Spinel Li4Mn5O12 as 2.0 V Insertion Materials for Mg-Based Hybrid Ion Batteries

With the increasing demand for electrical energy storage, a new Mg-Li hybrid battery with Mg anode is regarded as a promising candidate because of low cost, high volumetric capacity, and dendrite-free nature of the Mg anode. Nevertheless, the characteristics of low operation voltage and low energy density for Mg-Li hybrid batteries hinders their widespread application, owing to limited reversible cathodes. To overcome these issues, a highly reversible fast Li+ insertion cathode with high voltage is an effective strategy to realize high-energy-density Mg-Li hybrid batteries. Herein, we develop the 2 V high-voltage spinel Li4Mn5O12 cathode material with unique nano-/microspheres, using a novel low-temperature method, offering a short Li-diffusion path and sufficient transport channels for electrolyte penetration into the electrode. For the first time, we demonstrate the feasibility of the spinel Li4Mn5O12 nano-/microspheres with hierarchical architecture as a cathode for 2 V hybrid Mg-Li batteries. It exhibits a reversible specific capacity of 155 mAh g(-1) and a long discharge voltage platform exceeding 2.0 V (vs. Mg/Mg2+) coupled with high energy density of 326 Wh kg(-1) at a current density of 0.1 C (1 C=163 mA g(-1)). Our results pave the way of constructing new hybrid Mg-Li batteries with high voltage and high energy density.