Wang Peifeng, Ma Xiao, Yang Pu, An Jingyi, Xu Youlong
Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Shaanxi Engineering Research Center of Advanced Energy Materials & Devices, School of Electronic Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.
Small. 2025 Sep;21(36):e2506046. doi: 10.1002/smll.202506046. Epub 2025 Jul 9.
NaV(PO)F (NVPF) is a promising sodium-ion battery cathode due to its high voltage and structural stability, but suffers from fluorine loss, suboptimal capacity from limited Na⁺ extraction, and insufficient stability at deeper Na (de)intercalation. Therefore, this study used in situ thermogravimetry-infrared-mass spectrometry for the first time to clarify the fluorine loss mechanism during the synthesis of NVPF. Based on this, a targeted dynamic fluorine compensation strategy is proposed, using NHF as a dual-functional additive that combines the functions of fluorine source and pH buffer. The optimal NVPF-12.5NHF shows the characteristics of completely suppressing the impurity phase. In addition, by expanding the voltage window to 1.0-4.4 V to activate the redox reaction of V/V, the ultrahigh specific capacity of NVPF is achieved via the electrochemical insertion of additional Na. The NVPF-12.5NHF cathode exhibits an astonishing specific capacity of 173.6 mAh g at a rate of 0.3C (64 mA g), and maintains a specific capacity of 96.1 mAh g at 33C. Furthermore, the capacity retention rate is more than 70% after 2000 cycles at 13C. These findings establish a scalable strategy for designing electrode materials with volatile components, offering significant potential to accelerate the practical deployment of sodium-ion batteries.
NaV(PO)F（NVPF）因其高电压和结构稳定性而成为一种很有前景的钠离子电池正极材料，但存在氟损失、Na⁺脱出受限导致容量不理想以及在更深的Na（脱）嵌入过程中稳定性不足等问题。因此，本研究首次采用原位热重-红外-质谱联用技术来阐明NVPF合成过程中的氟损失机制。在此基础上，提出了一种有针对性的动态氟补偿策略，使用NHF作为兼具氟源和pH缓冲功能的双功能添加剂。最优的NVPF-12.5NHF表现出完全抑制杂质相的特性。此外，通过将电压窗口扩大到1.0-4.4V以激活V/V的氧化还原反应，通过额外Na的电化学嵌入实现了NVPF的超高比容量。NVPF-12.5NHF正极在0.3C（64mA g）的电流密度下展现出惊人的173.6mAh g的比容量，在33C时保持96.1mAh g的比容量。此外，在13C下循环2000次后容量保持率超过70%。这些发现为设计具有挥发性成分的电极材料建立了一种可扩展的策略，为加速钠离子电池的实际应用提供了巨大潜力。
