锂离子电池作为最有前途的储能技术之一，因具有循环寿命长、能量密度大、自放电率低、热稳定性能好、记忆效应不明显等优势，已成为新型能源领域的研究热点。本工作以聚丙烯酸(PAA)修饰的粒径约250 nm的Fe3O4微球为核，葡萄糖为碳源，通过水热法制备了Fe3O4@C核壳型微球，研究其作为锂离子电池负极材料的电化学特性。通过X射线衍射(XRD)、扫描电镜(SEM)、热重(TGA–DTA)和傅里叶红外光谱(FT-IR)等手段对其表征，并通过循环伏安特性曲线、循环性能曲线、倍率性能曲线，充放电平台曲线和阻抗及其拟合曲线等研究其电化学性能。结果表明，制备的聚丙烯酸(PAA)修饰的Fe3O4@C核壳型微球球状完整，粒径均一，平均尺寸约310 nm，碳层表面光滑，包覆均匀，平均厚度约30 nm。Fe3O4@C的核壳结构有效缓解了恒流充放电过程中的体积膨胀，避免了晶体结构的快速坍塌。PAA中大量的羧基基团对Fe3O4起到表面改性的作用，有效避免了颗粒团聚，保证了良好的分散性。碳的有效包覆可改善Fe3O4材料作为锂离子电池负极材料的离子和电子电导，增加其比容量、库伦效率和循环稳定性。Fe3O4@C核壳型微球在100 mA/g电流密度下，恒流充放电循环370圈后，仍能保持655 mAh/g放电比容量，约为首次放电的50%，具有良好的容量保持率。

Owing to its long cycle life, high energy density, low self-discharge performance, good thermal stability, and insignificant memory effect, lithium-ion battery (LIB) has attracted research attention as one of the most promising energy storage devices. In this study, as LIB anode materials, polyacrylic acid (PAA)-modified Fe3O4@C core–shell microspheres were synthesized by a hydrothermal method using glucose as the carbon source, and their electrochemical properties were investigated. As-obtained samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy, thermal gravimetric differential thermal analysis (TGA–DTA), and Fourier transform infrared spectroscopy (FT-IR). The electrochemical performance was investigated, including cyclic voltammetry performance, cycle life, rate performance, charge-discharge cycles, and impedance curve fitting. The PAA-modified Fe3O4@C core–shell structure was successfully prepared. Uniform microspheres with a particle size of ~310 nm were obtained, in addition to a uniformly coated carbon layer with a thickness of ~30 nm. In addition, the Fe3O4@C core–shell structure effectively relieved the volume expansion during constant current charge and discharge cycles and prevented the rapid collapse of the crystal structure. A large number of carboxyl groups in PAA exhibited a surface modification effect on Fe3O4, effectively preventing particle agglomeration and ensuring good dispersibility. The effective carbon coating can improve the electrochemical performance of Fe3O4 as the anode material of LIB. The enhanced ionic and electronic conductivities were beneficial for its specific capacity, coulombic efficiency, and cycle stability. Moreover, the Fe3O4@C core–shell microspheres maintained a specific capacity of 655 mAh/g after a constant current charge and discharge cycle of 370 cycles at a current density of 100 mA/g; hence, Fe3O4@C core–shell microspheres can be considered as good candidates for application as LIB anode materials.