The effect of Ti-doping on the electrochemical activity of the Li$_{0.44}$MnO$_2$ cathode material for Li-ion batteries

Manganese-based oxides can function as economical cathode materials for Li-ion batteries. Various metastable manganese oxides can exhibit efficient Li$^+$ (de)insertion activity. One such system is chemically derived Li$_{0.44}$MnO$_2$ offering reversible Li$^+$ intercalation involving the Mn$^{4+}$/Mn$^{3+}$ redox reaction albeit with poor rate kinetics. In this work, the electrochemical activity of tunnel-structured Li$_{0.44}$MnO$_2$ has been enhanced by tailoring its crystal structure and particle morphology by Ti-doping into Mn sites. X-ray diffraction and spectroscopy analyses revealed successful Ti-doping while retaining the original structure. Varying degrees of Ti-doping were found to exhibit improved electrochemical performance, with Li$_{0.44}$Mn$_{0.89}$Ti$_{0.11}$O$_{2}$ delivering the highest capacity of 129 mAh g$^{-1}$ at a rate of C/20. Ti-doping was further found to improve the Li$^{+}$ diffusivity and rate kinetics. This enhancement in electrochemical activity can be ascribed to the combined effect of Ti-induced lattice expansion and decrease in particle size. Electrochemical titration and ex situ analyses revealed the occurrence of a single-phase (solid-solution) redox mechanism. ... mehrTi-doped Li$_{0.44}$MnO$_{2}$ can be harnessed as an economical cathode for Li-ion batteries.