Layer Structured Chalcogenides For High-performance Lithium-sulfur Batteries

Due to high theoretical capacity of 1675 m A h g^-1,high energy storage density of2500 Wh kg^-1 and low cost,lithium sulfur battery has attracted special attention and has gradually become one of the most promising candidates for the next generation of energy storage devices.However,due to a series of problems in the working process of sulfur electrode,the low utilization rate of sulfur element has seriously affected the commercial application of lithium sulfur battery.Layered structure sulfides have been widely used in the fields of energy storage and energy conversion due to their band gap and crystal phase regulation and unique electrical properties.The purpose of this paper is to study the application of layered structure sulfides in lithium sulfur system.Mo Se₂@r GO composite material,Mo Se₂@r GO as the membrane coating and Mo Se₂@r GO as the positive electrode coating were prepared by solvent heat method to study the effect of layered structure sulfides on the performance of lithium sulfur battery.Specific research contents and results are as follows:First,the GO prepared by improved Hummers method was used as the carbon source,and then the Mo Se₂@r GO composite material was prepared by solvent heat method.Mo Se₂@r GO has high specific surface area and abundant micropores and mesopore.And the Mo Se₂@r GO has a strong adsorption performance on polysulfide.Second,the Mo Se₂@r GO composite material was used to modify the separator,and a pure sulfur electrode was used as a standard positive electrode assembled battery.The discharge capacity of the Mo Se₂@r GO coated separator battery reached 1034m A h g^-1 at 0.2 C rate.After 100 cycles,the capacity of 436 m A h g^-1 was still maintained.After 500 cycles at 1 C rate,the capacity decay rate per cycle is only 0.04%.Third,the Mo Se₂@r GO was coated on the positive electrode by scraping and coating.The Mo Se₂@r GO coating directly contact with the positive electrode,providing a larger reaction site for the active sulfur reaction and better preventing the passage of polysulfide.Under the catalysis of polar Mo Se₂,the captured sulfur can be reused.At a rate of 1 C,the capacity of each cycle decays to 0.03%.At a rate of 2 C,it has the performance of 554 m A h g^-1.In addition,the self-discharge test observed that the battery with positive Mo Se₂@r GO coating maintained two distinct discharge platforms in the first discharge after 12 hours of standing.