The Preparation Of Graphene By Chemical Intercalating Method And Its Application In Supercapacitors

Graphene, a monolayer of sp2-bonded carbon atoms, has been attracting great interest around the world owing to its fascinating electronic, optical, thermal, and mechanical properties, and a wide range of potential applications such as nano-devices, sensors, composites, energy storage and catalysis, etc. But, nowadays, one primary reason to graphene based functional materials haven’t been used in people’s everyday life is there no method that realize the preparation of high-quality graphene at large scale. Comparing to other preparation methods, chemical intercalating method has the advantages of mild reactive condition, simple reaction processe and the product without Oxygen-containing functional groups which quite conducive to realize this goal. As a new type of energy storage devices between the conventional capacitors and the common batteries, supercapacitors exhibit higher energy density than conventional capacitors, and greater power density than common batteries. Supercapacitors are now attracting intensive attention owing to its high power desnsities, long cycle life, wide potential range, safety and environmentally friendly. In this dissertation, we mainly committed to design more advanced graphene preparation methods and compare the effects on the electrochemical properties of graphene for supercapacitors. The main results include:1. By improving the raw materials, we designed a modified chemical intercalating method. The most striking feature is that the necessary above800℃high temperature or microwave irradiation in current chemical intercalating method removed, namely natural graphite itself can fully expanded during the intercalating process at the room temperature. Our method greatly reduces the manufacturing cost and the products have good quality.2. Based on the basic principle of chemical intercalating method, we put forward the "molecular shovel" exfoliation method. Intercalated graphite whose interlayer contain abundant acidic groups were made from natural graphite by mixed acid method. Owing to the alkaline amino on benzylamine molecule, there has a tendency power of benzylamine and acidic groups to form ionic bonds, so there formed steric hindrance between the larger size of benzylamine molecules and the smaller spacing of intercalated graphite layers. Then benzylamine molecules acted as "molecular shovel" to "shovel" the graphite layers to produce graphene sheets. It greatly improved the exfoliate efficiency, then we applied the products to produce transparent conductive film. Through subsequent operations, the sheet resistance of our transparent conductive films could reach as low as350Ω/sq at over80%transparency.3. Thermal-reduced graphene oxide (T-RGO) materials are synthesized by modified Hummer’s method followed by thermal reduction under argon atmosphere at different temperatures. Through electrochemical investigations, we compared specific surface area, electrical conductivity and surface functional groups, which is the most significant factor affecting the electrochemical capacitance when T-RGO as electrodes. And the results show that surface functional groups play more significant role in determining the electrochemical capacitance than the specific surface area and electrical conductivity. Therefore, it probably gives a new insight for designing and synthesizing graphene-based electrode materials for supercapacitors and other energy-storage devices.