阅读说明：本技术 一种锂硫电池用正极侧隔层材料的制备方法和应用 (Preparation method and application of positive electrode side interlayer material for lithium-sulfur battery ) 是由 李祥村 贺高红 郭娇 姜晓滨 吴雪梅 肖武 马沧海 于 2021-05-19 设计创作，主要内容包括：本发明公开了一种锂硫电池正极侧隔层材料的制备方法。以聚丙烯腈、钴盐、硫脲和氧化石墨烯为原料,通过静电纺丝、预氧化、碳化、电沉积CoS、电沉积并还原氧化石墨烯,得到能够截留多硫化物、缓解锂硫电池穿梭效应的RG@CoS@C膜(锂硫电池正极侧隔层材料),将RG@CoS@C膜插入锂硫电池正极和聚丙烯隔膜之间作为隔层,则RG@CoS@C隔层利用其CoS纳米片和石墨烯(RG)之间的“协同作用”能高效截留、吸附多硫化物,催化转化多硫化物,阻止其由锂硫电池正极向负极传递,从而缓解锂硫电池的穿梭效应,提高电池性能及循环寿命。以该膜为隔层的锂硫电池具有优异的储能性能,1.0C电流密度下初始放电比容为942.7mA h g～(-1),循环150圈后,每圈的容量损失率为0.02％,库伦效率接近100％。(The invention discloses a preparation method of a lithium-sulfur battery positive electrode side interlayer material. Polyacrylonitrile, cobalt salt, thiourea and graphene oxide are used as raw materials, through electrostatic spinning, pre-oxidation, carbonization, electrodeposition CoS, electrodeposition and reduction of graphene oxide, an RG @ CoS @ C film (lithium sulfur battery positive electrode side interlayer material) capable of intercepting polysulfide and relieving shuttle effect of a lithium sulfur battery is obtained, the RG @ CoS @ C film is inserted between a lithium sulfur battery positive electrode and a polypropylene diaphragm to serve as an interlayer, and then RG @The CoS @ C interlayer can efficiently intercept and adsorb polysulfide by utilizing the 'synergistic effect' between the CoS nanosheet and the graphene (RG), and catalytically convert the polysulfide to prevent the polysulfide from being transferred from the positive electrode to the negative electrode of the lithium-sulfur battery, so that the shuttle effect of the lithium-sulfur battery is relieved, and the performance and the cycle life of the battery are improved. The lithium-sulfur battery with the membrane as the interlayer has excellent energy storage performance, and the initial specific discharge capacity under the current density of 1.0C is 942.7mA h g ‑1 After 150 cycles, the capacity loss rate of each cycle is 0.02%, and the coulombic efficiency is close to 100%.)

1. A preparation method of a positive electrode side interlayer material for a lithium-sulfur battery is characterized by comprising the following steps: firstly, preparing a PAN nanofiber membrane through electrostatic spinning, and obtaining a carbon nanofiber membrane through hot pressing, pre-oxidation and carbonization; then, taking a mixed aqueous solution of cobalt salt and TU as an electrodeposition solution, and electrodepositing a CoS nanosheet on the carbon nanofiber membrane electrode by adopting a three-electrode electrodeposition system to obtain a CoS @ C membrane; thirdly, with GO and LiClO₄Mixed aqueous solution ofAdopting a three-electrode electrodeposition system to electrodeposit and reduce graphene oxide on a CoS @ C membrane electrode as electrodeposition liquid; finally LiClO is used₄The aqueous solution is used as electrolyte, and a three-electrode system is adopted to further reduce the graphene oxide deposited on the CoS, so that the RG @ CoS @ C interlayer film material is obtained.

2. The method for preparing a positive electrode-side separator for a lithium-sulfur battery according to claim 1, comprising the steps of:

1) sequentially adding polyacrylonitrile and a solvent into a silk mouth bottle, magnetically stirring the polyacrylonitrile and the solvent at 60-80 ℃ for 6 hours to obtain a light yellow transparent viscous membrane liquid, and carrying out electrostatic spinning to obtain a PAN nanofiber membrane; the mass ratio of polyacrylonitrile to a solvent in the membrane liquid is 1: 1-1: 30; the solvent is N, N-dimethyl formyl or dimethyl sulfoxide;

2) carrying out hot pressing on the obtained PAN nanofiber membrane for 2-20min at normal temperature, then carrying out pre-oxidation through a muffle furnace, and then carrying out carbonization in a tubular furnace under the protection of argon/nitrogen atmosphere to obtain a carbon nanofiber membrane;

3) constructing a three-electrode standard glass electrolytic cell by taking the carbon nanofiber membrane obtained in the step 2) as a working electrode, an Ag/AgCl electrode as a reference electrode and a graphite rod as a counter electrode, preparing a mixed aqueous solution of cobalt salt with the concentration of 1-20 mM and TU with the concentration of 0.1-10M as an electrodeposition solution, depositing CoS nanosheets on the carbon nanofiber membrane electrode by adopting a cyclic voltammetry method, and then cleaning and vacuum drying to obtain a CoS @ C membrane;

4) preparing LiClO with the concentration of 0.01-5.0M₄And a mixed aqueous solution of GO with the concentration of 0.1-10 mg/mL is used as an electrodeposition solution, a CoS @ C film obtained in the step 3) is used as a working electrode, an Ag/AgCl electrode is used as a reference electrode, a graphite rod is used as a counter electrode to construct a three-electrode standard glass electrolytic cell, a constant voltage method is adopted for electrodeposition and reduction of graphene oxide, cleaning is carried out after electrodeposition is finished, and then 1.0-5.0M LiClO is added₄And further reducing the graphene oxide deposited on the CoS in the three-electrode electrolytic cell, and then cleaning and vacuum drying to obtain the RG @ CoS @ C interlayer film.

3. The method according to claim 2, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 3), the range of the scanning rate of the cyclic voltammetry for electrodeposition is 1-50 mV/s, the range of the voltage is-1.5-0.5V vs. SCE, and the range of the number of scanning turns is 1-50 turns.

4. The method according to claim 2, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 4), the voltage range of electrodepositing and reducing the graphene oxide on the CoS @ C membrane electrode by a constant voltage method is-0.1 to-10V vs. SCE, and the time range is 10 to 600 s; the voltage range of the graphene oxide further reduced and deposited on the CoS is-1 to-2V vs. SCE, and the time range is 30 to 180 s.

5. The method according to claim 2, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: in the step 3) and the step 4), the vacuum drying conditions are as follows: the drying temperature is 50-80 ℃, and the drying time is 8-24 h.

6. The method for producing a positive electrode-side separator material for a lithium-sulfur battery according to claim 1 or 2, characterized in that: the pre-oxidation conditions are as follows: raising the temperature from room temperature to the pre-oxidation temperature at the temperature raising rate of 1-3 ℃ for min^-1The pre-oxidation temperature is 200-300 ℃, the pre-oxidation time is 1.5-4h, and the cooling rate from the pre-oxidation temperature to the room temperature is 1-10 ℃ min^-1。

7. The method for producing a positive electrode-side separator material for a lithium-sulfur battery according to claim 1 or 2, characterized in that: the carbonization conditions are as follows: heating the mixture from room temperature to carbonization temperature at a heating rate of 2-10 ℃ for min^-1The carbonization temperature is 700-900 ℃, the carbonization time is 1-2h, and the cooling rate of the carbonization temperature to the room temperature is 1-10 ℃ min^-1。

8. The method according to claim 2, wherein the positive electrode side separator material for a lithium-sulfur battery comprises: and 2) cutting the pre-oxidized PAN nanofiber membrane into round pieces.

9. The method for producing a positive electrode-side separator material for a lithium-sulfur battery according to claim 1 or 2, characterized in that: the molar concentration ratio of the TU to the cobalt salt in the mixed aqueous solution of the cobalt salt and the TU is 100: 1-200: 1.

10. Use of the positive electrode-side separator material obtained by the production method according to claim 1 in a lithium-sulfur battery.

Technical Field

The invention belongs to the field of lithium-sulfur battery positive electrode side interlayer materials, and particularly relates to a preparation method and application of a carbon nanofiber membrane, cobalt sulfide and graphene composite material as a lithium-sulfur battery positive electrode side interlayer material.

Background

With the rapid development of society, the demand for energy sources is higher and higher, and especially, the full utilization of solar energy, wind energy, tidal energy and the like puts higher demands on energy storage technology. Lithium ion batteries, sodium ion batteries, lithium sulfur batteries, and the like have been widely studied as an effective energy storage technique. The lithium ion battery has the advantages of high energy density, high charging efficiency, good temperature characteristic, low self-discharge, no memory effect and the like, and is widely applied to the fields of electronic products, new energy automobiles, unmanned aircrafts and the like. However, the energy density of the lithium ion cathode material is low and is close to the theoretical limit, and the requirement of further development of the society is difficult to meet. Therefore, it is still necessary to develop and explore a new generation of high capacity lithium battery material to promote the wide application of new energy devices.

Among lithium metal batteries, lithium sulfur batteries are rated at 1672mA h g^-1Theoretical capacity of 2600Wh kg^-1The theoretical energy density of (2) is of great interest and is an energy storage device with considerable prospect. In addition, the natural reserve of sulfur is abundant, the cost is low, and the lithium-sulfur battery is environment-friendly, so that the lithium-sulfur battery has the potential of large-scale energy storage application. However, the lithium-sulfur battery is practicalThe shuttle effect of polysulfides is still a problem in practical applications. Long chain lithium polysulphides Li during cycling of lithium-sulphur batteries₂S_x(4<x is less than or equal to 8) has extremely high solubility in electrolyte, polysulfide is driven to migrate to a metal lithium cathode by concentration gradient, and short-chain lithium polysulfide Li is formed on the cathode₂S_x(1<x 2) leading to a permanent loss of active species and reversible capacity, rapid corrosion of lithium metal. Lithium polysulphides migrate between the positive and negative electrodes, i.e. "shuttle effect". The shuttle effect is a main factor causing low coulombic efficiency of the lithium-sulfur battery, and the serious shuttle effect causes the problems of low charging efficiency, short cycle life, low safety performance and the like. The addition of the positive electrode side interlayer is an effective method for relieving the shuttle effect of the lithium-sulfur battery, the current research focuses on the improvement and optimization of single factors, the effect is limited, how to comprehensively optimize the structure of the interlayer is realized, and the method has important significance for the practical application of the lithium-sulfur battery.

Disclosure of Invention

Aiming at the problems, the invention provides a preparation method and application of a lithium-sulfur battery positive electrode side interlayer material. The carbon nanofiber membrane obtained by electrospinning Polyacrylonitrile (PAN) has high porosity, high specific surface area and good electrical conductivity. The electrodeposited incoming RG coating was tightly wrapped in situ on the CoS nanosheets. Moreover, the graphene introduced by the electrodeposition method does not generate a shielding effect on CoS, and a large number of defect sites exist, which reduce the catalytic reaction energy barrier on sulfide and greatly improve the catalytic conversion rate of polysulfide. In addition, the nanosheet-shaped CoS is tightly fixed and wrapped by the RG layer and is integrated on the carbon nanofiber membrane through electrodeposition, the wrapping of the RG layer not only introduces defect sites to obtain more coupling interfaces, but also effectively improves the conductivity of the CoS, and the coupling of the two different materials can effectively catalyze polysulfide, so that the shuttle effect is further reduced, and the shuttle effect is improvedHigh utilization rate of polysulfide. CoS nanosheets exposed to RG defects easily adsorb Li⁺Thereby promoting S₈Conversion to Li₂And S. The graphene layer not only improves the conductivity of the material, but also promotes Li⁺Thereby synergistically reducing Li₂The decomposition energy barrier of S. The synergistic effect of the two materials can greatly improve the electrochemical performance of the Li-S battery.

In order to achieve the above purpose, the invention provides the following technical scheme:

a preparation method of a positive electrode side interlayer material for a lithium-sulfur battery comprises the following steps of firstly, preparing a PAN (polyacrylonitrile) nanofiber membrane through electrostatic spinning, and obtaining a carbon nanofiber membrane through hot pressing, pre-oxidation and carbonization; then, taking a mixed aqueous solution of cobalt salt and TU (thiourea) as an electrodeposition solution (electrolyte), and electrodepositing CoS nanosheets on the carbon nanofiber membrane electrode by adopting a three-electrode electrodeposition system to obtain a CoS @ C membrane; thirdly, with GO and LiClO₄The mixed aqueous solution is electrodeposition solution (electrolyte), a three-electrode electrodeposition system is adopted to perform electrodeposition on a CoS @ C membrane electrode and reduce graphene oxide, and finally LiClO is used₄The aqueous solution is used as electrolyte, and a three-electrode system is adopted to further reduce the graphene oxide deposited on the CoS, so that the RG @ CoS @ C interlayer film material is obtained.

A preparation method of a positive electrode side interlayer material for a lithium-sulfur battery comprises the following steps:

1) sequentially adding polyacrylonitrile and a solvent into a silk mouth bottle, magnetically stirring the polyacrylonitrile and the solvent at 60-80 ℃ for 6 hours to obtain a light yellow transparent viscous membrane liquid, and carrying out electrostatic spinning to obtain a PAN nanofiber membrane; the mass ratio of polyacrylonitrile to a solvent in the membrane liquid is 1: 1-1: 30; the solvent is N, N-dimethyl formyl or dimethyl sulfoxide;

2) carrying out hot pressing on the obtained PAN nanofiber membrane for 2-20min at normal temperature, then carrying out pre-oxidation through a muffle furnace, and then carrying out carbonization under the protection of argon/nitrogen atmosphere to obtain a carbon nanofiber membrane;

3) using the carbon nanofiber membrane obtained in the step 2) as a working electrode, using an Ag/AgCl electrode as a reference electrode, using a graphite rod as a counter electrode to construct a three-electrode standard glass electrolytic cell, preparing a mixed aqueous solution of a cobalt salt with the concentration of 1-20 mM and TU with the concentration of 0.1-10M as an electrodeposition solution, electrodepositing a CoS nanosheet on the carbon nanofiber membrane electrode by adopting a cyclic voltammetry method, and then cleaning and vacuum drying to obtain a CoS @ C membrane;

4) preparing M LiClO with the concentration of 0.01-5₄And taking a mixed aqueous solution of Graphene Oxide (GO) with the concentration of 0.1-10 mg/mL as an electrodeposition solution, taking the CoS @ C film obtained in the step 3) as a working electrode, an Ag/AgCl electrode as a reference electrode, a graphite rod as a counter electrode to construct a three-electrode standard glass electrolytic cell, electrodepositing and reducing the graphene oxide on the CoS @ C film electrode by adopting a constant voltage method, cleaning after the electrodeposition is finished, and performing cleaning on 1.0-5.0M LiClO₄The graphene oxide deposited on the CoS is further reduced in the three-electrode electrolytic cell, and then cleaning and vacuum drying are carried out to obtain the RG @ CoS @ C interlayer film material.

Furthermore, in the step 3), the range of the scanning rate of the cyclic voltammetry for electrodeposition is 1-50 mV/s, the range of the voltage is-1.5-0.5V vs. SCE, and the range of the number of scanning cycles is 1-50 cycles.

Furthermore, in the step 4), the voltage range of the constant voltage method for electrodepositing and reducing the graphene oxide is-0.1 to-10V vs. SCE, and the time range is 10 to 600 s; the voltage range of the graphene oxide further reduced and deposited on the CoS is-1 to-2V vs. SCE, and the time range is 30 to 180s

Further, in step 3) and step 4), the vacuum drying conditions are as follows: the drying temperature is 50-80 ℃, and the drying time is 8-24 h.

Further, the pre-oxidation conditions are as follows: raising the temperature from room temperature to the pre-oxidation temperature at the temperature raising rate of 1-3 ℃ for min^-1The pre-oxidation temperature is 200-300 ℃, the pre-oxidation time is 1.5-4h, and the cooling rate from the pre-oxidation temperature to the room temperature is 1-10 ℃ for min^-1。

Further, the carbonization conditions are: heating from room temperature to carbonization temperature at a heating rate of 2-10 deg.C for min^-1The carbonization temperature is 700-900 ℃, the carbonization time is 1-2h, and the cooling rate from the carbonization temperature to the room temperature is 1-10 ℃ for min^-1。

Further, the step 2) further comprises cutting the pre-oxidized PAN nanofiber membrane into circular disks.

Furthermore, the molar concentration ratio of the TU to the cobalt salt in the mixed aqueous solution of the cobalt salt and the TU is 100: 1-200: 1. The cobalt salt is C DEG C l₂、Co(SO₄)₂Or Co (NO)₃)₂。

Further, at least one electrodeposition is performed in step 3) and step 4).

The invention also provides an application of the positive electrode side interlayer material obtained by the preparation method in a lithium-sulfur battery.

The beneficial effects of the invention include:

the method takes polyacrylonitrile, cobalt salt, Thiourea (TU) and graphene oxide as raw materials, obtains an RG @ CoS @ C interlayer membrane material (an interlayer material on the positive electrode side of the lithium sulfur battery) with a shuttle releasing effect by electrostatic spinning, pre-oxidation, carbonization, electrodeposition CoS, electrodeposition and reduction of the graphene oxide, and relieves the shuttle effect of the lithium sulfur battery by the RG @ CoS @ C interlayer with polysulfide adsorption and polysulfide catalytic conversion, thereby improving the performance and the service life of the battery. The complex network structure of the carbon nanofiber membrane shortens the transmission distance of lithium ions and electrons, and CoS nanosheets and graphene covering layers obtained through electrodeposition provide a large number of reaction sites for adsorption and catalytic conversion of polysulfides.

The invention simplifies the preparation method of the interlayer material and prepares the multifunctional interlayer material. The material is applied to the lithium-sulfur battery, so that the problems of poor conductivity, shuttle effect and the like in the process of charging and discharging sulfur are effectively solved, the cycling stability, the rate capability and the coulombic efficiency of the battery are improved, and the excellent electrochemical performance is displayed. Under the current density of 1.0C, after the battery with the RG @ CoS @ C interlayer circulates for 120 circles, the specific capacity is 912mA h g^-1The capacity loss rate of each circle is 0.02%, the coulombic efficiency is close to 100%, and the specific capacity is 824mA h g after the interlayer battery of CoS (CoS @ C) is only deposited for 120 circles^-1And after the battery assembled by the pure carbon film interlayer circulates for 120 circles under the current density of 1.0 ℃, the specific capacity is only 664mA h g^-1(ii) a In rate capability test, RGSpecific capacity of @ CoS @ C interlayer battery is maintained at 637mA h g under 2.0C current density^-1When the current density is recovered to 0.1C, the specific capacity can be kept at 954mA h g^-1And the specific capacity of the CoS @ C interlayer battery is maintained at 677mA h g under the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity can be kept at 857mA h g^-1The specific capacity of the pure carbon film assembled battery is only maintained at 648mA h g at the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity only reaches 896mA h g^-1。

Drawings

Fig. 1 is a scanning electron microscope image of the front side barrier material for a lithium sulfur battery prepared in example 1.

FIG. 2 is a graph of the cycling performance at 1.0C current density for example 1 lithium sulfur cells assembled with RG @ CoS @ C separators and comparative cells.

Fig. 3 is a graph of rate performance for a lithium sulfur battery of example 1 incorporating an RG @ CoS @ C separator and a comparative battery.

Fig. 4 is a graph of the charge and discharge of the assembled RG @ CoS @ C lithium sulfur battery of example 1.

Detailed Description

The experimental protocol of the present invention will be further illustrated with reference to the following examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials or the apparatus can be obtained commercially without specific mention.

Example 1

1. Preparation of positive side interlayer material for lithium-sulfur battery

1) 1.0g of polyacrylonitrile and 10g N, N-dimethylformamide were added in this order to a 20ml sample bottle, and this was magnetically stirred at 60 ℃ for 6 hours to give a pale yellow transparent dope solution. The membrane liquid is put into a 10mL medical injector and is connected with a metal spinning needle with the diameter of 0.5 mm. The distance of the needle from the rolling receiver was 15 cm. The loading voltage is 16KV, and the pushing pump is used for 0.003mL min^-1The speed of the injector is pushed, and the PAN nanofiber membrane is obtained through electrostatic spinning;

2) carrying out hot pressing on the obtained PAN nanofiber membrane for 2min at normal temperature under the pressure of 5Mpa, then carrying out pre-oxidation through a muffle furnace, cutting the PAN fiber membrane into a wafer with the diameter of 19mm after the pre-oxidation is finished, using the wafer as a battery anode side interlayer, and finally carbonizing the cut PAN fiber membrane in a tubular furnace under the protection of argon/nitrogen atmosphere, wherein the carbonization temperature is 800 ℃, and the carbonization time is 1h, so as to obtain a carbon nanofiber membrane wafer;

3) and 3) constructing a 50mL three-electrode standard glass electrolytic cell by using the carbon nanofiber membrane wafer obtained in the step 2) as a working electrode, an Ag/AgCl electrode as a reference electrode and a graphite rod as a counter electrode. The solution was prepared to contain 5mM CoCl₂And 0.75M TU in water as an electrodeposition bath, 50mL of electrolyte was used for each electrodeposition. And depositing cobalt sulfide nanosheets on the carbon nanofiber membrane electrode by adopting a cyclic voltammetry method. Setting the scanning speed to be 5mV/s, the voltage range to be-1.24-0.16V vs. SCE, the number of scanning cycles to be 7 cycles, carrying out electrodeposition for 1 time, soaking and cleaning the membrane material by deionized water for 1 hour after the electrodeposition is finished, and then flushing the membrane material by the deionized water for 3-5 times. And finally, putting the film into a vacuum oven at 60 ℃ and drying for 12 hours to obtain the CoS @ C film.

4) Preparing a mixture containing 0.1M LiClO₄0.7mg/mL of Graphene Oxide (GO) electrolyte for electrodeposition of graphene. Each time with 25mL of electrolyte. And 3) constructing a 25mL three-electrode standard glass electrolytic cell by using the CoS @ C film obtained in the step 3) as a working electrode, an Ag/AgCl electrode as a reference electrode and a graphite rod as a counter electrode. In an electrochemical workstation, a constant voltage method is adopted for electrodeposition and graphene oxide is reduced simultaneously, wherein the voltage is-1.2V vs. SCE, the time is 180s, and the electrodeposition is carried out for 1 time. After the electrodeposition was complete, the resulting film was washed with deionized water and then washed with 25mL of 1M LiClO₄Further reducing the graphene oxide deposited on the cobalt sulfide in the three-electrode electrolytic cell. Wherein the voltage is-1.2V vs. SCE and the time is 60 s. Washing with deionized water for several times. And finally, putting the film into a vacuum oven at 60 ℃ and drying for 12 hours to obtain the RG @ CoS @ C film, wherein a scanning electron microscope picture is shown in figure 1, and an RG covering layer is tightly wrapped on a CoS nano sheet in situ.

2. Preparation of pure carbon Membrane Barrier Material (not in accordance with the invention)

The pure carbon membrane separation layer material is formed by splitting a carbon nanofiber membrane in an RG @ CoS @ C membrane material to be independently used as a battery positive electrode side separation layer, and the operation effect of the pure carbon membrane separation layer material is obviously lower than that of the RG @ CoS @ C separation layer, as shown in figures 2 and 3.

Preparation of CoS @ C Barrier Material (not inventive)

The CoS @ C interlayer is formed by splitting a CoS @ C film, which is formed by only depositing CoS on a carbon nanofiber film in an RG @ CoS @ C film and not depositing graphene, and is independently used as a battery positive electrode side interlayer, and the operation effect of the CoS @ C interlayer is obviously lower than that of the RG @ CoS @ C film material, as shown in figures 2 and 3.

4. Preparation of lithium-sulfur battery by RG @ CoS @ C interlayer

10mg of polyvinylidene fluoride is dissolved in 700 mu L N-methyl pyrrolidone, and then 90mg of C/S composite material is added and stirred to obtain C/S composite slurry. The 14. mu. L C/S composite slurry was applied to one side of an aluminum foil (a disk having a diameter of 12 mm), and dried in vacuum to obtain a positive electrode for a lithium-sulfur battery. Assembling the battery in a glove box, wherein a lithium sheet is a negative electrode, Celgard 2325 is a diaphragm, RG @ CoS @ C is placed between a positive electrode and the Celgard 2325 diaphragm as an interlayer, the electrolyte is a non-aqueous phase electrolyte, 1,3 epoxy pentanes/ethylene glycol dimethyl ether (volume ratio 1:1) solution containing 1M lithium bistrifluoromethylenesulfonamide (LiTFSI), and 1% of LiNO is added₃The additive of (1).

5. Preparation of lithium-sulfur battery with pure carbon film interlayer

Other conditions were unchanged, and the RG @ CoS @ C barrier was replaced with a pure carbon film barrier.

6. Preparation of lithium-sulfur battery by CoS @ C interlayer

Other conditions were unchanged, and the RG @ CoS @ C spacer was replaced with a CoS @ C spacer.

7. Battery performance testing

After the battery is kept still for 12 hours, the constant current charge-discharge cycle performance test and the multiplying power performance test are completed through a blue test system, and the test voltage window is 1.7-2.8V. The current density of the multiplying power performance test is 0.1C, 0.2C, 0.5C, 1.0C, 2.0C (1C is 1675mA h g^-1). The cyclic voltammogram was measured by an electrochemical workstation at a scan rate of 0.05mV s^-1. FIG. 2 is a graph showing the cycle performance of the RG @ CoS @ C, CoS @ C and pure carbon film cell assembled in this example, and the RG @ CoS @ C interlayer cell at a current density of 1.0CAfter circulating for 120 circles, the specific capacity is 912mA h g^-1The capacity loss rate of each circle is 0.02%, the coulombic efficiency is close to 100%, and the specific capacity is 824mA h g after the CoS @ C interlayer battery only depositing CoS circulates for 120 circles^-1After the battery with the pure carbon film as the interlayer assembly is cycled for 120 circles under the current density of 1.0 ℃, the specific capacity is only 664mA h g^-1(ii) a FIG. 3 is a graph showing the rate capability test of the RG @ CoS @ C, CoS @ C and pure carbon film battery assembled in the present embodiment, wherein the specific capacity of the RG @ CoS @ C interlayer battery is maintained at 637mA h g under the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity can be kept at 954mA h g^-1The specific capacity of the CoS @ C interlayer battery is maintained at 677mA h g under the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity can be kept at 857mA h g^-1The specific capacity of the pure carbon film assembled battery is only maintained at 648mA h g at the current density of 2.0C^-1When the current density is recovered to 0.1C, the specific capacity only reaches 896mA h g^-1. FIG. 4 is a charging and discharging curve diagram of the assembled RG @ CoS @ C interlayer lithium-sulfur battery of the present embodiment, two discharging platforms can be observed, and the potential ranges are 2.4-2.3V and 2.1-2.0V; a charging platform, the potential interval is 2.4-2.2V.

Finally, it should be noted that: the above embodiment is only one of specific implementation manners of the present invention, and although the description thereof is more specific, the present invention should not be construed as limiting the scope of the present invention. It should be understood by those skilled in the art that the equivalent substitutions and modifications of the present invention can be made without departing from the technical scope of the present invention, and the present invention still belongs to the protection scope of the present invention.