Three-Electron Transfer-Based High-Capacity Organic Lithium-Iodine (Chlorine) Batteries

Conversion-type batteries apply the principle that more charge transfer is preferable. The underutilized electron transfer mode within two undermines the electrochemical performance of halogen batteries. Here, we realised a three-electron transfer lithium-halogen battery based on I^- /I⁺ and Cl^- /Cl⁰ couples by using a common commercial electrolyte saturated with Cl^- anions. The resulting Li||tetrabutylammonium triiodide (TBAI₃ ) cell exhibits three distinct discharging plateaus at 2.97, 3.40, and 3.85 V. Moreover, it has a high capacity of 631 mAh g^-1 _I (265 mAh g^-1 _electrode , based on entire mass loading) and record-high energy density of up to 2013 Wh kg^-1 _I (845 Wh kg^-1 _electrode ). To support these findings, experimental characterisations and density functional theory calculations were conducted to elucidate the redox chemistry involved in this novel interhalogen strategy. We believe our paradigm presented here has a foreseeable inspiring effect on other halogen batteries for high-energy-density pursuit.