A quasi-solid electrolyte based on WS2 / CNTs composite material and its preparation method and application

Abstract

A quasi-solid electrolyte based on a WS2 / CNTs composite material, and its preparation method and application, belong to the field of new energy materials and device technology. The composite material is a three-dimensional network structure with rich pores formed by the overlapping and interconnection of one-dimensional sulfonated CNTs and two-dimensional WS2 nanosheets. It is adsorbed into an organic electrolyte for lithium-sulfur batteries to obtain a porous framework-type solid electrolyte. Due to its large specific surface area and porous structure, it can effectively intercept the dissolution and diffusion of polysulfides and realize the rapid and free transmission of lithium ions and the efficient utilization of active substances. The lithium-sulfur battery system assembled based on this type of solid electrolyte exhibits excellent electrochemical properties, including high specific capacity, excellent rate performance and good cycle performance. In addition, the preparation method of this type of solid electrolyte is simple, easy to control, and has good reproducibility, which is conducive to industrial promotion and provides a new way to prepare quasi-solid electrolytes.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials and devices, and in particular relates to a quasi-solid electrolyte based on WS2 / CNTs composite material, and a preparation method and application thereof. Background Art

[0002] In recent years, in order to improve the high performance of lithium-sulfur batteries and solve the problems of polysulfide dissolution and diffusion, researchers have done a lot of research on lithium-sulfur battery electrolytes. These works mainly focus on optimizing the composition of organic electrolytes, using electrolyte additives and solid electrolytes. Since 1989, researchers have begun to use methods to adjust the composition of electrolytes to improve the performance of lithium-sulfur batteries. At present, the electrolyte components of lithium-sulfur batteries are mainly ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) as solvents to ensure that the electrolyte has high ionic conductivity (~10 -3 S / cm), and LiNO3 is used as an additive to form a protective film on the negative electrode to prevent the side reaction between polysulfides and metallic lithium. However, the problem of polysulfides dissolving in the electrolyte during charging and discharging is difficult to solve.

[0003] Compared with liquid electrolytes, solid electrolytes can effectively inhibit the dissolution and diffusion of polysulfides, and at the same time have the characteristics of good safety and stable electrochemical performance, which opens another door for the development of lithium-sulfur batteries. The research on solid electrolytes mainly focuses on two categories: polymer solid electrolytes and inorganic solid electrolytes. Polymer solid electrolytes are composed of polymer films and lithium salts. Their outstanding advantages are good electrochemical stability and strong deformation ability. They can ensure good contact with the electrodes, and it is easy to modify and modify the molecular structure of the polymer to meet special requirements. In particular, polymer solid electrolytes based on polyethylene oxide (PEO) have received widespread attention since they were first introduced into lithium-sulfur batteries. This type of electrolyte mainly uses the chain segment movement of PEO to achieve lithium ion conduction, which can greatly reduce the dissolution of polysulfides in the electrolyte, and its flexible characteristics can reduce interfacial impedance. However, the biggest disadvantage of this type of electrolyte is the low lithium ion conductivity at room temperature, generally below 10 -6 S / cm, the battery can only work normally under relatively high temperature conditions (70-90℃), and the operating temperature range is narrow.

[0004] The application of inorganic solid electrolytes in lithium-sulfur batteries is mainly based on sulfide electrolytes. This type of electrolyte has a high room temperature lithium ion conductivity of about 10 -4 S / cm, and the room temperature lithium ion conductivity of special inorganic solid electrolytes can reach 10 -2S / cm, which can suppress polysulfide dissolution and protect the negative electrode. However, the preparation process of inorganic solid electrolytes is complex and their interfacial compatibility with electrodes is poor. Analysis of existing electrolyte research shows that simultaneously achieving rapid lithium ion transport and suppressing polysulfide dissolution and shuttling is a challenge in the design and preparation of lithium-sulfur battery electrolytes.

[0005] Unlike existing liquid and solid electrolyte concepts, this invention modifies the surface of multi-walled carbon nanotubes (CNTs) by sulfonation, making their surface Lewis acidic. Ultrathin two-dimensional WS2 nanosheets are then grown on the surface of the sulfonated CNTs to obtain a three-dimensional porous structure WS2 / CNTs composite material. The WS2 / CNTs are then immersed in an organic electrolyte as a solid electrolyte skeleton to fix lithium salt anion groups, promote the dissociation of lithium salts, and achieve rapid and free movement of lithium ions in the electrolyte. At the same time, based on the principle of like charges repelling, the dissolution and diffusion of polysulfide anions can be effectively prevented. In addition, polar WS2 can adsorb and catalyze the conversion of polysulfides to inhibit the shuttle effect, ultimately achieving the goal of improving the overall performance of lithium-sulfur batteries. Summary of the Invention

[0006] The purpose of the present invention is to introduce a three-dimensional porous WS2 / CNTs composite material into the organic electrolyte for lithium-sulfur batteries as a skeleton to adsorb the organic electrolyte, thereby promoting lithium ion transmission and inhibiting the dissolution and shuttling of polysulfides, thereby proposing a solid-like electrolyte based on WS2 / CNTs composite material and its preparation method and application.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A solid-like electrolyte based on WS2 / CNTs composite material is composed of an organic electrolyte for lithium-sulfur batteries and a WS2 / CNTs composite material uniformly dispersed in the electrolyte. The WS2 / CNTs composite material is a three-dimensional network structure with rich pores formed by overlapping and interconnecting one-dimensional sulfonated CNTs and two-dimensional WS2 nanosheets, which is conducive to the adsorption of organic electrolyte for lithium-sulfur batteries to form a porous framework solid electrolyte.

[0009] In the quasi-solid electrolyte proposed in the present invention, the electrolyte is preferably an organic electrolyte for lithium-sulfur batteries including LS-001, LS-002, etc., and the weight proportion of the WS2 / CNTs composite material in the quasi-solid electrolyte is preferably 5-20%.

[0010] In the solid electrolyte proposed in the present invention, the WS2 / CNTs composite material is obtained by growing ultrathin two-dimensional WS2 nanosheets on the surface of one-dimensional sulfonated CNTs by a hydrothermal method, and the specific steps are as follows:

[0011] Take 20-80 mg of sulfonated CNTs and 40-100 mg of hexadecyltrimethylammonium bromide (CTAB), place them in a beaker filled with 20-80 mL of deionized water and ultrasonically disperse them for 0.5-1.5 hours to obtain a mixed solution A; weigh 15-75 mg of thioacetamide (TAA) and 40-100 mg of tungsten hexachloride (WCl6), place them in a beaker filled with 10-70 mL of deionized water and ultrasonically disperse them for 0.5-1.5 hours, marked as solution B; A and B are fully mixed and ultrasonically dispersed for 0.5-1 hour, and after dispersion, transferred to the inner lining of a 50-200 mL reactor, kept at 250-270°C for 20-30 hours, centrifuged and washed, and vacuum dried at 50-80°C for 12-24 hours to obtain WS2 / CNTs powder.

[0012] In the quasi-solid electrolyte proposed in the present invention, the sulfonated CNTs are obtained by sulfonating multi-walled CNTs, and the specific steps are as follows:

[0013] CNTs are refluxed with 60-70% HNO3 at 70-100°C for 2-4 hours, washed, and vacuum-dried to obtain purified CNTs; then, they are refluxed with a mixed acid of 4-6 mol / L HNO3 and 4-6 mol / L H2SO4 at 70-100°C for 4-6 hours, washed, and vacuum-dried; finally, they are dispersed in a (NH4)2SO4 solution and heated at 230-260°C for 0.5-1 hour to obtain sulfonated CNTs, wherein the mass ratio of CNTs to (NH4)2SO4 is 8-10:1.

[0014] At the same time, the present invention also proposes a method for preparing a solid-like electrolyte. First, the surface of CNTs is sulfonated, and then ultra-thin two-dimensional WS2 nanosheets are grown on the surface of CNTs by a hydrothermal method to obtain a three-dimensional network structure WS2 / CNTs composite material. WS2 / CNTs are used as a solid-like electrolyte skeleton and immersed in an organic electrolyte to obtain a solid-like electrolyte.

[0015] At the same time, the present invention also proposes a lithium-sulfur battery assembled with a solid-like electrolyte made from the WS2 / CNTs composite material.

[0016] The present invention assembles 2032 button batteries in the order of negative electrode shell-spring sheet-gasket-lithium sheet-electrolyte-diaphragm-electrolyte-positive electrode sheet-positive electrode shell and tests the electrochemical performance, and analyzes the influence of the solid-like electrolyte made from the WS2 / CNTs composite material on the performance of the lithium-sulfur battery.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention is designed based on the key components of lithium-sulfur batteries. By sulfonating multi-walled carbon nanotubes (CNTs), the CNT surface becomes Lewis acidic. Ultrathin two-dimensional WS2 nanosheets are then grown on the CNT surface to obtain a three-dimensional porous WS2 / CNTs composite material. WS2 / CNTs are then used as a framework to adsorb an organic electrolyte to construct a quasi-solid electrolyte. The sulfonated CNTs can fix lithium salt anion groups, promote the dissociation of lithium salts, and enable the rapid and free movement of lithium ions in the electrolyte. At the same time, based on the principle of like charges repelling each other, they can effectively prevent the dissolution and diffusion of polysulfide anions. In addition, the polar WS2 nanosheets can adsorb and catalyze the conversion of polysulfides to inhibit the shuttle effect, and the porous WS2 / CNTs can also physically intercept the diffusion shuttle of polysulfides to a certain extent. The lithium-sulfur battery system assembled based on this type of solid electrolyte exhibits excellent electrochemical properties, including high specific capacity, excellent rate capability, and good cycling performance. In addition, the preparation method of this type of solid electrolyte is simple, easy to control, and has good repeatability, which is conducive to industrial promotion and provides a new way to prepare solid electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the SEM morphology of the sulfonated CNTs in Example 1.

[0020] Figure 2 (a) SEM image and (b) TEM image of WS2 / CNTs in Example 1.

[0021] Figure 3 2 are the XRD curves of sulfonated CNTs and WS2 / CNTs composite materials in Example 1.

[0022] Figure 4 These are the cycling performance test results of the lithium-sulfur battery assembled with a quasi-solid electrolyte based on the WS2 / CNTs framework structure (the mass ratio of WS2 / CNTs to electrolyte is 1:10) at a current density of 0.5C in Example 1.

[0023] Figure 5 These are the rate performance test results of the lithium-sulfur battery assembled with a quasi-solid electrolyte based on the WS2 / CNTs framework structure (the mass ratio of WS2 / CNTs to electrolyte is 1:10) in Example 1.

[0024] Figure 6 GITT test results of the lithium-sulfur battery assembled with a quasi-solid electrolyte based on the WS2 / CNTs framework structure (the mass ratio of WS2 / CNTs to electrolyte is 1:10) in Example 1.

[0025] Figure 7These are the cycle performance test results of the lithium-sulfur battery assembled based on the ordinary electrolyte without adding WS2 / CNTs in Comparative Example 1 at a current density of 0.5C.

[0026] Figure 8 These are the rate performance test results of the lithium-sulfur battery assembled based on the ordinary electrolyte without adding WS2 / CNTs in Comparative Example 1.

[0027] Figure 9 These are the GITT test results of the lithium-sulfur battery assembled based on the ordinary electrolyte without adding WS2 / CNTs in Comparative Example 1.

[0028] Figure 10 The cycling performance results of the lithium-sulfur battery with a solid electrolyte based on the WS2 / CNTs framework structure (CNTs are not surface-sulfonated, and the mass ratio of WS2 / CNTs to electrolyte is 1:10) at a current density of 0.5C in Comparative Example 2 are shown in FIG.

[0029] Figure 11 These are the cycling performance test results of the lithium-sulfur battery assembled with a quasi-solid electrolyte based on the WS2 / CNTs framework structure (the mass ratio of WS2 / CNTs to electrolyte is 1:5) at a current density of 0.5C in Example 2.

[0030] Figure 12 These are the cycling performance test results of the lithium-sulfur battery assembled with a quasi-solid electrolyte based on a WS2 / CNTs framework structure (the mass ratio of WS2 / CNTs to electrolyte is 1:20) at a current density of 0.5C in Example 3. DETAILED DESCRIPTION

[0031] The following is a further detailed description of a quasi-solid electrolyte based on a WS2 / CNTs composite material, its preparation method, and application provided by the present invention in combination with the examples and drawings.

[0032] Example 1

[0033] This example uses a hydrothermal method to grow two-dimensional ultrathin WS2 nanosheets on the surface of one-dimensional sulfonated CNTs. The two are cross-linked to form a three-dimensional porous WS2 / CNTs composite material. The WS2 / CNTs are then uniformly dispersed in an organic electrolyte (LS-002). Utilizing their porous properties to fully absorb the electrolyte, a quasi-solid electrolyte with the WS2 / CNTs as its skeleton is prepared. This is then used as the electrolyte for assembling a lithium-sulfur battery. The steps include:

[0034] Step (1): reflux CNTs with 70% HNO3 at 100°C for 3 hours, wash, and vacuum dry to obtain purified CNTs; then reflux them with 5 mol / L HNO3 and 5 mol / L H2SO4 at 100°C for 6 hours, wash, and vacuum dry; finally, disperse them in (NH4)2SO4 solution and heat them at 235°C for 1 hour to obtain sulfonated CNTs, wherein the mass ratio of CNTs to (NH4)2SO4 is 10:1.

[0035] Step (2): Weigh 20 mg of sulfonated CNTs and 40 mg of cetyltrimethylammonium bromide (CTAB), place them in a beaker containing 20 mL of deionized water and ultrasonically disperse them for 1 hour to obtain a uniformly dispersed suspension A. Weigh 15 mg of thioacetamide (TAA) and 40 mg of tungsten hexachloride (WCl6), place them in a beaker containing 10 mL of deionized water and ultrasonically disperse them for 30 minutes to obtain a uniformly dispersed solution B.

[0036] Step (3): Suspension A and solution B were mixed and ultrasonicated for 30 min, and then uniformly dispersed and transferred to the inner lining of a 50 mL reactor. After being kept at 265 ° C for 24 h, they were centrifuged and washed, and vacuum dried at 70 ° C for 12 h to obtain WS2 / CNTs powder.

[0037] Step (4): The WS2 / CNTs obtained in step (3) were mixed with the electrolyte for lithium-sulfur batteries (LS-002) in a mass ratio of 1:10, and ultrasonically dispersed for 30 minutes to obtain a viscous liquid.

[0038] Step (5): Using the sulfur / carbon composite electrode as the positive electrode, the Celgard 2500 membrane as the separator, the lithium sheet as the negative electrode, and the solid electrolyte obtained in step (4) as the electrolyte, assemble a 2032 button cell in the order of negative electrode shell-spring sheet-gasket-lithium sheet-electrolyte-separator-electrolyte-positive electrode sheet-positive electrode shell and perform electrochemical performance testing. The area mass of active sulfur in the positive electrode sheet is approximately 1.5 mg / cm 2 , controlling the E / S (electrolyte / active sulfur) ratio to 5.0 μL mg -1 .

[0039] See also Figure 1 , which is a SEM morphology of the sulfonated CNTs used in this example. As can be seen from the figure, the CNTs have a one-dimensional tubular structure with a diameter of about 5 to 10 nm.

[0040] See also Figure 2 The figure shows the SEM image (a) and TEM image (b) of the prepared WS2 / CNTs, which clearly show the three-dimensional network structure of overlapping and interconnected WS2 and CNTs.

[0041] See also Figure 3The figure shows the XRD curves of the sulfonated CNTs and WS2 / CNTs composite. The WS2 / CNTs spectrum shows three sharp diffraction peaks at 13.9°, 28.0°, and 36.7°, corresponding to the characteristic peaks of the (002), (004), and (102) crystal planes of hexagonal WS2 (JCPDS: 08-0237), respectively. Characteristic peaks of CNTs also appear at 25.6° and 44.5°. These analysis results indicate that WS2 and CNTs are effectively composited, and the resulting material is of high purity and good crystallinity.

[0042] See also Figure 4 The figure shows the cycling performance test results of a lithium-sulfur battery assembled with a WS2 / CNTs framework-based solid electrolyte (WS2 / CNTs to electrolyte mass ratio is 1:10) at a current density of 0.5C. As shown in the figure, the battery's first discharge capacity is 967.5mAh·g -1 After 500 cycles, the capacity remains at 634.3 mAh g -1 The decay rate per cycle is about 0.068%, showing excellent cycle stability.

[0043] See also Figure 5 The figure shows the rate performance test results of the lithium-sulfur battery assembled with the WS2 / CNTs framework-based solid electrolyte (WS2 / CNTs to electrolyte mass ratio of 1:10) in Example 1. As shown in the figure, the current density increases stepwise in the range of 0.2-5.0C. The average capacity of the battery at 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0C is 1259.2, 956.6, 875.9, 795.2, 656.1, and 423.5 mAh·g, respectively. -1 When the current density returned to 0.5C, the capacity still reached 897.6 mAh g -1 , showing good rate performance.

[0044] See also Figure 6 The figure shows the GITT test results of the lithium-sulfur battery assembled with a quasi-solid electrolyte based on the WS2 / CNTs framework structure (the mass ratio of WS2 / CNTs to electrolyte is 1:10) in Example 1. GITT technology is widely used to reveal the Li + Ion diffusion kinetics, as shown in the figure, whether in the charging or discharging process, the solid electrolyte Li formed by introducing WS2 / CNTs into the organic electrolyte + The diffusion rate is large, on the order of 10 -9 -10 -10 About, indicating that the improvement of battery performance is affected by Li + The transmission dynamics have a great influence.

[0045] The above battery performance test results show that the solid-state electrolyte-assembled battery based on WS2 / CNTs composite material provided by the present invention has excellent electrochemical performance, which is mainly attributed to the large specific surface area and porous distribution of this WS2 / CNTs composite material, which enhances the penetration and infiltration of the electrolyte; it can effectively intercept the dissolution and diffusion of polysulfides, and realize the efficient transmission of lithium ions and the full utilization of active substances; the one-dimensional sulfonated carbon matrix can show Lewis acidity, which is used to fix the lithium salt anion groups, promote the dissociation of lithium salts, and realize the rapid and free movement of lithium ions in the electrolyte solvent. Thanks to the good synergistic effect of the two, when used in lithium-sulfur batteries, it exhibits the advantages of high specific capacity, long cycle life, and good rate performance.

[0046] Comparative Example 1

[0047] In order to compare and illustrate the effect of a quasi-solid electrolyte based on WS2 / CNTs composite material provided by the present invention on the electrochemical performance of lithium-sulfur batteries, this comparative example uses ordinary electrolyte LS-002 to assemble batteries.

[0048] A sulfur / carbon composite electrode prepared by doctor blade coating was used as the positive electrode, a Celgard 2500 membrane as the separator, and a lithium sheet as the negative electrode. No WS2 / CNTs were added to the electrolyte. A 2032 button cell was assembled in the following order: negative electrode shell - spring sheet - gasket - lithium sheet - electrolyte - separator - electrolyte - positive electrode sheet - positive electrode shell, and the electrochemical performance was tested. The area mass of active sulfur in the sulfur positive electrode is approximately 1.5 mg / cm 2 , control the E / S (electrolyte / active sulfur) ratio to 5.0 μL mg -1 .

[0049] See also Figure 7 The figure shows the cycle performance test results of the lithium-sulfur battery assembled based on ordinary organic electrolyte in Comparative Example 1 at a current density of 0.5C. As shown in the figure, the first discharge capacity is 835.5mAh·g -1 After 500 cycles, the capacity is only 515.7 mAh g -1 The decay rate per cycle is about 0.076%, indicating that the battery capacity and cycle stability in Comparative Example 1 are significantly reduced compared with the battery in Example 1.

[0050] See also Figure 8 The figure shows the rate performance results of the lithium-sulfur battery assembled based on ordinary organic electrolyte in Comparative Example 1. As shown in the figure, the current density increases stepwise in the range of 0.2-5.0C. The average capacity of the battery at 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0C is 1104.1, 871.9, 800.1, 671.9, 550.8, and 216.7 mAh·g, respectively.-1 When the current density returned to 0.5C, the capacity reached 850.3mAh·g -1 , the rate performance is significantly lower than that of Example 1.

[0051] See also Figure 9 , This figure shows the GITT test results of the lithium-sulfur battery assembled based on ordinary organic electrolyte in Comparative Example 1. As shown in the figure, whether in the charging or discharging process, the battery Li assembled based on ordinary organic electrolyte + The diffusion rate is small, on the order of 10 -12 It is about 1.5, which is obviously lower than Example 1.

[0052] The electrochemical performance test results in Comparative Example 1 show that when a lithium-sulfur battery is assembled with a common electrolyte without the introduction of WS2 / CNTs, the capacity provided by the sulfur / carbon composite positive electrode is limited due to the shuttle effect of polysulfides and the low utilization rate of active materials.

[0053] Comparative Example 2

[0054] In order to compare and illustrate the effect of surface sulfonation of CNTs in a quasi-solid electrolyte based on WS2 / CNTs composite material provided by the present invention on the electrochemical performance of lithium-sulfur batteries, the CNTs in this comparative example were not subjected to surface sulfonation treatment.

[0055] The sulfur / carbon composite electrode prepared by the doctor blade method was used as the positive electrode, the Celgard 2500 membrane was used as the separator, the lithium sheet was used as the negative electrode, and the WS2 / CNTs and lithium-sulfur battery electrolyte (LS-002) were mixed in a mass ratio of 1:10 as the electrolyte. The 2032 button cell was assembled in the order of negative electrode shell-spring sheet-gasket-lithium sheet-electrolyte-separator-electrolyte-positive electrode sheet-positive electrode shell and the electrochemical performance was tested. The area loading of active sulfur in the positive electrode was about 1.5mg / cm 2 , controlling the E / S (electrolyte / active sulfur) ratio to 5.0 μL mg -1 .

[0056] See also Figure 10 The figure shows the cycling performance of a lithium-sulfur battery with a WS2 / CNTs framework-based solid electrolyte (WS2 / CNTs to electrolyte mass ratio of 1:10) at a current density of 0.5C in Comparative Example 2, where the CNTs were not surface-sulfonated. As shown in the figure, the first discharge capacity was 853.5 mAh g -1 After 500 cycles, the capacity is only 536.2 mAh g -1 The decay rate per cycle is about 0.074%, indicating that the battery capacity and cycle stability in Comparative Example 2 are significantly lower than those in Example 1.

[0057] In view of the poor cycling performance of the lithium-sulfur battery assembled with the solid-state electrolyte obtained by WS2 / CNTs prepared from unsulfonated CNTs (the mass ratio of WS2 / CNTs to electrolyte is 1:10) at a current density of 0.5C, no other performance tests were performed.

[0058] Example 2

[0059] The preparation method of this embodiment is the same as that of embodiment 1, except that the mass ratio of WS2 / CNTs to electrolyte (LS-002) in step (4) is adjusted from 1:10 to 1:5, and other conditions remain unchanged. Compared with the solid electrolyte prepared in embodiment 1, the content of WS2 / CNTs in the electrolyte is increased in this embodiment. Figure 11 It can be seen that when the current density is 0.5C, the battery's first discharge capacity is only 681.7mAh·g -1 After 500 cycles, the capacity remains at 317.3 mAh g -1 .

[0060] Example 3

[0061] The preparation method of this embodiment is the same as that of embodiment 1, except that the mass ratio of WS2 / CNTs to electrolyte (LS-002) in step (4) is adjusted from 1:10 to 1:20, and other conditions remain unchanged. Compared with the solid electrolyte prepared in embodiment 1, the content of WS2 / CNTs in the electrolyte is reduced in this embodiment. Figure 12 It can be seen that when the current density is 0.5C, the battery's first discharge capacity is 893.6mAh·g -1 After 400 cycles, the capacity remains at 603.4 mAh g -1 , the attenuation rate per turn is about 0.081%.

[0062] Example 4

[0063] The preparation method of this example is the same as that of Example 1, except that the mass ratio of WS2 / CNTs to electrolyte (LS-002) in step (4) is adjusted from 1:10 to 1:15, while other conditions remain unchanged. When the current density is 0.5C, the battery's first discharge capacity is 780.3mAh·g -1 After 500 cycles, the capacity remains at 432.6 mAh g -1 .

[0064] The above content is merely an example and explanation of the concept of the present invention. Various modifications or additions to the described specific embodiments or replacements made by technicians in this technical field in a similar manner shall fall within the scope of protection of the present invention as long as they do not deviate from the concept of the invention or exceed the scope defined by the claims.

Claims

1. A quasi-solid electrolyte based on WS2 / CNTs composite material, characterized in that: The invention is composed of a commercial organic electrolyte LS-002 for lithium-sulfur batteries and a WS2 / CNTs composite material uniformly dispersed in the electrolyte. The WS2 / CNTs composite material and the commercial organic electrolyte LS-002 for lithium-sulfur batteries are mixed in a mass ratio of 1:

10. The WS2 / CNTs composite material is a three-dimensional network structure with rich pores formed by the overlapping and interconnection of one-dimensional sulfonated CNTs and two-dimensional WS2 nanosheets, which is conducive to the adsorption of organic electrolytes for lithium-sulfur batteries to form a porous framework solid electrolyte.

2. The solid-state electrolyte according to claim 1, wherein The WS2 / CNTs composite material is obtained by growing ultrathin two-dimensional WS2 nanosheets on the surface of one-dimensional sulfonated CNTs by a hydrothermal method, and the specific steps are as follows: 20-80 mg of sulfonated CNTs and 40-100 mg of cetyltrimethylammonium bromide (CTAB) were placed in a beaker containing 20-80 mL of deionized water and ultrasonically dispersed for 0.5-1.5 h to obtain mixed solution A. 15-75 mg of thioacetamide (TAA) and 40-100 mg of tungsten hexachloride (WCl6) were weighed and placed in a beaker containing 10-70 mL of deionized water and ultrasonically dispersed for 0.5-1.5 h, marked as solution B. A and B were thoroughly mixed and ultrasonically dispersed for 0.5-1 h. After dispersion, the mixture was transferred to the inner liner of a 50-200 mL reactor, kept at 250-270 °C for 20-30 h, centrifuged and washed, and vacuum dried at 50-80 °C for 12-24 h to obtain WS2 / CNTs powder.

3. The solid-like electrolyte according to claim 2, wherein The sulfonated CNTs are obtained by sulfonating multi-walled CNTs, and the specific steps are as follows: CNTs were refluxed with 60-70% HNO3 at 70-100 °C for 2-4 h, washed, and vacuum-dried to obtain purified CNTs; It was then refluxed with a mixed acid of 4-6 mol / L HNO3 and 4-6 mol / L H2SO4 at 70-100°C for 4-6 hours, washed, and vacuum-dried; finally, it was dispersed in a (NH4)2SO4 solution and heated at 230-260°C for 0.5-1 hour to obtain sulfonated CNTs, where the mass ratio of CNTs to (NH4)2SO4 was 8-10:

1.

4. A method for preparing a quasi-solid electrolyte based on a WS2 / CNTs composite material as claimed in claim 1, characterized in that: First, the surface of CNTs was modified by sulfonation, and then ultra-thin two-dimensional WS2 nanosheets were grown on the surface of CNTs by a hydrothermal method to obtain a three-dimensional network structure WS2 / CNTs composite material. WS2 / CNTs was used as a solid-like electrolyte skeleton and immersed in an organic electrolyte to obtain a solid-like electrolyte.

5. An application of the quasi-solid electrolyte based on the WS2 / CNTs composite material in a lithium-sulfur battery as claimed in claim 1, characterized in that: This type of solid electrolyte was used as a lithium-sulfur battery electrolyte, and the lithium-sulfur battery was assembled and its electrochemical performance was tested.

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