多元包覆石墨复合负极材料的低温电化学储锂性能研究

Multicomponent-coated graphite composite anodes for lowtemperature electrochemical energy storage

新能源技术的快速发展对锂离子电池在极端环境的使用提出了更高的要求。目前锂离子电池的低温性能主要受限于石墨负极界面阻抗,导致锂离子的嵌入和脱嵌过程受阻。本文通过液相法将沥青衍生碳和氧化铌颗粒协同包覆在石墨颗粒表面,制备了无定形碳/氧化铌多元包覆石墨复合负极材料(C/Nb-Gr)。调控复合材料制备方法和包覆比例,测试复合负极材料的常温和低温循环性能,对比不同实验方法对复合负极材料电化学储锂性能的影响。结果表明,无定形碳/氧化铌包覆石墨复合负极材料的倍率性能和低温储锂性能有所提升。在室温5C电流密度充放电时,C/Nb-Gr-10材料具有156.18 mAh/g的比容量;在-20℃条件下,C/Nb-Gr-10材料放电比容量为204.60 mAh/g,达到室温放电比容量55.7%的保持率。

The rapid development of new energy technologies has demanded higher requirements for the application of lithium-ion batteries(LIBs)for operation at low temperatures.The poor surface dynamics of graphite anodes is one of the main issues limiting the low-temperature performance of LIBs.In this study,amorphous carbon/niobium oxide multicomponent-coated graphite composite materials(C/Nb-Gr)were synthesized using a liquid-phase method.The optimal C/Nb-Gr ratio was determined by adjusting the preparation method and coating ratio of multicomponent materials.The crystal structure,morphology,and elemental distribution of C/Nb-Gr were characterized using X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and energy-dispersive X-ray spectroscopy.Furthermore,its electrochemical performance at high rates and low temperatures was evaluated using cyclic voltammetry,electrochemical impedance spectroscopy,and charge/discharge cycling.The graphite electrode coated with amorphous carbon/niobium oxide exhibited improved performance at high rates and low temperatures.When charged/discharged at a high current density of 5C at room temperature,C/Nb-Gr-10 demonstrated a reversible specific capacity of 156.18 mAh/g.Under low-temperature conditions(-20℃)at a current density of 0.1C,the discharge specific capacity of C/Nb-Gr-10 was 204.60 mAh/g,representing 55.7%of its room-temperature discharge specific capacity.