Resonant inelastic X-ray scattering and X-ray absorption spectroscopy on the cathode materials LiMnPO4 and LiMn_(0.9)Fe_(0.1)PO4—a comparative study

摘要

We present a study of the charge-state behavior of the Li-ion battery cathode materials Li_xMnPO4 and LiMn_(0.9)Fe_(0.1)PO4 using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). A set of six identical battery cathodes for each material have been cycled and left in different charge states in the range of x = 0.2.. .1.0 before disassembly in an Ar glove box. Unexpectedly, we find that the Mn 3d-bands are almost inert to the delithiation process, suggesting that Mn ions participate to a very small extent in the charge compensation process. In LiMn_(0.9)Fe_(0.1)PO4 the Fe 3d-band shows much more response to delithiation than the Mn 3d-band. The O 2p-band hybridizes with the bands of the other ions in Li_xMnPO4 and LiMn_(0.9)Fe_(0.1)PO4 and thus, indirectly, carries useful information about the effects of delithiation at all ion sites. We conclude that the redox reactions during lithiation/delithiation of these materials are complex and involve repopulation of charges for all constituent elements.