High-Energy-Density Rechargeable Lithium–Nickel Chloride Aqueous Solution Batteries

High-energy-density rechargeable batteries with performance beyond that of lithium-ion batteries are required for next-generation electric vehicles. We propose a novel rechargeable battery with a lithium anode and a NiCl 2 aqueous cathode that is separated Li 1.4 Al 0.4 Ge 0.2 Ti 1.4 (PO 4 ) 3 as a water-stable lithium-ion-conducting solid electrolyte. The cell was discharged up to 93% of the theoretical cathode capacity at 0.5 mA cm -2 and 25 °C. The calculated energy density, based on the weights of NiCl 2 and Li, and the average discharge voltage of 2.4 V at 0.5 mA cm -2 , was 852 Wh kg -1 , which is more than twice as high as that of conventional lithium-ion batteries. The cell was successfully cycled for 50 cycles without any degradation of the charge and discharge voltages at 0.5 mA cm -2 and 25 °C for 5 h charge and 5 h discharge, where the utilization of NiCl 2 was 80%.