Preparation And Capacitive Properties Of Graphene-based Composites

Graphene has excellent mechanical properties,electrical properties,and thermal conductivity,and is a very competitive electrode material for supercapacitors.However,due to some problems in the preparation and application of graphene,some excellent results about graphene cannot be applied to industrial production.How to mass-produce graphene and how to prevent the stacking of graphene sheets are desperated to be solved to promote the industrial application of graphene.To improve the electrochemical performance and application value of graphene and its composite materials,this thesis focuses on the green batch preparation of graphene,explores the preparation method of graphene with low energy consumption,low cost,pollution-free,and high performance,and introduces heteroatom doping between graphene layers.The main research contents and conclusions are as follows:1)The flake graphites were intercalated with C₂H₄O₃ and H₂O₂.Few-layers graphene was prepared through"intercalation-exfoliation-dispersion".The energy storage performance of the specimens was tested.It shows that C₂H₄O₃ and H₂O₂ can intercalate and oxide graphite,increasing the interlaminar spacing of graphite.After microwave irradiation,the oxidized groups and intercalated molecules can rapidly decompose,achieving rapid and efficient green exfoliation of lamellas.The obtained samples contain a small number of oxidized groups,and their layers are about 5-8 layers.They exhibited a distinctive capacitance and rate performance.The specific capacitance can reach 629 F·g^-1 at the current density of 1 A·g^-1,and exhibited outstanding cycle stability with98%of capacitance retention over 1000 cycles at 10 A·g^-1.Different from the traditional oxidation stripping process,no waste acid is produced during the process,which reduces the pollution to the environment and reduces the cost.2)To improve the electrochemical performance of graphene,NiCo-LDH/graphene composites were prepared by hydrothermal method using self-made few-layer graphene as the matrix,and the loading effect and energy storage performance of the composites under different conditions were explored.The results show that NiCo-LDH nanosheets with an open three-dimensional network structure are prepared on the graphene substrate,which overlaps each other to form abundant pores,which can inhibit the agglomeration of graphene and facilitate the acceleration of the Faradaic redox reaction.The specific surface area and pore volume of the sample with the best energy storage capacity increased to 77.45 m²·g^-1and 0.116 cm³·g^-1,respectively;The specific capacitance of the sample reached 820.6 F·g^-1 at the current density of 1 A·g^-1.After 1000 cycles,the specific capacitance reaches 992 F·g^-1.The composite material has a good cycle life and a good application prospect in the field of energy storage.