Electrochemical performances of a Co-free La(NiMnAlFe)_5 hydrogen storage alloy modified by surface coating with Cu

摘要

A new Cu coating technique is adopted for a Co-free alloy La(NiMnAlFe)s to improve its electrochemical properties. Compared with unmodified alloy, the Cu-coated alloys show improved electrochemical performances. The activation number decreased from 19 to 3 cycles and discharge capacity increased from 282 to 307 mAh/g. The optimal high rate discharge ability (HRD) is 25.4 percent (1200 mA/g) for the sample with 5 wt. percent Cu. EIS reveals that decreased charge-transfer resistances and cyclic voltammograms show the higher anodic current peaks, which indicate the high electronic conductivity and electrochemical activity of alloys after Cu coating. The hydrogen diffusion coefficient increases accordingly and the cycle life is also improved.