| Lithium ion batteries have been widely used in portable electronic mobile devices because of its high energy density,long cycle life,environmental friendliness,no memory effect and many other advantages.With the rapid development of electronic mobile devices,high demands about the performance of lithium ion batteries are pursued.At present,the traditionally commercial anode material,graphite has low specific capacity(372mAh g-1),which is far from enough to meet the needs of the development of lithium ion batteries.Therefore,it is necessary to develop new anode materials.Thus,lithium ion batteries were chosen as the study system,with anode material as the research object.Nitrogen doped graphene/bismuth nanocomposite was synthesized and used as the anode material of lithium ion batteries to investigated their lithium storage properties;and on this basis,due to the poor flexibility and inability of bend of traditional electrode materials,we synthesized flexibly functionalized three-dimensional graphene foam and study its electrochemical performance as an anode materials of lithium ion batteries.(1)Nitrogen doped graphene/bismuth nanocomposite was synthesized via a two-step method,combining the gas/liquid interface reaction with the rapid heat treatment method.The nanocomposite was used as an anode material to investigate its electrochemical performance,which delivers a specific capacity as high as 522 mAh g-1.Even after 50 cycles at different current densities from 50 to 1000 mA g-1,the specific capacity can still remain 386 mAh g-1.And at a high current density of 1000 mA g-1,the reversible specific capacity of the nanocomposite can still deliver a specific capacity of 218 mAh g-1.Compared with the reported bismuth based nanocomposites,it exhibits more excellent electrochemical performance.The excellent electrochemical performance of the N-doped graphene/Bi nanocomposite is supposed to benefit from the high electronic conductivity of nitrogen-doped graphene and the synergistic effect of bismuth nanoparticles and nitrogen-doped graphene.(2)A facile and mild method was developed to prepare monolithic and free-standing functionalized graphene foam by template-assisted hydrothermal carbonization reaction based on the renewable biomass source-glucose as the carbon source.The whole preparation process is environmentally benign and easy,and it is low-cost.In addition,the prepared 3D functionalized graphene foam exhibits good flexibility,which can directly be used as flexible electrode materials.We assembled it to coin-type lithium ion batteries and preliminarily studied the electrochemical performance by galvanostatic charge discharge test and cyclic voltammetry method.The results show that the specific capacity is 22 mAh g-1 at the current density of 5 mA g-1.Its lithium storage performance is not ideal,which may be caused by the poor conductivity or properties of the material itself.Although the specific capacity is not ideal,the material exhibits excellent flexibility and can be developed as a flexible current collector material.(3)3D functionalized graphene foam was reduced by using three different reduction methods,containing high-temperature reduction,reduction by hydrazine hydrate and ethylene glycol,respectively.And the products of reduction were characterized by SEM,FITR and Raman.Moreover,the bending performance was also investigated by bending tests.Through comparative analysis,the results show that the 3D functionalized graphene reduced by hydrazine hydrate can exhibit a better reduction effect,and the obtained 3D graphene foam can be well suitable as the flexible current collector. |
