Nanostructured Li<sub>2</sub>S Cathodes for Silicon–Sulfur Batteries
Hamid Mollania, Chaoqi Zhang, Ruifeng Du, Xueqiang Qi, Junshan Li, Sharona Horta, María Ibáñez, Caroline Keller, Pascale Chenevier, Majid Oloomi Buygi, Andreu Cabot
Abstract
Lithium–sulfur batteries are regarded as an advantageous option for meeting the growing demand for high-energy-density storage, but their commercialization relies on solving the current limitations of both sulfur cathodes and lithium metal anodes. In this scenario, the implementation of lithium sulfide (Li 2 S) cathodes compatible with alternative anode materials such as silicon has the potential to alleviate the safety concerns associated with lithium metal. In this direction, here, we report a sulfur cathode based on Li 2 S nanocrystals grown on a catalytic host consisting of CoFeP nanoparticles supported on tubular carbon nitride. Nanosized Li 2 S is incorporated into the host by a scalable liquid infiltration–evaporation method. Theoretical calculations and experimental results demonstrate that the CoFeP–CN composite can boost the polysulfide adsorption/conversion reaction kinetics and strongly reduce the initial overpotential activation barrier by stretching the Li–S bonds of Li 2 S. Besides, the ultrasmall size of the Li 2 S particles in the Li 2 S–CoFeP–CN composite cathode facilitates the initial activation. Overall, the Li 2 S–CoFeP–CN electrodes exhibit a low activation barrier of 2.56 V, a high initial capacity of 991 mA h g Li 2 S –1, and outstanding cyclability with a small fading rate of 0.029% per cycle over 800 cycles. Moreover, Si/Li 2 S full cells are assembled using the nanostructured Li 2 S–CoFeP–CN cathode and a prelithiated anode based on graphite-supported silicon nanowires. These Si/Li 2 S cells demonstrate high initial discharge capacities above 900 mA h g Li 2 S –1 and good cyclability with a capacity fading rate of 0.28% per cycle over 150 cycles.