凯发

Graphene materials attract increasing interest in clean energy applications, such as solar cells, supercapacitors, lithium ion batteries, Li-S batteries, and OLED devices. 

For supercapacitors and lithium ion batteries, it is found that graphene composites have a significant improvement in their capacity, rate capability and cycling stability. The roles of graphene are found mainly to form a conductive network, increase electron and lithium ion conductivity, and anchor and trap electrode materials, and their efficiency is dependent upon how strong the interaction between graphene and electrode materials is.

Graphene materials can be used in Li-S batteries. A unique sandwich structure with pure sulfur sandwiched between two graphene membranes was designed for a Li-S battery to trap polysulfides. Furthermore, a graphene membrane was used as both current collector and buffer layer on a polymer separator. These batteries show significant improvement in cyclability and capacity, because the electrode with the graphene membrane can provide rapid ion and electron transport paths, accommodate sulfur volumetric expansion, and store and reuse migrated polysulfides to alleviate the shuttling effect. By incorporating a graphene foam (GF) fabricated by template-directed CVD with reduced graphene oxide aerogel, a three-dimensional hybrid nested hierarchic graphene macrostructure was used as a current collector to solve the low sulfur loading and sulfur content issues of Li-S batteries.

Graphene materials can also be widely used in flexible energy storage devices. For example, a graphene/PANi composite membrane is good electrode material for flexible supercapacitors; by coating active materials on GF, an anode and cathode were made to assemble a thin, lightweight and flexible lithium ion battery and Li-S battery, which show high rate capability and capacity, and excellent flexibility. 

Finally, high-quality graphene transparent conducting films by CVD can be used as transparent electrode to assemble flexible OLEDs with excellent performance.