Selenium-Doped Sulfurized Polyacrylonitrile Hybrid Cathodes with Ultrahigh Sulfur Content for High-Performance Solid-State Lithium Sulfur Batteries

The solid-state lithium sulfur battery (SSLSB) is an attractive next-generation energy storage system by reason of its remarkably high energy density and safety. However, the SSLSB still faces critical challenges, such as sluggish reaction kinetics, mismatched interface, and undesirable reversible capacity. Herein, a high-performance SSLSB is reported using sulfurized polyacrylonitrile with rich selenium-doped sulfur (Se/S–S@pPAN) as a cathode and poly(ethylene oxide)/Li7La3Zr1.4Ta0.6O12 (PEO-LLZTO) as an electrolyte. The sulfur content of the cathode up to 60.9 wt % can be achieved by dispersing selenium sulfide (SeSx) species in the sulfurized polyacrylonitrile (S@pPAN) skeleton at a molecular level. Selenium as a eutectic accelerator can be uniformly distributed in the composite through the Se–S bond and can accelerate the reaction kinetics. The PEO-LLZTO hybrid solid-state electrolyte (SSE) displays an attractive electrochemical performance and provides an intimate contact with electrodes. At 60 °C, Se/S–S@pPAN delivers an impressive discharge capacity of 1042 mAh g–1 at 0.1C and 445 mAh g–1 at 1C. Additionally, the LiFePO4 cathodes combined with PEO-LLZTO deliver a high reversible capacity (158.9 mAh g–1, 1C) and an ultralong lifespan (a capacity retention of 80%, 1000 cycles) at 1C. The synergetic design of the high-performance sulfur cathode and the organic/inorganic hybrid electrolyte is crucial for enabling the high-performance SSLSB.