Inhibition of LaNi5 electrode decay in alkaline medium by electroless encapsulation of active powder particles

Surface of powdered LaNi5 intermetallic compound has been modified by active particle coverage with electroless nickel (Ni-P). The electrode degradation process in 6 M KOH solution has been tested across 70 charge/discharge cycles at -0.5 C/+0.5 C rates. It has been established that after approx. 25-35 initial cycles, the electrode degradation process fulfills first order chemical reaction kinetics law: logarithm of discharge capacity linearly decreases with cycle number. The rate constant for the Ni-P protected material is over 20 % lower than that of as received one. The surface modification also improves the alloy hydrogenation kinetics: exchange current densities of H2O/H-2 system are generally greater for modified material and, contrary to uncovered material, do not practically decrease with long-lasting cycling.