Na-ion batteries (NIBs), which possess the same working mechanism as Li-ion batteries (LIBs), have attracted extensive attention and delivered great application potential because of their abundant raw material and excellent comprehensive electrochemical performances. The development of cathodes is one of the key factors for the further industrialization of NIBs. Polyanionic phosphates are a class of cathode materials for NIBs with great research value and application prospect because of their stable 3D-frame structure, suitable working voltage and facilitated Na diffusion path. Among them, NaVPOX (X = O, F) compounds have high theoretical capacities of over 140 mAh/g and deliver an average voltage of over 3.6 V, corresponding to an energy density of more than 500 Wh/kg, which are regarded as cathode candidates with great potential for high-energy NIBs. So far, some of NaVPOX (X = O, F) materials have been reported as cathodes for NIBs and demonstrated completely different crystal structures and Na-storage performance. In this manuscript, we firstly summarized the current research progress and related challenges of NaVPOX (X = O, F) cathodes. Furthermore, a representative KTiOPO-type NaVOPO was successfully prepared and its electrochemical performances were also systematically investigated. Based on these, we committed to emphasizing the relationships between crystal structures and electrochemical performances, and further proposed corresponding guidelines for the design of the advanced cathodes. It is believed that this work can present a profound inspiration for the development of polyanionic cathodes for high-energy NIBs.

中文翻译：

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NaVPO4X（X = O，F）作为先进高能钠离子电池的阴极


钠离子电池（NIB）具有与锂离子电池（LIB）相同的工作机制，因其丰富的原材料和优异的综合电化学性能而受到广泛关注并具有巨大的应用潜力。正极材料的发展是NIBs进一步产业化的关键因素之一。聚阴离子磷酸盐由于其稳定的3D框架结构、合适的工作电压和促进的Na扩散路径，是一类具有巨大研究价值和应用前景的NIB正极材料。其中，NaVPOX（X = O，F）化合物具有超过140 mAh/g的高理论容量，平均电压超过3.6 V，对应的能量密度超过500 Wh/kg，被视为正极材料在高能 NIB 方面具有巨大潜力的候选者。到目前为止，一些NaVPOX（X = O，F）材料已被报道可作为NIB的阴极，并表现出完全不同的晶体结构和储钠性能。在这篇手稿中，我们首先总结了NaVPOX（X = O，F）阴极的当前研究进展和相关挑战。此外，成功制备了具有代表性的KTiOPO型NaVOPO，并系统研究了其电化学性能。在此基础上，我们致力于强调晶体结构与电化学性能之间的关系，并进一步为先进阴极的设计提出了相应的指导方针。相信这项工作可以为高能NIB用聚阴离子阴极的发展提供深刻的启发。