Effect of duplex surface treatment on electrochemical properties of AB 3-type La 0.88Mg 0.12Ni 2.95Mn 0.10Co 0.55Al 0.10 hydrogen storage alloy

Abstract

A new surface treatment technique, i.e. HF etching-Ni coating duplex surface treatment was applied to modify AB 3-type La 0.88Mg 0.12Ni 2.95Mn 0.10Co 0.55Al 0.10 hydrogen storage alloy. Surface structure and electrochemical properties were investigated. SEM and EDS indicated that Ni deposited on the alloy surface, forming a porous Ni-rich layer. And thus initial activation ability and kinetics properties of the alloy electrode were improved significantly. The ratio C 1st/ C max increased from 68.0% to 89.3%, the middle discharge voltage is 0.025 V higher, the high rate dischargeability (HRD) was about 10% higher at a current density of 1080–1800 mA g −1, and the cycling stability was improved slightly after duplex surface treatment. In addition, the exchange current density I 0, the limiting current density I L, the oxidation peak current and the peak area of cyclic voltammograms were also increased obviously after the duplex surface treatment.