Fluoro-organosulfur catholytes to boost lithium primary battery energy

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-SF(5)) 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-SF(5) 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.