Nitrogen-doped carbon-coated zinc oxide hollow structure material, preparation method thereof and application of nitrogen-doped carbon-coated zinc oxide hollow structure material in lithium-sulfur battery

Abstract

The invention provides a nitrogen-doped carbon-coated zinc oxide hollow structure material, a preparation method thereof and application of the nitrogen-doped carbon-coated zinc oxide hollow structure material in a lithium-sulfur battery. The material takes zinc oxide as a core (the volume ratio is 1 / 4-1 / 2), and a nitrogen-doped carbon shell layer with multistage pores is coated outside the zinc oxide. The material is based on a ZIF-8 coated zinc oxide precursor, conversion of a nitrogen-doped carbon layer is realized through carbonization pyrolysis, and a hollow structure is constructed in combination with etching. According to the nitrogen-doped carbon shell disclosed by the invention, high loading of sulfur and chemical anchoring of polysulfide are realized through multistage pores and a polar surface; the zinc oxide component and sulfur form a coordination effect by utilizing crystal face characteristics, and lithium ions are induced to uniformly deposit inwards through lithium affinity; and the hollow structure is combined with a carbon / zinc oxide heterogeneous interface to synergistically optimize the performance of the sulfur positive electrode and the lithium negative electrode. When applied to the lithium-sulfur battery, the composite material can significantly improve the sulfur utilization rate, inhibit the volume expansion of the electrode and improve the lithium deposition morphology and cycle stability, and meanwhile, has high specific capacity and long cycle life, and provides a new thought for the design of the integrated lithium-sulfur battery electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and particularly relates to a nitrogen-doped carbon-coated zinc oxide hollow structure material, a preparation method thereof, and an application in a lithium-sulfur battery. Background Art

[0002] With the rapid development of electric vehicles and various electronic products, the demand for high-energy-density energy storage systems is increasing day by day. This trend has promoted the research and development of new battery technologies to meet the urgent need for higher-performance, more economical, and more environmentally friendly batteries. The lithium-sulfur battery, as a secondary battery, has a high theoretical specific capacity (1675 mA g -1 ) and a high energy density (2600 Wh kg -1 ) and low cost, and is considered to be the most promising next-generation battery.

[0003] Currently, the lithium-sulfur battery faces two challenges: First, on the sulfur cathode side, the polysulfides formed during the charge and discharge process of sulfur will dissolve in the ether-based electrolyte and shuttle to the lithium metal anode and react with it, resulting in a serious shuttle effect. At the same time, the conductivity of sulfur and the discharge product lithium sulfide is low, and there is a volume difference. During the cycling process, the material expands and contracts repeatedly inside, gradually accumulating, resulting in a decline in the mechanical properties of the electrode material, and ultimately causing the structure of the cathode material to collapse and pulverize, seriously affecting the cycle life of the battery. Second, due to the inherent superactivity and non-host characteristics of metallic lithium, infinite volume fluctuations and uncontrollable dendrite growth will occur during the lithium deposition / stripping process, resulting in the continuous rupture and formation of short circuits in the solid electrolyte interphase layer (SEI). These problems inevitably lead to low Coulomb efficiency (CE), serious capacity attenuation, and even potential safety hazards, seriously hindering the practical application of the lithium metal anode. In addition, the traditional positive and negative electrodes use different carrier materials, which easily cause the incompatibility of their surface chemical properties and interfaces. These problems limit the large-scale application of lithium-sulfur batteries.

[0004] In view of the above situation, it is urgent to develop a safe and reliable two-way carrier material that can adsorb elemental sulfur as the cathode material and deposit metallic lithium as the anode material, and can significantly improve the lithium deposition / stripping efficiency and cycling performance of a new lithium-sulfur battery carrier to meet the requirements of future large-scale energy storage systems for efficient and reliable lithium-sulfur batteries. Summary of the Invention

[0005] In view of the problems of the existing carrier materials for lithium-sulfur batteries, such as single function, polysulfide shuttle effect, and uncontrollable growth of dendrites caused by uneven lithium deposition, the present invention proposes a nitrogen-doped carbon-coated zinc oxide hollow structure material, a preparation method thereof, and an application in lithium-sulfur batteries. The nitrogen-doped carbon-coated zinc oxide hollow structure material serves as a two-way carrier for lithium-sulfur batteries. Using the ZIF-8-coated zinc oxide structure as a precursor, the conversion of ZIF-8-coated zinc oxide to a nitrogen-doped carbon-coated zinc oxide composite structure is achieved through pyrolysis, and then acid selective etching is used to etch out a hollow structure inside, finally forming a hollow heterogeneous structure with hierarchical pores. Zinc oxide exhibits strong Lewis acidity, inhibits the diffusion of polysulfides through Zn-S coordination, and at the same time its lithiophilic property induces the orderly deposition of lithium ions. The hierarchical pore structure of the nitrogen-doped carbon material formed on the surface can provide a high specific surface area loading space for the sulfur cathode, and the polar sites generated by nitrogen doping can effectively anchor polysulfides and inhibit the shuttle effect. Moreover, the hollow structure can provide space for lithium deposition. At the same time, when the obtained material is applied to the lithium-sulfur battery system, it exhibits excellent specific capacity and cycling performance.

[0006] The technical solution of the present invention is as follows:

[0007] A nitrogen-doped carbon-coated zinc oxide hollow structure material, with zinc oxide as the core and nitrogen-doped carbon as the shell, having a cavity between the core and the shell. The diameter of the nitrogen-doped carbon-coated zinc oxide hollow structure is 200-400 nm, the volume ratio of the internal zinc oxide core is 1 / 4-1 / 2, and the hierarchical pores in the nitrogen-doped carbon are connected to the cavity.

[0008] Furthermore, the morphologies of the nitrogen-doped carbon-coated zinc oxide hollow structure and zinc oxide include rod-like or spherical. More specifically, the morphology of the nitrogen-doped carbon-coated zinc oxide hollow structure is rod-like, with a diameter of 150-300 nm.

[0009] The present invention also provides a preparation method of the nitrogen-doped carbon-coated zinc oxide hollow structure material, including the following steps:

[0010] (1) Disperse zinc oxide in an H2O / DMF mixed solution, then add 2-methylimidazole and mix evenly, and transfer it to a polytetrafluoroethylene hydrothermal container for hydrothermal reaction;

[0011] (2) Wash the obtained product and dry it to obtain a ZIF-8-coated zinc oxide material;

[0012] (3) Subject the ZIF-8-coated zinc oxide material to high-temperature carbonization to obtain a nitrogen-doped carbon-coated zinc oxide material;

[0013] (4) The nitrogen-doped carbon-coated zinc oxide material is uniformly dispersed in an aqueous hydrochloric acid solution and reacted for 3 - 12 h. After the reaction, it is washed, filtered, and dried to obtain a nitrogen-doped carbon-coated zinc oxide hollow structure material; the concentration of the aqueous hydrochloric acid solution is 0.02 - 0.1 mol / L.

[0014] Further, in step (1), the volume ratio of H2O / DMF is 1:(1 - 3), and the mass ratio of zinc oxide to 2-methylimidazole is 1:(5 - 10).

[0015] Further, in step (1), the hydrothermal temperature is 70 - 100 °C, and the hydrothermal time is 12 - 24 h.

[0016] Further, in step (3), the temperature of the high-temperature carbonization is 600 - 800 °C, and the time of the high-temperature carbonization is 1 - 4 h.

[0017] Further, in step (4), the mass-volume ratio mg / L of the nitrogen-doped carbon-coated zinc oxide material to the aqueous hydrochloric acid solution is (1 - 3):1.

[0018] Further, the preparation method of the zinc oxide includes mixing zinc nitrate hexahydrate and sodium hydroxide in deionized water, stirring the mixed solution evenly, transferring it to a polytetrafluoroethylene hydrothermal container for solvothermal reaction, washing the obtained product, and drying it to obtain a rod-shaped zinc oxide material.

[0019] Further, in the mixed solution, the concentration of zinc nitrate hexahydrate is 0.01 - 0.05 mol / L, and the concentration of sodium hydroxide is 0.08 - 0.16 mol / L.

[0020] Further, in the preparation of zinc oxide, the hydrothermal temperature is 120 - 140 °C, and the hydrothermal time is 6 - 12 h.

[0021] The present invention also provides an application of the nitrogen-doped carbon-coated zinc oxide hollow structure material in a lithium-sulfur battery.

[0022] Further, the nitrogen-doped carbon-coated zinc oxide hollow structure material serves as a two-way carrier material for the lithium-sulfur battery, and the two-way carrier material serves as a positive sulfur carrier and / or a negative lithium metal carrier.

[0023] Further, sulfur is loaded on the positive electrode by the melt perfusion method, and the nitrogen-doped carbon-coated zinc oxide hollow structure material is mixed with sulfur and melt-perfused at 140 - 180 °C for 12 - 24 h.

[0024] Further, the mass percentage of sulfur in the positive electrode is 60 - 80%.

[0025] Further, the negative electrode is coated with a nitrogen-doped carbon-coated zinc oxide hollow structure material on a copper foil by electrochemically depositing metallic lithium, and it is assembled with a lithium sheet into a half-cell, and deposited at a current density of 0.5-1 mA cm -2 for 5-20 h,

[0026] Further, the lithium capacity in the negative electrode is 5-10 mAh cm -2 of the metallic lithium negative electrode.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention provides a safe and reliable nitrogen-doped carbon-coated zinc oxide hollow structure material, which, as a two-way carrier material, creatively changes the way that traditional materials can only be used as a single electrode carrier. It can not only load elemental sulfur as the positive electrode material but also deposit metallic lithium as the negative electrode material, and this material system shows significant advantages in the positive and negative electrode matching: its surface chemical properties have excellent interfacial compatibility with both the sulfur positive electrode and the lithium negative electrode, and the volume adjustment ability of the hollow structure can simultaneously alleviate the expansion effect of the sulfur positive electrode and the dendrite growth problem of the lithium negative electrode.

[0029] 2. For the hollow structure created by the present invention, the inner cavity surface is uniformly modified with a zinc oxide nanocrystal layer. Utilizing its high lithium affinity characteristics, it induces the preferential directional deposition of metallic lithium inside the cavity. Moreover, zinc oxide exhibits strong Lewis acidity, and through the Zn-S coordination effect, it inhibits the diffusion of polysulfides, and the cavity also provides space for sulfur loading.

[0030] 3. The outer shell layer created by the present invention is composed of a nitrogen-doped carbon material. The hierarchical pore structure formed on its surface provides a high specific surface area loading space for the sulfur positive electrode, can also inhibit the outward growth of dendrites, and also provides a channel for lithium ions to transport into the internal space. The polar sites generated by nitrogen doping can effectively anchor polysulfides and inhibit the shuttle effect.

[0031] 4. Based on the materials prepared by the present invention as the positive and negative electrode carriers of a lithium-sulfur battery, the initial capacity can reach 1002.1 mAh g -1 at 0.5 C, and the capacity after 700 cycles is 599.1 mAh g -1 , and the capacity retention rate is 60%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 are the XRD pictures of zinc oxide, ZIF-8-coated zinc oxide, nitrogen-doped carbon-coated zinc oxide, and nitrogen-doped carbon-coated zinc oxide hollow structure materials prepared in Example 1.

[0033] Figure 2 are the XPS pictures of the nitrogen-doped carbon-coated zinc oxide hollow structure materials prepared in Example 1.

[0034] Figure 3 It is the XPS picture of the nitrogen-doped carbon-coated zinc oxide hollow structure infused with sulfur material prepared in Example 9.

[0035] Figure 4 It is the TEM picture of the nitrogen-doped carbon-coated zinc oxide hollow structure material prepared in Example 1.

[0036] Figure 5 It is the TEM and corresponding EDS spectrum pictures of the nitrogen-doped carbon-coated zinc oxide hollow structure infused with sulfur material prepared in Example 9.

[0037] Figure 6 It is the comparison picture of the Coulombic efficiency cycles of the electrode sheets prepared in Example 1, Comparative Example 1 and Comparative Example 4 at a current density of 1 mA cm -2 , with a deposition cycle capacity of 1 mAh cm -2 .

[0038] Figure 7 It is the comparison picture of the Coulombic efficiency cycles of the electrode sheets prepared in Example 2, 4, 6, 7 and Comparative Example 5 at a current density of 1 mA cm -2 , with a deposition cycle capacity of 1 mAh cm -2 .

[0039] Figure 8 It is the comparison picture of the cycles of the symmetric cells of Example 3 and Comparative Example 3 at a current density of 1 mA cm -2 , with a deposition cycle capacity of 1 mAh cm -2 .

[0040] Figure 9 It is the comparison picture of the cycles of the full cells of Example 8 combined with Example 9 and Comparative Example 2 combined with Comparative Example 3. Detailed implementation mode

[0041] The following makes a detailed description of the present invention through some representative examples, but the present invention is not limited to these examples.

[0042] The assembly methods of the half, symmetric and full cells in the examples are as follows: Inside a glove box, 1 mol / L LiTFSI (the solvent includes dimethylethane and 1,3-dioxolane, with a volume ratio of 1:1) is used as the electrolyte, and a PP membrane is used as the separator to assemble a CR2025 button cell. The electrode sheet is related to the assembled cell.

[0043] Example 1

[0044] This example provides a preparation and testing method for a nitrogen-doped carbon-coated zinc oxide hollow structure material and its electrode sheet. The specific operation steps are as follows:

[0045] Dissolve 3 g of zinc nitrate hexahydrate in 140 mL of deionized water, add 3.2 g of sodium hydroxide, stir evenly for 30 min, then transfer it to a polytetrafluoroethylene inner liner, put on the reactor jacket, and place it in a blast drying oven for hydrothermal reaction. The reaction temperature is 120 °C and the reaction time is 12 h. After the reaction, it is naturally cooled to room temperature, washed, centrifuged, and dried to obtain zinc oxide with a diameter of 100 - 300 nm. Disperse 0.5 g of the obtained zinc oxide in a solution of H2O / DMF (volume ratio 1:3), add 2.5 g of 2-methylimidazole, stir evenly for 30 min, then transfer it to a polytetrafluoroethylene inner liner, put on the reactor jacket, and place it in a blast drying oven for hydrothermal reaction. The reaction temperature is 70 °C and the reaction time is 24 h. After the reaction, it is naturally cooled to room temperature, washed, centrifuged, and dried to obtain ZIF-8-coated zinc oxide material. Place 0.5 g of ZIF-8-coated zinc oxide in a tubular carbonization furnace, under an argon atmosphere, heat it to 700 °C at a heating rate of 3 °C / min, and hold it at this temperature for 2 h, then naturally cool it to room temperature to obtain nitrogen-doped carbon-coated zinc oxide material. Finally, mix 0.2 g of nitrogen-doped carbon-coated zinc oxide with 100 mL of 0.02 mol / L hydrochloric acid and react for 6 h. After the reaction, wash, filter by suction, and dry to obtain nitrogen-doped carbon-coated zinc oxide hollow structure material. Figure 1 XRD pattern of the material prepared in this example. It can be seen that the material shows the peak shape of zinc oxide, while the nitrogen-doped carbon presents an amorphous structure. Figure 2 XPS pattern of the nitrogen-doped carbon-coated zinc oxide hollow structure material prepared in this example. It can be proved that the material contains nitrogen, carbon, and zinc oxide. Figure 4 TEM image of the nitrogen-doped carbon-coated zinc oxide hollow structure material prepared in this example. It can be seen that the nitrogen-doped carbon is on the outside as the shell, and there is also a cavity structure between the internal zinc oxide core and the shell. The volume ratio of the internal zinc oxide core is 1 / 2 - 1 / 4. Mix the obtained material with PVDF binder and coat it on the current collector copper foil, and dry it in vacuum at 100 °C for 12 h. After drying, cut it into electrode sheets with a diameter of 12 mm, use a lithium sheet as the counter electrode, assemble a half-cell for charge-discharge testing, the deposition capacity is 1 mAh cm -2 , the cut-off voltage is 1 V, and the charge-discharge current density is 1 mA cm -2 , and test the cycling Coulomb efficiency.

[0046] Example 2

[0047] The difference from Example 1 is that the mass of 2-methylimidazole is 3 g, and the other conditions are the same.

[0048] Example 3

[0049] The difference from Example 1 is that the mass of 2-methylimidazole is 5 g, and the other conditions are the same.

[0050] Example 4

[0051] The difference from Example 1 is that the carbonization temperature is 600 °C, and the other conditions are the same.

[0052] Example 5

[0053] The difference from Example 1 is that the carbonization temperature is 800 °C, and the other conditions are the same.

[0054] Example 6

[0055] The difference from Example 1 is that the hydrochloric acid concentration is 0.05 mol / L, and the other conditions are the same.

[0056] Example 7

[0057] The difference from Example 1 is that the hydrochloric acid concentration is 0.1 mol / L, and the other conditions are the same.

[0058] Example 8

[0059] This example provides a preparation method for a composite metal lithium negative electrode, and the specific operation steps are as follows:

[0060] Take the electrode sheet of Example 1 as the negative electrode, and metal lithium as the counter electrode to assemble a half-cell. Deposit at a current density of 0.5 mA cm -2 for 10 hours, then disassemble the battery and take out the prepared metal lithium negative electrode with a deposition capacity of 5 mAh cm -2 Assemble the electrode sheet after depositing lithium into a symmetric cell and conduct electrochemical tests at a current density of 1 mA cm -2 with a cyclic deposition / stripping capacity of 1 mAh cm -2 Figure 8 This is the cyclic comparison diagram of the symmetric cell in this example.

[0061] Example 9

[0062] This example provides a preparation method for nitrogen-doped carbon-coated zinc oxide hollow structure infused with sulfur, and the specific operation steps are as follows:

[0063] Take the material prepared in Example 1, mix it with elemental sulfur in a mass ratio of 3:7, transfer it to a small glass bottle, wrap it with three layers of aluminum foil paper, transfer it to a forced-air oven, heat it to 155 °C, and keep it at this temperature for 12 h, then naturally cool it to room temperature to obtain the nitrogen-doped carbon-coated zinc oxide hollow structure infused with sulfur active material, where the mass fraction of sulfur accounts for 70%. Mix it with a conductive agent and a binder to form a slurry, coat it on aluminum foil, and then dry it in vacuum at 60 °C for 12 h. After drying, cut it into circular pieces with a diameter of 10 mm, and match it with Example 8 to form a full cell for electrochemical tests, where the charge-discharge voltage is 1.7 - 2.8 V. Figure 3 ​XPS graph of the nitrogen-doped carbon-coated zinc oxide hollow structure material prepared in this example, from which sulfur can be seen in the material. Figure 5 TEM graph and corresponding EDS picture of the nitrogen-doped carbon-coated zinc oxide hollow structure material prepared in this example, from which sulfur can be seen to be infused into the cavity and the hierarchical pores of the nitrogen-doped carbon. Figure 9 Full cell cycle comparison graph paired with Example 8 in this example.

[0064] Comparative Example 1

[0065] Using a commercial copper current collector as the negative electrode and a lithium sheet as the counter electrode, assemble a half cell for charge and discharge tests. The deposition capacity is 1 mAh cm -2 , the cut-off voltage is 1 V, and the charge and discharge current density is 1 mA cm -2 , and test the cycling Coulomb efficiency.

[0066] Comparative Example 2

[0067] Using a commercial copper current collector as the negative electrode and metallic lithium as the counter electrode, assemble a CR2025 coin cell. Deposit for 10 hours at a current density of 0.5 mA cm -2 , then disassemble the cell to obtain a metallic lithium negative electrode with a deposition capacity of 5 mAh cm -2 . Assemble the electrode sheet after depositing lithium into a symmetric cell and perform electrochemical tests at a current density of 1 mA cm -2 , with a cyclic deposition / stripping capacity of 1 mAh cm -2 .

[0068] Comparative Example 3

[0069] Mix Ketjenblack (KB) and elemental sulfur in a mass ratio of 3:7, transfer it to a glass vial, wrap it with 3 layers of aluminum foil paper, transfer it to a forced-air oven, heat it to 155 °C, and keep it at this temperature for 12 h, then naturally cool it to room temperature to obtain a carbon / sulfur composite material, in which the mass fraction of sulfur is 70%. After mixing it with a conductive agent and a binder to form a slurry and coating it on aluminum foil, vacuum dry it at 60 °C for 12 h. After drying, cut it into a disc with a diameter of 10 mm, and pair it with Comparative Example 2 to form a full cell for electrochemical tests, where the charge and discharge voltage is 1.7 - 2.8 V.

[0070] Comparative Example 4

[0071] Mix the nitrogen-doped carbon-coated zinc oxide material obtained in Example 1 with a PVDF binder and coat it on a copper foil current collector, then vacuum dry it at 100 °C for 12 h. After drying, cut it into an electrode sheet with a diameter of 12 mm. Using a lithium sheet as the counter electrode, assemble a half cell for charge and discharge tests. The deposition capacity is 1 mAh cm -2, the cut-off voltage is 1 V, and the charge-discharge current density is 1 mA cm -2 , and the cycling Coulomb efficiency is tested.

[0072] Comparative Example 5

[0073] The difference from Example 1 is that the hydrochloric acid concentration is 0.5 mol / L, and the internal zinc oxide is completely etched, with the remaining conditions being the same.

[0074] Table 1 shows the comparison of the cycling Coulomb efficiency performance of Examples 1-7 and Comparative Examples 1, 4, and 5, where the number of cycles is the number of cycles with a Coulomb efficiency of more than 90%:

[0075]

[0076] Analysis:

[0077] As can be seen from the above table, the preparation method of the nitrogen-doped carbon-coated zinc oxide hollow structure material proposed by the present invention has significant innovation and practicality. From Examples 1 and Comparative Examples 1, 4, and 5, it can be seen that after partial etching of the material of the present invention, it can not only attract the deposition of metallic lithium, but also provide space for inhibiting dendrite growth, thereby significantly improving its Coulomb efficiency and deposition / stripping times. The highest Coulomb efficiency can reach 99.2%, and the deposition / stripping cycle is more than 800 cycles.

[0078] As Figure 8 shown, the composite metallic lithium anode prepared by depositing metallic lithium on the material of the present invention has a deposition / stripping cycle performance of more than 800 h, while Comparative Example 3 can only reach 150 h, indicating that the material has excellent lithium deposition / stripping reversibility as a carrier of the metallic lithium anode and can meet the requirements of actual battery charge and discharge.

[0079] From the full cell performance of Example 10 combined with Example 11 and Comparative Example 2 combined with Comparative Example 3, it can be seen that due to the uniform modification of the inner cavity surface of the material with a zinc oxide nanocrystal layer, the high lithium-philic property is used to induce the preferential directional deposition of metallic lithium inside the cavity, and the zinc oxide exhibits strong Lewis acidity, and the diffusion of polysulfides is inhibited through the Zn-S coordination effect. The fabricated outer shell layer is composed of a nitrogen-doped carbon material, and the hierarchical pore structure formed on its surface provides a high specific surface area loading space for the sulfur cathode and also provides a channel for lithium ions to transport into the internal space. The polar sites generated by nitrogen doping can effectively anchor polysulfides and inhibit the shuttle effect, thereby improving the performance of the full cell. The initial capacity at 0.5 C can reach 1002.1 mAh g -1 , and the capacity after 700 cycles is 599.1 mAh g -1 , and the capacity retention rate is 60%.

[0080] The above has described the present invention in detail. The purpose is to enable those skilled in this field of technology to understand the content of the present invention and implement it. However, this should not limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A nitrogen-doped carbon-coated zinc oxide hollow structure material, characterized in that: With zinc oxide as the core and nitrogen-doped carbon as the shell, there is a cavity between the core and the shell. The diameter of the nitrogen-doped carbon-coated zinc oxide hollow structure material is 200 - 400 nm, the volume ratio of the internal zinc oxide core is 1 / 4 - 1 / 2, and the multi-level pores in the nitrogen-doped carbon are connected to the cavity.

2. The nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 1, wherein: The morphologies of the nitrogen-doped carbon-coated zinc oxide hollow structure material and zinc oxide include rod-like or spherical shapes.

3. A method for preparing the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 1, characterized in that: It includes the following steps: (1) Disperse zinc oxide in a H2O / DMF mixed solution, then add 2-methylimidazole and mix evenly, and transfer it to a polytetrafluoroethylene hydrothermal container for hydrothermal reaction; (2) Wash the obtained product and dry it to obtain a ZIF-8-coated zinc oxide material; (3) Carbonize the ZIF-8-coated zinc oxide material at high temperature to obtain a nitrogen-doped carbon-coated zinc oxide material; (4) Uniformly disperse the nitrogen-doped carbon-coated zinc oxide material in an aqueous hydrochloric acid solution and react for 3 - 12 h. After the reaction, wash, filter, and dry to obtain the nitrogen-doped carbon-coated zinc oxide hollow structure material; the concentration of the aqueous hydrochloric acid solution is 0.02 - 0.1 mol / L.

4. The preparation method of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 3, wherein: In step (1), the volume ratio of H2O / DMF is 1:(1 - 3), and the mass ratio of zinc oxide to 2-methylimidazole is 1:(5 - 10); and / or, in step (1), the hydrothermal temperature is 70 - 100 °C and the hydrothermal time is 12 - 24 h; and / or, In step (3), the temperature of the high-temperature carbonization is 600 - 800 °C and the time of the high-temperature carbonization is 1 - 4 h.

5. The preparation method of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 3, wherein: In step (4), the mass-volume ratio mg / L of the nitrogen-doped carbon-coated zinc oxide material to the aqueous hydrochloric acid solution is (1 - 3):

1.

6. The preparation method of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 3, characterized in that: The preparation method of the zinc oxide in step (1) includes mixing zinc nitrate hexahydrate and sodium hydroxide in deionized water, stirring the mixed solution evenly, transferring it to a polytetrafluoroethylene hydrothermal container for solvothermal reaction, washing the obtained product, and drying it to obtain a rod-like zinc oxide material.

7. Application of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 1 in a lithium-sulfur battery.

8. Use of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 7 in a lithium-sulfur battery, characterized in that: The nitrogen-doped carbon-coated zinc oxide hollow structure material is used as a two-way carrier material for a lithium-sulfur battery, and the two-way carrier material is used as a positive sulfur carrier and / or a negative lithium metal carrier.

9. The application of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 8 in a lithium-sulfur battery, characterized in that: The positive electrode is loaded with sulfur by the material melt perfusion method. The nitrogen-doped carbon-coated zinc oxide hollow structure material and sulfur are mixed and melt-perfused under the conditions of 140 - 180 °C for 12 - 24 h.

10. The application of the nitrogen-doped carbon-coated zinc oxide hollow structure material according to claim 8 in a lithium-sulfur battery, characterized in that: The negative electrode electrochemically deposits metallic lithium, coats a nitrogen-doped carbon-coated zinc oxide hollow structure material on a copper foil, and assembles it with a lithium sheet into a half-cell, and deposits it for 5-20 h at a current density of 0.5-1.0 mA cm -2 -2.

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