CN115425363A - Preparation method and application of metal sulfur battery interlayer material - Google Patents

Abstract

The invention discloses a preparation method and application of a metal sulfur battery interlayer material. The preparation method comprises the following steps: uniformly dissolving inorganic tungsten salt, pore-forming template agent, polymer and auxiliary agent in solvent to prepare spinning solution, and obtaining WO by utilizing electrostatic spinning technology ₃ A nanofiber; and heating to remove the template agent, and then calcining with a vulcanizing agent to obtain the metal sulfur battery interlayer material. Ordered mesopores WO prepared in the invention ₃ /WS ₂ The heterojunction ordered mesoporous nanofiber has an ultra-large specific surface area, so that the utilization rate is high, adsorption sites and reaction sites are rich, and the mass transfer of electrolyte is facilitated. Meanwhile, WO ₃ Can enhance the chemisorption of the membrane to polysulfides, while WS ₂ The electrochemical conversion of soluble polysulfide can be promoted by catalysis, so that the shuttle of polysulfide between two electrodes is inhibited, the utilization rate of active substances is improved, and the specific capacity and the cycling stability of the metal sulfur battery are effectively improved. The method has the advantages of simple process, low cost and easy popularization.

Description

Preparation method and application of a metal-sulfur battery interlayer material

technical field

The invention relates to a preparation method of tungsten trioxide (WO ₃ )/tungsten disulfide (WS ₂ ) heterojunction ordered mesoporous nanofibers used as an interlayer of metal sulfur batteries and a metal sulfur battery, belonging to the technical field of batteries .

Background technique

In recent years, in order to reduce environmental pollution and increase the utilization rate of renewable energy, human beings have put forward higher requirements for secondary energy storage systems. As a new type of chemical power source, metal sulfur battery has been widely accepted since its inception due to its high specific capacity (theoretical specific energy is 760Wh/kg, but actually greater than 150Wh/kg), abundant reserves, low price and environmental friendliness. Attention and research have broad application prospects. However, at present, the actual energy density of metal-sulfur batteries is far lower than its theoretical value, and the cycle life is poor and the rate performance is low, which seriously hinders the industrialization process of metal-sulfur batteries. The main reason is that in the metal-sulfur battery system, lithium polysulfide, an intermediate product of charging and discharging, is easily dissolved in the ether electrolyte, and diffuses and shuttles between the positive and negative electrodes, resulting in a "shuttle effect", which leads to irreversible loss of active materials and Negative passivation seriously affects battery performance. In addition, the incomplete reduction of sulfur during discharge also greatly reduces the specific capacity of the battery.

At present, most studies on metal sulfur battery systems use polyethylene (PE) and polypropylene (PP)-based polyolefin separators, which have good electrochemical stability, high tensile strength and high Porosity and many other advantages. However, this type of material has very limited adsorption and barrier effects on soluble polysulfides. As the number of charge-discharge cycles increases, the "shuttle effect" of polysulfides becomes severe, causing the battery capacity to decline sharply and cycle stability keeps getting worse.

Contents of the invention

The technical problem to be solved by the present invention is to provide a metal-sulfur battery interlayer material, which can catalyze and promote the conversion to solid sulfur/discharge products while chemically adsorbing soluble polysulfides, so as to alleviate the "shuttle" of metal-sulfur batteries. effect".

In order to solve the above problems, the present invention provides a method for preparing interlayer materials for metal-sulfur batteries: uniformly dissolve inorganic tungsten salts, pore-forming template agents, polymers and additives in solvents to make spinning solutions, and use electrospinning Technology to obtain WO ₃ nanofibers; heating to remove the template agent and then calcining with a vulcanizing agent to obtain a metal-sulfur battery interlayer material, that is, a WO ₃ /WS ₂ heterojunction ordered mesoporous nanofiber.

Preferably, the inorganic tungsten salt is any one or more of tungsten chloride, tungsten nitrate, and tungsten acetate; the pore-forming template is any one of a triblock copolymer, a diblock copolymer or Several kinds; the polymer is any one or several of polyvinylpyrrolidone (PVP), polystyrene (PS), polymethyl methacrylate (PMMA); the auxiliary agent is any of hydrochloric acid, acetic acid, and acetylacetone One or more; the solvent is any one or more of ethanol, N,N-dimethylformamide (DMF), tetrahydrofuran, and dimethyl sulfoxide.

Preferably, the process parameters of the electrospinning are specifically: temperature 20-40° C., voltage 5-25 kV, spinning solution flow rate 0.1-5 mL/h, sample receiving distance 2-30 cm.

Preferably, the WO ₃ nanofiber is a mesoscopic structure.

Preferably, the atmosphere used for removing the template agent is any one of nitrogen, argon, and air; the temperature of the heating is 200-500° C., and the time is 0.5-5 h.

Preferably, the vulcanizing agent is any one or more of sulfur, thiourea, and hydrogen sulfide; the temperature of the calcination is 200-800°C; the time is 0.5-5h.

The present invention also provides a metal-sulfur battery interlayer material prepared by the method for preparing the metal-sulfur battery interlayer material.

The present invention also provides a method for preparing a metal-sulfur battery: uniformly mix the above-mentioned metal-sulfur battery interlayer material with a binder in a solvent, apply it on the surface of the diaphragm material, and dry it in vacuum to obtain a composite diaphragm; The carbon composite material is used as the positive electrode, the alkali metal is used as the negative electrode, and the battery composite diaphragm is assembled to form a metal-sulfur battery.

Preferably, the mass ratio of the metal-sulfur battery interlayer material to the binder is 1:(0.01-0.5); the binder is polyvinylidene fluoride (PVDF), sodium alginate, carboxymethyl cellulose ( Any one or several of CMC).

Preferably, the solvent is any one or more of 1-methyl-2-pyrrolidone (NMP), ethanol, water; the diaphragm material is any one of PP, PE, glass fiber; the alkali The metal is any one of lithium, sodium, and potassium.

The WO3/WS2 heterojunction mesoporous nanofiber material prepared by the invention can be used as a metal-sulfur battery interlayer material. The unique ordered mesoporous structure of the material makes it have a large specific surface area, which in turn has many advantages such as high utilization rate, abundant adsorption and reaction sites, and favorable mass transfer of electrolyte. At the same time, WO3 can enhance the chemical adsorption of polysulfides on the separator, while WS2 can catalyze and promote the electrochemical conversion of soluble polysulfides to improve the reaction kinetics, thereby inhibiting the dissolution and shuttling of polysulfides in the electrolyte and improving the positive electrode sulfur concentration. In order to obtain high specific capacity and good cycle stability of metal-sulfur batteries. The method of the invention has the advantages of simple process, low cost and easy popularization. The invention can improve the specific capacity of the metal-sulfur battery, reduce the polarization during charging and discharging, enhance cycle stability and service life, and comprehensively improve the electrochemical performance of the metal-sulfur battery.

Description of drawings

Figure 1 is a transmission electron microscope image of the WO ₃ /WS ₂ heterojunction mesoporous nanofiber material prepared in Example 1;

Figure 2 shows the WO ₃ /WS ₂ heterojunction mesoporous nanofiber material prepared in Example 1 as an interlayer coated on glass fiber to prepare a composite interlayer and pure glass fiber as a room temperature sodium-sulfur battery separator to assemble the battery at a current density of 0.2 Cyclic test performed under A/g conditions.

Detailed ways

In order to make the present invention more comprehensible, preferred embodiments are described in detail below with accompanying drawings.

Example 1

(1) Mix and dissolve tungsten chloride, PEO-b-PS, PVP and acetylacetone in the solvent DMF to prepare a spinning solution. Using electrospinning technology, adjust the temperature to 30°C, the voltage to 15kV, and the flow rate of the spinning solution 0.5mL/h and a sample receiving distance of 15cm, the WO ₃ nanofibers with mesoscopic structure were obtained; the obtained WO ₃ nanofibers were calcined in air at 350°C for 1 h to remove the template agent, and then accompanied by the vulcanizing agent thiourea at 600 Calcined at ℃ for 1 hour to obtain WO ₃ /WS ₂ heterojunction mesoporous nanofiber material.

(2) The obtained WO ₃ /WS ₂ heterojunction mesoporous nanofiber material and the binder PVDF are uniformly mixed in the solvent NMP at a mass ratio of 9:1, coated on the surface of commercial glass fibers, and vacuum-dried; The obtained material is used as a battery diaphragm, and the elemental sulfur/carbon nanotube composite material is used as a positive electrode, and the metal sodium is used as a negative electrode to assemble a button battery.

The morphology of the prepared ordered mesoporous WO ₃ /WS ₂ heterojunction mesoporous nanofiber material is shown in Fig. 1 . As shown in Figure 2, the electrochemical performance of the room-temperature sodium-sulfur battery added with ordered mesoporous WO ₃ /WS ₂ heterojunction mesoporous nanofiber interlayer was tested. It can be seen that its cycle performance is excellent, compared with that of pure glass fiber Compared with the room temperature sodium-sulfur battery as a separator, the performance has been significantly improved.

Example 2

(1) Mix and dissolve tungsten chloride, PEO-b-PS, PS and hydrochloric acid in the solvent DMF and ethanol mixture to prepare a spinning solution. Using electrospinning technology, adjust the temperature to 30°C and the voltage to 15kV. The silk liquid flow rate is 0.5mL/h and the sample receiving distance is 15cm, and the WO ₃ nanofibers with mesoscopic structure are obtained; the obtained WO ₃ nanofibers are calcined in air at 350°C for 1 hour to remove the template agent, and then accompanied by the vulcanizing agent Sulfur was calcined at 400°C for 1 h to obtain the target interlayer material.

(2) The obtained WO ₃ /WS ₂ heterojunction mesoporous nanofiber material and the binder PVDF are uniformly mixed in the solvent NMP at a mass ratio of 9:1, coated on the surface of commercial glass fibers, and vacuum-dried; The obtained material is used as a battery diaphragm, and the elemental sulfur/carbon nanotube composite material is used as a positive electrode, and the metal sodium is used as a negative electrode to assemble a button battery.

Example 3

(1) Mix and dissolve tungsten chloride, PEO-b-PS, PVP and hydrochloric acid in the solvent DMF and ethanol mixture to prepare a spinning solution. Using electrospinning technology, adjust the temperature to 35°C and the voltage to 18kV. The silk liquid flow rate is 0.5mL/h and the sample receiving distance is 15cm, and the WO ₃ nanofibers with mesoscopic structure are obtained; the obtained WO ₃ nanofibers are calcined in air at 350°C for 1 h to remove the template agent, and then accompanied with the vulcanizing agent sulfur Urea was calcined at 500°C for 2h to obtain the target interlayer material.

(2) The obtained WO ₃ /WS ₂ heterojunction mesoporous nanofiber material and the binder PVDF are uniformly mixed in the solvent NMP at a mass ratio of 9:1, coated on the surface of commercial glass fibers, and vacuum-dried; The obtained material is used as a battery diaphragm, and the elemental sulfur/carbon nanotube composite material is used as a positive electrode, and the metal sodium is used as a negative electrode to assemble a button battery.

The material prepared in Examples 1-3 was used as a separator for a sodium-sulfur battery at room temperature, and a button battery was assembled with a metal sodium sheet as a negative electrode. After standing for 6 hours, a cycle performance comparison experiment was performed. Experimental results show that when the materials prepared in Examples 1-3 are used as room-temperature sodium-sulfur battery diaphragm materials, compared with commercial diaphragm materials without interlayers, the room-temperature sodium-sulfur battery of the present invention has a greatly increased specific capacity, and the cycle stability And the rate performance is greatly enhanced. The reason is that the ordered mesoporous WO ₃ /WS ₂ heterojunction mesoporous nanofibers prepared in the present invention have a super large specific surface area, so the utilization rate is high, the adsorption sites and reaction sites are abundant, and it is beneficial to the mass transfer of the electrolyte. At the same time, WO ₃ can enhance the chemical adsorption of polysulfides on the separator, while WS ₂ can catalyze and promote the electrochemical conversion of soluble polysulfides, thereby inhibiting the "shuttle effect" of polysulfides, improving the utilization rate of active materials, and effectively improving the Specific capacity and cycle stability of metal-sulfur batteries.

Claims (10)

1. A preparation method of a metal sulfur battery interlayer material is characterized in that inorganic tungsten salt, a pore-forming template agent, a polymer and an auxiliary agent are uniformly dissolved in a solvent to prepare a spinning solution, and an electrostatic spinning technology is utilized to obtain WO ₃ A nanofiber; and heating to remove the template agent and then calcining with a vulcanizing agent to obtain the metal sulfur battery interlayer material.

2. The method for preparing the interlayer material of the metal-sulfur battery as claimed in claim 1, wherein the inorganic tungsten salt is one or more of tungsten chloride, tungsten nitrate and tungsten acetate; the pore-forming template agent is any one or more of triblock copolymer and diblock copolymer; the polymer is any one or more of polyvinylpyrrolidone, polystyrene and polymethyl methacrylate; the auxiliary agent is any one or more of hydrochloric acid, acetic acid and acetylacetone; the solvent is any one or more of ethanol, N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide.

3. The preparation method of the metal-sulfur battery interlayer material as claimed in claim 1, wherein the electrostatic spinning process parameters are as follows: the temperature is 20-40 ℃, the voltage is 5-25kV, the flow rate of the spinning solution is 0.1-5mL/h, and the sample receiving distance is 2-30cm.

4. The method of claim 1, wherein the WO is a process for preparing a sandwich material for a metal-sulfur battery ₃ The nanofibers are mesoscopic.

5. The method for preparing the sandwich material of the metal-sulfur battery as claimed in claim 1, wherein the atmosphere used for removing the template is any one of nitrogen, argon and air; the heating temperature is 200-500 ℃ and the time is 0.5-5h.

6. The preparation method of the metal-sulfur battery interlayer material as claimed in claim 1, wherein the vulcanizing agent is any one or more of sulfur, thiourea and hydrogen sulfide; the calcining temperature is 200-800 ℃; the time is 0.5-5h.

7. A metal-sulfur battery interlayer material prepared by the method for preparing a metal-sulfur battery interlayer material according to any one of claims 1 to 6.

8. A preparation method of a metal sulfur battery is characterized in that the metal sulfur battery interlayer material of claim 7 and a binder are uniformly mixed in a solvent, coated on the surface of a diaphragm material, and dried in vacuum to obtain a composite diaphragm; and the elemental sulfur/carbon composite material is used as a positive electrode, the alkali metal is used as a negative electrode, and the elemental sulfur/carbon composite material and the battery composite diaphragm are assembled into the metal sulfur battery.

9. The method of manufacturing a metal-sulfur battery of claim 8, wherein the mass ratio of the metal-sulfur battery interlayer material to the binder is 1: (0.01-0.5).

10. The method for preparing a metal-sulfur battery as claimed in claim 8, wherein the binder is any one or more of polyvinylidene fluoride, sodium alginate and carboxymethyl cellulose; the solvent is any one or more of 1-methyl-2-pyrrolidone, ethanol and water; the diaphragm material is any one of PP, PE and glass fiber; the alkali metal is any one of lithium, sodium and potassium.

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