Electrochemical capacitors, also known as supercapacitors, are energy storage devices like batteries, yet they can be recharged a hundred to a thousand times faster. Because of their enabling features, supercapacitors are replacing batteries and capacitors in an increasing number of applications. Supercapacitors are used in today’s smartphones to provide a high-intensity flash for camera phones. In addition, their high power density and excellent low-temperature performance have made them the technology of choice for backup power, regenerative braking and whenever a high power is required in a short period of time. They also play an important role in the progress of hybrid and electric vehicles. However, the low energy density of the current supercapacitors is the main impediment to realizing the full commercial potential of this technology. This has triggered tremendous research efforts in order to develop new electrode materials that are capable of providing a huge amount of energy in a short period of time. In addition, the dramatic increase in flexible and miniaturized electronics has motivated the search for a new generation of energy storage systems that are flexible, foldable and even twistable, can be miniaturized to the microscale and store a large amount of charge per footprint. To address these issues, our research team is active in the following areas.
Large scale fabrication of high-power graphene micro-supercapacitors
The demand for smaller electronic devices has spurred the miniaturization of a variety of technologies including energy storage. Unfortunately, traditional methods for the fabrication of micro-supercapacitors involve labor-intensive and time-consuming lithographic techniques that have proven difficult for building cost-effective devices, thus limiting the commercial applications of micro-supercapacitors. Instead, we use a consumer-grade LightScribe DVD burner to produce graphene micro-supercapacitors over large areas at a fraction of the cost of traditional methods. No photomasks, post-processing or expensive cleanrooms required.
Engineering three-dimensional hybrid supercapacitors and micro-supercapacitors for integrated energy storage
Battery users would like energy storage devices that are compact, reliable, and energy dense, charge quickly, and possess both long cycle life and calendar life. We demonstrate 3D high-performance hybrid supercapacitors and micro-supercapacitors based on graphene and MnO2 by rationally designing the electrode microstructure and combining active materials with electrolytes that operate at high voltages. These hybrid supercapacitors can store as much charge as a lead acid battery, yet they can be recharged in seconds compared with hours for conventional batteries.
Supercapacitors can also be combined with solar cells for storing huge amounts of energy during the day which can then be released at night for the operation of LEDs. Consideration is being given to use this opportunity for off-grid street lighting, thus saving enormous amounts of energy.