Lithium-rich high entropy oxide with abundant oxygen vacancies for composite polymer all-solid-state Li-S batteries

Poly(ethylene-oxide) (PEO)-based all-solid-state lithium-sulfur (Li-S) batteries simultaneously possess the advantage of extraordinary theoretical energy density and high safety, high machinability. However, the challenges of lithium polysulfide (LiPS) shuttling and insufficient Li+ conductivity hinder the batteries from practical application. In this work, a lithium-rich high entropy oxide with abundant oxygen vacancies (HL30) is developed as an active filler in PEO to concurrently address the two issues. Specifically, the addition of HL30 promotes the mobility of Li+ in PEO electrolyte as well as provides an extra high-efficiency pathway for Li+ transport, leading to large enhancement of the Li+ ionic conductivity. The metal species in HL30 could anchor the LiPS via bonding interaction while the surface oxygen vacancies further increase the bonding energy. As a result, the ionic conductivity of HL30-containing electrolyte reaches 5.06 x 10(-4) S cm(-1) at 60 degrees C, exceeding that of pure PEO electrolyte (2.45 x 10(-4) S cm(-1)) to a considerable extent. The coulombic efficiency of Li-S full battery decreases from 113 % to 103 %, revealing an efficient restriction of shuttling effect. This work provides a novel method of composite polymer electrolyte design to achieve the practical application of high-performance solid-state Li-S batteries.