Effect of duplex surface treatment on electrochemical properties of AB3-type La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 hydrogen storage alloy

A new surface treatment technique, i.e. HF etching-Ni coating duplex surface treatment was applied to modify AB(3)-type La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 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 10, 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. (c) 2009 Elsevier B.V. All rights reserved.