Preparation And Electrochemical Properties Of Interlayer Of Cobalt Selenide/Carbon Cloth Composites

The development of society is inseparable from the supply of energy,the consumption and utilization of traditional energy is approaching the bottleneck,the utilization and storage of renewable energy has become a hot spot of research today.At present,the most successful one is lithium-ion battery,which is widely used in life due to its stable capacity and long cycle life.However,people still need to pursue higher energy density to meet the rapid development of human society.Among them,lithium-sulfur batteries have received more and more attention because of their high energy density and still fall under the lithium-ion battery system.Up to now,the capacity of lithium-sulfur batteries has been close to the theoretical capacity value,but the existence of shuttle effect seriously affects the battery life,thus restricting the commercialization of lithium-sulfur batteries.There are three main methods to improve the shuttle effect:physical domain limitation,chemisorption,and catalytic conversion.In this paper,from the perspective of catalytic conversion,a structure of cobalt selenide catalyst loaded on carbon cloth is designed as an intermediate layer for lithium-sulfur batteries.Selenide,as a homologous element of oxides and sulfides,has similar crystal structure and polar characteristics,has affinity for sulfur and sulfides,and promotes the conversion kinetics of polysulfides.We selected the transition metal Co element,which has excellent performance in the battery,as the metal compound,and the composite material achieves the conductivity and catalytic properties in one,which effectively reduces the shuttle effect in the battery reaction.The main research of this paper is as follows.(1)Modified carbon cloth(CCO)was successfully pretreated by hydrothermal method using carbon cloth(CC)as raw material and concentrated nitric acid(HNO₃)as oxidizing agent to obtain the original carbon cloth.After scanning tests,it was found that CCO has richer pores and three-dimensional structure than CC fibers,and the degree of disorder and defects is higher.Therefore,as an intermediate layer,CCO has a faster ion transport rate and lower internal resistance,resulting in a better circulation capacity than CC.(2)A layer of cobalt selenide nanosheets was covered on the surface of the modified carbon cloth,and the characterization results showed that a layer of cobalt selenide nanosheets with a diameter of 60 nm was uniformly covered on the surface of the carbon cloth.The cycle performance,multiplicative performance and electrochemical impedance of the battery were significantly improved by using S/KB as the anode of the lithium-sulfur battery and cobalt selenide covered carbon cloth as the intermediate layer on the anode side,compared with the battery with and without the intermediate layer of carbon cloth only.The initial capacity of the improved battery was 1380 m Ah g^-1 at 0.1 C,and the capacity remained at 1100 m Ah g^-1 after 200 cycles,and the capacity remained at 596 m Ah g^-1 after 500 cycles even at a high current density of 1 C,with a decay rate of 0.06%per cycle.Subsequent polysulfide adsorption tests and deposition experiments proved that the cobalt selenide carbon cloth composites could indeed enhance the reaction kinetics of polysulfides and effectively suppress the shuttle problem in the battery reaction,thus improving the electrochemical performance of the lithium-sulfur batteries.