Water-Soluble\nTrifunctional Binder for Sulfur Cathodes\nfor Lithium–Sulfur Battery

Abstract

Conventional\npolymer binder in a lithium–sulfur (Li–S)\nbattery, poly­(vinylidene fluoride) (PVDF), suffers from insufficient\nion conductivity, poor polysulfide-trapping ability, weak mechanical\nproperty, and requirement of organic solvents, which significantly\nencumber the industrial application of Li–S battery. Herein,\na water-soluble binder with trifunctions, covalently cross-linked\nquaternary ammonium cationic starch (c-QACS), is developed to confront\nthese issues. Similar to the poly­(ethylene oxide) solid electrolytes,\nthe c-QACS binder remarkably improves Li⁺ ion transfer\ncapacity. The abundant O actives endow the c-QACS binder with admirable\nlithium polysulfide-trapping capability to retard the shuttle effect.\nIn addition, the formed 3D network effectively maintains the electrode\nintegrity during cycling. Benefiting from the above merits, the sulfur\ncathode with the c-QACS binder demonstrates a performance improvement\nof 300 and 150% compared with sulfur cathode with PVDF and bulk QACS\nbinder after 100 cycles at 0.2C.