Surface Modification and Electrochemical Performance of Al₂O₃ Coated and Ni-Doped Spinel LiMn₂O₄ for Aqueous Rechargeable Battery Applications

This work reports the synthesis and electrochemical performance of the nickel-doped lithium manganese oxide along with the surface modification of the mentioned oxide coated with the aluminum oxide via a solid state route. The structural and functional groups were confirmed by the X-ray powder diffraction and Raman spectroscopy studies, respectively. A pyramid-like structure of the pure lithium manganese oxide and a plate-like structure of lithium manganese nickel oxide coated by Al₂O₃ were confirmed by the field emission scanning electron microscopy. The exchange current density and the charge transfer resistance were calculated via electrochemical impedance spectroscopy in an aqueous electrolyte system. In that system, the electrochemical behaviour of the lithium manganese oxide, of the lithium manganese nickel oxide, and of the Al₂O₃ coated lithium manganese nickel oxide was studied by the charge/discharge analysis. The Al₂O₃ coated lithium manganese nickel oxide exhibits 91% capacity retention up to 100 charge/discharge cycles as well as a lower charge transfer resistance which are far better than previously reported values.