Effect of Cr and Mo doping on the electrochemical properties of freeze-dried LiCoO2

In this study, LiCoO2 is doped with 2 mol.% Cr and Mo in order to determine the effect of these elements on the electrochemical performance. Precursors are synthesized by means of freeze drying. Calcination is applied at 750 degrees C for 24 h. Doping content and calcination temperature as well as duration are very important for producing impurity-free layered LiCoO2. If the doping content is larger than 2 mol.% or when the calcination temperature is decreased to 550 degrees C, impurity phases are seen. As a result, the sample doped with 2 mol.% Cr has better high charge and discharge rate capability, and cycleability, but discharge capacity is slightly lowered when compared to the undoped sample. Electrochemical impedance spectroscopy results show that surface film resistances of Cr-doped samples are lower than that of the undoped sample.