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

[Image: see text] 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%.