Development of an energy-dense and high-power Li-Cl2 battery using reversible interhalogen bonds

Anionic redox reactions would achieve a higher capacity than typical transition-metal-oxide cathodes, offering low-cost chemistry for advanced 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 electrolyte-based lithium-ion batteries. Chlorine ions bonded by ionic bonding hardly dissolve in organic electrolytes, 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. A reversible Li-Cl 2 delivers a specific capacity of 302 mAh g −1 at 425 mA g −1 and a 73.8% capacity retention at 1,250 mA g −1 .