Nanoscale differentiation of surfaces and cores for olivine phosphate particles—a key characteristic of practical battery materials

Abstract We provide a review of our recent studies on the surface chemistries and electronic structures of olivine phosphate cathode materials LiMPO 4 (M = Mn, Fe, Co, Ni). Li-depletion and mixed oxidation for the transition metal ions have been detected on particle surfaces, across the family of metal phosphate cathode materials. The effects of surface Li-depletion on optical properties and electronic band structures are discussed. LiFePO 4 doped with metals or ions that are reported in the literature as beneficial for rate capability enhancement show more pronounced surface Li-depletion and mixed oxidation compared to undoped material. This outcome, among others, indicates that the dopant resides predominantly on, and influences, the surface of cathode materials.