Synthesis of Ternary Metal Oxide as a Positive Electrode for Mg-Li Hybrid Ion Batteries

Rechargeable magnesium-ion battery (MIB) has emerged as an exciting energy storage system owing to highly stable magnesiation and de-magnesiation process and high theoratical energy density. However, MIB technology is restricted by sluggish Mg2+ ion transportation inside the host cathode due to large impedance. Herein, a rechargeable Mg-Li hybrid ion battery (MLIB) is presented to achieve fast Mg2+ ion stripping/plating at magnesium anode and Li+ ion intercalation/de-intercalation in a ternary transition metal oxide cathode. The (NiMnCo)3O4 multi-shelled hollow spheres prepared by one-step hydrothermal method followed by thermal treatment, was employed as a positive electrode in Mg-Li hybrid ion battery, with magnesium metal anode and all-phenyl-complex based dual ion electrolytes. The resulted prototype MLIB delivered a reversible capacity of 550 mAhg-1 at a current density of 50 mAg-1, which is signifcantly highesr compared with reported MLIBs. Furthermore, the prototype MLIB exhibited an affordable specific energy (368 Whkg-1) and cycle life (capacity of 277 mAhg-1 was retained even after 100 cycles at 100 mAg-1). The significant improvement in electrochemical performance of MLIB is achieved via rational design of (NiMnCo)3O4 cathode with reduced Li+ ion diffusion length and stable deposition/dissolution of Mg at anode without occurance of side reactions. Furthermore, ex-situ XRD, SEM, ICP and EIS techniques were used to understand the reaction kinetics of guest ions inside the (NiMnCo)3O4 hollow sphere cathode.