Structural reconfiguration of PEO frameworks via β-cyclodextrin as solid polymer electrolyte for superior all-solid-state lithium-sulfur batteries

Polyethylene oxide (PEO) is widely considered to be a highly promising solid polymer electrolyte (SPE) owing to its flexibility, excellent mechanical and chemical stability, and safety. However, PEO still faces challenges in the application of all-solid-state lithium-sulfur batteries (ASSLSBs), such as low ion transport efficiency, lithium dendrite formation, and complex polysulfide shuttle effects. Herein, a unique ring-funnel β-cyclodextrin (β-CD) is introduced as a functional additive into the PEO matrix for structural reconfiguration as a composite solid electrolyte (CSE). The strong non-covalent interactions between β-CD and PEO reveals that the ordered arrangement of the PEO chains is disrupted because the dihedral and torsional angles are disturbed. These interactions significantly expand the amorphous regions of PEO, which increases the ion transport pathways and enhances the chain flexibility to improve ionic conductivity and electrochemical performance. Additionally, β-CD could strengthen the immobilization of TFSI⁻, further promoting Li⁺ dissociation and rapid migration, while effectively suppressing lithium dendrite growth and the polysulfide shuttle effect. As a result, the discharge capacity of ASSLSBs with PEO-LiTFSI-β-CD retain at 650.5 mAh·g⁻ 1 after 200 cycles, exhibiting a coulombic efficiency close to 98 %, which provide a novel design strategy for preparing high-performance and durable SPE for ASSLSBs.