Sulfur cathodes in conversion reaction batteries operate by a different mechanism than that of intercalation materials, and they possess larger theoretical gravimetric capacities. However, sulfur-based electrode materials suffer from parasitic polysulfide shuttling, which contributes to decreased capacity retention and cyclability. We demonstrate that transition metal polysulfide chalcogels achieve high gravimetric capacity as electrode materials for lithium-ion batteries. Transition metal polysulfide chalcogels are amorphous and comprise of polysulfide chains connected by inorganic linkers. The linkers appear to act as a "glue" in the electrode to prevent polysulfide shuttling. The use of an amorphous electrode material avoids the issue of large volume changes between the as-prepared material and intermediate products upon cycling. In particular, we examined 3d and 4d transition metal polysulfide chalcogels (M'M''Sx) and their role in maintaining structural stability in the electrode. In the MoS3.4 case study, the Mo polysulfide chalcogels function as electrodes in carbonate-- as well as ether--based electrolytes and achieve an initial gravimetric capacity of 600 mAh g-1. We employ X-ray absorption spectroscopy and operando pair distribution function techniques to elucidate the structural evolution of the electrode. Raman and X-ray photoelectron spectroscopy track the chemical moieties that arise during the anion-redox-driven processes. We find the redox state of Mo remains unchanged across the electrochemical cycling even to 1 V and correspondingly, the redox is anion-driven. The local Muller-type cluster structure is also maintained upon discharge and charge. Understanding chemical and local structural environment of these chalcogel case studies provides valuable insight into this class of materials as electrode materials for Li-ion batteries.

Transition metal polysulfide chalcogels as electrode materials for Li-ion batteries

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.