High temperature phase transformation and low temperature electrochemical properties of La1.9Y4.1Ni20.8Mn0.2Al H2-storage alloy

Metal hydrides can theoretically store H2 at extremely low temperatures in anodic nickel-metal hydride batteries (Ni-MHBs). However, the evolution kinetics of H2 was retarded at low temperatures and the H2-storing capacity of the battery was reduced. Annealing temperature was hypothesized to be the key to regulate the phase composition and therefore, improve the electrochemical kinetics and performance in cold operating conditions. A new-type of La1.9Y4.1Ni20.8Mn0.2Al H2-storage alloy was prepared and annealed at 1098, 1148, 1223 and 1323 K. At the annealing temperature of 1148 K, the alloy exhibited various crystalline structures and H2 channel modifications, a high H2 desorption plateau, resistance to oxidation/corrosion and favourable kinetic characteristics. All the measurements was performed at a temperature of 243 K, resulting in a maximum discharge specific capacity of 298.6 mAh g−1, low-temperature discharge rate of 80.5%, and high-rate dischargeability of 62.8% at a current density of up to 300 mA g−1.