Flexible Asymmetric Microsupercapacitors from Freestanding Hollow Nickel Microfiber Electrodes

Abstract

The increasing demand for flexible and wearable microelectronics is a major driving force for the development of high‐performance small‐volume energy sources. Microsupercapacitors exhibit significant potential in energy storage as they provide high power and good cycle stability. Yet, most microsupercapacitors display low energy densities limiting their practical use in microelectronics. Here, synthesis of high surface area freestanding electrodes comprising hollow nickel microfibers is demonstrated. The microfiber nickel electrodes constitute a platform for flexible asymmetric microsupercapacitors exhibiting excellent mechanical resilience as well as high energy density (0.11 mWh cm−2) and power density (37.5 mW cm−2). The freestanding nature and extensive surface area of the electrodes contribute to pronounced areal and volumetric capacitance, energy storage values, and stability after numerous (hundreds) physical bending cycles. The simple preparation scheme and use of an inexpensive building block (e.g., nickel) underscore potential uses as light and flexible energy storage devices.

Miniaturized Energy Storage Devices Based on Two‐Dimensional Materials

“…The MSCs also exhibited good flexibility with a capacity retention of 97 % at a bending degree of 180°. A series of conductive polymers, including PANI, PPy, and polythiophene (PTP), have been explored in combination with graphene for MSC fabrication. Conductive polymers not only enlarge the graphene interlayer distances, but also function as pseudocapacitive components to provide additional capacitance, similar to the roles of many other electrode materials .…”

“…[21] Benefiting from highly pseudocapacitive TP and highly conductive EG, the TP/EG MSCs delivered an areal capacitance of 3.42 mF cm À2 and av olumetric capacitance of 326 Fcm À3 at 10 mV s À1 .A lso, an impressive rate capability up to 1000 Vs À1 was also achieved. The MSCs also exhibited good flexibilityw ith ac apacity retention of 97 %a tabending degree of 1808.As eries of conductive polymers, including PANI, [35,85,86] PPy, [87] and polythiophene (PTP), [88] have been exploredi nc ombination with graphene for MSC fabrication. Conductive polymers not only enlarge the graphene interlayer distances, but also function as pseudocapacitive components to provide additional capacitance, similart ot he roles of many other electrode materials.…”