Provided herein are methods for processing electrochemically active materials for use in rechargeable batteries. The methods may also be practiced on electrodes and batteries containing such electrochemically active materials. In a typical embodiment, a method of chemically modifying the surface of an electrochemically active component of a battery is provided, the method including receiving the electrochemically active material and exposing the electrochemically active material to a gaseous reactant under conditions that chemically modify surfaces of the electrochemically active material that are accessible to the gaseous reactant, and thereby produce a modified electrochemically active material having improved properties for use in the battery.