A three-in-one C60-integrated PEO-based solid polymer electrolyte enables superior all-solid-state lithium–sulfur batteries

Abstract

Polyethylene oxide (PEO) is a potential solid polymer electrolyte for all-solid-state lithium–sulfur batteries, yet its practical application has been hindered due to the low ionic conductivity, serious lithium dendrite growth, and uncontrolled shuttle effect. Fullerene (C₆₀) is a versatile additive for solid polymer electrolytes, since it lacks electronic conductivity, and the curved π surface of C₆₀ tends to interact with the n-orbitals of the PEO ether oxygen. Herein, a multifunctional additive, C₆₀, is proposed to compensate for the intrinsic imperfection of the PEO electrolyte. The unique 0D molecular structure of C₆₀ promotes the ionic conductivity from 0.57 × 10⁻⁴ to 1.27 × 10⁻⁴ S cm⁻¹ at 60 °C by boosting the chain segment movement of PEO and dissociating the ion association of LiTFSI. The high interface energy of C₆₀ towards Li can effectively block the growth and penetration of Li dendrites, which is responsible for the stable cycling durability for 1000 h. With the integration of C₆₀, the rate-determining liquid–solid conversion process is selectively facilitated to retard polysulfide shuttle, and furthermore, the Li₂S decomposition energy barrier is reduced in the lithium–sulfur electrochemistry. We highlight that the PEO–C₆₀ solid polymer electrolyte endows the all-solid-state lithium–sulfur batteries with improved rate performance, long-span-life stability, and enhanced safety features.