Theoretical Study On The Anchoring Mechanism Of Polysulfides By Two-dimensional Layered Materials In Lithium-sulfur Batteries

In recent years,rechargeable lithium-sulfur(Li-S)batteries have broad application prospects in the next-generation high-energy storage devices due to their high theoretical specific energy density(2600 W h kg^-1).However,the problems of short cycle life and low Coulombic efficiency caused by poor electronic conductivity and large volume expansion of sulfur during charging and discharging,still restrict the commercial development of Li-S batteries.Especially,the intermediate long-chain polysulfides are easily soluble into the common organic electrolytes,and they will diffuse between the anode and cathode,resulting in“shuttle effect”that affects the battery performance.In order to solve the“shuttle effect”,two-dimensional materials are usually used as cathode anchoring materials for Li-S batteries to inhibit the dissolution of polysulfides.In this paper,the feasibility of different two-dimensional layered materials in Li-S battery cathode was predicted through density functional theory(DFT)calculations.The main research contents are as follows:Firstly,the group-VA two-dimensional layered materials including arsenene, antimonene and bismuthene were selected as the research subjects,and their potentials as cathode anchoring materials for Li-S batteries were investigated based on density functional theory.The adsorption energies,electronic properties,structural integrity and diffusion energy barriers of different polysulfides on these surfaces were calculated in detail.The results show that these materials have moderate adsorption energies for polysulfides while maintaining structural integrity.In addition,the low surface diffusion energy barriers ensure the efficient diffusion of polysulfides.Therefore,arsenene,antimonene and bismuthene can be promising cathode anchoring materials for improving the performance of Li-S batteries.Secondly,inspired by the successfully synthesized Janus Mo SSe,the anchoring performance and diffusion properties of Se and S surfaces with different properties in Janus Sn SSe to polysulfides were explored through DFT calculations by comparing with Sn Se₂and Sn S₂.The adsorption strength,electronic properties,catalytic conversion process and diffusion behaviors of polysulfides on three kinds of materials(four different surfaces)were comprehensively analyzed.The results show that the adsorption energies of polysulfides on Sn SSe are between Sn Se₂and Sn S₂,so that Sn SSe can trap polysulfides with moderate binding strength.The lower diffusion energy barriers of long-chain polysulfides on Sn SSe than Sn Se₂ensure the electrode reaction efficiency.Furthermore,the small Gibbs free energies and Li₂S decomposition barriers on Sn SSe endow Li-S battery with better performance.Thus,we believed that Janus Sn SSe has excellent performance and can be a potential cathode material to suppress the shuttle effect.Finally,the application prospect of Janus Ti SSe with better conductivity in Li-S battery cathode was explored based on DFT calculations,and their adsorption energies,charge transfer and catalytic conversion process were simply analyzed.Compared with the calculated results of Ti Se₂and Ti S₂,it is preliminarily predicted that Janus Ti SSe has the potential to act as the cathode anchoring material for Li-S batteries.