New devices require energy sources that are both tiny, so they can be easily accommodated, and efficient, so that devices can run for longer and perform more sophisticated functions. This requires the technological feat of fitting maximum energy density into a tiny space. By density this refers to the amount of energy that can be stored within a given device. A low density means that a battery does not hold charge for long and requires more regular ‘charge’ and ‘discharge’ cycles.
To improve energy capacity, researchers from King Abdullah University of Science and Technology have created a microsupercapacitor that exploits three-dimensional porous electrodes. The outcome is a more powerful, micro-sized power unit. The aim is for these devices to be integrated with the next wave of ‘smart’ wearable devices.
The power devices – or ‘micro-batteries’ – are based on films and they have a thickness of only a few micrometers. The film has considerable energy density. The devices are described as ‘microsupercapacitors.’ The devices use two different electrode materials for the cathode (nickel cobalt sulfide) and anode (carbon nanofiber.) The output is such that the microsupercapacitors achieve between one and forty microwatt-hours per square centimetre. This offers improved power capacity.
Discussing the application with Controlled Environments, Professor Husam Alshareef, who led the university team, stated: “while batteries must be charged at a constant voltage, a supercapacitor charges most efficiently by drawing the maximum current that the source can supply, irrespective of voltage.”
Examples of application include self-powered sensors for wearables, security devices, and medical devices aimed at structural health monitoring.
Further initiatives are underway to improve the operation of the microsupercapacitors. This involves integrated the devices with vertically-scaled three-dimensional porous current collectors made from nickel foams. The use of the foam is designed to increase the surface area and improve power consumption.
The technology has yet to be reported to a peer reviewed journal and research is continuing to fine tune the production process.
