Battery containing lithium supplement layer, electrode plate, lithium supplement diaphragm, lithium supplement method and electric device

Abstract

The invention discloses a battery containing a lithium supplement layer, an electrode plate, a lithium supplement diaphragm, a lithium supplement method and an electric device, the battery comprises an electrochemical active substance layer and a diaphragm layer; a lithium supplementing layer is arranged between the electrochemical active substance layer and the diaphragm layer; the lithium supplementing layer contains a composite lithium foil; the preparation method of the composite lithium foil comprises the following steps: mixing molten metal lithium or lithium alloy with MXene to obtain mixed lithium slurry; cooling and curing the mixed lithium slurry to obtain a composite lithium ingot; and extruding and / or rolling the composite lithium ingot to form the composite lithium foil. The lithium supplementing method is simple and is suitable for industrial mass production.

Description

Technical Field

[0001] This invention belongs to the field of lithium batteries, and in particular relates to a battery containing a lithium replenishment layer, an electrode sheet, a lithium replenishment separator, a lithium replenishment method, and an electrical device. Background Technology

[0002] Lithium-ion batteries, due to their advantages such as high specific capacity, high operating voltage, long lifespan, no memory effect, and high safety, have gradually replaced traditional lead-acid, Ni-MH, and Ni-Cd batteries in lightweight devices such as small equipment, measuring instruments, and electrical appliances, and have been widely used. In recent years, with the rapid development of mobile devices, vehicle electrification, grid storage, 5G information transmission technology, biochips, and wearable electronic devices, existing lithium-ion batteries are no longer sufficient to meet application needs, and the market urgently demands high-energy-density batteries that can adapt to different application scenarios.

[0003] Typically, during the initial charge and discharge of a lithium-ion battery, the electrode material and electrolyte react at the solid-liquid interface, forming a solid electrolyte interphase (SEI) film covering the surface of the electrode material. The formation of the SEI film consumes some lithium, leading to lithium loss in the positive electrode material and thus reducing battery capacity and initial efficiency. Furthermore, during lithium-ion battery cycling, the consumption and repair of the SEI film results in varying degrees of irreversible lithium loss within both the positive and negative electrodes, further reducing cycle life. This is particularly pronounced when the active material in the negative electrode is an alloy (such as silicon alloys and tin alloys). Currently, industrially, adding a small amount (<10%) of silicon to a graphite system is used to improve capacity. High-specific-capacity silicon anode materials have achieved initial commercial application. However, the low initial coulombic efficiency of silicon anodes limits their doping amount and also limits the capacity of silicon / graphite composite anodes. Therefore, to improve the initial coulombic efficiency of lithium-ion batteries and reduce lithium consumption due to SEI film formation, lithium replenishment technology for lithium-ion batteries urgently needs development.

[0004] For lithium replenishment layers, controlling the amount of lithium replenished is crucial. This can be achieved by thinning the lithium metal layer; however, ultra-thin lithium metal (thickness ≤ 20 μm) is difficult to process and unstable in air, making it unsuitable for direct use as a lithium replenishment material. Existing lithium replenishment methods typically involve complex processes and structures, such as the patent application "Lithium Replenishment Method for Negative Electrode, Lithium Replenishment Device for Negative Electrode, Negative Electrode, and Battery" (application number 202110821874); or a slurry formed by mixing lithium replenishment additives with electrode materials and coating it onto the electrode sheet. These methods result in low lithium content and introduce non-conductive materials into the electrode sheet, increasing its impedance and thus reducing the battery's electrochemical performance, as seen in the patent application "A Method for Lithium Replenishment to the Positive Electrode of a Lithium-ion Battery" (patent publication number: CN102916164A). Summary of the Invention

[0005] This invention addresses the technical problem that the formation of the SEI film during the initial charge-discharge of lithium ions consumes some lithium, leading to a decrease in initial coulombic efficiency and the need for lithium replenishment. However, due to the difficulty in processing ultrathin metallic lithium and the instability of air, it cannot be directly used as a lithium replenishment material. This invention provides a composite lithium foil for lithium replenishment, its preparation method, and a simple and easy-to-implement lithium replenishment method.

[0006] The first aspect of the present invention provides a battery containing a lithium replenishment layer, the battery comprising an electrochemical active material layer and a separator layer; a lithium replenishment layer is disposed between the electrochemical active material layer and the separator layer; the lithium replenishment layer contains a composite lithium foil; a method for preparing the composite lithium foil includes the following steps: mixing molten metallic lithium or a lithium alloy with MXene to obtain a mixed lithium slurry; cooling and solidifying the mixed lithium slurry to obtain a composite lithium ingot; and forming the composite lithium ingot into a composite lithium foil by extrusion and / or rolling.

[0007] In some embodiments, the composite lithium ingot is first extruded into a composite lithium sheet, and then the composite lithium sheet is rolled several times to reduce its thickness and obtain a composite lithium foil.

[0008] In some embodiments, the thickness of the composite lithium foil is ≤20μm; preferably, the thickness is ≤10μm; more preferably, the thickness is ≤5μm.

[0009] In some embodiments, during the rolling process described above, a coating layer is provided on one or both sides of the composite lithium sheet.

[0010] In some embodiments, the coating material is a polymer material.

[0011] In some embodiments, the coating is polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), or polyethylene (PE).

[0012] In some embodiments, the composite lithium foil is characterized by X-ray diffraction (XRD) testing to have (002) diffraction peaks of MXene, (110) crystal plane diffraction peaks of lithium metal, and (200) crystal plane diffraction peaks; the intensity ratio of the (110) crystal plane diffraction peaks of lithium metal and the (200) crystal plane diffraction peaks is greater than 2.6; preferably, the ratio is greater than 4.2, more preferably, the ratio is greater than 5.2; and more preferably, the ratio is greater than 7.6.

[0013] In some embodiments, the MXene exhibits an oriented layered structure in the composite lithium foil; the scanning electron microscopy (SEM) test of the composite lithium foil can characterize this oriented layered structure; preferably, the metallic lithium in the composite lithium foil is stripped off before the SEM test is performed.

[0014] In some embodiments, the surface of the composite lithium foil is covered with MXene nanosheets; scanning electron microscopy tests show that the surface of the composite lithium foil is covered with two-dimensional nanosheets.

[0015] In some embodiments, the chemical formula of the above-mentioned MXene is represented as: M n+1 X n T x Where M represents one or more of the transition metal elements Ti, V, Mo, Nb, Ta, W, Zr, and Y, X represents one or more of the elements carbon, nitrogen, or boron, and T x The term represents the presence of functional groups; 1 ≤ n ≤ 4; preferably, the functional groups contain fluorine; most preferably, in the MXene, M is Ti, X is carbon, and T is... x It contains fluorine.

[0016] In some embodiments, the alloying elements in the lithium alloy are selected from one or more of Na, Mg, Al, Zn, Sn, V, In, Ag, Au, B, Si, and Ge.

[0017] In some embodiments, the mass ratio of the above-mentioned MXene to lithium metal or lithium metal in the alloy is between (0.01 to 1):1; preferably, it is between (0.1 to 0.5):1.

[0018] In some embodiments, when the amount of lithium metal or lithium alloy is 100 parts by weight, the amount of MXene added is 0.1 to 50 parts; preferably, the amount of MXene added is 0.1 to 30 parts; more preferably, the amount of MXene added is 0.1 to 20 parts; even more preferably, the amount of MXene added is 0.1 to 10 parts; and most preferably, the amount of MXene added is 5 to 10 parts.

[0019] In some embodiments, the tensile strength of the composite lithium foil is more than twice that of metallic lithium of the same size, preferably more than three times.

[0020] In some embodiments, the hardness of the composite lithium foil is more than 10 times that of metallic lithium of the same size; preferably, more than 20 times; more preferably, more than 30 times.

[0021] In some embodiments, the composite lithium foil maintains its metallic luster in air for 1 hour or more; preferably, 2 hours or more; even more preferably, 2 hours or more; more preferably, 3 hours or more; more preferably, 4 hours or more; more preferably, 5 hours or more; and more preferably, 6 hours or more.

[0022] In some embodiments, the battery is a lithium-ion battery, a solid-state battery, or a semi-solid-state battery.

[0023] In some embodiments, the electrochemically active material in the electrochemically active material layer is a lithium-ion battery positive electrode material or a negative electrode material.

[0024] In some embodiments, the positive electrode material is selected from lithium iron phosphate, ternary materials, lithium titanate, lithium cobalt oxide, and lithium manganese oxide; the negative electrode material is selected from one or more of lithium, carbon materials, silicon, silicon-carbon, tin, and tin oxide.

[0025] A second aspect of the present invention provides a method for replenishing lithium in a battery, the battery comprising an electrochemically active material layer, a lithium replenishing layer, and a separator layer; the lithium replenishing method includes the steps of placing the aforementioned composite lithium foil as a lithium replenishing layer between the aforementioned electrochemically active material layer and the aforementioned separator layer.

[0026] A third aspect of the present invention provides an electrode sheet containing a lithium replenishment layer, the electrode sheet comprising: a current collector layer, an electrochemically active material layer, and a lithium replenishment layer; wherein the lithium replenishment layer contains the aforementioned composite lithium foil.

[0027] In some embodiments, the electrode sheet further includes a membrane layer in contact with the lithium replenishment layer.

[0028] A fourth aspect of the present invention provides a method for preparing the above-mentioned electrode sheet, the method comprising the steps of: coating a slurry containing an electrochemically active substance onto a current collector and then drying it to form the electrochemically active substance layer;

[0029] The composite lithium foil is then used as a lithium replenishment layer and placed on the surface of the electrochemically active material layer to obtain the electrode sheet; or, the composite lithium foil is then used as a lithium replenishment layer and placed on the surface of the electrochemically active material layer and the separator layer to obtain the electrode sheet.

[0030] The fifth aspect of the present invention provides a lithium replenishing membrane, the lithium replenishing membrane comprising a lithium replenishing layer and a membrane layer; the lithium replenishing layer is disposed on one or both sides of the membrane layer; the lithium replenishing layer contains the aforementioned composite lithium foil.

[0031] The sixth aspect of the present invention provides a method for preparing a lithium-replenishing separator, the method comprising the steps of: combining the composite lithium foil with the separator layer.

[0032] A seventh aspect of the present invention provides a battery comprising the electrode sheet described above, or the lithium-filling separator described above.

[0033] An eighth aspect of the present invention provides an electrical device comprising a battery as described above. In some embodiments, the electrical device is a means of transportation, such as a car or an electric vehicle.

[0034] A ninth aspect of the present invention provides an energy storage device comprising the aforementioned battery. In some embodiments, the energy storage device is a photovoltaic-supported energy storage system.

[0035] Compared with the prior art, the advantages of the present invention are as follows:

[0036] (1) The composite lithium foil of the present invention exhibits excellent air stability as a lithium replenishment layer in batteries, greatly reducing the stringent environmental requirements during the production of metallic lithium materials and lowering the production risks. (2) The composite lithium foil of the present invention possesses excellent mechanical properties, including tensile strength and hardness, and exhibits excellent continuity and self-support. (3) The lithium replenishment method of the present invention is simple and suitable for large-scale industrial production. (4) The MXene in the composite lithium foil of the present invention itself has excellent electrical conductivity, and its addition to the battery as a lithium replenishment layer will not affect the battery's electrochemical performance. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the processing method of the present invention. Under the action of shear force, the disordered MXene nanosheets in the composite lithium ingot form a directional layered structure.

[0038] Figure 2 The image shows a thickness test photograph of the ultrathin composite lithium foil obtained in Example 2 of this invention, with the result showing a thickness of 13 μm.

[0039] Figure 3 This is a surface SEM image of the ultrathin composite lithium foil obtained in Example 2 of the present invention.

[0040] Figure 4 These are cross-sectional SEM images of the composite lithium foil obtained in Example 2 of this invention after the metallic lithium has been stripped away, under different magnifications.

[0041] Figure 5 This is a cross-sectional SEM image of the ultrathin composite lithium foil with a thickness of 9 micrometers obtained in Example 2 of the present invention.

[0042] Figure 6To test the air stability of the lithium metal sheet, the comparative lithium foil, and the composite lithium foil of the present invention in Example 2 of the present invention, the test discs were placed in the air and the changes in surface properties were observed at different times.

[0043] Figure 7 This is a comparison diagram of the XRD spectra of the lithium metal sheet, the comparative lithium foil, and the composite lithium foil of the present invention in Example 2 of the present invention.

[0044] Figure 8 This is a comparison diagram of the XRD patterns of composite lithium foils of different thicknesses in Example 2 of the present invention.

[0045] Figure 9 The results show the hardness test results of the metallic lithium foil, composite lithium foil, and comparative lithium foil in Example 2 of this invention.

[0046] Figure 10 The tensile test results are for composite lithium foils with different MXene contents, comparative lithium foils, and metallic lithium foils in Example 3 of the present invention.

[0047] Figure 11 The results show the electrochemical performance of the composite lithium electrode placed in air for 24 hours in Example 4 of this invention.

[0048] Figure 12 This is a schematic diagram of the structure of the electrode sheet containing the lithium replenishment layer in Embodiment 7 of the present invention.

[0049] Figure 13 This is a schematic diagram of the structure of an electrode sheet containing a coating layer in some embodiments of the present invention.

[0050] Figure 14 This is a schematic diagram of the stacking of multilayer rolled electrode sheets in some embodiments of the present invention.

[0051] Figure 15 This is a schematic diagram of the stacking of multilayer pressed electrode sheets in some embodiments of the present invention.

[0052] Figure 16 This is a schematic diagram of the lithium replenishment layer structure in Embodiment 10 of the present invention, including a single-sided lithium replenishment layer membrane and a double-sided lithium replenishment layer membrane.

[0053] Figure 17 This is a schematic diagram of a lithium-filled separator structure containing a coating layer in some embodiments of Embodiment 10 of the present invention.

[0054] Figure 18 This is a schematic diagram of the stacking of multiple lithium-filling separators by rolling or pressing in some embodiments of Embodiment 10 of the present invention.

[0055] Figure 19 This is a schematic diagram of the composite electrode sheet in Embodiment 11 of the present invention.

[0056] Key reference numerals:

[0057] A10 - Electrode sheet, A11 - Current collector layer, A12 - Electrochemical active material layer, A13 - Lithium replenishment layer, A14 - Coating layer; A20 - Lithium replenishment separator, A21 - Separator layer, A22 - Lithium replenishment layer; A23 - Coating layer; A30 - Composite electrode sheet. Detailed Implementation

[0058] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0059] The raw materials and instruments used in the examples are not specifically limited in their source; they can be purchased from the market or prepared according to conventional methods well known to those skilled in the art. The MXene nanosheets used in this invention are MXene Ti3C2T produced by Jinan Sanchuan New Materials Technology Co., Ltd. x Powder products.

[0060] The tensile strength test method of this invention is a tensile test of metal strip. The tensile test is carried out in accordance with the national standard GB / T3076-1982 "Metallic Sheet (Strip) Tensile Test Method". The tensile sample size is prepared in accordance with the national standard GB / T6397-1986 "Metallic Materials Tensile Test Specimens". The thickness of the tensile sample is 50 μm.

[0061] The hardness testing method was static nanoindentation based on atomic force microscopy.

[0062] In this invention, extrusion refers to the deformation of metal through a die orifice under strong force, usually using an extrusion press, with the strong power source being hydraulic pressure, compressed air, or mechanical pressurization; rolling refers to the deformation of metal under pressure and shear force as it passes through rotating rolls, and can also be called rolling, roll pressing, or calendering.

[0063] This invention provides a composite lithium foil and its preparation method, comprising the following steps: (1) melt mixing, mixing molten lithium metal or lithium alloy with MXene to obtain a mixed lithium slurry; (2) a curing step, cooling and curing the mixed lithium slurry to obtain a composite lithium ingot; and (3) a forming step, processing the composite lithium ingot by extrusion and / or roll forming to provide shear force, thereby obtaining a composite lithium sheet or composite lithium foil. Figure 1 As shown, MXene is dispersed in molten lithium metal or lithium alloy during the melt mixing step, and MXene is uniformly and disorderedly dispersed in the mixed lithium slurry and composite lithium ingot. We unexpectedly found that the shear force generated by the extrusion and / or rolling processes during the forming step can enable the disordered MXene nanosheets in the composite lithium ingot to form an oriented layered structure in the lithium metal or lithium alloy matrix.

[0064] The present invention also found that the shear force generated by the extrusion and / or rolling processes during the forming step can induce more lithium Li(110) crystal faces to be exposed in the composite lithium ingot. For lithium metal anodes, since the migration barrier of Li atoms on the Li(110) crystal face is lower than that on the Li(200) crystal face, they are more likely to diffuse and migrate laterally on the Li(110) surface, resulting in planar dendrite-free lithium deposition. It is generally believed that the Li(110) crystal face is less prone to dendrite growth than other crystal faces. Therefore, the present invention also provides a method for inducing the formation of high (110) crystal facet lithium metal.

[0065] For lithium replenishment layers, controlling the amount of lithium replenishment is crucial. This can be achieved by reducing the thickness of the lithium metal layer. However, processing ultrathin lithium metal presents two main challenges: First, lithium metal itself has extremely poor mechanical properties and is very soft. Therefore, when lithium metal is mechanically rolled to a thickness below 50 μm, the lithium strip is prone to breakage. When rolled to a thickness of 20 μm or even less, the lithium metal adheres to the polymer substrate material due to the pressure applied by the rollers, making it impossible to separate from the substrate and obtain a continuous ultrathin lithium strip. Simultaneously, because lithium metal has low hardness, it is prone to deformation during rolling, resulting in extremely high precision requirements for the rolling equipment used to prepare ultrathin lithium, which increases the cost of ultrathin lithium production. Second, when using the melt method to prepare ultrathin lithium, the liquid lithium metal has high surface tension, causing it to be incompatible with most of the substrate, forming spherical droplets on the substrate. This is detrimental to the spreading and deep processing of lithium metal on the substrate, making it difficult to obtain ultrathin lithium with uniform thickness.

[0066] This invention discovers that oriented, layered MXene nanosheets can also serve as an intrinsic reinforcing phase in lithium metal composites, improving the mechanical properties of lithium metal composites, including hardness and tensile strength. This solves the technical problem that lithium metal is prone to fracture and deformation during extrusion or rolling due to its soft texture and low hardness, making it difficult to process. In particular, the processing method of this invention can produce ultrathin lithium metal with a thickness (≤20 micrometers) that is continuous, uniform in thickness, and self-supporting.

[0067] In addition, due to MXene's good lithium affinity, MXene can be uniformly mixed with molten lithium or lithium alloys. By adjusting the content of MXene, the content of metallic lithium in the composite lithium foil of the present invention can also be controlled, thereby regulating the lithium content in the lithium replenishment layer.

[0068] We also found that the composite lithium foil after extrusion / rolling exhibits excellent air stability. This is due to the corrosion-resistant properties of MXene nanosheets themselves. Furthermore, the oriented, layered arrangement of MXene nanosheets within metallic lithium or lithium alloys effectively prevents corrosion of lithium metal by corrosive substances (such as air and electrolyte), thus preventing the reaction between the surface lithium metal and the corrosive substances. The layered arrangement of MXene nanosheets acts as a physical barrier, increasing the structural tortuosity within the metallic lithium composite material and lengthening the path that corrosive substances must traverse to corrode the metallic lithium. This effectively prolongs the oxidation time of the metallic lithium, or in other words, prevents the oxidation of most of the metallic lithium. In other words, the composite lithium foil of this invention exhibits excellent air stability. When used in industrial production, it can be stably placed in the air environment for a relatively long time, solving the problem of stringent environmental requirements during the manufacturing process due to the easy oxidation, flammability, and explosiveness of metallic lithium.

[0069] Example 1

[0070] This embodiment provides a composite lithium foil and its processing method, wherein the processing method includes the following steps:

[0071] 1) Melting and mixing: Under the argon atmosphere in a glove box, place the lithium metal block or lithium metal alloy in a crucible and heat it to melt it into a liquid state; add a certain amount of MXene to the liquid lithium metal and stir to mix evenly. Since MXene has a lithium affinity, the mixed lithium slurry after the addition of MXene turns into a viscous gel state; preferably, the mass ratio of the added MXene to the mass of lithium metal or lithium and lithium alloy is between (0.1~50):100.

[0072] 2) Cooling and solidification step: The mixed lithium slurry in step 1 is naturally cooled to room temperature and solidified to obtain a composite lithium ingot; in the embodiments of the present invention, the composite lithium ingot is cylindrical (the internal shape of the container crucible);

[0073] In other embodiments, to facilitate subsequent processing and molding, the composite lithium slurry is filled into molds of other shapes (such as cubes or sheets) to obtain composite lithium ingots of different shapes.

[0074] 3) Processing and shaping: In a dry environment, the composite lithium ingot obtained in step 2 is placed in an extrusion and / or rolling equipment to extrude and / or roll the composite lithium metal column into sheet or foil. Extrusion or rolling can provide huge shear force to cause directional deformation of the composite lithium ingot.

[0075] In the processing method of this invention, the melting and cooling solidification of lithium metal and alloy are carried out in an inert gas environment, and the extrusion and rolling processes are carried out in a dry room environment to control the moisture in the environment. In a specific embodiment of this invention, the melting and cooling solidification of lithium metal and alloy are carried out in an argon environment, and the extrusion and rolling processes are carried out in a dry room environment with a dew point below -50°C. All other tests are carried out in a conventional air environment.

[0076] In one specific embodiment, a composite lithium ingot is placed in an extrusion apparatus and extruded to obtain a composite lithium sheet with a thickness between 100 micrometers and 1 millimeter. The resulting composite lithium sheet is then coated on both sides with a PET release film and subjected to several rolls to obtain composite lithium foils or ultrathin lithium metal of different thicknesses (1 to 100 micrometers). Multiple rolls can optimize the oriented layered arrangement structure of MXene and adjust the mechanical properties of the composite lithium foil or ultrathin lithium metal. In some preferred embodiments, the composite lithium foil or ultrathin lithium metal is softened by heating before rolling; in some embodiments, the softening temperature is between 50 and 120°C.

[0077] In this embodiment of the invention, a 0.1 mm thick PET release film is selected for coating, which serves to assist in roll forming. Other materials or thicknesses can also be selected, such as polyimide (PI), polypropylene (PP), or polyethylene (PE).

[0078] The coating is then removed, and the shape of the composite lithium sheet, composite lithium foil, or ultrathin lithium metal is adjusted, such as by shearing or stamping. In practice, we found that the composite lithium foil of this invention can be easily peeled off from the PET coating. This is because the oriented, layered MXene nanosheets are parallel to the coating surface, reducing the adhesion between the lithium metal and the coating. This is highly beneficial for obtaining continuous, uniformly thick composite lithium foils, especially suitable for continuous industrial production and large-size composite lithium foils. In contrast, when preparing lithium metal foil by coating a mixed lithium slurry onto a substrate, the soft texture and high adhesion of lithium metal to the substrate present technical challenges in achieving complete separation. Therefore, obtaining continuous, uniformly thick lithium metal foils is difficult, especially when preparing large-size lithium metal foils.

[0079] This embodiment also provides a coated lithium foil composite layer (metal lithium composite film), comprising a coated-composite lithium foil-coated structure. Because the composite lithium foil has coatings on both sides for protection, the resulting coated-composite lithium foil-coated composite layer exhibits excellent stability, making it suitable for long-term storage and avoiding the flammable and explosive safety issues associated with storing metallic lithium. The coating can be simply peeled off during use.

[0080] It should be noted that extrusion processing has the advantage of rapid prototyping, but it is limited by existing extrusion equipment and processes. In particular, compared with pure lithium, the mechanical properties and hardness of MXene-reinforced lithium metal are increased, which greatly increases the pressure required during extrusion. This places higher demands on the extrusion molds and processes, making it difficult to obtain composite lithium foil with a thickness ≤100μm in a single extrusion. To obtain thinner lithium foil, we further reduce the thickness by rolling the extruded composite lithium sheet several times. Therefore, in a more preferred embodiment of the present invention, extrusion is followed by rolling, which can obtain lithium foil with a thickness ≤100μm (especially lithium foil with a thickness ≤50μm, or even ≤20μm), and the production is also more efficient.

[0081] Example 2

[0082] This embodiment provides a specific composite lithium foil and its processing method, wherein MXene is Ti3C2T containing fluorine functional groups. x Nanosheets, the processing steps include:

[0083] Under an argon atmosphere in a glove box, 10g of lithium metal was heated to 200℃ until it melted into a liquid state. 1g of Ti3C2T was then taken... x Nanosheets were added to liquid lithium and stirred continuously until Ti3C2T was obtained. x Nanosheets are uniformly dispersed in liquid lithium to form a mixed lithium slurry; after the mixed lithium slurry cools naturally, a composite lithium ingot is obtained.

[0084] In a dry room (dew point below -50℃), the composite lithium ingot was placed in an extrusion apparatus. The extrusion head pressure and pushing speed were set to 50-150 tons and 1 mm / min, respectively, to obtain a composite lithium sheet with a thickness of 1 mm. After adjusting the roll gap of the rolling equipment to 50 μm under a pressure of 5 tons, the composite lithium sheet was placed in the rolling equipment to obtain an ultra-thin composite lithium foil, the thickness of which was only 13 μm. Figure 2 Furthermore, the ultrathin composite lithium foil exhibits a distinct metallic luster and demonstrates good continuity and self-support.

[0085] The surface of the obtained ultrathin composite lithium foil was characterized by scanning electron microscopy (SEM). Figure 3As can be seen, its surface has obvious sheet-like coverings, which are MXene nanosheets. After the ultrathin composite lithium foil was immersed in anhydrous ethanol to remove metallic lithium, cross-sectional SEM characterization was performed. Figure 4 In Figures a and b), the oriented layered structure can be clearly observed, indicating that the MXene nanosheets transform from a disordered state to an ordered oriented layered structure during the extrusion process.

[0086] By adjusting the roll gap distance of the rolling mill, composite lithium foils of different thicknesses (e.g., from 1 μm to 1000 μm) can be obtained. In some specific embodiments of the present invention, composite lithium foils of different thicknesses of 9 μm, 13 μm, 20 μm, 50 μm, 100 μm, 200 μm, and 500 μm were obtained. Figure 5 A cross-sectional SEM image of an ultrathin composite lithium foil with a thickness of only 9 μm obtained after rolling (without stripping off metallic lithium) is presented. It can be seen that the ultrathin composite lithium foil has a uniform thickness and a smooth surface.

[0087] The composite lithium slurry was poured into a cylindrical mold, cooled and solidified, and then removed from the mold and cut into a comparison lithium foil with a thickness of about 50 μm for comparative testing to illustrate the technical effects of extrusion or rolling.

[0088] To verify the air stability of the composite lithium foil of the present invention, the obtained composite lithium foil (50 μm), the test disc obtained by stamping the control lithium foil, and the metallic lithium sheet (approximately 500 μm thick, purchased from the market) were placed together in an air environment at room temperature (approximately 25°C), and the surface changes were observed at different times; the test results are as follows. Figure 6 As shown, the lithium metal sheet initially has a silvery-white metallic luster, but after 60 minutes of air exposure, the surface completely turns black (lithium nitride). The lithium metal sheet is easily oxidized and nitrided in air. In contrast, the lithium foil gradually changes from a silvery-white metallic luster to black after 15 minutes, and then gradually turns to grayish-white, indicating the nitriding and oxidation process of the lithium metal sheet. The composite lithium foil of the present invention still has a silvery-white metallic luster after being placed in air for 360 minutes (6 hours), showing the best air stability.

[0089] Figure 7A comparison of the XRD patterns of lithium metal sheets, a comparative lithium foil, and the composite lithium foil (50 μm) of the present invention is presented. It can be seen that the lithium metal sheet exhibits a sharp, high-intensity diffraction peak on the (200) crystal plane at approximately 52°, while showing a significantly low-intensity diffraction peak on the (110) crystal plane at approximately 36°. This indicates that pure lithium metal exhibits a low (110) crystal plane and a high (200) crystal plane. Conversely, the composite lithium foil of the present invention exhibits a low-intensity diffraction peak on the (200) crystal plane and a high-intensity diffraction peak on the (110) crystal plane. In comparison, the intensity of the (200) and (110) crystal planes of the comparative lithium foil is moderate. This demonstrates that the addition of MXene nanosheets and extrusion / rolling treatment can adjust the crystal plane orientation of lithium metal, thereby obtaining a lithium metal composite material with a high (110) crystal plane.

[0090] Because the migration barrier of lithium atoms on the lithium (110) crystal plane is lower than that on the lithium (200) plane, they are more likely to diffuse and migrate laterally on the lithium (110) surface, resulting in planar dendrite-free lithium deposition. Therefore, it is generally believed that the lithium (110) plane is less prone to dendrite growth than other crystal planes. Common knowledge suggests that controlling the crystallization of lithium batteries with preferred (110) crystal plane orientation is also an effective strategy for achieving highly reversible lithium metal batteries (LMBs), but a simple control method is lacking. (See article: Directing (110) Oriented Lithium Deposition through High-flux Solid Electrolyte Interphase for Dendrite-free Lithium Metal Batteries, Angewandte Chemie International Edition, 2023(62)42, https: / / doi.org / 10.1002 / anie.202309622). In response to this technical problem, the present invention also provides a simple and easy method for controlling high (110) crystal plane lithium metal, and obtaining the composite lithium foil with high (110) crystal plane is beneficial for producing planar dendrite-free lithium.

[0091] Composite lithium of different thicknesses can be obtained by adjusting the roll gap distance of the rolling mill. Figure 8 Comparison of XRD spectra of composite lithium foils with thicknesses of 50, 100, 200, and 500 μm are presented. It can be seen that as the thickness of the composite lithium foil decreases, the intensity of the (110) crystal plane of lithium metal gradually increases, and the intensity ratio of the (110) crystal plane to the (200) crystal plane of lithium metal (I110) increases. (110) :I (200)The strength of MXene nanosheets increased from 2.695 at 500 μm to 7.646 at 50 μm. This phenomenon can be explained by the fact that the extrusion and rolling process generates huge shear forces, which cause the MXene nanosheets to be oriented and layered. The thinner the composite lithium is, the greater the shear force it experiences. At the same time, the horizontally arranged MXene induces the exposure of the (110) crystal plane of lithium under pressure, resulting in a composite lithium foil with a high (110) crystal plane. The strength of the (002) crystal plane of MXene decreases as the thickness decreases.

[0092] To evaluate the effect of the method of this invention on the mechanical properties of lithium metal, hardness tests were performed on lithium metal sheets, composite lithium foils, and control lithium foils. The results are as follows: Figure 9 As shown, the hardness of the composite lithium foil of the present invention (342.3) is significantly higher than that of metallic lithium foil (10.37) and comparative lithium foil (29.7). This is also the reason why the composite lithium foil obtained by the method of the present invention exhibits excellent self-supporting properties.

[0093] Example 3

[0094] This embodiment uses a method similar to that of Example 2, adjusting the MXene content and testing the air stability of composite lithium foils with different MXene contents. Air stability is expressed as the time it takes for the sample to maintain a metallic luster in room temperature air; a longer retention time indicates better air stability, as shown in the table below.

[0095] Table 1. Air stability test results of composite lithium foils with different MXene contents according to the present invention

[0096]

[0097] It is evident that air stability is related to the MXene content in lithium metal. A higher MXene content, forming a multilayer structure, can more effectively provide protection. Preferably, the mass ratio of MXene to lithium metal is greater than 1:10, more preferably greater than 1:20, and even more preferably greater than 1:10. In some embodiments, the mass ratio of MXene to lithium metal is between (0.1 and 0.5):1.

[0098] Tensile tests were conducted on composite lithium foils with different MXene contents, control lithium foils, and metallic lithium foils (pure lithium, 50 μm thick). The stress-strain curves are shown below. Figure 10As shown, sample 3, with an MXene to lithium metal mass ratio of 1:10, exhibits the highest tensile strength (3.22 MPa), significantly superior to the control lithium foil (1.63 MPa) and lithium metal foil (1.05 MPa). Samples 1 and 2, with the addition of small amounts of MXene, also show a significant increase in tensile strength. This demonstrates that the oriented layered structure of MXene formed after shear extrusion significantly improves the mechanical properties of the composite lithium foil, resulting in better tensile strength.

[0099] Example 4

[0100] This embodiment provides a lithium metal battery containing the composite lithium foil of the present invention. The composite lithium foil (approximately 20 μm thick) obtained by the method in Example 2 was placed in room temperature air for 24 hours, and then assembled into a coin cell lithium metal battery (CR2032). The charge and discharge performance at different current densities was tested. The composite lithium foil not exposed to air was used as a control sample.

[0101] The specific assembly method of the battery includes: in a glove box with a water and oxygen content of less than 0.1 ppm, composite lithium foil stamped into small discs (16 mm in diameter) is used as the negative electrode, and placed in the order of negative electrode, separator, and positive electrode. Electrolyte (LB-092) is then added and the battery is sealed. The positive electrode material is lithium iron phosphate. Following standard laboratory testing methods, the positive electrode material, binder, and conductive carbon black are mixed in an 8:1:1 ratio, heated to a slurry state using NMP solvent, coated onto aluminum foil, dried, and then stamped. A comparative negative electrode battery was assembled using the same method.

[0102] The electrochemical performance testing conditions were as follows: using a Blue Battery testing instrument, the assembled full cells were subjected to charge-discharge cycles of 2-3.8V at room temperature, following the charge-discharge rate sequence of 0.2C, 0.5C, 1C, 2C, 3C, 5C, 2C. The electrochemical test results are as follows: Figure 11 As shown, the electrochemical performance of the negative electrode after 24 hours of exposure to air is very similar to that of the unexposed control negative electrode. This demonstrates that the composite lithium foil of the present invention exhibits excellent air stability, significantly reducing the stringent environmental requirements during the production of lithium metal batteries.

[0103] MXenes are a family of two-dimensional materials with similar structures and properties, and their general chemical formula can be represented as M. n+1 X n T x Where M is selected from one or more of Ti, V, Mo, Nb, Ta, W, Zr, and Y; X is selected from one or more of carbon, nitrogen, or boron, 1 ≤ n ≤ 4, and T x This means that the surface contains functional groups. In specific embodiments of this invention, MXene nanosheets composed of other elements, such as Nb3C2T, can also be selected.x V2CT x Ti2CT x Ti4C3T x Ti3CNT x VNbCT x Ta4C3T x Etc. These MXene nanosheets possess similar two-dimensional layered structures and surface functional groups, and are used to produce the same or similar effects as the method of the present invention when combined with metallic lithium or lithium alloys. All of these are included in the technical solution of the present invention. Considering the ease of raw material preparation and cost, MXene with fluorine-containing functional groups is preferred for Ti3C2T. x .

[0104] In some embodiments, the composite lithium foil of the present invention may also be a composite of lithium metal alloy and MXene, such as lithium magnesium alloy, lithium aluminum alloy, etc. The processing method of the present invention enables MXene nanosheets to form a directional layered structure in the lithium alloy, or achieves the same or similar technical effects as the present invention, all of which are within the technical solution of the present invention.

[0105] Because MXene is lithiophilic, it can be easily mixed and dispersed in molten lithium metal. In preparing the composite lithium alloy foil of lithium alloy and MXene, the lithium content in the alloy is between 0.1 and 99.9 wt.%; for lithium replenishment applications, a lithium alloy with a lithium content greater than 50 wt.% is preferred, more preferably, the lithium content is greater than 80 wt.%, and the mass ratio of MXene to lithium metal in the alloy is between (0.01 to 1):1; preferably, between (0.1 to 0.5):1.

[0106] Example 5

[0107] This embodiment provides a composite lithium-magnesium alloy foil and its preparation method, which is similar to that of Embodiment 2. The difference is that, under an argon atmosphere, molten lithium-magnesium alloy liquid is mixed with MXene nanosheets, cooled and solidified to form a composite lithium-magnesium alloy ingot, which is then subjected to extrusion and / or rolling processing.

[0108] More specific implementation steps include: heating 10g of lithium metal to 300℃ under argon atmosphere until the lithium metal melts into a liquid state, and then adding 1g of Ti3C2T... x Nanosheets are dispersed in molten lithium metal and stirred for 10 minutes to ensure uniform dispersion. Then, 2g of small pieces of magnesium metal are added, and the temperature is raised to 650℃ to gradually melt the magnesium metal and form a mixed lithium-magnesium slurry. The mixed magnesium-lithium slurry is then cooled and solidified into a composite lithium-magnesium ingot, which is then extruded and / or rolled into sheets or foils.

[0109] Similarly, in another embodiment, the magnesium sheet is replaced with an aluminum sheet to obtain a composite lithium-aluminum alloy foil.

[0110] Similarly, in another embodiment, Ti3C2T x Nanosheets can also be replaced with other types of MXene, such as Nb2CT. x This yields composite lithium-magnesium alloy foil or composite lithium-aluminum alloy foil.

[0111] Example 6

[0112] This embodiment provides a composite lithium-magnesium alloy foil of magnesium-lithium alloy and MXene and its preparation method. Similar to Embodiment 2, the difference is that, under an argon atmosphere, molten magnesium-lithium alloy liquid is mixed with MXene nanosheets, cooled and solidified to form a composite lithium-magnesium alloy ingot, which is then subjected to extrusion and / or rolling processing.

[0113] More specific implementation steps include: heating 10g of lithium metal to 250℃ in an argon atmosphere until the lithium metal melts into a liquid state, and then adding 1g of Ti3C2T... x Nanosheets were dispersed in molten lithium metal and stirred for 10 minutes with a metal stirrer to ensure uniform dispersion. The mixture was then cooled to room temperature to obtain composite lithium metal.

[0114] The magnesium block is then heated to 650℃-680℃ until it melts into molten magnesium. A certain amount of composite lithium is added to the molten magnesium, and the mixture is stirred to obtain a composite magnesium-lithium alloy liquid. This liquid is then cooled to room temperature to obtain a composite magnesium-lithium alloy. Preferably, the mass content of lithium in the composite magnesium-lithium alloy is between 1% and 20%, and the mass content of MXene is between 0.1% and 10%. The obtained composite magnesium-lithium alloy is further extruded and / or rolled to obtain a composite magnesium-lithium alloy foil.

[0115] In one specific embodiment, the composite magnesium-lithium alloy contains 16% lithium metal by mass, 8% MXene by mass, and 76% magnesium metal by mass.

[0116] Example 7

[0117] This embodiment provides an electrode sheet containing a lithium replenishment layer and its preparation method, such as... Figure 12 As shown, the lithium replenishment effect is achieved by combining the composite lithium foil of the present invention with an electrode sheet. The electrode sheet A10 includes: a current collector layer A11, an electrochemically active material layer A12, and a lithium replenishment layer A13, wherein the lithium replenishment layer A13 is a composite lithium foil obtained by the method described above in the present invention. Preferably, the thickness of the composite lithium foil is between 1 μm and 20 μm, more preferably, between 1 μm and 10 μm; and even more preferably, between 1 μm and 5 μm.

[0118] The preparation method of the electrode sheet includes the following steps: coating a slurry containing electrochemically active material onto the current collector layer A11 and drying it to form an electrochemically active material layer A12; and then depositing the composite lithium foil of the present invention onto the surface of the electrochemically active material layer A12 to obtain the electrode sheet.

[0119] The electrode can be either a positive or negative electrode. When it is a positive electrode, the electrochemically active material is the positive electrode material; when it is a negative electrode, the electrochemically active material is the negative electrode material. In lithium-ion batteries, electrochemically active materials include positive and negative electrode materials. Positive electrode materials include ternary materials, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium manganese iron phosphate, and high-nickel ternary materials. Negative electrode materials include graphite, mesophase carbon microspheres (MCMB), petroleum coke, carbon fiber, pyrolytic resin carbon, etc., including metal oxides, transition metal oxides, lithium titanate, tin alloy negative electrodes, silicon suboxide, silicon-carbon composite materials, and silicon materials.

[0120] Example 8

[0121] This embodiment provides a specific positive electrode sheet containing a lithium replenishment layer and its preparation method, wherein the electrochemical active material is lithium iron phosphate (LiFePO4), and the preparation method includes the following steps:

[0122] LiFePO4 powder, conductive carbon black, and PVDF binder are mixed in a predetermined ratio, and then N-methylpyrrolidone (NMP) solvent is added to prepare a slurry. This slurry is then coated onto the surface of the current collector aluminum foil to form a film. After vacuum drying, a positive electrode material layer is formed. The composite lithium foil of the present invention is then placed on the surface of the positive electrode material layer, and after roll bonding, a positive electrode sheet containing a lithium replenishment layer is obtained.

[0123] In one specific embodiment, LiFePO4 powder, conductive carbon black, and binder are mixed in a ratio of 8:1:1; the thickness of the composite lithium foil of the present invention is 5 μm.

[0124] In another embodiment, LiFePO4 can be replaced with other types of cathode materials to obtain a cathode sheet containing a lithium replenishment layer.

[0125] This embodiment also provides a battery containing a lithium replenishment layer. The obtained positive electrode sheet containing the lithium replenishment layer is assembled with a separator, a negative electrode sheet, electrolyte, etc., according to existing battery assembly structures and methods to obtain a battery containing a lithium replenishment layer. In a specific battery embodiment, the negative electrode material in the negative electrode sheet is graphite.

[0126] Example 9

[0127] This embodiment provides a specific negative electrode sheet containing a lithium replenishment layer and its preparation method, wherein the electrochemical active material is a silicon-carbon negative electrode material, and the preparation method includes the following steps:

[0128] Silicon carbon powder, conductive carbon black, and binder (styrene-butadiene rubber latex SBR) are mixed in a predetermined ratio, and then water is added to form a slurry. This slurry is then coated onto the surface of a current collector copper foil to form a film. After vacuum drying, a negative electrode material layer is formed. The composite lithium foil of the present invention is then placed on the surface of the negative electrode material layer, and after roll bonding, a negative electrode sheet containing a lithium replenishment layer is obtained.

[0129] In one specific embodiment, silicon carbide powder, conductive carbon black, and binder are mixed in a ratio of 8:1:1; the thickness of the composite lithium foil of the present invention is 5 μm.

[0130] In another embodiment, silicon carbon powder can be replaced with other types of anode materials to obtain an anode sheet containing a lithium replenishment layer.

[0131] This embodiment also provides a battery containing a lithium replenishment layer. The resulting negative electrode sheet containing the lithium replenishment layer is assembled with a separator, a positive electrode sheet, an electrolyte, etc., according to existing battery assembly structures and methods to obtain a battery containing a lithium replenishment layer. In a specific battery embodiment, the positive electrode material in the positive electrode sheet is a high-nickel ternary material.

[0132] In some embodiments, during the roll-forming process of the composite lithium foil, one side of the composite lithium foil is in contact with the electrochemically active material layer, and the other side is provided with a coating layer A14, such as... Figure 13 As shown, the coating layer is preferably a smooth PET film, and the composite lithium foil can be easily peeled off from the surface of the PET film.

[0133] In some embodiments, the above-mentioned roll-forming composite process for preparing electrode sheets containing lithium replenishment layers can be multi-layer roll-forming composite, such as... Figure 14 As shown, a coating layer A14 (PET film) is placed on the surface of the lithium replenishment layer A13, and then an electrode sheet A10 is placed on it for rolling, which can improve production efficiency.

[0134] In another embodiment, the above-mentioned preparation of the electrode sheet containing the lithium replenishment layer can be carried out by multilayer pressing, such as... Figure 15 As shown, a coating layer A14 is placed between the multilayer electrode sheets A10, and then the layers are pressed together.

[0135] Example 10

[0136] This embodiment provides a lithium-replenishing separator and its preparation method. The lithium-replenishing separator is obtained by combining the composite lithium foil of this invention with a separator, thereby achieving a lithium-replenishing effect. Figure 16 The lithium replenishing membrane A20 includes a membrane layer A21 and a lithium replenishing layer A22, wherein the membrane layer A21 is a membrane material, such as a polymer porous membrane, a glass fiber membrane, a solid electrolyte membrane, etc.; and the lithium replenishing layer A22 is the composite lithium foil of the present invention.

[0137] The preparation method of the composite separator includes the following steps: depositing the composite lithium foil of the present invention on at least one side of the separator layer A21 to obtain a lithium-replenishing separator. The composite method can be rolling or pressing.

[0138] In use, the obtained separator containing the lithium replenishment layer is combined with the positive electrode, negative electrode, electrolyte, etc., according to the existing battery assembly structure and method to obtain a battery containing the lithium replenishment layer.

[0139] In one specific embodiment, a solid electrolyte separator for lithium-ion batteries is rolled together with the composite lithium foil of the present invention to obtain a separator containing lithium replenishment. Preferably, the thickness of the composite lithium foil is 1 to 10 μm; in one specific embodiment, the thickness is 5 μm.

[0140] In some embodiments, during the composite lithium foil roll lamination process, one side of the composite lithium foil contacts the separator layer, and the other side is configured as a coating layer A23, such as... Figure 17 As shown, the coating layer A23 is preferably a smooth PET film, and the composite lithium foil can be easily peeled off from the surface of the PET film.

[0141] In some embodiments, when preparing a separator containing a lithium replenishment layer using the above-mentioned roll-forming composite process, it can be a multilayer roll-forming composite, such as... Figure 18 As shown, a coating layer A23 (PET film) is placed on the surface of the lithium replenishment layer A22, and then one or more layers of separator layer A20 are placed before rolling or pressing, which can improve production efficiency.

[0142] Example 11

[0143] This embodiment provides a composite electrode sheet, which is similar to the electrode sheets described in embodiments 7 to 9, except that, as Figure 19 As shown, a separator layer A21 is also composited on the surface of the lithium replenishment layer A13. The composite electrode sheet A30 is sequentially provided with a current collector layer A11, an electrochemically active material layer A12, a lithium replenishment layer A13, and a separator layer A21.

[0144] In practice, a slurry containing electrochemically active material is first coated on the surface of the current collector layer A12. After vacuum drying, an electrochemically active material layer A12 is formed, resulting in an electrochemically active material-current collector layer. Then, a composite lithium foil is placed between the separator layer A21 and the above-mentioned electrochemically active material-current collector layer, and after roll bonding, the composite electrode sheet A30 is obtained.

[0145] The separator layer A21 and the electrochemically active material layer A12 in the composite electrode sheet A30 can serve as protective layers for the lithium replenishment layer A13, which is beneficial for long-term placement and storage. When reassembling the battery, it is only necessary to pair this composite electrode sheet with another electrode sheet, reducing the battery assembly process, simplifying the battery production process, and improving battery production efficiency.

[0146] This embodiment also provides a battery containing a lithium replenishment layer, the battery including a current collector layer A11, an electrochemical active material layer A12 and a separator layer A21, with a lithium replenishment layer A13 between the electrochemical active material layer A12 and the separator layer A21.

[0147] In summary, this invention also provides a simple method for replenishing lithium in lithium-ion batteries. Because the composite lithium foil of this invention possesses excellent air stability, mechanical strength, and adjustable thickness, it can be used as a lithium replenishing layer between the separator and the electrochemical active material layer during battery production. Specifically, the composite lithium foil can be first laminated with an electrode sheet to obtain an electrode sheet with a lithium replenishing layer, and then assembled into a battery; alternatively, the composite lithium foil can be laminated with a separator to obtain a separator with a lithium replenishing layer, and then assembled into a battery; or the composite lithium foil can be placed between the separator and the electrochemical active material layer during battery assembly. The composite component MXene in the composite lithium foil of this invention has excellent conductivity and can also improve the conductivity of the electrode sheet.

[0148] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A battery containing a lithium replenishment layer, characterized in that, The battery includes an electrochemical active material layer and a separator layer; a lithium replenishment layer is disposed between the electrochemical active material layer and the separator layer; the lithium replenishment layer contains composite lithium foil; The method for preparing the composite lithium foil includes the following steps: mixing molten metallic lithium or lithium alloy with MXene to obtain a mixed lithium slurry; After the mixed lithium slurry is cooled and solidified, a composite lithium ingot is obtained; the composite lithium ingot is then formed into a composite lithium foil by extrusion and / or rolling.

2. The battery as described in claim 1, characterized in that, In the above steps, the composite lithium ingot is first extruded into a composite lithium sheet, and then the composite lithium sheet is rolled several times to reduce its thickness to obtain a composite lithium foil; preferably, the thickness of the composite lithium foil is ≤20μm; more preferably, the thickness is ≤10μm; and even more preferably, the thickness is ≤5μm.

3. The battery as described in claim 2, characterized in that, During the rolling process, a coating layer is provided on one or both sides of the composite lithium sheet; preferably, the coating layer is made of a polymer material; more preferably, the polymer material is polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), or polyethylene (PE).

4. The battery as described in any one of claims 1 to 3, characterized in that, The composite lithium foil was characterized by X-ray diffraction (XRD) testing, showing the presence of (002) diffraction peaks of MXene, and diffraction peaks of the (110) and (200) crystal planes of lithium metal; the intensity ratio of the (110) and (200) crystal plane diffraction peaks of lithium metal was greater than 2.6; preferably, the ratio was greater than 4.2, more preferably, the ratio was greater than 5.2; and even more preferably, the ratio was greater than 7.

6. And / or, the MXene exhibits an oriented layered arrangement structure in the composite lithium foil; And / or, the surface of the composite lithium foil is covered with MXene nanosheets.

5. The battery as described in claim 1, characterized in that, The chemical formula of MXene is: M n+1 X n T x Where M represents one or more of the transition metal elements Ti, V, Mo, Nb, Ta, W, Zr, and Y, X represents one or more of the elements carbon, nitrogen, or boron, and T x The term represents the presence of functional groups; 1 ≤ n ≤ 4; preferably, the functional groups contain fluorine; most preferably, in the MXene, M is Ti, X is carbon, and T is... x Contains fluorine; And / or, the alloying elements in the lithium alloy are selected from one or more of Na, Mg, Al, Zn, Sn, V, In, Ag, Au, B, Si, and Ge; And / or, the mass ratio of the MXene to lithium metal or lithium metal in the alloy is between (0.01 to 1):1; preferably, between (0.1 to 0.5):1; And / or, when the amount of lithium metal or lithium alloy is 100 parts, the amount of MXene added is 0.1 to 50 parts; preferably, the amount of MXene added is 0.1 to 30 parts; more preferably, the amount of MXene added is 0.1 to 20 parts; even more preferably, the amount of MXene added is 0.1 to 10 parts; most preferably, the amount of MXene added is 5 to 10 parts.

6. The battery as claimed in claim 1, characterized in that, The tensile strength of the composite lithium foil is more than twice that of metallic lithium of the same size, preferably more than three times; And / or, the hardness of the composite lithium foil is more than 10 times that of metallic lithium of the same size; preferably, more than 20 times; more preferably, more than 30 times. And / or, the composite lithium foil maintains its metallic luster in air for more than 1 hour; preferably, more than 2 hours; even more preferably, more than 2 hours; more preferably, more than 3 hours; more preferably, more than 4 hours; more preferably, more than 5 hours; more preferably, more than 6 hours.

7. The battery as claimed in claim 1, characterized in that, The battery is a lithium-ion battery, a solid-state battery, or a semi-solid-state battery. And / or, the electrochemical active material in the electrochemical active material layer is a positive electrode material or a negative electrode material of a lithium-ion battery; preferably, the positive electrode material is selected from lithium iron phosphate, ternary materials, lithium titanate, lithium cobalt oxide, and lithium manganese oxide; the negative electrode material is selected from one or more of lithium, carbon materials, silicon, silicon-carbon, tin, and tin oxide.

8. A method for replenishing lithium in a battery, characterized in that, The battery includes an electrochemical active material layer, a lithium replenishment layer, and a separator layer; the lithium replenishment method includes the following steps: using a composite lithium foil as any one of claims 1 to 5 as a lithium replenishment layer, disposed between the electrochemical active material layer and the separator layer.

9. An electrode sheet containing a lithium replenishment layer, characterized in that, The electrode sheet comprises: a current collector layer, an electrochemically active material layer, and a lithium replenishment layer; the lithium replenishment layer contains a composite lithium foil as described in any one of claims 1 to 6; Alternatively, the electrode sheet may comprise: a current collector layer, an electrochemically active material layer, a lithium replenishment layer, and a separator layer; wherein the lithium replenishment layer contains a composite lithium foil as described in any one of claims 1 to 6.

10. A method for preparing an electrode sheet as described in claim 9, characterized in that, The preparation method includes the following steps: coating a slurry containing electrochemically active substances onto a current collector layer and then drying it to form the electrochemically active substance layer; The composite lithium foil is then used as a lithium replenishment layer and placed on the surface of the electrochemically active material layer to obtain the electrode sheet; or, the composite lithium foil is then used as a lithium replenishment layer and placed on the surface of the electrochemically active material layer and the separator layer to obtain the electrode sheet.

11. A lithium-replenishing separator, characterized in that, The lithium replenishing membrane includes a lithium replenishing layer and a membrane layer; the lithium replenishing layer is disposed on one or both sides of the membrane layer; the lithium replenishing layer contains a composite lithium foil as described in any one of claims 1 to 5.

12. A method for preparing a lithium-supplemented separator as described in claim 11, characterized in that, The preparation method includes the following steps: combining the composite lithium foil with the separator layer.

13. A battery, characterized in that, It contains the electrode sheet as described in claim 9, or the lithium-filling separator as described in claim 11.

14. An electrical appliance or energy storage device, characterized in that, The electrical device contains a battery as described in any one of claims 1 to 6; Or, the battery as described in claim 13.

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