A novel coating technology for preparation of cathodes in Li-ion batteries

Cathodes for Li-ion batteries were prepared using a novel coating technology. First, on the surface of active cathode particles (Li cobalt oxide, Li manganese oxide etc.) dispersed in a solution a thin film of a polyelectrolyte (e.g., gelatin) is adsorbed. Onto each gelatin-coated active particle, about one layer of highly conducting submicrometers carbon black particles is deposited. In the final step, the carbon black- and gelatin-coated particles are glued together using an additional amount of a polyelectrolyte (gelatin, cellulose, etc.). Due to optimized distribution of carbon black and binder, the final composite material can contain up to 96 wt % of active material, and only 2 wt % of gelatin and 2 wt % of carbon black. The polarization of cathodes prepared by the new technology is considerably lower than that of conventional cathodes. On the other hand, the cycling behavior of both electrode types and the surface-to-surface resistivity of the corresponding dry pellets are similar. Based on microimpedance measurements, these results are explained in terms of a simple model referring to a different distribution of carbon black particles in the newly and conventionally prepared cathodes. (C) 2001 The Electrochemical Society.