Hierarchically Structured Nb2O5 Microflowers with Enhanced Capacity and Fast-Charging Capability for Flexible Planar Sodium Ion Micro-Supercapacitors
Jiaxin Ma, Jieqiong Qin, Shuanghao Zheng, Yinghua Fu, Li‐Ping Chi, Yaguang Li, Cong Dong, Bin Li, Feifei Xing, Haodong Shi, Zhong‐Shuai Wu
Abstract
With the booming development of emerging wearable and portable electronics, such as foldable smartphones, shape-conformable healthy monitors and wearable sensors, the flexible and miniaturized energy storage systems are expected to offer excellent energy and power density as well as long lifespan [ 1 , 2 , 3 , 4 , 5 ]. A hybrid ion micro-supercapacitor is made up of a battery-type anode and a capacitor-type cathode, which combines the benefits of battery and supercapacitor and achieves a balance between energy density and power density [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. In this regard, sodium-ion micro-supercapacitors (NIMSCs) are deemed to a highly competitive class of next-generation miniaturized energy storage devices due to more earth-abundant sodium source and its low cost [ 14 , 15 , 16 , 17 ]. According to the working mechanism of sodium ion capacitors, the battery-type anodes have been reported for enhancing Na ion storage performance, including high capacity ( e.g. , RuO 2 , Ti 3 C 2 T x , Ti 2 C ) [ 18 , 19 , 20 ] and decent rate performance (e.g., TiO 2 , NaTi 2 (PO 4 ) 3 , Na 3 V 2 (PO 4 ) 3 ) [ 21 , 22 , 23 , 24 ] and novel polymer materials [ 25 , 26 , 27 ], towards well capacity and/or kinetics matching with capacitor-type cathodes. Unfortunately, the attention is rarely focused on simultaneously fortifying the capacity and rate capability of anode materials. Notably, pseudocapacitive materials possess rapid redox reaction and excellent Na ion storage performance, providing a feasible way to address the trade-off between capacity and kinetics [ 28 , 29 ].