Phenyl Selenosulfides as Cathode Materials for Rechargeable Lithium Batteries

The Se-Se bond in an organo-diselenide (RSeSeR, R is an organic group) can break in a 2e(-) reduction reaction, but it has limited capacity as a cathode material for rechargeable lithium-ion batteries. To increase its capacity, redox active species (e.g., sulfur) can be added in the middle of the selenium atoms. Herein, phenyl diselenide (PDSe, PhSeSePh) is mixed with sulfur to form two hybrid compounds with 1:1 and 1:2 molar ratios, which almost double and triple the capacity of PDSe, respectively. Theoretical calculations suggest that phenyl selenosulfide (PDSe-S, PhSe-S-SePh) and phenyl selenodisulfide (PDSe-S-2, PhSe-SS-SePh) can form via addition reactions, which is supported by mass spectrometry analysis. The hybrid materials exhibit three highly reversible redox plateaus and enhanced cycling stability due to the reduced solubility of the discharge products. PDSe-S and PDSe-S-2 show initial capacities of 252 and 330 mAh g(-1), respectively, followed by stable cycling performance with a capacity retention of >73% after 200 cycles at C/5 rate. In addition, they show steady rate capabilities. This study reports a novel strategy to increase the electrochemical performance of organo-diselenide by addition of sulfur.