Self-supporting positive electrode carrier material for in-situ growth of VOx-TiO2 heterostructure, preparation and lithium-sulfur battery

Abstract

The invention relates to a self-supporting positive electrode carrier material for in-situ growth of a VOx-coated TiO2 heterostructure, preparation and a lithium-sulfur battery, and belongs to the technical field of lithium-sulfur batteries. The material comprises a self-supporting carbon substrate, a TiO2 nanosheet array growing on the carbon substrate in situ and a VOx nanostructure growing on the TiO2 nanosheet array, and TiO2 and VOx form a heterostructure. Vanadium oxide is introduced to the surface of TiO2 to construct a heterostructure, an interface electric field is established to optimize a material electronic structure, and the adsorption capacity of titanium dioxide to soluble polysulfide and the excellent catalytic characteristic of vanadium oxide are cooperatively utilized. On the basis of establishment of an interface electric field of a heterostructure, regulation of valence states of titanium and vanadium and electronic regulation and control of a heterostructure interface, the catalytic conversion efficiency of lithium polysulfide is improved, so that the shuttle effect is effectively inhibited, and the capacity, rate capability and cycling stability of a lithium-sulfur battery are improved.

Description

Technical Field

[0001] This invention relates to an in-situ grown VO x @TiO2 heterostructure self-supporting cathode carrier material, preparation and lithium-sulfur battery, belongs to the field of lithium-sulfur battery technology. Background Technology

[0002] Lithium-sulfur batteries are considered a potential candidate for next-generation rechargeable batteries due to their high theoretical energy density and low cost. However, in practical applications, lithium-sulfur batteries face the serious challenge of the "shuttle effect," namely the dissolution and diffusion of lithium polysulfides (LiPS) in the electrolyte, leading to loss of active material, capacity decay, and reduced cycle performance. Simultaneously, the electrode processes in lithium-sulfur batteries involve complex multi-electron reactions, including solid-liquid-solid transformations. The resulting solid discharge products, Li₂S₂ and Li₂S, are insulating, causing sluggish electrode reaction kinetics. Their continuous deposition at the electrode reaction interface passivates active sites and triggers rapid capacity decay. The development and utilization of catalytic materials in lithium-sulfur batteries are effective means to improve the kinetics of the electrode processes. In existing technologies, titanium dioxide (TiO₂) has been widely studied and applied as a cathode support material due to its strong adsorption capacity for lithium polysulfides, and it can suppress the shuttle effect to some extent.

[0003] Existing titanium dioxide-based cathode materials have the following problems. Firstly, titanium dioxide has poor electrical conductivity (conductivity <10 at room temperature). -10 The presence of phosphorus dioxide (S / cm) hinders electron transfer in the cathode material. Furthermore, lithium-sulfur batteries involve complex heterogeneous catalytic reactions involving electron transfer, making it difficult for catalysts with a single intrinsic state to meet the demands for improved battery reaction kinetics. Titanium dioxide materials possess excellent polysulfide adsorption capabilities, which can suppress side reactions caused by the dissolution of internal polysulfides during battery reactions. However, its catalytic conversion activity for lithium polysulfides is low, making it difficult to efficiently promote the nucleation and conversion of lithium polysulfides to lithium sulfides. This results in rapid capacity decay and insufficient cycle stability during high-rate charge-discharge or long-term cycling.

[0004] Transition metal compound M n X yTransition metal oxides (M = Ti, Co, V, Ni, etc., X = O, S, N, P, B, etc.) have attracted widespread attention due to their strong chemisorption properties. This is because the polar interface formed by the metal d orbitals and the high electronegativity of nonmetals can significantly enhance the anchoring ability for polysulfides. Through systematic evaluation of the redox potentials of transition metal oxides, the academic community has proposed a "golden rule" based on adsorption intensity classification, dividing materials into three categories: high, medium, and low potentials. High potential materials will lead to irreversible polysulfide formation due to strong adsorption; low potential materials have insufficient adsorption capacity and cannot effectively suppress the shuttle effect; while medium potential materials can achieve reversible adsorption of polysulfides, which can both suppress the shuttle effect and ensure that subsequent reactions can proceed.

[0005] However, in practical applications, it has been found that the effectiveness of these adsorption capacities is affected by the material structure adaptability (such as composite materials, porosity, crystal orientation, and electron transport paths). Meanwhile, transition metal compounds are mostly wide-bandgap semiconductors with generally poor intrinsic conductivity, leading to increased charge transport impedance and exacerbating electrode polarization. During cycling, transition metal compounds can also experience structural collapse, causing deactivation of active sites and even capacity decay. Studies have shown that single-component materials struggle to simultaneously achieve multi-scale reaction characteristics. Therefore, researchers have attempted to construct heterostructures to integrate the sulfur electrode process-promoting properties of different materials, achieving division of labor and synergy among multiple active sites. The heterostructure interface induces a built-in electric field (IEF) through the Fermi level difference between components. This not only drives the directional migration and efficient separation of charge carriers but also suppresses polysulfide diffusion through the electrostatic confinement effect of the space charge layer. Simultaneously, it reconstructs the dp orbital hybridization state at the interface to lower the energy barrier of the sulfur reduction reaction, enhancing polysulfide anchoring ability and promoting Li2S catalytic activity.

[0006] Currently, copper foil and aluminum foil are commonly used as conductive current collectors in commercial applications and research, with active materials and binders coated on top. These non-self-supporting electrode structures face the following problems: First, their mechanical support and conductivity are highly dependent on the metal current collector (such as aluminum or copper foil), leading to a 15%-30% increase in overall battery weight and significantly limiting the potential for energy density improvement. Second, the preparation of composite electrodes requires complex processes such as coating, drying, and rolling, which not only increases production costs (accounting for approximately 8%-12% of the total battery cost) but also reduces product yield due to difficulties in controlling slurry uniformity. Third, during long-term cycling, the difference in volume expansion between the electrode material and the current collector can easily cause interfacial delamination, resulting in a capacity decay rate that is more than 30% higher than that of self-supporting structures. At the same time, cracking causes the utilization rate of active materials to drop below 75%. Finally, rigid substrate materials limit the bending performance of the electrodes (bending radius is generally >5mm), making it difficult to meet the stringent requirements of flexible electronic devices (such as wearable devices) for electrode deformation capabilities (bending radius <1mm).

[0007] By constructing a three-dimensional conductive network to achieve an integrated design of mechanical support and electronic conduction, the need for a current collector can be eliminated, and the manufacturing process can be simplified through in-situ growth, providing an ideal solution for the development of next-generation high-energy-density flexible energy storage devices. In 2023, Yuan Weiyong et al. from Zhejiang University applied for a patent entitled "Graphene-supported nanoporous titanium dioxide lithium-sulfur battery cathode carrier material and its preparation method and lithium-sulfur battery," publication number CN117254028A. This invention discloses a graphene-supported nanoporous titanium dioxide lithium-sulfur battery cathode carrier material, its preparation method, and a lithium-sulfur battery based on this carrier material. This material uses the triblock copolymer Pluronic F127 as a template agent and glycerol as a confining solvent, and is stirred in an oil bath to construct a titanium dioxide nanoporous structure on pristine graphene. However, its electrochemical performance still needs further improvement. Summary of the Invention

[0008] In view of this, the present invention provides an in-situ growth of VO x @TiO2 heterostructure self-supporting cathode carrier material, preparation and lithium-sulfur battery. Introducing vanadium oxide (VO2) onto the TiO2 surface. x ) Construct VO x By using a TiO2 heterostructure to optimize the electronic structure of the material through an interfacial electric field, the adsorption capacity of titanium dioxide for soluble polysulfides and the excellent catalytic properties of vanadium oxide are synergistically utilized. Based on the heterostructure, an interfacial electric field is established to regulate the valence states of titanium and vanadium and the electronic modulation of the heterostructure interface, thereby improving the catalytic conversion efficiency of lithium polysulfides. This effectively suppresses the shuttle effect and enhances the capacity, rate performance, and cycle stability of lithium-sulfur batteries, providing a new technical pathway for the development of high-performance lithium-sulfur batteries.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows.

[0010] An in-situ grown VO x @TiO2 heterostructure self-supporting cathode carrier material, the material comprising a self-supporting carbon substrate, an array of TiO2 nanosheets grown in situ on the carbon substrate, and VO2 grown on the TiO2 nanosheet array. x Nanostructures, TiO2 and VO x It forms a heterogeneous structure.

[0011] Preferably, the self-supporting carbon substrate includes carbon cloth or carbon paper.

[0012] Preferably, the heterostructure is V2O3@TiO2, VO2@TiO2, or V2O5@TiO2.

[0013] An in-situ grown VO according to the present invention x The preparation method of self-supported cathode carrier material with TiO2 heterostructure includes the following steps:

[0014] (1) Immerse the self-supporting carbon substrate in concentrated hydrochloric acid (concentration of 36% to 38%) for 12 to 16 hours to generate oxidation sites for nanoarray growth, and obtain a carbon substrate containing active sites.

[0015] (2) After mixing isopropyl titanate, diethylenetriamine and isopropanol evenly, the mixture is immersed in a carbon substrate containing active sites and kept at 180-200℃ for 16-24h. After the reaction is completed, the carbon substrate with TiO2 generated in situ is dried.

[0016] (3) Vanadium triisopropoxy oxide and isopropanol were mixed and immersed into a carbon substrate in situ to generate TiO2. The mixture was kept at 180-200℃ for 8-12 hours. After the reaction was completed, the substrate was dried to obtain the in situ grown TiO2. x And TiO2 carbon substrate;

[0017] (4) In situ growth of VO x A carbon substrate containing TiO2 is calcined in a tube furnace at 400-450℃ for 8-10 hours to obtain in-situ grown VO2. x @TiO2 heterostructure self-supporting cathode carrier material.

[0018] Preferably, the area of ​​the carbon substrate in step (1) to the volume ratio of isopropyl titanate, diethylenetriamine, and isopropanol in step (2) is 9 cm². 2 :1.5-2.5mL: 30-50μL: 40mL.

[0019] Preferably, the area of ​​the carbon substrate in step (1) to the volume ratio of vanadium triisopropoxylate and isopropanol in step (3) is 9 cm². 2 200-500μL: 30mL.

[0020] Preferably, in step (4), calcination is carried out under an argon atmosphere to obtain a self-supporting cathode material with an in-situ grown VO2@TiO2 heterostructure;

[0021] Alternatively, calcination under a mixed atmosphere of argon and hydrogen can yield a self-supporting cathode material with an in-situ grown V2O3@TiO2 heterostructure.

[0022] Alternatively, calcination in air can yield a self-supporting cathode material with an in-situ grown V2O5@TiO2 heterostructure.

[0023] Preferably, in the mixed atmosphere of argon and hydrogen, the volume fraction of hydrogen is 5%-8%.

[0024] A lithium-sulfur battery, wherein the positive electrode material of the battery is the in-situ grown VO as described in this invention. xThe material obtained by loading sulfur onto a self-supporting cathode carrier material with a TiO2 heterostructure.

[0025] Preferably, the loading of elemental sulfur in the self-supporting positive electrode carrier material is 1-5 mg per square centimeter.

[0026] Beneficial effects

[0027] This invention provides an in-situ grown VO x @TiO2 heterostructure self-supporting cathode support material. This material consists of a self-supporting carbon substrate and VO2 grown in situ on it. x @Heterogeneous structure composition, relying on the strong adsorption of lithium polysulfides by TiO2, VO x Its excellent catalytic conversion activity and the synergistic electronic regulation effect of the heterogeneous interface effectively suppress the shuttle effect of lithium-sulfur batteries, improve performance, and can be directly loaded with sulfur as a positive electrode. The process is simple and suitable for flexible battery manufacturing.

[0028] The method described in this invention employs a two-step solvothermal approach. First, a self-supporting carbon substrate is immersed in concentrated hydrochloric acid to generate oxidation sites. Then, two separate solvothermal reactions are performed to grow TiO2 and VO2, respectively. X A heterostructure was obtained, and finally calcined to obtain a self-supported cathode material based on the titanium dioxide-vanadium oxide heterostructure. Further high-temperature calcination under different calcination atmospheres (argon, argon / hydrogen mixture, air) yielded materials with different VO values. x Self-supporting cathode carrier materials with @TiO2@CC heterostructures (V2O3@TiO2@CC, VO2@TiO2@CC, V2O5@TiO2@CC).

[0029] Load VO x The use of TiO2@CC heterostructure materials filled with sulfur as a positive electrode in lithium-sulfur batteries can effectively improve the capacity, rate performance, and cycle stability of lithium-sulfur batteries. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention. The illustrative embodiments of the invention and the accompanying drawings are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 This is a physical image of VO2@TiO2@CC prepared in Example 1 of the present invention.

[0032] Figure 2 The XRD pattern of VO2@TiO2@CC prepared in Example 1 of this invention.

[0033] Figure 3 The image shown is a SEM image of VO2@TiO2@CC prepared in Example 1 of this invention.

[0034] Figure 4 The image is an HRTEM image of VO2@TiO2@CC prepared in Example 1 of this invention.

[0035] Figure 5 XPS spectrum of VO2@TiO2@CC prepared in Example 1 of this invention.

[0036] Figure 6 This refers to the rate performance of the lithium-sulfur battery in Example 1 of the present invention.

[0037] Figure 7 The cycling performance of the lithium-sulfur battery in Example 1 of this invention at 0.5C is shown.

[0038] Figure 8 The cycling performance of the lithium-sulfur battery in Example 1 of the present invention at 1C. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments.

[0040] In a first aspect, the present invention proposes an in-situ growth method for VO x @TiO2 heterostructure self-supporting cathode support material, which includes a self-supporting carbon substrate and VO x @TiO2 heterostructure, the heterostructure is grown in situ on the surface of a carbon substrate. Firstly, the carbon substrate has large porosity and specific surface area, which can be used for VOCs. x The TiO2 heterostructure provides ample growth sites and can effectively load sulfur (S8) and sulfides (Li2S). x The high flexibility of carbon materials, including positive electrode active materials such as TiO2, can reduce volume changes during cycling. Furthermore, this material combines the strong adsorption capacity of TiO2 for lithium polysulfides and VOCs... x The excellent catalytic conversion activity and synergistic electronic regulation at the heterogeneous interface effectively suppress the shuttle effect in lithium-sulfur batteries, improving the battery's specific capacity, rate performance, and cycle stability. This material can be directly loaded with sulfur and used as a cathode in lithium-sulfur batteries, which is simpler than the traditional lithium-sulfur battery cathode synthesis process, avoids the use of organic solvents and binders, and can also be used in the manufacture of flexible batteries.

[0041] A second aspect of the present invention provides an in-situ growth method for VO x A method for preparing a self-supported cathode support material with a TiO2 heterostructure. This method involves in-situ growth of VO2 on a self-supported carbon substrate using a two-step solvothermal method. x @TiO2 heterostructure, followed by heat treatment and calcination to adjust vanadium oxide (VO) x The chemical valence state of ).

[0042] A third aspect of the invention provides a lithium-sulfur battery with the aforementioned load VO x @TiO2 heterostructure self-supporting positive electrode carrier material is filled with sulfur and used as positive electrode material, and assembled with battery shell, separator, electrolyte, negative electrode sheet, etc. to form coin lithium sulfur battery or pouch battery.

[0043] Furthermore, the positive electrode material is cut into circular electrode sheets with a diameter of 12 mm, and 1-5 mg of elemental sulfur is uniformly loaded per square centimeter of this positive electrode material. The battery casing used is a CR2032 coin cell casing. The negative electrode sheet used is a lithium metal sheet. The separator used is a Celgard 2325 commercial separator. The electrolyte used is a mixed solution of DME:DOL (volume ratio 1:1) with 1 M LiTFSI dissolved and 1.0% LiNO3 added. The electrolyte addition amount for each battery is 20-60 μL, and they are assembled into coin cells.

[0044] The positive electrode material was cut into 9cm × 6cm pouch plates, with a 1cm × 1cm tab reserved. 6mg of elemental sulfur was uniformly loaded onto each square centimeter of this positive electrode material. The negative electrode used was a 100mm thick lithium strip, 9cm × 6cm in size. The separator used was a commercially available Celgard 2325 separator. Aluminum and nickel tabs were welded to the positive and negative electrodes respectively; the aluminum-plastic film was 100mm thick with a 4mm indentation depth. When assembling the pouch battery, five positive electrodes and eight lithium strips were used for the negative electrode, with a total electrolyte volume of 8mL.

[0045] The methods used for material characterization in this invention are as follows:

[0046] The phase composition of VO2@TiO2@CC was characterized by X-ray diffraction (XRD, Ultima IV); its microstructure was studied by high-resolution field emission transmission electron microscopy (HRTEM, JEM-2010F) and scanning electron microscopy (SEM, QUANTA-250); and its bonding and valence states were analyzed by X-ray photoelectron spectroscopy (XPS, Thermo Scientific ESCALAB Xi+).

[0047] Example 1

[0048] (1) Cut carbon cloth (CC) into 3cm×3cm size, soak it in concentrated hydrochloric acid for 12h, wash it with water and dry it for later use.

[0049] (2) Take 1.8 mL of isopropyl titanate and 40 mL of diethylenetriamine, and add 40 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth in the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200°C for 24 h. Then remove the carbon cloth and dry it in an oven at 60°C for 4 h.

[0050] (3) Take 200 mL of triisopropoxyvanadium oxide and add 30 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth obtained in step (2) into the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200 °C for 12 h. Then take out the carbon cloth and dry it in an oven at 60 °C for 4 h.

[0051] (4) The carbon cloth obtained in step (3) is placed in a tube furnace and heated to 400℃ at 5℃ / min under an argon atmosphere, and held for 10h. This causes TiO2 to form anatase phase and VO2 to form monoclinic B phase. Finally, a self-supporting cathode material with a VO2@TiO2 heterostructure is obtained, named VO2@TiO2@CC.

[0052] (5) Immerse VO2@TiO2@CC in a sulfur-containing carbon disulfide solution (20 mg / mL), remove and dry after 5 min, and melt and fill with sulfur at 155℃ for 12 h to obtain a self-supporting positive electrode sheet with a VO2@TiO2 heterostructure, and assemble it into a lithium-sulfur battery.

[0053] The prepared VO2@TiO2@CC was analyzed by XRD, and the results are shown in the figure. Figure 2 Peaks corresponding to TiO2 and VO2 were observed. Figure 3 The SEM images revealed a uniform and porous nanosheet array structure, which effectively contacts the electrolyte and active material, promotes ion and electron transport, and enhances the kinetics of the electrode process. This indicates that VO2 nanostructures were successfully grown on the surface of the TiO2 nanosheet array, forming a hierarchical structure. High-resolution transmission electron microscopy (HRTEM) analysis further revealed the microstructure of the material. Figure 4 The image shows an HRTEM image of the VO2@TiO2@CC material, revealing its high-resolution crystal structure. The measured lattice spacings are 0.35 nm and 0.60 nm, corresponding to the (101) crystal plane of TiO2 and the (002) crystal plane of VO2. The interface between the VO2 and TiO2 lattice stripes is clearly visible, confirming the successful growth of VO2 on TiO2.

[0054] The chemical states of Ti and V were then investigated using X-ray photoelectron spectroscopy (XPS). Further analysis... Figure 5 When viewing the high-resolution XPS spectra presented in a, b, c, and d, significant changes in peak positions can be clearly observed. Figure 5 In the original Ti 2p spectrum of TiO2@CC (a), the Ti 2p3 / 2 and Ti 2p1 / 2 peaks have specific initial positions. However, in Figure 5In c(VO2@TiO2@CC), peak shifts can be observed: the Ti 2p3 / 2 peak shifts from its original position to approximately 458.5 eV, the Ti 2p1 / 2 peak shifts to approximately 464.1 eV, and an additional Ti peak appears at approximately 457.2 eV and 462.3 eV. 3+ The negative shift of the Ti peak in the VO2@TiO2@CC spectrum compared to the original Ti 2p spectrum indicates a decrease in electron density around Ti atoms in the heterostructure. Similarly, for the V 2p spectrum, in Figure 5 In b (the original V 2p spectrum), the V 2p3 / 2 and V 2p1 / 2 peaks have initial positions. However, Figure 5 In d, a positive shift occurred: the V 2p3 / 2 peak shifted to V 5+ Approximately 517.3 eV and V 4+ The peak is approximately 516.1 eV, while the V 2p1 / 2 peak shifts to V. 5+ Approximately 524.5 eV and V 4+ The value is approximately 523.2 eV. Compared to the original V 2p spectrum, the positive shift of the V peak in the VO2@TiO2@CC spectrum indicates an increase in the electron density around the V atom. The negative shift of the Ti peak and the positive shift of the V peak in the VO2@TiO2@CC spectrum together indicate the transfer of electrons from Ti to V in the heterostructure.

[0055] The rate performance of the battery was tested using the Neware battery testing system (CT-4008, Shenzhen, China) within a voltage range of 1.7–2.8V. The results are as follows: Figure 6 As shown, the cycle performance test results are as follows: Figure 7 and Figure 8 As shown.

[0056] Example 2

[0057] (1) Cut the carbon paper (CP) into 3cm×3cm size, soak it in concentrated hydrochloric acid for 12h, wash it with water and dry it for later use.

[0058] (2) Take 1.8 mL of isopropyl titanate and 40 mL of diethylenetriamine, and add 40 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon paper in the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200°C for 24 h. Then remove the carbon paper and dry it in an oven at 60°C for 4 h.

[0059] (3) Take 200 mL of triisopropoxyvanadium oxide and add 30 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon paper obtained in step (2) into the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200°C for 12 h. Then take out the carbon paper and dry it in an oven at 60°C for 4 h.

[0060] (4) The carbon paper obtained in step (3) is placed in a tube furnace and heated to 400℃ at 5℃ / min under an argon atmosphere, and held for 10h. This causes TiO2 to form anatase phase and VO2 to form monoclinic B phase. Finally, a self-supporting cathode material with a VO2@TiO2 heterostructure is obtained, named VO2@TiO2@CP.

[0061] (5) Immerse VO2@TiO2@CP in a sulfur-containing carbon disulfide solution (20 mg / mL), remove and dry after 5 min, and melt and fill with sulfur at 155℃ for 12 h to obtain a self-supporting positive electrode sheet with a VO2@TiO2 heterostructure, and assemble it into a lithium-sulfur battery.

[0062] The battery was cycle-tested using the Neware battery testing system within a voltage range of 1.7–2.8V, and the initial capacity at 0.5C was 1236 mAg. -1 After 200 cycles, the value remained at 833 mg. -1 The average decay rate per lap is 0.016%.

[0063] Example 3

[0064] (1) Cut the carbon cloth into 3cm×3cm size, soak it in concentrated hydrochloric acid for 12h, wash it with water and dry it for later use.

[0065] (2) Take 2.4 mL of isopropyl titanate and 40 mL of diethylenetriamine, and add 40 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth in the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200°C for 24 h. Then remove the carbon cloth and dry it in an oven at 60°C for 4 h.

[0066] (3) Take 200 mL of triisopropoxyvanadium oxide and add 30 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth obtained in step (2) into the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200 °C for 12 h. Then take out the carbon cloth and dry it in an oven at 60 °C for 4 h.

[0067] (4) The carbon cloth obtained in step (3) is placed in a tube furnace and heated to 400℃ at 5℃ / min under an argon atmosphere, and held for 10h. This causes TiO2 to form anatase phase and VO2 to form monoclinic B phase. Finally, a self-supporting cathode material with a VO2@TiO2 heterostructure is obtained, named VO2@TiO2@CC.

[0068] (5) Immerse VO2@TiO2@CC in a sulfur-containing carbon disulfide solution (20 mg / mL), remove and dry after 5 min, and melt and fill with sulfur at 155℃ for 12 h to obtain a self-supporting positive electrode sheet with a VO2@TiO2 heterostructure, and assemble it into a lithium-sulfur battery.

[0069] The battery was cycle-tested using the Neware battery testing system within a voltage range of 1.7–2.8V, and the initial capacity at 0.5C was 1147 mA g. -1 After 200 cycles, the pressure remained at 784 mA g. -1 The average decay rate per lap is 0.016%.

[0070] Example 4

[0071] (1) Cut carbon cloth (CC) into 3cm×3cm size, soak it in concentrated hydrochloric acid for 12h, wash it with water and dry it for later use.

[0072] (2) Take 1.8 mL of isopropyl titanate and 40 mL of diethylenetriamine, and add 40 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth in the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200°C for 24 h. Then remove the carbon cloth and dry it in an oven at 60°C for 4 h.

[0073] (3) Take 200 mL of triisopropoxyvanadium oxide and add 30 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth obtained in step (2) into the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200 °C for 12 h. Then take out the carbon cloth and dry it in an oven at 60 °C for 4 h.

[0074] (4) The carbon cloth obtained in step (3) is placed in a tube furnace and heated to 400℃ at a rate of 5℃ / min under a hydrogen / argon mixed atmosphere (6% hydrogen), and held for 10h. This causes TiO2 to form the anatase phase and VO2 to form the monoclinic B phase. Finally, a self-supporting cathode material with a V2O3@TiO2 heterostructure is obtained, named V2O3@TiO2@CC.

[0075] (5) Immerse V2O3@TiO2@CC in a sulfur-containing carbon disulfide solution (20 mg / mL), remove and dry after 5 min, and melt and fill with sulfur at 155℃ for 12 h to obtain a self-supporting positive electrode sheet with a V2O3@TiO2 heterostructure, and assemble it into a lithium-sulfur battery.

[0076] The battery was cycle-tested using the Neware battery testing system within a voltage range of 1.7–2.8V, and the initial capacity at 0.5C was 1323 mA g. -1 After 200 cycles, maintain 845 mA g. -1 The average decay rate per lap is 0.018%.

[0077] Example 5

[0078] (1) Cut the carbon cloth into 3cm×3cm size, soak it in concentrated hydrochloric acid for 12h, wash it with water and dry it for later use.

[0079] (2) Take 1.8 mL of isopropyl titanate and 40 mL of diethylenetriamine, and add 40 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth in the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200°C for 24 h. Then remove the carbon cloth and dry it in an oven at 60°C for 4 h.

[0080] (3) Take 200 mL of triisopropoxyvanadium oxide and add 30 mL of isopropanol to prepare a homogeneous solution. Immerse the carbon cloth obtained in step (2) into the above solution, transfer it to a closed polytetrafluoroethylene reactor, and react at 200 °C for 12 h. Then take out the carbon cloth and dry it in an oven at 60 °C for 4 h.

[0081] (4) The carbon cloth obtained in step (3) is placed in a tube furnace and heated to 400℃ at 5℃ / min under air atmosphere, and held for 10h. This causes TiO2 to form anatase phase and VO2 to transform into V2O5 orthorhombic phase. Finally, a self-supporting cathode material with a V2O5@TiO2 heterostructure is obtained, named V2O5@TiO2@CC.

[0082] (5) Immerse V2O5@TiO2@CC in a sulfur-containing carbon disulfide solution (20 mg / mL), remove and dry after 5 min, and melt and fill with sulfur at 155℃ for 12 h to obtain a self-supporting positive electrode sheet with a V2O5@TiO2 heterostructure, and assemble it into a lithium-sulfur battery.

[0083] The battery was cycle-tested using the Neware battery testing system within a voltage range of 1.7–2.8V, and the initial capacity at 0.5C was 1156 mAg. -1 After 200 cycles, maintain 806 mA g. -1 The average decay rate per lap is 0.015%.

[0084] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. An in-situ grown VO x @TiO2 heterostructure self-supporting cathode carrier material, characterized in that: The material includes a self-supporting carbon substrate, a TiO2 nanosheet array grown in situ on the carbon substrate, and VO grown on the TiO2 nanosheet array. x Nanostructures, TiO2 and VO x It forms a heterogeneous structure.

2. An in-situ grown VO as described in claim 1 x @TiO2 heterostructure self-supporting cathode carrier material, characterized in that: The self-supporting carbon substrate includes carbon cloth and carbon paper.

3. An in-situ grown VO as described in claim 1 or 2 x @TiO2 heterostructure self-supporting cathode carrier material, characterized in that: The heterostructure is V2O3@TiO2, VO2@TiO2, or V2O5@TiO2.

4. An in-situ grown VO according to any one of claims 1 to 3 x A method for preparing a self-supporting cathode carrier material with a TiO2 heterostructure, characterized in that: The method steps include: (1) Soak the self-supporting carbon substrate in concentrated hydrochloric acid for 12-16 hours to obtain a carbon substrate containing active sites; (2) After mixing isopropyl titanate, diethylenetriamine and isopropanol evenly, the mixture is immersed in a carbon substrate containing active sites and kept at 180-200℃ for 16-24h. After the reaction is completed, the carbon substrate with TiO2 generated in situ is dried. (3) Vanadium triisopropoxy oxide and isopropanol were mixed and immersed into a carbon substrate in situ to generate TiO2. The mixture was kept at 180-200℃ for 8-12 hours. After the reaction was completed, the substrate was dried to obtain the in situ grown TiO2. x And TiO2 carbon substrate; (4) In situ growth of VO x The carbon substrate containing TiO2 was calcined in a tube furnace at 400-450℃ for 8-10 hours to obtain in-situ grown VO2. x @TiO2 heterostructure self-supporting cathode carrier material.

5. The in-situ growth of VO as described in claim 4 x A method for preparing a self-supporting cathode carrier material with a TiO2 heterostructure, characterized in that: The area of ​​the carbon substrate in step (1) and the volume ratio of isopropyl titanate, diethylenetriamine, and isopropanol in step (2) are 9 cm². 2 :1.5-2.5mL: 30-50μL: 40mL.

6. The in-situ growth of VO as described in claim 4 x The preparation method of the self-supported cathode carrier material with a TiO2 heterostructure, in step (1), the area of ​​the carbon substrate and the volume ratio of vanadium triisopropoxy oxide and isopropanol in step (3) are: 9 cm². 2 200-500μL: 30mL.

7. The in-situ growth of VO as described in claim 4 x The preparation method of the self-supporting positive electrode carrier material of @TiO2 heterostructure, in step (4), calcination is carried out under argon atmosphere to obtain the self-supporting positive electrode carrier material of in-situ grown VO2@TiO2 heterostructure; Alternatively, calcination under a mixed atmosphere of argon and hydrogen can yield a self-supporting cathode material with an in-situ grown V2O3@TiO2 heterostructure. Alternatively, calcination in air can yield a self-supporting cathode material with an in-situ grown V2O5@TiO2 heterostructure.

8. The in-situ grown VO as described in claim 7 x The preparation method of self-supporting cathode carrier material with TiO2 heterostructure involves a mixed atmosphere of argon and hydrogen, with the volume fraction of hydrogen being 5%-8%.

9. A lithium-sulfur battery, characterized in that: The positive electrode material of the battery is the in-situ grown VO as described in any one of claims 1 to 3. x The material obtained by loading sulfur onto a self-supporting cathode carrier material with a TiO2 heterostructure.

10. A lithium-sulfur battery as described in claim 9, characterized in that: The loading of elemental sulfur per square centimeter of the self-supporting positive electrode carrier material is 1-5 mg.

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