A study on crystal structure and chemical state of TiCrVMn hydrogen storage alloys during hydrogen absorption-desorption cycling

The evolution of crystal structure and chemical state of the V-based hydrogen storage alloy (Ti0.32Cr0.46V0.22)96Mn4 during hydrogen absorption/desorption cycling was examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Reasons for the degradation in cycling capacity of the alloy are presented and discussed. One reason is the continuous reduction of the V-based cell volume during cycling, which cannot hold further hydrogen atoms. The decrease in cycling capacity can also be attributed to the oxidation of Ti, V, and Cr elements during cycling.