Design Synthesis And Electrochemical Performance Research Of Graphene Based Composite Electrode Materials Of Lithium Ion Batteries

Rechargeable lithium ion batteries (LIBs) have attracted great attention both fromacademy and industry communities because of their superior advantages over the othersecondary batteries including the high energy density, low maintenance, and relatively lowself-discharge. Therefore, LIBs are regarded as the potential power for electric vehicles(EVs), hybrid electric vehicles (HEVs). As is known to all, electrode materials (e.g. theanode and the cathode) are an important part for the battery, which will directly affect theperformance of LIBs, and therefore the selection of electrode materials is a crucial factorfor construction of LIBs and improvement of battery performance. Graphene (GN) with atwo-dimensional (2D) honeycomb lattice has become an exciting and appealing materialdue to its prominent physicochemical properties, flexible structure, good electricalconductivity and high surface area. Most important of all, it can serve as an attractive2Dsubstrate for the growth of various metal or metal oxide nanoparticles (NPs). In recent years,hybrid materials based on GN and nanostructured transition metal oxides have been widelyemployed in LIBs, which exhibit significantly improved lithium storage performance.In this thesis, graphene-based anode/cathode composites were prepared. Theirstructures were characterized by XRD, SEM, TEM, and other techniques. They werefurther used as electrode materials for LIBs, and their electrochemical performance wasinvestigated in details. Therefore, the study contents are as follows:(1) A series of ZnO/N-doped GN hybrids (denoted as ZnO–GN) were successfullyfabricated by a facile freeze drying treatment followed by subsequent heat treatment.We successfully fabricated a series of ZnO/N-dopedGN hybrids (ZnO–GN) fromgraphene oxide (GO) and zinc hydroxide [Zn(OH)2] by a facile freeze drying treatmentfollowed subsequent heat treatment. The preparation process is simple, easy to control andno need for any template and surfactant. When used as an anode material for LIBs, thehybrid showed unprecedentedly enhanced cycling stability and rate performance. Moreremarkably, the optimized ZnO–GN hybrid achieved an ultrahigh reversible capacity of900mAh g-1, close to the theoretical capacity (978mAh g-1) of ZnO after100cycles at acurrent density of100mA g-1. (2) V2O5-Graphene hybrids were prepared by hydrothermal-pyrolysis route.The V2O5-Graphene hybrids were synthesized from graphene oxide (GO) andammonium metavanadate (NH4VO3) by a hydrothermal method followed by subsequentannealing treatment. The process is simpler and more practical with higher yield. Thehybrids have structural stability and better electrochemical performance. As cathodematerials for LIBs, a high specific capacity of325mAh g-1can be delivered at the currentdensity of100mA g-1.