▎ 摘　　要

Nano-LiMn2O4 and graphene nanosheets were synthesized by sol-gel route and reduction of exfoliated graphite oxides method respectively. Graphene modified spinel LiMn2O4 cathode nanocomposites were synthesized by freeze-drying method. The structure, morphology and electrochemical performance of the synthesized materials were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge techniques. The graphene modified spinel LiMn2O4 nanocomposites exhibited a high discharge capacity of 124.30 mAh.g(-1) at 0.1C, while spinel LiMn2O4 only delivered 107.16 mAh.g(-1) at the same rate. Compared with pure LiMn2O4, the graphene modified LiMn2O4 exhibited excellent cycle ability, with a capacity retention of 96.66% after 100 cycles versus about 74% for pure LiMn2O4. The improved electrochemical performance was attributed to the excellent conductivity of graphene nanosheets. The inductive loop observed in the impedance spectra of the graphene modified LiMn2O4 electrode was attributed to the formation of nano-LiMn2O4 local concentration cell from which current flows in opposition to Li de-intercalation into cathode, consistent with the conditions for the generation of an inductive loop. Consequently a model was proposed to explain the inductive loop response of composites electrode for lithium ion batteries.