The effect of carbon–polyaniline hybrid coating on high-temperature electrochemical performance of perovskite-type oxide LaFeO3 for MH–Ni batteries

Abstract

An efficient carbon–polyaniline (PANI)-coated method was applied for perovskite-type oxide LaFeO₃ to enhance its high-temperature electrochemical performance. Transmission electron microscopy (TEM) results reveal that LaFeO₃ particles are evenly coated with carbon and PANI hybrid layers after carbon–PANI treatment. The carbon layers prevent the nanosized LaFeO₃ particles from aggregation and allow the electrolyte to penetrate in every direction inside the particles. The PANI layers also enhance the electrocatalytic activity, facilitating hydrogen protons transferring from the electrolyte to the electrode interface. The cooperation of carbon and PANI hybrid layers results in a significant enhancement of the electrochemical performance at high temperatures. At an elevated temperature (60 °C), the maximum discharge capacity of the LaFeO₃ electrodes remarkably increases from 231 mA h g⁻¹ to 402 mA h g⁻¹ and the high rate dischargeability at a discharge current density of 1500 mA g⁻¹ (HRD₁₅₀₀) increases from 22.7% to 44.3%. Moreover, the hybrid layers mitigate the corrosion of LaFeO₃ electrodes by reducing the loss of active materials in the alkaline electrolyte, leading to increase in the capacity retention rate from 67.1% to 77.6% after 100 cycles (S₁₀₀).