Modified diaphragm and preparation method and application therefor

Abstract

The invention discloses a modified diaphragm. The modified diaphragm comprises a diaphragm substrate, and an electronic conductive coating layer and an inorganic hard coating layer positioned on the two surfaces of the diaphragm substrate respectively, wherein the electronic conductive coating layer is a mixed coating layer with graphene and a porous carbon material; and the inorganic hard coating layer is a nitrogen-carbon material coating layer, a nitrogen-silicon material coating layer, a carbon-boron material coating layer or a silicon-carbon material coating layer. The preparation method comprises the steps of uniformly coating the two surfaces of the diaphragm substrate with the electronic conductive coating layer and the inorganic hard coating layer respectively, and drying the two surfaces respectively obtain the modified diaphragm. The modified diaphragm has high diffusion and absorption capacity for an organic electrolyte, high ionic conductivity, and an obvious adsorption and blocking effect on poly-sulfur-lithium; in addition, the modified diaphragm can further restrain a shuttle effect, prevent battery short-circuit, effectively restrain the growth of negative electrode metal lithium dendrites in a cyclic process, prevent from punching the diaphragm, and protect the lithium negative electrode, so that the problem that the diaphragm is punched after dendrites formation is solved, and the safety performance of the battery is improved.

Description

Technical field [0001] The invention relates to the technical field of lithium-sulfur batteries, in particular to a modified diaphragm with double-sided modification, a preparation method thereof, and a lithium-sulfur battery. Background technique [0002] With the continuous advancement of science and technology and the rapid development of electronic products, people urgently need a battery system with high energy density and environmental friendliness, so lithium-sulfur batteries have gradually entered the field of vision of researchers. [0003] Comparing with traditional lithium ion battery cathode material LiCoO 2 , LiMn 2 O 4 , LiPFeO 4 In comparison, the sulfur cathode material for lithium-sulfur batteries has a higher theoretical specific capacity (1675mAh / g) and a higher energy density (2600Wh / kg). It is currently known as the second highest energy density other than lithium-air batteries. Secondary battery system. In addition, the positive electrode raw material is rich...

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Problems solved by technology

In terms of diaphragm modification, porous carbon nanotube / polyethylene glycol modified diaphragm [GuanchaoWang, Royal Society of Chemistry A, 2015, 3, 7139], carbon modified diaphragm [Shengheng Chung, AdvFunctMater, 2014, 24, 5299-5306] and other functional diaphragms The application of lithium-sulfur batteries improves the cycle life and rate performance of lithium-sulfur batteries. However, the carbon material is coated on the separator. Due to the pore structure of the separator and the electronic conductivity of the carbon material, it is easy to cause a short circuit after assembling the battery. Feasible measures were proposed for negative electrode protection. The application of alumina modified separator [ZhiyongZhang, ElectrochimicaActa, 129(2014) 55-61] improved the performance of lithium-sulfur batteries, but the adsorption capacity of alumina was weak, and there was no proposal for lithium negative electrode protection. Feasible measures

Therefore, there is no research on a modified separator that can not only improve the cycle life and rate performance of lithium-sulfur batteries, but also provide protective measures for the protection of lithium anodes, especially the problem of lithium dendrites piercing the separator after formation.

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