A high-resilience and conductive composite binder for lithium-sulfur batteries

Binder is very important for the cycle stability of lithium-sulfur batteries under high sulfur loading. In this paper, we designed and prepared a waterborne polyurethane/polyacrylic acid/graphene (WPU/PAA/GN) multi-functional composite binder. The polyoxyethylene segments in WPU are used to promote the migration of lithium ions and provide high elongation. The introduction of polyacrylic acid (PAA) and graphene forms a double hydrogen bond network through simple in situ blending, which gives the binder higher strength and electronic conductivity. More importantly, the physical crosslinking of PAA and WPU can achieve high resilience and ensure the integrity of the cathode structure during charging and discharging. In addition, abundant polar functional groups provide strong chemical adsorption for lithium polysulfide. The synergistic effect of various components makes the binder possess the functions of high resilience, good electrical conductivity, and strong adsorption, which provides a simple and effective solution for the practical application of lithium-sulfur batteries. As a result, the assembled lithium-sulfur battery displayed a high initial discharge capacity of 1243 mAh g−1, good cycle stability (81% capacity retention after 500 cycles at 0.5 C) and superior rate performance.