Switchable nucleophile-electrophile chemistry enables functional four-electron Li-I2 batteries

Abstract Four-electron iodine redox chemistry offers a high theoretical specific energy of ~1324 Wh kgI −1 , yet its practical realization is fundamentally limited by the conflicting demands of rapid I 0 /I + oxidation, effective suppression of iodine shuttling, and stabilization of highly reactive I + species. Here we report a redox-active, Lewis acid/base-tunable phthalimide that resolves these constraints through a single-molecule polarity-switching mechanism. Upon electrochemical oxidation, electrophilic phthalimide δ+ strongly interacts with nucleophilic iodine and polyiodide species, concurrently suppressing polyiodide shuttling and promoting their conversion to I + . The consecutively generated phthalimide δ− acts as a nucleophilic stabilizer for the resulting I + species. This electrochemically driven polarity switching of phthalimide enables flexible four-electron Li-I 2 pouch cells that deliver ~400 mAh gI −1 capacity, a specific energy exceeding 1200 Wh kgI −1 , a high cathode-level specific energy ( ~ 883.4 Wh kg(cathode) −1 ), and stable cycling over 1000 cycles. The successful integration of these cells into wearable wireless charging and motion-sensing systems demonstrates the potential of polarity-switchable iodine chemistry for next-generation flexible energy-storage devices.