Graphene/hierarchy structure manganese dioxide(GN/MnO_2) composites were synthesized using a simple microwave-hydrothermal method.The properties of the prepared composites were analyzed using field emission scanning electron microscopy(FE-SEM),X-ray diffraction(XRD),transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy(XPS) measurements.The electrochemical performances of the composites were analyzed using cyclic voltammetry,electrochemical impedance spectrometry(EIS),and chronopotentiometry.The results showed that GN/MnO_2(10wt% graphene) displayed a specific capacitance of 244F/gat a current density of 100mA/g.An excellent cyclic stability was obtained with a capacity retention of approximately 94.3% after 500 cycles in a 1 mol/L Li_2SO_4 solution.The improved electrochemical performance is attributed to the hierarchy structure of the manganese dioxide,which can enlarge the interface between the active materials and the electrolyte.The preparation route provides a new approach for hierarchy structure graphene composites;this work could be readily extended to the preparation of other graphene-based composites with different structures for use in energy storage devices.
运用热重-气相色谱质谱联用系统(TGA-GC-MS)在线检测了商用锂离子电池正极物质在燃烧过程中的质量变化及其气相燃烧产物成分,结合X射线衍射仪对固相燃烧产物成分的测定,分析了荷电状态(State of Charge,SOC)对正极物质燃烧产物的影响。结果表明:商用锂离子电池正极物质的固相燃烧产物为Li3Fe2(PO4)3和Fe2O3,气相燃烧产物为CO和CO2,荷电状态对固相产物的成分无影响,对气相产物的影响较大。荷电量为0时,气相燃烧产物中CO的含量最多,烟气毒性最大。而荷电量为50%时,CO的含量最少,烟气毒性最弱。
