Composite metal lithium electrode with three-dimensional lithium conduction path as well as preparation method and application of composite metal lithium electrode

Abstract

The invention discloses a composite metal lithium electrode with a three-dimensional lithium conduction path as well as a preparation method and application of the composite metal lithium electrode. The preparation method of the composite metal lithium electrode with the three-dimensional lithium conduction path comprises the following steps: pretreating the carbon fiber cloth; preparing a metal salt solution and an organic solution; mixing the organic solution and the metal salt solution, and stirring the carbon fiber cloth in the mixture; the carbon fiber cloth is taken out, cleaned, dried and sintered, and then a sintered product is soaked in diluted hydrochloric acid; after soaking, cleaning and drying to obtain a three-dimensional metal conductive framework material; and filling the three-dimensional metal conductive framework material with molten metal lithium to obtain the composite metal lithium electrode with a three-dimensional lithium conductive path. The preparation method is simple and easy to operate, the used raw materials are common, and the cost is low; when the material is applied to a lithium metal battery, lithium dendrite growth can be inhibited, and the cycle performance and stability of the battery are improved; the unique three-dimensional structure and good performance provide support for improvement of battery performance, and large-scale popularization and application are facilitated.

Description

Technical Field

[0001] This application belongs to the technical field of battery materials, and relates to a composite metal lithium electrode with a three-dimensional lithium conduction path, its preparation method and application. Background Art

[0002] The research and development of high-energy-density energy storage devices has become the core driving force to support the development of new energy vehicles, smart grids and portable electronic devices. Since Sony Corporation of Japan achieved a commercial breakthrough in 1991, lithium-ion batteries have successfully replaced traditional nickel-cadmium and lead-acid batteries in the past three decades with their advantages such as long cycle life and low self-discharge rate, and have built a multi-dimensional application landscape covering consumer electronics, power batteries and energy storage power stations. Data shows that the current scale of the lithium battery industry has exceeded 1.2 trillion yuan, and the installed capacity of power batteries has ranked first in the world for six consecutive years. However, as the driving range requirement of electric vehicles breaks through the 800-kilometer mark, the theoretical specific capacity ceiling (372 mAh g-1) of the existing graphite anode system has severely restricted the improvement of energy density - even the third-generation anode technology using silicon-carbon composite materials still has an actual capacity limited to the range of 450-500 mAh g-1, making it difficult to meet the advanced requirements of future energy storage technologies.

[0003] This technological dilemma has given rise to a revival boom in the lithium metal anode system. As the anode material with the best electrochemical performance in nature, lithium metal has a theoretical specific capacity as high as 3860 mAh g-1, more than 10 times higher than that of graphite materials. Combined with an ultra-low oxidation potential of -3.040 V vs. SHE, the energy density of lithium batteries can theoretically be increased to more than 500 Wh / kg. More importantly, this system can form a perfect match with high-capacity cathode materials such as sulfur and oxygen, laying a foundation for the construction of subversive battery systems such as lithium-sulfur (theoretical energy density 2600 Wh / kg) and lithium-air (theoretical energy density 3500 Wh / kg).

[0004] However, the industrialization process of this system has always been restricted by the century-old problem of lithium dendrite growth. During the cycling process, the non-uniform deposition of lithium ions on the anode surface will form a dendritic structure: on the one hand, this crystal continuously consumes active lithium, resulting in the attenuation of Coulomb efficiency (usually <99%), making it difficult for the cycle life to exceed 200 weeks; on the other hand, the dendrite tips continuously grow during charge and discharge, and may penetrate the polyolefin separator only 20-25 μm thick, triggering an internal short circuit. More seriously, the broken dendrites will react violently with the electrolyte, triggering a chain exothermic reaction above 60°C, resulting in an exponential increase in the thermal runaway risk index. Statistics show that about 73% of the safety accidents in laboratory prototype batteries equipped with metal lithium anodes are caused by internal short circuits triggered by dendrites. Summary of the Invention

[0005] Based on the above-mentioned disadvantages existing in the prior art, the purpose of this application is to provide a composite metal lithium electrode with a three-dimensional lithium conduction path, its preparation method and application. This application can effectively produce a three-dimensional metal conductive framework material with excellent lithiophilicity. This kind of conductive framework relies on a carbon nanotube substrate modified by metal cluster atoms to provide more lithiophilic sites, so as to promote the uniform deposition of lithium ions during the battery cycling process and achieve the purpose of inhibiting the growth of lithium dendrites.

[0006] This application provides the following technical solutions:

[0007] One of the technical solutions of this application provides a three-dimensional metal conductive framework material, which is represented by CC@M-NCNTs. Among them, CC is carbon fiber cloth, M represents metal nanocrystals, which are at least any one of Co, Fe, Ni, Cu, Mn or Zn, and NCNT is nitrogen-doped carbon nanotubes; this three-dimensional metal conductive framework material uses carbon fiber cloth as the matrix, and nitrogen-doped carbon nanotubes modified by metal nanocrystals are deposited on the surface.

[0008] The three-dimensional conductive framework formed by metal nanocrystal-modified nitrogen-doped carbon nanotubes provides good conditions for high-speed and uniform lithium plating, and inhibits the formation of lithium dendrites in the carbon-lithium composite electrode during repeated charge and discharge cycles.

[0009] Another technical solution of this application provides a composite metal lithium electrode with a three-dimensional lithium conduction path, which is represented by Li-CC@M-NCNTs. Among them, CC@M-NCNTs is the three-dimensional metal conductive framework material described in Technical Solution 1, and Li means that metal Li is filled on the surface of CC@M-NCNTs.

[0010] A third technical solution of this application provides a preparation method of the three-dimensional metal conductive framework material described in Technical Solution 1, including the following steps:

[0011] S1. Cut the carbon fiber cloth, soak the cut carbon fiber cloth in dilute hydrochloric acid, and perform ultrasonic treatment; after the ultrasonic treatment is completed, wash and dry the carbon fiber cloth to obtain a pretreated carbon fiber cloth for standby;

[0012] S2. Weigh metal salts, add solvents, and stir evenly to prepare a metal salt solution;

[0013] S3. Weigh 1,2-dimethylimidazole, add solvents, and stir evenly to prepare an organic solution;

[0014] S4. Place the pretreated carbon fiber cloth obtained in S1 in the organic solution prepared in step S3, and then slowly pour the metal salt solution prepared in step S2 into the organic solution and stir;

[0015] S5. Take out the carbon fiber cloth after stirring, wash and dry it;

[0016] S6. Sinter the carbon fiber cloth prepared in S5, and then immerse the sintered product in dilute hydrochloric acid; wash and dry it after immersion to obtain a three-dimensional metal conductive framework material (CC@M-NCNTs).

[0017] Further, the size of the carbon fiber cloth cut in step S1 is (10-100) cm × (1-10) cm, preferably 18 cm * 2 cm; the concentration of the dilute hydrochloric acid is 0.1-3 M, preferably 1 M; the time of the ultrasonic treatment is 0.1-10 h, preferably 0.5 h; the washing is carried out by washing with deionized water multiple times; the drying is preferably carried out by vacuum drying in a vacuum drying oven; the drying time is 8-24 h, preferably 12 h; the drying temperature is 25-100 °C, preferably 60 °C; further, the purpose of the operation in step S1 is to improve the hydrophilic ability of the carbon fiber cloth.

[0018] Further, the cation in the metal salt in step S2 is at least any one of metal cations such as Co, Fe, Ni, Cu, Mn or Zn, and the anion is any one of sulfate and nitrate. The metal salt may contain water of crystallization. The metal salt is preferably NiSO 4 ·6H 2 O, FeSO 4 ·7H 2 O, CoSO 4 ·6H 2 O, CuSO 4 ·5H 2 O, MnSO 4 ·4H 2 O or Zn(NO 3 ) 2 ·6H 2 O; the concentration of the metal cation in the metal salt solution is 0.1-1 mol / mL, preferably 0.1 mol / mL; the solvent of the metal salt solution is deionized water.

[0019] Further, the concentration of 1,2-dimethylimidazole in the organic solution in step S3 is 0.1-1 mol / mL, preferably 0.4 mol / mL; the solvent of the organic solution is deionized water.

[0020] Further, the temperature of the stirring in step S4 is 15-30 °C, and the time of the stirring is 2-12 h, preferably 4 h.

[0021] Furthermore, the cleaning in step S5 is: washing with deionized water for multiple times to clean the residual solution on it; the drying is: placing the cleaned carbon fiber in a vacuum drying oven for vacuum drying; the drying time is 8 to 24 hours, preferably 12 hours; the drying temperature is 25 to 100°C, preferably 60°C.

[0022] Furthermore, the sintering in step S6 is as follows: the carbon fibers are arranged on a reaction boat and placed in a tubular furnace for vacuum sintering; the temperature control scheme for the sintering is as follows: heating to 600°C at a heating rate of 1°C / min, and then keeping warm for 2 hours; the concentration of the dilute hydrochloric acid is 0.1-5wt.%, preferably 1wt.%; the impregnation time is 1-6h, preferably 2h; the purpose of impregnation in dilute hydrochloric acid is to remove excess metal ions.

[0023] The fourth technical solution of the present application provides a method for preparing a composite metal lithium electrode having a three-dimensional lithium conductive path as described in the second technical solution, wherein steps S1 to S6 of the preparation method are steps S1 to S6 as described in the third technical solution, and after obtaining a three-dimensional metal conductive skeleton material (CC@M-NCNTs), step S7 is performed:

[0024] S7. Cut the three-dimensional metal conductive skeleton material CC@M-NCNTs into a suitable size, and then heat the metal lithium sheet to a molten state; place the three-dimensional metal conductive skeleton material into the molten metal lithium for immersion, fill the metal lithium into the three-dimensional metal conductive skeleton material, and finally obtain the target product: a composite metal lithium electrode Li-CC@M-NCNTs with a three-dimensional lithium conductive pathway.

[0025] In some specific embodiments of the present application, the three-dimensional metal conductive skeleton material CC@M-NCNTs is cut into discs with a diameter of 12 mm; the temperature of the heated metal lithium sheet is 200-240°C to ensure that the lithium sheet can be melted; the three-dimensional metal conductive skeleton material CC@M-NCNTs is immersed in molten metal lithium for 10-30 minutes, preferably 15 minutes; this step is carried out in a glove box with an argon atmosphere to prevent the oxidation of metal lithium by water and oxygen in the air.

[0026] The fifth technical solution of the present application provides an application of a composite metal lithium electrode with a three-dimensional lithium conductive path as described in one of the above technical solutions. The composite metal lithium electrode with a three-dimensional lithium conductive path is used to prepare a lithium metal battery, which can improve the rate and cycle performance of the metal lithium battery.

[0027] Sixth, a technical solution of the present application provides a battery. The battery is a CR2025 button cell; both the positive and negative electrodes of the CR2025 button cell adopt Li-CC@M-NCNTs, the separator is Celgard 2000, the solvent component in the electrolyte is a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (v / v = 1:1), and the electrolyte component in the electrolyte is 1.0 M LiPF6 and 5 wt.% fluoroethylene carbonate (FEC).

[0028] Compared with the prior art, the present application has at least the following technical effects:

[0029] (1) The preparation method is simple and easy to operate: The preparation method of the conductive framework material provided by the present application has clear and definite steps, and only requires conventional experimental operations such as cutting, infiltration, stirring, and sintering, without complex equipment and professional skills.

[0030] (2) Improve the cycle performance and stability of the battery: When the prepared three-dimensional metal conductive framework material is applied to a lithium metal battery, it can effectively inhibit the growth of lithium dendrites. The growth of lithium dendrites will cause problems such as battery short circuit and capacity attenuation, while this material can reduce the occurrence of these situations. For example, during multiple charge and discharge processes, due to the inhibition of lithium dendrites, the internal structure of the battery is stable, resulting in improved cycle performance and enhanced cycle stability of the battery, thereby extending the service life of the battery and ensuring the reliable operation of the battery.

[0031] (3) Common raw materials with low cost: The carbon fiber cloth, analytical pure metal salts, organic salts, and dilute hydrochloric acid used in the preparation process are all common chemical materials, with wide sources and low costs. The cost can be effectively controlled during large-scale production, which is beneficial to the popularization and application of this conductive framework material.

[0032] (4) The material structure has significant performance advantages: The finally obtained three-dimensional metal conductive framework material has a unique three-dimensional structure, which provides more channels and space for the transmission of lithium ions, helping to improve the charge and discharge efficiency of the battery. At the same time, its organic metal composition endows it with good conductivity and stability, enabling it to better adapt to the electrochemical environment inside the battery, providing strong support for the improvement of the performance of lithium metal batteries, and showing more excellent performance than traditional materials. Description of the Drawings

[0033] Figure 1 It is a preparation flow chart of the CC@M-NCNTs framework material and the composite metal lithium electrode with a three-dimensional lithium conduction path of Li-CC@M-NCNTs;

[0034] Figure 2 For 1 mA·cm -2 2 mA·cm -2 and 6 mA·cm-2 Overpotential magnitudes of different electrode materials in Example 1 and Example 2 under current density;

[0035] Figure 3 The corresponding polarization voltages when the current density is gradually increased until (a) the Li-CC@Co-NCNTs symmetric cell and (b) the pure Li symmetric cell reach the critical current density (CCD);

[0036] Figure 4 Galvanostatic charge-discharge performance plots for (a) the Li-CC@Co-NCNTs symmetric cell; (b) comparison of three charge / discharge curves at different cycles marked by the box in (a); (c) galvanostatic charge-discharge performance plot for the pure Li symmetric cell.

[0037] Figure 5 High-magnification SEM images of (a) CC@Co-NCNTs; TEM images of (b) CC@Co-NCNTs; high-magnification SEM images of (c) CC@Fe-NCNTs; TEM images of (d) CC@Fe-NCNTs. Detailed implementation manners

[0038] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all fall within the protection scope of the present invention.

[0039] Example 1 Three-dimensional metal conductive framework material CC@Fe-NCNTs and the composite metal lithium electrode Li-CC@Fe-NCNTs with three-dimensional lithium conduction pathway prepared therefrom

[0040] S1. Cut the carbon fiber cloth (CC) to obtain a carbon fiber cloth with a size of 18 cm * 2 cm; place the cut carbon fiber cloth into a beaker with a capacity of 100 mL, pour 50 mL of dilute hydrochloric acid with a concentration of 1 M, place the beaker in an ultrasonic cleaner for 0.5 hours for carbon cloth infiltration operation, then wash the carbon cloth with deionized water, and place it in a vacuum drying oven for vacuum drying for 12 hours to improve the hydrophilic ability of the carbon cloth;

[0041] S2. Weigh 0.197 g of analytical pure Zn(NO 3 ) 2 ·6H 2 O and 0.367 g of analytical pure FeSO 4 ·7H 2O. Weigh the substance and place it in a beaker. Add 40 mL of deionized water and use a magnetic stirrer to stir evenly until a metal salt solution is formed.

[0042] S3. Weigh 1.3 g of 1,2 - dimethylimidazole and place it in a beaker. Pour 40 mL of deionized water into it and also stir evenly to form an organic solution.

[0043] S4. Place the carbon fiber cloth obtained after the S1 operation into the organic solution. Then slowly pour the metal salt solution into the organic solution and cooperate with a magnetic stirrer for rapid stirring. Place the stirred beaker in a normal temperature environment for 4 hours.

[0044] S5. Take out the stirred carbon fiber cloth, wash the residual solution on it with deionized water, and then place it in a vacuum drying oven for vacuum drying for 12 hours.

[0045] S6. Place the prepared carbon fiber cloth on a reaction boat, put it into a tube furnace for vacuum sintering. Then immerse the sintered product in 1 wt.% HCl for 2 h. The purpose is to remove the excess Zn metal. After washing and vacuum drying, the three - dimensional metal conductive framework material CC@Fe - NCNTs is obtained.

[0046] S7. Cut the three - dimensional metal conductive framework material CC@Fe - NCNTs into circular pieces with a diameter of 12 mm. Then use a heating stage to heat the lithium metal sheet until the lithium sheet becomes in a molten state (220 °C). Put the pre - prepared circular pieces into the liquid molten lithium for infiltration for 3 min, inject the lithium metal into the three - dimensional conductive matrix, and finally obtain the target product Li - CC@Fe - NCNTs, a composite lithium metal electrode with a three - dimensional lithium - conducting pathway. This step is carried out entirely in a glove box with an argon atmosphere to prevent the oxidation of lithium metal by water and oxygen in the air.

[0047] Figure 1 It is the preparation flow chart of the CC@M - NCNTs framework material in Example 1 (the same for Example 2). As can be seen in the figure: A deposition reaction occurs between the metal salt and dimethylimidazole on the surface of the carbon cloth. After a simple solution reaction, the surface of the carbon cloth will be covered by leaf - shaped M - ZIF (M is Ni, Fe, Co, Cu, Mn, Zn, etc.) to form the precursor M - ZIF@CC. During the vacuum sintering process of M - ZIF@CC, the leaf - shaped M - ZIF on the surface of the carbon fiber will be transformed into N - doped carbon nanotube nanosheets filled with nanosheets, and the reduced M nanocrystals are evenly distributed on the nanosheets and carbon nanotubes, that is, the M nanocrystals are anchored on the N - doped carbon nanotubes CC@M - NCNTs. Finally, the CC@M - NCNTs framework material is filled with molten lithium to obtain the Li - CC@M - NCNTs composite electrode.

[0048] Example 2 Three-dimensional metal conductive framework material CC@Co-NCNTs and composite metal lithium electrode Li-CC@Co-NCNTs with three-dimensional lithium conduction pathway prepared therefrom

[0049] S1. Cut the carbon fiber cloth to obtain a carbon fiber cloth with a size of 18 cm * 2 cm. Put the cut carbon fiber cloth into a beaker with a capacity of 100 mL, pour 50 mL of dilute hydrochloric acid with a concentration of 1 M, place the beaker in an ultrasonic cleaner for 0.5 hours for carbon cloth infiltration operation, then wash the carbon cloth with deionized water, and put it into a vacuum drying oven for vacuum drying for 12 hours to improve the hydrophilic ability of the carbon cloth;

[0050] S2. Weigh 0.197 g of analytical pure Zn(NO 3 ) 2 ·6H 2 O and 0.367 g of analytical pure CoSO 4 ·6H 2 O. Place the weighed substances in a beaker, add 40 mL of deionized water, and stir evenly with a magnetic stirrer until a metal salt solution is formed;

[0051] S3. Weigh 1.3 g of 1,2-methylimidazole and place it in a beaker, pour 40 mL of deionized water, and stir evenly to form an organic solution;

[0052] S4. Place the carbon fiber cloth obtained after the operation of S1 in the organic solution, then slowly pour the metal salt solution into the organic solution, cooperate with a magnetic stirrer for rapid stirring, and place the stirring beaker in a normal temperature environment for 4 hours;

[0053] S5. Take out the stirred carbon fiber cloth, wash the remaining solution on it with deionized water, and then place it in a vacuum drying oven for vacuum drying for 12 hours;

[0054] S6. Place the prepared carbon fiber cloth on a reaction boat, put it into a tube furnace for vacuum sintering, and then immerse the sintered product in 1 wt.% HCl for 2 h to remove the excess Zn metal. After washing and vacuum drying, the three-dimensional metal conductive framework material CC@Co-NCNTs is obtained.

[0055] S7. Cut the three-dimensional metal conductive framework material of CC@Co-NCNTs into circular wafers with a diameter of 12 mm. Subsequently, heat the lithium metal sheet using a heating stage until the lithium sheet becomes molten (220 °C). Place the pre-prepared circular wafer into the liquid molten lithium and soak it for 3 min to fill the three-dimensional metal conductive framework material with lithium metal. Finally, obtain the target product, the composite lithium metal electrode Li-CC@Co-NCNTs with a three-dimensional lithium conduction pathway. This step is carried out entirely in a glove box with an argon atmosphere to prevent the oxidation of lithium metal by water and oxygen in the air. The flowchart of this example is referred to Figure 1 。

[0056] Comparative Example 1 Pure lithium metal electrode

[0057] The pure lithium metal electrode in this comparative example was purchased from Tianqi Lithium Industry, with a thickness of 1 mm and a diameter of 12 mm.

[0058] Example 3 Performance characterization of a three-dimensional metal conductive framework material

[0059] In this example, performance characterization was carried out on the metal conductive framework materials provided in Examples 1-2 and Comparative Example 1. The characterization experiments included: charge-discharge long-cycle test and rate performance test. A standard eight-channel tester (LANHE CT3002A) developed by Wuhan Blue Electronic Co., Ltd. was used to conduct a constant current charge-discharge test on the symmetric battery for rate performance test. The specific experimental steps are as follows:

[0060] (1) Cut and slice the composite lithium metal electrode material of Li-CC@Co-NCNTs with a three-dimensional lithium conduction pathway into circular wafers with a diameter of 12 mm to serve as the positive and negative electrodes of the button battery. Then, in a glove box filled with an argon atmosphere, combine with the electrolyte to make a button battery. The specific steps are: assemble the positive and negative electrodes, the separator (Celgard 2000), and the electrolyte together to form a CR2025 button battery. The solvent in the electrolyte is a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) (v / v = 1:1), and the electrolyte in the electrolyte is 1.0 M LiPF6 and 5 wt.% fluoroethylene carbonate (FEC).

[0061] (2) Place the CR2025 button battery prepared in step (1) on one of the channels of the LANHE CT3002A test device for testing:

[0062] Charge-discharge long-cycle test: At a current density of 5 mA·cm -2 , charge and discharge for 1 h each to conduct a constant current charge-discharge test.

[0063] Rate performance test: Gradually increase the corresponding polarization voltage when increasing the current density until the symmetric battery reaches the critical current density (CCD).

[0064] The experimental results are as Figures 2 to 5 shown below:

[0065] This preparation method can effectively and rapidly produce three-dimensional conductive framework materials and composite lithium metal electrodes with three-dimensional lithium conduction pathways. The prepared composite lithium metal electrodes with three-dimensional lithium conduction pathways, as electrode materials for lithium metal batteries, exhibit good performance in rate tests.

[0066] Figure 2 It can be seen from the analysis of the average hysteresis voltage that at different current densities, the overpotential of the Li-CC@Co-NCNTs electrode is less than that of the Li-CC@Fe-NCNTs electrode, mainly due to its better lithium binding energy and electronic conductivity.

[0067] From Figure 3 it can be seen that as the current density increases, the symmetric cell of the pure Li electrode quickly short-circuits, indicating extremely unstable lithium deposition behavior inside the cell. However, the overpotential of the Li-CC@Co-NCNTs electrode has better regularity and a smaller increment compared to that of the pure Li electrode, indicating that the Li stripping and deposition behaviors on the CC@Co-NCNTs framework are stable at high current densities.

[0068] Figure 4 (a) shows the galvanostatic charge-discharge curves of the Li-CC@Co-NCNTs symmetric cell and the pure Li symmetric cell. The Li-CC@Co-NCNTs symmetric cell can continuously operate for 1200 hours at a current density of 400 μA cm -2 and shows a very smooth lithium stripping and deposition curve. Figure 4 (b) is the charge-discharge voltage curves of three different stages after magnification. It can be seen that the polarization voltages of the three stages are almost the same, indicating that the symmetric cell with Li-CC@Co-NCNTs as the electrode material has a more stable current, a smaller internal resistance, and is more suitable for the generation of lithium ion deintercalation / insertion behaviors. At the same time, this is mainly attributed to the better lithium binding energy and better chemical activity of Li-CC@Co-NCNTs. On the contrary, Figure 4 (c) shows the pure Li symmetric cell. When operating at a current density of 30 μA cm -2 , the voltage drops significantly and a short-circuit fault occurs only after 40 hours.

[0069] Figure 5 shows the scanning electron microscope and transmission electron microscope results of the CC@M-NCNTs materials; among them, (a) is the high-magnification SEM image of CC@Co-NCNTs; (b) is the TEM image of CC@Co-NCNTs; (c) is the high-magnification SEM image of CC@Fe-NCNTs; (d) is the TEM image of CC@Fe-NCNTs.Figure 5 (a)(b) show that the Co-NCNTs nanosheets are covered with tiny nitrogen-doped carbon nanotubes. Each nitrogen-doped carbon nanotube has a diameter of about 8 nm and a length of tens of nanometers. In other words, the Co-NCNTs nanosheets are a complex network interwoven by a large number of nitrogen-doped carbon nanotubes, and Co clusters are evenly distributed inside and outside the N-doped carbon nanotube walls. Figure 5 (d)(e) show that for CC@Fe-NCNTs, the structure of the thin nanosheets is slightly different from that of the Co-NCNTs nanosheets. The nanosheets are separated by nitrogen-doped carbon nanotubes and are branch-like. The diameter of each nitrogen-doped carbon nanotube is also slightly shorter (about 7 nm). Fe clusters are also distributed inside and outside the walls of the carbon nanotubes.

[0070] In summary, the three-dimensional metal conductive skeleton prepared by this innovative preparation method can effectively improve the cycling performance of lithium metal batteries during the cycling process, and inhibit the growth of dendrites during the cycling process, thereby achieving stable and long-term battery safety cycling.

[0071] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A three-dimensional metal conductive skeleton material, characterized in that: The three-dimensional metal conductive skeleton material is represented by CC@M-NCNTs, wherein CC is carbon fiber cloth, M is metal nanocrystal, which is at least any one of Co, Fe, Ni, Cu, Mn or Zn, and NCNT is nitrogen-doped carbon nanotube; the three-dimensional metal conductive skeleton material is based on carbon fiber cloth, and nitrogen-doped carbon nanotubes modified by metal nanocrystals are deposited on the surface.

2. A composite metal lithium electrode having a three-dimensional lithium-conducting path, characterized in that: The composite metal lithium electrode with a three-dimensional lithium conductive path is represented by Li-CC@M-NCNTs, wherein CC@M-NCNTs is the three-dimensional metal conductive skeleton material according to claim 1, and Li represents that metal Li is filled on the surface of CC@M-NCNTs.

3. The method for preparing a three-dimensional metal conductive skeleton material according to claim 1, characterized in that: The following steps are involved: S1. Cutting the carbon fiber cloth, soaking the cut carbon fiber cloth in dilute hydrochloric acid, and ultrasonicating; After the ultrasonic treatment, the carbon fiber cloth is washed and dried to obtain the pretreated carbon fiber cloth for later use; S2. Weigh the metal salt, add the solvent, stir evenly, and prepare a metal salt solution; S3. Weigh 1,2-dimethylimidazole, add solvent, stir evenly, and prepare an organic solution; S4. The pretreated carbon fiber obtained in S1 is arranged in the organic solution prepared in step S3, and then the metal salt solution prepared in step S2 is slowly poured into the organic solution and stirred; S5. Take out the stirred carbon fiber cloth, wash and dry it; S6. The carbon fiber cloth prepared in S5 is sintered, and then the sintered product is soaked in dilute hydrochloric acid; after soaking, it is washed and dried to obtain a three-dimensional metal conductive skeleton material CC@M-NCNTs.

4. The method for preparing a three-dimensional metal conductive skeleton material according to claim 3, characterized in that: The size of the carbon fiber cloth cut in step S1 is (10-100) cm×(1-10) cm; the concentration of the dilute hydrochloric acid is 0.1-3 M; the ultrasonic time is 0.1-10 h; the drying time is 8-24 h; and the drying temperature is 25-100° C.

5. The method for preparing a three-dimensional metal conductive skeleton material according to claim 3, characterized in that: The cation in the metal salt described in step S2 is at least any one of Co, Fe, Ni, Cu, Mn or Zn, and the anion is any one of sulfate and nitrate; the concentration of the metal cation in the metal salt solution is 0.1-1 mol / mL; the solvent of the metal salt solution is deionized water; The concentration of 1,2-dimethylimidazole in the organic solution in step S3 is 0.1-1 mol / mL; the solvent of the organic solution is deionized water.

6. The method for preparing a three-dimensional metal conductive skeleton material according to claim 3, characterized in that: The stirring temperature in step S4 is 15 to 30° C. and the stirring time is 2 to 12 hours; The cleaning in step S5 is: cleaning with deionized water for multiple times; the drying time is 8 to 24 hours; the drying temperature is 25 to 100°C.

7. The method for preparing a three-dimensional metal conductive skeleton material according to claim 3, characterized in that: The temperature control scheme of the sintering in step S6 is: heating to 600°C at a heating rate of 1°C / min, and then keeping warm for 2 hours; the concentration of the dilute hydrochloric acid is 0.1-5wt.%; and the infiltration time is 1-6 hours.

8. The method for preparing a composite metal lithium electrode having a three-dimensional lithium conductive path according to claim 2, characterized in that: Steps S1 to S6 of the preparation method are steps S1 to S6 described in the third technical solution. After obtaining the three-dimensional metal conductive skeleton material CC@M-NCNTs, step S7 is performed: S7. Cut the three-dimensional metal conductive skeleton material CC@M-NCNTs to a suitable size, and then heat the metal lithium sheet to a molten state; place the three-dimensional metal conductive skeleton material CC@M-NCNTs into the molten metal lithium for infiltration, and finally obtain the target product: a composite metal lithium electrode Li-CC@M-NCNTs with a three-dimensional lithium conductive path; The three-dimensional metal conductive skeleton material CC@Fe-NCNTs is immersed in molten metal lithium for 10 to 30 minutes.

9. An application of the composite metal lithium electrode with a three-dimensional lithium conducting path as claimed in claim 2, characterized in that: The composite metal lithium electrode with three-dimensional lithium conductive path is used for preparing lithium metal batteries.

10. A battery, characterized in that: The battery is a CR2025 button cell; the positive electrode and the negative electrode of the CR2025 button cell both adopt the composite metal lithium electrode with a three-dimensional lithium conductive path as described in claim 2, the separator is Celgard2000, the solvent component in the electrolyte is a mixture of ethylene carbonate and dimethyl carbonate, the volume ratio of the two is 1:1, and the electrolyte component in the electrolyte is 1.0M LiPF6 and 5wt.% fluoroethylene carbonate.

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