Sulfide-Loaded Carbon Nanofibers Interlayer For Lithium-Sulfur Batteries

In recent years,lithium-sulfur battery has received a lot of attention,and is considered as a potential next generation energy storage system for high specific capacity and high specific energy.However,multi-electron,multi-step,and multi-phase transformation redox reactions between elemental sulfur and lithium metals can cause many problems.In particular,the shuttle effect of soluble lithium polysulfide will lead to rapid decay of battery capacity,which seriously limits the pace of practical application of lithium-sulfur battery.In order to improve the cycle stability of lithium-sulfur battery,this paper prepared the interlayer with physical blocking,chemical adsorption and catalytic conversion of lithium polysulfides from the inhibition of shuttle effect.The main research contents and results obtained are as follows:1.A carbon nanofibers（CNFs）film with a three-dimensional conductive network structure was prepared by electrospinning technology combined with carbonization treatment.Then Zn S nanoparticles are grown on CNFs thin films by solvothermal synthesis to obtain an interlayer that can be used in lithium-sulfur battery.The three-dimensional conductive network structure of CNFs has a lager specific surface area,which is beneficial to the infiltration of the electrolyte and rapid ion transmission.The Zn S nanoparticles grown on the surface of CNFs enhance the adsorption of lithium polysulfides through polar interaction,which in turn effectively catalyzes the conversion of lithium polysulfides.After optimization,the prepared Zn S@CNFs interlayer has a first discharge specific capacity of 1045.4 m Ah g^-1 at 0.5 C,and retains625.7 m Ah g^-1 after 500 cycles.The average attenuation rate of each cycle is 0.08%,which significantly improves the cycle stability of the battery.2.Carbon nanofibers loaded with Co S nanoparticles（Co S@CNFs）were designed and constructed as the interlayer of lithium-sulfur battery.Compared with Zn S,Co S has the advantages of better electrical conductivity,the stronger chemical interaction of lithium polysulfides and the stronger catalytic conversion performance.Electrochemical tests show that as the interlayer of lithium-sulfur battery,the prepared Co S@CNFs composite materials can greatly reduce the charge transfer impedance and Li⁺diffusion impedance of the battery.In addition,Co S participates in redox reactions and contributes capacity during the first discharge of the battery.The optimized Co S@CNFs interlayer battery has an initial discharge capacity of 1609.5m Ah g^-1 at 1C,showing improved rate performance and extended cycle life.