Influence of Temperature on Self-Discharge and High-Rate Discharge Characteristics of La-Rich AB5-Based MH Alloy Electrode

The influence of temperature on self-discharge and high-rate discharge characteristics of MmNi3.65(CoAlMn)1.35 alloy electrode has been investigated by way of simulated battery tests. Self-discharge behaviors of the MH electrode were measured using two methods: continuous mode self-discharge and step mode self-discharge. The results indicate that both reversible and irreversible capacity loss of MH electrode are mainly affected by temperature and storage time. When tested at 323K, the gross capacity loss after storage for 4 days is 30.88%, 15.02% at 273K and 20.09% at 303K, respectively. SEM analysis has shown that some needle corrosion products are formed on the surface of MH electrode, especially following storage at high temperature. The efficiency of high-rate discharge process is related closely to its discharge current density (DCD) adopted in tests, discharged capacities decreased with increasing DCD, and the electrode performed good high-rate discharge behavior at 303 K. Cyclic voltammetry (CV) analysis has indicated that near linear relationships between Ip and Scan rate (v) have been observed in the three temperature cases. The calculated values of hydrogen diffusion coefficient (D) within the electrode, are 1.479×10-8 cm2 / s at 273K, 2.437×10-8 cm2 / s at 303K, and 3.156×10-8 cm2 / s at 323K, respectively.