Activating multielectron reactions of sodium superionic conductor (NASICON)-type cathodes toward higher energy density remains imperative to boost their application feasibility. However, multisodium storage with high stability is difficult to achieve due to the sluggish reaction kinetics, irreversible phase transitions, and negative structural degradation. Herein, a kind of NASICON-type Na_2.5V_1.5Ti_0.5(PO₄)₃/C (NVTP-0.5) hierarchical microsphere consisting of abundant primary nanoparticles is designed, realizing a reversible 3.2-electron reaction with high stability. The optimized NVTP-0.5 cathode demonstrates an ultrahigh discharge capacity of 192.42 mAh g^–1, energy density of up to 497.3 Wh kg^–1 at 20 mA g^–1, and capacity retention ratio of 94.1% after 1000 cycles at 1 A g^–1. Additionally, the NVTP-0.5 cathode delivers excellent tolerance to extreme temperatures while also achieving a high-energy density of 400 Wh kg^–1 (based on the cathode mass) in a full-cell configuration. Systematic in situ/ex situ analysis results confirm the multisodium storage processes of NVTP-0.5 involving successive redox reactions (V²⁺/V³⁺, Ti³⁺/Ti⁴⁺, and V³⁺/V⁴⁺ redox couples) and reversible structure evolution (solid-solution and biphasic mechanisms), which contribute to the high capacity and excellent cycling stability. This work indicates that the rational regulation of components with different functions can unlock more possibilities for the development of NASICON-type cathodes.

中文翻译：

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聚阴离子阴极中的超越三电子反应实现钠离子电池的高能量密度


激活钠超离子导体（NASICON）型阴极的多电子反应以获得更高的能量密度仍然是提高其应用可行性的必要条件。然而，由于缓慢的反应动力学、不可逆的相变和负面的结构降解，高稳定性的多钠储存很难实现。在此，一种NASICON型Na _2.5 V _1.5 Ti _0.5 (PO ₄ ) ₃ /设计了由丰富的初级纳米颗粒组成的C（NVTP-0.5）分级微球，实现了高稳定性的可逆3.2电子反应。优化的NVTP-0.5正极表现出192.42 mAh g ^–1 的超高放电容量，20 mA g ^–1 时能量密度高达497.3 Wh kg ^–1 ， 1 A g ^–1 1000次循环后容量保持率为94.1%。此外，NVTP-0.5 阴极具有出色的极端温度耐受性，同时在全电池配置中实现了 400 Wh kg ^–1 （基于阴极质量）的高能量密度。系统的原位/异位分析结果证实了NVTP-0.5的多钠储存过程涉及连续的氧化还原反应（V ²⁺ /V ³⁺ , Ti ³⁺ /Ti ⁴⁺ 和 V ³⁺ /V ⁴⁺ 氧化还原对）和可逆结构演化（固溶体和双相机制），这有助于实现高容量和优异的性能循环稳定性。这项工作表明，合理调控不同功能的组分可以为NASICON型阴极的发展释放更多可能性。