All-solid-state lithium-sulfur batteries assembled by composite polymer electrolyte and amorphous sulfur/rGO composite cathode

All-solid-state lithium‑sulfur batteries are becoming a breakthrough technology for energy storage systems due to its high energy density , high safety and low cost of sulfur. However, its application has been restricted by the isolating properties of sulfur (S), as well as S shuttle effect, S volume effect, and low electron conductivity. In this work, the amorphous sulfur-reduced graphene oxide (S/rGO) composite cathode material was prepared with a smaller particle size of about 2 nm S onto rGO to alleviate the volume effect of S (after 30 cycles, the charge transfer impedance changes about only 3 Ω); at the same time, highly conductive rGO maintain good ionic conduction during charge-discharge cycling. Along with the cathode material, we fabricated a composite polymer electrolyte (CPE) based on poly (ethylene oxide), lithium-ion conductor Li 6.4 Ga 0.2 La 3 Zr 2 O 12 -succinonitrile (PEO 18 - LiTFSI-LLZO-SN) possessing lithium conductivities of 1.16 × 10 −4 and 7.26 × 10 −4  S cm −1 at room temperature and 60 °C, respectively, which can mitigate the transport of polysulfide and be suitable for battery applications. The composite cathode material exhibits an initial discharge capacity of 783mAh g −1 at 45 °C, with a capacity retention rate of 81.2% at 0.2C after 60 cycles. At 60 °C, the battery shows excellent electrochemical cyclability 820mAh g −1 of reserved capacity after stable operation for 100 cycles at 0.2C. The synergy between the CPE and the amorphous S/rGO composite cathode demonstrated in this work may bring insights to improve the cycling performance of all-solid-state Li-S batteries