Modifications to the surface of an electrode and/or the surfaces of the electrode material can improve battery performance. For example, the modifications can improve the capacity, rate capability and long cycle stability of the electrode and/or may minimize undesirable catalytic effects. In one instance, metal-ion batteries can have an anode that is coated, at least in part, with a metal fluoride protection layer. The protection layer is preferably less than 100 nm in thickness.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with Government support under Contract DE-AC0576RLO1830 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.