Sodium-ion batteries have been considered as one of ideal power sources for energy storage system. However, the choice of cathode material with good cycling stability and high capacity is limited. Herein, a nanocomposite of hierarchical mesoporous iron fluoride and reduced graphene oxide is prepared by an in situ approach. The as-prepared nanocomposite exhibits remarkably high discharge specific capacity of 227.5 mAh/g at 0.1C. Specifically, the discharge specific capacity of the sample still remains 87.5 mAh/g at a high rate of 15C after the 100th cycle. The electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) measurements show that the addition of reduced graphene oxide can effectively reduce the charge transfer resistance and enhance the Na⁺ diffusion rate in the FeF₃·0.33H₂O nanoparticles. The structural changes of FeF₃·0.33H₂O is further investigated by ex-situ XRD, XPS, and ex situ high-resolution transmission electron microscopy.

中文翻译：

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分层介孔氟化铁和还原氧化石墨烯纳米复合材料作为高性能钠离子电池的阴极材料

钠离子电池已被认为是能量存储系统的理想电源之一。然而，具有良好循环稳定性和高容量的阴极材料的选择受到限制。在本文中，通过原位方法制备了分级的介孔氟化铁和还原的氧化石墨烯的纳米复合材料。所制备的纳米复合材料在0.1 C时具有227.5 mAh / g的极高放电比容量。具体而言，样品的放电比容量在15 C的高速率下仍保持87.5 mAh / g在第100个周期之后。电化学阻抗谱（EIS）和恒电流间歇滴定技术（GITT）测量表明，添加还原的氧化石墨烯可以有效降低电荷转移阻力，并增强FeF ₃ ·0.33H ₂ O纳米粒子中的Na ⁺扩散速率。通过异位XRD，XPS和异位高分辨率透射电子显微镜进一步研究了FeF ₃ ·0.33H ₂ O的结构变化。