Emulsion Binders with Multiple Crosslinked Structures for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries suffer a lot from the huge volume change and the shuttle effect. However, conventional poly(vinylidene fluoride) binder has intrinsic drawbacks, such as low ion conductivity, weak polysulfide-trapping ability, poor mechanical properties, and requirement of organic solvents. Herein, we designed a functional emulsion binder with multi crosslinked structure. Such a structure was formed by the covalent crosslinking within and between the emulsion particles, which facilitates the adapting of the volume expansion of sulfur cathode, thereby ensuring the integrity of electrodes. Besides, the polar functional groups endow the binder with strong chemisorption of lithium polysulfide and fast lithium-ion migration ability. Thus, the assembled lithium-sulfur battery displayed a high initial discharge capacity of 1246 mAh·g^(−1) at 0.1 C, and a capacity fading rate of 0.04% per cycle after 500 cycles at 0.5 C. Even at a high sulfur mass loading of 4.8 mg·cm^(−2), a high capacity of 956 mAh·g^(−1) was still obtained at 0.2 C.