Sodium-ion battery technology is one of the best alternative candidates to the lithium analogue due to the low cost and the abundance of sodium. Extensive research effort is dedicated to the development of low-cost and high-performance cathodes. Here, a new sodium-deficient NASICON material Na_3.41£_0.59FeV(PO₄)₃ is synthesized by a simple sol-gel method. This new material delivers high initial discharge capacity of 170 mAh g⁻¹ in the voltage range of 1.5-4.4 V vs. Na⁺/Na, originating from the intercalation of about 3 Na⁺ per formula unit. Furthermore, when cycled in the range of 2.0-3.8 V vs. Na⁺/Na, excellent rate capability and outstanding cycle life are obtained. The remarkable electrochemical performances are attributed to the small volume change (2.36 %) during the sodium extraction through a single-phase mechanism proved by in situ X-ray diffraction (XRD). Refined XRD and ²³Na solid-state Nuclear Magnetic Resonance (NMR) combined with Density functional theory (DFT) calculations reveal that the sodium extraction during charge process occurs preferably from Na2 sites. Moreover, this new cathode exhibits high sodium diffusion kinetics confirmed by Galvanostatic Intermittent Titration Technique (GITT). These findings highlight the beneficial use of non-stoichiometry in electrodes for batteries and provide rational design of high-performance cathode materials for sodium-ion batteries.

钠离子电池技术因其成本低廉和钠含量高而成为锂类似物的最佳替代选择之一。广泛的研究工作致力于开发低成本和高性能阴极。在这里，通过简单的溶胶-凝胶法合成了一种新的钠缺乏的NASICON材料Na _3.41 £ _0.59 FeV（PO ₄）₃。这种新材料在相对于Na ⁺ / Na的1.5-4.4 V电压范围内可提供170 mAh g ^-1的高初始放电容量，这是由于每个配方单元插入了约3 Na ⁺所致。此外，当以Na ⁺在2.0-3.8 V范围内循环时/ Na，可获得优异的速率能力和出色的循环寿命。出色的电化学性能归因于通过原位X射线衍射（XRD）证明的单相机制钠萃取过程中的体积变化小（2.36％）。精致的XRD和²³Na固态核磁共振（NMR）与密度泛函理论（DFT）的计算相结合表明，电荷过程中钠的提取最好从Na2位置进行。此外，这种新阴极具有高恒钠扩散动力学，这已通过恒电流间歇滴定技术（GITT）得以证实。这些发现凸显了非化学计量在电池电极中的有益应用，并为钠离子电池提供了高性能阴极材料的合理设计。