Effects of Addition of Carbon Nanotubes on Properties of MmMn_(0.4)Co_(0.7)Al_(0.3)Ni_(3.4) Hydrogen Storage Electrode

The electrochemical properties of MmMn0.4Co0.7Al0.3Ni3.4 hydrogen storage electrode with CNTs and Ni additives were invesitigated. The results show that the addition of CNTs in the alloys improves the discharge capacity and initially activation performance. The alloy electrodes with CNTs, CNTs+Ni additives can be completely activated after 11 charge-discharge cycles with maximum capacity of 255.1 and 270.5 mAh/g, respectively. However, activation process of the electrode containing Ni powder needs 24 cycles and the maximum capacity is 245.0 mAh/g accordingly. And also, the addition of CNTs, CNTs+Ni in the alloys modifies the high-rate dis-chargeability(HRD) performance and reveals the higher discharge voltage. The HRD of electrodes with CNTs, CNTs+Ni, Ni and without any additives are 80.5%, 83.9%, 66.9% and 62.4% at the discharge current of 1000 mAh/g, respectively. From their kinetics analysis of linear polarization curve and electrochemical impedance spectroscopy, the addition of CNTs in the alloys decreases the ohmic resistance and improves the rate of charge transfer reaction on the surface, and contributes to the discharge under the high current conditions.