Electrochemical performance of compounds Gd 6Mn 23− xNi x ( x = 0–1.4)

Abstract

Alloys with composition Gd 6Mn 23− x Ni x ( x = 0, 0.4, 1.0, 1.2 and 1.4) are prepared and examined by X-ray diffraction technique. The Gd 6Mn 23− x Ni x ( x = 0, 0.4, 1.0, 1.2 and 1.4) compounds crystallize in cubic Th 6Mn 23-type structure with space group F m 3 ¯ m (No. 225). The electrochemical properties of these alloys such as discharge capacity, cycling performance and high rate dischargeability are investigated by battery testing instruments in alkaline electrolyte. The discharge capacity after activation of the Gd 6Mn 23 alloy is about 520 mAh/g at a discharge current density 50 mA/g. Substitution of small amounts of Ni for Mn in Gd 6Mn 23− x Ni x improves the activation, discharge capacity, cycle life, cycle stability and the kinetics of hydrogen absorption–desorption processes at different discharge rates. Most of the Ni substituted alloys were found to possess an exceptional electrochemical performance, while the alloy with x = 0.4 (Gd 6Mn 22.6Ni 0.4) has an exceptional discharge capacity and plateau pressure at discharge current density 200 mA/g and the alloy with x = 1.0 (Gd 6Mn 22Ni) has an exceptional cycle stability and HRD.