LAB-SCALE METHODS FOR CARBON COATING ONTO POWDERS AND APPLICATIONS FOR LI-ION BATTERIES

Abstract

Carbon coating onto fine powders is a commonly used surface modification method in the field of materials science. This is an especially important method for Li-ion battery active materials, which are often carbon coated to improve electrical conductivity and to inhibit surface reactions with electrolyte. In this thesis, two methods of carbon coating technologies were applied on various materials. A new laboratory chemical vapor deposition (CVD) reactor is described, which features an opposing screw rotating fluidized bed. The reactor efficiently concentrates powdered reactants in the reaction zone while maintaining fluidization independent of powder properties. Hydrothermally deposited carbon coatings for Li-ion battery materials were also evaluated. The applied coatings were found to be highly uniform but porous. Nevertheless, carbon coatings on graphite particles produced by both CVD and hydrothermal methods were effective at reducing surface reactions and increasing coulombic efficiency during cycling in lithium cells.