The discharge characteristics of the negative electrode alloys for the nickel-metal hydride batteries

In recent years, owing to the rapid development of portable electronic and electrical appliances, including cellular telephones, video cameras, lap-top computers, tape-recorders and hand tools, and electric vehicles, the market for rechargeable batteries is increasing at a high rate. The nickel-metal hydride battery (Ni/MH) is one of the more promising types, because of its high capacity, high-rate charge/discharge capability and non-polluting nature. This type of battery uses a hydrogen storage alloy as its negative electrode. The characteristics of the Ni/MH battery, including discharge voltage, high-rate discharge capability and charge/discharge cycle lifetime are mainly determined by the construction of the negative electrode and the composition of the hydrogen-absorbing alloy. The negative electrode of the Ni/MH battery described in this paper was made from a mixture of hydrogen-absorbing alloy, nickel powder and polytetrafluoroethylene (PTFE). A multicomponent MmNi(5)-based alloy (Mm(0.95)Ti(0.05)Ni(3.85)Co(0.45)Mn(0.35)Al(0.35)) was used for the negative electrode alloy. The discharge characteristics of the negative electrode, including discharge capacity, cycle lifetime and polarization overpotential, were studied by means of the electrochemical experiments and analysis.