Selenium-Doped Cathodes for Lithium-Organosulfur Batteries with Greatly Improved Volumetric Capacity and Coulombic Efficiency.

Abstract

For the first time a new strategy is reported to improve the volumetric capacity and Coulombic efficiency by selenium doping for lithium-organosulfur batteries. Selenium-doped cathodes with four sulfur atoms and one selenium atom (as the doped heteroatom) in the confined structure are designed and synthesized; this structure exhibits greatly improved volumetric/areal capacities, and a Coulombic efficiency of almost 100% for highly stable lithium-organosulfur batteries. The doping of Se significantly enhances the electronic conductivity of battery electrodes by a factor of 6.2 compared to pure sulfur electrodes, and completely restricts the production of long-chain lithium polysulfides. This allows achievement of a high gravimetric capacity of 700 mAh g^-1 close to its theoretical mass capacity, an exceptional volumetric capacity of 2457 mAh cm^-3 , and excellent capacity retention of 92% after 400 cycles. Shuttle effect is efficiently weakened since no long-chain polysulfides are detected from in situ UV/vis results throughout the entire cycling process arising from selenium doping, which is theoretically confirmed by density functional theory calculations.