The electrochemical activity of Ni2+/3+ redox couple in the mixed-polyanionic framework Na4Ni3(PO4)2(P2O7) is reported for the first time. The application of a carbon coating and the use of an ionic liquid-based electrolyte enable the reversible Na+ (de-)insertion in the host structure accompanied by the redox activity of Ni2+/3+ at operating voltages as high as 4.8V vs. Na/Na+. These results represent an important step towards the realization of Ni- based mixed polyanionic compounds with improved electrochemical activity and pave ways for the discovery of new Na-based cathode materials and the formulation of Na-ion batteries with very high operating voltages.
- Huang Zhang
- Ivana Hasa
- Stefano Passerini
