阅读说明：本技术 一种锂硫电池隔膜及其制备方法和应用 (Lithium-sulfur battery diaphragm and preparation method and application thereof ) 是由 袁伟 许铭 张晓清 于 2021-07-21 设计创作，主要内容包括：本发明公开了一种锂硫电池隔膜及其制备方法和应用。本发明的锂硫电池隔膜由层叠贴合的隔层和隔膜组成,隔层为碳纳米纤维构成的网状膜,隔膜为不导电聚合物纳米纤维构成的网状膜。本发明的锂硫电池隔膜实现了隔层与隔膜的一体化,隔层和隔膜均是由纳米纤维构成的网状膜,且均具有柔性,隔层具有良好的导电性和丰富的孔结构,隔膜具有优良的化学稳定性、电解液润湿性、机械性能和热稳定性以及高的孔隙率,隔层和隔膜协同作用,有利于提升锂硫电池的性能。(The invention discloses a lithium-sulfur battery diaphragm and a preparation method and application thereof. The lithium-sulfur battery diaphragm disclosed by the invention consists of an interlayer and a diaphragm which are laminated, wherein the interlayer is a reticular film formed by carbon nanofibers, and the diaphragm is a reticular film formed by non-conductive polymer nanofibers. The lithium-sulfur battery diaphragm disclosed by the invention realizes the integration of the interlayer and the diaphragm, the interlayer and the diaphragm are both net-shaped membranes formed by nano fibers and have flexibility, the interlayer has good conductivity and rich pore structures, the diaphragm has excellent chemical stability, electrolyte wettability, mechanical property and thermal stability and high porosity, and the interlayer and the diaphragm have synergistic effect, so that the performance of the lithium-sulfur battery is favorably improved.)

1. A lithium sulfur battery separator, characterized by: the lithium-sulfur battery diaphragm consists of a laminated interlayer and a diaphragm; the interlayer is a reticular membrane formed by carbon nanofibers; the diaphragm is a reticular film formed by non-conductive polymer nano fibers.

2. The lithium sulfur battery separator according to claim 1, wherein: the barrier layer further comprises nano-titania particles.

3. The lithium sulfur battery separator according to claim 1 or 2, wherein: the separator also includes nano-silica particles.

4. The lithium sulfur battery separator according to claim 3, wherein: the non-conductive polymer is at least one of polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate and polyvinylpyrrolidone.

5. The lithium sulfur battery separator according to claim 3, wherein: the thickness of the interlayer is 2-2000 mu m; the thickness of the diaphragm is 2-2000 mu m.

6. The method for preparing the separator for a lithium-sulfur battery according to any one of claims 3 to 5, comprising the steps of:

1) dispersing organic polymer and nano titanium dioxide particles in a solvent to prepare a spinning solution I, carrying out primary electrostatic spinning to form a reticular membrane consisting of nano fibers, and carrying out heat treatment to obtain an interlayer;

2) and dispersing the non-conductive polymer and the nano silicon dioxide particles in a solvent to prepare a spinning solution II, and performing secondary electrostatic spinning on the interlayer to form a reticular membrane consisting of nano fibers, thus obtaining the lithium-sulfur battery diaphragm.

7. The method of manufacturing a lithium sulfur battery separator according to claim 6, wherein: the organic polymer in the step 1) is at least one of polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate and polyvinylpyrrolidone.

8. The method of manufacturing a lithium sulfur battery separator according to claim 6 or 7, characterized in that: the specific operation of the heat treatment in the step 1) is as follows: the reticular membrane composed of the nano-fibers is firstly placed in a muffle furnace, the temperature is raised to 220-280 ℃ at the heating rate of 1-5 ℃/min, the temperature is preserved for 1-3 h, the reticular membrane is cooled to the room temperature along with the furnace, then the reticular membrane is placed in a tubular furnace, protective gas is filled, the temperature is raised to 600-1200 ℃ at the heating rate of 1-5 ℃/min, the temperature is preserved for 1-3 h, and the reticular membrane is cooled to the room temperature along with the furnace.

9. The method of manufacturing a lithium sulfur battery separator according to claim 6 or 7, characterized in that: the mass ratio of the organic polymer to the nano titanium dioxide particles in the step 1) is 1: 0.01-1: 1; the mass ratio of the non-conductive polymer to the nano silicon dioxide particles in the step 2) is 1: 0.01-1: 1.

10. A lithium-sulfur battery comprising the lithium-sulfur battery separator according to any one of claims 1 to 5.

Technical Field

The invention relates to the technical field of lithium-sulfur batteries, in particular to a lithium-sulfur battery diaphragm and a preparation method and application thereof.

Background

With the rapid development of world science and technology and industry, people's demand for new energy is increasing, and the development of high-efficiency and large-capacity energy storage devices becomes a research hotspot. The lithium ion battery occupies a dominant position in the field of energy storage, but because the lithium ion battery has the defects of high electrode material cost, low charging and discharging specific capacity and the like, the lithium ion battery is difficult to meet the increasing practical application requirements. The lithium-sulfur battery is a battery taking sulfur as a battery anode and metal lithium as a battery cathode, and the active substance sulfur in the battery has the advantages of high theoretical specific capacity, low price, rich reserves, environmental friendliness and the like, so the lithium-sulfur battery has better application prospect and is expected to realize commercialization.

Lithium-sulfur batteries undergo a series of complicated electrochemical reactions during charging and discharging, and are prone to problems that limit practical applications, such as: the "shuttle effect" of polysulfides, the insulation of the active material sulfur and its charge and discharge products, the generation of lithium dendrites by the lithium metal negative electrode, etc., which problems ultimately result in the performance of lithium sulfur batteries being severely affected. The barrier layer is arranged between the positive electrode and the diaphragm to inhibit the shuttle effect of polysulfide, so that the utilization rate of the positive electrode active material of the lithium-sulfur battery is improved, which is a common solution at present. However, most of the barrier layers arranged at present have the problems of poor conductivity, unsatisfactory adsorption effect on polysulfide, poor wettability of electrolyte, poor thermal stability, poor mechanical property and the like, and the arrangement of the single barrier layer can also increase the assembly difficulty of the lithium-sulfur battery, increase extra assembly cost and be difficult to promote the large-scale application of the lithium-sulfur battery.

Disclosure of Invention

The invention aims to provide a lithium-sulfur battery diaphragm and a preparation method and application thereof.

The technical scheme adopted by the invention is as follows:

a lithium-sulfur battery diaphragm is composed of a laminated interlayer and a diaphragm, wherein the interlayer is a reticular film formed by carbon nano fibers, and the diaphragm is a reticular film formed by non-conductive polymer nano fibers.

Preferably, the barrier layer further comprises nano titanium dioxide particles.

Preferably, the separator further comprises nano silica particles.

Preferably, the non-conductive polymer is at least one of polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate and polyvinylpyrrolidone.

Further preferably, the non-conductive polymer is polyacrylonitrile.

Preferably, the thickness of the interlayer is 2 to 2000 μm.

Preferably, the thickness of the separator is 2 μm to 2000 μm.

The preparation method of the lithium-sulfur battery diaphragm comprises the following steps:

1) dispersing organic polymer and nano titanium dioxide particles in a solvent to prepare a spinning solution I, carrying out primary electrostatic spinning to form a reticular membrane consisting of nano fibers, and carrying out heat treatment to obtain an interlayer;

2) and dispersing the non-conductive polymer and the nano silicon dioxide particles in a solvent to prepare a spinning solution II, and performing secondary electrostatic spinning on the interlayer to form a reticular membrane consisting of nano fibers, thus obtaining the lithium-sulfur battery diaphragm.

Preferably, the mass ratio of the organic polymer to the nano titanium dioxide particles in the step 1) is 1: 0.01-1: 1.

Further preferably, the mass ratio of the organic polymer to the nano titanium dioxide particles in the step 1) is 1: 0.3-1: 0.7.

Preferably, the particle size of the nano titanium dioxide particles in the step 1) is 10 nm-100 nm.

Preferably, the organic polymer in step 1) is at least one of polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate and polyvinylpyrrolidone.

Further preferably, the organic polymer in step 1) is polyacrylonitrile.

Preferably, the solvent in step 1) is at least one of N, N-dimethylformamide, water, alcohol and acetone.

Preferably, the electrostatic spinning parameters in the step 1) are that the inner diameter of the syringe needle is 0.1-1 mm, the voltage between the syringe needle and the receiver is 10 kV-20 kV, the distance is 10 cm-20 cm, and the outflow speed of the spinning solution is 0.1-1 mL/h.

Preferably, the specific operation of the heat treatment in step 1) is as follows: the reticular membrane composed of the nano-fibers is firstly placed in a muffle furnace, the temperature is raised to 220-280 ℃ at the heating rate of 1-5 ℃/min, the temperature is preserved for 1-3 h, the reticular membrane is cooled to the room temperature along with the furnace, then the reticular membrane is placed in a tubular furnace, protective gas is filled, the temperature is raised to 600-1200 ℃ at the heating rate of 1-5 ℃/min, the temperature is preserved for 1-3 h, and the reticular membrane is cooled to the room temperature along with the furnace.

Preferably, the mass ratio of the non-conductive polymer and the nano silicon dioxide particles in the step 2) is 1: 0.01-1: 1.

Further preferably, the mass ratio of the non-conductive polymer and the nano silicon dioxide particles in the step 2) is 1: 0.3-1: 0.7.

Preferably, the particle size of the nano silicon dioxide particles in the step 2) is 10 nm-100 nm.

Preferably, the solvent in step 2) is at least one of N, N-dimethylformamide, water, alcohol and acetone.

Preferably, the electrostatic spinning parameters in the step 2) are that the inner diameter of the syringe needle is 0.1-1 mm, the voltage between the syringe needle and the receiver is 10 kV-20 kV, the distance is 10 cm-20 cm, and the outflow speed of the spinning solution is 0.1-1 mL/h.

The invention has the beneficial effects that: the lithium-sulfur battery diaphragm disclosed by the invention realizes the integration of the interlayer and the diaphragm, the interlayer and the diaphragm are both net-shaped membranes formed by nano fibers and have flexibility, the interlayer has good conductivity and rich pore structures, the diaphragm has excellent chemical stability, electrolyte wettability, mechanical property and thermal stability and high porosity, and the interlayer and the diaphragm have synergistic effect, so that the performance of the lithium-sulfur battery is favorably improved.

Specifically, the method comprises the following steps:

1) the lithium-sulfur battery diaphragm disclosed by the invention realizes the integration of the interlayer and the diaphragm, can realize the one-time assembly of the interlayer and the diaphragm, reduces the assembly difficulty and the assembly cost of the lithium-sulfur battery, and reduces the negative influence caused by the assembly problem;

2) according to the invention, the interlayer and the diaphragm are prepared by an electrostatic spinning process, and the modification of the interlayer and the diaphragm can be realized by respectively adding different nano oxide functional particles, compared with the modification by adding metal organic salt, the direct addition of the nano oxide functional particles can enable the nano oxide functional particles to be more easily exposed on the surface of the nanofiber, so that polysulfide can be more easily contacted and adsorbed, and the addition of the nano oxide functional particles can also improve the mechanical properties of the interlayer and the diaphragm;

3) the lithium-sulfur battery diaphragm disclosed by the invention is simple in preparation process, low in preparation cost and convenient for realizing large-scale production and application.

Drawings

Fig. 1 is a schematic structural view of a lithium sulfur battery separator according to the present invention.

Fig. 2 is a photograph of a lithium sulfur battery separator of example 2.

Fig. 3 is an SEM image of the lithium sulfur battery separator of example 2.

Fig. 4 is a graph showing electrochemical cycle performance test results of a lithium sulfur battery assembled with the lithium sulfur battery separator of example 1, the lithium sulfur battery separator of example 2, and a polypropylene separator.

The attached drawings indicate the following: 10. an interlayer; 20. a diaphragm.

Detailed Description

The invention will be further explained and illustrated with reference to specific examples.

Example 1:

a lithium-sulfur battery diaphragm (the structural schematic diagram is shown in figure 1) is composed of a laminated interlayer 10 and a diaphragm 20, wherein the interlayer 10 is a reticular membrane formed by carbon nanofibers, and the diaphragm 20 is a reticular membrane formed by polyacrylonitrile nanofibers.

The preparation method of the lithium-sulfur battery diaphragm comprises the following steps:

1) adding 0.8g of polyacrylonitrile into 8mL of N, N-dimethylformamide, placing the mixture in a water bath at 60 ℃ and stirring for 12 hours to obtain a spinning solution I, carrying out first electrostatic spinning on an aluminum foil to form a reticular membrane consisting of polyacrylonitrile nanofibers, wherein the parameters of the electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the aluminum foil is 16kV and the distance is 14cm, the outflow speed of the spinning solution I is 0.8mL/h, peeling the reticular membrane from the aluminum foil, placing the stripped reticular membrane in a drying oven, drying at 50 ℃ for 12 hours, placing the stripped reticular membrane in a muffle furnace, heating to 230 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 3 hours, cooling to room temperature with the furnace, placing the stripped reticular membrane in a tubular furnace, filling argon, heating to 700 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 1 hour, and cooling to room temperature with the furnace to obtain an interlayer;

2) adding 0.8g of polyacrylonitrile into 8mL of N, N-dimethylformamide, placing the mixture in a water bath at 60 ℃ for stirring for 12 hours to obtain a spinning solution II, carrying out secondary electrostatic spinning on an interlayer to form a reticular membrane consisting of polyacrylonitrile nanofibers, wherein the parameters of the electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the interlayer is 16kV, the distance is 14cm, the outflow speed of the spinning solution II is 0.8mL/h, then placing the membrane in a drying oven, and drying the membrane for 24 hours at 50 ℃ to form a membrane, thus obtaining the lithium-sulfur battery membrane.

Assembling the lithium-sulfur battery:

mixing sulfur and conductive carbon black according to a mass ratio of 7:3 to obtain an active material, mixing the active material, the multi-walled carbon nanotube and polyvinylidene fluoride according to a mass ratio of 7:2:1, coating the mixture to prepare a positive plate, and adding lithiumThe sheet was a negative electrode sheet, the lithium-sulfur battery separator prepared in example 1 was a separator, and a 1mol/L solution of lithium bistrifluoromethanesulfonylimide (LiTFSI) in which the solvent was composed of ethylene glycol dimethyl ether and 1, 3-dioxolane in a volume ratio of 1:1 and 1 wt% LiNO was added to the solution₃) And assembling the lithium-sulfur battery for electrolyte, wherein the interlayer surface of the lithium-sulfur battery diaphragm faces to the positive plate, and the diaphragm surface faces to the negative plate.

Example 2:

a lithium-sulfur battery diaphragm (the structural schematic diagram is shown in figure 1) is composed of a laminated interlayer 10 and a diaphragm 20, wherein the interlayer 10 is a reticular membrane formed by carbon nanofibers, the interlayer 10 further comprises nano titanium dioxide particles, and the diaphragm 20 is a reticular membrane formed by polyacrylonitrile nanofibers.

The preparation method of the lithium-sulfur battery diaphragm comprises the following steps:

1) adding 0.4g of nano titanium dioxide particles with the particle size of 100nm into 8mL of N, N-dimethylformamide, carrying out ultrasonic treatment for 30min, adding 0.8g of polyacrylonitrile, placing the mixture in a water bath at 60 ℃ and stirring for 12h to obtain a spinning solution I, carrying out first electrostatic spinning on an aluminum foil to form a reticular membrane consisting of polyacrylonitrile nano fibers, wherein the parameters of the electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the aluminum foil is 16kV and the distance is 14cm, the outflow speed of the spinning solution I is 0.8mL/h, stripping the reticular membrane from the aluminum foil, placing the stripped reticular membrane in a drying oven, drying the reticular membrane for 12h at 50 ℃, placing the reticular membrane in a muffle furnace, heating to 230 ℃ at the heating rate of 2 ℃/min, carrying out heat preservation for 3h, cooling the reticular membrane to room temperature along with the furnace, placing the tubular furnace again, filling argon, heating to 700 ℃ at the heating rate of 2 ℃/min, carrying out heat preservation for 1h, cooling to room temperature along with the furnace to obtain an interlayer;

2) adding 0.8g of polyacrylonitrile into 8mL of N, N-dimethylformamide, placing the mixture in a water bath at 60 ℃ for stirring for 12 hours to obtain a spinning solution II, carrying out secondary electrostatic spinning on an interlayer to form a reticular membrane consisting of polyacrylonitrile nanofibers, wherein the parameters of the electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the interlayer is 16kV, the distance is 14cm, the outflow speed of the spinning solution II is 0.8mL/h, then placing the membrane in a drying oven, and drying the membrane for 24 hours at 50 ℃ to form a membrane, thus obtaining the lithium-sulfur battery membrane.

A lithium sulfur battery was assembled according to the method of example 1.

A real photograph and a Scanning Electron Microscope (SEM) image of the lithium sulfur battery separator prepared in example 2 are shown in fig. 2 and 3, respectively.

As can be seen from fig. 2: the lithium-sulfur battery diaphragm is successfully prepared, the interlayer is laminated with the diaphragm, the binding property is good, and the assembly is easy.

As can be seen from fig. 3: the interlayer and the diaphragm are both provided with a nanofiber net structure, the porosity is high, and the nanofiber structure of the interlayer is also loaded with a plurality of nano titanium dioxide particles, so that polysulfide can be adsorbed conveniently, and the performance of the lithium-sulfur battery can be improved.

The results of electrochemical cycle performance tests of the lithium sulfur battery assembled with the lithium sulfur battery separator prepared in example 1, the lithium sulfur battery separator prepared in example 2, and the polypropylene separator are shown in fig. 4.

As can be seen from fig. 4: at a charge-discharge rate of 0.2C, the lithium-sulfur battery in example 1 has better performance than a lithium-sulfur battery using a polypropylene separator because the separator and the separator have the advantages of high porosity and the like, and the carbon nanofiber separator has a physical barrier effect on polysulfide. In addition, the performance of the lithium sulfur battery in example 2 is superior to that of the lithium sulfur battery in example 1 due to the effect of the chemisorption of the nano titanium dioxide particles supported on the carbon nanofiber structure to polysulfides.

Example 3:

a lithium-sulfur battery diaphragm (the structural schematic diagram is shown in figure 1) is composed of a laminated interlayer 10 and a diaphragm 20, wherein the interlayer 10 is a reticular membrane formed by carbon nanofibers, the diaphragm 20 is a reticular membrane formed by polyacrylonitrile nanofibers, and the diaphragm 20 further comprises nano silica particles.

The preparation method of the lithium-sulfur battery diaphragm comprises the following steps:

1) adding 0.8g of polyacrylonitrile into 8mL of N, N-dimethylformamide, placing the mixture in a water bath at 60 ℃ and stirring for 12 hours to obtain a spinning solution I, carrying out first electrostatic spinning on an aluminum foil to form a reticular membrane consisting of polyacrylonitrile nanofibers, wherein the parameters of the electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the aluminum foil is 16kV and the distance is 14cm, the outflow speed of the spinning solution I is 0.8mL/h, peeling the reticular membrane from the aluminum foil, placing the stripped reticular membrane in a drying oven, drying at 50 ℃ for 12 hours, placing the stripped reticular membrane in a muffle furnace, heating to 230 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 3 hours, cooling to room temperature with the furnace, placing the stripped reticular membrane in a tubular furnace, filling argon, heating to 700 ℃ at the heating rate of 2 ℃/min, keeping the temperature for 1 hour, and cooling to room temperature with the furnace to obtain an interlayer;

2) adding 0.4g of nano silica particles with the particle size of 30nm into 8mL of N, N-dimethylformamide, carrying out ultrasonic treatment for 30min, adding 0.8g of polyacrylonitrile, placing the mixture in a water bath at 60 ℃ and stirring for 12h to obtain a spinning solution II, carrying out secondary electrostatic spinning on an interlayer to form a reticular membrane consisting of polyacrylonitrile nanofibers, wherein the parameters of electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the interlayer is 16kV, the distance is 14cm, the outflow speed of the spinning solution II is 0.8mL/h, placing the obtained product in a drying box, and drying for 24h at 50 ℃ to form a membrane, thus obtaining the lithium-sulfur battery membrane.

A lithium sulfur battery was assembled according to the method of example 1.

The performance of the assembled lithium sulfur battery of example 3 was tested to be superior to that of the assembled lithium sulfur battery of example 1.

Example 4:

a lithium-sulfur battery diaphragm (the structural schematic diagram is shown in figure 1) is composed of a laminated interlayer 10 and a diaphragm 20, wherein the interlayer 10 is a net-shaped film formed by carbon nanofibers, the interlayer 10 further comprises nano titanium dioxide particles, the diaphragm 20 is a net-shaped film formed by polyacrylonitrile nanofibers, and the diaphragm 20 further comprises nano silicon dioxide particles.

The preparation method of the lithium-sulfur battery diaphragm comprises the following steps:

1) adding 0.4g of nano titanium dioxide particles with the particle size of 100nm into 8mL of N, N-dimethylformamide, carrying out ultrasonic treatment for 30min, adding 0.8g of polyacrylonitrile, placing the mixture in a water bath at 60 ℃ and stirring for 12h to obtain a spinning solution I, carrying out first electrostatic spinning on an aluminum foil to form a reticular membrane consisting of polyacrylonitrile nano fibers, wherein the parameters of the electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the aluminum foil is 16kV and the distance is 14cm, the outflow speed of the spinning solution I is 0.8mL/h, stripping the reticular membrane from the aluminum foil, placing the stripped reticular membrane in a drying oven, drying the reticular membrane for 12h at 50 ℃, placing the reticular membrane in a muffle furnace, heating to 230 ℃ at the heating rate of 2 ℃/min, carrying out heat preservation for 3h, cooling the reticular membrane to room temperature along with the furnace, placing the tubular furnace again, filling argon, heating to 700 ℃ at the heating rate of 2 ℃/min, carrying out heat preservation for 1h, cooling to room temperature along with the furnace to obtain an interlayer;

2) adding 0.4g of nano silica particles with the particle size of 30nm into 8mL of N, N-dimethylformamide, carrying out ultrasonic treatment for 30min, adding 0.8g of polyacrylonitrile, placing the mixture in a water bath at 60 ℃ and stirring for 12h to obtain a spinning solution II, carrying out secondary electrostatic spinning on an interlayer to form a reticular membrane consisting of polyacrylonitrile nanofibers, wherein the parameters of electrostatic spinning are that the inner diameter of a syringe needle is 0.5mm, the voltage between the syringe needle and the interlayer is 16kV, the distance is 14cm, the outflow speed of the spinning solution II is 0.8mL/h, placing the obtained product in a drying box, and drying for 24h at 50 ℃ to form a membrane, thus obtaining the lithium-sulfur battery membrane.

A lithium sulfur battery was assembled according to the method of example 1.

The performance of the assembled lithium sulfur battery of example 4 was tested to be superior to that of the assembled lithium sulfur battery of example 1.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.