A mixed electron/ion conducting interlayer enabling ultra-stable cycle performance for solid state lithium sulfur batteries

Replacement liquid electrolyte with solid polymer electrolytes (SPEs) is an effective strategy to boost the development of high performance lithium sulfur (Li–S) batteries. However, most of reported solid state Li–S batteries (SSLSBs) with SPEs show unsatisfying cycle performances owing to low utilization of S and notorious shuttle effect. In our case, to address above issues, a mixed electron/ion conducting interlayer which consists of carbon nanotubes, polyethylene oxide and lithium salt is introduced into SSLSBs. The carbon nanotubes and mixture of polymer/lithium salt construct conductive channels of electrons and Li ions, respectively, resulting in electronic/ionic conductivity of the interlayer. Additionally, the carbon nanotubes of interlayer can absorb polysulfides. Therefore, the interlayer can localize polysulfides and deliver electrons/Li ions to them, enabling polysulfides to accomplish redox reaction in the interlayer. The results shows that SSLSBs with interlayer deliver initial discharge capacity of 750 mAh g−1 at 0.05 C under ambient temperature, and 83.8% capacity is retained after 320 cycles. Even the current rate is increased to 0.1 C, the SSLSBs show an initial discharge capacity of 740 mAh g−1 with 70% capacity retention after 400 cycles. Undoubtedly, the strategy of the mixed electron/ion conducting interlayer will be a milestone to SSLSBs.