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

Cathodes for Li-ion batteries were prepared using a novel coating technolog y. First, on the surface of active cathode particles (Li cobalt oxide, Li m anganese oxide etc.) dispersed in a solution a thin film of a polyelectroly te (e.g., gelatin) is adsorbed. Onto each gelatin-coated active particle, a bout one layer of highly conducting submicrometers carbon black particles i s deposited. In the final step, the carbon black- and gelatin-coated partic les are glued together using an additional amount of a polyelectrolyte (gel atin, cellulose, etc.). Due to optimized distribution of carbon black and b inder, the final composite material can contain up to 96 wt % of active mat erial, and only 2 wt % of gelatin and 2 wt % of carbon black. The polarizat ion of cathodes prepared by the new technology is considerably lower than t hat of conventional cathodes. On the other hand, the cycling behavior of bo th electrode types and the surface-to-surface resistivity of the correspond ing dry pellets are similar. Based on microimpedance measurements, these re sults are explained in terms of a simple model referring to a different dis tribution of carbon black particles in the newly and conventionally prepare d cathodes. (C) 2001 The Electrochemical Society.