Electrochemical Realization of 3D Interconnected MoS₃/PPy Nanowire Frameworks as Sulfur-Equivalent Cathode Materials for Li-S Batteries

The development of freestanding and binder-free electrode is an effective approach to perform the inherent capacity of active materials and promote the mechanism study by minimizing the interference from additives. Herein, we construct a freestanding cathode composed of MoS₃/PPy nanowires (NWs) deposited on porous nickel foam (NF) (MoS₃/PPy/NF) through electrochemical methods, which can work efficiently as sulfur-equivalent cathode material for Li-S batteries. The structural stability of the MoS₃/PPy/NF cathode is greatly enhanced due to its significant tolerance to the volume expansion of MoS₃ during the lithiation process, which we ascribe to the flexible 3D framework of PPy NWs, leading to superior cycling performance compared to the bulk-MoS₃/NF reference. Eliminating the interference of binder and carbon additives, the evolution of the chemical and electronic structure of Mo and S species during the discharge/charge was studied by X-ray absorption near-edge spectroscopy (XANES). The formation of lithium polysulfides was excluded as the driving cathode reaction mechanism, suggesting the great potential of MoS₃ as a promising sulfur-equivalent cathode material to evade the shuttle effect for Li-S batteries. The present study successfully demonstrates the importance of structural design of freestanding electrode enhancing the cycling performances and revealing the corresponding mechanisms.