In situ formation of an intimate solid-solid interface by reaction between MgH2 and Ti to stabilize metal hydride anode with high active material content

Abstract

MgH₂ and TiH₂ have been extensively studied as potential anode materials due to their high theoretical specific capacities of 2036 and 1024 mAh/g, respectively. However, the large volume changes that these compounds undergo during cycling affects their performance and limits practical applications. The present work demonstrates a novel approach to limiting the volume changes of active materials. This effect is based on mechanical support from an intimate interface generated in situ via the reaction between MgH₂ and Ti within the electrode prior to lithiation to form Mg and TiH₂. The resulting Mg can be transformed back to MgH₂ by reaction with LiH during delithiation. In addition, the TiH₂ improves the reaction kinetics of MgH₂ and enhances electrochemical performance. The intimate interface produced in this manner is found to improve the electrochemical properties of a MgH₂-Ti-LiH electrode. An exceptional reversible capacity of 800 mAh/g is observed even after 200 cycles with a high current density of 1 mA/cm² and a high proportion of active material (90 wt.%) at an operation temperature of 120 °C. This study therefore showcases a new means of improving the performance of electrodes by limiting the volume changes of active materials.