Effect of Sm on performance of Pr/NW/Mg-free and low-cobalt AB4.6 alloys in nickel-metal hydride battery electrode

In this study, Sm-doped Pr/Nd/Mg-free low-cobalt La3.0xCexSm0.98-4xZr0.02Ni3.91Co0.14Mn0.25Al0.30(x = 0.08; 0.12; 0.16; 0.20; 0.245) metal hydride electrodes were synthesized for the first time in the literature, and their structural characteristics and electrochemical performance were investigated. The CaCu5-type main phase and Ce2Ni7-type minor phase were found to coexist in the electrodes via XRD analysis. A large volume of the unit cell with increasing values of x led to a lower desorption plateau pressure, and high thermodynamic stability of the hydride and a maximum discharge capacity of 331.2 mA h g(-1) were obtained at x = 0.245. The HRD 3000 of the electrode alloy exhibited 81.40% at x = 0.245, and this contributed to excellent catalytic performance of the CaCu5-type phase and provided phase boundary layers in the Ce2Ni7-type phase. The retention capacity was maintained at 78.30% at x = 0.12 after 100 cycles owing to the combined effect of Ce and Sm. The mechanisms of the related electrochemical thermodynamics and kinetics were also systematically investigated. (C) 2020 Elsevier B.V. All rights reserved.