Preparation And Performance Of Graphene-based Composite Anode Materials For Lithium-ion Batteries

Abstract:Graphene Oxide (GO) is successfully synthesized by Hummers method, and graphene matarials are prepared by N2H4-H2O reduction of GO. Then the Li4Ti5O12/Graphene composite (LTO/G) is synthesized by two methods:spray-drying and sintering processes, liquid phase reduction prosess. The Cu2O/Graphene composite (Cu2O/G) is prepared by in situ synthesis. XRD, SEM, TEM, FT-IR and Raman are employed to investigate the microstructure of the materials, galvanostatic current charge-discharge is used to study the rate performance and cycling stability of the electrode, and the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are used to explore the kinetics behavior of lithium ion intercalation/deintercalation process of the materials.Graphene materials were prepared by solution reduction of GO. The results indicate that when the batteries are cycled galvanostatically between0.001V and3.0V, the first discharge capacity of the graphene electrode is1212.5mAh-g-1at the rate of0.1C, and the charge capacity is612.4mAh·g-1, which corresponds to50.5%of the coulombic efficiency, the reversible specific capacity is609.3mAh-g-I after30cycles. With the increase of the current density, the reversible specific capacity of the materials decreased rapidly.LTO/G composite is synthesized by spray-drying and sintering processes, under the optimized synthetic conditions (calcination temperature is400℃, the content of graphene is3%), the composite LTO/G has much better electrochemical performances than the pristine LTO, the initial discharge capacities are161.2,147.1and122.5at the rates of5,10and20C, respectively, compared with the LTO, the capacities are improved by12.17%,33.36%and85.32%. AC impedance measurements indicate that the lithium ion diffusion coefficient (D) of the LTO and LTO/G are5.737×10-16and1.045×10-15cm2·s-1, respectively.LTO/G composite is synthesized by liquid phase reduction prosess, with3%graphene content, the composite LTO/G has much better electrochemical performances:it is noteworthy that the capacity of LTO/G at20C (118.7mAh·g-1) is higher than that at10C (110.3mAh·g-1) for the bare LTO.CU2O/G composite is synthesized by one-step reduction process. With20%graphene content, the composite CU2O/G has much better electrochemical performances than the pristine Cu2O. The Cu2O/G composites retain567.3,374.1and106.3mAh-g"1at different current densities of50,100,800mA·g-1, in comparison, the bare Cu2O shows a capacity of353.1,76.6and6mAh·g-1respectively. The EIS and CV tests show that the addition of graphene has improved the conductivity of the materials.