Hydrogen Storage Alloy Negative Electrode Kinetic Performance

The effect of charge/discharge rate, shaping processing and environmental temperature on the kinetic properties of the hydrogen storage alloy was investigated. The additions of Ni powder or C03M0 powder, which possess high electrocatalytic activity, display a great influence on the kinetics characteristics of the metal hydride. The activation rate and the discharge capacity of the hydrogen storage alloy are correlated with activation current.The influences of Co and B element on the kinetics properties of the alloy were studied. The addition of B greatly improves the high-rate dischargeability, whereas it reduces the electrochemical capacity of the alloy. The cyclic stability is improved greatly with the increase of Co content, however, activation rate and the high rate capability decrease.The performance of the hydrogen storage alloy depends on the casting conditions in addition to alloy composition. Compared with the vacuum induction melting alloy, atomized alloy has excellent low-temperature discharge characteristics, which would be ascribed to the very fine crystal grain size and the existence of large quantities of the grain boundaries, because the grain boundaries could work as a fast path for hydrogen diffusion. The rapidly solidified alloy prepared by melt-spinning method showed better cycling stability than the as-cast alloy, while the kinetics characteristics were rather poor.The surface structure and composition of hydrogen storage alloy is very important for its electrochemical performance. The effect of electroless plated Ni coating, hydrazine (N₂H₄ ) solutiontreatment and sodium hypophosphate (NaH2P02) solution treatment on the electrochemical properties of MlNi3.eCoo.7Mno.3Alo.3, MlNi3.7Coo.72Mno.32Alo.31, MlNi3.55Co0.75Mn0.4Alo.2 alloys was investigated. The results indicate that the cyclic life of the alloy was improved by Ni coating. Hydrazine solution treatment and NaH2P02 solution treatment can increase the activation rate and discharge capacity of the alloy. The treated alloy has initial discharge capacity Co before charging. The higher the concentration of the reducing agent, the larger the initial capacity Co.