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.

Keywords

• All-solid-state battery
• In situ formation of solid electrolyte
• In situ formed intimate interface
• MgH2 anode