Enhancing the activation and cycling properties of V-based alloys by trace Ce doping

This study focused on improving the activation property and cycling stability of V78Ti6Cr16 alloy through trace Ce doping. V78Ti6Cr16Cex (x= 0, 0.2, 0.4) alloys were prepared by arc melting. The activation property, the kinetic and thermodynamic properties, the cycling stability and the cycling stability mechanism of the prepared alloys were investigated. The results show that trace Ce doping significantly improves the activation performance of the alloy. The kinetics changed little and the thermodynamics changed a little by trace Ce doping. Crucially, trace Ce doping remarkably improved cycling stability of the alloy. V78Ti6Cr16Ce0.2 exhibited a capacity retention rate of 97.43% after 400 cycles, substantially higher than the 93.06% of undoped alloy. Even after 1,000 cycles, Even after 1000 cycles, V78Ti6Cr16Ce0.2 maintained higher than 90% retention, demonstrating excellent cycling stability for practical applications. XRD and compressing test reveal that Ce doping effectively improves the crystal structure of the alloys by increasing the cell volume and the enhancing the mechanical properties of the alloy, thereby improving the structure stability of the alloy during cycling. TEM analysis indicated that the defect density progressively increases with cycling in undoped alloy, which is the main reason for the capacity decay. But the defect density is much less in V78Ti6Cr16Ce0.2 alloy compared with undoped alloy, which contributes to its superior capacity retention rate. This work provides a new strategy for enhancing hydrogen storage properties via trace rare-earth doping.