Hierarchically Structured NbO Microflowers with Enhanced Capacity and Fast-Charging Capability for Flexible Planar Sodium Ion Micro-Supercapacitors.

HIGHLIGHTS

Hierarchically structured NbO microflowers consiste of porous and ultrathin nanosheets. NbO microflowers exhibit enhanced capacity and rate performance boosting Na ion storage. Planar NIMSCs with charge and kinetics matching show superior areal capacitance and lifespan.

ABSTRACT

Planar Na ion micro-supercapacitors (NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectronics. Nevertheless, the development of NIMSCs are hugely impeded by the low capacity and sluggish Na ion kinetics in the negative electrode. Herein, we demonstrate a novel carbon-coated NbO microflower with a hierarchical structure composed of vertically intercrossed and porous nanosheets, boosting Na ion storage performance. The unique structural merits, including uniform carbon coating, ultrathin nanosheets and abundant pores, endow the NbO microflower with highly reversible Na ion storage capacity of 245 mAh g at 0.25 C and excellent rate capability. Benefiting from high capacity and fast charging of NbO microflower, the planar NIMSCs consisted of NbO negative electrode and activated carbon positive electrode deliver high areal energy density of 60.7 μWh cm, considerable voltage window of 3.5 V and extraordinary cyclability. Therefore, this work exploits a structural design strategy towards electrode materials for application in NIMSCs, holding great promise for flexible microelectronics. [Image: see text]

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40820-023-01281-5.