AU2021101671A4 - The Preparation Method For A Positive Electrode-Interlayer Integrated Membrane Material Applied To Lithium-Sulfur Batteries And Its Application - Google Patents

The Preparation Method For A Positive Electrode-Interlayer Integrated Membrane Material Applied To Lithium-Sulfur Batteries And Its Application Download PDF

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AU2021101671A4
AU2021101671A4 AU2021101671A AU2021101671A AU2021101671A4 AU 2021101671 A4 AU2021101671 A4 AU 2021101671A4 AU 2021101671 A AU2021101671 A AU 2021101671A AU 2021101671 A AU2021101671 A AU 2021101671A AU 2021101671 A4 AU2021101671 A4 AU 2021101671A4
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membrane
lithium
positive electrode
integrated membrane
carbon
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Yan Dai
Gaohong HE
Fulin JIANG
Xiaobin Jiang
Xiangcun LI
Xuemei Wu
Wu Xiao
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Dalian University of Technology
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/581Chalcogenides or intercalation compounds thereof
    • H01M4/5815Sulfides
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139Processes of manufacture
    • H01M4/1397Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/362Composites
    • H01M4/366Composites as layered products
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M2004/021Physical characteristics, e.g. porosity, surface area
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material
    • H01M2004/026Electrodes composed of or comprising active material characterised by the polarity
    • H01M2004/028Positive electrodes

Abstract

The present invention discloses the preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries and its application. The integrated membrane material provided by the present invention refers to forming a carbon membrane after solvent-phase inversion and carbonization of polyacrylonitrile/carbon nanotubes composite membrane solution, and then coating an organic membrane solution on the surface of the carbon membrane to prepare an integrated membrane which has been covered with an organic membrane on the surface of the porous carbon membrane. The integrated membrane material plays dual functions of positive electrode and diaphragm, which are conducive to ion transport. The organic membrane plays function of battery diaphragm, and the carbon membrane, which can load sulfur, can be used as a positive electrode of lithium-sulfur battery; and the nanoparticles can be added in the carbon membrane to adsorb polysulfides, and mitigate the shuttle effect of the lithium-sulfur battery, as well as improve the cycling stability, the rate capability, and the coulomb efficiency of the battery. The lithium-sulfur battery prepared by utilizing such integrated membrane electrode material has excellent energy storage properties. In addition, the specific capacity can reach up to 890 mA h g-1 after cycling for 100 cycles at the electric current density of 0.2 C, and the capacity loss rate per cycle is 0.21%, as well as the coulomb efficiency can be approximate to 100%. 1/2 9/25/2019 - HV WID mag - spot - 2pm - 452:21 PM 3 00 kV 5 7 MM 40 000 x 3.0, DLUT Figure 1 - 1600 :1400 1200 -80 Integrated Membrane Electrode 411W 60 o 800 Non-integrated Membrane Electrode 600 -- 40 400 20 200 0 20 40 60 80 100 Cycle number Figure 2

Description

1/2
9/25/2019 - HV WID mag - spot - 2pm - 452:21 PM 3 00 kV 5 7 MM 40 000 x 3.0, DLUT
Figure 1
- 1600 :1400 1200 -80 Integrated Membrane Electrode
411W 60 o 800 Non-integrated Membrane Electrode 600 -- 40 400 20 200
0 20 40 60 80 100 Cycle number
Figure 2
Descriptions
The Preparation Method for a Positive Electrode-Interlayer Integrated Membrane Material Applied to Lithium-sulfur Batteries and Its Application
Technical Field The present invention relates to the field of lithium-sulfur battery positive electrode materials and interlayers, particularly to a preparation method of utilizing polyacrylonitrile/carbon nanotubes composite material as a lithium-sulfur battery positive electrode-interlayer integrated membrane material.
Background Technology With the rapid development of the global economy and the demand for energy is increasing, the large-scale exploitation and application of fossil fuels will not only cause the rapid exhaustion of earth resources, but also generate plenty of environmental pollutants. Moreover, the discontinuity and instability of electrical energy output from renewable clean energy sources such as solar and wind energy make such clean energy sources hard to be fully utilized. Thus, developing a high-capacity energy storage equipment to store and reuse discontinuous and unstable electrical energy is an effective way to solve this problem. In addition, the development of a new generation of electro-mobiles, hybrid electric vehicles and portable electronic equipment, that proposes higher requirements to the battery life, has triggered continuous exploration of cost-effective storage devices. Thus, secondary batteries are important energy storage devices in the field of new energy, which mainly consist of lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries, etc. Wherein, the lithium-ion battery has been widely applied in the fields of electronic products, new energy automobiles, and unmanned aerial vehicles, etc., due to it has such advantages as having high energy density, high charging efficiency, good temperature characteristics, low self-discharge and without memory effects, etc., but the energy density of traditional lithium-ion positive electrode materials including LiCoO2, LiMn204, LiFePO4, etc., is close to its theoretical limit. Thus, it is necessary to explore and develop a new generation of lithium battery materials with high-capacity to promote the wide application of new energy equipment urgently. As the sulfur is plentiful in the world (which accounts for 0.048% of the earth's crust), which is a by-product of petroleum refining, and is low-cost, lithium-sulfur batteries use sulfur as the positive electrode material, and the theoretical specific capacity of which reaches up to 1675 mA h g-1, and is 5-10 times of the battery capacity of existing lithium-ion batteries, meanwhile, the theoretical energy density of lithium-sulfur batteries can reach up to 2600 Wh kg-1, which is much higher than that of lithium-ion batteries. More and more scholars are turning their attention to Lithium-sulfur batteries, due to they are low-cost, with high content of sulfur in raw materials, and are eco-friendly, as well as have high theoretical capacity. The shuttle effect of polysulfides is the biggest problem needs to be addressed during the practical application of lithium-sulfur batteries. During the discharge process of lithium-sulfur batteries, the sulfur existed on the positive electrode will generate polysulfides (Li 2Sn, 4$n-8). Polysulfides can be freely soluble in the electrolyte, which will dissolve and diffuse in the electrolyte, and may pass through the diaphragm, and thus reach the negative electrode. And the polysulfides existed on the negative electrode are reduced to short-chain Li 2S and Li 2S 2, and the insulating Li 2S and Li 2S 2 will be deposited on the surface of lithium. The shuttle effect of polysulfides occurred on the negative electrode is reduced to the short-chain Li2S and Li2S2, and the insulatingLi2S and Li2S2 will be deposited on the lithium surface. The shuttle effect of polysulfides will cause the loss of electrolyte and the reduction of active materials, and accelerate the growth of negative electrode lithium dendrites, and thus make the battery generate self-discharge phenomenon, reduce coulombic efficiency, and shorten cycle life, as well as reduce safety performance. For the modification of positive electrode materials of lithium-sulfur batteries, adding an interlayer is an effective method to mitigate the shuttle effect of lithium-sulfur batteries. Current studies focus on the improvement and optimization of a single factor, but are with limited success. However, utilizing various methods for improvement simultaneously would increase the complexity of the battery structure and rise the difficulty of operation. How to optimize the structure of the positive electrode material and the interlayer and simplify the operation steps is of great significance to the practical application of lithium-sulfur batteries.
Summary of the Invention Aiming at the aforesaid problems, the present invention proposes a concept of integrating the positive electrode and the interlayer. It also provides a preparation method for a positive electrode-interlayer integrated membrane material for lithium-sulfur batteries (polyacrylonitrile/carbon nanotubes integrated membrane material) and its application, wherein, the positive electrode-interlayer integrated membrane material for lithium-sulfur batteries is prepared by taking polymer Acrylonitrile and carbon nanotubes as raw materials, and then adding different kinds of particulate materials that can adsorb polysulfides in the raw material solution, after that, obtaining a polyacrylonitrile/carbon nanotubes composite carbon-based material with a porous network structure by means of solvent phase inversion and carbonization, and thus forming an organic/electrodeless integrated membrane material after coating organic membrane solution (casting solution). The positive electrode-interlayer integrated membrane material simplifies the battery structure, which can effectively mitigate the shuttle effect, and improve the conductivity and ion transport rate. The integrated membrane material can be applied to lithium-sulfur batteries and has excellent cycling stability, rate capability, coulomb efficiency and high charge and discharge capacity. For the purpose of achieving the aforesaid objectives, the present invention provides following technical scheme: The preparation method for a positive electrode-interlayer integrated membrane material (polyacrylonitrile/carbon nanotubes integrated membrane material) applied to lithium-sulfur batteries, which consists of following steps: 1) Add N, N-dimethylformamide and polyethylene glycol to the reagent bottle with screw cap in turn, and thus obtain solvent a. After that, dissolve the carbon nanotubes and polyacrylonitrile in the reagent bottle with screw cap containing solvent a successively, then, conduct magnetic stirring to the reagent bottle with screw cap for 10-12 hours at the temperature of 60-80°C, and thus obtain the casting solution. Wherein, a part of the casting solution will be used to prepare a membrane on the glass plate through membrane casting equipment, and then, put the glass plate carrying membrane in the phase inversion solvent to complete phase inversion for 20-24 hours; and the material mass ratio of N, N-dimethylformamide, polyethylene glycol, carbon nanotubes and polyacrylonitrile dissolved in the casting solution is 7:0.5:1:1 - 9:0.7:1:1; for example, 8.4g: 0.6g: ig: ig; 2) Conduct vacuum drying to the material after phase inversion, and then perform pre-oxidation in a muffle furnace, and finally complete carbonization in a tube furnace under the protection of an argon/nitrogen atmosphere, and thus obtain the polyacrylonitrile/carbon nanotubes composite carbon-based material; 3) Coat the casting solution obtained from step 1) on the surface of the polyacrylonitrile/carbon nanotubes composite carbon-based material, and then put the coated membrane in the phase inversion solvent to complete phase inversion for 20-24 hours, then, take it out, and conduct vacuum drying to the membrane, and thus obtain a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries. (polyacrylonitrile/carbon nanotube integrated membrane material). Further, in step 1), the thickness of the membrane obtained by the said membrane casting equipment is 100-300 m, and the ion transfer resistance is low, as well as the battery performance is more excellent. Further, the coating thickness of the casting solution coated on the surface of the polyacrylonitrile/carbon nanotubes composite carbon-based material is 100-300 im, which has a more excellent effect of preventing battery short circuit. Further, in step 1) the casting solution obtained from step 1) further consists of nanoparticles, which would be finally dissolved in solvent a, and the said nanoparticles, such as TiO 2 , SiO 2 , SnO2, CeO2, MnO2, etc., have adsorption function to polysulfides.
Further, in step 1) and step 3), the said phase inversion solvent is one of n-amyl alcohol or water. Further, in step 2) and step 3), the said vacuum drying conditions are: the drying temperature is at 70-90 0C and the drying time is 2-4 hours. Further, in step 2), the said pre-oxidation conditions are: heating up from the room temperature to the pre-oxidation temperature, wherein, the heating rate is 1.5-3C min-1, and the pre-oxidation temperature is at 200-300 0C, as well as the pre-oxidation time is 1.5-4 hours, in addition, the cooling rate of the temperature dropped from the pre-oxidation temperature to the room temperature is 1-10°C min-. Further, in step 2), the said carbonization conditions are: heating up from the room temperature to the carbonization temperature, wherein, the heating rate is 4-60 C min-1, and the carbonization temperature is at 700-900 0C, as well as the carbonization time is 1-2 hours, in addition, the cooling rate of the temperature dropped from the carbonization temperature to the room temperature is1-10°C min-. The present invention also provides an integrated membrane electrode, which is obtained through applying C/S composite slurry on the inorganic layer side (composite carbon-based material side) of the integrated membrane material and then conducting vacuum drying; wherein, the C/S composite slurry consists of polyvinylidene fluoride, N-Methyl pyrrolidone and C/S composite materials. The beneficial effects of the present invention include: The present invention uses polyacrylonitrile and carbon nanotubes as raw materials, and then obtains a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries (polyacrylonitrile/carbon nanotubes integrated membrane material) through a series of processes including phase inversion, carbonization, and coating of organic membrane solution (casting solution). Such integrated membrane material consists of an organic layer and an inorganic layer, wherein, part of pores on the organic layer are dense, which play the function of interlayer, while part of pores on the inorganic layer are sparse, which can be used as the main material for loading sulfur by positive electrode. In addition, the integrated membrane material takes carbon-based material, which adopt an interlaced and interconnected pore structure, as the main body. Carbon materials have good electrical conductivity and low density, which can effectively increase the energy density of mass of electrode. The present invention integrates the positive electrode and the interlayer of the lithium-sulfur battery to simplify the battery structure, and the prepared integrated membrane material plays dual functions of the positive electrode and the interlayer. Such material can be applied to lithium-sulfur batteries, which may effectively solve the problems of volume expansion, poor conductivity, and shuttle effect, etc., occurred during the charge and discharge of sulfur, meanwhile, improve the cycling stability, the rate capability and the coulomb efficiency of the battery, and thus manifest excellent electrochemical performance. In addition, the specific capacity of the integrated membrane electrode can reach up to 890 mA h g-1 after cycling for 100 cycles at the electric current density of 0.2 C, and the capacity loss rate per cycle is 0.21%, as well as the coulomb efficiency can be approximate to 100%, however, the specific capacity of the non-integrated membrane electrode can reach up to 722 mA h g-1 after cycling for 100 cycles at the electric current density of 0.2 C. Furthermore, during the rate capability test, the specific capacity of the integrated membrane electrode can be maintained at 665 mA h g-1 at the electric current density of 2 C, which can also be maintained at 980 mA h g-1 when the electric current density returns to 0.1 C, on the contrary, the specific capacity of the non-integrated membrane electrode only can be maintained at 600 mA h g-1 at the electric current density of 2 C, and would only reach 860 mA h g-1 when the electric current density returns to 0.1 C.
Brief Description of the Drawings Figure 1 is a scanning electron microscopy image of the positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries prepared in Embodiment 1. Figure 2 is a cycling performance graph of the lithium-sulfur battery with integrated membrane electrode or non-integrated membrane electrode assembled in Embodiment 1 at the electric current density of 0.2 C. Figure 3 is a rate capability graph of the lithium-sulfur battery with integrated membrane electrode or non-integrated membrane electrode assembled in Embodiment 1. Figure 4 is a curve chart of charge and discharge of the lithium-sulfur battery with integrated membrane electrode assembled in Embodiment 1.
Detailed Description of the Presently Preferred Embodiments The text below will further illustrate the experimental scheme of the present invention in conjunction with specific embodiments, however the present invention is not limited to the following embodiments. Unless otherwise specified, the said methods are all conventional methods. In addition, unless otherwise specified, the said raw materials or instruments can be obtained through purchasing.
Embodiment 1 1. The preparation of a positive electrode-interlayer integrated membrane electrode material applied to lithium-sulfur batteries 1) Add 21 g of N, N-dimethylformamide and 1.5 g of polyethylene glycol to the reagent bottle with screw cap of 100 mL in turn, and thus obtain solvent a. After that, add 2.5 g of carbon nanotubes to solvent a, and then add 2.5 g of polyacrylonitrile after stirring for dissolution, and then, stir and dissolve them, after that, conduct magnetic stirring to the reagent bottle with screw cap for 12 hours at the temperature of 80C, and thus obtain the homogeneous black casting solution. Wherein, a part of casting solution will be used to prepare a membrane with the thickness of 300 pm on the glass plate through the membrane casting equipment, and then, put the glass plate covering membrane in the n-amyl alcohol quickly to complete phase inversion for 24 hours; 2) Take out the phase-inverted membrane, and dry it on the glass plate, and then conduct vacuum drying at the temperature of 90 °C. After that, put the dried membrane in a muffle furnace to complete pre-oxidation, wherein, the temperature would rise to 250 °C at a heating rate of 2°C min-, and keep the constant temperature for 2 hours. Finally, complete carbonization of the materials in a tube furnace under the protection of an argon atmosphere, wherein, the temperature would rise to 800 °C at a heating rate of 5 °C min-1
, and keep the constant temperature for 1 hour, and thus obtain the polyacrylonitrile/carbon nanotubes composite carbon-based material; and the sulfur content loaded on the carbon membrane can reach up to 1.5 mg/cm 2 , furthermore, due to it adopts porous structure, the transfer resistance of carbon membrane ion and electrolyte is low. 3) Coat the casting solution obtained from step 1) on the surface of the polyacrylonitrile/carbon nanotubes composite carbon-based material, and the thickness of coating is 100 im, and then put the coated material in the n-amyl alcohol to complete phase inversion for 24 hours, after that, conduct vacuum drying at the temperature of °C, and thus obtain a positive electrode-interlayer integrated membrane material (polyacrylonitrile/carbon nanotubes integrated membrane material) applied to lithium-sulfur batteries. Figure 1 is a scanning electron microscopy image of the cross-section of positive electrode-interlayer integrated membrane material, from which, the microstructure, and the dense organic layer as well as the sparse inorganic layer of the successfully prepared integrated membrane material can be clearly observed. 2. The preparation of non-integrated membrane material preparation (do not described in the present invention) The non-integrated membrane material refers to separating the inorganic carbon membrane layer (polyacrylonitrile/carbon nanotubes composite carbon-based material layer) from the organic coating layer (the membrane layer coated with the casting solution) of the integrated membrane, wherein, the inorganic carbon layer is used as a current collector, and the organic coating layer is used as an interlayer. However, as shown in Figures 2 and 3, the operation effect of battery is significantly poor than that of the integrated membrane material. 3. Preparing the lithium-sulfur battery with the integrated membrane electrode material Take 10 mg of polyvinylidene fluoride to dissolve in 700 tL of N-Methyl pyrrolidone, and then add 90 mg of C/S composite materials, stir them, and thus obtain a C/S composite slurry. Take 14 tL of C/S composite slurry and apply it on the inorganic layer side of the integrated membrane material (integrated membrane wafer with a diameter of 1 cm), and then, conduct vacuum drying, as well as use the product as an integrated membrane electrode. After that, assemble the battery in the glove box, wherein, the lithium tablets are served as the negative electrode, and the Celgard 2325 is used as the diaphragm, as well as the electrolyte utilized is non-aqueous electrolyte, which refers to the 1, 3 epoxy oxolane/ethylene glycol dimethyl ether solution (with the volume ratio of 1:1) containing IM of Lithium bis(trifluoromethanesulfonyl) (LiTFSI) after added 1% LiNO3 additive. In addition, the C/S composite slurry is coated on the inorganic carbon layer. 4. Preparing the lithium-sulfur battery with the non-integrated membrane electrode material Coat the C/S composite slurry on the inorganic carbon layer. Wherein, take 100 pm of organic membrane to be used as the interlayer and place it between the carbon membrane and the Celgard 2325 diaphragm, meanwhile, other conditions remain unchanged, and the sulfur content loaded on the carbon membrane is 1.5 mg/cm-2 .
5. Performance test of batteries with integrated membrane electrode or non-integrated membrane electrode Keep the battery standing for 12 hours, and then perform the performance test of charge-discharge cycle of constant current and the rate capability test through the LAND test system, and the test voltage window takes 1.7 - 2.8 V. In addition, the electric current density used in the rate capability test is 0.1 C, 0.2 C, 0.5 C, 1.0 C, 2.0 C (1 C = 1675 mA h g-1). Meanwhile, an electrochemical workstation shall be utilized to test the cyclic voltammetry curve, and the scan rate is 0.05 mV s-1. Figure 2 is a cycling performance graph of the lithium-sulfur battery with integrated membrane electrode or non-integrated membrane electrode, wherein, the specific capacity of the integrated membrane electrode can reach up to 890 mA h g-1 after cycling for 100 cycles at the electric current density of 0.2 C, and the capacity loss rate per cycle is 0.21%, as well as the coulomb efficiency can be approximate to 100%, however, the specific capacity of the non-integrated membrane electrode can reach up to 722 mA h g-1 after cycling for 100 cycles at the electric current density of 0.2 C. Figure 3 is a rate capability graph of the lithium-sulfur battery with integrated membrane electrode or non-integrated membrane electrode, wherein, the specific capacity of the integrated membrane electrode can be maintained at 665 mA h g-1 at the electric current density of 2 C, which can also be maintained at 980 mA h g-1 when the electric current density returns to 0.1 C, on the contrary, the specific capacity of the non-integrated membrane electrode only can be maintained at 600 mA h g-1 at the electric current density of 2 C, and would only reach 860 mA h g-1 when the electric current density returns to 0.1 C. Figure 4 is a curve chart of charge and discharge of the lithium-sulfur battery with integrated membrane electrode, from which, two discharge platforms can be observed, and the potential range is 2.4-2.3 V and 2.1-2.0 V respectively; or one charging platform can be observed, and the potential range is 2.4-2.2 V. In conclusion, it should be noted that the aforesaid embodiment is only one of the specific implementation methods of the present invention. Although it has been described in detail specifically herein, it should not be understood as a limitation on the scope of the present invention. For those skilled in the art should understand that, without departing from the technical scope of the present invention, any equivalent replacements or modifications made to the present invention belong to the technical scheme of the present invention and shall fall within the protection scope of the present invention.

Claims (9)

Claims
1. The preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries, characterized in that consisting of following steps: 1) Add N, N-dimethylformamide and polyethylene glycol to the reagent bottle with screw cap in turn, and thus obtain solvent a. After that, dissolve the carbon nanotubes and polyacrylonitrile in the reagent bottle with screw cap containing solvent a successively, then, conduct magnetic stirring to the reagent bottle with screw cap for 10-12 hours at the temperature of 60-80C, and thus obtain the casting solution. Wherein, a part of the casting solution will be used to prepare a membrane on the glass plate through membrane casting equipment, and then, put the glass plate carrying membrane in the phase inversion solvent to complete phase inversion for 20-24 hours; and the material mass ratio of N, N-dimethylformamide, polyethylene glycol, carbon nanotubes and polyacrylonitrile dissolved in the casting solution is 7:0.5:1:1 - 9:0.7:1:1; 2) Conduct vacuum drying to the material after phase inversion, and then perform pre-oxidation in a muffle furnace, and finally complete carbonization in a tube furnace under the protection of an argon/nitrogen atmosphere, and thus obtain the polyacrylonitrile/carbon nanotubes composite carbon-based material; 3) Coating the casting solution obtained from step 1) on the surface of the polyacrylonitrile/carbon nanotubes composite carbon-based membrane, and then put the coated membrane in the phase inversion solvent to complete phase inversion for 20-24 hours, then, after an organic membrane is formed on the surface of carbon membrane, take it out, after that, conduct vacuum drying to the membrane, and thus obtain a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries.
2. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1, characterized in that: in step 1), the thickness of the membrane obtained by the said membrane casting equipment is 100-300 im.
3. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1 or 2, characterized in that: in step 3), the coating thickness of the casting solution coated on the surface of the polyacrylonitrile/carbon nanotubes composite carbon-based material is 100-300 im.
4. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1, characterized in that: the casting solution obtained from step 1) further consists of nanoparticles, which would be finally dissolved in solvent a, and the said nanoparticles have adsorption function to polysulfides.
5. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1, characterized in that: in step 1) and step 3), the said phase inversion solvent is one of n-amyl alcohol or water.
6. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1, characterized in that: in step 2) and step 3), the said vacuum drying conditions are: the drying temperature is at 70-90 0C and the drying time is 2-4 hours.
7. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1, characterized in that: in step 2), the said pre-oxidation conditions are: heating up from the room temperature to the pre-oxidation temperature, wherein, the heating rate is 1.5-30 C min-1, and the pre-oxidation temperature is at 200-300 0C, as well as the pre-oxidation time is 1.5-4 hours, in addition, the cooling rate of the temperature dropped from the pre-oxidation temperature to the room temperature is 1-10°C min-.
8. The said preparation method for a positive electrode-interlayer integrated membrane material applied to lithium-sulfur batteries according to Claim 1, characterized in that: in step 2), the said carbonization conditions are: heating up from the room temperature to the carbonization temperature, wherein, the heating rate is 4-60 C min-, and the carbonization temperature is at 700-900 0C, as well as the carbonization time is 1-2 hours, in addition, the cooling rate of the temperature dropped from the carbonization temperature to the room temperature is1-10°C min- .
9. An integrated membrane electrode, characterized in that: the integrated membrane electrode is obtained through applying C/S composite slurry on the polyacrylonitrile/carbon nanotubes composite carbon-based material side of the integrated membrane material described in claim 1 and then conducting vacuum drying; wherein, the C/S composite slurry consists of polyvinylidene fluoride, N-Methyl pyrrolidone and C/S composite materials.
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