Surface-Defect Engineering of Nickel Hexacyanoferrate Material for High-Performance Printed Flexible Supercapacitors

Abstract

Flexible supercapacitors (FSCs) are the promising electrochemical energy source for wearable electronic products. However, the absence of high-performance electrode materials and effective manufacturing techniques of device hinder the volume-production of FSCs. Here, a facile surface-etching method is investigated to prepare high-performance nickel hexacyanoferrate (NiHCF) electrode materials and further a screen-printing strategy is employed to realize high-volume production for FSCs. Compared with the conventional NiHCF electrodes, the Na 2 Ni[Fe(CN) 6 ]-based electrode with surface-defect offers a specific capacitance of 262 F g -1 (135 F g -1 of conventional NiHCF) and its capacitance retains 91% after 10000 cycles . According to density functional theory (DFT) calculations, the excellent cycling stability can be attributed to the negligible structural distortion during Na + insertion/extraction process ( ∼ 6% volume change). Subsequently, symmetric FSCs are constructed by printing the NiHCF electrode materials on flexible PET substrates, displaying excellent areal capacitance of 7.3 mF cm -2 (0.1 mA cm -2 ) and energy density and power density of 0.65 μWh cm -2 and 0.4 mW cm -2 , respectively. The surface-defect engineering provides a low-cost strategy to construct nickel hexacyanoferrate materials with outstanding electrochemical properties. And the printing electronic techniques we provided for large-scale and low-cost printed FSCs applications is inspired.

Keywords: nickel hexacyanoferrate, surface-defect strategies, printing electronics, Flexible Supercapacitors, Wearable electronics