An Energy-Dense and High-Power Li-Cl2 Battery by Reversible Interhalogen Bonds

Abstract Anionic redox reactions would achieve a high capacity than typical transition-metal-oxide cathodes, offering a low-cost chemistry to advance the energy storage capability of lithium-ion batteries. Li-Cl 2 chemistry using anionic redox reactions of Cl 0/−1 shows superior operation voltage (~ 3.8 V) and capacity (756 mAh g − 1 ). However, a redox-active and reversible chlorine cathode has not been developed in organic electrolytes-based lithium-ion batteries. Chlorine ions bonded by ionic bonding hardly dissolve in organic electrolyte, imposing a thermodynamic barrier for redox reactions. Meanwhile, chlorine gas is easily formed during oxidation. Herein, we report an interhalogen compound, iodine trichloride (ICl 3 ), as the cathode to address these two issues. In- situ and ex-situ spectroscopy data and calculations reveal that reduced Cl − ions are partially dissolved in the electrolyte, and oxidized Cl 0 is anchored by forming interhalogen bonds with I. A reversible Li-Cl 2 at room temperature is developed, which delivers a specific capacity of 302 mAh g − 1 at 425 mA g − 1 , and a 73.8% capacity retention at 1250 mA g − 1 . The demonstration of reversible interhalogen bonds enabled rechargeable Li-Cl 2 battery opens a new avenue to develop halogen compound cathodes.