Abstract

AbstractLithium–sulfur/selenium batteries have attracted broad interest and achieved good performance using ether‐based electrolytes. However, when the ether‐based electrolytes are employed, Li–S/Se battery systems still have several inevitable drawbacks inhibiting their practical applications, such as intermediate product dissolution issues, and a dependency on a high content of electrolyte. Thus, it is urgent to pay attention to the electrochemical properties of SexSy cathodes in carbonate‐based electrolytes, which may avoid the above mentioned problems. In this work, a series of mesoporous carbon/SexSy (CMK‐3/SexSy) composites with covalent Se‐S bonds and different Se/S molar ratios are prepared and their working mechanism in carbonate‐based electrolytes is systematically investigated by combining experimental analysis and theoretical calculations. This work finds that the Se in the CMK‐3/SexSy cathode is beneficial for the transportation of Li+ ions and forms a thin cathode electrolyte interphase (CEI) during the discharge–charge process. Furthermore, S substitution in Se8 molecules can enhance the specific capacity and lower the bond breaking and lithiation energies. The optimal CMK‐3/SexSy cathode delivers outstanding performance with a high reversible capacity of 609 mA h g−1 at 1 A g−1 over 300 cycles.

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