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

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.

Automated summary

Bimetallic oxides with nanoscale morphology have shown promise as electrode materials for supercapacitors. MnCo2O4 nanoparticles were successfully synthesized via a one-step solvothermal method and exhibited a high specific capacity in alkaline electrolyte. By introducing vapor-grown carbon fibers into the MnCo2O4 material, a composite with improved specific capacity and cycling stability was achieved, leading to the fabrication of a hybrid supercapacitor with enhanced energy and power density.