NaNbV(PO₄)₃: Multielectron NASICON-Type Anode Material for Na-Ion Batteries with Excellent Rate Capability

NASICON-type NaNbV(PO4)3 electrode material synthesized by the Pechini sol–gel technique undergoes a reversible three-electron reaction in a Na-ion cell which corresponds to the Nb5+/Nb4+, Nb4+/Nb3+, and V3+/V2+ redox processes and provides a reversible capacity of 180 mAh·g–1. The sodium insertion/extraction takes place in a narrow potential range at an average potential of 1.55 V versus Na+/Na. Structural characterization by operando and ex situ X-ray diffraction disclosed the reversible evolution of the NaNbV(PO4)3 polyhedron framework during cycling, while XANES measurements in the operando regime confirmed the multielectron transfer upon sodium intercalation/extraction into NaNbV(PO4)3. This electrode material demonstrates extended cycling stability and excellent rate capability maintaining the capacity value of 144 mAh·g–1 at 10 C current rates. It can be regarded as a superior anode material suitable for application in high-power and long-life sodium-ion batteries.NASICON型NaNbV(PO₄)₃电极材料采用Pechini溶胶-凝胶法合成。该材料在钠离子电池中可发生可逆三电子反应，对应Nb⁵⁺/Nb⁴⁺、Nb⁴⁺/Nb³⁺及V³⁺/V²⁺的氧化还原过程，可逆比容量可达180 mAh·g⁻¹。钠离子的嵌入与脱嵌过程发生在较窄的电位区间，相对于Na⁺/Na的平均电位为1.55 V。通过操作式原位（operando）与非原位X射线衍射开展结构表征，结果揭示了循环过程中NaNbV(PO₄)₃多面体骨架的可逆演化；而X射线吸收近边结构光谱（XANES）的原位测试证实，钠离子嵌入/脱嵌至NaNbV(PO₄)₃的过程中伴随多电子转移。该电极材料展现出优异的长循环稳定性与出色的倍率性能，在10 C电流倍率下仍可维持144 mAh·g⁻¹的比容量。其可被视为高性能负极材料，适用于高功率长寿命钠离子电池的应用场景。