Structural change of Li1-xNi0.5Mn0.5O2 cathode materials for lithium-ion batteries by synchrotron radiation

Synchrotron X-ray diffraction and XAFS measurement have been employed to investigate structural change and the charging process of a layered LiNi0.5Mn0.5O2 cathode material. The structure of charged Li1-xNi0.5Mn0.5O2 (x = 0.5). which corresponds to the composition for showing, rechargeable capacity, was determined. The results showed that divalent nickel metal was oxidized to trivalent after charging, in association with the phase transition from hexagonal (R $(3) over bar $m) to monoclinic (C2/m) resulting from the ordering of cations in the layered structure.