- based electrode.*

Manganese hexacyanomanganate (MnHCMn) with an unusual Mn1+ charged valence state has recently been identified as a promising sodium ion anode material, in spite of what appears to be an unfavorable closed-shell electron configuration. I will present an analysis of MnHCMn charge dynamics with bulk- and surface-sensitive soft X-ray absorption spectroscopy (sXAS) and resonant inelastic X-ray scattering (RIXS) at the Mn L3 edge. A charge transfer collective mode is observed, and found to represent the likely energy of the next charging redox plateau, which is yet unachieved in redox experiments. This reveals a unique capability that RIXS can provide for strongly correlated battery electrode materials, and suggests a significant untapped potential for MnHCMn anodes.