A method of coating particles includes dispensing particles into a vacuum chamber to form a particle bed in at least a lower portion of the chamber that forms a half-cylinder, evacuating the chamber through a vacuum port in an upper portion of the chamber, rotating a paddle assembly such that a plurality of paddles orbit a drive shaft to stir the particles in the particle bed, injecting a reactant or precursor gas through a plurality of channels into the lower portion of the chamber as the paddle assembly rotates to coat the particles, and injecting the reactant or precursor gas or a purge gas through the plurality of channels at a sufficiently high velocity such that the reactant or precursor a purge gas de-agglomerates particles in the particle bed.