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-Cl2 chemistry using anionic redox reactions of Cl0/−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 (ICl3), 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 Cl0 is anchored by forming interhalogen bonds. A reversible Li-Cl2 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.