Exploration of Spinel LiCrTiO₄ as Cathode Material for Rechargeable Mg-Li Hybrid Batteries

Mg-Li hybrid batteries have attracted wide interest in recent years because of their potential safety as well as their cost benefit and high volumetric capacity. However, slow kinetic properties strongly hinder their commercial application. In this study, we have prepared spinel LiCrTiO₄ by a solid-state reaction and have conducted a comprehensive study aimed at improving the performance of Mg-Li hybrid batteries by optimizing the dual-salt electrolyte. LiCrTiO₄ has been found to show reversible discharge/charge capacities of 178 and 169 mA h g^-1 in electrolytes of 1 m LiCl and 0.3 m APC (all-phenyl-complex), respectively. When the concentration of APC was increased to 0.4 m, LiCrTiO₄ showed a high capacity retention of 95 % after 30 cycles. In addition, no phase transition could be observed for an LiCrTiO₄ electrode in a dual-salt system, suggesting high electrochemical reversibility. Ex situ EDX and SEM studies have indicated that only Li⁺ ions are inserted into the cathode side, while Mg²⁺ ions are reversibly deposited on the surface of Mg metal without dendrite-like growth, indicative of good safety of the Mg-Li hybrid batteries.