Lithium-carbon composite material as well as preparation method and application thereof

Abstract

The invention discloses a lithium-carbon composite material as well as a preparation method and application thereof. According to the lithium-carbon composite material, metal lithium powder and / or lithium alloy powder are / is used as an inner core, a single-wall carbon nanotube and a multi-wall carbon nanotube are jointly used as an outer shell, and the lithium-carbon composite material of a core-shell structure is constructed. The flexibility of the single-walled carbon nanotubes and the rigidity of the multi-walled carbon nanotubes are utilized to construct a rigid-flexible stable shell, so that the problem of volume expansion of metal lithium in the charging and discharging process is relieved; besides, the shell can conduct electrons and ions at the same time and synchronously regulate and control lithium ion transmission and current density, so that the problem of non-uniform deposition of metal lithium is effectively solved, and growth of lithium dendrites is avoided, thereby improving the safety and service life of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a lithium-carbon composite material and a preparation method and use thereof. Background Art

[0002] Lithium batteries are rechargeable secondary batteries that primarily rely on chemical reactions between positive and negative electrodes to store electrical energy. Lithium metal, as the negative electrode material for lithium batteries, has a high theoretical capacity and is considered one of the most promising high-capacity negative electrode materials. Furthermore, its low density significantly increases the energy density of lithium batteries. Consequently, lithium metal has been extensively researched.

[0003] However, in practical applications, lithium metal suffers from severe volume expansion, which can lead to structural damage to the electrode and the pulverization and shedding of lithium metal, resulting in internal short circuits in the battery and posing a safety hazard. Furthermore, the uneven deposition of lithium metal and the easy growth of lithium dendrites during charge and discharge also limit its practical application.

[0004] Currently, research on metallic lithium mainly focuses on introducing lithiophilic deposition sites and skeleton materials. For example, adding lithiophilic deposition sites such as nanosilver, nanotin, and zinc oxide can induce uniform deposition of metallic lithium, solve the problem of lithium dendrites, and introduce skeleton materials to alleviate the volume expansion problem of metallic lithium. CN112750987A discloses a method for preparing a lithium metal negative electrode with a lithiophilic three-dimensional carbon-based current collector, comprising the following steps: first, self-assembling one-dimensional nanomaterials such as silver nanowires and organic materials to obtain a three-dimensional precursor skeleton material; then, subjecting the three-dimensional precursor skeleton material to a high-temperature carbonization treatment to prepare a lithiophilic three-dimensional carbon-based current collector with good wettability for liquid metallic lithium; heating the metallic lithium to 180°C to 500°C to obtain liquid metallic lithium, mixing the liquid metallic lithium with the lithiophilic three-dimensional carbon-based current collector, and naturally cooling the mixture after the liquid metallic lithium is fully wetted to produce a composite lithium metal negative electrode. This method requires heating the metallic lithium to a molten state and cannot modify powdered lithium-containing materials such as metallic lithium powder.

[0005] Based on this, how to modify powdered lithium-containing materials such as metallic lithium powder, solve the problems of volume expansion and uneven deposition of metallic lithium, and promote the application of powdered lithium-containing materials has become an urgent problem to be solved. Summary of the Invention

[0006] To address the above technical issues, the present invention provides a lithium-carbon composite material, its preparation method, and its use. The composite material uses both single-walled carbon nanotubes and multi-walled carbon nanotubes as a shell to modify powdered lithium-containing materials such as lithium metal powder, thereby resolving the volume expansion and uneven deposition issues associated with these materials.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0008] In a first aspect, the present invention provides a lithium-carbon composite material, which includes metallic lithium powder and / or lithium alloy powder as a core, and a shell is provided on the surface of the core; the shell is composed of single-walled carbon nanotubes and multi-walled carbon nanotubes, and the mass ratio of the single-walled carbon nanotubes to the multi-walled carbon nanotubes is 1:(0.1-100).

[0009] In the present invention, single-walled carbon nanotubes and multi-walled carbon nanotubes are interwoven to form a shell, modifying the core of metallic lithium powder and / or lithium alloy powder. The flexibility of the single-walled carbon nanotubes is used to construct the shell framework, and the multi-walled carbon nanotubes are fixed in the shell. The rigidity of the multi-walled carbon nanotubes is used to enhance the rigidity of the shell. The two cooperate to construct a stable, porous shell that is both rigid and flexible, providing space for the volume expansion of the core. In addition, the shell has good electronic conductivity and ion transport capabilities, regulating the uniform deposition of metallic lithium, solving the problem of uneven metallic lithium deposition and the generation of lithium dendrites, and endowing the lithium-carbon material with good cycle performance and safety performance.

[0010] In the present invention, the shell constructed by single-walled carbon nanotubes and multi-walled carbon nanotubes in a specific mass ratio is relatively stable, so that the lithium-carbon composite material has good cycle performance. The mass ratio of the single-walled carbon nanotubes and multi-walled carbon nanotubes can be 1:0.1, 1:0.3, 1:0.5, 1:0.8, 1:1, 1:2.5, 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:75, 1:90 or 1:100, etc., including but not limited to the listed point values. If the mass ratio is too large, there are more single-walled carbon nanotubes, the rigidity of the shell is weak, and the structure is unstable; if the mass ratio is too small, there are more multi-walled carbon nanotubes, and the framework of the shell cannot be constructed, making it difficult to form a stable shell on the surface of the core.

[0011] Optionally, the average particle size of the metallic lithium powder and / or lithium alloy powder is 1-100 μm, preferably 10-50 μm.

[0012] Optionally, the alloying elements in the lithium alloy powder include at least one of tin, gold, barium, bismuth, calcium, germanium, platinum, lead, antimony, silver, boron, magnesium, indium, gallium, aluminum, or zinc. During lithium extraction from the lithium-carbon composite material, the alloying elements remain in place and do not participate, thereby improving the stability of the core. The alloying elements have an affinity for lithium and can regulate the uniform deposition of metallic lithium during deposition.

[0013] Optionally, the length of the single-walled carbon nanotubes is 0.5 μm to 50 μm, preferably 1-20 μm. If the length of the single-walled carbon nanotubes is too small, a stable framework cannot be formed. If the length of the single-walled carbon nanotubes is too large, aggregation is likely to occur. The outer diameter of the single-walled carbon nanotubes is 1-2 nm.

[0014] Optionally, the number of layers of the multi-walled carbon nanolayer is greater than or equal to 2 and less than or equal to 15, preferably 2-10 layers.

[0015] Optionally, the outer diameter of the multi-walled carbon nanotubes is less than 30 nm, preferably 4-20 nm.

[0016] Optionally, the length of the multi-walled carbon nanotubes is 0.5-50 μm.

[0017] Optionally, the length of the multi-walled carbon nanotube is less than or equal to that of the single-walled carbon nanotube.

[0018] As a preferred technical solution of the present invention, the multi-walled carbon nanotubes have a modified layer containing a lithium-phobic element, and the lithium-phobic element in the modified layer includes at least one of copper, nickel, titanium, chromium, vanadium, cobalt, manganese or iron. In the prior art, the regulation of the deposition of metallic lithium is concentrated on the deposition site introducing lithium affinity, and in the present invention, the inventors found during the experiment that the use of multi-walled carbon nanotubes containing a lithium-phobic element modified layer (such as the related materials sold by Beijing Dekedao Gold Technology Co., Ltd.) can also achieve the regulation of metallic lithium deposition. The reason is speculated to be: the uneven deposition of metallic lithium is caused by the uneven current density on the surface of the material. Although the lithium-phobic element modified layer cannot induce the uniform deposition of metallic lithium, it has good electronic conductivity, so that the current density on the surface of the material is more uniform, thereby solving the problem of uneven deposition of metallic lithium and the generation and growth of lithium dendrites.

[0019] Optionally, based on the mass of the multi-walled carbon nanotubes being 100%, the mass content of the lithium-phobic element is greater than 50%, preferably 60-80%. A lower mass content may limit the uniform deposition of metallic lithium, while a higher mass content may result in a lower gram capacity of the lithium-carbon composite.

[0020] Optionally, the shell has a thickness between 0.5 μm and 50 μm. If the thickness is too thick, the metallic lithium content is low and the specific capacity of the lithium-carbon composite material is low; if the thickness is too thin, the effect of alleviating the volume expansion of the core is limited.

[0021] Optionally, the mass ratio of the single-walled carbon nanotubes to the multi-walled carbon nanotubes is 1:(0.5-50), preferably 1:(1-30). The thickness of the shell can be adjusted according to the change of the mass ratio, thereby achieving effective control of ions and electrons.

[0022] Optionally, based on the mass of the lithium-carbon composite material being 100%, the mass fraction of the core in the lithium-carbon composite material is greater than 50%, preferably greater than 70%, and more preferably greater than 85%.

[0023] In a second aspect, the present invention provides a method for preparing the lithium-carbon composite material as described in the first aspect, the preparation method comprising the following steps:

[0024] (1) dispersing single-walled carbon nanotubes and multi-walled carbon nanotubes in an organic solvent to obtain a first dispersed system;

[0025] (2) mixing metallic lithium powder and / or lithium alloy powder with the first dispersion system of step (1) to obtain a second dispersion system;

[0026] (3) spray drying the second dispersed system to obtain the lithium-carbon composite material;

[0027] Alternatively, after high-speed stirring (rotation speed above 5000 rpm), the organic solvent is removed to obtain the lithium-carbon composite material; the organic solvent is inert to metallic lithium powder and / or lithium alloy powder.

[0028] In the present invention, the organic solvent is not specifically limited, as long as it is inert to the lithium metal powder and / or lithium alloy powder, does not undergo violent chemical reactions, and can be used as a solvent. For example, it can be any one of liquid alkanes having 4 to 20 carbon atoms, liquid halogenated hydrocarbons having 4 to 20 carbon atoms, toluene, xylene, liquid paraffin, tetrahydrofuran, N,N-dimethylformamide, or silicone oil, or a combination of at least two thereof.

[0029] Optionally, step (1) includes the following operations: (a) pre-dispersing the single-walled carbon nanotubes in an organic solvent, and then adding the multi-walled carbon nanotubes and mixing to obtain a first dispersion system. Pre-dispersing the single-walled carbon nanotubes allows the single-walled carbon nanotubes to be more evenly dispersed, thereby better forming a stable shell with the multi-walled carbon nanotubes.

[0030] Optionally, the mixing method in step (2) includes at least one of mechanical stirring, ultrasonic dispersion or high-speed stirring at a rotation speed of 5000 rpm or above.

[0031] In a third aspect, the present invention provides an electrode comprising the lithium-carbon composite material as described in the first aspect. The electrode may be an electrode made of a pure lithium-carbon composite material, or a composite electrode comprising a lithium-carbon composite material and graphite or a silicon-based material. The electrode may be a unipolar electrode (the polarity of the active materials on both sides of the current collector is the same) or a bipolar electrode (the polarity of the active materials on both sides of the current collector is opposite).

[0032] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0033] 1. A core-shell lithium-carbon composite material is constructed by using metallic lithium powder and / or lithium alloy powder as the core and single-walled carbon nanotubes and multi-walled carbon nanotubes as the shell. The flexibility of single-walled carbon nanotubes and the rigidity of multi-walled carbon nanotubes are utilized to construct a stable shell structure, thereby reducing the volume expansion problem of metallic lithium during charging and discharging.

[0034] 2. The shell can conduct electrons and ions at the same time, regulate lithium ion transmission and current density, effectively solve the problem of uneven deposition of metallic lithium, avoid the growth of lithium dendrites, and thus improve the safety and service life of the battery;

[0035] 3. In the lithium-carbon material, the single-walled carbon nanotubes and multi-walled carbon nanotubes at a specific mass ratio cooperate with each other to construct a shell with good stability. The cyclic stability of the lithium-carbon composite material is better than that of the lithium-carbon material prepared from single-walled carbon nanotubes or multi-walled carbon nanotubes;

[0036] 4. Further, by introducing multi-walled carbon nanotubes containing a lithium-phobic element modified layer into the outer shell, the uniform deposition of metallic lithium is achieved by regulating the current density, achieving the same or similar effect as in the prior art, and solving the problem of lithium dendrite generation and growth. Therefore, the present invention provides a new idea for regulating the uniform deposition of metallic lithium. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the cross-sectional structure of a lithium-carbon composite material provided by the present invention;

[0038] Figure 2 Symmetrical battery test curves of Examples 2 and 3, and Examples 4 and 5;

[0039] Figure 3 These are the symmetrical battery test curves of Example 2, Example 8, and Example 11;

[0040] Figure 4 Symmetrical battery test curves of Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 5;

[0041] Figure 5 These are the symmetrical battery test curves of Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5.

[0042] Note: Some discontinuous areas in the test curve are caused by different sampling parameter settings of the test equipment. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the examples. The following examples are only used to explain the principles of the present invention and are not to be construed as limiting the present invention.

[0044] For example, the present invention provides a lithium-carbon composite material, the cross-sectional structure diagram of the lithium-carbon composite material is as follows: Figure 1 The lithium-carbon composite material comprises a core of metallic lithium powder and / or lithium alloy powder, with an outer shell disposed on the surface of the core; the outer shell is composed of single-walled carbon nanotubes and multi-walled carbon nanotubes. The flexibility of the single-walled carbon nanotubes is used to construct the outer shell framework, while the multi-walled carbon nanotubes are fixed within the outer shell. The rigidity of the multi-walled carbon nanotubes is utilized to enhance the rigidity of the outer shell. The two interact to create a stable, porous outer shell that is both rigid and flexible.

[0045] Example 1

[0046] This embodiment provides a lithium-carbon composite material, comprising metallic lithium powder, a shell composed of single-walled carbon nanotubes and multi-walled nanotubes in a mass ratio of 1:0.1 provided on the surface of the metallic lithium powder, the shell having a thickness of 45 μm, and a mass fraction of the metallic lithium powder of 50%;

[0047] The preparation method of the lithium-carbon composite material comprises the following steps:

[0048] (1) 10 g of single-walled carbon nanotubes (Article No. 104477, outer diameter 1-2 nm, length 5-30 μm, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and 1 g of multi-walled carbon nanotubes (GT-400, outer diameter 20-30 nm, length 3-12 μm, Shandong Dazhan Nanomaterial Co., Ltd.) were added to 100 L of liquid paraffin, ultrasonicated, and mixed uniformly to obtain a first dispersion system;

[0049] (2) adding 11 g of metallic lithium powder having an average particle size of 10 μm to the first dispersion system and mixing at a rotation speed of 7000 rpm for 20 min to obtain a second dispersion system;

[0050] (3) The second dispersed system is filtered to remove the liquid paraffin, and then dried at 110° C. under vacuum conditions for 24 hours to obtain the lithium-carbon composite material.

[0051] Example 2

[0052] This embodiment provides a lithium-carbon composite material, comprising metallic lithium powder, a shell composed of single-walled carbon nanotubes and multi-walled nanotubes in a mass ratio of 1:100 provided on the surface of the metallic lithium powder, the shell having a thickness of 5 μm, and a mass fraction of the metallic lithium powder of 95%;

[0053] The preparation method of the lithium-carbon composite material comprises the following steps:

[0054] (1) 0.1 g of single-walled carbon nanotubes (Article No. 104477, outer diameter 1-2 nm, length 5-30 μm, Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.) and 10 g of multi-walled carbon nanotubes (GT-400, outer diameter 20-30 nm, length 3-12 μm, Shandong Dazhan Nanomaterial Co., Ltd.) were added to 120 L of p-xylene and dispersed at a speed of 8000 rpm. The mixture was mixed uniformly to obtain a first dispersion system;

[0055] (2) adding 20.2 g of metallic lithium powder having an average particle size of 50 μm to the first dispersion system and mechanically stirring the mixture at a speed of 3000 rpm for 90 min to obtain a second dispersion system;

[0056] (3) The second dispersed system was spray-dried with an air inlet temperature of 220° C., an air outlet temperature of 90° C., an atomization pressure of 1.2 MPa, and an injection volume of 200 mL / min to obtain the lithium-carbon composite material.

[0057] Example 3

[0058] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes to multi-walled carbon nanotubes is replaced with 1:0.5, and the other conditions are the same.

[0059] Example 4

[0060] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes to multi-walled carbon nanotubes is replaced with 1:30, and the other conditions are the same.

[0061] Example 5

[0062] Compared with Example 2, the only difference is that the mass ratio of single-walled carbon nanotubes to multi-walled carbon nanotubes is changed to 1:50, and the other conditions are the same.

[0063] Example 6

[0064] Compared with Example 2, the only difference is that the multi-walled carbon nanotubes are replaced with copper-plated multi-walled carbon nanotubes (Beijing Dekedaojin Technology Co., Ltd., CNT813, copper content of 60% by mass, outer diameter 8-15 nm, length 50 μm), and the other conditions are the same.

[0065] Example 7

[0066] Compared with Example 2, the only difference is that the multi-walled carbon nanotubes are replaced with nickel-plated multi-walled carbon nanotubes (Beike Nano, HQNANO-CNTs-009-6A, nickel content greater than 60% by mass, outer diameter 8-15 nm, length 50 μm), and the other conditions are the same.

[0067] Example 8

[0068] Compared with Example 2, the only difference is that the metallic lithium powder is replaced by lithium-boron alloy powder (the mass fraction of boron is 1 wt%), and the other conditions are the same.

[0069] Example 9

[0070] Compared with Example 2, the only difference is that the metallic lithium powder is replaced with lithium-boron-silver alloy powder (the mass fraction of boron is 1 wt %, and the mass fraction of silver is 4%), and the other conditions are the same.

[0071] Example 10

[0072] Compared with Example 2, the only difference is that the length of the multi-walled carbon nanotubes is replaced with 50 μm, and the other conditions are the same.

[0073] Example 11

[0074] Compared with Example 8, the only difference is that the multi-walled carbon nanotubes are replaced with nickel-plated multi-walled carbon nanotubes (Beike Nano, HQNANO-CNTs-009-6A, nickel content greater than 60% by mass, outer diameter 8-15 nm, length 50 μm), and the other conditions are the same.

[0075] Comparative Example 1

[0076] Compared with Example 2, the only difference is that the shell is composed of only single-walled carbon nanotubes and does not contain multi-walled carbon nanotubes.

[0077] Comparative Example 2

[0078] Compared with Example 2, the only difference is that the shell consists only of multi-walled carbon nanotubes and does not contain single-walled carbon nanotubes.

[0079] Comparative Example 3

[0080] Compared with Example 2, the only difference is that the shell is composed of conductive graphite (KS-6) and multi-walled carbon nanotubes, and does not contain single-walled carbon nanotubes.

[0081] Comparative Example 4

[0082] Compared with Example 2, the only difference is that the shell is composed of single-walled carbon nanotubes and graphene (Shenzhen Turing New Materials Co., Ltd., TA-001A, D50 is 5-8 μm), and does not contain multi-walled carbon nanotubes.

[0083] Comparative Example 5

[0084] Compared with Example 2, the only difference is that the lithium-carbon composite material does not include a shell, but only contains metallic lithium powder.

[0085] Testing of lithium-carbon composite material performance:

[0086] The lithium-carbon composite materials in Examples 1-11 and Comparative Examples 1-5 were pressed onto copper foam to make electrodes, and then assembled into symmetrical cells. The electrolyte was 1M LiTFSI (lithium bis(trifluoromethylsulfonyl)imide) DOL (1,3-dioxolane) / DME (ethylene glycol dimethyl ether) (volume ratio of 1:1), and the cycling performance was tested. At 2 mA / cm 2 and 1mAh / cm 2 Under the conditions of , the test results are shown in Table 1. The test cutoff condition is that the overpotential exceeds 1V or a short circuit occurs.

[0087] Table 1

[0088] Sources Number of cycles Example 1 709 Example 2 520 Example 3 602 Example 4 750 Example 5 675 Example 6 716 Example 7 773 Example 8 880 Example 9 896 Example 10 486 Example 11 924 Comparative Example 1 337 Comparative Example 2 249 Comparative Example 3 298 Comparative Example 4 394 Comparative Example 5 205

[0089] From Table 1 we can see that:

[0090] (1) The cycle performance of the lithium-carbon composite material in Example 2 is poorer than that in Examples 3-5 (test curves as shown in FIG. Figure 2 As shown, a short circuit occurred in Example 5). This is because the mass content of the single-walled carbon nanotubes in Example 2 is lower than that in Examples 3-5, the stability of the shell in the lithium-carbon composite material is poor, and the regulation of the volume expansion and uneven deposition of metallic lithium during the cycle is limited;

[0091] (2) The cycle performance of the lithium-carbon composite material of Examples 6-7 is better than that of Example 2. This is because the shell of the lithium-carbon composite material in Examples 6-7 adopts multi-walled carbon nanotubes containing a lithium-phobic element modification layer, which has both the rigidity of the multi-walled carbon nanotubes (which does not contain a lithium-phobic element modification layer in Example 2) and can stabilize the shell structure, and the lithium-phobic element modification layer can regulate the uniformity of the surface current density, thereby solving the problem of uneven deposition of metallic lithium and the generation and growth of lithium dendrites.

[0092] (3) The cycle performance of the lithium-carbon composite materials of Examples 8 and 9 is better than that of Example 2. This is because the core of Examples 8 and 9 is lithium alloy powder. When the metallic lithium is stripped, the alloy elements do not participate in the lithium extraction and remain in place, playing a role in stabilizing the core; when the metallic lithium is deposited, the alloy elements have an affinity for lithium and regulate the uniform deposition of the metallic lithium;

[0093] (4) The cycling performance of the lithium-carbon composite material of Example 10 is worse than that of Example 2. This is because the length of the multi-walled carbon nanotubes in Example 10 is longer than that of the single-walled carbon nanotubes. When constructing the shell, the flexible single-walled carbon nanotubes easily form a framework, while the longer rigid multi-walled carbon nanotubes are not easily fixed and are unevenly distributed, which is detrimental to the stability of the shell.

[0094] (5) The cycle performance of the lithium-carbon composite material of Example 11 is better than that of Example 8 and Example 2 (test curve as shown in FIG. Figure 3As shown, a short circuit occurs in Example 8). This is because the core of Example 11 is lithium alloy powder, which induces the inward deposition of metallic lithium, and the outer shell contains multi-walled carbon nanotubes with a lithium-repellent element modified layer, which is not affinity for metallic lithium, regulates the inward transmission of lithium ions and simultaneously regulates the uniformity of the current density on the surface. The two cooperate with each other to jointly regulate the deposition of metallic lithium;

[0095] (6) The cycle performance of the lithium-carbon composite material of Example 2 is better than that of Comparative Examples 1-5 (test curves as shown in FIG. Figure 4 and Figure 5 As shown, short circuit occurs in Comparative Example 2), this is because the shell of the lithium-carbon composite material in Comparative Example 1 is composed only of single-walled carbon nanotubes with good flexibility, and the shell stability is limited; the shell of the lithium-carbon composite material in Comparative Example 2 is composed only of multi-walled carbon nanotubes, which are relatively rigid, and the shell is not easy to form or has poor stability, which can easily cause a short circuit; the shells of the lithium-carbon composite materials in Comparative Examples 3 and 4 do not contain both single-walled carbon nanotubes and multi-walled carbon nanotubes, and the structural stability of the shells is poor; therefore, the shells of the lithium-carbon composite materials in Comparative Examples 1-4 have limited effect on solving the volume expansion and uneven deposition problems of metallic lithium; in Comparative Example 5, there is only metallic lithium powder, and no shell to modify it, which characterizes the performance of the metallic lithium powder itself.

Claims

1. A lithium-carbon composite material, characterized in that: The lithium-carbon composite material includes metallic lithium powder and / or lithium alloy powder as a core, and a shell is provided on the surface of the core; the shell is composed of single-walled carbon nanotubes and multi-walled carbon nanotubes, and the mass ratio of the single-walled carbon nanotubes to the multi-walled carbon nanotubes is 1:(0.1-100).

2. The lithium-carbon composite material according to claim 1, wherein: The average particle size of the metallic lithium powder and / or lithium alloy powder is 1-100 μm, preferably 10-50 μm.

3. The lithium-carbon composite material according to claim 1 or 2, characterized in that: The alloying elements in the lithium alloy powder include at least one of tin, gold, barium, bismuth, calcium, germanium, platinum, lead, antimony, silver, boron, magnesium, indium, gallium, aluminum or zinc.

4. The lithium-carbon composite material according to any one of claims 1 to 3, characterized in that: The length of the single-walled carbon nanotubes is 0.5 μm to 50 μm, preferably 1-20 μm.

5. The lithium-carbon composite material according to any one of claims 1 to 4, characterized in that: The number of layers of the multi-walled carbon nanolayer is greater than or equal to 2 and less than or equal to 15, preferably 2-10; Preferably, the outer diameter of the multi-walled carbon nanotubes is less than 30 nm, preferably 4-20 nm; Preferably, the length of the multi-walled carbon nanotubes is 0.5-50 μm; Preferably, the length of the multi-walled carbon nanotube is less than or equal to the length of the single-walled carbon nanotube.

6. The lithium-carbon composite material according to any one of claims 1 to 5, characterized in that: The multi-walled carbon nanotubes have a modified layer containing a lithium-phobic element, wherein the lithium-phobic element includes at least one of copper, nickel, titanium, chromium, vanadium, cobalt, manganese or iron; Preferably, based on the mass of the multi-walled carbon nanotubes being 100%, the mass content of the modified layer is above 50%, preferably 60-80%.

7. The lithium-carbon composite material according to any one of claims 1 to 6, characterized in that: The thickness of the shell is between 0.5 μm and 50 μm.

8. The lithium-carbon composite material according to any one of claims 1 to 7, characterized in that: The mass ratio of the single-walled carbon nanotubes to the multi-walled carbon nanotubes is 1:(0.5-50), preferably 1:(1-30); Preferably, based on the mass of the lithium-carbon composite material being 100%, the mass fraction of the core in the lithium-carbon composite material is 50% or more, preferably 70% or more, and more preferably 85% or more.

9. A method for preparing the lithium-carbon composite material according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: (1) dispersing single-walled carbon nanotubes and multi-walled carbon nanotubes in an organic solvent to obtain a first dispersed system; (2) mixing metallic lithium powder and / or lithium alloy powder with the first dispersion system of step (1) to obtain a second dispersion system; (3) spray drying the second dispersed system to obtain the lithium-carbon composite material; or after high-speed stirring at a rotation speed of 5000 rpm or more, removing the organic solvent to obtain the lithium-carbon composite material; the organic solvent is inert to the metallic lithium powder and / or lithium alloy powder; Preferably, the step (1) comprises the following operations: (a) pre-dispersing single-walled carbon nanotubes in an organic solvent, and then adding multi-walled carbon nanotubes and mixing to obtain a first dispersed system; Preferably, the mixing in step (2) comprises at least one of mechanical stirring, ultrasonic dispersion or high-speed mixing at a rotation speed of 5000 rpm or above.

10. An electrode, characterized in that: The electrode comprises the lithium-carbon composite material according to any one of claims 1 to 8; Preferably, the electrodes comprise bipolar electrodes.

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