Unlocking the Multi-Electron Reactions of Transition Metal (co-)doped Sodium Vanadium Phosphate Cathode Materials via X-ray Absorption Spect

The introduction of further transition metals (TMs) such as Cr, Mn and Ti, into the Na superionic conductor Na3V2(PO4)3 (NVP) used as cathode material for sodium-ion batteries (SIBs), can boost its specific capacity, increasing the specific energy at the full-cell level. Nonetheless, the mechanistic interplay of the dopants in NVP remains unclear. Our objective is to unveil the multi-electron reactions of TM (co-)doped NVP cathode materials, focusing on the impact of Cr, and the synergic interactions of Mn and Ti, which have so far rarely been fully investigated. Ex situ and operando XANES spectra are crucial for elucidating the evolution of oxidation states and the bonding state of the dopant species. EXAFS data will complement the findings by disclosing the evolution of the local structural environment of the TMs. The results are expected to attract significant attention and develop guidelines on the impact of the dopants in this class of cathodes for high-performance SIBs.