阅读说明：本技术 一种基于纳米金属氢氧化物-碳复合材料的锂硫电池用改性隔膜的制备方法 (Preparation method of modified diaphragm for lithium-sulfur battery based on nano metal hydroxide-carbon composite material ) 是由 侯士峰 胡成 赵长锋 于 2020-09-25 设计创作，主要内容包括：本发明涉及一种基于纳米金属氢氧化物-碳复合材料的锂硫电池用改性隔膜的制备方法,本发明将纳米金属氢氧化物或纳米金属氢氧化物与碳基体复合材料作为多硫化锂的阻隔层,在传统隔膜上形成锂硫电池改性隔膜,对于正极产生的多硫化锂具有阻挡、吸附的作用。纳米金属氢氧化物或纳米金属氢氧化物与碳基体复合材料具有高的比表面积,它可以有效吸附可溶性多硫化物,抑制多硫化物向负极扩散,同时其表面含有大量亲水的表面羟基化合物与聚硫阴离子具有良好的物理化学稳定性,能有效地抑制多硫化物的溶解和泄漏。(The invention relates to a preparation method of a modified diaphragm for a lithium-sulfur battery based on a nano metal hydroxide-carbon composite material. The nano metal hydroxide or the nano metal hydroxide and carbon matrix composite has high specific surface area, can effectively adsorb soluble polysulfide and inhibit the polysulfide from diffusing to a negative electrode, and simultaneously, the surface of the nano metal hydroxide or the nano metal hydroxide and carbon matrix composite contains a large amount of hydrophilic surface hydroxyl compounds and polysulfide anions, has good physical and chemical stability and can effectively inhibit the dissolution and leakage of the polysulfide.)

1. A preparation method of a modified diaphragm for a lithium-sulfur battery based on a nano metal hydroxide-carbon composite material comprises a diaphragm body, wherein one side or two sides of the diaphragm body are coated with a modified coating, and the modified coating comprises the nano metal hydroxide or the composite material formed by the nano metal hydroxide and the carbon matrix, a conductive agent and a binder;

the preparation method comprises the following steps:

(1) adding nano metal hydroxide or nano metal hydroxide and carbon matrix composite, conductive agent and adhesive into a solvent, and then performing ball milling, grinding, stirring and the like to obtain uniform diaphragm modified slurry;

(2) and (2) uniformly coating the diaphragm modified slurry obtained in the step (1) on the surface of one side or two sides of the diaphragm body and drying to obtain the nano metal hydroxide modified lithium-sulfur battery diaphragm.

2. The method for preparing the nano metal hydroxide-carbon composite-based modified separator for a lithium sulfur battery according to claim 1, wherein in the step (1), the nano metal hydroxide is prepared by the following steps:

(1.1) mixing one or more of a nickel source, a cobalt source, a manganese source, a copper source, a zinc source or an iron source, dissolving the mixture in deionized water, adding an alkaline material, and stirring uniformly to obtain a reaction solution;

(1.2) standing the reaction solution at normal temperature or reacting under a hydrothermal condition to obtain a composite product, collecting a precipitate of the composite product, washing the precipitate with deionized water, and drying to obtain nano metal hydroxide powder;

the nano metal hydroxide and carbon matrix composite material is prepared by the following steps:

(2.1) dissolving one or more of a nickel source, a cobalt source, a manganese source, a copper source, a zinc source or an iron source in water, adding a solution, a suspension or an emulsion of an alkaline material and a carbon matrix, stirring uniformly to obtain a reaction solution,

(2.2) standing the reaction solution at normal temperature or reacting under a hydrothermal condition to obtain a reaction product, collecting the precipitate of the reaction product, washing the precipitate with deionized water, and drying to obtain nano metal hydroxide and carbon matrix composite powder;

preferably, in step (1.1) and step (2.1), the nickel source, cobalt source, manganese source, copper source, zinc source or iron source is oxalate, chloride, bromide, sulfate, nitrate or acetate of the nickel source, cobalt source, manganese source, copper source, zinc source or iron source.

3. The method for preparing the modified separator for the lithium-sulfur battery based on the nano metal hydroxide-carbon composite material according to claim 2, wherein in the step (1.1) and the step (2.1), the alkaline material is one or more of urea, urotropine and a sodium hydroxide solution with a concentration of 0.01-1%.

4. The method for preparing the modified separator for the lithium-sulfur battery based on the nano metal hydroxide-carbon composite material according to claim 2, wherein in the step (1.1), the mass ratio of the alkaline material to one or more of the nickel source, the cobalt source, the manganese source, the copper source and the iron source is as follows: (0.5-3): 1.

5. the method for preparing the modified separator for the lithium sulfur battery based on the nano metal hydroxide-carbon composite material according to claim 2, wherein in the step (1.2), the hydrothermal temperature is 60-80 ℃ until no new precipitate appears; in the step (1.2) and the step (2.2), the drying method is one of forced air drying, vacuum drying, freeze drying or supercritical drying.

6. The method for preparing a modified separator for a lithium-sulfur battery based on a nano-metal hydroxide-carbon composite according to claim 2, wherein in the step (2.1), the carbon substrate is selected from one of graphene, graphene oxide, carbon nanotubes, carbon fibers, carbon nanofibers, carbon nanobelts, carbon black, activated carbon, mesoporous carbon, porous carbon, or a non-carbon atom-doped product of the above carbon materials.

7. The method for preparing the modified separator for the lithium-sulfur battery based on the nano metal hydroxide-carbon composite material according to claim 2, wherein in the step (2.1), the mass ratio of the alkaline material to one or more of the nickel source, the cobalt source, the manganese source, the copper source and the iron source is: (0.5-3): 1; the concentration of the carbon matrix in the solution, the suspension or the emulsion of the carbon matrix is 1-65mg/mL, and the volume ratio of the added amount of the solution, the suspension or the emulsion of the carbon matrix to the deionized water is as follows: 1: (4-6); in the step (2.2), the hydrothermal condition temperature is 60-80 ℃, and the reaction is carried out until no new precipitate appears.

8. The method for preparing a modified separator for a lithium sulfur battery based on a nano metal hydroxide-carbon composite material according to claim 1, wherein the thickness of the modified coating layer is 1 to 30 μm; the conductive agent is one or more of conductive carbon black, carbon fiber, acetylene black, crystalline flake graphite, carbon nano tube, graphene, polypyrrole, polyaniline, polyacetylene and nano silver wire; in the modified coating, the mass ratio of the nano metal hydroxide or the nano metal hydroxide to the carbon matrix composite, the conductive agent and the adhesive is (3-9): (1-6): (0.2-1.5).

9. The preparation method of the modified diaphragm for the lithium-sulfur battery based on the nano metal hydroxide-carbon composite material as claimed in claim 1, wherein the diaphragm body is any one of a polyethylene diaphragm, a polypropylene diaphragm, a polyethylene/polypropylene double-layer diaphragm, a polyethylene/polypropylene/polyethylene three-layer diaphragm, a polyimide diaphragm, a glass ceramic diaphragm, a polyamide diaphragm or polyacrylonitrile; the binder is one or more of epoxy resin, polyethylene oxide, polyacrylic acid, polyvinylidene fluoride, sodium carboxymethylcellulose and styrene butadiene rubber.

10. The method for preparing the modified membrane for the lithium-sulfur battery based on the nano metal hydroxide-carbon composite material according to claim 1, wherein the solvent in the step (1) is nitrogen-methyl pyrrolidone or deionized water, and the addition amount of the solvent is 20-80 wt% of the weight of the modified slurry of the membrane; the coating mode is a coating, suction filtration or spraying mode.

Technical Field

The invention relates to a preparation method of a modified diaphragm for a lithium-sulfur battery based on a nano metal hydroxide-carbon composite material, belonging to the technical field of battery diaphragms.

Background

The lithium-sulfur battery takes the elemental sulfur and the metallic lithium as the positive and negative active materials of the battery, the theoretical specific capacity is large (1675mAh/g), and the lithium-sulfur battery has the advantages of light weight, large capacity, environmental friendliness, easily obtained raw materials and the like. The lithium-sulfur battery is a secondary battery with great application prospect.

Despite the great advantage of high energy density, lithium sulfur batteries also have some problems to be solved, most notably the shuttling effect of soluble polysulfides. Ether electrolyte commonly used in lithium-sulfur battery at present is applied to charge-discharge intermediate product polysulfide ion Li₂S_x(x ═ 4-8) has strong solubility, so that the charging and discharging process of the lithium-sulfur battery is represented by a complex solid-liquid-solid process. This process is accompanied by dissociation and reconstruction of the positive electrode structure, making the electrode less stable. Meanwhile, when the lithium-sulfur battery is charged, long-chain polysulfide ions generated by the positive electrode are driven by the concentration gradient to migrate to the negative electrode to react with metal lithium to generate short-chain polysulfide ions, and the short-chain polysulfide ions migrate back to the positive electrode under the action of an electric field and are further oxidized, and the process is continuously and circularly repeated to form a shuttle effect. The shuttle effect not only reduces the coulombic efficiency of the battery, but also causes the problems of corrosion of a metal lithium cathode, increase of the viscosity of the electrolyte and the like, so that the performance of the battery is deteriorated.

In order to solve the above problems, attention has been paid to the use of polysulfide ion barrier layers based on carbon materials. Since 2012 scientific researchers reported that after microporous carbon paper was used as an intermediate layer of a lithium sulfur battery, biomass thin films, porous carbon and the like were also used as carbon-based barrier layers to block shuttling of polysulfides. The insertion of the intermediate layer between the sulfur positive electrode and the separator can significantly improve the utilization of active materials and the capacity retention, and is an effective way to improve the performance of lithium-sulfur batteries. However, the intermediate layer which is structurally independent has the disadvantage of relatively large volume and mass, and the problem can be effectively solved by compounding the carbon material with the membrane to form the modified membrane.

In addition to the above-mentioned carbon material intermediate layer, researchers have also made studies and attempts on the suppression of the "shuttle effect" of materials such as conductive polymer materials with slightly strong polarity, Metal Organic Framework (MOF) materials with micropores, metal oxides, oxide ceramics, etc. on polysulfides, and have obtained a good effect. The materials inhibit the diffusion of polysulfide mainly through adsorption or blocking, and the battery capacity is improved to a certain extent. The ability of such materials to regulate polysulfide conversion and deposition is still limited, especially under the high sulfur-loading test condition, and it is also necessary to promote polysulfide electrochemical conversion while adsorbing and limiting the domain, so as to further improve the performance of the battery.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of a modified diaphragm for a lithium-sulfur battery based on a nano metal hydroxide-carbon composite material. Compared with the carbon material intermediate layer, the preparation method of the modified diaphragm for the lithium-sulfur battery is simple, has low cost, can continue to use the existing processes of slurry mixing, coating, baking and the like of the existing lithium battery, and is suitable for industrial production. The modified diaphragm can effectively prevent the shuttle of polysulfide, nano metal hydroxide and carbon have obvious adsorption effect on polysulfide, wherein the nano metal hydroxide can reduce Gibbs free energy in the chemical reaction process, and has obvious catalytic action.

The invention is realized by the following technical scheme:

a preparation method of a modified diaphragm for a lithium-sulfur battery based on a nano metal hydroxide-carbon composite material comprises a diaphragm body, wherein one side or two sides of the diaphragm body are coated with a modified coating, and the modified coating comprises the nano metal hydroxide or the composite material formed by the nano metal hydroxide and the carbon matrix, a conductive agent and a binder;

the preparation method comprises the following steps:

(1) adding nano metal hydroxide or nano metal hydroxide and carbon matrix composite, conductive agent and adhesive into a solvent, and then performing ball milling, grinding, stirring and the like to obtain uniform diaphragm modified slurry;

(2) and (2) uniformly coating the diaphragm modified slurry obtained in the step (1) on the surface of one side or two sides of the diaphragm body and drying to obtain the nano metal hydroxide modified lithium-sulfur battery diaphragm.

In the step (1), the nano metal hydroxide is prepared by the following steps:

(1.1) mixing one or more of a nickel source, a cobalt source, a manganese source, a copper source, a zinc source or an iron source, dissolving the mixture in deionized water, adding an alkaline material, and stirring uniformly to obtain a reaction solution;

and (1.2) standing the reaction solution at normal temperature or reacting under a hydrothermal condition to obtain a composite product, collecting the precipitate of the composite product, washing the precipitate with deionized water, and drying to obtain the nano metal hydroxide powder.

In the step (1), the nano metal hydroxide and carbon matrix composite material is prepared by the following steps:

(2.1) dissolving one or more of a nickel source, a cobalt source, a manganese source, a copper source, a zinc source or an iron source in water, adding a solution, a suspension or an emulsion of an alkaline material and a carbon matrix, stirring uniformly to obtain a reaction solution,

and (2.2) standing the reaction solution at normal temperature or reacting under a hydrothermal condition to obtain a reaction product, collecting a precipitate of the reaction product, washing the precipitate with deionized water, and drying to obtain the nano metal hydroxide and carbon matrix composite powder.

Preferably, in step (1.1) and step (2.1), the nickel source, cobalt source, manganese source, copper source, zinc source or iron source is oxalate, chloride, bromide, sulfate, nitrate or acetate of the nickel source, cobalt source, manganese source, copper source, zinc source or iron source.

According to the invention, in the step (1.1) and the step (2.1), the alkaline material is one or more of urea, urotropine and a sodium hydroxide solution with the concentration of 0.01-1%.

According to the invention, in the step (1.1), the mass ratio of the mixture of one or more of the nickel source, the cobalt source, the manganese source, the copper source or the iron source to the alkaline material is as follows: (0.5-3): 1.

according to the invention, in step (1.2), the hydrothermal conditions are preferably at a temperature of 60 ℃ to 80 ℃ until no new precipitate is formed.

According to the invention, in the step (1.2) and the step (2.2), the drying method is one of air-blast drying, vacuum drying, freeze drying or supercritical drying.

Preferably, in step (2.1), the carbon substrate is selected from one of graphene, graphene oxide, carbon nanotubes, carbon fibers, carbon nanofibers, carbon nanobelts, carbon black, activated carbon, mesoporous carbon, porous carbon, or a product obtained by doping the above carbon materials with non-carbon atoms.

The product of carbon material after non-carbon atom doping is prior art.

According to the invention, in the step (2.1), the mass ratio of the mixture of one or more of the nickel source, the cobalt source, the manganese source, the copper source or the iron source to the alkaline material is as follows: (0.5-3): 1.

preferably, in step (2.1), the concentration of the carbon matrix in the solution, suspension or emulsion of the carbon matrix is 1-65mg/mL, and the volume ratio of the added amount of the solution, suspension or emulsion of the carbon matrix to the deionized water is: 1: (4-6).

According to the invention, in step (2.2), the hydrothermal conditions are preferably at a temperature of 60 ℃ to 80 ℃ until no new precipitate is formed.

Preferably, according to the invention, the modified coating has a thickness of 1 to 30 μm; the conductive agent is one or more of conductive carbon black, carbon fiber, acetylene black, crystalline flake graphite, carbon nano tube, graphene, polypyrrole, polyaniline, polyacetylene and nano silver wire.

According to the invention, in the modified coating, the mass ratio of the nano metal hydroxide or the nano metal hydroxide to the carbon matrix composite, the conductive agent and the binder is (3-9): (1-6): (0.2-1.5).

According to the invention, the diaphragm body is preferably any one of a polyethylene diaphragm, a polypropylene diaphragm, a polyethylene/polypropylene double-layer diaphragm, a polyethylene/polypropylene/polyethylene three-layer diaphragm, a polyimide diaphragm, a glass ceramic diaphragm, a polyamide diaphragm or polyacrylonitrile. The thickness of the separator body is not limited, and preferably, the separator substrate and the coating layer can be effectively bonded, so that the stability of the lithium-sulfur battery is improved, and the polarization of the lithium-sulfur battery is effectively reduced.

According to the invention, the binder is preferably one or a mixture of more than two of epoxy resin, polyethylene oxide, polyacrylic acid, polyvinylidene fluoride, sodium carboxymethylcellulose and styrene butadiene rubber.

According to the invention, the solvent in the step (1) is nitrogen-methyl pyrrolidone or deionized water, and the addition amount of the solvent accounts for 20-80 wt% of the weight of the diaphragm modified slurry.

According to the invention, the coating mode in the step (1) is preferably a coating, suction filtration or spraying mode.

The invention has the following advantages and positive effects:

1. the invention takes the nano metal hydroxide or the nano metal hydroxide and carbon matrix composite material as the barrier layer of lithium polysulfide, forms the modified diaphragm of the lithium-sulfur battery on the traditional diaphragm, and has the functions of blocking and adsorbing the lithium polysulfide generated by the anode. The nano metal hydroxide or the nano metal hydroxide and carbon matrix composite has high specific surface area, can effectively adsorb soluble polysulfide and inhibit the polysulfide from diffusing to a negative electrode, and simultaneously, the surface of the nano metal hydroxide or the nano metal hydroxide and carbon matrix composite contains a large amount of hydrophilic surface hydroxyl compounds and polysulfide anions, has good physical and chemical stability and can effectively inhibit the dissolution and leakage of the polysulfide.

2. According to the invention, the nano metal hydroxide or the nano metal hydroxide and carbon matrix composite material is applied to the lithium-sulfur battery modified diaphragm, the inherent micropores or mesopores on the surface of the mixture formed by the metal hydroxide and lithium are convenient for the shuttling of lithium ions, and the metal ions can play a certain catalytic role in the electrochemical reaction of the lithium-sulfur battery, so that the electrochemical activity of the lithium-sulfur battery is improved.

3. According to the invention, the nano metal hydroxide or the nano metal hydroxide and carbon matrix composite material is applied to the modified diaphragm of the lithium-sulfur battery, and the conductive agent is added into the modified diaphragm, so that the electrochemical catalytic conversion of polysulfide ions is promoted, the sulfur utilization rate of the anode is improved, and the cycle stability of the lithium-sulfur battery is improved.

4. The preparation method of the nano metal hydroxide or the nano metal hydroxide and carbon matrix composite material is prepared by adopting a one-step hydrothermal method, does not need inert gas, does not need high temperature and high pressure, does not need other reagents, has simple process, low cost, low energy consumption and lower reaction temperature, is suitable for large-scale industrial production, is in a nano level, has the material thickness of a membrane modification layer smaller than 100nm, has controllable morphology, and has volume and mass ratio obviously lower than that of an independent lithium-sulfur battery middle layer.

Drawings

FIG. 1 is an SEM photograph of nickel hydroxide prepared in example 1;

FIG. 2 is an SEM partial view of nickel hydroxide prepared in example 1;

FIG. 3 is a TEM image of the nano nickel hydroxide-graphene composite powder in example 2;

FIG. 4 is an SEM image of the nano nickel hydroxide/manganese hydroxide composite powder in example 3;

FIG. 5 is a TEM image of copper hydroxide powder in example 4;

FIG. 6 is a graph of charge and discharge curves for different separator batteries;

FIG. 7 is a graph comparing the rate discharge of different membrane batteries;

fig. 8 is a graph comparing the cycle discharge of different membrane batteries.

The specific implementation mode is as follows:

the invention is explained in more detail below with reference to the figures and examples.

The raw materials in the examples are all commercial products.

Example 1

A preparation method of a lithium-sulfur battery diaphragm modified by nanometer metal hydroxide comprises the following steps that the lithium-sulfur battery diaphragm comprises a diaphragm body, one side of the diaphragm body is coated with a modified coating, and the modified coating comprises nickel hydroxide powder, a conductive agent SP and a binder PVDF; the mass ratio of the nickel hydroxide powder, the conductive agent SP and the adhesive PVDF is 8:1: 1;

the preparation method comprises the following steps:

(1) weighing 0.24g of sodium hydroxide, dissolving the sodium hydroxide in 500mL of deionized water, wherein the concentration is 0.012mol/L, weighing 0.548g of nickel nitrate, putting the nickel nitrate into a beaker filled with 100mL of deionized water, stirring until the nickel nitrate is completely dissolved, gradually dripping the 0.012mol/L sodium hydroxide solution into the slowly stirred nickel nitrate solution, reacting to finally generate light green precipitate, collecting the precipitate, washing the deionized water for several times, and drying at 60 ℃ to obtain nano nickel hydroxide powder;

(2) adding the nano nickel hydroxide powder, the conductive agent SP and the adhesive PVDF into N-methyl pyrrolidone, and then performing ball milling to obtain modified slurry;

(3) and (3) uniformly coating the modified slurry on the surface of one side of the polyethylene diaphragm body, and baking for 12 hours at the temperature of 60 ℃ to obtain the nano metal hydroxide modified lithium-sulfur battery diaphragm. Cut into sheets with a diameter of 17mm and then used as separators of button cells.

Fig. 1 and fig. 2 are scanning electron micrographs of the nano nickel hydroxide powder prepared in this example 1, respectively, and it can be clearly seen from fig. 2 that the nano nickel hydroxide is in the form of flower-like flakes, and the flake thickness is less than 100 nm.

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

1) mixing the carbon nano tube and the sublimed sulfur according to a certain mass ratio, uniformly mixing the mixture for a main material of a positive electrode material, preparing the main material, SP and PVDF binder into slurry (preferably 8:1:1) according to a certain mass ratio, coating the slurry on an aluminum foil, drying and rolling the aluminum foil, and cutting the aluminum foil into pole pieces with the diameter of 12 mm;

2) the electrochemical performance of the CR2025 button cell is tested after the CR2025 button cell is assembled in a glove box according to the sequence of a sulfur positive electrode, a diaphragm and metallic lithium, the assembled button cell is charged and discharged for 5 times respectively at 0.2C, 0.5C, 1C, 0.5C and 0.2C, and the 0.2C specific discharge capacity of the cell is about 740mAh g after the rate test^-1The capacity after 100 cycles at a charge-discharge rate of 0.2C was 606mAh g^-1Left and right. Specific data refer to fig. 6, 7 and 8.

Example 2

A preparation method of a lithium-sulfur battery diaphragm modified by nanometer metal hydroxide comprises a diaphragm body, wherein one side of the diaphragm body is coated with a modified coating, and the modified coating comprises nanometer nickel hydroxide-graphene composite powder, a conductive agent SP and an adhesive PVDF; the mass ratio of the nano nickel hydroxide-graphene composite powder to the conductive agent SP to the adhesive PVDF is 8:1: 1;

the preparation method comprises the following steps:

(1) weighing 8mL of graphene oxide solution with solid content of 5mg/mL, weighing 1.6g of nickel sulfate hexahydrate and 0.72g of urotropine, putting the materials into a beaker filled with 40mL of deionized water, uniformly stirring, transferring the aqueous solution into a reaction kettle, sealing, preserving heat at 95 ℃ for 6 hours to generate black precipitates, collecting the precipitates, washing the precipitates with deionized water for several times, and freeze-drying to obtain nano nickel hydroxide-graphene composite powder; fig. 3 is a transmission electron microscope image of the nano nickel hydroxide-graphene composite powder prepared in this embodiment, and it can be clearly seen from fig. 3 that the nano nickel hydroxide-graphene composite powder has a lamellar structure, and the thickness of the lamellar layer is less than 100 nm.

(2) Adding the nano nickel hydroxide-graphene composite powder, a conductive agent SP and an adhesive PVDF into N-methyl pyrrolidone, and then performing ball milling to obtain modified slurry;

(3) and uniformly coating the modified slurry on the surface of one side of the polyethylene/polypropylene double-layer diaphragm body, baking at the temperature of 60 ℃ for about 24 hours, and drying to obtain the nano metal hydroxide modified lithium-sulfur battery diaphragm. Cut into sheets with a diameter of 17mm and then used as separators of button cells.

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

1) mixing the acidified carbon nano tube and the sublimed sulfur according to a certain mass ratio, uniformly mixing the mixture for a main material of a positive electrode material, preparing the main material, SP and PVDF binder into slurry (preferably 8:1:1) according to a certain mass ratio, coating the slurry on an aluminum foil, drying and rolling the aluminum foil, and cutting the aluminum foil into pole pieces with the diameter of 12 mm;

2) the electrochemical performance of the CR2025 button cell is tested after the CR2025 button cell is assembled in a glove box according to the sequence of the sulfur anode, the diaphragm and the metallic lithium, and the 0.2C first-time release efficiency of the assembled button cell reaches 1578mAh g^-1Close to the theoretical specific discharge capacity of sulfur (1645mAh g)^-1) The battery is charged and discharged for 5 times by 0.2C, 0.5C, 1C, 0.5C and 0.2C respectively, and the 0.2C specific discharge capacity of the battery is about 1175mAh g after the rate test^-1The capacity after 100 cycles at a charge-discharge rate of 0.2C was 920mAh g^-1For left and right, specific data refer to fig. 6, 7, and 8.

Example 3

A preparation method of a lithium-sulfur battery diaphragm modified by nanometer metal hydroxide comprises the following steps that the lithium-sulfur battery diaphragm comprises a diaphragm body, one side of the diaphragm body is coated with a modified coating, and the modified coating comprises metal hydroxide composite powder, a conductive agent SP and a binder PVDF; the mass ratio of the nickel hydroxide/manganese hydroxide composite material to the conductive agent SP to the adhesive PVDF is 8:1: 1;

the preparation method comprises the following steps:

(1) weighing 0.570g of nickel chloride hexahydrate, 0.119g of manganese chloride tetrahydrate and 0.540g of urea, putting the three into a beaker filled with 40mL of deionized water, stirring until the three are completely dissolved, transferring the aqueous solution into a reaction kettle, sealing, then preserving the temperature for 12 hours at 80 ℃ to generate black precipitates, collecting the precipitates, washing the precipitates with the deionized water for a plurality of times, and freeze-drying to obtain nano nickel hydroxide/manganese hydroxide composite powder, wherein the morphology of the composite material is shown in figure 4;

(2) adding the composite powder, the conductive agent SP and the adhesive PVDF into N-methyl pyrrolidone, and then grinding to obtain modified slurry;

(3) and uniformly coating the modified slurry on the surface of one side of the polypropylene diaphragm body, baking for about 12 hours at the temperature of 60 ℃ under the protection of inert gas, and then coating the other side of the diaphragm according to the mode to obtain the nano metal hydroxide modified lithium-sulfur battery diaphragm. Cut into sheets with a diameter of 17mm and then used as separators of button cells.

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

1) mixing the acidified carbon nano tube and the sublimed sulfur according to a certain mass ratio, uniformly mixing the mixture for a main material of a positive electrode material, preparing the main material, SP and PVDF binder into slurry (preferably 8:1:1) according to a certain mass ratio, coating the slurry on an aluminum foil, drying and rolling the aluminum foil, and cutting the aluminum foil into pole pieces with the diameter of 12 mm;

2) the electrochemical performance of the CR2025 button cell is tested after the CR2025 button cell is assembled in a glove box according to the sequence of a sulfur positive electrode, a diaphragm and metallic lithium, the assembled button cell is charged and discharged for 5 times respectively at 0.2C, 0.5C, 1C, 0.5C and 0.2C, and the 0.2C specific discharge capacity of the cell is about 986mAh g after the rate test^-1The capacity after 100 cycles at a charge-discharge rate of 0.2C was 680mAh g^-1Left and right. Detailed description of the drawings referring to fig. 6, 7 and 8;

example 4

A preparation method of a lithium-sulfur battery diaphragm modified by nanometer metal hydroxide comprises the following steps that the lithium-sulfur battery diaphragm comprises a diaphragm body, one side of the diaphragm body is coated with a modified coating, and the modified coating comprises nanometer copper hydroxide powder, a conductive agent SP and an adhesive PVDF; the mass ratio of the nano copper hydroxide powder, the conductive agent SP and the adhesive PVDF is 8:1: 1;

the preparation method comprises the following steps:

(1) weighing 0.511g of copper chloride dihydrate and 0.540g of urea, putting the copper chloride dihydrate and the urea into a beaker filled with 80mL of deionized water, stirring until the copper chloride dihydrate and the urea are completely dissolved, transferring the aqueous solution into a reaction kettle, sealing, then preserving the temperature for 12 hours at 80 ℃ to generate black precipitates, collecting the precipitates, washing the precipitates with the deionized water for a plurality of times, and freeze-drying to obtain nano copper hydroxide powder, wherein the shape of the nano copper hydroxide powder is shown in figure 5;

(2) adding nano copper hydroxide powder, a conductive agent SP and an adhesive carboxymethylcellulose sodium/styrene butadiene rubber (CMC/SBR) into deionized water, and then grinding to obtain modified slurry;

(3) and uniformly coating the modified slurry on the surface of one side of the polyethylene/polypropylene/polyethylene three-layer diaphragm body, baking for about 12 hours at the temperature of 60 ℃ under the protection of inert gas, drying, and coating the other side of the diaphragm according to the method to obtain the nano metal hydroxide modified lithium-sulfur battery diaphragm. Cut into sheets with a diameter of 17mm and then used as separators of button cells.

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

1) mixing the acidified carbon nano tube and the sublimed sulfur according to a certain mass ratio, uniformly mixing the mixture for a main material of a positive electrode material, adding the main material, SP and a CMC/SBR (1: 1) adhesive in a certain mass ratio into deionized water to prepare slurry (preferably 8:1:1), coating the slurry on an aluminum foil, drying and rolling the aluminum foil, and cutting the aluminum foil into pole pieces with the diameter of 12 mm;

2) the electrochemical performance of the CR2025 button cell is tested after the CR2025 button cell is assembled in a glove box according to the sequence of a sulfur positive electrode, a diaphragm and metallic lithium, the assembled button cell is charged and discharged for 5 times respectively at 0.2C, 0.5C, 1C, 0.5C and 0.2C, and the 0.2C specific discharge capacity of the cell is about 1030mAh g after the rate test^-1The capacity after 100 cycles at a charge-discharge rate of 0.2C was 660mAh g^-1Left and right. Specific data refer to fig. 6, 7 and 8.

Comparative example 1

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

(1) mixing a multi-wall carbon tube and sulfur simple substance powder in a ratio of 2: 8, mixing, uniformly grinding in a mortar, adding 10% of adhesive PVDF and 10% of conductive agent SP after hot melting at 155 ℃, preparing slurry by N-methylpyrrolidone according to a proper proportion, and rolling on an aluminum foil to obtain the positive plate. The button cell adopts the specification of CR2025, the pole piece is coated on one side, the diameter is 12 mm;

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

the electrolyte adopts Dioxolane (DOL): ethylene glycol dimethyl ether (DME) is 1:1, 0.15M anhydrous lithium nitrate and 1.0M lithium bis (trifluorosulfonyl) imide (LiTFSI) were added; the cathode adopts a metal lithium sheet with the thickness of 0.5mm, the battery diaphragm adopts a commercial polypropylene diaphragm (Celgard 2400), the arranged button cell is charged and discharged for 5 times respectively at 0.2C, 0.5C, 1C, 0.5C and 0.2C, and the 0.2C specific discharge capacity of the cell is about 691mAh g after the rate test^-1Charging and discharging at 0.2CThe capacity after 100 cycles of circulation under the electric multiplying power is 500mAh g^-1Left and right. Specific data refer to fig. 6, 7 and 8.