Аннотация:Sodium-ion batteries (SIB) technology offers an attractive alternative to rechargeable batteries for large-scale application. To meet the practical demands, it is essential to develop stable electrode materials with high capacity and high energy density. Herein, we demonstrate a successful activation of the of Nb5+/Nb4+, Nb4+/Nb3+ and Cr3+/Cr2+ redox couples in NASICON structured NaCrNb(PO4)3, thus introducing a novel three-electron reaction anode for sodium-ion batteries with high specific capacity. Carbon coated NaCrNb(PO4)3 synthesized using the Pechini sol-gel method demonstrates the reversible capacity of 162 mA h*g−1 at 1C rate and good cycling stability. This is a first example of NASICON type anode material with the Cr3+/Cr2+ reversible transition confirmed by Cr K-edge XANES measurements. Operando X-ray powder diffraction showed that sodium insertion-extraction in NaCrNb(PO4)3 proceeds through a combination of single-phase and biphasic processes. The scanning calorimetry study revealed the excellent thermal stability of NaCrNb(PO4)3, which exceeds that of hard carbon anodes, making it a promising anode material for sodium-ion batteries.
