Thermodynamically induced surface modification for the stabilization of high-capacity LiCoO2

Stabilization of high-specific-capacity LiCoO2 has been demonstrated more than a decade ago by simple modification of the synthesis protocol. However, the stabilization mechanism has remained unclear. In order to identify the origin of such stabilization, LiCoO2 materials were fabricated through three different synthesis routines in this study. All samples provided high specific capacity (190 mAh/g), but only the best sample maintained good cycling stability. Utilizing extensive physical and electrochemical characterization, the improvement was directly correlated to the modification of the chemistry of the surface rather than the bulk. In particular, high-resolution transmission electron microscopy revealed the thermodynamic growth of distinct phases at the surface of the best material. Such an approach enabled a one-step synthesis process, leading to a uniform surface coating from intrinsic constituents as opposed to more complex synthesis techniques required for the extrinsically deposited surface coatings. (c) 2008 The Electrochemical Society.