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

Abstract

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 (TBAI<inf>3</inf>) 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<inf>I</inf> (265 mAh g⁻¹<inf>electrode</inf>, based on entire mass loading) and record-high energy density of up to 2013 Wh kg⁻¹<inf>I</inf> (845 Wh kg⁻¹<inf>electrode</inf>). 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.