Preparation Of Three Dimensional Grephene Aerogel Based Composites And The Research Of Its Electrochemical Performances

As one of the most promising energy storage devices,lithium ion battery?LIBs?has been widely studied in electric vehicle field.However,graphite,as the main anode material for commercial LIBs,still has some disadvantages,such as low specific capacity,short cycle life and poor safety,which can not meet the demand of high energy density and big power density for industrial electric vehicles.The anode material is one of the important components of LIBs,so it is very important to choose and prepare the anode materials for high-performance LIBs.Metal oxides and metal sulfides have become one of the most promising alternative anode materials due to their high theoretical specific capacity,low cost and environmental friendliness.However,there are still a large volume change during the process of charge-discharge cycle and poor conductivity,which greatly limits its commercial application.Graphene aerogel?GA?is a new type of 3D carbon material developed in recent years.It is one of the most popular conductive carbon substrates,because it perfectly combines the excellent physical and chemical properties of graphene and the inherent high porosity of aerogels.By combining it with metal oxides and metal sulfides,which can obviously improve the conductivity,specific surface area and structural stability of the whole material,thus improving the electrochemical performances of the whole material.In this paper,several graphene aerogel matrix composites with different structures were prepared and their electrochemical properties were evaluated.The main contents are as follows:?1?The lamellar reverse micelles formed by using P123 surfactants in mixed solvents were used as the growth template and biphase TiO₂ were firstly synthesized.Then,the biphase TiO₂/GA?TGAs?was prepared by a electrostatic self-assembly process between the diallyldimethylammonium chloride?PDDA?modified TiO₂ and graphene oxide?GO?,followed by a one-pot hydrothermal method and freeze-drying technique.The final samples were characterized by means of X-ray Diffraction?XRD?,Scanning Electron Microscopy?SEM?,Transmission Electron Microscopy?TEM?,High Resolution Transmission Electron Microscopy?HRTEM?,Thermogravimetric Analysis?TGA?and N₂ Adsorption-Desorption?BET?.The results show that the as-prepared TGAs is a 3D porous network structure coated with the biphase?anatase/TiO₂?B??TiO₂.In addition,the biphase TiO₂ is actually a 3D big aggregates compose of 2D TiO₂ nanosheets.Electrochemical measurements show that the TGAs electrode exhibits a better electrochemical performance than the bare biphase TiO₂electrode,especially,its cycling stability(200.8 mA·h·g^-11 after 100 cycles at a current density of 100 mA·g^-1)and rate capability(99.8 mA·h·g^-1at a large rate of 2000 mA·g^-1).?2?The hollow CoMn₂O₄ nanospheres were prepared by using carbon spheres as a template and modified by silane coupling agent APTES.The hollow CoMn₂O₄/GA?ZGAs?was prepared by a one-step hydrothermal method and subsequent freeze-drying technique using the modified CoMn₂O₄ and GO as raw materials.The final samples were characterized by means of XRD,TEM,SEM and BET.The results show that the as-prepared ZGAs sample is a 3D porous network structure coated with hollow CoMn₂O₄nanospheres,and the average diameter of hollow CoMn₂O₄ spheres is about 200 nm.Electrochemical measurements show that ZGAs electrode exhibits a more excellent electrochemical performance than the bare hollow CoMn₂O₄ electrode,especially,its cycling stability(966.8 mA·h·g^-11 after 50 cycles at a current density of 100 mA·g^-1)and rate capability(754.7 mA·h·g^-11 at a large rate of 2000 mA·g^-1).?3?The NiCo₂S₄ nanotubes were firstly prepared by a two-step hydrothermal method.Then,the NiCo₂S₄ nanotubes/GA?NGAs?was prepared by a electrostatic self-assembly process between the diallyldimethylammonium chloride?PDDA?modified NiCo₂S₄nanotubes and GO,followed by a one-pot hydrothermal method and freeze-drying technique.The final samples were characterized by means of XRD,SEM,TEM,HRTEM,TGA and BET.The results show that the as-prepared NGAs sample is a 3D porous network structure coated with NiCo₂S₄ nanotubes,and the average diameter of NiCo₂S₄ nanotubes is about 200 nm.Electrochemical measurements show that NGAs electrode exhibits a more excellent electrochemical performance than the bare hollow CoMn₂O₄ electrode,especially,its cycling stability(967.5 mA·h·g^-11 after 50 cycles at a current density of 100 mA·g^-1)and rate capability(654.7 mA·h·g^-11 at a large rate of 2000 mA·g^-1).