Significant influence of insufficient lithium on electrochemical performance of lithium-rich layered oxide cathodes for lithium ion batteries

With an aim to broaden the understanding of the factors that govern electrochemical performance of lithium-rich layered oxide, the influences of insufficient lithium on reversible capacity, cyclic stability and rate capability of the oxide as cathode of lithium ion battery are investigated in this study. Various concentrations of lithium precursor are introduced to synthesize a target composition Li[Li_0.13Ni_0.30Ni_0.57]O₂, and the resulting products are characterized with inductively coupled plasma spectrum, scanning electron microscope, X-ray diffraction, Raman spectroscopy, and electrochemical measurements. The results indicate that the lithium content in the resulting oxide decreases with reducing the concentration of lithium precursor from 10wt%-excess lithium to stoichiometric lithium, due to insufficient compensation for lithium volatilization during synthesis process at high temperature. However, all these oxides still exhibit typically structural and electrochemical characteristics of lithium-rich layered oxides. Interestingly, with decreasing the Li content in the oxide, its reversible capacity increases due to relatively higher content of active transition-metal ions, while the cyclic stability degrades severely because of structural instability induced by higher content of Mn³⁺ ions and deeper lithium extraction