(217dp) Electrochemical Synthesis of NdNi5 Hydrogen Storage Alloy

Hydrogen storage alloy has focused on the energy storage materials of rechargeable batteries for application to many electric vehicles (EVs). Especially NdNi₅ alloys have received much attention for the hydrogen storage materials because of the high hydrogen storage capacity. The conventional method for the alloy preparation has a complicated metallurgical process since each oxide should be reduced to its metal beforehand, and then the two metals react to form the alloys. Especially the production process of rare earth (RE) metals has many disadvantages such as high production cost and low energy efficiency. However, the electrochemical reduction method of an oxide mixture in molten salt is relatively simple than the conventional process. This process brings about high productivity and lower energy-consumption. In the present work, an electrochemical synthesis of NdNi₅ hydrogen storage alloy has been studied in LiCl molten salt. In order to conduct electrolysis of mixed oxide, a pellet of mixed oxide and a graphite rod were used as cathode and anode, respectively. The crystalline structure of the reduced samples and the surface morphology were observed with X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. When 200% of the theoretical charges pass though the electrolysis cell, the NiNi₅ alloy was successfully prepared as confirmed by the XRD and EDS analysis. The NdNi₅ alloy with 1,600 ppm oxygen content was successfully synthesized with 50% current efficiency within 1 h in the condition of 3.2 V of cell voltage at 750 °C.