Phosphorus-based anode materials are of considerable interest for grid-scale energy storage systems due to their high theoretical capacity. Nevertheless, the low electrical conductivity of P, large volume changes during cycling, and highly-reactive phosphide surface are hindering their potential applications. Herein, outstanding long-term cycling stability with high retained potassium storage capacity (213.7 mA h g⁻¹ over 2000 cycles) was achieved via the introduction of an alternative potassium bis(fluorosulfonyl)imide (KFSI) salt and by using a layered compound (GeP₅) with a high phosphorus concentration as anode material. Fourier transform infrared spectroscopic mapping results suggest that KFSI salt helps to form an uniform solid electrolyte interphase (SEI) layer and reduces the side reactions at the electrode/electrolyte interface, thus enhancing the cycling performance. In-operando synchrotron X-ray diffraction analysis has revealed the synergistic reaction mechanisms of the K-P and K-Ge reactions. These findings indicate the enormous potential of phosphorus-based anodes for high-performance potassium ion batteries and can attract broad interest for regulating the SEI layer formation through manipulating the salt chemistry.

磷基阳极材料因其理论容量高而备受电网规模的储能系统关注。然而，P的低电导率，循环过程中的大体积变化以及高反应性的磷化物表面阻碍了它们的潜在应用。在本文中，通过引入替代的双（氟磺酰基）酰亚胺钾盐（KFSI）并使用层状化合物（GeP），可实现出色的长期循环稳定性，并具有较高的钾储存容量（2000个循环中为213.7 mA h g ^-1）₅）作为阳极材料具有高的磷浓度。傅里叶变换红外光谱图结果表明，KFSI盐有助于形成均匀的固体电解质相间（SEI）层，并减少电极/电解质界面的副反应，从而提高循环性能。内操作同步加速器X射线衍射分析揭示了KP和K-Ge反应的协同反应机理。这些发现表明，基于磷的阳极在高性能钾离子电池中具有巨大的潜力，并且可以通过控制盐化学来调节SEI层的形成而引起广泛的兴趣。