Array negative electrode, preparation method and application thereof

Abstract

The present invention provides an array-type negative electrode, a preparation method, and an application thereof. The preparation method comprises: etching metal nanowires with an aqueous hydrofluoric acid solution to obtain an array-structured metal nanowire, subjecting the metal nanowires to a hydrothermal reaction with a mixed solution of a transition metal salt and 2-methylimidazole, obtaining a hydrothermal product solution, and sintering the solution twice to obtain an array-type negative electrode; wherein the first sintering is performed at 600-1000°C in an argon-hydrogen mixed atmosphere, and the second sintering is performed at 150-300°C in an air atmosphere. The present invention uses a metal nanowire array as a conductive substrate and, through hydrothermal post-sintering, allows transition metal oxides to grow directly on the nanowire array. In addition to providing support, the metal nanowire array can also improve conductivity. The two sintering processes can retain the structural characteristics of the transition metal organic framework material obtained by the hydrothermal reaction. The preparation process of the present invention is simple and easy to operate, and can produce an array-type negative electrode material with excellent electrochemical activity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to an array-type negative electrode, a preparation method thereof, and applications thereof. Background Art

[0002] Lithium-ion batteries have become a research hotspot in recent years due to their numerous advantages, including high voltage, high capacity, long cycle life, excellent safety, and environmental friendliness. Currently, the production process for lithium-ion battery electrodes primarily involves slurrying and coating. This process is time-consuming and labor-intensive, and often suffers from uneven dispersion of electrode materials and particle agglomeration. Therefore, developing novel electrode processes is of great significance. Furthermore, the primary anode material currently used in commercial lithium-ion batteries is graphite, which has a theoretical specific capacity of only 372 mAh / g, making it difficult to meet the increasing energy density demands of the power sector. Among other potential anode material candidates, transition metal oxides have attracted research attention due to their unique conversion reaction mechanisms. Since 1 mol of transition metal can convert 3–4 mol of lithium ions, their theoretical specific capacity approaches 1000 mAh / g. However, transition metal oxides have poor conductivity, resulting in their actual specific capacity far below their theoretical value and poor cycle life.

[0003] Patent CN108695507A discloses a method for preparing carbon-coated porous cobalt oxide nanoparticles. Cobalt nitrate and oxalic acid are mixed and ground, washed with water, and dried. The mixture is then calcined in air to obtain porous cobalt oxide. This is then mixed with a carbon source precursor in ethanol and ground evenly, followed by drying. Finally, the mixture is heated and carbonized under a protective atmosphere to obtain carbon-coated porous cobalt oxide nanoparticles. Patent CN105870439A discloses a method for preparing porous cobalt oxide. Cobalt salt and imidazole derivatives are dissolved and stirred, then sealed in a hydrothermal reactor and reacted at 20-190°C for 2-48 hours. The solid is then centrifuged, washed, and dehydrated to obtain a cobalt oxide precursor. Finally, the mixture is calcined in air at 350-600°C and cooled to room temperature to obtain porous cobalt oxide. Patent CN109650464A discloses a method for preparing a cobalt tetroxide nanowire array, its products, and applications. The cobalt tetroxide nanowire array is prepared by in-situ growth on a conductive substrate. The synthesis is carried out using a one-step hydrothermal method and a template method to prepare a cobalt tetroxide nanowire array supported on a conductive substrate titanium foil. Cobalt salt and water are used as solvents. Urea and ammonium fluoride are added during stirring. After uniform stirring, the solution and the conductive substrate titanium foil are transferred to a polytetrafluoroethylene reactor, a hydrothermal reaction is carried out in an oven, and then high-temperature calcination is carried out under a nitrogen atmosphere. However, the above patents all have problems such as poor electrode structure stability, complex processes, and poor electrochemical performance of the products. Summary of the Invention

[0004] The main purpose of the present invention is to provide an array-type negative electrode, a preparation method and application thereof, so as to solve the problems of complex preparation process and poor electrochemical performance of lithium-ion battery negative electrodes in the prior art.

[0005] To achieve the above-mentioned object, according to one aspect of the present invention, a method for preparing an array-type negative electrode is provided, comprising the following steps: step S1, etching metal nanowires with an aqueous hydrofluoric acid solution to obtain array-structured metal nanowires; step S2, mixing a transition metal salt and 2-methylimidazole to obtain a mixed solution; step S3, mixing the array-structured metal nanowires and the mixed solution, conducting a hydrothermal reaction, and obtaining a hydrothermal product solution; step S4, subjecting the hydrothermal product solution to a first sintering to obtain a first sintered product; step S5, subjecting the first sintered product to a second sintering to obtain an array-type negative electrode; wherein the first sintering is carried out in an argon-hydrogen mixed atmosphere, and the temperature of the first sintering is 600-1000°C; the second sintering is carried out in an air atmosphere, and the temperature of the second sintering is 150-300°C.

[0006] Furthermore, in step S1, the metal nanowires are titanium nanowires and / or nickel nanowires; preferably, the metal nanowires have a diameter of 50 to 150 nm and a length of 2 to 8 μm.

[0007] Furthermore, in step S1 , the mass concentration of the hydrofluoric acid aqueous solution is 2-5%, and the etching time is 600-1200 s.

[0008] Furthermore, in step S2, the molar ratio of the transition metal salt to 2-methylimidazole is (1 to 5):1; preferably, the transition metal salt is one or more of an iron salt, a cobalt salt, a nickel salt, a manganese salt and a copper salt, and optionally, the transition metal salt also includes a zinc salt; more preferably, the transition metal salt is cobalt nitrate hexahydrate, or a mixture of cobalt nitrate hexahydrate and zinc nitrate hexahydrate.

[0009] Furthermore, the temperature of the hydrothermal reaction is 60 to 160° C., and the time of the hydrothermal reaction is 1 to 5 hours.

[0010] Furthermore, the first sintering time is 2 to 6 hours, and the second sintering time is 1 to 3 hours.

[0011] According to another aspect of the present invention, an array-type negative electrode is provided, which is obtained by the preparation method of the present invention and includes a conductive substrate and an active material covering the surface of the conductive substrate, wherein the conductive substrate is a metal nanowire array structure and the active material is a transition metal oxide.

[0012] Furthermore, the metal nanowires are titanium nanowires and / or nickel nanowires, the diameter of the metal nanowires is 50 to 150 nm, and the length is 2 to 8 μm; preferably, the transition metal oxide is one or more oxides of iron, cobalt, nickel, manganese and copper.

[0013] According to another aspect of the present invention, a battery is provided, comprising a positive electrode, a negative electrode, an electrolyte and a separator, wherein the negative electrode is obtained by the preparation method of the present invention, or is the above-mentioned array negative electrode.

[0014] Furthermore, the positive electrode includes an active material, a conductive agent and a binder, the active material is one or more of lithium cobalt oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium manganate, ternary material, and lithium-rich manganese-based material, the conductive agent is one or more of carbon black, graphene and carbon tubes, and the binder is polyvinylidene fluoride and / or polyacrylic acid; preferably, by weight percentage, the positive electrode includes 92-98% of active material, 0.5-1.5% of conductive agent, and 0.5-1.5% of binder; preferably, the electrolyte includes a solvent, a lithium salt and an additive, the solvent is one or more of EC, PC, DMC, DEC, EMC, FEC and EA, the lithium salt is one or more of LiPF6, LiFSI, LiTFSI, LiBF4, LiClO4 and LiBOB, and the additive is one or more of VC, FEC, DTD, PS and ES; the separator is polyethylene, polypropylene or a composite film.

[0015] The technical solution of the present invention is applied. First, a metal nanowire array is used as a conductive substrate. A transition metal oxide is directly grown on the nanowire array by hydrothermal post-sintering to obtain an electrode with a self-supporting structure based on in-situ growth. In addition to playing a supporting role, the metal nanowire array can also improve the conductivity. The electrode prepared by this method does not need to add a conductive agent and a binder and can be directly used as a battery negative electrode. Second, the present invention uses a transition metal organic framework material obtained by a hydrothermal reaction as a precursor and prepares a transition metal oxide by two sintering processes. The unique two-time sintering process can still retain the high specific surface area and high porosity structure of the precursor, while retaining the nitrogen and carbon elements in the transition metal organic framework material without the need to introduce a carbon source separately, which is also beneficial to improving the conductivity and cycle performance of the material. The preparation method of the present invention has a simple process flow and is easy to operate, and can produce an array-type negative electrode material with excellent electrochemical activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0017] Figure 1 The SEM image of the array-type negative electrode according to Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] As described in the background of the present invention, the prior art has the problem of complex preparation process and poor electrochemical performance of lithium-ion battery negative electrodes. To solve the above problems, in a typical embodiment of the present invention, a method for preparing an array-type negative electrode is provided, comprising the following steps: step S1, etching metal nanowires with a hydrofluoric acid aqueous solution to obtain an array-type metal nanowire structure; step S2, mixing a transition metal salt and 2-methylimidazole to obtain a mixed solution; step S3, mixing the array-type metal nanowires and the mixed solution, and performing a hydrothermal reaction to obtain a hydrothermal product solution; step S4, performing a first sintering on the hydrothermal product solution to obtain a first sintered product; step S5, performing a second sintering on the first sintered product to obtain an array-type negative electrode; wherein the first sintering is performed in an argon-hydrogen mixed atmosphere at a temperature of 600 to 1000°C; and the second sintering is performed in an air atmosphere at a temperature of 150 to 300°C.

[0020] The present invention, on the one hand, etches metal nanowires with hydrofluoric acid to obtain metal nanowires in an array structure as a conductive substrate; on the other hand, mixes a transition metal salt and 2-methylimidazole and dissolves them in an organic solvent; then mixes the two and conducts a hydrothermal reaction to form a transition metal organic framework structure with a high specific surface area and high voids, with the transition metal as the center and 2-methylimidazole as the organic ligand. The structure is directly grown on the nanowire array to form the basic structure of the array-type negative electrode. The solvent thermal method also allows for more complete contact between the reactants and better uniformity of the generated product.

[0021] Finally, the hydrothermal product solution is sintered twice. The first high-temperature sintering in an argon-hydrogen atmosphere plays a reducing role, reducing the carbon-containing part of the organic ligand in the transition metal organic framework structure to carbon. When the sintering temperature is less than 600°C, the reduction effect is poor. When the sintering temperature is higher than 1000°C, the reduction effect will not be improved, but the cost will increase. Therefore, the present invention limits the first sintering temperature to 600-1000°C; the second low-temperature sintering in an air atmosphere can prevent the oxidation of carbon in the transition metal organic framework structure at a lower temperature, thereby preserving the conductivity of carbon. On the other hand, it oxidizes the transition metal into transition metal oxides, so that the transition metal oxides grow directly on the nanowire array, obtaining an array-type negative electrode based on an in-situ growth self-supporting structure. When the second sintering temperature is less than 150°C, the transition metal oxidation is insufficient. When the temperature is higher than 300°C, the carbon in the transition metal organic framework structure will be oxidized, and the electrochemical properties such as conductivity will be reduced. Therefore, the present invention limits the second sintering temperature to 150-300°C.

[0022] In addition to providing support, the nanowire arrays also enhance electrical conductivity. Electrodes fabricated using this method require no conductive agents or binders and can be used directly as battery negative electrodes. The unique double-sintering process preserves the high surface area and high porosity of the transition metal-organic framework (TMOF), serving as a site for lithium-ion reactions and increasing the actual gram capacity. Furthermore, the retention of nitrogen and carbon in the TMOF eliminates the need for a separate carbon source, improving the material's electrical conductivity and cycling performance while further simplifying the fabrication process.

[0023] Considering that metal nanowires need to support the negative electrode structure, be easy to etch, and possess a certain degree of conductivity, in a preferred embodiment, in step S1, the metal nanowires are titanium nanowires and / or nickel nanowires; preferably, the metal nanowires have a diameter of 50-150 nm and a length of 2-8 μm. These two types of metal nanowires offer excellent structural support and conductivity, while their high porosity allows for easier etching to form nanowire arrays, paving the way for the subsequent growth of the transition metal-organic framework.

[0024] In a preferred embodiment, in step S1, the mass concentration of the hydrofluoric acid aqueous solution is 2-5%, and the etching time is 600-1200 seconds, which achieves a better etching effect. The etching process includes first ultrasonically cleaning the metal nanowires with acetone, a 1% dilute hydrochloric acid aqueous solution, deionized water, and anhydrous ethanol, followed by drying, and finally etching in a hydrofluoric acid aqueous solution to obtain an array of metal nanowires. The cleaning process can remove dirt and oxidized impurities that may be present on the surface of the metal nanowires, making it easier to obtain a clean surface of the array of metal nanowires after subsequent etching.

[0025] In order to obtain a transition metal organic framework structure with a higher specific surface area and higher porosity, in a preferred embodiment, in step S2, the molar ratio of the transition metal salt and 2-methylimidazole is (1-5):1; preferably, the transition metal salt is one or more of an iron salt, a cobalt salt, a nickel salt, a manganese salt and a copper salt, and optionally, the transition metal salt also includes a zinc salt; more preferably, the transition metal salt is cobalt nitrate hexahydrate, or a mixture of cobalt nitrate hexahydrate and zinc nitrate hexahydrate. The transition metal organic framework material formed by the transition metal salts in the above ratio has a larger specific surface area and pores, is more suitable as a site for lithium ion reaction, and further improves the actual gram capacity. Most preferably, the transition metal salt is a mixture of cobalt nitrate hexahydrate and zinc nitrate hexahydrate, with a mass ratio of 1:(1-3), wherein zinc volatilizes during the high-temperature sintering process, can further form pores, increase the porosity and specific surface area of ​​the organic framework structure, and obtain better electrical performance of the negative electrode.

[0026] The present invention does not require the reaction ratio of the array-structured metal nanowires and the mixed solution in step S3. Those skilled in the art can determine this ratio based on the desired array-type negative electrode, based on the present invention. In a preferred embodiment, the hydrothermal reaction temperature is 60-160°C, and the hydrothermal reaction time is 1-5 hours. These hydrothermal temperatures and times allow for more complete growth of the transition metal organic framework material on the nanowire array.

[0027] In order to better utilize the unique conversion reaction mechanism of transition metals, while improving the conductivity of the negative electrode material, further improve the actual specific capacity and cycle performance, preferably, the first sintering time is 2 to 6 hours and the second sintering time is 1 to 3 hours, so that the reduction and oxidation effects are more sufficient without causing oxidation of carbon in the transition metal organic framework.

[0028] In another typical embodiment of the present invention, an array-type negative electrode is provided, obtained by the preparation method of the present invention; wherein the array-type negative electrode comprises a conductive substrate and an active material coated on the surface of the conductive substrate, wherein the conductive substrate is a metal nanowire array structure, and the active material is a transition metal oxide, wherein the transition metal oxide comprises, by weight, 20-50 parts transition metal, 20-40 parts oxygen, 5-10 parts carbon, and 2-10 parts nitrogen. The array-type negative electrode of the present invention has a self-grown electrode structure, wherein the nitrogen and carbon elements in the material, as well as the high specific surface area and high porosity transition metal organic framework, are retained without the need for a separate carbon source. The metal nanowire array structure not only provides support but also improves conductivity. Compared with traditional mixing and coating processes, no additional conductive agent or binder is required during the electrode production process. Moreover, the elimination of the mixing process can prevent problems such as material agglomeration during the mixing process and shorten the time required for electrode preparation.

[0029] Compared with single planar structures such as titanium foil, the nanowire array structure of the array-type negative electrode of the present invention is more structurally stable. In order to construct a more structurally stable array structure, in a preferred embodiment, the metal nanowires are titanium nanowires and / or nickel nanowires with a diameter of 50 to 150 nm and a length of 2 to 8 μm; preferably, the transition metal oxide is one or more oxides of iron, cobalt, nickel, manganese and copper. The transition metal used is not limited to metallic cobalt, and the transition metal can be selected as needed.

[0030] In another typical embodiment of the present invention, a battery is provided, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the negative electrode is obtained by the preparation method of the present invention or is the array-type negative electrode described above. Due to the use of the array-type negative electrode of the present invention, the battery's conductivity and cycle performance are significantly improved, and its electrochemical activity is further enhanced.

[0031] The positive electrode material of the above-mentioned battery can use the commonly used materials in this field. In order to further improve the matching of the positive electrode material and the array-type negative electrode of the present invention, thereby obtaining a battery with better overall performance, in a preferred embodiment, the positive electrode includes an active material, a conductive agent and a binder. The active material is one or more of lithium cobalt oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, a ternary material, and a lithium-rich manganese-based material. Preferably, the ternary material is one or more of NCM111, NCM523, NCM811 and NCA, the conductive agent is one or more of carbon black, graphene and carbon tubes, and the binder is polyvinylidene fluoride and / or polyacrylic acid; preferably, by weight percentage, the positive electrode includes 92-98% of active material, 0.5-1.5% of conductive agent, and 0.5-1.5% of binder, which is easy to prepare.

[0032] Accordingly, the electrolyte preferably includes a solvent, a lithium salt and an additive, the solvent is one or more of EC, PC, DMC, DEC, EMC, FEC, EA, the lithium salt is one or more of LiPF6, LiFSI, LiTFSI, LiBF4, LiClO4 and LiBOB, and the additive is one or more of VC, FEC, DTD, PS and ES; the separator is polyethylene, polypropylene or a composite film, which can further improve the stability and conductivity of the electrolyte.

[0033] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0034] Example 1

[0035] Step S1, etching titanium nanowires with a diameter of 100 nm and a length of 5 μm, ultrasonically cleaning them with acetone, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence, drying them, placing them in a 3% by mass hydrofluoric acid solution, and etching them for 900 s to obtain an array structure of titanium nanowires;

[0036] Step S2, dissolving cobalt nitrate hexahydrate, zinc nitrate hexahydrate, and 2-methylimidazole in methanol at a molar ratio of 1:2:1, and stirring until completely dissolved to obtain a mixed solution;

[0037] Step S3, mixing the array structured titanium nanowires and the mixed solution, transferring the mixture into a reactor for hydrothermal reaction at a temperature of 80° C. for 5 h, cooling the mixture and taking it out to obtain a hydrothermal product solution;

[0038] Step S4, drying the hydrothermal product solution, and then sintering it at a high temperature in an argon-hydrogen mixed atmosphere at a sintering temperature of 900° C. for 5 hours to obtain a first sintered product;

[0039] Step S5 , performing secondary sintering on the first sintered product in an air atmosphere at a sintering temperature of 200° C. and a sintering time of 1.5 h, and taking out the product to obtain an array-type negative electrode.

[0040] SEM observation shows that the array negative electrode includes a conductive substrate and an active material covering the surface of the conductive substrate. The surface of the conductive substrate is a titanium nanowire array structure, and the active material is cobalt tetroxide. The SEM image of the array negative electrode material is shown in Figure 1 .

[0041] Example 2

[0042] The only difference between Example 2 and Example 1 is that zinc nitrate hexahydrate is not added in step S2.

[0043] Example 3

[0044] The only difference between Example 3 and Example 1 is that zinc nitrate hexahydrate is not added in step S2, and the sintering temperature in step S4 is 600°C.

[0045] Example 4

[0046] Step S1, etching titanium nanowires with a diameter of 50 nm and a length of 2 μm, and ultrasonically cleaning them with acetone, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence, drying them, placing them in a 2% hydrofluoric acid solution, and etching them for 1200 s to obtain an array structure of titanium nanowires;

[0047] Step S2, dissolving cobalt nitrate hexahydrate, zinc nitrate hexahydrate, and 2-methylimidazole in methanol at a molar ratio of 1:2:1, and stirring until completely dissolved to obtain a mixed solution;

[0048] Step S3, mixing the array structured titanium nanowires and the mixed solution, transferring the mixture into a reactor for hydrothermal reaction at a temperature of 60° C. for 5 h, cooling the mixture and taking it out to obtain a hydrothermal product solution;

[0049] Step S4, drying the hydrothermal product solution, and then sintering it at a high temperature in an argon-hydrogen mixed atmosphere at a sintering temperature of 900° C. for 5 hours to obtain a first sintered product;

[0050] Step S5 , performing secondary sintering on the first sintered product in an air atmosphere at a sintering temperature of 200° C. and a sintering time of 1.5 h, and taking out the product to obtain an array-type negative electrode.

[0051] SEM observation shows that the array-type negative electrode includes a conductive substrate and an active material covering the surface of the conductive substrate. The surface of the conductive substrate is a titanium nanowire array structure, and the active material is cobalt tetroxide.

[0052] Example 5

[0053] Step S1, etching nickel nanowires with a diameter of 150 nm and a length of 8 μm, and ultrasonically cleaning them with acetone, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence, drying them, and etching them in a 5% hydrofluoric acid solution for 600 seconds to obtain an array structure of nickel nanowires;

[0054] Step S2, dissolving cobalt nitrate hexahydrate, zinc nitrate hexahydrate, and 2-methylimidazole in methanol at a molar ratio of 2:2:1, and stirring until completely dissolved to obtain a mixed solution;

[0055] Step S3, mixing the array structured nickel nanowires and the mixed solution, transferring the mixture into a reactor for hydrothermal reaction at a temperature of 160° C. for 1 hour, cooling the mixture and taking it out to obtain a hydrothermal product solution;

[0056] Step S4, drying the hydrothermal product solution, and then sintering it at a high temperature in an argon-hydrogen mixed atmosphere at a sintering temperature of 900° C. for 5 hours to obtain a first sintered product;

[0057] Step S5 , performing secondary sintering on the first sintered product in an air atmosphere at a sintering temperature of 200° C. and a sintering time of 1.5 h, and taking out the product to obtain an array-type negative electrode.

[0058] SEM observation shows that the array-type negative electrode includes a conductive substrate and an active material covering the surface of the conductive substrate. The surface of the conductive substrate is a nickel nanowire array structure, and the active material is cobalt tetroxide.

[0059] Examples 6 to 9

[0060] The only difference between Examples 6 to 9 and Example 1 is the sintering temperature and time, see Table 1 for details.

[0061] Table 1

[0062]

[0063] Comparative Example 1

[0064] The only difference between Comparative Example 1 and Example 1 is that in step S1, the titanium foil is etched, ultrasonically cleaned with acetone, dilute hydrochloric acid, deionized water, and anhydrous ethanol in sequence, dried, placed in a 3% by mass hydrofluoric acid solution, and etched for 900 seconds to obtain a conductive substrate.

[0065] Comparative Example 2

[0066] The only difference between Comparative Example 2 and Example 1 is that in step S2, cobalt nitrate hexahydrate, zinc nitrate hexahydrate, and oxalic acid are mixed and dissolved in methanol in a molar ratio of 1:2:1, and stirred until completely dissolved to obtain a mixed solution.

[0067] Comparative Example 3

[0068] The only difference between Comparative Example 3 and Example 1 is that the high-temperature sintering in step S4 is not performed, and the hydrothermal product is directly sintered at 500° C. for 3 h to obtain the negative electrode.

[0069] The array-type negative electrodes in Examples 1 to 9 and Comparative Examples 1 to 3 were assembled into button cells and performance tested. The results are shown in Table 2.

[0070] Table 2

[0071]

[0072]

[0073] As can be seen from the above, compared with the comparative example, the embodiment of the present invention uses a metal nanowire array as a conductive substrate, and through a hydrothermal post-sintering method, a transition metal oxide is directly grown on the nanowire array, wherein the metal nanowire array not only plays a supporting role, but also can improve the conductivity. Moreover, the present invention uses a transition metal organic framework material obtained by a hydrothermal reaction as a precursor, and prepares a transition metal oxide by sintering twice. The unique two-time sintering process can still retain the high specific surface area and high porosity structure of the precursor, while retaining the nitrogen and carbon elements in the transition metal organic framework material without having to introduce a carbon source separately, which is also beneficial to improving the conductivity and cycle performance of the material. The preparation method of the present invention has a simple process flow and is easy to operate, and can produce an array-type negative electrode material with excellent electrochemical activity. In addition, it can be seen that when each process parameter is within the preferred range of the present invention, the electrochemical activity of the prepared array-type negative electrode material is optimal.

[0074] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing an array negative electrode, characterized in that: The following steps are involved: Step S1, etching the metal nanowires with a hydrofluoric acid aqueous solution to obtain an array structure of metal nanowires; Step S2, mixing a transition metal salt and 2-methylimidazole to obtain a mixed solution; Step S3, mixing the array structured metal nanowires and the mixed solution, performing a hydrothermal reaction, and obtaining a hydrothermal product solution; Step S4, performing a first sintering on the hydrothermal product solution to obtain a first sintered product; Step S5, performing a second sintering on the first sintered product to obtain the array-type negative electrode; The temperature of the hydrothermal reaction is 60-160° C., and the time of the hydrothermal reaction is 1-5 hours. The first sintering is carried out in an argon-hydrogen mixed atmosphere, and the temperature of the first sintering is 600~1000℃, and the time of the first sintering is 2~6h; the second sintering is carried out in an air atmosphere, and the temperature of the second sintering is 150~300℃, and the time of the second sintering is 1~3h.

2. The preparation method according to claim 1, characterized in that In step S1, the metal nanowires are titanium nanowires and / or nickel nanowires.

3. The preparation method according to claim 2, characterized in that The metal nanowire has a diameter of 50-150 nm and a length of 2-8 μm.

4. The preparation method according to claim 1 or 2, characterized in that In step S1, the mass concentration of the hydrofluoric acid aqueous solution is 2-5%, and the etching time is 600-1200 seconds.

5. The preparation method according to claim 1 or 2, characterized in that In the step S2, the molar ratio of the transition metal salt to the 2-methylimidazole is (1-5):

1.

6. The preparation method according to claim 5, characterized in that The transition metal salt is one or more of iron salt, cobalt salt, nickel salt, manganese salt and copper salt.

7. The preparation method according to claim 6, characterized in that The transition metal salt also includes zinc salt.

8. The preparation method according to claim 7, characterized in that The transition metal salt is cobalt nitrate hexahydrate, or a mixture of cobalt nitrate hexahydrate and zinc nitrate hexahydrate.

9. An array-type negative electrode, characterized in that: Obtained by the preparation method according to any one of claims 1 to 8; wherein the array-type negative electrode includes a conductive substrate and an active material covering the surface of the conductive substrate, the conductive substrate is a metal nanowire array structure, and the active material is a transition metal oxide.

10. The array-type negative electrode according to claim 9, characterized in that: The metal nanowires are titanium nanowires and / or nickel nanowires, and the diameter of the metal nanowires is 50-150 nm and the length is 2-8 μm.

11. The array-type negative electrode according to claim 10, characterized in that: The transition metal oxide is one or more oxides of iron, cobalt, nickel, manganese and copper.

12. A battery comprising a positive electrode, a negative electrode, an electrolyte and a separator, characterized in that: The negative electrode is obtained by the preparation method according to any one of claims 1 to 8, or is the array-type negative electrode according to any one of claims 9 to 11.

13. The battery according to claim 12, characterized in that The positive electrode includes an active material, a conductive agent and a binder. The active material is one or more of lithium cobalt oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium manganese oxide, ternary materials, and lithium-rich manganese-based materials. The conductive agent is one or more of carbon black, graphene and carbon tubes. The binder is polyvinylidene fluoride and / or polyacrylic acid.

14. The battery according to claim 13, characterized in that In terms of weight percentage, the positive electrode includes 92-98% of the active material, 0.5-1.5% of the conductive agent, and 0.5-1.5% of the binder.

15. The battery according to claim 13, characterized in that The electrolyte includes a solvent, a lithium salt and an additive, wherein the solvent is one or more of EC, PC, DMC, DEC, EMC, FEC and EA, the lithium salt is one or more of LiPF6, LiFSI, LiTFSI, LiBF4, LiClO4 and LiBOB, and the additive is one or more of VC, FEC, DTD, PS and ES; the separator is polyethylene, polypropylene or a composite film.

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