Rational Design of Statically and Dynamically Stable Lithium-Sulfur Batteries with High Sulfur Loading and Low Electrolyte/Sulfur Ratio.

Abstract

The primary challenge with lithium-sulfur battery research is the design of sulfur cathodes that exhibit high electrochemical efficiency and stability while keeping the sulfur content and loading high and the electrolyte/sulfur ratio low. With a systematic investigation, a novel graphene/cotton-carbon cathode is presented here that enables sulfur loading and content as high as 46 mg cm^-2 and 70 wt% with an electrolyte/sulfur ratio of as low as only 5. The graphene/cotton-carbon cathodes deliver peak capacities of 926 and 765 mA h g^-1 , respectively, at C/10 and C/5 rates, which translate into high areal, gravimetric, and volumetric capacities of, respectively, 43 and 35 mA h cm^-2 , 648 and 536 mA h g^-1 , and 1067 and 881 mA h cm^-3 with a stable cyclability. They also exhibit superior cell-storage capability with 95% capacity-retention, a low self-discharge constant of just 0.0012 per day, and stable poststorage cyclability after storing over a long period of six months. This work demonstrates a viable approach to develop lithium-sulfur batteries with practical energy densities exceeding that of lithium-ion batteries.