Solvothermal-derived nanoscale spinel bimetallic oxide particles rationally bridged with conductive vapor-grown carbon fibers for hybrid supercapacitors

Abstract

Recently, bimetallic oxides with nanoscale morphology have emerged as promising and reliable electrode candidates for supercapacitors. Herein, we synthesized MnCo2O4 nanoparticles (NPs) (≤100 nm) via a facile one-step solvothermal method without further calcination. Thanks to the multi-valence states of manganese and cobalt elements as well as the structural characteristics of NPs, the MnCo2O4 NPs material delivered a maximum capacity of 44.8 mAh g−1 at a current density of 2 A g−1 in alkaline electrolyte. To improve the electrical conductivity and electrokinetics, vapor-grown carbon fibers (VCFs) were introduced into the MnCo2O4 (VCFs@MnCo2O4) material. Here, the VCFs connected to NPs can act as conductive bridges among the MnCo2O4 NPs and also transfer the generated charge promptly to the current collector. Consequently, the VCFs@MnCo2O4 composite demonstrated a higher specific capacity of 48.4 mAh g−1 (at 2 A g−1) than solitary MnCo2O4. Besides, the VCFs@MnCo2O4 composite demonstrated excellent cycling stability without degradation even after 2000 and 10000 charge-discharge cycles. Furthermore, the hybrid supercapacitor (HSC) was fabricated with VCFs@MnCo2O4 as a cathode and activated carbon as an anode, which showed a good specific capacitance of 63.8 F g−1 (2 mA cm−2). Also, this HSC device exhibited a considerable energy density of 20.6 Wh kg−1 and a power density of 2251.5 W kg−1. The efficiency of HSC was also tested by driving electronic components.