As an energy-storage material, iron phosphide (FeP) has always been a research hotspot on account of its high theoretical capacity and low ion intercalation potential. However, its practical application is seriously limited by the structural damage and poor conductivity caused by the large volume expansion in the discharge process. In this work, the authors report a method combining hydrothermal synthesis with calcination to prepare a hollow sea-urchin-like FeP@C nanocomposite. The hollow sea-urchin-like structure can effectively alleviate volume expansion resulting from sodium (Na⁺)-ion intercalation. Carbon (C) coating not only limits the volume expansion and protects the integrity of the electrode structure but also improves electrical conductivity, promotes electron transmission, improves electrode reaction kinetics and thus improves the cycling performance of the FeP@C electrode. As an anode material of sodium-ion batteries, FeP@C showed good electrochemical performance with a capacity of 284.7 mAh/g after 200 cycles at a current density of 200 mA/g.

中文翻译：

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来自 FeOOH 的分层碳包覆 FeP 具有增强的储钠性能

磷化铁（FeP）作为一种储能材料，由于其理论容量高、离子嵌入电位低，一直是研究的热点。然而，由于放电过程中体积膨胀较大导致结构破坏和导电性差，严重限制了其实际应用。在这项工作中，作者报告了一种将水热合成与煅烧相结合的方法来制备空心海胆状 FeP@C 纳米复合材料。中空的海胆状结构可以有效缓解钠（Na ⁺)-离子嵌入。碳（C）涂层不仅限制了体积膨胀，保护了电极结构的完整性，而且提高了导电性，促进了电子传输，改善了电极反应动力学，从而提高了 FeP@C 电极的循环性能。作为钠离子电池的负极材料，FeP@C表现出良好的电化学性能，在200 mA/g的电流密度下循环200次后容量为284.7 mAh/g。