Enhancing the Efficient Utilization of Li₂S in Lithium–Sulfur Batteries via Functional Additive Diethyldiselenide

Lithium–sulfur batteries hold great promise for energy storage because of their high theoretical capacity, cost-effectiveness, and environmental friendliness. However, their commercialization has been hindered by the low conductivity of the discharge product lithium sulfide (Li2S) and its high oxidation energy barrier, resulting in low sulfur utilization, poor reversibility, and rapid capacity decay. This study investigates the addition of diethyldiselenide (DEDSe) into conventional electrolytes to mitigate Li2S deficiencies. The result demonstrates the breakage of the Se–Se bond in DEDSe and the elongation of the Li–S bond in Li2S. Moreover, DEDSe reduces the oxidation energy barriers and accelerates the oxidation kinetics of Li2S. Quantitative analysis confirms the decrease of irreversible Li2S deposition at the electrode. As a result, batteries with DEDSe contents exhibit excellent electrochemical performance. Specifically, cells with 2.0 wt % DEDSe added show a high initial discharge capacity of 1314.2 mAh g–1 in the high sulfur-loading pouch cell, maintaining 992.5 mAh g–1 after 34 cycles, which is significantly higher than conventional electrolyte cells at 562.7 mAh g–1. This study offers innovative perspectives on addressing practical challenges and improving the cycling stability of lithium–sulfur batteries.