Organosulfur Cathodes with High Compatibility in Carbonate Ester Electrolytes for Long Cycle Lithium–Sulfur Batteries

Abstract

Lithium-sulfur batteries (LSBs) are potential candidates for high energy storage technologies due to their theoretical gravimetric energy density of ∼2600 Wh kg-1 and lightweight electrodes. In LSBs, ether electrolytes are frequently utilized because sulfur cathodes and the polysulfide redox intermediate species are chemically stable. However, LSBs in ether electrolytes suffer from the dissolution of higher-order polysulfides, and migration of the soluble polysulfides into electrolytes causes the polysulfide shuttle effect. The shuttle polysulfides react with the lithium anode and give rise to the irreversible deposition of lithium sulfides, deteriorate the morphology of the anode, and cause rapid capacity fading. Moreover, ether electrolytes are highly flammable and trigger safety issues. As an alternative, carbonate ester electrolytes are promising choices to substitute ether electrolytes in LSBs. Organic carbonate electrolytes used in LSBs result in irreversible reactions with long-chain polysulfide anions that cause the cell to shut down. Therefore, carbonate ester electrolytes compatible sulfur cathodes design needs special attention. Sulfurized polyacrylonitrile (SPAN) and short-chain sulfur cathodes are compatible with organic carbonate electrolytes. However, the sulfur contents in these cathodes are mostly below 50 wt% which hamper the practical application of the LSBs. Here, we designed an organosulfur cathode with a high chemical bonded sulfur content of ~58 wt% in the cathode composite. The prepared organosulfur cathode showed excellent compatibility with carbonate ester electrolytes. The organosulfur cathode exhibits a high initial discharge capacity of 1301 mAh g-1 and long cycle stability for 400 cycles with nearly 99.99% coulombic efficiency.