The electroactivity of sodium‐rich manganese hexacyanoferrate (MnHCF) material constituted of only abundant elements, as insertion host for Li‐ and Na‐ions is herein comprehensively discussed. This material features high specific capacities (>130 mAh g−1) at high potentials when compared to other materials of the same class, i.e., Prussian blue analogs. The reversible electronic and structural modifications occurring during ion release/uptake, which are responsible for such high specific capacity, are revealed herein. The in‐depth electronic and structural analysis carried out combining X‐ray diffraction and X‐ray absorption spectroscopy (XAS), demonstrates that both Fe and Mn sites are involved in the electrochemical process, being the high delivered capacity the result of a reversible evolution in oxidation states of the metallic centers (Fe3+/Fe2+ and Mn2+/Mn3+). Along with the Mn2+/Mn3+ oxidation, the Mn local environment experiences a substantial yet reversible Jahn–Teller effect, being the equatorial Mn‐N distances shrunk by 10% (2.18 Å → 1.96 Å). Na‐rich MnHCF material offers slightly higher performance upon uptake and release of Na‐ions (469 Wh kg−1) than Li‐ions (457 Wh kg−1), being, however, the electronic and structural transformation independent of the adopted medium, as observed by XAS spectroscopy.

Exploiting the high-energy density of lithium metal as a negative electrode for lithium batteries is considered a prerequisite to satisfy the continually increasing demand for extended driving range of electric vehicles and fully electrify our mobility and transportation. However, such lithium-metal batteries face critical safety and life-span concerns. This work outlines a clear route toward realizing safe high-energy-density lithium-metal batteries with excellent cycling stability through the use of a non-flammable and low-volatile ionic liquid electrolyte.

The electronic and structural evolution of copper hexacyanoferrate (CuHCF) cathode material was studied by operando X-ray absorption spectroscopy (XAS) simultaneously at both Fe and Cu K edges during a full galvanostatic cycle. The full set of XAS data collected during the electrochemical process was analyzed by a combined chemometric approach using the multicurve resolution analysis with the alternate least squares algorithm. Using this joint approach and by applying a simultaneous multipleedge fitting procedure, it was possible to clarify the participation of both copper and iron centers to the redox processes and to analyze their local environment. The structural modifications occurring in CuHCF along with the redox processes are entirely reversible, with the steady multiplicity of Fe−C−N−Cu linear chains evidencing the structural stability of the material during cycling.