposite side of the base film 11, the conductivity of the current collector 10 can be further improved.

[0109] S200: Form a first active material layer on the first side of the current collector, and the first active material layer includes metallic lithium

[0110] In this step, a first active material layer 20 is formed on the first side of the current collector 10, and the first active material layer 20 includes metallic lithium. The inventors found that by forming the first active material layer 20 including metallic lithium on the first side of the current collector 10, it can serve as a supplementary lithium source to improve the cycle life of the battery.

[0111] According to a specific embodiment of the present invention, the above-mentioned first active material layer 20 can be formed on the first conductive layer 12.

[0112] S300: Form a second active material layer on the side of the first active material layer away from the current collector, and the second active material layer includes a metallic lithium alloy

[0113] 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 found 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, it can prevent the highly reactive metallic lithium in the first active material layer 20 from directly contacting the electrolyte or the electrolyte. On the other hand, during the charge and discharge process of the battery, an alloying reaction can occur between the metallic lithium and the metallic lithium alloy in the second active material layer 30, which is beneficial to the uniform deposition of metallic lithium, avoiding problems such as the growth of lithium dendrites caused by the uneven deposition of metallic lithium and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thereby being beneficial to improving the cycle stability of the lithium metal battery.

[0114] S400: Form a first artificial SEI layer on the side of the second active material layer away from the first active material layer, and the first artificial SEI layer includes a lithium compound

[0115] 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, and the first artificial SEI layer 40 includes lithium compounds. The inventors found that by forming the first artificial SEI layer 40 including lithium compounds 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 the electrolyte, and on the other hand, it can promote the rapid migration of lithium ions, effectively avoiding problems such as the growth of lithium dendrites caused by the untimely insertion and extraction of lithium ions at the negative electrode, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thereby being beneficial to improving the cycle stability of the lithium metal battery.

[0116] Therefore, the negative electrode tab obtained by using the method for preparing a negative electrode tab of the present invention can improve the interfacial problems of metallic lithium in the application of secondary batteries, avoid problems such as the continuous thickening of the SEI film, the continuous growth of lithium dendrites, dead lithium, and the piercing of the separator by lithium dendrites, thereby being beneficial to improving the cycle stability of the lithium metal battery.

[0117] 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 elaborated here.

[0118] 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 lithium compounds and 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 serve as a supplementary lithium source to improve the cycle life of the battery. By forming the third artificial SEI layer 80 including lithium compounds and 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 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 compounds in the third artificial SEI layer 80 can further facilitate the rapid migration of lithium ions, thereby effectively avoiding problems such as the growth of lithium dendrites caused by untimely insertion and extraction of lithium ions at the negative electrode, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinite volume change rate. On the other hand, the metallic lithium alloy in the third artificial SEI layer 80 can undergo an alloying reaction with metallic lithium during the charge and discharge process of the battery, further facilitating the uniform deposition of metallic lithium, effectively avoiding problems such as the growth of lithium dendrites caused by non-uniform deposition of metallic lithium, and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinite volume change rate, thereby further facilitating the improvement of the cycle stability of the lithium metal battery.

[0119] According to a specific embodiment of the present invention, the above method further includes: forming a fifth active material layer 90 on the second side of the current collector 10, the fifth active material layer 90 including 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 including 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 including a lithium compound. The inventors have found that by forming the fifth active material layer 90 including metallic lithium on the second side of the current collector 10, it can serve as a supplementary lithium source to further improve the cycle life of the battery; by forming the 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, it can prevent the highly reactive metallic lithium in the fifth active material layer 90 from directly contacting the electrolyte or the solid electrolyte, and on the other hand, it can enable an alloying reaction between the metallic lithium and the metallic lithium alloy in the sixth active material layer 100 during the charge and discharge process of the battery, which is further beneficial to the uniform deposition of metallic lithium, avoiding problems such as the growth of lithium dendrites caused by non-uniform deposition of metallic lithium and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate; by forming the 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 prevent the highly reactive metallic lithium in the fifth active material layer 90 from directly contacting the electrolyte or the solid electrolyte, and on the other hand, it can further facilitate the rapid migration of lithium ions, effectively avoiding problems such as the growth of lithium dendrites caused by the untimely insertion and extraction of lithium ions at the negative electrode and the continuous thickening of the SEI film, dead lithium, and the piercing of the separator by lithium dendrites due to an infinitely large volume change rate, thereby further facilitating the improvement of the cycle stability of the lithium metal battery.

[0120] 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 elaborated here.

[0121] In the third aspect of the present invention, the present invention provides a lithium metal battery. According to an embodiment of the present invention, the lithium metal battery includes the above negative electrode sheet or a negative electrode sheet obtained by using the method for preparing the negative electrode sheet described above. Thus, the lithium metal battery has high cycle 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 elaborated here.

[0122] According to an embodiment of the present invention, the above lithium metal battery may include a liquid battery, a semi-solid battery, and a solid-state battery.

[0123] According to specific embodiments of the present invention, the above 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 solution.

[0124] According to specific embodiments of the present invention, the above lithium metal battery may include a liquid laminated soft-pack battery, a liquid wound battery or a liquid cylindrical battery composed of the above negative electrode sheet or a negative electrode sheet obtained by using the method for preparing the negative electrode sheet, a positive electrode sheet, a separator and an electrolyte solution.

[0125] According to specific embodiments of the present invention, the above lithium metal battery may further include a semi-solid laminated soft-pack battery, a semi-solid wound battery or a semi-solid cylindrical battery composed of the above negative electrode sheet or a negative electrode sheet obtained by using the method for preparing the negative electrode sheet, a positive electrode sheet and a gel electrolyte.

[0126] According to specific embodiments of the present invention, the above lithium metal battery may further include a semi-solid laminated soft-pack battery, a semi-solid wound battery or a semi-solid cylindrical battery composed of the above negative electrode sheet or a negative electrode sheet obtained by using the method for preparing the negative electrode sheet, a positive electrode sheet, a gel electrolyte and an optional additive of 0.5 wt% - 50 wt%.

[0127] According to specific embodiments of the present invention, the above electrolyte solution 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.; the lithium salt may include lithium hexafluorophosphate (LiPF 6 )、lithium perchlorate (LiClO 4 )、lithium tetrafluoroborate (LiBF 4 )、lithium hexafluoroarsenate (LiAsF 6 )、other organic lithium salts (such as lithium trifluoromethanesulfonate (LiCF 3 SO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium trifluoromethanesulfonyl-perfluorobutanesulfonylimide (LiTNFSI), lithium fluorosulfonyl-perfluorobutanesulfonylimide (LiFNFSI), lithium bis(oxalato)borate (LiBOB), lithium tris(trifluoromethanesulfonyl)methyl (LiC(SO 2 CF 3 ) 3etc.); the additives may include film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, additives for controlling the water and HF content (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 lithium metal negative electrode (such as fluoroethylene carbonate (FEC), lithium nitrate (LiNO 3 ) etc.).

[0128] According to specific embodiments of the present invention, the above lithium metal battery may include a semi-solid battery and a solid-state battery, and the semi-solid battery and the 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.

[0129] According to specific embodiments of the present invention, the above lithium metal battery may also include a solid-state laminated soft-pack battery, a solid-state wound battery, or a solid-state cylindrical battery composed of the above negative electrode sheet or a negative electrode sheet obtained by the method for preparing the negative electrode sheet, a positive electrode sheet, and a solid electrolyte.

[0130] According to specific embodiments of the present invention, the specific types of the above 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 may 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 may include lithium nickel cobalt manganese oxide (LiN x M y C z O 2 , x + y + z = 1), lithium iron manganese phosphate (LiFe a Mn b PO 4 , a + b = 1), lithium iron phosphate, lithium manganate, lithium cobaltate, lithium nickelate, lithium-rich manganese-based positive electrode material, lithium nickel manganese oxide (LMNO), and lithium vanadium phosphate (Li 3 V 2 (PO 4 ) 3 , LiVOPO 4 ), etc.

[0131] According to specific embodiments of the present invention, the above separator may include polypropylene (PP) and / or polyethylene (PE).

[0132] According to specific embodiments of the present invention, the above-mentioned solid electrolyte may include inorganic solid electrolytes (such as oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes), polymer solid electrolytes, and composite solid electrolytes (such as composite solid electrolytes based on polymer matrices and inorganic fillers), etc. Specifically, the oxide solid electrolyte may include NASICON type (structurally stable, such as LATP (Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 )、LAGP(Li 1.5 Al 0.5 Ge 1.5 P 3 O 12 ), perovskite type, garnet type (with the highest conductivity, 10 -3 S / cm, and relatively good stability against metallic lithium, such as lithium lanthanum zirconium oxide (LLZO)); the sulfide solid electrolyte may include binary compounds (such as Li 2 S-SiS 2 and Li 2 S-P 2 S 5 , Li 2 S-GeS 2 etc.), ternary compounds (such as Li 2 S-MS 2 -P 2 S 5 (M = Si, Ge, Sn, Al, etc.), and Li 6 PS 5 X (X = F, Cl, Br, I) type; the halide solid electrolyte may include Li a MX 4 type (X represents a halogen element, such as Li 2 MnCl 4 , Li 2 ZnCl 4 etc., and halide electrolytes formed by trivalent and other valent metal ions M, such as LiYbF 4 , LiAlF 4 ), Li a MX 6 type (such as Li 3 YCl 6 (LYC) and Li 3 BrCl 6 ) and Li a MX 8 type (such as Li 6 CoCl 8)。The polymer solid electrolyte may include polymer matrices such as polyethylene oxide (PEO), polycarbonate, poly(trimethylene carbonate) (PTMC), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride - hexafluoropropylene) copolymer, lithium polyacrylate (PAL), etc., inorganic fillers such as LATP, lithium lanthanum zirconium oxide (LLZO), aluminum oxide (Al 2 O 3 ), metal - organic frameworks (MOFs), etc., and lithium salts such as LiAsF 6 , lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF 4 ). Specifically, the gel electrolyte may include at least one of the above - mentioned solid electrolytes and at least one of the above - mentioned electrolytes.

[0133] In the fourth aspect of the present invention, a method for preparing a lithium - metal battery is proposed. According to an embodiment of the present invention, the method includes: providing a negative electrode plate, the negative electrode plate includes a current collector having opposite first and second sides, 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 along 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, the first artificial SEI layer includes a lithium compound, a fourth active material layer and a metal compound layer are sequentially arranged on the second side of the current collector along a direction away from the current collector, the fourth active material layer includes metallic lithium; assembling the negative electrode plate into a battery and charging it so that a third artificial SEI layer is formed in situ during the battery charging process, the third artificial SEI layer includes a lithium compound and a metallic lithium alloy (i.e., generating a third artificial SEI layer including a lithium compound and a metallic lithium alloy by an in - situ method), wherein the metal compound layer includes a compound of at least one of halogen, oxygen element, nitrogen element, sulfur element, and phosphorus element 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.

[0134] Specifically, the battery assembled with the above - mentioned negative electrode plate can be charged under the condition of 0.01C - 50C.

[0135] According to a specific embodiment of the present invention, the above - mentioned metal compound layer may include M x+ F - x (i.e., a compound of fluorine element and M), during the battery charging process, M x+ F - xReact with lithium atoms from the positive electrode during battery charging to form M and lithium fluoride (LiF). M can undergo an alloying reaction with metallic lithium to form a Li-M alloy. The reactions involved are as follows:

[0136] M x+ F - x +x Li=M+x LiF,

[0137] M+Li=Li-M.

[0138] According to specific embodiments of the present invention, the above metal compound layer may include M x+ O 2- x / 2 (i.e., a compound of oxygen element and M). During battery charging, M x+ O 2- x / 2 reacts with lithium atoms from the positive electrode during battery charging to form M and lithium oxide (Li 2 O). M can undergo an alloying reaction with metallic lithium to form a Li-M alloy. The reactions involved are as follows:

[0139] M x+ O 2- x / 2 +x Li=M+x / 2Li 2 O,

[0140] M+Li=Li-M.

[0141] It should be noted that M x+ O 2- x / 2 can be a conductive metal oxide and a non-conductive metal oxide. Among them, the conductive metal oxides 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.); the non-conductive metal oxides can be magnesium oxide (MgO), aluminum oxide (Al 2 O 3 ), zinc oxide (ZnO), silicon oxide (SiO x ), tin oxide (SnO), manganese oxide, zirconium oxide ZrO, etc.).

[0142] According to specific embodiments of the present invention, the above metal compound layer may include M x+ S 2- x / 2 (i.e., a compound of sulfur element and M). During battery charging, Mx+ S 2- x / 2 reacts with lithium atoms from the positive electrode during battery charging to form M and lithium sulfide (Li 2 S), and M can undergo an alloying reaction with metallic lithium to form a Li-M alloy. The reactions involved are as follows:

[0143] M x+ S 2- x / 2 +x Li = M + x / 2Li 2 S,

[0144] M + Li = Li-M.

[0145] According to a specific embodiment of the present invention, the above metal compound layer may include M x+ N 3- x / 3 (i.e., a compound of nitrogen element 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 (Li 3 N), and M can undergo an alloying reaction with metallic lithium to form a Li-M alloy. The reactions involved are as follows:

[0146] M x+ N 3- x / 3 +x Li = M + x / 3Li 3 N,

[0147] M + Li = Li-M.

[0148] According to a specific embodiment of the present invention, the above metal compound layer may include M x+ P 3- x / 3 (i.e., a compound of phosphorus element and M). During battery charging, M x+ P 3- x / 3 reacts with lithium atoms from the positive electrode during battery charging to form M and lithium phosphide (Li 3 P), and M can undergo an alloying reaction with metallic lithium to form a Li-M alloy. The reactions involved are as follows:

[0149] M x+ P 3- x / 3 +x Li = M + x / 3Li 3 P,

[0150] M + Li = Li-M.

[0151] Thus, 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.

[0152] In a fifth aspect of the present invention, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device includes the above-mentioned lithium metal battery or a lithium metal battery obtained by the above-mentioned method for preparing a lithium metal battery. The electrical device has the same advantages as the above-mentioned lithium metal battery or the above-mentioned method for preparing a lithium metal battery over the prior art, which will not be elaborated herein.

[0153] Next, the present invention will be described with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0154] Example 1

[0155] A negative electrode sheet, referring to Figure 8 , 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.

[0156] The current collector 10 includes an opposite first side and second side. 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 disposed on the surface of one side of the base film 11, and the second conductive layer 13 is disposed on the surface of the opposite side of the base film 11. The material of the base film 11 is polypropylene with a thickness of 1 μm, the material of the first conductive layer 12 is copper with a thickness of 0.3 μm, and the material of the second conductive layer 13 is copper with a thickness of 0.3 μm.

[0157] The first active material layer 20, the second active material layer 30, and the first artificial SEI layer 40 are sequentially disposed 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, the second active material layer 30 includes an alloy formed by metallic lithium and magnesium with a lithium element content of 2 atm%, and 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 disposed 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, the sixth active material layer 100 includes an alloy formed by metallic lithium and magnesium with a lithium element content of 2 atm%, and the fourth artificial SEI layer 110 includes lithium fluoride. The thicknesses 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 thicknesses of the first artificial SEI layer 40 and the fourth artificial SEI layer 110 are both 1 μm.

[0158] The negative electrode sheet of Example 1 was assembled into a liquid battery:

[0159] 1. Preparation of the positive electrode sheet

[0160] The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 、conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were made into a positive electrode slurry in N-methylpyrrolidone (NMP). The solid content in the positive electrode slurry was 50 wt%, and the mass ratio of LiNi 0.8 Co 0.1 Mn 0.1 O 2 、Super P, and PVDF was 8:1:1. The positive electrode slurry was coated on the upper and lower surfaces of the current collector aluminum foil, dried at 85°C, cold-pressed, then trimmed, sliced, and slit, and finally dried in a vacuum at 85°C for 4 h to make the positive electrode sheet.

[0161] 2. Preparation of the electrolyte

[0162] In a glove box under an argon atmosphere (H 2 O < 0.1 ppm, O 2 < 0.1 ppm), 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). After mixing evenly, an electrolyte with a concentration of 1 mol / L was obtained.

[0163] 3. Separator

[0164] A 16-μm polyethylene film was used as the separator.

[0165] 4. Preparation of the lithium metal battery

[0166] The positive electrode sheet, separator, and negative electrode sheet of Example 1 were stacked in sequence, with the separator placed in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes. After winding, a bare battery cell was obtained, the electrode tabs were welded, the bare battery cell was placed in the outer package, and the above-prepared electrolyte was injected into the dried battery cell. Then, processes such as encapsulation, standing, formation, shaping, and capacity testing were carried out to complete the preparation of the lithium metal battery.

[0167] The cycle performance of the lithium metal battery obtained from the negative electrode sheet of Example 1 was characterized.

[0168] Test method for the cycle performance of the lithium metal battery

[0169] Charge at a constant current of 0.2C under the condition of 25°C ± 2°C. When the battery voltage reaches 4.2V, switch to constant voltage charging and stop charging when the charging current drops to 0.05C. After charging, let it stand for 30 minutes and discharge at a current of 0.3C until the voltage reaches 2.6V. After cycling 50 times according to the above charge-discharge process, disassemble the battery and perform a scanning electron microscope (SEM) test on the negative electrode plate of Example 1.

[0170] It can be seen from the obtained SEM images that the surface of the negative electrode plate of Example 1 is uniform and relatively flat, and no obvious growth of lithium dendrites is observed.

[0171] It can be seen from Example 1 that using the negative electrode plate of the present invention can improve the interface problems in the application of metallic lithium in secondary batteries, avoid problems such as continuous thickening of the SEI film, continuous growth of lithium dendrites, dead lithium, and lithium dendrites piercing the separator, thereby being beneficial to improving the cycle stability of the lithium metal battery using this negative electrode plate.

[0172] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection 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 a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0173] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A negative electrode plate, characterized in that, it includes: a current collector, the current collector includes opposite first and second sides; a first active material layer, a second active material layer and a first artificial SEI layer, 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 along the 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 lithium compound.

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

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

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

6. The negative electrode plate 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 plate according to claim 5 or 6, characterized in that, the thicknesses of the first conductive layer and the second conductive layer are each independently 0.3 μm - 10 μm.

8. The negative electrode plate 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 plate according to claim 5 or 8, characterized in that, the thickness of the base film is 1 μm - 10 μm.

10. The negative electrode plate according to claim 5, characterized in that, it further includes a third active material layer, the third active material layer is provided on the second side of the current collector, and the third active material layer includes a metallic lithium alloy.

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

12. The negative electrode plate according to claim 10, characterized in that, it further includes a second artificial SEI layer, the second artificial SEI layer is provided on the side of the third active material layer away from the current collector, and the second artificial SEI layer includes a lithium compound.

13. The negative electrode plate according to claim 5, characterized in that, it further includes a fourth active material layer and a third artificial SEI layer, the fourth active material layer and the third artificial SEI layer are sequentially arranged on the second side of the current collector along the 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 plate 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 tab according to claim 5, wherein, it further includes a fifth active material layer and a sixth active material layer. The fifth active material layer and the sixth active material layer are sequentially disposed 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 tab according to claim 15, wherein, 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 tab according to claim 15, wherein, it further includes a fourth artificial SEI layer. The fourth artificial SEI layer 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.

18. The negative electrode tab according to claim 1 or 10 or 13 or 15, wherein, the metallic lithium alloy includes an alloy formed by metallic 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 tab according to claim 18, wherein, the content of lithium element in the metallic lithium alloy is 0.1 atm% - 99.9 atm%.

20. The negative electrode tab according to claim 10 or 12, wherein, the thicknesses of the first active material layer, the second active material layer, and the third active material layer are each independently 0.1 μm - 100 μm.

21. The negative electrode tab according to claim 13, wherein, the thickness of the fourth active material layer is 0.1 μm - 100 μm.

22. The negative electrode tab according to claim 15 or 17, wherein, the thicknesses of the fifth active material layer and the sixth active material layer are each independently 0.1 μm - 100 μm.

23. The negative electrode tab according to claim 1 or 12 or 13 or 17, wherein, the lithium compound includes a compound of at least one of halogen, oxygen element, nitrogen element, sulfur element, and phosphorus element and lithium element.

24. The negative electrode tab according to claim 13, wherein, the metallic 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 Li-M is (0.1 - 10):

1.

25. The negative electrode tab according to claim 12, wherein, the thicknesses of the first artificial SEI layer and the second artificial SEI layer are each independently 0.1 μm - 1 μm.

26. The negative electrode tab according to claim 13, wherein, the thickness of the third artificial SEI layer is 0.1 μm - 1 μm.

27. The negative electrode sheet 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, comprising: providing a current collector, the current collector including opposite first and second sides; forming a first active material layer on the first side of the current collector, the first active material layer including metallic lithium; forming a second active material layer on a side of the first active material layer away from the current collector, the second active material layer including a metallic lithium alloy; forming a first artificial SEI layer on a side of the second active material layer away from the first active material layer, the first artificial SEI layer including a lithium compound.

29. The method according to claim 28, characterized in that, further comprising: forming a fourth active material layer on the second side of the current collector, the fourth active material layer including metallic lithium; forming a third artificial SEI layer on a side of the fourth active material layer away from the current collector, the third artificial SEI layer including a lithium compound and a metallic lithium alloy.

30. The method according to claim 28, characterized in that, further comprising: forming a fifth active material layer on the second side of the current collector, the fifth active material layer including 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 including a metallic lithium alloy; 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 including a lithium compound.

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

32. The lithium metal battery according to claim 31, characterized in that, the lithium metal battery includes a liquid battery, a semi-solid battery, and a solid-state battery.

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, 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 trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethylsulfonyl - n - perfluorobutanesulfonylimide, lithium fluorosulfonyl - n - perfluorobutanesulfonylimide, lithium bis(oxalato)borate, and lithium tris(trifluoromethylsulfonyl)methyl.

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 the contents of water and HF, 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 a all-solid-state battery, the semi-solid 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.

38. A method for preparing a lithium metal battery, characterized in that, comprises: providing a negative electrode sheet, the negative electrode sheet includes a current collector having opposite first and second sides, 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 along 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, the first artificial SEI layer includes a lithium compound, a fourth active material layer and a metal compound layer are sequentially arranged on the second side of the current collector along a direction away from the current collector, and the fourth active material layer includes metallic lithium; assembling the negative electrode sheet into a battery and charging the battery so that the metal compound layer forms a third artificial SEI layer in-situ during the charging process of the battery, and the third artificial SEI layer includes a lithium compound and a metallic lithium alloy, wherein the metal compound layer includes a compound of at least one of halogen, oxygen element, nitrogen element, sulfur element, and phosphorus element 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, it includes the lithium metal battery according to any one of claims 31-37 or the lithium metal battery obtained by the method according to claim 38.

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