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采用XRD的Rietveld全谱拟合技术以及利用储氢合金吸氢量与其体积膨胀成线形关系的原理,研究了Ti-V基贮氢电极合金的电化学吸放氢机理.结果表明,铸态合金Ti0.8Zr0.2V1.867Mn0.373Cr0.56Ni0.7由C14型Laves相和V基固溶体相构成.在充电过程中,充电时间由3.33增至120 min时,Laves相的晶胞体积膨胀率ΔV/V分别由0.301％增加到2.719％,而V基同溶体相的ΔV/V由0.011％增至1.685％.在放电过程中,放电时间从0 min增加到165 min时,Layes相的ΔV/V从14.542％降到8.119％;而V基固溶体相的△V/V从8.117％减小到6.248％.说明电化学吸氢时,氢首先被Laves相吸收,然后再扩散进入V基固溶体;电化学放氢时, V基固溶体中的氢首先扩散进入Laves相然后再释放.因此,该合金中,Laves相既是吸氢相又是催化相,提高合金中V基固溶体相的利用率,从而使Ti-V基贮氢合金具有较好的综合电化学性能.
The mechanism of electrochemical hydrogen storage and desorption of Ti-V-based hydrogen storage electrode alloys was studied by using the Rietveld full-spectrum fitting technique of XRD and the linear relationship between the amount of hydrogen absorbed by the hydrogen storage alloy and its volume expansion. The results show that as-cast alloy Ti0.8Zr0.2V1.867Mn0.373Cr0.56Ni0.7 consists of C14-type Laves phase and V-based solid solution phase during charging, charging time from 3.33 to 120 min, the Laves phase unit cell volume expansion rate ΔV / V increased from 0.301% to 2.719%, respectively, while the VV / V of the V-based isotropic phase increased from 0.011% to 1.685%. During the discharge process, when the discharge time increased from 0 min to 165 min, the ΔV / V From 14.542% to 8.119%, while V / V of the V-based solid solution decreases from 8.117% to 6.248%, indicating that hydrogen is first absorbed by the Laves phase and then diffused into the V-based solid solution during the electrochemical hydrogen absorption When hydrogen is released chemically, the hydrogen in the V-based solid solution first diffuses into the Laves phase and then is released, so that the Laves phase is both a hydrogen-absorbing phase and a catalytic phase to increase the utilization of the V-based solid solution phase in the alloy, Ti-V-based hydrogen storage alloy has good electrochemical properties.