Researchers at Rice University have created a thin film for energy storage that could be used for flexible, portable and wearable electronics.
The flexible material, which was developed by Rice chemist James Tour and his colleagues, features nanoporous nickel-fluoride electrodes layered around a solid electrolyte to deliver battery-like supercapacitor performance that the team says combines the best qualities of a high-energy battery and a high-powered supercapacitor without the lithium found in commercial batteries today. Their research is detailed in Journal of the American Chemical Society.
Their electrochemical capacitor is about a hundredth of an inch thick but can be scaled up for devices either by increasing the size or adding layers. The team expects that standard manufacturing techniques may allow the battery to be even thinner.
In tests, the students found their square-inch device held 76 percent of its capacity over 10,000 charge-discharge cycles and 1,000 bending cycles.
Tour said the team set out to find a material that has the flexible qualities of graphene, carbon nanotubes and conducting polymers while possessing much higher electrical storage capacity typically found in inorganic metal compounds. Inorganic compounds have, until recently, lacked flexibility, he said.
To create the battery/supercapacitor, the team deposited a nickel layer on a backing. They etched it to create 5-nanometer pores within the 900-nanometer-thick nickel fluoride layer, giving it high surface area for storage. Once they removed the backing, they sandwiched the electrodes around an electrolyte of potassium hydroxide in polyvinyl alcohol. Testing found no degradation of the pore structure even after 10,000 charge/recharge cycles. The researchers also found no significant degradation to the electrode-electrolyte interface.
In February 2013, EartTechling reported on UCLA researchers using a laser optical drive (usually used to label DVDs) and graphene to mass-produce micro supercapacitors. The team managed to produce more than 100 super capacitors on a single DVD-sized disc in less than 30 minutes.