Fluoro-organosulfur catholytes to boost lithium primary battery energy

H. Gao, A. R. Sevilla, G. M. Hobold, A. M. Melemed, R. Guo, S. C. Jones, and B. M. Gallant
Proceedings of the National Academy of Sciences, 2022, 119, e2121440119
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Abstract

Discovery of new electrochemical redox motifs is essential to expand the design landscape for energy-dense batteries. We report a family of fluorinated reactants based on pentafluorosulfanyl arenes (R-Ph-SF₅) that allow for high electron-transfer numbers (up to 8-e⁻/reactant) by exploiting multiple coupled redox processes, including extensive S–F bond breaking, yielding capacities of 861 mAh·g_reactant⁻¹ and voltages up to ∼2.9 V when used as catholytes in primary Li cells. At a cell level, gravimetric energies of 1,085 Wh·kg⁻¹ are attained at 5 W·kg⁻¹ and moderate temperatures of 50 °C, with 853 Wh·kg⁻¹ delivered at >100 W·kg⁻¹, exceeding all leading primary batteries based on electrode + electrolyte (substack) mass. Voltage compatibility of R-Ph-SF₅ reactants and carbon monofluoride (CF_x) conversion cathodes further enabled investigation of a hybrid battery containing both fluorinated catholyte and cathode. The hybrid cells reach extraordinarily high cell active mass loading (∼80%) and energy (1,195 Wh·kg⁻¹), allowing for significant boosting of substack gravimetric energy of Li−CF_x cells by at least 20% while exhibiting good shelf life and safety characteristics.