CATALYST DEVELOPMENT FOR POLYSULFIDE CONVERSION REACTIONS IN LITHIUM-SULFUR BATTERIES

Abstract

This thesis is focused on the development of high activity catalysts to overcome the loss of electrochemically active sulfur (as polysulfides) in rechargeable lithium-sulfur batteries. The approach adopted was modifications of known polysulfide catalysts rather than the design of new catalysts. We first examined the catalytic activity of sulfur deficiencies in MoS2, a simple catalyst modification method with theoretical advantages, and then tested the general utility of this catalyst modification method on another transition metal sulfide (Co9S8). The effectiveness of heteroatom doping was also evaluated. Since transition metal oxides have been successfully used as a polysulfide adsorbent in Li-S batteries, we deem it meaningful to also determine their intrinsic catalytic activity in the polysulfide conversion reaction. For this part of the work we used WO3 as the representative non-transition metal sulfide catalyst; and evaluated the effect of oxygen deficiency in polysulfide conversion.