Ni-Co coordination hollow spheres for high performance flexible all-solid-state supercapacitor

In this work, hollow spherical nickel-cobalt coordination polymer (Ni-Co/CP) have been synthesized. The hollow structure would facilitate the transport of ions, meanwhile the lamellar sheets may provide more active sites, which are of benefit to achieve high electrochemical performance. The Ni-Co/CP exhibits a high specific capacity of 758.8C g(-1 )at 0.5 A g(-1) . At 20 A g(-1) , the specific capacity is still as high as 584 C g(-1) . The capacity remains 84.6% of its initial value after 5000 cycles. Furthermore, all-solid-state supercapacitors have been assembled using Ni-Co/CP, polybenzimidazole (PBI) doped with KOH and activated carbons (AC) (Ni-Co/CP//PBI-KOH//AC). A high cell specific capacitance of 166.9 F g(-1) have been achieved at 1 A g(-1) with applied potential difference up to 1.8 V, which corresponds to a specific energy of 75.1 W h kg(-1) at 900 W kg(-1) ; the capacitance retention remains 85.5% after 8000 cycles suggesting the good stability. Moreover, the device with a large size (2*7 cm) exhibits good flexibility under bending and folding conditions. It also exhibits a cell specific capacitance of 169.5 F g(-1 )at 0.5 A g(-1) . These results indicate that the Ni-Co/CP and PBI based flexible all-solid-state supercapacitors are very competitive in the future applications of flexible and wearable electronics. (C) 2020 Elsevier Ltd. All rights reserved.