Ionic conductivity promotion of polymer electrolyte with ionic liquid grafted oxides for all-solid-state lithium–sulfur batteries

Abstract

Recently, great attention has been paid to all-solid-state lithium–sulfur (Li–S) batteries for their high energy density and security. But large-scale application of this technology is hindered by the poor ionic conductivity of solid-state electrolytes and high interfacial resistance at ambient temperature. In addition, seeking an appropriate carbon matrix for solid-state Li–S batteries is challenging. Herein, with the purpose of addressing these problems, N-doped carbon nanosheets (N-CNs) as a matrix for optimizing a sulfur cathode was successfully prepared. Furthermore, we fabricated innovative poly(ethylene oxide) (PEO)-based solid-state polymer electrolytes (SSPEs) containing ionic liquid grafted oxide nanoparticles (IL@NPs), which showed high ionic conductivity at low temperatures. Additionally, the differences among IL@NPs based on ZrO₂, TiO₂, and SiO₂ are compared. The electrolyte with IL@ZrO₂ showed the highest ionic conductivity of 4.95 × 10⁻⁴, 2.32 × 10⁻⁴ S cm⁻¹ at 50 and 37 °C, respectively. With advanced and innovative designs in both cathode and electrolyte, our solid-state Li–S battery exhibits improved electrochemical performance. The battery with SSPEs based on IL@ZrO₂ delivered a high specific capacity of 986, 600 mA h g⁻¹ at 50 and 37 °C, respectively. It's believed that this strategy, using IL@NPs added SSPEs and the N-CNs/S cathode, may shed light on prospective applications with all-solid-state Li–S batteries.