In situ monitoring of the volume change and cracking of a MgTi hydride electrode

摘要

Metastable MgTi-10 wt% Pd alloy was synthesized by high-energy ball milling and evaluated as metal hydride electrode for Ni-MH batteries. In situ acoustic emission and generated/relaxed force measurements were performed to monitor the particle cracking and volume expansion/contraction of the electrode occurring during electrochemical charge-discharge cycling. On the basis on these measurements, it was shown that the electrochemical hydrogenation of the MgTi alloy occurs first by an irreversible hydroge-nation (corresponding to a charge capacity of 500 mA h g~(-1)) followed by a reversible hydrogenation (resulting in a discharge capacity of 370 mA h g~(-1)). This second step induces MgTi particle cracking and electrode collapse. During the subsequent cycles, a more reversible volume expansion/contraction is observed and the particle cracking becomes progressively less intensive and originates from the hydrogen evolution reaction rather than to the hydrogen absorption reaction.