A Poly(Ionic Liquid)‐Based Polymer Binder for Endurable Lithium–Sulfur Batteries

Abstract

Though polyvinylidene fluoride (PVDF) is widely‐used binder for conventional lithium‐sulfur (Li–S) batteries, it still encounters challenges of severe electrode fracture involved by drastic volume change upon repeating cycling, and lack of extended‐functions like trapping dissolved polysulfides and smoothing Li+ transfer. Herein, a methodology of grafting sulfophilic hydrogen‐bond donor and lithiophilic hydrogen‐bond acceptor to the polymer binder (named as PIL), function as gear teethes and tooth spaces, is reported. When cracks occur, the engaged gears driven by dynamic hydrogen bonds are separated, which are spontaneously reformed owing to the automatic meshing of gears, and thus accelerate the healing of cracks. At the molecular level, the synergetic effect of sulfophilic hydrogen‐bond donor and lithiophilic hydrogen‐bond acceptor enables polysulfides immobilization through “push‐pull effect”, facilitating the subsequent redox kinetics. Accordingly, the cross‐link network of hydrogen bonds endows the elaborated designed polymer binder with strong adhesive strength and rapid Li+ migration. Attributed to these beneficial properties, the PIL‐based sulfur cathode exhibits excellent rate performance and superior cycling durability (an ultralow capacity fading rate of 0.062% per cycle over 800 cycles at 2 C). Even with high sulfur loading of 9.27 mg cm−2, a high areal capacity of 8.71 mAh cm−2 can be achieved, verifying its potential application.