Synthesis And Properties Of Carbon-based Anode Materials For Lithium-ion Batteries

Due to the advantages of high voltage, high energy density and environmental friendliness, lithium-ion batteries (LIBs) have attracted increasing interests in the application of portable devices, electronic vehicles and the large energy storage system of smart grid. Amongst the candidates for the anode materials of LIBs, carbonaceous materials are dominant because of their outstanding kinetics. Graphite, the mainstay of the commercial anode materials, delivers a limited specific capacity of372mAh/g, which can hardly meet the requirement of high-performance LIBs, and thus provides ample opportunity for exploring alternative high-performance electrode materials. This paper aims to explore simple synthesis of new types of carbon-based materials which can be used as the high-performance anode materials in the LIBs. The contents are generally included as follows:(1) Carbon nano-onions (CNOs) were prepared by a simple reaction between copper dichloride hydrate (CuCl2·2H2O) and calcium carbide (CaC2). The morphology and structure of the obtained products were investigated by field-emission scanning electron microscope, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectrum, and nitrogen adsorption. Large quantities of CNOs consisting of quasi-spherically concentric graphitic shells with high purity and uniform size distribution (about30nm) were obtained. The crystal water in CuCl2·2H2O plays an important role in the formation of CNOs. The as-obtained CNOs exhibit high capacity and excellent cycling performance as anode materials for LIBs.(2) Hollow carbon nanospheres (HCNSs) were prepared by a template-free approach based on a simple reduction route from the reaction between Zn and sucrose in autoclaves. The as-obtained HCNSs with thin and closely packed graphitic shells possess a high surface area of270m2g-1. When used as anode material for lithium ion batteries (LIBs), the HCNSs exhibit highly reversible capacity, excellent cyclic performance and rate performance due to the fact that the unique hollow structure could not only facilitate rapid mass transport of both electrons and lithium ions, but also supply multiple lithium storage sites in the electrode materials. In addition, when the HCNSs were further carbonized under1350℃, their rate performance have increased a lot in spite of the low capacity caused by the elimination of defects such as pores and edges.(3) Sulfur-doped carbon materials were prepared from the pyrolysis of thiophen by introducing different contents of sulfur. The effect on the morphology and performance of the product under different contents of sulfur addition was investigated. The result shows that the morphology of the as-obtained carbon materials changes from the large spheres into one dimensional structure as increasing the content of sulfur addition. Moreover, the carbon layers in the one dimensional structure are perpendicular to the axis. Accordingly, the performance of the as-obtained carbon materials used as anode materials for LIBs increases with the increase of the content of sulfur addition.