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

Abstract

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 Li6.4Ga0.2La3Zr2O12-succinonitrile (PEO18- 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