Abstract
Ni-MH Battery used in New Energy Vehicle (NEV) often presents poor electrochemical behaviors under high temperature condition. In view of this gap, this paper explores electrochemical behaviors of such Ni-MH battery that contains rare-earth elements (Y, Er, Tm, Yb, and Lu) oxides at room and high temps, and discusses the impact of rare earth elements on its charge and discharge voltage, discharge efficiency, volt-ampere characteristics and service life. The results show that the rare earth oxides change the electrochemical behaviors of the surface of the Ni-MH battery crystallites, leading to a concurrent increase in both oxygen evolution overpotential and positive electrode charge efficiency. After rare earth oxides are added, the high rate discharge efficiency of Ni-MH batteries at room temperature significantly worsens. When the discharge is greater than 3C, the Ni-MH batteries with Lu element have the lowest discharge efficiency. Ni-MH batteries containing Ni element show the oxygen evolution potential and oxidation/reduction potential difference all increase at room temperature, and the gas evolution amount of batteries containing rare earth oxides when the potentials exceed the range of oxygen evolution peak is far less than that of common Ni-MH batteries. The Ni- MH batteries perform reversely under high temperature vs. normal temperature conditions. The addition if rare earth elements can effectively improve the service life of Ni-MH batteries.
