阅读说明：本技术 一种石墨烯-氮化钴的Li-S电池隔膜及其制备方法 (Graphene-cobalt nitride Li-S battery diaphragm and preparation method thereof ) 是由 吴淏 赵丹 王宏志 李耀刚 张青红 候成义 于 2019-09-04 设计创作，主要内容包括：本发明涉及一种石墨烯-氮化钴的Li-S电池隔膜及其制备方法,制备：石墨烯-氮化钴分散液,然后采用滤膜进行抽滤,真空烘干,即得。本发明中利用该隔膜组装的Li-S电池具有优异的电学性能和循环稳定性,能够极大的拓展Li-S电池的应用市场。制备方法简单快速,成本低廉,易于操作,易于产业化。(The invention relates to a graphene-cobalt nitride Li-S battery diaphragm and a preparation method thereof, and the preparation method comprises the following steps: and (3) carrying out suction filtration on the graphene-cobalt nitride dispersion liquid by adopting a filter membrane, and drying in vacuum to obtain the graphene-cobalt nitride dispersion liquid. The Li-S battery assembled by the diaphragm has excellent electrical property and cycling stability, and the application market of the Li-S battery can be greatly expanded. The preparation method is simple and quick, has low cost, is easy to operate and is easy to industrialize.)

1. The graphene-cobalt nitride/filter membrane battery diaphragm is characterized in that the diaphragm is formed by vertically stacking graphene-cobalt nitride laminar materials on a filter membrane to form a continuous network structure.

2. The membrane of claim 1, wherein the filter membrane is polypropylene PP; the diaphragm is circular, the diameter of the diaphragm is 1.9-2.1 cm, and the thickness of the diaphragm is 29.8-30.2 μm.

3. A preparation method of a graphene-cobalt nitride/filter membrane battery diaphragm comprises the following steps:

(1) adding graphene oxide GO into water, performing ultrasonic crushing to obtain GO aqueous solution, then adding aqueous solution of cobalt salt, performing magnetic stirring, and performing ultrasonic crushing to obtain GO-Co³⁺A solution;

(2) the GO-Co in the step (2) is treated³⁺Adding a dimethyl imidazole aqueous solution into the solution, magnetically stirring, standing, performing suction filtration, freeze-drying, and nitriding to obtain a graphene-cobalt nitride compound;

(3) and dispersing the graphene-cobalt nitride compound in a solvent, crushing cells to obtain a graphene-cobalt nitride dispersion solution, performing suction filtration by using a filter membrane, and drying in vacuum to obtain the Li-S battery diaphragm.

4. The preparation method of claim 3, wherein the concentration of the GO aqueous solution in the step (1) is 0.4-1.0 wt%.

5. The method according to claim 3, wherein the cobalt salt in the step (1) is CoCl₃(ii) a The concentration of the aqueous solution of cobalt salt is 3.0-6.0 wt%.

6. The preparation method according to claim 3, wherein the aqueous solution of cobalt salt is added in the step (1), magnetic stirring is carried out for 5-10min, and ultrasonic crushing is carried out for 1-1.5 h.

7. The method according to claim 3, wherein the concentration of the aqueous solution of dimethylimidazole in the step (2) is 5.0 to 10.0 wt%.

8. The preparation method according to claim 3, wherein the ratio of GO to the aqueous solution of cobalt salt to the aqueous solution of dimethylimidazole in steps (1) and (2) is 0.20-0.5 g: 8-12 mL: 8-12 mL.

9. The method according to claim 3, wherein the nitriding in the step (2) is specifically performed by: nitriding in a tube furnace with NH first₃Discharging the excessive oxygen in the tube furnace with the ventilation time of 0.5-1.0 h; setting the initial temperature to be 30-50 ℃, heating the furnace for 110-114 min at the speed of 5 ℃/min to raise the temperature in the furnace to 600 ℃, keeping the temperature for 3-4 h for nitriding, and after the nitriding is finished, reducing the temperature in the furnace to be below 100 ℃ to obtain the graphene-cobalt nitride compound.

10. The method according to claim 3, wherein the solvent in step (3) is ethanol, and the filter membrane is polypropylene PP; the concentration of the graphene-cobalt nitride dispersion liquid is 0.1-0.3 mg/mL.

11. A graphene-cobalt nitride/filter membrane battery separator prepared by the method of claim 3.

12. Use of the graphene-cobalt nitride/filter membrane battery separator of claim 1 as a Li-S battery separator.

Technical Field

The invention belongs to the field of Li-S battery diaphragms and preparation thereof, and particularly relates to a graphene-cobalt nitride Li-S battery diaphragm and a preparation method thereof.

Background

In recent years, with the rapid development of electric automobiles, people have long-term mileage on vehiclesThe demand is higher and higher, and the capacity of the power battery of the vehicle is urgently increased. In view of the above, conventional battery materials, such as lithium cobaltate, lithium manganate and lithium titanate, have not been able to meet the overall development requirements. Therefore, it is urgent to develop a new electrode material having a high specific capacity and a high energy density. The sulfur simple substance has rich resources and low toxicity in nature, and the Li-S battery system which is used as the anode material and is composed of the sulfur simple substance and the metallic lithium can ensure that the mass and the volume energy density respectively reach 2600Wh & Kg-¹And 2800 Wh. L^-1And has a power of 1675mA h.g^-1The theoretical specific capacity of (a).

However, the disadvantages of Li-S batteries are also quite evident. Sulfur has poor conductivity, and the volume of the positive electrode is easy to expand in the cycle process, wherein polysulfide generated by the positive electrode is easy to dissolve in electrolyte and diffuse to the negative electrode in the charge-discharge process, so that the shuttle effect is caused, the cycle stability of the Li-S battery is influenced, and the main factors of low specific discharge capacity and rapid capacity attenuation are caused.

The graphene-cobalt nitride/PP diaphragm is prepared by synthesizing a graphene-cobalt nitride compound and is applied to a Li-S battery. By utilizing the chemical adsorption effect of polysulfide on graphene-cobalt nitride, the effect of preventing the polysulfide from dissolving and diffusing is achieved, so that the shuttle effect of the polysulfide can be reduced to a great extent, the stability of the battery can be improved, the application field of the Li-S battery is expanded, and the industrialization process of the Li-S battery is accelerated.

The graphene-based porous carbon sheet material is prepared by CN 108365153A and is applied to a Li-S battery diaphragm. In the patent, the graphene-based material has the problems of less heteroatom doping and poor polysulfide adsorption due to heteroatom adsorption after being sintered by nitrogen, so that the Li-S battery has low performance. Based on the method, more pyrrole nitrogen is doped on the surface of the graphene through ammonia gas sintering, a cobalt nitride compound is produced, and the pyrrole nitrogen and lithium polysulfide form a chemical bond, so that the diffusion of polysulfide is inhibited, the shuttle effect is reduced, and the utilization rate of active substance sulfur is improved. The invention can overcome the defect of lithium polysulfide diffusion brought by the prior art and is a short plate with low battery stability.

Disclosure of Invention

The invention aims to solve the technical problem of providing a graphene-cobalt nitride Li-S battery diaphragm and a preparation method thereof, and overcomes the defects that the prior art is lack of effective nitrogen atom doping, nitrogen atom-polysulfide chemical bond formation, and the polysulfide shuttling problem of a Li-S battery cannot be effectively inhibited. The method takes Co-2MIM growing on graphene as a main body and adopts high-temperature NH₃Ammoniation, and then carrying out suction filtration to obtain the diaphragm.

The graphene-cobalt nitride/filter membrane battery diaphragm is formed by vertically stacking graphene-cobalt nitride laminar materials on a filter membrane to form a continuous network structure.

The filter membrane is polypropylene PP; the diaphragm is circular, the diameter of the diaphragm is 1.9-2.1 cm, and the thickness of the diaphragm is 29.8-30.2 μm.

The invention discloses a preparation method of a graphene-cobalt nitride/filter membrane battery diaphragm, which comprises the following steps:

(1) adding GO into water, carrying out ultrasonic crushing for 12-18 min to obtain a GO aqueous solution, then adding a cobalt salt aqueous solution, carrying out magnetic stirring, and carrying out ultrasonic crushing to obtain graphene oxide-cobalt ions (GO-Co)³⁺) Interlayer separation to obtain GO-Co³⁺A solution;

(2) the GO-Co in the step (2) is treated³⁺Adding a dimethyl imidazole aqueous solution into the solution, magnetically stirring for 5-10min, standing for 50min, performing suction filtration, freeze-drying to obtain a Co-2MIM/GO compound, and nitriding to obtain a graphene-cobalt nitride compound;

(3) and dispersing the graphene-cobalt nitride compound in a solvent, crushing cells for 2.0-2.5 h to obtain a graphene-cobalt nitride dispersion solution, then performing suction filtration by using a filter membrane, and performing vacuum drying to obtain the Li-S battery diaphragm.

The preferred mode of the above preparation method is as follows:

in the step (1), the ratio of GO to water in the graphene oxide GO aqueous solution is 0.20-0.28 g: 70-80 mL.

The cobalt salt in the step (1) is CoCl₃(ii) a The concentration of the aqueous solution of cobalt salt is 3.0-6.0 wt%.

Adding an aqueous solution of cobalt salt in the step (1), magnetically stirring for 5-10min, and ultrasonically crushing for 1-1.5 h.

In the steps (1) and (2), the ratio of the graphene oxide GO to the cobalt salt aqueous solution to the dimethyl imidazole aqueous solution is 0.20-0.28 g to 8-12 mL.

The concentration of the dimethyl imidazole aqueous solution in the step (2) is 5.0-10.0 wt%.

The nitriding in the step (2) is specifically as follows: putting the compound into a clean crucible, putting the crucible into a tubular furnace for ammoniation, and introducing NH firstly₃Discharging the excessive oxygen in the tube furnace with the ventilation time of 0.5-1.0 h; setting the initial temperature to be 30-50 ℃, heating the furnace for 110-114 min at the speed of 5 ℃/min to raise the temperature in the furnace to 600 ℃, keeping the temperature for 3-4 h for nitriding, and after the nitriding is finished, reducing the temperature in the furnace to be below 100 ℃ to obtain the graphene-cobalt nitride compound.

In the step (3), the solvent is ethanol, and the filter membrane is polypropylene PP; the concentration of the graphene-cobalt nitride dispersion liquid is 0.1-0.3 mg/mL. The graphene-cobalt nitride/filter membrane battery diaphragm prepared by the method is provided by the invention.

The graphene-cobalt nitride/filter membrane battery diaphragm is applied as a Li-S battery diaphragm.

The Li-S battery is a lithium sulfur battery.

Advantageous effects

(1) The diaphragm is composed of a graphene-cobalt nitride compound and a commercial polypropylene (PP) battery diaphragm, can block the shuttle effect of polysulfide in the Li-S battery, is used for improving the circulation stability of the Li-S battery, and can realize large-scale production;

(2) the preparation method is simple and feasible, and the obtained graphene-cobalt nitride/PP membrane has a continuous network structure;

(3) the graphene-cobalt nitride/PP diaphragm prepared by the invention provides a new idea for improving the performance of the Li-S battery;

(4) the graphene-cobalt nitride/PP diaphragm disclosed by the invention not only has stable performance of a graphene material, but also can adsorb diffusion of polysulfide in an organic electrolyte through a chemical action, so that the cycle stability and the working efficiency of a Li-S battery are improved;

(5) when the graphene-cobalt nitride/PP diaphragm prepared by the invention is charged and discharged in the first circle, due to the performance of the graphene, extra compensation capacity can be provided for the Li-S battery, and the specific capacity of the battery is further improved;

(6) the preparation method is simple in preparation process, easy to operate, suitable for industrial production and low in cost;

(7) the graphene-cobalt nitride/PP diaphragm can be directly and stably existed in a Li-S battery, can improve the efficiency of the battery, and has important scientific value and wide application prospect in the wearable field;

(8) the preparation method is simple and feasible, and is convenient for industrial production, and the prepared graphene-cobalt nitride diaphragm has excellent chemical stability and can greatly improve the cycle efficiency and specific capacity of the Li-S battery.

Drawings

Fig. 1 is a digital photograph of the graphene-cobalt nitride/PP separator prepared in example 1; wherein (a) is a pure PP diaphragm and a graphene-cobalt nitride/PP diaphragm, and (b) is the thickness of the pure PP diaphragm; (c) the digital photo of the thickness of the graphene-cobalt nitride/PP membrane is obtained;

FIG. 2 is an FE-SEM photograph of examples 2 and 3; wherein, the images (a) and (b) are FE-SEM pictures of a pure PP membrane, and the pore diameter of the pure PP membrane is about 400 nm; FIGS. (c) and (d) are FE-SEM photographs of graphene-cobalt nitride/PP membrane, wherein the diameter of the graphene-cobalt nitride sheet is about 400nm, and the size of the cobalt nitride particles is about 50nm attached to the surface of the graphene sheet; FIGS. (e) and (f) are FE-SEM photographs of the graphene/PP separator, the size of the graphene sheet layer being about 10 μm;

fig. 3 is a graph of cycle performance of pure PP separator, graphene/PP separator and graphene-cobalt nitride/PP separator applied to Li-S battery, compared to example 1 and example 3 in comparative example 1; (b) the (c) and (d) are pure PP diaphragms, graphene/PP diaphragms and specific capacity and voltage relation graphs of the graphene-cobalt nitride/PP diaphragms, wherein black is the charge and discharge of the first circle; red is the second charge and discharge; blue is the third charge-discharge diagram.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

GO was manufactured by Nanjing Xiancheng nanomaterial science and technology Limited: 1-5 μm; both cobalt chloride and dimethylimidazole were supplied by Aladdin Chemicals, Inc.