Flexible, high performance battery doubles as a supercapacitor

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Researchers have created an ultra thin, high performance battery that is lithium-free, extremely flexible, only a hundredth of an inch thick, and also doubles as a supercapacitor.

The device consists of nanoporous nickel-fluoride electrodes layered around a solid electrolyte. It is expected to find use in next generation mobile and wearable electronics devices, such as smartphones, smartwatches and fitness bands. "Compared with a lithium-ion device, the structure is quite simple and safe," said Yang Yang, a postdoctoral researcher at Rice University. "It behaves like a battery but the structure is that of a supercapacitor. If we use it as a supercapacitor, we can charge quickly at a high current rate and discharge it in a very short time. But for other applications, we find we can set it up to charge more slowly and to discharge slowly like a battery." To create the battery/supercapacitor, the team deposited a nickel layer on a backing. They etched it to create 5nm pores within the 900m 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. "The numbers are exceedingly high in the power that it can deliver, and it's a very simple method to make high powered systems," said Rice chemist James Tour, adding that the technique shows promise for the manufacture of other 3D nanoporous materials. "We're already talking with companies interested in commercialising this."