Hierarchical Carbon Interlayer Design as Interfacial Stabilizer and In-Situ Solid-Electrolyte Infiltrate for High-Performance Solid-State Li–S Batteries

A great deal of attention has been paid to lithium–sulfur (Li–S) batteries due to their high energy density (>2600 Wh kg^–1), elemental abundance, and environmental friendliness, which show great application prospects in a wide range of energy storage systems. However, the shuttle effect caused by traditional liquid electrolyte remains a problem handicapping the development of the Li–S battery. In-situ polymerized gel polymer electrolytes (GPEs) with high ionic conductivity, high-voltage stability, and interfacial compatibility are spotlighted to solve the shuttle effect for better electrochemical performance. Here, we use Al(OTf)₃ to initiate DOL ring-opening polymerization to form GPEs. A hierarchical carbon interlayer, comprised of superaligned carbon nanotubes and Super P, was rationally organized with size exclusion effect (0.76 nm) to strengthen the interface stability and conversion of soluble lithium polysulfides for higher sulfur utilization. GPEs with ionic conductivity up to 1.74 mS cm^–1 and low interfacial impedance at room temperature are proposed, which infiltrate into the demonstrated hierarchical carbon interlayer to form HC@PP separators. The Li–S battery using the HC@PP separator exhibits higher sulfur utilization and discharge capacities (1332 mAh g^–1), improved rate capability, and 80% capacity retention at 1 C after 150 cycles, greatly surpassing the interlayer-free solid-state Li–S battery. Our work provides a promising in-situ polymerization strategy of GPEs with compatible hierarchical carbon interlayers design and its intrinsic interface regulation for a high-performance solid-state Li–S battery.