Performance enhancement of Li–Se batteries by manipulating redox reactions pathway

Lithium–selenium (Li–Se) batteries are promising high-energy battery systems. However, they suffer from shuttling effects of soluble lithium polyselenide intermediates and poor cycling stability. Herein, we use diphenyl diselenide (DPDSe) as an electrolyte additive to alter the redox reactions of selenium. The Li|Se-DPDSe cell shows the maximum discharge capacity of 643 mAh/g at 0.3 °C in the first few cycles, which is 94.7% of the theoretical specific capacity. After 250 cycles, it still maintains a reversible capacity of 602 mAh/g, possessing 93.6% of the initial capacity with Coulombic efficiency of almost 100%. DPDSe brings a new electrochemical reduction pathway leading to a high discharge voltage plateau. In the charge process, some selenium atoms are integrated into the structure of DPDSe to form diphenyl triselenide which adheres to carbon nanotubes therefore reducing the loss of active material. This study reveals intriguing electrochemical reactions of organoselenides and provides guidance for the optimization of electrolyte for stable Li–Se batteries.