Influence of Oxygen Content on Microstructure and Electrochemical Properties of V2-xTi0.5Cr0.5NiOx (x=0~0.35) Hydrogen Storage Alloys

摘要:

为了提高V基固溶体贮氢合金的充放电循环稳定性能，研究了O含量对V2-xTi0.5Cr0.5NiOx (x=0~0.35)合金的组织结构和电化学性能的影响。组织结构分析表明，当没有添加O时，合金主要由bcc结构的V基固溶体相和TiNi相组成，随着O含量的增加，合金中出现了Ti4Ni2O新相。电化学测试表明，随着O含量的增加合金电极的最大放电容量有所降低，从x=0时的366.8 mAh/g降低到 x=0.35时的225.3 mAh/g，而较少氧含量时，合金电极的循环稳定性能明显得到了改善，从x=0时的69.9%增大到 x=0.2时的83.7%，而后又降低到76.9%（x=0.35）。电化学动力学分析结果表明，合金的高倍率放电性能，交换电流密度和氢的扩散系数均随着O含量的增加先增加而后减小。

Abstract:

To improve the charge-discharge cycle stability of V-based hydrogen storage alloys, the different contents of oxygen (O) element were introduced into the V2Ti0.5Cr0.5Ni alloy, and the structures and electrochemical properties of the V2-xTi0.5Cr0.5NiOx (x =0~0.35) alloys were investigated. The structural investigations show that the alloys with lower O content mainly consist of a V-based solid solution phase with a bcc structure and a TiNi-based secondary phase, while a new phase Ti4Ni2O is observed for the alloys with higher O content. With increasing of O content, the maximum discharge capacity for the V2-xTi0.5Cr0.5NiOx (x =0~0.35) alloy electrodes decreases from 366.8 mAh/g (x=0) to 225.3 mAh/g (x=0.35), while the cycle stability of the alloy electrodes first increases from 69.9% (x=0) to 83.7% (x=0.2) and then decreases to 76.9% (x=0.35). Moreover, the high rate discharge ability, the exchange current density and the hydrogen diffusion coefficient of the alloys first increase and then decrease with increasing of O content.