Three electrolyte high voltage acid–alkaline hybrid rechargeable battery

Performance characteristics of a three electrolyte rechargeable acid–alkaline hybrid battery using a PbO2 positive plate and a nickel metal hydride (NiMHx) negative electrode in separate electrolyte of H2SO4 and KOH were studied. This hybrid battery has three electrolytes in a single cell. A neutral K2SO4 salt solution was placed between the acid and alkaline compartments of the cell, in which a cation exchange membrane and an anion exchange membrane, were employed to separate these three electrolytes. The open circuit voltage of this hybrid cell was found to be 2.64 V in an electrolyte configuration of 1 M H2SO4|0.2 M K2SO4|2 M KOH electrolyte configuration, compared to 1.92 V in the conventional lead-acid cell in 1 M H2SO4 and 1.40 V in a NiMHx cell in 2 M KOH. This hybrid acid–alkaline PbO2/NiMHx battery was shown to operate with a voltage 20% higher than the conventional lead acid battery and 110% higher than nickel–metal hydride battery at 1/3 C discharging rate. The concentrations of the three electrolytes, the dimension of the electrolyte chamber, and other cell/operation parameters with impacts on the hybrid cell performance were investigated.