Effect of carbon coating on the electrochemical properties of La–Y–Ni-based hydrogen storage alloys

The A2B7-type (LaSmY) (NiMnAl)3.5 alloys were prepared by induction melting, and then the alloy samples coated with different contents of nano-carbon were prepared by the mixing and sintering method using pitch as carbon source. The effects of the contents and structure of the coated-carbon on the electrochemical properties of alloy samples were investigated. With the carbon content increase from 0.1 to 1.0 wt%, the cyclic stability is improved and the high-rate dischargeabilitiy (HRD) of the alloy electrodes first increase and then decrease. The kinetic results show that the carbon coating improves the electrocatalytic activity and electrical conductivity of the alloy electrodes. The alloy electrode with 0.5 wt% carbon coating exhibits the best electrochemical properties. The maximum discharge capacity (Cmax) is 345.7 mAh·g−1, the HRD1200 is 72.49%, and the capacity retention rate (S300) is 79.44%.