High-Electrochemical-Activity\nComposite Cathode Enabled\nby Fast Segmental Relaxation for Solid-State Lithium–Sulfur\nBatteries

Solid-state\nlithium–sulfur batteries (SSLSBs)\nhave attracted\na great deal of attention because of their high theoretical energy\ndensity and intrinsic safety. However, their practical applications\nare severely impeded by slow redox kinetics and poor cycling stability.\nHerein, we revealed the detrimental effect of aggregation of lithium\npolysulfides (LiPSs) on the redox kinetics and reversibility of SSLSBs.\nAs a paradigm, we introduced a multifunctional hyperbranched ionic\nconducting (HIC) polymer serving as a solid polymer electrolyte (SPE)\nand cathode binder for constructing SSLSBs featuring high electrochemical\nactivity and high cycling stability. It is demonstrated that the unique\nstructure of the HIC polymer with numerous flexible ether oxygen dangling\nchains and fast segmental relaxation enables the dissociation of LiPS\nclusters, facilitates the conversion kinetics of LiPSs, and improves\nthe battery’s performance. A Li|HIC SPE|HIC-S battery, in which\nthe HIC polymer acts as an SPE and cathode binder, exhibits an initial\ncapacity of 910.1 mA h g<sub>S</sub><sup>–1</sup> at 0.1C and\n40 °C, a capacity retention of 73.7% at the end of 200 cycles,\nand an average Coulombic efficiency of approximately 99.0%, demonstrating\nhigh potential for application in SSLSBs. This work provides insights\ninto the electrochemistry performance of SSLSBs and provides a guideline\nfor SPE design for SSLSBs with high specific energy and high safety.