The effect of synthesis modifications on the lithium cobalt oxide using commercial precursors

Abstract

In this work, the effects of modifications in the synthesis Li/Co/dopant concentrations on the performance and cycle life of lithium cobalt oxide are investigated to learn how different modification methods work in relation to each other and to provide data for up-to-date commercial interest. The LiCoO2 materials are prepared using the same precursors and synthesis process to ensure the comparability. The electrochemical characterizations are performed in both half-cells and LiCoO2/graphite pouch cells. The Mg–Ti doped LiCoO2 shows superior performance compared to stoichiometric and over-lithiated LiCoO2. The Mg–Ti doped sample shows 89% capacity retention after 1000 cycles in 3.0–4.2 V and 80% capacity retention after 240 cycles in 3.0–4.4 V in LiCoO2/graphite pouch cell. The better rate capability is attributed to Ti doping reducing the Co valence in LiCoO2, making it more metallic and conductive. The longer cycle life of the doped LiCoO2, in turn, is attributed to a better structural stability caused mainly by Mg doping. This is also reflected in a smaller increase in the charge transfer impedance during cycling. In contrast, the Li doping increases the material impedance and thus decreases the cycle life of the material.