Highly Elastic and Polar Block Polymer Binder Enabling Accommodation of Volume Change and Confinement of Polysulfide for High-Performance Lithium–Sulfur Batteries

Lithium polysulfide (LiPS) shuttling and sulfur volume change causing degradation of electrodes have hindered the practical application of lithium–sulfur batteries. Here, a highly elastic and polar block polymer binder, poly(acrylic acid)-b-((poly(n-butyl acrylate)-co-poly(2,2,3,4,4,4-hexafluorobutyl acrylate))-b-poly(acrylic acid) (PAA-b-(PnBA-co-PHFBA)-b-PAA), was designed and synthesized to both accommodate sulfur volume change and confine LiPSs. The rigid–soft modulated triblock polymer combined the traditional polar binder PAA, low glass-temperature PnBA, and high-polarity PHFBA. The resultant binder can not only adjust the striking volume expansion and inhibit disintegration of a pure sulfur cathode but also strongly anchor LiPSs. The cycle stability and rate performance of lithium–sulfur batteries were significantly improved after being incorporated with the multifunctional binder. Besides, abundant F atoms can enhance ionic conductivity to improve electrochemical reaction of the sulfur cathode. This work offers a feasible and effective strategy for designing an efficient multifunctional binder toward building next-generation high energy density lithium–sulfur batteries.