Research into efficient charge storage mechanisms has always been an area of interest to the electronics industry, specifically for application segments such as consumer electronics.
The ability to charge a storage device and maintain the charge over a considerable amount of time have been the two most important performance markers of any charge storage technology.
Over the past decade, supercapacitors have been an area of interest to the research fraternity focusing on development of highly efficient battery technologies. Supercapacitors, or ultracapacitors, are electrochemical capacitors that have an extremely high energy density.
While supercapacitors have made a performance mark through their ability to acquire charge at very high speeds, industrial experts feel that there is still a lot of potential to improve their retention capacity. In the current scenario, even the best of the supercapacitors discharge at a very high rate, restricting their dominance in the industrial space.
In an attempt to improve the retention capability of supercapacitors, a team of researchers from the University of California in Los Angeles has developed a manufacturing process for supercapacitors that is said to improve their retention capacity. The process employs single walled carbon nanotubes (SWCNTs). Nanotubes are considered to have the potential to replace conventionally used silicon in applications such as CPUs, memories and radio circuits, due to their small size and very encouraging electrical characteristics.
Traditional supercapacitors are manufactured in layers with a viscous solution between plates, similar to a capacitor. When a voltage is applied across the two electrodes, the positive ions head very quickly to one electrode, and the negative ones to another, building up a charge. This process helps the supercapacitor to store energy at a faster rate, but doesn’t provide resistance from discharging.
In the new process suggested by the team from UCLA, carbon nanotubes were sprayed onto plastic films and two such films were sandwiched between an electrolyte of a water-soluble synthetic polymer, phosphoric acid and water. As a result, an ultrathin supercapacitor is formed, which is in the order of micrometres. This process prevents the supercapacitor from discharging too quickly.
The current implementation of this manufacturing process yields an equivalent of 70 kilowatts per kilogram of energy (9 watt hours per kilogram) – well below the power available in traditional lithium-ion batteries, due to energy losses seen when discharging the supercapacitor. An unusually high resistance exists when energy is moved into or out of the device.
The team is working on resolving these issues, and this effort is expected to result in super thin capacitors, which can be very large and rectangular, about 1 mm thick, making them suitable for use in extremely thin cellphones and mobile gadgets. As these supercapacitors power devices for an extended time period, they can also be charged via remote magnetic fields that do not require wires. As these carbon nanotube-based supercapacitors have properties such as fast charging, reliability, long-term cycling, and the ability to deliver significantly more power than batteries, they are expected to find application in power saving features in CPUs.