The cycle life of 50/50 TiFe alloy electrodes for charge storage

The evolution of charge capacity with cycle number into 50/50 TiFe intermetallic compound (IMC) has been investigated. It has been found that in lithiated KOH electrolyte the passivation of a TiFe pressed powder electrode is slowed but not eliminated. Mechanical mixing of the IMC with minor amounts of Ni powder results in better cycle life, probably due to the reduction of passivating oxides, electrocatalytically induced by finely divided Ni. However the best improvement of cycle life was obtained from TiFe+Fe composite electrodes. Although the main charge storage route is again hydrogen insertion into TiFe, the onset of passivation of the IMC is significantly delayed by the presence of Fe.