A sulfur-based composite cathode material and its preparation method

Abstract

The present invention belongs to the field of new materials and new energy, and particularly relates to a sulfur-based composite cathode material and a preparation method thereof. The material is a sulfur-based composite material using vanadate or carbon / vanadate as a carrier material, and the chemical formula of the vanadate is A x V y O z (where 1

Description

Technical Field

[0001] The present invention belongs to the field of new materials, and particularly relates to a sulfur-based composite cathode material and a preparation method thereof. Background Art

[0002] The contradiction between the increasing global energy demand and carbon emission control has made the development of renewable energy an inevitable trend, and the research on energy storage systems has become a key point. Lithium-ion batteries have been favored due to their high voltage, low self-discharge rate, no memory effect, long cycle life, etc., and have been widely used in electronic products, electric vehicles, medical devices and other fields. However, limited by the relatively low theoretical specific capacity of electrode materials, it is difficult to significantly improve the energy density of lithium-ion batteries, and it is increasingly difficult to meet people's needs. Therefore, the development of new high-energy secondary batteries is extremely urgent. Lithium-sulfur batteries have a theoretical energy density (2600 Wh kg -1 ) and a theoretical specific capacity (1675 mAh g -1 ) several times that of lithium-ion batteries. In addition, as the electrode material, elemental sulfur has the advantages of rich reserves and low price. Therefore, lithium-sulfur batteries are considered to be one of the most promising high-energy secondary batteries.

[0003] At present, there is still a large gap between the actual energy density of lithium-sulfur batteries and their practical application, which is mainly due to the following inherent problems of sulfur cathodes: First, due to the large density difference between sulfur and Li2S, the volume change rate of sulfur cathodes during charge and discharge is close to 80%, which easily causes adverse consequences such as pulverization of electrode materials and damage to electrode structures. Second, the insulating properties of sulfur and lithium (di) sulfide (Li2S2 / Li2S) reduce the ion and electron transfer efficiency during the electrochemical reaction process of the electrode, resulting in slow electrochemical kinetics of the sulfur cathode, and thus low utilization rate of active substances, which is not conducive to the long-term stable cycling of the battery. In addition, soluble intermediate products (polysulfides) generated during the reaction of sulfur will shuttle back and forth between the positive and negative electrodes, resulting in a large loss of active substances in the sulfur cathode, the inability to complete the battery charging process smoothly, and a serious reduction in the charge-discharge efficiency of the battery.

[0004] In view of the above problems, those skilled in the art have proposed various solutions from different perspectives such as cathode materials, electrolyte additives, and separator modification. Among them, preparing sulfur-based composite cathodes is a common method. For example, porous carbon is used as a carrier material to be combined with sulfur to prepare sulfur-based composites. The rich pore structure of carbon materials is utilized to physically adsorb intermediate polysulfide lithium products, and with its good electrical conductivity, the charge transfer process is further accelerated. However, the physical adsorption of soluble intermediate polysulfide lithium products by carbon-based carrier materials is weak, and sulfur / carbon composites still have problems such as rapid capacity decay and low Coulomb efficiency during long-term cycling. In particular, the tap density of carbon-based materials is relatively low, which greatly reduces the volumetric energy density of sulfur / carbon composites. Subsequently, researchers introduced polar metal compounds and polymers as carriers into sulfur cathodes to prepare sulfur-based composites, hoping to utilize their chemical adsorption to adsorb polysulfide lithium, slow down the shuttle effect, and catalyze the electrochemical conversion of sulfur. However, currently, sulfur-based composites still face the problem of low energy density, mainly due to the following two reasons. Firstly, a large amount of non-electrochemically active carrier materials are added to the cathode, resulting in a low proportion of active cathode materials; in addition, existing sulfur-based composites still have problems such as slow electrochemical kinetics, low utilization rate of active materials, and severe shuttle effect.

[0005] Therefore, whether high-energy-density and excellent cycling performance sulfur-based composites can be obtained has become an urgent problem to be solved in this field. Summary of the Invention

[0006] In view of the many deficiencies of the prior art, the present invention provides a sulfur-based composite cathode material and a preparation method thereof. The material is a sulfur-based composite using vanadate or carbon / vanadate as a carrier material. When used in a lithium-sulfur battery, the sulfur-based composite has a high specific capacity, energy density, and excellent cycling performance.

[0007] The theoretical basis of the present invention is as follows:

[0008] The vanadate carrier has lithium storage activity, which can increase the proportion of active materials in the cathode of a lithium-sulfur battery and contribute additional capacity; at the same time, the electrochemical activity of the vanadate can enable it to combine and rapidly transport lithium ions during the electrode electrochemical reaction process, thereby accelerating the electrochemical reaction process of the sulfur cathode; in addition, the vanadate or carbon / vanadate carrier material has a good polar adsorption effect on intermediate polysulfide lithium products, which can slow down the shuttle effect and catalyze the electrochemical conversion of sulfur, thereby improving the sulfur utilization rate of the sulfur cathode under practical conditions. At the same time, vanadate has a relatively high tap density (>2.0 g cm -3 )), which can increase the tap density of the sulfur-based composite, thereby increasing the volumetric energy density of the electrode. Therefore, the sulfur-based composite provided by the present invention has the characteristics of high mass / volume energy density.

[0009] Under the guidance of the above theory, the specific technical solution of the present invention is as follows:

[0010] A sulfur-based cathode composite material, which is composed of elemental sulfur and a vanadate carrier or a carbon / vanadate composite carrier; wherein the sulfur is one or more of sublimed sulfur, precipitated sulfur, refined sulfur, and nano sulfur; and its content is 50-95 wt% of the entire composite material;

[0011] The vanadate carrier is A x V y O z (1 < x < 3, 1 < y < 3, 3 < z < 8) or several of them, where A is one or more of Bi, In, Al, Fe, Ni, Co, Ca, Zn, Mn, Mg, Cu, Ag, Li, Na, Nb, Ti.

[0012] The above vanadate can be a single-metal vanadate or a multi-metal vanadate, that is, A can be one or more of the above metals; at the same time, the carrier can be a composite of multiple metal vanadates, and they can all achieve the same or similar technical effects;

[0013] The above vanadate carrier or carbon / vanadate composite carrier has lithium storage activity within the charge and discharge voltage window (1.7-2.8V) of the lithium-sulfur battery and can contribute capacity as an active material. At the same time, the vanadate carrier can quickly combine and transport lithium ions during the charge and discharge process of the lithium-sulfur battery, promote the electrode electrochemical reaction process, and limit the shuttle effect of polysulfide intermediate products;

[0014] The carbon in the carbon / vanadate composite carrier is one or more of carbon nanotubes (tube diameter 0.6-200nm), graphene, carbon nanofibers (tube diameter less than 500nm), and porous carbon. The carbon can form a good conductive network, and the vanadate content in the composite carrier is 5-95 wt%.

[0015] The inventor also provides a synthesis method of a vanadate carrier material, and the specific steps are as follows:

[0016] 1-10 mmol of nitrate is dissolved in 4-40 mL of ethylene glycol at 50°C-100°C, and 1-10 mmol of ammonium metavanadate is dissolved in 4-40 mL of deionized water at 50°C-100°C. The ammonium metavanadate aqueous solution is dropped into the nitrate ethylene glycol solution using a peristaltic pump (dropwise addition rate 0.1-1 mL / min). The reaction process is kept under vigorous stirring, and the whole reaction is carried out in a reflux device. After dropping, continue stirring for 10-60 min, and then the obtained precipitate is washed with deionized water and absolute ethanol. The washed precipitate is placed in an oven at 50-100°C and dried for 10-24 h to obtain the product;

[0017] The particle size of the vanadate carrier prepared by the above method is between 0.5 μm and 5.0 μm, and the vanadates all have a relatively high tapped density (>2.0 g m -3 ).

[0018] The preparation method of the carbon / vanadate composite carrier is as follows:

[0019] Put 0.1 - 0.5 g of carbon material into 4 - 40 mL of ethylene glycol at 50°C - 100°C, ultrasonic for 10 - 30 min, then dissolve 1 - 10 mmol of nitrate in the above solution in proportion, and then the carbon / vanadate composite carrier can be prepared in the same manner as the above steps.

[0020] The preparation method of the sulfur-based cathode composite material of the present invention can specifically adopt the melting method, chemical precipitation method, vapor deposition method, dissolution-crystallization method.

[0021] The melting method is to grind a certain mass of carrier material and elemental sulfur (sulfur content 500 - 95 wt%) in an agate mortar for 20 - 60 min, then put it into a crucible wrapped with tin foil, keep it warm at 100 - 200°C for 10 - 24 h. After heating and returning to room temperature, put the product into the agate mortar again and grind it for 20 - 60 min to finally obtain a sulfur-based composite cathode material with vanadate as the carrier.

[0022] The chemical deposition method is to dissolve 0.1 - 10 g of polyvinylpyrrolidone (PVP) in 10 - 500 mL of water to prepare a PVP aqueous solution. Then dissolve 0.01 - 1 mol of sodium thiosulfate pentahydrate in proportion in 100 - 500 mL of PVP aqueous solution. After thoroughly grinding 0.1 - 10 g of vanadate or carbon / vanadate composite carrier, slowly add it to the above solution and ultrasonic for 1 - 10 h. Prepare 1 - 10 wt% dilute hydrochloric acid, and use a peristaltic pump (drip rate 0.1 - 1 mL / min) to slowly drip the dilute hydrochloric acid into the ultrasonicated mixed liquid. Keep stirring vigorously during the dripping process. After dripping, continue to stir for 1 - 10 h. Then wash the obtained precipitate with deionized water and absolute ethanol, put the washed precipitate into an oven at 60 - 200°C and dry it for 10 - 24 h. After cooling to room temperature, take out the product and grind it in an agate mortar for 20 - 60 min to finally obtain a sulfur-based composite cathode material with vanadate as the carrier.

[0023] The above methods can all be completed by existing technologies, but preferably adopt the above two methods, and the inventors will not elaborate on other methods here.

[0024] After obtaining the above sulfur-based cathode composite material, the inventor also provided its application in the preparation of lithium-sulfur batteries. The specific solution is as follows: A lithium-sulfur battery is obtained by using a carrier material or a sulfur-based composite material as the cathode material, metallic lithium as the anode, and DOL / DME as the electrolyte, and its electrochemical performance is tested. The specific assembly process is a conventional technique, and the inventor will not elaborate further.

[0025] The lithium-sulfur battery prepared by the above materials and methods exhibits excellent electrochemical performance and can achieve a high energy density. For example, the lithium-sulfur battery assembled with the sulfur-based composite material using carbon nanotubes / bismuth vanadate as the carrier has an initial discharge specific capacity of 1056.4 mAh g -1 at 0.2C, and the discharge specific capacity is 827.45 mAh g -1 after 100 cycles, and the capacity retention rate is 78.33%.

[0026] In summary, for the sulfur-based cathode composite material provided by the present invention, the vanadate therein has lithium storage activity within the charge-discharge voltage range of the lithium-sulfur battery and can contribute capacity as an electrochemically active substance; since the provided vanadate can bind and transport lithium ions, it can catalyze the electrochemical conversion process of sulfur and thus improve the utilization rate of active sulfur in the cathode; the vanadate has a good polar adsorption effect on polysulfides, thereby achieving the purpose of restricting the shuttle effect; the provided sulfur-based composite material has a high specific capacity and cycle stability. Description of the Drawings

[0027] Figure 1 SEM image of bismuth vanadate prepared in Example 1;

[0028] Figure 2 Battery cycle performance graph of bismuth vanadate prepared in Example 1 as the cathode material;

[0029] Figure 3 Initial charge-discharge curve of the sulfur-based composite material prepared in Example 1 applied to a lithium-sulfur battery;

[0030] Figure 4 Cycle performance graph of the sulfur-based composite material prepared in Example 1 applied to a lithium-sulfur battery;

[0031] Figure 5 SEM image of the carbon nanotubes / bismuth vanadate composite carrier prepared in Example 4. Detailed Description of the Invention

[0032] The following examples are used to further illustrate the present invention, which can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way;

[0033] Example 1

[0034] Prepare a bismuth vanadate carrier material. The specific preparation process is as follows:

[0035] Dissolve 10 mmol of bismuth nitrate pentahydrate in 40 mL of ethylene glycol at 90 °C. Dissolve 10 mmol of ammonium metavanadate in 40 mL of deionized water at 60 °C. Use a peristaltic pump (drip rate 0.5 mL / min) to drip the ammonium metavanadate aqueous solution into the ethylene glycol solution of bismuth nitrate pentahydrate. Keep stirring vigorously during the dripping process. The whole reaction is carried out in a reflux device. After the dripping is completed, continue stirring for 60 min. Then wash the obtained precipitate with deionized water and absolute ethanol. Put the washed precipitate into an oven at 60 °C and dry it for 12 h to obtain the bismuth vanadate carrier material.

[0036] The obtained carrier material has a rice grain-like morphology, as Figure 1 shown in the SEM image of the carrier material. The particle size of the bismuth vanadate particles is 1 - 2 μm.

[0037] Figure 2 Figure of the cycle performance of the battery using the above-prepared bismuth vanadate as the cathode material. The initial discharge specific capacity at 0.1C is 89 mAh g -1 , and the discharge specific capacity after 50 cycles is 38.5 mAh g -1 , indicating that the prepared carrier material has certain electrochemical activity within the working range of the lithium-sulfur battery.

[0038] Prepare a sulfur-based composite cathode material with bismuth vanadate as the carrier by the melting method. The specific preparation process is as follows:

[0039] Mix 0.8 g of elemental sulfur with 0.2 g of the above-prepared bismuth vanadate carrier material, grind it in an agate mortar for 30 min, then put it into a crucible wrapped with tin foil, keep it at 155 °C for 12 h. After the heating is completed and the temperature returns to room temperature, grind the product in the agate mortar again for 20 min. Finally, obtain a sulfur-based composite cathode material with bismuth vanadate as the carrier, and the sulfur content is 80 wt%.

[0040] Make the prepared composite cathode material into an electrode sheet according to the following method and assemble the battery for testing. The specific method is as follows:

[0041] Weigh 0.28 g of the above-prepared positive composite material, 0.08 g of conductive carbon black (Super P), and 0.04 g of polyvinylidene fluoride (PVdF), and place them in a flat weighing bottle. After mixing evenly, add 2.6 mL of N-methylpyrrolidone (NMP), and stir for 6 h to obtain a positive electrode slurry with appropriate viscosity (Super P, PVdF, and NMP are all conventional reagents in the art); then use a coater to evenly coat the slurry on carbon paper (Toray carbon paper, model: TGP-H-060 hydrophilic type), with a coating amount of 0.2 g, and place it in an oven at 60 °C for drying for 12 h for standby; then cut the dried positive electrode sheet into circular pieces with a diameter of 10 mm. The mass of sulfur in each positive electrode is about 1.3 mg, and it is assembled into a button cell in a glove box filled with argon. The electrolyte dosage is 30 μL / mg (the mass is the above sulfur mass). After assembly, after the battery stands for 24 h, it is activated for two weeks at 0.03C and one week at 0.06C on a battery test system, and then tested with a charge-discharge program at 0.1C and a voltage range of 1.7 - 2.8V. As shown in Figure 3 the first-week charge-discharge performance diagram of the battery. It can be seen that the first-week discharge specific capacity at 0.1C is 1289 mAh g -1 ; Figure 4 This is the cycle performance diagram of the battery. After 100 cycles, the discharge specific capacity is 623.5 mAh g -1 .

[0042] Example 2

[0043] The preparation method of the sulfur-based composite positive electrode material is the same as that in Example 1, except that the composition of the sulfur-based composite positive electrode material is 0.7 g of elemental sulfur and 0.3 g of bismuth vanadate carrier material, and the sulfur content is 70 wt%; the above composite positive electrode material is made into an electrode sheet according to the method described in Example 1, and the battery is assembled and tested according to the method described in Example 1. The discharge specific capacity of the battery is calculated based on the mass of the active substance sulfur. The first-week discharge specific capacity is 1217.0 mAh g -1 , and the discharge specific capacity after 100 cycles is 795.0 mAh g -1 , and the capacity retention rate is 65.3%.

[0044] Example 3

[0045] Prepare the bismuth vanadate carrier material according to the scheme described in Example 1, and then prepare the sulfur-based composite positive electrode material with bismuth vanadate as the carrier by the chemical precipitation method. The specific preparation process is as follows:

[0046] Dissolve 2 g of polyvinylpyrrolidone (PVP) in 400 mL of water to prepare an aqueous PVP solution. Then dissolve 0.02 mol of sodium thiosulfate pentahydrate in 200 mL of the PVP aqueous solution in proportion. After thoroughly grinding 0.16 g of the bismuth vanadate carrier material, slowly add it to the above solution and ultrasonicate for 1 h. Prepare 5 wt% dilute hydrochloric acid, and use a peristaltic pump (drip rate 0.5 mL / min) to slowly drip the dilute hydrochloric acid into the ultrasonically treated mixed liquid. Keep stirring vigorously during the dripping process. After dripping, continue stirring for 4 h. Then wash the obtained precipitate with deionized water and absolute ethanol. Put the washed precipitate into an oven at 60 °C and dry for 12 h. After cooling to room temperature, take out the product and grind it with an agate mortar for 20 min to obtain the above composite cathode material.

[0047] Fabricate the electrode sheet with the prepared composite cathode material according to the method described in Example 1, and assemble and test the battery according to the method described in Example 1. Calculate the discharge specific capacity of the battery based on the mass of the active substance sulfur. The discharge specific capacity in the first cycle is 1235.5 mAh g -1 , and the discharge specific capacity after 100 cycles is 801.0 mAh g -1 , and the capacity retention rate is 64.83%.

[0048] Example 4

[0049] Prepare a carbon nanotube / bismuth vanadate composite carrier material. The specific preparation process is as follows:

[0050] Place 0.324 g of carbon nanotubes in 30 mL of ethylene glycol at 90 °C and ultrasonicate for 30 min. Dissolve 1 mmol of bismuth nitrate pentahydrate in the above mixed solution. Dissolve 1 mmol of ammonium metavanadate in 30 mL of deionized water at 60 °C in proportion. Use a peristaltic pump (drip rate 0.5 mL / min) to drip the ammonium metavanadate aqueous solution into the ethylene glycol solution of bismuth nitrate pentahydrate / carbon nanotubes. Keep stirring vigorously during the reaction process. The whole reaction is carried out in a reflux device. After dripping, continue stirring for 60 min. Then wash the obtained precipitate with deionized water and absolute ethanol. Put the washed precipitate into an oven at 60 °C and dry for 12 h to obtain the carbon nanotube / bismuth vanadate composite carrier material.

[0051] Figure 5 is the SEM image of the above composite carrier material. The carbon nanotubes are evenly covered on the surface of bismuth vanadate, forming a good conductive network. Compared with Example 1, the carrier material can form a conductive network, greatly improving the conductivity of the composite material.

[0052] A sulfur-based composite cathode material with carbon nanotubes / bismuth vanadate as the carrier was prepared by the melting method. The specific preparation process is as follows: 0.8 g of elemental sulfur was mixed with 0.2 g of carbon nanotubes / bismuth vanadate composite carrier material, ground in an agate mortar for 30 min, and then placed in a crucible wrapped with tin foil. It was kept at 155 °C for 12 h. After the heating was completed and the temperature returned to room temperature, the product was ground in the agate mortar again for 20 min. Finally, a sulfur-based composite cathode material with carbon nanotubes / bismuth vanadate as the carrier was obtained, and the sulfur content was 80 wt%.

[0053] The above-prepared composite cathode material was made into an electrode sheet according to the method described in Example 1, and the battery was assembled and tested according to the method described in Example 1. The discharge specific capacity of the battery was calculated based on the mass of the active material sulfur. The first-week discharge specific capacity at 0.2C was 1056.4 mAh g -1 After 100 cycles, the discharge specific capacity was 827.45.0 mAh g -1 and the capacity retention rate was 78.32%.

[0054] Example 5

[0055] To prepare an iron vanadate carrier material, the specific preparation process is as follows: 10 mmol of ferric nitrate nonahydrate was dissolved in 40 mL of ethylene glycol at 90 °C, and 10 mmol of ammonium metavanadate was dissolved in 40 mL of deionized water at 60 °C. The ammonium metavanadate aqueous solution was dropped into the ethylene glycol solution of ferric nitrate nonahydrate using a peristaltic pump (drip rate 0.5 mL / min). The dropping process was kept under vigorous stirring, and the whole reaction was carried out in a reflux device. After the dropping was completed, stirring was continued for 60 min. Subsequently, the obtained precipitate was washed with deionized water and absolute ethanol, and the washed precipitate was placed in an oven at 60 °C and dried for 12 h to obtain the iron vanadate carrier material.

[0056] 0.7 g of elemental sulfur was mixed with 0.3 g of the above-prepared iron vanadate carrier material, ground in an agate mortar for 30 min, and then placed in a crucible wrapped with tin foil. It was kept at 155 °C for 12 h. After the heating was completed and the temperature returned to room temperature, the product was ground in the agate mortar again for 20 min. Finally, a sulfur-based composite cathode material with iron vanadate as the carrier was obtained, and the sulfur content was 70 wt%.

[0057] The above-prepared composite cathode material was made into an electrode sheet according to the method described in Example 1, and the battery was assembled and tested according to the method described in Example 1. The discharge specific capacity of the battery was calculated based on the mass of the active material sulfur. The first-week discharge specific capacity was 1160.0 mAh g -1 After 100 cycles, the discharge specific capacity was 740.0 mAh g -1 and the capacity retention rate was 63.79%.

[0058] Example 6

[0059] Preparation of Co 0.5 Mn 0.5 V3O8 support material, and the specific preparation process is as follows: 5 mmol of cobalt nitrate and 5 mmol of manganese nitrate are dissolved in 40 mL of ethylene glycol at 90 °C. 30 mmol of ammonium metavanadate is dissolved in 40 mL of deionized water at 60 °C. The ammonium metavanadate aqueous solution is added dropwise to the ethylene glycol solution of cobalt nitrate and manganese nitrate by using a peristaltic pump (the dropping rate is 0.5 mL / min). During the dropping process, vigorous stirring is maintained. The whole reaction is carried out in a reflux device. After the dropping is completed, stirring is continued for 60 min. Subsequently, the obtained precipitate is washed with deionized water and absolute ethanol, and the washed precipitate is placed in an oven at 60 °C for drying for 12 h to obtain Co 0.5 Mn 0.5 V3O8 support material.

[0060] Preparation of Na3VO4 support material, and the specific preparation process is as follows: 10 mmol of sodium nitrate is dissolved in 40 mL of ethylene glycol at 90 °C. 10 mmol of ammonium metavanadate is dissolved in 40 mL of deionized water at 60 °C. The ammonium metavanadate aqueous solution is added dropwise to the ethylene glycol solution of sodium nitrate by using a peristaltic pump (the dropping rate is 0.5 mL / min). During the dropping process, vigorous stirring is maintained. The whole reaction is carried out in a reflux device. After the dropping is completed, stirring is continued for 60 min. Subsequently, the obtained precipitate is washed with deionized water and absolute ethanol, and the washed precipitate is placed in an oven at 60 °C for drying for 12 h to obtain Na3VO4 support material.

[0061] Mix 0.8 g of elemental sulfur with 0.1 g of the prepared Co 0.5 Mn 0.5 V3O8 support and 0.1 g of the prepared Na3VO4 support material, place them in an agate mortar and grind for 30 min, then put them into a crucible wrapped with tin foil, keep them at 155 °C for 12 h. After heating and returning to room temperature, place the product in the agate mortar again and grind for 20 min. Finally, a sulfur-based composite cathode material with Co 0.5 Mn 0.5 V3O8 and Na3VO4 as supports is obtained, and the sulfur content is 80 wt%.

[0062] The prepared above-mentioned composite cathode material is made into an electrode sheet according to the method described in Example 1, and the battery is assembled and tested according to the method described in Example 1. The discharge specific capacity of the battery is calculated based on the mass of the active substance sulfur. The first-week discharge specific capacity is 1360.0 mAh g -1 , and the discharge specific capacity after 100 cycles is 940.0 mAh g -1 , and the capacity retention rate is 69.1%.

[0063] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity in description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification. The description of the above embodiments can be used to help understand the principles and methods of the present invention. However, the above embodiments are not exclusive and should not be construed as a limitation on the present invention. At the same time, for those of ordinary skill in the art, based on the principles and methods of the present invention, flexible changes can be made in the specific implementation manners and application scopes.

Claims

1. A sulfur-based composite cathode material, characterized in that: It consists of elemental sulfur and a vanadate carrier or a carbon / vanadate composite carrier; wherein the sulfur is one or more of sublimed sulfur, precipitated sulfur, refined sulfur, and nano sulfur; and its content is 50-95 wt% of the entire composite material. The vanadate carrier is one or more of AxVyOz, where 1 < x < 3, 1 < y < 3, 3 < z < 8, and A is one or more of Bi, Fe, Co, and Mn; The preparation method of the vanadate carrier material is as follows: 1-10 mmol of nitrate is dissolved in 4-40 mL of ethylene glycol at 50°C-100°C, and 1-10 mmol of ammonium metavanadate is dissolved in 4-40 mL of deionized water at 50°C-100°C. The ammonium metavanadate aqueous solution is dropped into the nitrate ethylene glycol solution using a peristaltic pump. The reaction process is kept under vigorous stirring, and the whole reaction is carried out in a reflux device. After dropping, continue to stir for 10-60 min. Then, the obtained precipitate is washed with deionized water and absolute ethanol, and the washed precipitate is placed in an oven at 50-100°C and dried for 10-24 h to obtain the product; In the carbon / vanadate composite carrier, the carbon is one or more of carbon nanotubes, graphene, carbon nanofibers, and porous carbon, and the vanadate content in the composite carrier is 5-95 wt%; The preparation method of the carbon / vanadate composite carrier is as follows: 0.1-0.5 g of carbon material is placed in 4-40 mL of ethylene glycol at 50°C-100°C and ultrasonicated for 10-30 min. Then, 1-10 mmol of nitrate is dissolved in the above solution in proportion, and 1-10 mmol of ammonium metavanadate is dissolved in 4-40 mL of deionized water at 50°C-100°C. The ammonium metavanadate aqueous solution is dropped into the above carbon material and nitrate ethylene glycol solution using a peristaltic pump. The reaction process is kept under vigorous stirring, and the whole reaction is carried out in a reflux device. After dropping, continue to stir for 10-60 min. Then, the obtained precipitate is washed with deionized water and absolute ethanol, and the washed precipitate is placed in an oven at 50-100°C and dried for 10-24 h to obtain the product; The vanadate carrier or the carbon / vanadate composite carrier has lithium storage activity in the working voltage range of 1.7-2.8 V of the lithium-sulfur battery.

2. The thiol-based composite cathode material according to claim 1, characterized in that: The carbon nanotubes have a diameter of 0.6-200 nm, and the carbon nanofibers have a diameter less than 500 nm.

3. The preparation method of the sulfur-based composite cathode material according to claim 1, characterized in that: Using the melting method, the melting method is to grind the carrier material and elemental sulfur, where the sulfur content is 50-95 wt%, in an agate mortar for 20-60 min, then put it into a crucible wrapped with tin foil, keep it at 100-200°C for 10-24 h. After heating and returning to room temperature, the product is ground again in the agate mortar for 20-60 min to finally obtain a sulfur-based composite cathode material with vanadate as the carrier.

4. The preparation method of the sulfur-based composite cathode material according to claim 1, characterized in that: Prepared by chemical deposition method, wherein the chemical deposition method is to dissolve 0.1-10 g of polyvinylpyrrolidone PVP in 10-500 mL of water to prepare an aqueous PVP solution; then dissolve 0.01-1 mol of sodium thiosulfate pentahydrate in 100-500 mL of the PVP aqueous solution in proportion. After thoroughly grinding 0.1-10 g of vanadate or carbon / vanadate composite support, slowly add it to the above solution and sonicate for 1-10 h; Prepare 1-10 wt% dilute hydrochloric acid, and use a peristaltic pump to slowly drip the dilute hydrochloric acid into the sonicated mixed liquid. Keep stirring vigorously during the dripping process. After the dripping is completed, continue to stir for 1-10 h. Then wash the obtained precipitate with deionized water and absolute ethanol. Put the washed precipitate into an oven at 60-200 °C and dry for 10-24 h. After cooling to room temperature, take out the product and grind it with an agate mortar for 20-60 min to finally obtain a sulfur-based composite cathode material with vanadate as the support.

5. Application of the sulfur-based composite cathode material according to claim 1 in the preparation of lithium-sulfur batteries.

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