Lithium-copper integrated composite negative electrode material and preparation method and application thereof

Abstract

The invention provides a lithium-copper integrated composite negative electrode material and a preparation method and application thereof, and belongs to the technical field of electrochemical energy storage, the lithium-copper integrated composite negative electrode material comprises a copper foil, a lithium alloy layer and a carbon layer which are stacked in sequence, the lithium alloy layer comprises lithium metal and lithium-loving metal, the lithium-loving metal comprises at least one of silver, zinc, tin, aluminum and magnesium, and the carbon layer is a carbon layer. The carbon layer is made of a carbon material subjected to thermal reduction treatment. The lithium alloy layer and the carbon layer are coated on the surface of the copper foil, so that the bonding degree between metal lithium and the copper foil can be enhanced, the interface impedance between the lithium negative electrode and the copper foil is reduced, the transmission of electrons is facilitated, and higher conductivity and stronger interface bonding force are provided; the carbon layer has high conductivity and good lithium ion transmission capacity, interface impedance can be effectively reduced, uneven deposition of lithium metal on the copper substrate is inhibited, and formation of lithium dendrites is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly relates to a lithium-copper integrated composite anode material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its ultra-high theoretical specific capacity (3860 mAh / g) and low electrochemical potential (-3.04 V vs. standard hydrogen electrode), lithium metal has become one of the most ideal anode materials. However, lithium metal is prone to dendrite formation during charge and discharge processes, which may cause short circuits and lead to safety problems of the battery. In addition, lithium metal anodes also face problems of poor cycle life and Coulombic efficiency. Especially during charge and discharge cycles, an uneven lithium deposition layer will form on the surface of lithium metal, resulting in the loss of active lithium and an increase in interfacial impedance. These problems limit the popularization of lithium metal anodes in practical applications. Therefore, how to solve the problems of dendrite growth and volume expansion of lithium metal anodes has become a key technical problem in this field.

[0003] In the structural design of lithium metal batteries, copper is widely used as a current collector material on the anode side of the battery. Copper materials have good electrical conductivity and mechanical strength, and can provide a stable support substrate for the deposition of lithium. However, the bonding between traditional copper current collectors and lithium metal layers is not strong enough, which may cause uneven deposition of lithium during charge and discharge, thereby affecting the cycle performance of the battery. Therefore, enhancing the bonding force between the copper substrate and lithium metal and forming a uniform lithium deposition layer on its surface have become an important research direction for optimizing the performance of lithium-copper batteries.

[0004] In existing lithium-copper battery anode materials, the main strategies adopted include physical modification and chemical modification. For example, materials such as carbon nanotubes and graphene are coated on the copper substrate to improve its electrical conductivity and interfacial stability; or methods such as nickel plating and silver plating are used to increase the uniformity of lithium deposition. However, although these modification methods have improved the performance of the anode material to a certain extent, there are still some problems. For example, the stability of the physical coating layer is poor and it is easy to fall off during charge and discharge; the chemical plating layer may increase the interfacial impedance due to incompatibility with lithium metal. In addition, these modification methods are often complex in process and high in cost, which is not conducive to large-scale production and practical applications. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a lithium-copper integrated composite anode material, a preparation method thereof, and an application thereof, aiming to solve the problems of dendrite growth and volume expansion of the lithium metal anode on the copper foil substrate; currently, the stability of the physical coating layer provided on the copper foil substrate is poor and it is easy to fall off during charge and discharge; the technical problem that setting a chemical plating layer may increase the interfacial impedance due to incompatibility with lithium metal.

[0006] In a first aspect, an embodiment of the present application provides a lithium-copper integrated composite negative electrode material, which includes a copper foil, a lithium alloy layer, and a carbon layer stacked in sequence. The lithium alloy layer includes lithium metal and a lithium-philic metal. The lithium-philic metal includes at least one of silver, zinc, tin, aluminum, and magnesium. The carbon layer is made of a carbon material after thermal reduction treatment.

[0007] In some embodiments, the carbon material includes at least one of graphene, carbon nanotubes, carbon spheres, and activated carbon.

[0008] In some embodiments, the mass ratio of the lithium-philic metal to the lithium metal is 1:(5 - 10).

[0009] In some embodiments, the thickness ratio of the copper foil, the lithium alloy layer, and the carbon layer is (5 - 20):(10 - 100):(1 - 5).

[0010] In a second aspect, an embodiment of the present application provides a method for preparing a lithium-copper integrated composite negative electrode material, including the following steps: S1. Heat and melt the lithium metal and the lithium-philic metal, then coat them on the copper foil, and obtain a copper foil-lithium alloy layer after cooling; S2. After thermally reducing the carbon material, disperse it in a solvent to obtain a dispersion liquid, drop the dispersion liquid on the surface of the copper foil-alloy layer, and heat and dry it to obtain a lithium-copper integrated composite negative electrode material.

[0011] In some embodiments, in step S1, the heating and melting temperature is 250°C - 400°C, and the heating time is 10 - 30 min.

[0012] In some embodiments, the thermal reduction conditions of the carbon material in step S2 are: perform thermal reduction under the protection of an inert gas, the thermal reduction temperature is 500°C - 1000°C, and the thermal reduction time is 0.5 - 5 h.

[0013] In some embodiments, the solvent in step S2 is at least one of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0014] In some embodiments, the concentration of the dispersion liquid is 0.1 - 1 mg / mL.

[0015] In a third aspect, an embodiment of the present application provides a lithium metal battery, including the above-mentioned lithium-copper integrated composite negative electrode material.

[0016] Different from the prior art solutions, the beneficial effects of the present application include: 1. By introducing a lithium alloy layer on the copper foil in this application, the deposition uniformity and structural stability of lithium metal can be enhanced. In the integrated structure of the copper foil - lithium alloy layer, there is a large electron cloud around the lithiumophilic metal atoms in the lithium alloy layer, which can combine with the deposited lithium metal to form an alloy during the charge - discharge cycle, enabling the deposition of lithium metal to grow along the planar direction of the lithium alloy layer and effectively inhibiting the growth of lithium dendrites; by introducing lithiumophilic metals such as silver, zinc, tin, aluminum, and magnesium into the lithium alloy layer, the binding force between these lithiumophilic metals and lithium and copper is very strong. Therefore, the lithiumophilic metal can also enhance the bonding degree between metallic lithium and the copper foil, reduce the interfacial impedance between the lithium negative electrode and the copper foil, facilitate the transmission of electrons, provide higher conductivity and stronger interfacial binding force, and enhance the structural stability of the negative electrode material.

[0017] Meanwhile, in this application, a carbon layer composed of carbon materials after thermal reduction treatment is modified on the surface of the lithium alloy layer. The carbon materials after thermal reduction treatment have carbon defect sites and vacancies. The energy barriers at the carbon defect sites and vacancies are low, and the lithiumophilic elements in the lithium alloy can provide more electron clouds to interact with the defect sites with low energy barriers to form fast channels, thereby promoting the movement of lithium ions along the defect sites, increasing the adsorption and diffusion rate of lithium ions on the surface, and improving the electro - chemical reactivity of lithium ions. By coating the lithium alloy layer and the carbon layer on the surface of the copper foil in this application, the lithium ion transmission path is increased. By regulating the lithium ion insertion / extraction kinetics, the energy barrier is reduced, the high - rate discharge performance is improved, and the stability of the battery during fast charge - discharge is enhanced.

[0018] 2. The carbon layer has high conductivity and good lithium ion transmission ability, which can effectively reduce the interfacial impedance and inhibit the non - uniform deposition of lithium metal on the copper substrate, reducing the formation of lithium dendrites. Setting a carbon layer on the surface of the negative electrode not only improves the energy density of the battery, but also can accelerate the charge - discharge rate of the battery, enabling the battery to have higher rate performance.

[0019] 3. Lithium is prone to volume expansion during the charge - discharge process, while the carbon layer can limit the expansion of lithium to a certain extent. The copper foil - lithium alloy layer - carbon layer structure in this application can reduce the impact of volume effects on the negative electrode material, thereby maintaining the stability of the battery structure.

[0020] 4. There are often compatibility problems between lithium metal and the electrolyte, which are likely to trigger side reactions. The carbon layer can isolate part of the direct contact with the electrolyte, reduce the occurrence of side reactions, thereby improving the stability of the negative electrode and the overall Coulomb efficiency of the battery.

[0021] The above description is only an overview of the technical solution of this application. In order to understand the technical means of this application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of this application more obvious and understandable, the following specific embodiments of this application are specifically given. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0023] Figure 1 It is the scanning electron microscope (SEM) image of the surface of the lithium-copper integrated composite anode material with a surface protective layer prepared in Example 1 of the present invention.

[0024] Figure 2 a is the rate performance test chart of the lithium-lithium symmetric battery assembled with the anode material of Comparative Example 1 at different current densities; Figure 2 b is the rate performance test chart of the lithium-lithium symmetric battery assembled with the anode material of Example 1 at different current densities.

[0025] Figure 3 It is the cycle performance test of assembling a lithium-lithium symmetric battery using the anode of Comparative Example 1 and the anode material prepared in Example 1.

[0026] Figure 4 a-4d are respectively the scanning electron microscope test charts of the surface morphology of the lithium iron phosphate batteries prepared using the anode materials in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 after cycling.

[0027] Figure 5 It is the rate performance test chart of the lithium iron phosphate batteries prepared with the anode materials in Example 1, Comparative Example 1, and Comparative Example 2 at different current densities.

[0028] Figure 6 a-6d are respectively the exchange current density tests of the lithium-lithium symmetric batteries prepared using the anode materials in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Specific Embodiments

[0029] The embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application, so they are only examples and cannot be used to limit the protection scope of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above accompanying drawing descriptions are intended to cover non-exclusive inclusion.

[0031] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is more than two, unless otherwise clearly and specifically defined.

[0032] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appearing in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0033] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0034] In the description of the embodiments of the present application, the term "a plurality of" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces).

[0035] In existing negative electrode materials for lithium-copper batteries, the main strategies adopted include physical modification and chemical modification. For example, by coating materials such as carbon nanotubes and graphene on the copper substrate to improve its electrical conductivity and interface stability; or using methods such as nickel plating and silver plating to increase the uniformity of lithium deposition. However, although these modification methods have improved the performance of the negative electrode material to a certain extent, there are still some problems. For example, the stability of the physical coating layer is poor and it is easy to fall off during the charge and discharge process; the chemical coating may increase the interface impedance due to incompatibility with lithium metal. In addition, these modification methods are often complex in process and high in cost, which is not conducive to large-scale production and practical application.

[0036] To solve the technical problems that the physical coating layer on the copper foil substrate has poor stability and is prone to peeling off during charge and discharge, and the chemical coating may increase the interfacial impedance due to incompatibility with lithium metal, the present application can enhance the deposition uniformity and structural stability of lithium metal by introducing a lithium alloy layer on the copper foil. In the copper foil-lithium alloy layer integrated structure, there is a large electron cloud around the lithiumophilic metal atoms in the lithium alloy layer, which can combine with the deposited lithium metal to form an alloy during the charge and discharge cycle, enabling the deposition of lithium metal to grow along the plane direction of the lithium alloy layer, effectively inhibiting the growth of lithium dendrites; lithiumophilic metals are introduced into the lithium alloy layer, and the binding forces between these lithiumophilic metals such as silver, zinc, tin, aluminum, and magnesium and lithium and copper are very strong. Therefore, the lithiumophilic metals can also enhance the bonding degree between metallic lithium and the copper foil, reduce the interfacial impedance between the lithium negative electrode and the copper foil, facilitate the transmission of electrons, provide higher conductivity and stronger interfacial binding force, and enhance the structural stability of the negative electrode material. At the same time, the present application modifies a carbon layer composed of heat-reduced carbon materials on the surface of the lithium alloy layer. The heat-reduced carbon materials have carbon defect sites and vacancies, and the energy barriers at the carbon defect sites and vacancies are low. The lithiumophilic elements in the lithium alloy can provide more electron clouds to interact with the defect sites with low energy barriers to form fast channels, thereby promoting the movement of lithium ions along the defect sites, increasing the adsorption and diffusion rate of lithium ions on the surface, and improving the electrochemical reactivity of lithium ions. By coating the lithium alloy layer and the carbon layer on the surface of the copper foil, the present application increases the lithium ion transmission path, regulates the lithium ion insertion / extraction kinetics, reduces the energy barrier, improves the high-rate discharge performance, and enhances the stability of the battery during fast charge and discharge.

[0037] In a first aspect, an embodiment of the present application provides a lithium-copper integrated composite negative electrode material, including a copper foil, a lithium alloy layer, and a carbon layer stacked in sequence. The lithium alloy layer includes lithium metal and lithiumophilic metal, and the lithiumophilic metal includes at least one of silver, zinc, tin, aluminum, and magnesium. The carbon layer is made of heat-reduced carbon materials.

[0038] In some embodiments, the carbon materials include at least one of graphene, carbon nanotubes, carbon spheres, and activated carbon.

[0039] In some embodiments, the mass ratio of the lithiumophilic metal to the lithium metal is 1:(5~10).

[0040] In some embodiments, the thickness ratio of the copper foil, the lithium alloy layer, and the carbon layer is (5~20):(10~100):(1~5).

[0041] In a second aspect, an embodiment of the present application provides a preparation method of a lithium-copper integrated composite negative electrode material, including the following steps: S1. Heat and melt the lithium metal and the lithiumophilic metal, then coat them on the copper foil, and obtain a copper foil-lithium alloy layer after cooling; S2. After thermally reducing the carbon material, disperse it in a solvent to obtain a dispersion, drop the dispersion onto the surface of the copper foil - alloy layer, heat and dry it to obtain the lithium - copper integrated composite anode material.

[0042] In some embodiments, in step S1, the temperature for heating and melting is 250°C to 400°C, and the heating time is 10 to 30 minutes.

[0043] In some embodiments, the thermal reduction conditions of the carbon material in step S2 are: thermal reduction is carried out under the protection of an inert gas, the thermal reduction temperature is 500°C to 1000°C, and the thermal reduction time is 0.5 to 5 hours.

[0044] In some embodiments, the solvent in step S2 is at least one of tetrahydrofuran, N,N - dimethylformamide, N,N - dimethylacetamide, dimethyl sulfoxide, and N - methylpyrrolidone.

[0045] In some embodiments, the concentration of the dispersion is 0.1 to 1 mg / mL.

[0046] In a third aspect, an embodiment of the present application provides a lithium metal battery, including the above - mentioned lithium - copper integrated composite anode material.

[0047] The following lists some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those embodiments where specific technologies or conditions are not indicated, the technologies or conditions described in the literature in the art or according to the product specifications are followed. For reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained through commercial purchase.

[0048] I. Preparation method Example 1 The preparation and application of a lithium - copper integrated composite anode material include the following steps: 1) Weigh 5 g of graphene material, heat it to 800 °C in a tubular furnace under argon protection, and after keeping it warm for 1 h, naturally cool it to room temperature for standby.

[0049] 2) Weigh 5 g of lithium metal strip and 0.5 g of metal tin powder in a drying room with a dew point lower than - 45°C.

[0050] 3) Place the lithium metal and tin powder weighed in step 1) in an iron crucible and place it in a muffle furnace to heat to 300°C until molten, then take out the crucible and coat it on the copper foil, and naturally cool it to room temperature.

[0051] 4) Weigh a certain amount of graphene in step 1 and disperse it in a tetrahydrofuran solution to form a uniform dispersion with a concentration of 0.2 mg / mL. Subsequently, drop the dispersion onto the surface of the negative electrode obtained in step 2) and heat it at 50 °C for 2 h until the solution is dried to form the negative electrode material.

[0052] Example 2 Preparation and application of a lithium-copper integrated composite negative electrode material, including the following steps: 1) Weigh 3 g of carbon sphere material, heat it to 800 °C in a tubular furnace under argon protection, and after holding for 3 h, naturally cool it to room temperature for standby.

[0053] 2) Weigh 5 g of lithium metal strip and 0.8 g of silver metal powder in a drying room with a dew point lower than -45 °C.

[0054] 3) Place the weighed lithium metal and silver powder in step 1) in an iron crucible and place it in a muffle furnace to heat to 350 °C until molten. Then take out the crucible and coat it on a copper foil, and naturally cool it to room temperature.

[0055] 4) Weigh a certain amount of carbon spheres in step 1 and disperse them in an N,N-dimethylacetamide solution to form a uniform dispersion with a concentration of 0.1 mg / mL. Subsequently, drop the dispersion onto the surface of the negative electrode obtained in step 2) and heat it at 60 °C for 12 h until the solution is dried to form the negative electrode material.

[0056] Example 3 Preparation and application of a lithium-copper integrated composite negative electrode material, including the following steps: 1) Weigh 1 g of carbon nanotube material, heat it to 800 °C in a tubular furnace under argon protection, and after holding for 2 h, naturally cool it to room temperature for standby.

[0057] 2) Weigh 5 g of lithium metal strip and 1 g of magnesium metal powder in a drying room with a dew point lower than -45 °C.

[0058] 3) Place the weighed lithium metal and magnesium powder in step 1) in an iron crucible and place it in a muffle furnace to heat to 250 °C until molten. Then take out the crucible and coat it on a copper foil, and naturally cool it to room temperature.

[0059] 4) Weigh a certain amount of carbon nanotubes in step 1 and disperse them in an N,N-dimethylformamide solution to form a uniform dispersion with a concentration of 0.5 mg / mL. Subsequently, drop the dispersion onto the surface of the negative electrode obtained in step 2) and heat it at 80 °C for 6 h until the solution is dried to form the negative electrode material.

[0060] Example 4 Preparation and application of a lithium-copper integrated composite negative electrode material, including the following steps: 1) Weigh 1 g of activated carbon material and heat it to 800 °C in a tube furnace under argon protection. After holding for 2 h, cool it naturally to room temperature for standby.

[0061] 2) Weigh 5 g of lithium metal strip and 0.7 g of zinc metal powder in a drying room with a dew point below -45 °C.

[0062] 3) Place the lithium metal and zinc powder weighed in step 1) in an iron crucible and heat it to 300 °C in a muffle furnace until it melts. Then take out the crucible, coat it on a copper foil, and cool it naturally to room temperature.

[0063] 4) Weigh a certain amount of the activated carbon material in step 1) and disperse it in dimethyl sulfoxide solution to form a uniform dispersion with a concentration of 0.8 mg / mL. Then drop the dispersion onto the surface of the negative electrode obtained in step 2), and heat it at 70 °C for 10 h until the solution is dried to form the negative electrode material.

[0064] Comparative Example 1 Comparative Example 1 is a commercial lithium strip without any treatment.

[0065] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the carbon material is not subjected to thermal reduction treatment.

[0066] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that there is no carbon layer on the surface of the lithium alloy layer.

[0067] II. Test Methods For the batteries in the following test methods, CR2032 battery cases are used, the electrolyte is a conventional commercial electrolyte, and the separator is a conventional commercial separator.

[0068] 1. Symmetric battery rate performance test method Assemble a symmetric battery to test the charge-discharge performance of the prepared negative electrode material at different current densities, where the current densities are set to 0.1, 0.2, 0.3, 0.5, 0.8, 1 mA cm -2 , and cycle 10 times at each current density.

[0069] 2. Symmetric battery cycle performance test method Assemble a symmetric battery to test the charge-discharge performance of the prepared negative electrode material at a certain current density, where the current density is set to 0.5 mA cm -2 , and the deposition amount is set to 0.5 mAh cm -2 .

[0070] 3. Lithium iron phosphate full battery performance test method The lithium iron phosphate button battery was assembled with a commercial lithium iron phosphate electrode and the anode material prepared by this solution, and the specific capacity retention rate of the battery was tested at the current densities of 0.2, 0.5, 1, 2, 3, 4, and 5 C respectively.

[0071] 4. Exchange current density test method The assembled symmetrical battery was placed on a CHI660 electrochemical workstation for testing. The test voltage range was -0.02V - 0.02V, and the scanning rate was 0.001V / s.

[0072] 5. Surface morphology test of the electrode after cycling The cycled battery was disassembled, and a scanning electron microscope was used to observe the degree of damage on the electrode surface.

[0073] III. Analysis of test results of each example and comparative example (1) The lithium-copper integrated composite anode material prepared in Example 1 was scanned by SEM as shown in Figure 1 It can be seen that there is a dense layer of carbon material on the anode surface.

[0074] (2) The anode materials prepared in Example 1 and Comparative Example 1 were used to assemble a lithium-lithium symmetrical battery, and the rate performance of the battery at different current densities was tested. The test results are shown in Figure 2 It can be seen that the anode material prepared in Example 1 can withstand a larger current density than that in Comparative Example 1 without short circuit.

[0075] (3) The anode materials prepared in Example 1 and Comparative Example 1 were used to assemble a lithium-lithium symmetrical battery, and the cycle performance of the battery was tested. The test results are shown in Figure 3 It can be seen that the anode material prepared in Example 1 has better stability.

[0076] (4) Figure 4 a - 4d are the scanning electron microscope pictures of the anode surface of the lithium iron phosphate batteries prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 after cycling. It can be seen that the dendritic layers on the anode surfaces in Comparative Examples 1 - 3 are severely damaged, and Example 1 has the flattest surface morphology, with no particles or dendrites on the surface, indicating that the anode prepared in Example 1 can well inhibit the growth of lithium dendrites.

[0077] (5) Figure 5 The specific capacity retention rates of the lithium iron phosphate batteries prepared with the anode materials in Example 1, Comparative Example 1, and Comparative Example 2 at different current densities are shown. It can be seen that the anode material prepared in Example 1 still has a high specific capacity at a current density of 1C, which can well match the use of commercial lithium iron phosphate batteries. The specific capacities of the batteries prepared with the anode materials in Comparative Example 2 and Comparative Example 2 decrease significantly in the later stage of cycling.

[0078] (6) Figure 6 a to 6d are the test of the exchange current density of the symmetric batteries prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 respectively. It can be seen that Example 1 has the largest exchange current density, indicating that the battery prepared in Example 1 has better surface kinetic performance.

[0079] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and the embodiments with the same structure and the same effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope not departing from the gist of this application, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A lithium-copper integrated composite negative electrode material, characterized in that: It includes a copper foil, a lithium alloy layer and a carbon layer stacked in sequence, the lithium alloy layer includes lithium metal and a lithium-philic metal, the lithium-philic metal includes at least one of silver, zinc, tin, aluminum and magnesium, and the carbon layer is made of a carbon material after thermal reduction treatment.

2. The lithium-copper integrated composite negative electrode material according to claim 1, characterized in that: The carbon material includes at least one of graphene, carbon nanotubes, carbon balls and activated carbon.

3. The lithium-copper integrated composite negative electrode material according to claim 1, characterized in that: The mass ratio of the lithium-philic metal to the lithium metal is 1:(5-10).

4. The lithium-copper integrated composite negative electrode material according to claim 1, characterized in that: The thickness ratio of the copper foil, the lithium alloy layer and the carbon layer is (5-20):(10-100):(1-5).

5. A method for preparing a lithium-copper integrated composite negative electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, heating and melting the lithium metal and the lithium-philic metal, and then coating them on a copper foil, and cooling them to obtain a copper foil-lithium alloy layer; S2. After thermally reducing the carbon material, disperse it in a solvent to obtain a dispersion, drop the dispersion on the surface of the copper foil-alloy layer, heat and dry it to obtain a lithium-copper integrated composite negative electrode material.

6. The method for preparing the lithium-copper integrated composite negative electrode material according to claim 5, characterized in that: The heating and melting temperature in step S1 is 250° C. to 400° C., and the heating time is 10 to 30 minutes.

7. The method for preparing the lithium-copper integrated composite negative electrode material according to claim 5, characterized in that: The thermal reduction conditions of the carbon material in step S2 are: thermal reduction is carried out under the protection of an inert gas, the thermal reduction temperature is 500° C. to 1000° C., and the thermal reduction time is 0.5 to 5 hours.

8. The method for preparing the lithium-copper integrated composite negative electrode material according to claim 5, characterized in that: The solvent in step S2 is at least one of tetrahydrofuran, N,N-dimethylformamide, N,N,-dimethylacetamide, dimethyl sulfoxide and N,N-methylpyrrolidone.

9. The method for preparing the lithium-copper integrated composite negative electrode material according to claim 5, characterized in that: It is characterized in that The concentration of the dispersion is 0.1-1 mg / mL.

10. A lithium metal battery, characterized in that: A lithium-copper integrated composite negative electrode material comprising any one of claims 1 to 4.

Images