Electronic structure of Li sub(2)Fe sub(1-x)Mn sub(x)P sub(2)O sub(7) for lithium-ion battery studied by resonant photoemission spectroscopy

In order to clarify changes in the electronic structures, especially Fe partial density of states (DOS), of Li sub(2)Fe sub(1-x)Mn sub(x)P sub(2)O sub(7) with Mn substitution, we have performed x-ray absorption spectroscopy and resonant photoemission spectroscopy (RPES) experiments for Li sub(2)Fe sub(1-x)Mn sub(x)P sub(2)O sub(7). Using RPES teqniques, we have succeeded in extracting the Fe super(2+) partial DOS. We have found the systematic shift to higher binding energy and broadening of Fe 3d t sub(2g) down-spin states accompanying with the Mn substitution. The peak shift of the Fe 3d t sub(2g) down-spin states is matched very well to the change of Fe super(3+)/Fe super(2+) redox potential, suggesting that the origin of high Fe super(3+)/Fe super(2+) redox potential in Li sub(2)Fe sub(1-x)Mn sub(x)P sub(2)O sub(7) is the shift of the Fe 3d t sub(2g) down-spin states to the higher binding energy with Mn substitution.