Metal lithium composite material, metal lithium composite membrane and production system

Abstract

The utility model discloses a metal lithium composite material, a metal lithium composite membrane and a production system, and the metal lithium composite material comprises a metal lithium or lithium alloy matrix and an MXene nanosheet, and the MXene nanosheets are of an oriented layered arrangement structure in the matrix. The lithium metal composite material disclosed by the utility model shows air stability and excellent mechanical property.

Description

Technical Field

[0001] The utility model belongs to the field of metal materials, in particular to a metal lithium composite material and a preparation method, application and production system thereof. Background Art

[0002] Lithium metal is highly chemically active and can cause various uncontrollable adverse reactions when exposed to air, producing heterogeneous pollutants and uneven surfaces. Especially when reacting with moisture, it leads to serious safety hazards, which severely limits the industrial application scenarios of lithium metal.

[0003] In addition, there are currently two difficulties in the processing of metallic lithium materials: First, the mechanical properties of metallic lithium itself are extremely poor and its texture is very soft. Therefore, when metallic lithium is mechanically rolled to a thickness of less than 50 μm, the metallic lithium strip is prone to breakage; when rolled to a thickness of 20 μm or even less, the metallic lithium will adhere to the polymer substrate material due to the pressure exerted by the roller and cannot be separated from the substrate to obtain a continuous ultra-thin lithium strip. At the same time, because metallic lithium has a low hardness and is easily deformed during rolling, the precision requirements of the rolling equipment for preparing ultra-thin lithium are extremely high, which invisibly increases the cost of preparing ultra-thin lithium. Second, when using the melting method to prepare ultra-thin lithium, the liquid lithium metal will be incompatible with most substrates due to the high tension, and will appear as spherical droplets on the substrate, which is not conducive to the spreading and deep processing of metallic lithium on the substrate, and it is difficult to obtain an ultra-thin lithium strip with uniform thickness. Utility Model Content

[0004] In response to the technical problem that metallic lithium has high chemical activity and poor stability in air, the utility model provides a metallic lithium composite material having a directional layered arrangement structure of MXene nanosheets in a metallic lithium or lithium alloy matrix, and the metallic lithium composite material exhibits excellent air stability.

[0005] The first aspect of the present invention provides a metal lithium composite material, which includes: a matrix made of metal lithium or a lithium alloy and MXene nanosheets; the MXene nanosheets are arranged in a directional layered structure in the matrix.

[0006] In some embodiments, the thickness of the lithium metal composite material is ≤1000 μm.

[0007] In some embodiments, the thickness of the lithium metal composite material is ≤500 μm.

[0008] In some embodiments, the thickness of the lithium metal composite material is ≤ 200 μm.

[0009] In some embodiments, the thickness of the lithium metal composite material is ≤100 μm.

[0010] In some embodiments, the thickness of the lithium metal composite material is ≤50 μm.

[0011] In some embodiments, the thickness of the lithium metal composite material is ≤20 μm.

[0012] In some embodiments, the thickness of the lithium metal composite material is ≤10 μm.

[0013] In some embodiments, the chemical formula of the MXene is: n+1 X n T x , wherein M represents one or more transition metal elements Ti, V, Mo, Nb, Ta, W, Zr, Y, X represents one or more carbon, nitrogen or boron elements, T x Represents the presence of functional groups; 1≤ n ≤4.

[0014] In some embodiments, the functional group of the MXene contains fluorine.

[0015] In some embodiments, M in the above MXene is Ti, X is carbon, and T x Contains fluorine element.

[0016] In some embodiments, the lithium alloy is a lithium-magnesium alloy or a lithium-aluminum alloy.

[0017] In some embodiments, the above-mentioned metal lithium composite material forms the directional layered arrangement structure by the following method: mixing molten metal lithium or lithium alloy with MXene nanosheets to obtain a mixed lithium slurry; cooling and solidifying the mixed lithium slurry to obtain a composite lithium ingot; forming the composite lithium ingot into a sheet or foil shape by extrusion and / or rolling, and during the extrusion and / or rolling process, the MXene nanosheets form the directional layered arrangement structure inside the metal lithium matrix.

[0018] 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 to obtain a composite lithium foil.

[0019] In some embodiments, the oriented layered structure in the lithium metal composite material is characterized by scanning electron microscopy. More preferably, the lithium metal in the lithium metal composite material is stripped before scanning electron microscopy testing.

[0020] In some embodiments, the surface of the lithium metal composite material is covered with two-dimensional nanosheets, or the surface of the lithium metal composite material is shown to be covered with two-dimensional nanosheets after metal etching. Scanning electron microscopy can show that the surface of the lithium metal composite material has two-dimensional nanosheets. In some embodiments, before testing and characterization, the surface of the metal composite material is corroded to reveal the two-dimensional nanosheet coverage, and the two-dimensional nanosheets are MXene nanosheets.

[0021] In some embodiments, the X-ray diffraction test (XRD) characterization of the above-mentioned metal lithium composite material has the (002) diffraction peak of MXene, and the diffraction peaks of the metal lithium (110) crystal plane and (200) crystal plane; the intensity ratio of the diffraction peaks of the metal lithium (110) crystal plane and (200) crystal plane is greater than 2.6.

[0022] In some embodiments, the ratio of the diffraction peak intensities of the metallic lithium (110) crystal plane and the (200) crystal plane is greater than 4.2.

[0023] In some embodiments, the ratio of the diffraction peak intensities of the metallic lithium (110) crystal plane and the (200) crystal plane is greater than 5.2.

[0024] In some embodiments, the ratio of the diffraction peak intensities of the metallic lithium (110) crystal plane and the (200) crystal plane is greater than 7.6.

[0025] The second aspect of the present invention provides a metal lithium composite membrane, comprising the metal lithium composite material mentioned above; and a coating layer provided on one side or both sides of the metal lithium composite material.

[0026] In some embodiments, the coating layer in the metal lithium composite film is made of a polymer material.

[0027] In some embodiments, the polymer material is polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP) or polyethylene (PE).

[0028] In some embodiments, the coating layer in the metal lithium composite film is made of a metal material.

[0029] In some embodiments, the metal material is copper foil, aluminum foil, stainless steel foil, nickel foil or titanium foil.

[0030] The third aspect of the present invention provides a production system for the above-mentioned metal lithium composite material, comprising: an inert gas system, a melting device, a cooling and solidifying device, an extrusion device and / or a rolling device; the inert gas system includes an inert gas environment chamber, and the melting device and the cooling and solidifying device are arranged in the inert gas environment chamber; the melting device includes a heater, a container and a stirring device, which is used to heat and melt metal lithium or lithium alloy, mix it with MXene powder, and obtain a mixed lithium liquid; the cooling and solidifying device includes a mold, which is used to cool and solidify the mixed lithium liquid to obtain a composite lithium ingot; the extrusion device is used to extrude the composite lithium ingot into a composite lithium sheet or a composite lithium foil; the rolling device is used to roll the composite lithium ingot into a composite lithium sheet or a composite lithium foil; or, it is used to roll the extruded composite lithium sheet into a composite lithium foil.

[0031] In some embodiments, the production system further comprises: a slitting device for slitting the composite lithium sheet or composite lithium foil into predetermined shapes.

[0032] In some embodiments, the production system further comprises: a winding device for winding the composite lithium sheet or composite lithium foil.

[0033] In some embodiments, the production system further comprises a coating device for coating one or both sides of the composite lithium sheet before the rolling step.

[0034] In some embodiments, the above-mentioned production system further includes the above-mentioned coating device and film stripping device, and the film stripping device is used to remove the coating after the rolling.

[0035] In some embodiments, the production system further includes a drying room system for controlling moisture in the environment, and the extrusion device and / or the rolling device are located in the environment of the drying room system.

[0036] Compared with the prior art, the useful technology of the present invention is:

[0037] The oriented layered structure of MXene nanosheets in the lithium metal composite material of this utility model effectively prevents corrosive agents (such as air) from corroding lithium metal. Even if the surface lithium metal reacts with the corrosive agent, the oriented layered nanosheets act as a physical barrier, increasing the structural tortuosity within the lithium metal composite material and prolonging the path the corrosive agent must traverse to attack the lithium metal. This effectively prolongs the time it takes for the lithium metal to oxidize, or in other words, prevents most of the lithium metal from being oxidized. In other words, the lithium metal composite material of this utility model exhibits excellent air stability. When used in industrial production, it can remain stable in an air environment for a long time, resolving the problem of strict environmental requirements during the manufacturing process due to the flammability and explosiveness of lithium metal due to its easy oxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the processing method of the present invention. Under the action of shear force, the disorderly dispersed MXene nanosheets in the composite lithium ingot form a directional layered arrangement structure.

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

[0040] Figure 3 These are cross-sectional SEM images at different magnifications of the composite lithium foil obtained in Example 2 of the present invention after stripping of metallic lithium.

[0041] Figure 4 This is a cross-sectional SEM image of the ultra-thin composite lithium foil with a thickness of 9 microns obtained in Example 2 of the present invention.

[0042] Figure 5 To test the air stability of the metal lithium 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 at different times were observed.

[0043] Figure 6 This is a comparison chart of the XRD spectra of the metal lithium sheet, the comparative lithium foil and the composite lithium foil of the present invention in Example 2 of the present invention.

[0044] Figure 7 This is a comparison chart of the XRD spectra of composite lithium foils of different thicknesses in Example 2 of the present invention.

[0045] Figure 8 These are the hardness test results of the metal lithium foil, composite lithium foil and comparative lithium foil in Example 2 of the present invention.

[0046] Figure 9 These are the tensile test results of composite lithium foils with different MXene contents, comparative lithium foils, and metallic lithium foils in Example 3 of the present invention.

[0047] Figure 10 These are the electrochemical performance test results of the composite lithium electrode placed in air for 24 hours in Example 4 of the present utility model.

[0048] Figure 11 This is a schematic diagram of a production system for a metal lithium composite material in Example 5 of the present utility model.

[0049] Figure 12 This is a schematic diagram of another production system of a lithium metal composite material in Example 6 of the present utility model.

[0050] Figure 13These are the tensile test results of different composite aluminum-lithium alloy foil samples in Example 9 of the present invention.

[0051] Figure 14 This is a SEM image of the corrosion test of the aluminum-lithium alloy foil (AL) in Example 9 of the present invention.

[0052] Figure 15 This is a SEM image of the corrosion test of the composite aluminum-lithium alloy foil (A-1L-0.5MX) in Example 9 of the present invention.

[0053] Figure 16 These are the tensile performance test results of lead foils with different compositions and composite lead-lithium foil samples in Example 10 of the present invention.

[0054] Main reference numerals:

[0055] 10 - Inert gas system, 11 - Inert gas atmosphere chamber; 20 - Melting device, 21 - Heater, 22 - Container, 23 - Stirring device; 30 - Cooling and curing device, 31 - Mold; 40 - Extrusion device; 50 - Rolling device; 60 - Slitting device; 70 - Laminating device; 80 - Demolding device; 90 - Winding device;

[0056] 100-mixed lithium solution; 200-composite lithium sheet; 300-composite lithium foil; 400-film; 500-film-lithium foil-film composite layer. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is described below through specific embodiments. It should be understood that one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combination step, or other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of arrangement of each method or limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships can also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0058] The raw materials and instruments used in the examples are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods known to those skilled in the art. The MXene nanosheets used in this utility model are MXene Ti3C2T produced by Jinan Sanchuan New Material Technology Co., Ltd. x Powder products.

[0059] The test method for tensile strength of the present invention is a tensile test of a metal strip. The tensile test is carried out in accordance with the national standard GB / T3076-1982 "Metal Sheet (Strip) Tensile Test Method". The size of the tensile sample is prepared in accordance with the national standard GB / T6397-1986 "Metal Tensile Test Specimen". The thickness of the tensile sample is 50 μm.

[0060] The hardness test method is static nanoindentation based on atomic force microscopy.

[0061] Extrusion in the present invention refers to the deformation of metal through a die mouth under the action of strong force, usually using an extruder, and the strong power source can be hydraulic, compressed air or mechanical pressure; rolling refers to the deformation of metal under the action of pressure and shear force when it passes through rotating rollers, which can also be called rolling, rolling or calendering.

[0062] The utility model provides a metal lithium composite material and a processing method thereof, wherein the processing method of the metal lithium composite material comprises the following steps: (1) melting and mixing, mixing molten metal lithium or lithium alloy with MXene to obtain a mixed lithium slurry; (2) solidifying step, cooling and solidifying the mixed lithium slurry to obtain a composite lithium ingot; (3) forming step, providing shear force (Shear Force) to the composite lithium ingot by extrusion and / or roll forming, and forming the composite lithium ingot to obtain a composite lithium sheet or composite lithium foil, which can be used as the negative electrode of a lithium metal battery. Figure 1 As shown, during the melt mixing step, MXene is dispersed in the molten lithium metal or lithium alloy, and the MXene is uniformly and disorderly dispersed in the mixed lithium slurry and the composite lithium ingot. We unexpectedly discovered that the shear force generated by the extrusion and / or rolling processing method in the forming step can cause the disordered MXene nanosheets in the composite lithium ingot to form a directional layered structure in the lithium metal or lithium alloy matrix.

[0063] The present invention also discovered that the shear force generated by the extrusion and / or rolling process in the forming step can also induce the metallic lithium in the composite lithium ingot to expose more lithium Li (110) crystal planes. For lithium metal negative electrodes, since the migration barrier of Li atoms on the Li (110) crystal plane is lower than that on the Li (200) crystal plane, it is easier for Li atoms 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 plane is less prone to dendrite growth than other crystal planes. Therefore, the present invention also provides a method for inducing the production of metallic lithium with a high (110) crystal plane.

[0064] The present invention discovers that oriented layered MXene nanosheets can also become the intrinsic reinforcement phase of metal lithium composite materials, thereby improving the mechanical properties of the metal lithium composite materials, including hardness and tensile strength, and solving the technical problem that metal lithium is easy to break and deform during extrusion or rolling due to its soft texture and low hardness, and is difficult to process. In particular, the present invention can obtain ultra-thin metal lithium with a continuous, uniform thickness and self-supporting property (≤20 microns).

[0065] We also discovered that the extruded / rolled lithium metal composite exhibits excellent air stability. This stems from the inherent corrosion resistance of the MXene nanosheets, coupled with the fact that the oriented, layered MXene nanosheets within the lithium metal or lithium alloy effectively prevent corrosive agents (such as air and electrolyte) from corroding the lithium metal. This effectively prevents the surface lithium metal from reacting with the corrosive agents. The layered MXene nanosheets act as a physical barrier, increasing the structural tortuosity within the lithium metal composite, extending the path that the corrosive agents must traverse to attack the lithium metal. This effectively prolongs the time it takes for the lithium metal to oxidize, or in other words, prevents most of the lithium metal from being oxidized. In other words, the lithium metal composite of the present invention exhibits excellent air stability. When used in industrial production, it can remain stable in an air environment for extended periods of time, resolving the environmental challenges inherent in manufacturing processes, where lithium metal is easily oxidized, flammable, and explosive, and therefore subject to stringent environmental requirements.

[0066] Example 1

[0067] This embodiment provides a lithium metal composite material and a processing method thereof, wherein the processing method comprises the following steps:

[0068] 1) Melt mixing: In a glove box under argon atmosphere, place a metallic lithium block or metallic lithium alloy in a crucible and heat to melt it into a liquid state; add a certain amount of MXene to the liquid metallic lithium and stir to mix evenly. Due to the lithiophilicity of MXene, 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 metallic lithium or lithium and lithium alloy is between (0.1-50):100;

[0069] 2) Cooling and solidifying step: naturally cooling the mixed lithium slurry in step 1 to room temperature and solidifying to obtain a composite lithium ingot; in the embodiment of the present invention, the composite lithium ingot is cylindrical (the internal shape of the container crucible);

[0070] In other embodiments, in order to facilitate subsequent processing and molding, the composite lithium slurry is filled into molds of other shapes (such as blocks or sheets) to obtain composite lithium ingots of different shapes;

[0071] 3) Processing and forming: In a dry room environment, the composite lithium ingot obtained in step 2 is placed in an extrusion and / or rolling device, and the composite metal lithium column is extruded and / or rolled into a metal lithium composite material. The extrusion or rolling process can provide a huge shear force to cause the composite lithium ingot to produce directional deformation.

[0072] In the processing method of the present invention, the melting and cooling solidification of metallic lithium and alloys 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 the present invention, the melting and cooling solidification of metallic lithium and alloys 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, and other tests are carried out in a conventional air environment.

[0073] In one specific embodiment, a composite lithium ingot is placed in an extrusion machine and extruded to produce a composite lithium sheet with a thickness ranging from 100 microns to 1 mm. The resulting composite lithium sheet is then coated with a PET release film on both sides and rolled several times to produce composite lithium foil or ultrathin lithium metal with varying thicknesses (1 to 100 microns). Repeated rolling can optimize the oriented layered structure of the 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 heated and softened before rolling; in some embodiments, the heating and softening temperature is between 50°C and 120°C.

[0074] Then remove the coating and adjust the shape of the composite lithium sheet, composite lithium foil or ultra-thin metallic lithium, such as by shearing or stamping. In specific implementation, we found that the composite lithium foil of the utility model can be easily peeled off from the PET coating. This is because the oriented layered MXene nanosheets are parallel to the coating surface, which reduces the bonding force between the metallic lithium and the coating. This is very beneficial for obtaining a continuous composite lithium foil with uniform thickness, especially suitable for industrial continuous production and large-sized composite lithium foil. In contrast, when the metallic lithium foil is prepared by scraping a mixed lithium slurry on a substrate, there is a technical problem that it is difficult to separate the metallic lithium intact because the metallic lithium is soft and has a high bonding force with the substrate. Therefore, it is difficult to obtain a metallic lithium foil with good continuity and uniform thickness. In particular, this problem is more prominent when preparing large-sized metallic lithium foil.

[0075] This embodiment also provides a coated lithium foil composite layer (metal lithium composite film), comprising a coating-composite lithium foil-coating structure. Because the composite lithium foil is protected by the coating on both sides, the resulting coating-composite lithium foil-coating composite layer has excellent stability and is suitable for long-term storage, avoiding the flammable and explosive storage safety issues of metallic lithium. The coating can be removed by tearing it off during use. In this embodiment of the utility model, the coating is a 0.1mm thick PET release film, which serves to assist in rolling film formation. Other materials or thicknesses may also be used, such as polyimide (PI), polypropylene (PP), or polyethylene (PE).

[0076] In some embodiments, the coating layer can also be made of polymer and / or metal materials, and a metal composite film with a coating layer on one side or both sides is obtained during the rolling process; in a specific implementation, a metal lithium composite film with a metal copper foil on one side is obtained by rolling a composite lithium foil with a metal copper foil during the rolling process; preferably, the thickness of the composite lithium foil is between 1 and 100 microns; the thickness of the copper foil is between 1 and 10 microns; in a preferred embodiment, the thickness of the composite lithium foil is 10 to 20 microns, and the thickness of the copper foil is 3 to 5 microns. In other embodiments, the material of the coating layer provided on one or both sides of the composite lithium foil can also be a polymer material, such as PET, PI, PP, PE, etc.; or, other types of metal materials, such as aluminum foil, nickel foil, stainless steel foil, titanium foil, etc.; or, a composite foil of a polymer and a metal, such as a composite foil formed by PET and a metal copper foil.

[0077] It should be noted that extrusion processing has the advantage of rapid prototyping, but is limited by existing extrusion equipment and processes. In particular, compared with pure lithium, the mechanical properties and hardness of MXene composite lithium metal after reinforcement are increased, which greatly increases the pressure required during the extrusion process and places higher requirements on the extrusion molding die and process. Therefore, it is difficult to extrude composite lithium foil with a thickness of ≤100μm in one go. To obtain thinner lithium foil, the extruded composite lithium sheet is rolled several times to further reduce the thickness. Therefore, a more preferred embodiment of the present invention is to first perform extrusion and then rolling, which can obtain lithium foil with a thickness of ≤100μm (especially lithium foil with a thickness of ≤50μm, or even ≤20μm), and is also more efficient in production.

[0078] Example 2

[0079] This embodiment provides a specific lithium metal composite material and its processing method, wherein MXene is Ti3C2T3 containing fluorine functional groups. x Nanosheets, the processing method steps include:

[0080] In the argon atmosphere of the glove box, 10g of lithium metal was heated to 200℃ and the lithium metal was melted into liquid. 1g of Ti3C2T xThe nanosheets are added to the liquid lithium and stirred continuously until Ti3C2T x The nanosheets are evenly dispersed in liquid lithium to form a mixed lithium slurry; after the mixed lithium slurry is naturally cooled, a composite lithium ingot is obtained;

[0081] In a dry room (dew point below -50°C), the composite lithium ingot was placed in an extrusion device, and the extrusion head pressure and pushing speed were set to 50-150 tons and 1 mm / min, respectively. After obtaining a composite lithium sheet with a thickness of 1 mm, the roller gap distance of the rolling equipment was adjusted to 50 μm under a pressure of 5 tons, and the composite lithium sheet was placed in the rolling equipment to obtain an ultra-thin composite lithium foil. The test showed that its thickness was only 13 μm, and the ultra-thin composite lithium foil showed obvious metallic luster, good continuity and self-support.

[0082] The surface of the ultra-thin composite lithium foil was characterized by scanning electron microscopy (SEM). Figure 2 ), its surface can be seen to be covered with obvious flakes, which are MXene nanosheets. The ultra-thin composite lithium foil is immersed in anhydrous ethanol to remove the metallic lithium. The metallic lithium slowly reacts and dissolves with the ethanol, and the residue (MXene nanosheet) is characterized by cross-sectional SEM ( Figure 3 In (a) and (b), the oriented layered arrangement structure of the two-dimensional nanosheets can be clearly observed, indicating that the MXene nanosheets transform from a disordered state to an ordered oriented layered arrangement during the extrusion process.

[0083] By adjusting the roller gap distance of the rolling equipment, composite lithium foils of different thicknesses (e.g., 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 4 A cross-sectional SEM image of an ultra-thin composite lithium foil with a thickness of only 9 μm obtained after rolling (without stripping of metallic lithium) is given. It can be seen that the ultra-thin composite lithium foil has a uniform thickness and a smooth surface.

[0084] The composite lithium slurry is poured into a cylindrical mold, and after cooling and solidification, it is taken out of the mold and cut into a comparison lithium foil with a thickness of about 50 μm for comparative testing to illustrate the technical effect of extrusion or rolling.

[0085] In order to verify the air stability of the composite lithium foil of the present invention, the composite lithium foil (50 μm) and the comparison lithium foil were punched to obtain test discs and metal lithium sheets (thickness of about 500 μm, purchased from the market) were placed together in an air environment at room temperature (about 25°C) and the surface changes at different times were observed; the test results are as follows: Figure 5As shown, it can be seen that the metal lithium sheet initially has a silvery-white metallic luster. After 60 minutes of air exposure, the surface completely turns into black (lithium nitride). The metal lithium sheet is easily oxidized and nitrided in the air. In contrast, the lithium foil gradually changes from a silvery-white metallic luster to black after 15 minutes, and then gradually changes to grayish-white, indicating the nitridation and oxidation process of the metal lithium sheet. The composite lithium foil of the present invention still has a silvery-white metallic luster after being placed in the air for 360 minutes (6 hours), which shows that it has the best air stability.

[0086] Figure 6 A comparison of the XRD spectra of lithium metal sheets, comparative lithium foil, and the composite lithium foil (50 μm) of the present invention is given. It can be seen that the lithium metal sheet exhibits a sharp, high-intensity diffraction peak at the (200) crystal plane at around 52°, and a significantly low-intensity diffraction peak at the (110) crystal plane at around 36°, indicating that pure lithium metal exhibits a low (110) crystal plane and a high (200) crystal plane; while the composite lithium foil of the present invention is just the opposite, exhibiting a low-intensity diffraction peak at the (200) crystal plane and a high-intensity diffraction peak at the (110) crystal plane. In contrast, the intensities of the (200) and (110) crystal planes of the comparative lithium foil are intermediate. This indicates 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.

[0087] Since the migration barrier of lithium atoms on the lithium (110) crystal plane is lower than that on the lithium (200) plane, it is easy for lithium atoms 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 likely to grow dendrites than other crystal planes. It is common knowledge that controlling the crystallization of lithium with a preferred (110) crystal plane orientation is also an effective strategy for achieving highly reversible lithium metal batteries (LMBs), but there is a lack of simple control methods. (See the 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 regulating metallic lithium with a high (110) crystal face, thereby obtaining a metallic lithium composite material with a high (110) crystal face for use in lithium metal battery electrodes, which is conducive to the production of planar dendrite-free lithium.

[0088] Composite lithium foils of different thicknesses can be obtained by adjusting the roller gap distance of the rolling equipment. Figure 7 The comparison of XRD spectra of composite lithium foils with thicknesses of 50, 100, 200, and 500 μm is given. It can be seen that as the thickness of the composite lithium foil becomes thinner, the intensity of the (110) crystal plane of metallic lithium gradually increases, and the intensity ratio of the (110) crystal plane to the (200) crystal plane of metallic lithium (I (110) :I (200) ) increases from 2.695 at 500μm to 7.646 at 50μm. This phenomenon can be explained by the fact that the huge shear force generated during the extrusion and rolling process promotes the directional layered arrangement of MXene nanosheets. The thinner the composite lithium foil, the greater the shear force it is subjected to. At the same time, the horizontally arranged MXene induces lithium to produce (110) crystal plane slip under the action of pressure, resulting in a composite lithium foil with a high (110) crystal plane. The strength of the (002) crystal plane of MXene decreases with decreasing thickness.

[0089] In order to evaluate the effect of the method of the present invention on the mechanical properties of metallic lithium, the hardness test was carried out on metallic lithium sheet, composite lithium foil and comparative lithium foil. The results are as follows: Figure 8 As shown in the figure, it can be seen that the hardness of the composite lithium foil of the present invention (342.3) is significantly higher than that of the metal lithium foil (10.37) and the comparison 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.

[0090] Example 3

[0091] This example uses a method similar to that of Example 2 to adjust the MXene content and test the air stability of composite lithium foils with different MXene contents. The air stability is represented by the time the sample can maintain its metallic luster under normal temperature air environment. The longer the maintenance time, the better the air stability, as shown in Table 1 below:

[0092] Table 1. Air stability test results of composite lithium foils with different MXene contents in this invention

[0093]

[0094] It can be seen that air stability is related to the MXene content in the lithium metal. A higher MXene content forming a multilayer structure can provide more effective protection. Preferably, the mass ratio of MXene to lithium metal is greater than 1:10, more preferably greater than 1:20, and more preferably greater than 1:10. In some embodiments, the mass ratio of MXene to lithium metal is between (0.1-0.5):1.

[0095] Tensile tests were performed on composite lithium foils with different MXene contents, comparative lithium foils, and metallic lithium foils (pure lithium, 50 μm thick). The stress-strain curves are shown in Figure 2. Figure 9 As shown, Sample 3, with a MXene to lithium metal mass ratio of 1:10, exhibits the highest tensile strength (3.22 MPa), significantly outperforming both the control lithium foil (1.63 MPa) and the metal lithium foil (1.05 MPa). Samples 1 and 2, which incorporate a small amount of MXene, also exhibit significant increases in tensile strength. This indicates that the oriented, layered structure of MXene nanosheets formed after shear extrusion significantly enhances the mechanical properties of the composite lithium foil, resulting in improved tensile strength.

[0096] Example 4

[0097] This example provides a lithium metal battery containing the composite lithium foil of the present invention, specifically, the lithium metal composite material of the present invention is used in a battery. The composite lithium foil (approximately 20 μm thick) obtained by the method of Example 2 was exposed to ambient air for 24 hours before being assembled into a button-type lithium metal battery (CR2032). The charge and discharge performance at various current densities was tested. A composite lithium foil not exposed to air was used as a control.

[0098] The battery assembly method involves placing a small, 16mm diameter, punched-out composite lithium foil as the negative electrode in a glove box with a water and oxygen content below 0.1 ppm. The negative electrode, separator, and positive electrode are then placed in that order. The electrolyte (LB-092) is then added and packaged. 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. The mixture is heated with the solvent NMP to form a slurry, which is then coated onto aluminum foil, dried, and then stamped. A comparison negative electrode battery was assembled using the same method.

[0099] The electrochemical performance test conditions are as follows: using a blue battery test instrument, the assembled full battery was subjected to a 2-3.8V charge and discharge cycle at room temperature in the order of 0.2C, 0.5C, 1C, 2C, 3C, 5C, and 2C. The electrochemical test results are as follows Figure 10 As shown in the figure, the electrochemical performance of the negative electrode sheet after 24 hours of exposure to air is very similar to that of the unexposed negative electrode sheet, indicating that the composite lithium foil of the present invention has excellent air stability, which greatly reduces the stringent requirements for environmental conditions in the production process of metal lithium batteries.

[0100] MXene is a family of two-dimensional materials with similar structures and properties. Its general chemical formula can be expressed as M n+1 X n T x, wherein 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, and boron, 1≤ n ≤4, T x The meaning is that the surface contains functional groups. In the specific embodiment of the present invention, MXene nanosheets composed of other elements can also be selected, such as Nb3C2T x 、V2CT x 、Ti2CT x 、Ti4C3T x 、Ti3CNT x 、VNbCT x 、Ta4C3T x These MXene nanosheets have similar two-dimensional layer 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, and are all included in the technical solution of the present invention. Considering the ease of raw material preparation and cost, the preferred MXene is Ti3C2T3 containing fluorine functional groups. x .

[0101] When composite lithium sheets or lithium foils are used as negative electrodes for lithium batteries, MXene nanosheets containing fluorine (F) functional groups are preferred. The resulting ultrathin lithium metal electrode also features a native LiF layer on its surface, derived from the reaction between the F-containing functional groups on the MXene surface and the lithium metal. As a lithium metal battery electrode, this LiF forms part of the solid electrolyte interface on the lithium negative electrode surface during battery cycling, guiding and homogenizing the flow of lithium ions, resulting in more uniform lithium metal deposition and mitigating the problem of lithium metal dendrite growth.

[0102] In some embodiments, the component of the composite lithium of the present invention can also be a composite of metallic lithium alloy and MXene, such as lithium-magnesium alloy, lithium-aluminum alloy, etc. Through the processing method of the present invention, the MXene nanosheets produce a directional layered arrangement structure in the lithium alloy, or obtain the same or similar technical effects as the present invention, which are all within the technical solution of the present invention.

[0103] In other embodiments, the metal lithium composite material of the present invention can also be used as a catalyst in the fields of medicine, petrochemicals, and fine chemicals, as an electrode material or lithium supplement material in lithium batteries, and for manufacturing lightweight alloys in the metallurgical field.

[0104] Example 5

[0105] This embodiment provides a production system of a metal lithium composite material, which is used for preparing a MXene / metal lithium composite material by the processing method of the present invention, such as Figure 11As shown, it includes: an inert gas system 10, a melting device 20, a cooling and solidifying device 30, an extrusion device 40, a rolling device 50, and a slitting device 60; wherein, the inert gas system 10 includes an inert gas environment chamber 11, the melting device 20 and the cooling and solidifying device 30 are arranged in the inert gas environment chamber 11, and the inert gas environment chamber 11 is used to provide an inert gas environment (such as argon) and control the water and oxygen content to prevent the molten metal lithium or lithium alloy from reacting with water and oxygen; the melting device 20 includes a heater 21, a container 22 and a stirring device 23, which are used to heat and melt the metal lithium or lithium alloy and uniformly mix it with the MXene powder to obtain a mixed lithium liquid 100; the cooling and solidifying device 30 includes at least one mold 31, which is used to cool and solidify the mixed lithium liquid 100 to obtain a composite lithium ingot.

[0106] In this embodiment, a mixed lithium solution 100 is placed in a mold, cooled, and solidified. After demolding, multiple small composite lithium ingots are obtained. These composite lithium ingots are then placed in an extrusion device 40 and extruded to form composite lithium sheets 200. Composite lithium sheets 200 then pass through a rolling device 50, where they undergo multiple rolling cycles to form composite lithium foil 300. The composite lithium foil is then formed into a predetermined shape through a slitting device 60.

[0107] Example 6

[0108] This embodiment provides another production system of lithium metal composite material. The inert gas system 10, melting device 20, and cooling and solidification device 30 are the same as those in embodiment 5. The difference is that Figure 12 As shown, the present invention also includes a coating device 70 for applying a coating layer to one or both sides of the composite lithium sheet 200 before rolling. In this embodiment, double-sided coating is applied to facilitate rolling to obtain a smooth composite lithium foil. After rolling, a coating-lithium foil-coating composite layer 500 is obtained. After the coating is removed by a demolding device 80, a composite lithium foil 300 is obtained. The composite lithium foil 300 is wound into a roll by a winding device 90. The coating is preferably a polymer material. In this embodiment, PET is selected. The composite lithium foil of the present invention can be easily peeled from the PET coating.

[0109] In another embodiment, the film stripping device 80 may not be provided, and the resulting product is a film-lithium foil-film composite layer 500, which is then slit or rolled. Because both sides are protected by the film layer, the film-lithium foil-film composite layer 500 can be adapted for long-term storage, thereby improving the safety of the composite lithium foil. When the composite lithium foil product is needed, the film can be removed by simply tearing off the film.

[0110] In another embodiment, the coating device 70 may not be provided, and the composite lithium sheet 200 may be directly rolled to obtain the composite lithium foil 300 .

[0111] In another embodiment, the composite metal sheet 200 obtained by extrusion directly enters the slitting device 60 to be formed into a predetermined shape, or enters the winding device 70 .

[0112] In another embodiment, the composite lithium ingot may also be directly rolled several times to form a composite lithium sheet or composite lithium foil, and then enter the slitting device 60 to be formed into a predetermined shape, or enter the winding device 70 .

[0113] Because MXene materials are lithiophilic, they can be easily mixed and dispersed in molten lithium. When preparing a composite lithium alloy foil of lithium alloy and MXene, the lithium content in the alloy ranges from 0.1 to 99.9 wt.%, and the mass ratio of the MXene to the metallic lithium in the alloy ranges from 0.01 to 1:1, preferably from 0.1 to 0.5:1.

[0114] Example 7

[0115] This embodiment provides a composite lithium-magnesium alloy foil and a preparation method thereof, which is similar to Example 2, except that, under an argon atmosphere, the molten lithium-magnesium alloy liquid is mixed with MXene nanosheets, cooled and solidified to form a composite lithium-magnesium alloy ingot, and then extruded and / or rolled.

[0116] More specific implementation steps include: heating 10g of lithium metal block to 300℃ under argon atmosphere, melting the lithium metal block into liquid, and adding 1g of Ti3C2T x The nanosheets are dispersed in molten lithium metal solution and stirred for 10 minutes using a metal stirrer to ensure uniform dispersion. 2g of small pieces of magnesium metal flakes are then added and the heating temperature is raised to 650°C to gradually melt the magnesium metal flakes to 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.

[0117] Similarly, in another embodiment, the metal magnesium sheet is replaced with a metal aluminum sheet to obtain a composite lithium aluminum alloy foil.

[0118] Similarly, in another embodiment, Ti3C2T x Nanosheets can also be replaced by other types of MXene, such as Nb2CT x , obtaining a composite lithium-magnesium alloy foil or a composite lithium-aluminum alloy foil.

[0119] Example 8

[0120] This embodiment provides a composite lithium-magnesium alloy foil of magnesium-lithium alloy and MXene and a preparation method thereof, which is similar to Example 2, except that, under an argon atmosphere, the molten magnesium-lithium alloy liquid is mixed with MXene nanosheets, cooled and solidified to form a composite lithium-magnesium alloy ingot, which is then extruded and / or rolled.

[0121] More specific implementation steps include: heating 10g of lithium metal block to 250℃ under argon atmosphere, melting the lithium metal block into liquid, and adding 1g of Ti3C2T x The nanosheets were dispersed in molten lithium metal solution and stirred with a metal stirrer for 10 minutes to make them uniformly dispersed, and then cooled to room temperature to obtain composite lithium metal.

[0122] The magnesium metal block is then heated to 650°C-680°C until it melts into a magnesium metal liquid. A predetermined amount of the composite lithium metal is added to the magnesium metal liquid and stirred to form a composite magnesium-lithium alloy liquid. The alloy is then cooled to room temperature to form a composite magnesium-lithium alloy. Preferably, the composite magnesium-lithium alloy contains 1% to 20% lithium metal by weight and 0.1% to 10% MXene by weight. The resulting composite magnesium-lithium alloy is then extruded and / or rolled to form a composite magnesium-lithium alloy foil.

[0123] In a specific embodiment, the composite magnesium-lithium alloy has a lithium metal content of 16% by mass, a MXene content of 8% by mass, and a magnesium metal content of 76% by mass.

[0124] Example 9

[0125] This embodiment provides a composite aluminum-lithium foil of a metal aluminum-lithium alloy and MXene and a preparation method thereof, which is similar to Example 8, except that metal magnesium is replaced by metal aluminum, and the alloying elements are one or more of metal lithium, magnesium, and copper. The specific preparation method includes: heating 10g of metal lithium block to 250°C under argon gas environment, melting the metal lithium block into liquid state, and adding a certain amount of Ti3C2T x The nanosheets were dispersed in molten lithium metal solution and stirred with a metal stirrer for 10 minutes to make them uniformly dispersed, and then cooled to room temperature to obtain composite lithium metal.

[0126] The metal aluminum block is then heated to 650°C-680°C until it melts into metal aluminum liquid. A certain amount of the above-mentioned composite metal lithium, magnesium flakes, and copper powder are added to the metal aluminum liquid and stirred to obtain a composite aluminum-lithium alloy liquid. The composite aluminum-lithium alloy is cooled to room temperature and then rolled several times to obtain a composite aluminum-lithium alloy foil.

[0127] The composition and corresponding tensile properties of the composite aluminum-lithium alloy foil sample (thickness 100 μm) were obtained (e.g. Figure 13 ) The maximum tensile strength (UTS) is shown in the following table:

[0128] Table 2. Aluminum foil and composite aluminum-lithium foil samples with different compositions and their corresponding maximum tensile strengths

[0129]

[0130] It can be seen that after lithium is added to metallic aluminum, the maximum tensile strength is greatly improved. When 0.5% MXene is added to the sample (A-1L-0.5MX), the maximum tensile strength is shown. The relationship between metal alloy composition and mechanical properties is relatively complex, and its specific mechanism is still unclear.

[0131] Corrosion resistance test: The composite aluminum-lithium foil sample was placed in a commercial aluminum alloy metallographic etchant (diluted nitric acid alcohol) and immersed for 20s and 60s, and then the surface state was observed by SEM test. Figure 14 and 15 Surface SEM images of samples AL and A-1L-0.5MX are shown. Sample AL, which does not contain MXene, exhibits distinct grain boundaries after 20 seconds of etching, indicating that the metal is etched along these boundaries. After 60 seconds, the grain boundaries become more pronounced, and the etching deepens. Sample A-1L-0.5MX, on the other hand, maintains a smooth surface with no distinct grain boundaries after 20 seconds of etching. However, after 60 seconds of etching, fine lines appear on the surface, differing in shape from the grain boundaries of sample AL. This is likely due to the MXene nanosheet coverage. This demonstrates that the MXene-containing composite alloy foil of this invention effectively improves the corrosion resistance of the material.

[0132] Example 10

[0133] This embodiment provides a composite lead-lithium foil of a metal lead-lithium alloy and MXene and a preparation method thereof, which is similar to Example 9, except that the metal aluminum is replaced by metal lead, and the alloying element is metal lithium or magnesium. The specific preparation method includes: heating 10g of metal lithium block to 250°C under argon gas environment, melting the metal lithium block into liquid state, and adding a certain amount of Ti3C2T x The nanosheets were dispersed in molten lithium metal solution and stirred with a metal stirrer for 10 minutes to make them uniformly dispersed, and then cooled to room temperature to obtain composite lithium metal.

[0134] The lead metal is then heated to 380°C to melt it into a lead liquid. A certain amount of composite metal lithium is then added to the molten lead liquid according to the recipe, stirred and evenly dispersed to obtain a composite metal lead liquid. The composite metal lead is then cooled to room temperature to obtain a composite metal lead. The composite metal lead is then passed through a rolling device and rolled several times to obtain a composite lead foil.

[0135] In this example, a composite lead foil with a thickness of 1 mm was obtained and its tensile properties were tested. For comparison, metal lead foil (Pb) and lead-lithium alloy foil (commercial lead alloy Pb alloy) were obtained by the same method but without adding MXene, as shown in Table 3 and Table 4. Figure 16 As shown:

[0136] Table 3. Lead foil and composite lead-lithium foil samples with different compositions and their corresponding maximum tensile strengths

[0137]

[0138] As shown in the table above, the tensile strength of lead-lithium-tin-aluminum alloys (Pb alloys) formed by adding alloying elements to lead alloys is significantly improved. The addition of a small amount of MXene (0.1%-0.2%) to lead-lithium alloys also significantly improves tensile strength compared to pure lead samples. However, the tensile strength improvement achieved by adding only MXene to pure lead (Pb MX0.2) is significantly less than that achieved by the lead-lithium alloy sample containing MXene. This may be due to the metallic lithium content in the lead alloy promoting the uniform dispersion of the MXene throughout the lead-lithium alloy. In particular, the maximum tensile strength of a lead-lithium alloy with a metallic lithium content of 0.3% and a concentration of 0.1-0.2% MXene exceeds that of a commercial lead alloy (Pb alloy), demonstrating that the addition of MXene to lead-lithium alloys can effectively improve the mechanical properties of the material.

[0139] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the present invention to the precise forms disclosed, and it is apparent that many modifications and variations are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the present invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the present invention and various options and variations. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A metal lithium composite material, characterized in that The metal lithium composite material comprises: a matrix made of metal lithium or lithium alloy and MXene nanosheets; the MXene nanosheets are arranged in a directional layered structure in the matrix.

2. The lithium metal composite material according to claim 1, wherein The thickness of the lithium metal composite material is ≤1000 μm.

3. The lithium metal composite material according to claim 2, wherein The thickness is ≤500 μm.

4. The lithium metal composite material according to claim 2, wherein The thickness is ≤200 μm.

5. The metal lithium composite material according to claim 2, wherein The thickness is ≤100 μm.

6. The metal lithium composite material according to claim 2, wherein The thickness is ≤50 μm.

7. The metal lithium composite material according to claim 2, wherein The thickness is ≤20 μm.

8. The metal lithium composite material according to claim 2, wherein The thickness is ≤10 μm.

9. The metal lithium composite material according to claim 1, wherein The lithium alloy is a lithium-magnesium alloy or a lithium-aluminum alloy.

10. The lithium metal composite material according to any one of claims 1 to 9, characterized in that The lithium metal composite material is formed into the oriented layered structure by extrusion or roll forming.

11. The lithium metal composite material according to claim 1, wherein The surface of the metal lithium composite material is covered with two-dimensional nanosheets, or the surface of the metal lithium composite material is shown to be covered with two-dimensional nanosheets after metal etching.

12. A metallic lithium composite film, characterized in that The method comprises the lithium metal composite material according to any one of claims 1 to 11; and a coating layer provided on one side or both sides of the lithium metal composite material.

13. The metal lithium composite film according to claim 12, characterized in that The coating layer is made of metal material; And / or, the coating layer is made of polymer material.

14. The metal lithium composite film according to claim 13, characterized in that The metal material is copper foil, aluminum foil, nickel foil, stainless steel foil or titanium foil; And / or, the polymer material is polyethylene terephthalate, polyimide, polypropylene or polyethylene.

15. A production system for the metal lithium composite material according to any one of claims 1 to 11, characterized in that: include: Inert gas system, melting device, cooling and solidification device, extrusion device and / or rolling device; The inert gas system comprises an inert gas environment chamber, wherein the melting device and the cooling and solidifying device are arranged in the inert gas environment chamber; The melting device includes a heater, a container and a stirring device, which is used to heat and melt metallic lithium or lithium alloy and mix it with MXene powder to obtain a mixed lithium liquid; The cooling and solidifying device includes a mold for cooling and solidifying the mixed lithium liquid to obtain a composite lithium ingot; The extrusion device is used to extrude the composite lithium ingot into a composite lithium sheet or a composite lithium foil; The rolling device is used to roll the composite lithium ingot into a composite lithium sheet or a composite lithium foil; or to roll the extruded composite lithium sheet into a composite lithium foil.

16. The production system according to claim 15, wherein: The production system further comprises: a slitting device for slitting the composite lithium sheet or composite lithium foil into predetermined shapes; and / or, a winding device for winding the composite lithium sheet or composite lithium foil; and / or, a coating device for providing a coating layer on one or both sides of the composite lithium sheet before the rolling step; or, the coating device and a stripping device, the stripping device for removing the coating after the rolling step; And / or, a dry room system is used to control moisture in the environment, and the extrusion device and / or the rolling device are in the environment of the dry room system.

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