Engineered NiCo-LDH nanosheets- and ZnFe2O4 nanocubes-decorated carbon nanofiber bonded mats for high-rate asymmetric supercapacitors

Abstract

In this work, we have prepared the hierarchically nanostructured core–shell NiCo layered double hydroxide (NiCo-LDH) nanosheets- and ZnFe2O4 nanocubes-decorated polyacrylonitrile (PAN)/pitch-based carbon nanofibers (PPCNs) webs (NiCo-LDH@PPCNs as cathode and ZnFe2O4@PPCNs as anode materials) with the bonded network structure by a facile and scalable hydrothemal method. Herein, the low-cost pitch with lower softening point (∼90 °C) as co-precursor was utilized to produce the PAN/pitch-based carbon nanofibers (PPCNs) with enhanced electrical conductivity. The obtained PPCNs with pitch content of 30% (PP30CNs) electrode material delivered higher specific capacitance (∼67 F g−1) than that (∼48 F g−1) of the PAN-based carbon nanofibers (PCNs) at 1 A g−1, due to the increased electrical conductivity and lower interfacial charge transfer resistance (RCT) of ∼0.16 Ω. Further, the NiCo-LDH-decorated PP30CNs (NiCo-LDH@PP30CNs) as cathode material showed superior specific capacitance of 1162 F g−1 at 1.0 A g−1 and ultra-high retention rate of 91.56% at 10 A g−1. The ZnFe2O4@PP30CNs as anode material also showed higher specific capacitance of 282 F g−1 at 1 A g−1 and good rate capability with capacitance retention of 56.73% at 10 A g−1. The as-fabricated asymmetric NiCo-LDH@PP30CNs//ZnFe2O4@PP30CNs hybrid supercapacitor device delivered a specific capacitance of ∼98 F g−1 at 1 A g−1 and excellent capacitance retention of ∼88% after 5000 charge–discharge cycles.