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

Abstract

Abstract We provide a review of our recent studies on the surface chemistries and electronic structures of olivine phosphate cathode materials LiMPO4 (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. LiFePO4 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.