Synthesis and electrochemical performance of tetravalent doped LiCoO2 in lithium rechargeable cells

Titanium-doped lithium cobalt oxides having the formula LiTixCo1 - xO2 (0 less than or equal to x less than or equal to 0.5) have been synthesized using high temperature solid-state technique and its performance in a lithium rechargeable cell is reported. The synthesized oxides were structurally analyzed using X-ray diffraction (XRD) and Raman spectroscopy. It has been observed that single-phase materials were below 10% of Ti doping whereas impurity spinel phases were detected at higher concentrations. Electrochemical behaviors of the prepared powders were analyzed using cyclic voltammetry (CV) and galvanostatic charge/discharge cycling studies in the voltage range 3.0-4.25 V (vs. Li metal) using 1 M LiClO4/PC as electrolyte. The composition with x = 0.01 exhibits an initial charge and discharge capacity of 157 and 148 mA h/g at 0.2C rate, respectively, as compared to 137 and 134 mA h/g of LiCoO2. Further, more than 90% of the capacity is retained even after 10 cycles. The role of tetravalent doping on the electrochemical behavior of LiCoO2 has not been reported previously. (C) 2003 Elsevier Science B.V. All rights reserved.