Laminar Composite Electrolytes with Nanoporous Sulfonated Covalent Organic Framework-Confined Crown Ether for Solid-State Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are one of the most promising next-generation energy storage systems due to their ultrahigh theoretical specific capacity. However, the sluggish redox kinetics and shuttle effect of lithium polysulfide of sulfur cathodes remain obstacles to their development. Herein, we synthesize a thin laminar composite TpPa-SO3H/2-Methylol-15-crown-5 solid-state electrolyte (TpPa-SO3H/15-C-5-OH SSE) by encapsulating the crown ether into nanoscale pores (1.2 nm) of TpPa-SO3H covalent organic framework (COF) through low-pressure filtration. Importantly, the hydrogen-bonding interaction between TpPa-SO3H COF and 15-C-5-OH largely enhances the stable existence of 15-C-5-OH in pores of TpPa-SO3H COF. The 15-C-5-OH confined in pores of TpPa-SO3H COF can form a long-range ordered cavity channel for effective Li+ transport. This endows TpPa-SO3H/15-C-5-OH SSE with high ionic conductivity of 1.31 × 10–5 S cm–1 at 30 °C and satisfactory Li+ transference number (tLi+) of 0.75. In addition, the negative charge of the sulfonate group on the TpPa-SO3H COF can repel the polysulfide anions efficiently through an electrostatic repulsion interaction, thereby blocking the migration of polysulfide. As a result, the Li–S battery with TpPa-SO3H/15-C-5-OH SSE presents superior cycling stability, which preserves a capacity of 739.9 mA h g–1 with a retention of 82.9% after 400 cycles at 60 and 0.5C.