Substrate induced coagulation (SIC) in aqueous and non-aqueous media for the preparation of advanced battery materials

Substrate induced coagulation (SIC) is a dip-coating method capable of coating chemically different surfaces with finely dispersed nano-sized solid particles. In the first step of an SIC process the surface is conditioned with a thin layer of polymer or poly-electrolyte. In the second step the conditioned surface is dipped into a dispersion that is close to a point where coagulation occurs. The polymer or polyelectrolyte on the surface induces coagulation of the nano-sized material and a thin layer of the solid is formed. The SIC process can be performed in aqueous as well as non-aqueous media as long as the particles are stabilised (or destabilised) by electrostatic repulsive (or attractive) forces. The theory of Derjaguin, Landau, Verwey and Overbeek (DLVO), describing colloidal stability as well as the zeta-potential and surface charging of dispersed particles are discussed for aqueous and non-aqueous dispersions and some experimental difficulties adressed. For example trace water can have a profound impact on the colloidal stability of non-aqueous dispersions. Dispersions in polar and non-polar media carbon black, titania and alumina, materials so far used for SIC, are discussed. Lithium cobalt oxide has the ability to intercalate lithium ions reversibly. It is the preferred cathode material because it is easy to prepare and has a high specific capacity. Disadvantages of this material are its low electronic conductivity and high reactivity when charged (delithiated). A non-aqueous SIC process was used to prepare lithium cobalt oxide with an improved conductivity by coating with highly conductive carbon black. Furthermore, core-shell cathode materials of lithium cobalt oxide with a protective layer to reduce the materials reactivity when charged (delithiated), are prepared by coating with titania via an aqueous SIC process.