Electrolyte-as-binder strategy using in situ-formed PDOL gel for binder-free cathodes in flexible quasi-solid-state Li–S batteries

Abstract

Quasi-solid-state electrolytes (QSSEs) have attracted significant attention as a promising solution to safety and shuttle-effect issues in lithium-sulfur batteries (LSBs) owing to their high lithium-ion transference numbers (t_Li⁺), which suppress lithium dendrite formation and enhance safety and electrochemical stability. In this study, a binder-free (BF) cathode with a QSSE is fabricated via in situ polymerization of 1,3-dioxolane into poly(1,3-dioxolane) (PDOL). The QSSE serves simultaneously as an electrolyte and a binder. Despite being BF, the electrode exhibits stable electrochemical performance and mechanical strength, even under deformation. The polyvinylidene fluoride (PVDF) cathode shows a lower initial capacity of 885.8 mAh g⁻¹ because the PVDF binder impedes capillary absorption, preventing deep electrolyte infiltration and generating voids that hinder charge transport and reduce coulombic efficiency. The BF cathode achieves 1059.3 mAh g⁻¹ at 0.2C owing to infiltration of polymerized PDOL into the porous structure, enhancing interfacial integration and wettability. This study is the first to employ PDOL as a bifunctional binder–solid polymer electrolyte in LSBs, exploiting its strong adhesion and high lithium-ion conductivity. The BF@QSSE pouch cell is exceptionally flexible and safe under cycling and mechanical abuse, demonstrating the potential of combining BF cathodes with in situ-formed PDOL to fabricate flexible LSBs.