The microstructures and electrochemical behaviors of new AB4 type RE-Ti-Mg-Ni based superlattice negative electrodes

In this study, new AB₄ type superlattice negative electrodes were developed with the elemental composition of La_0.8-xTi_xMg_0.2Ni_3.96 (x = 0–0.5) through a process involving induction melting followed by annealing. A thorough investigation was conducted into the microstructure and electrochemical properties. The XRD analysis shows that the x = 0 alloy contained AB₄ and 3R-A₅B₁₉ phases. After partial substitution of Ti 2H-A₅B₁₉ phase appeared, with Ti₂Ni phase forming when x ≥ 0.3. Ti addition causes a preliminary rise followed by a decline in the quantity of the AB₄ phase, a reduction in the amount of 3R-A₅B₁₉ phase, and a steady increase in the levels of 2H-A₅B₁₉ and Ti₂Ni phases. Electrochemical tests revealed the maximum discharge capacity decreases, while the capacity retention rises. Moreover, the high-rate discharge ability falls as Ti substitution increases. The investigations reveal that the transfer of charge taking place on the alloy's surface significantly influences the kinetic properties of all sample electrodes.