Synthesis And Electrochemical Performance Of CoAl-Layered Double Hydroxides

Supercapacitor, as an energy storage device, has many potential applications in transportation, electro-communication, aerospace science and technology, by combining the advantages of traditional capacitors and batteries. Layered double hydroxides(LDHs) with unique lamellar structure, can provide high specific surface area. Electrical double layer capacitance and faradaic pseudocapacitance can be simultaneously acquired because of their abundant channels and electrochemically active sites when used as active electrode materials. Thus, layered double hydroxides are very promising for next-generation supercapacitors.In this thesis, the electrochemical performances of LDHs are further improved by preventing the agglomeration and improving the conductivity of active materials. CoAl-layered double hydroxide(CoAl-LDH)/graphene oxide (GO) composite was prepared by using microwave method, where the agglomeration of LDHs crystals was greatly suppressed by the combination of graphite oxide. CoAl-LDH nano sheet arrays grown on the surface of foam nickel were also modified by ion sputtering platinum in order to improve the conductivity of electrode materials. The following are focused.1. A microwave-assisted reflux method was developed to rapidly synthesize CoAl-LDH/graphene oxide composite. Those oxygen-containing functional groups on the surface of GO nanosheets acted as nucleation sites for the in situ formation of LDH nanostructures. The presence of GO prevented the aggregation of LDH, while at the same time, LDH crystals led to the exfoliation of GO nanosheets. The composite containing12.9%GO exhibited a high specific capacitance (772F/g was at1A/g) and excellent cyclic performance (about73%specific capacitance retained after10000cycles).2. Three-dimensional network of CoAl-LDH nano sheet arrays was synthesized by hydrothermal method, followed by ion sputtering of Pt. The optimum sputtering time was concluded. The sample exhibited an enhanced electrochemical performance after5minutes sputtering. The specific capacitance reached734.4F/g at3A/g. The sample showed a long life of77%retention and its morphology was retained after6000cycles.