Greatly Improved Conductivity of Double-Chain Polymer Network Binder for High Sulfur Loading Lithium-Sulfur Batteries with a Low Electrolyte/Sulfur Ratio.

Binders have been considered to play a key role in realizing high-energy-density lithium-sulfur batteries. However, the accompanying problems of limited conductivity and inferior affinity of soluble polysulfide intermediates bring down their comprehensive performance for practical applications. Herein, the synthesis of a novel double-chain polymer network (DCP) binder by polymerizing 4,4'-biphenyldisulfonic acid connected pyrrole monomer onto viscous sodium carboxymethyl cellulose matrix, yielding a primary crystal structure is reported. Consequently, the resulted binder enables superior rate performance from 0.2 C (1326.9 mAh g-1 ) to 4 C (701.4 mAh g-1 ). Moreover, a high sulfur loading of 9.8 mg cm-2 and a low electrolyte/sulfur ratio (5:1, µL mg-1 ) are achieved, exhibiting a high area capacity of 9.2 mAh cm-2 . In situ X-ray diffraction analysis is conducted to monitor the structural modifications of the cathode, confirming the occurrence of sulfur reduction/recrystallization during charge-discharge process. In addition, in situ UV-vis measurements demonstrate that DCP binder impedes the polysulfide migration, thereby giving rise to high capacity retention for 400 cycles.