Graphene And Graphene Composites For Supercapacitors Application

Electrode materials are the key factor of the super-capacitor, and determine the storage properties of super-capacitor. According to the mechanism of the energy storage, electrode materials for super-capacitor consist of electric double-layer materials and pseudo capacitor materials. Graphene?electric double-layer materials? as a single atom of sp2 hybrid two-dimensional materials, with high specific surface area and excellent conductivity, as a result, graphene as super-capacitor electrode materials has excellent stability and cycle life. Fe₃O₄ and MnO₂?pseudo capacitor materials? can provide performance of pseudo capacitor and low-price, but the lower conductivity and more serious degradation with the cycles subject to application. In this paper, graphene/Fe₃O₄ and graphene/MnO₂ composite materials were prepared by different methods, the excellent performance of two materials, which was expected to prepare excellent electrochemical performance of super-capacitor.In this paper, graphene was produced by an improved Hummer method. Fe₃O₄ nanoparticles were produced by coprecipitation method. Graphene/Fe₃O₄ composite materials has been successfully prepared by the one-step reduction and self-assembly of the mixture of GO in the present of Fe₃O₄ nanoparticles. Research into influence of reaction temperature and materials ratio on the electrochemical properties of composite materials graphene/Fe₃O₄, the research found that in 90?, 2.5mL Fe₃O₄ conditions, the preparation of electrode materials for the best electrochemical performance. Composites prepared by BET analysis of the Graphene sheet consisting of slit pore structure, surface area with 373.9m2/g. Through the BET analysis, the preparation of composites which was the graphene sheet consisting of slit pore structure. Electrochemical measurements show that the capacity of composite reached 219F/g?at 20mV/s,-0.3¹.4Vvs.SCE?. Under the same test condition that the capacity was almost twice of pure reduced graphene and triple of only Fe₃O₄. Even at the 10A/g of current density, 87F/g was maintained. In 1500 cycles, 97% capacity was maintained.Higher quality graphene was prepared by plasma chemical vapor deposition on Stainless Steel, Nickel foam, Stainless steel mesh. We researched the effects of different current collector on the influence of capacitance characteristics of graphene. Results show that the graphene nanowall deposition on stainless prepared supercapacitor reached 51F/g?at1M LiClO4/PC, 30mV/s,-0.3¹.4Vvs.SCE?. In this paper, using 2M Mn?CH3COO?2/C2H5 OH as raw material, voltage DC power supply for deposition, manganese dioxide was deposited on graphene. We research of DC voltage, electrochemical deposition time on capacitance characteristics of graphene /MnO₂, results showed that the best deposition voltage is 0.9V, the best time is 10 min. And graphene/MnO₂ preparation of supercapacitor, capacitors up to 115F/g?at1M LiClO4/PC,-0.3¹.4Vvs.SCE?, specific capacity is about twice the Graphene. When the scanning speed increases from 30 to 1000mV/s, the cyclic voltammetric curve shape remains stable and not deformed. Graphene/MnO₂ was preparation of supercapacitor after 5,000 cycles remain more than 95% capacity.