High-rate discharge characteristics of metal hydride modified by electroless nickel plating based on experimental design approach

In this study, a metal hydride (MH) alloy (MmNi_3.81Mn_0.41Al_0.19Co_0.76) is modified by electroless nickel plating with the controlled variables of plating time (A), temperature (B), amount of MH alloy (C), pH (D), concentration of reducing agent (NaH₂PO₂·H₂O) (E), and complex agent (Na₃C₆H₅O₇·2H₂O) (F). Based on the two-level orthogonal array strategy, the Ni loadings on the modified MH alloy of −20.25–11.83% are strongly affected by the variables of A, D, E, and F, as well as the two-factor interactions of AB, AC, AD, BD, and EF. The utility of the unmodified MH alloy used as the negative electrode material of the Ni–MH battery decreases from 100.6 to 7.6% when increasing the discharge rate from 0.2 to 10 C. The utility at the discharge rate of 10 C can be increased to 54.5% for the MH alloy modified by electroless plating Ni when the plating time, temperature, amount of MH, pH, and concentrations of the reducing agent and complex agent are equal to 10 min, 70 °C, 2 g, 7.0, 15 g L⁻¹, and 30 g L⁻¹, respectively.