Application Of Selenium-doped Sulfurized Polyacrylonitrile In High Performance Lithium-sulfur And Room Temperature Sodium-sulfur Batteries

The theoretical specific capacity of sulfur?S?is as high as 1675 mAh g^-1,and sulfur is low cost,naturally abundant and environmentally friendly.When coupled with lithium or sodium anode,the lithium-sulfur?Li-S?and room temperature sodium-sulfur?RT Na-S?are considered as the promising candidates for high energy density battery system.However,there are still some problems in the practical application of Li-S or RT Na-S batteries,including the insulated nature of S,dissolution of polysulfides and the shuttling effect.Sulfurized pyrolyzed polyacrylonitrile?S@pPAN?is a promising candidate which can partly inhibit the dissolution of polysulfides in Li-S or RT Na-S batteries.Selenium?Se?belongs to the same column with S in the periodic table,shows much better conductivity,and has been successfully used in high-rate sodium-selenium batteries.Herein,we propose to use Se as eutectic accelerator in S@pPAN to boost reaction kinetics for high performance Li-S and RT Na-S batteries.The lithium or sodium storage properties of the Se-doped S@pPAN composites have been studied as follows:?1?The differences of morphology,structure and electrochemical properties of SeS₂@pPAN composites synthesized under different temperatures have been analyzed.The results show that the SeS₂@pPAN cathode materials synthesized at 450?has the highest theoretical capacity and exhibits the best electrochemical properties in carbonate electrolytes.At the same time,the composites exhibit the excellent rate performance in ether electrolytes.The discharge capacity is up to 800 mAh g^-1 at 3 A g^-1.?2?Se_0.08S_0.92@pPAN cathode materials exhibit excellent electrochemical performance in carbonate and ether electrolytes for RT Na-S batteries.Compared with S@pPAN,the electrochemical performance of Se_0.08S_0.92@pPAN is significantly improved.Further kinetic analysis shows that a small amount Se doping can effectively reduce the diffusion barrier of sodium ion and improve the diffusion rate of sodium ion.The results show that using Se as“eutectic accelerator”could effectively inhibit the dissolution of polysulfides in RT Na-S batteries,and greatly reduce the self-discharge performance of RT Na-S batteries.