Natural okra gum as functional binder enables highly stable Lithium–Selenium batteries

Abstract

Lithium–selenium (Li–Se) batteries are garnered significant attention due to their high theoretical specific capacity, high volumetric energy density and moderate output voltage. Nevertheless, Li–Se batteries are still restricted by severe volume expansion and “shuttle effect” of polyselenides, resulting in deteriorated electrochemical performance. Binders are a crucial component of Li–Se batteries, playing a key role in addressing the mentioned issues. Herein, a non-toxic, bio-friendly, hydro-soluble binder of okra gum (OG) extracted from okra pods is proposed to ameliorate the electrochemical performance of Li–Se batteries. The as-prepared OG binders are rich in branched-chain polysaccharides (glucoside) and polar functional groups (–C–O–C–, –COOH), which not only have a good interpenetrating binding network to ensure the mechanical stability of Se cathode, but also have excellent interfacial chemical binding force for immobilizing polyselenides. Consequently, the OG binder endows Li–Se batteries with high initial discharge capacity (607 mA h g−1 at 0.2C), good cycling stability (218 mA h g−1 after 100 cycles at 0.2C), and remarkable rate performance (364 mA h g−1 at 1C), all of which are superior to Li–Se batteries with PVDF binder. Our study demonstrates the feasibility of natural mucilage as functional binder for Li–Se batteries and paves a research path in developing natural plant-based binders to stabilize electrode materials for reliable high-energy batteries.