Enhancement of the high-temperature performance of advanced nickel–metal hydride batteries with NaOH electrolyte containing NaBO2

In this paper, an alternative approach to improve the high-temperature performance of nickel–metal hydride (Ni–MH) batteries is proposed by introducing NaOH electrolyte with sodium metaborate (NaBO2) additives. Compared with conventional batteries using KOH electrolyte, the in-house prepared batteries with proposed electrolytes exhibit an enhanced discharge capacity, improved high-rate discharge ability, increased cycle stability and reduced self-discharge rate at an elevated temperature (70 °C). The charge acceptance of these Ni–MH batteries at 70 °C is over 96% at a charge/discharge rate of 1 C. These performance improvements are ascribed to the increased oxygen evolution overpotential, slower oxygen evolution rate and lower electrochemical impedance, as indicated by CV, steady-state polarization measurements and EIS. The results suggest that the proposed approach be an effective way to improve the high-temperature performance of Ni–MH batteries.