Due to its abundant sodium content and low cost, sodium-ion battery (SIB) has become an effective substitute and supplement for lithium-ion batteries, which has a broad development prospect in large-scale energy storage systems. Na-super-ionic conductor (NASICON) structural materials have stable 3D skeleton structures and open Na⁺ transport channels, which is a very promising SIB cathode material. But in the typical NASICON material Na₃V₂(PO₄)₃ (NVP), the number of electrons involved in NVP per formula unit is less than 2 at the stable voltage window, which limits the further improvement of battery performance. In this work, we report another NASICON structured Na₃V_4/3Cr_2/3(PO₄)₃@C (NVCP@C), which is obtained by Cr-doped NVP through spray drying. By taking full advantage of the voltage platforms of V^5+/4+, V^4+/3+, and V^3+/2+ in the window of 1.5–4.4 V, NVCP@C delivered a high discharge capacity (175 mAh g^–1) and durable cyclability (86% capacity retention for 2000 cycles). In-situ X-ray diffraction results demonstrate that the reversible structural evolution accompanies by solid-solution reaction and two-phase reaction mechanisms co-exist during charge/discharge processes. When coupled with Na⁺ pre-embedded hard carbon (HC), the assembled NVCP@C//HC full cell delivers a high capacity (105 mAh g^–1) and long cycling performance (70% after 1000 cycles). This Cr-doped NVP method offers new insights into the design of high-energy NASICON-structured cathode materials.

由于钠含量丰富、成本低廉，钠离子电池（SIB）已成为锂离子电池的有效替代和补充，在大规模储能系统中具有广阔的发展前景。钠超离子导体（NASICON）结构材料具有稳定的3D骨架结构和开放的Na ⁺传输通道，是一种非常有前途的SIB正极材料。但在典型的NASICON材料Na ₃ V ₂ (PO ₄ ) ₃ (NVP)中，稳定电压窗口下每分子式单元NVP涉及的电子数小于2，限制了电池性能的进一步提升。在这项工作中，我们报告了另一种 NASICON 结构的 Na ₃ V _4/3Cr _2/3 (PO ₄ ) ₃ @C (NVCP@C)，由Cr掺杂NVP经喷雾干燥得到。通过充分利用1.5-4.4 V窗口内的V ^5+/4+、V ^4+/3+和V ^3+/2+电压平台，NVCP@C提供了高放电容量（175 mAh） g ^–1 ) 和持久的循环性能（2000 次循环后容量保持率为 86%）。原位X射线衍射结果表明，充放电过程中固溶反应伴随可逆结构演化，两相反应机制共存。^{当与Na +}结合时预嵌入硬碳（HC），组装好的NVCP@C//HC全电池具有高容量（105 mAh g ^–1）和长循环性能（1000次循环后70%）。这种 Cr 掺杂 NVP 方法为高能 NASICON 结构阴极材料的设计提供了新的见解。