Exploring Li-ion hopping behavior in zinc ferrite and promoting performance for flexible solid-state supercapacitor

Abstract

Zinc ferrite as an electrode material for electrochemical energy storage has attracted much attention due to its good pseudocapacitive performance. However, Li-ion diffusion behavior in zinc ferrite has not been clearly understood, therefore, further improvements are still facing challenges. Herein, we report a controlled growth of single crystal mesoporous zinc ferrite (ZnFe2O4) nanowall arrays on highly flexible carbon textile for flexible supercapacitors. Li-ion hopping behavior and energy barrier in ZnFe2O4 are calculated by the density functional theory. The electrode based on the ZnFe2O4 nanowall arrays exhibits high specific capacity of 162.7 mAhg−1 at 3.35 Ag−1 (1170 Fg−1 at 3.35 Ag−1) with excellent capacity retention of 96.4% after 8000 cycles. Furthermore, a flexible symmetric solid-state supercapacitor based on the ZnFe2O4 nanowall arrays is fabricated, which exhibits excellent capacitive performance (620 F g−1 at 5 mVs−1) with high flexibility and super-long life by retaining 97.35% of its initial capacitance after 10000 cycles, and high energy density of 85 Wh kg−1 at power density of 1000 W kg−1. The results indicate that the ZnFe2O4 nanowall arrays is a promising material for the future generation of high-performance supercapacitors. The finding of Li-ion diffusion behavior presents a better understanding of the pseudocapacitive contribution of spinel structured binary metal oxides.