High-performance multi-dimensional nitrogen-doped N+MnO2@TiC/C electrodes for supercapacitors

Intercalation of alkali cations (Na+, K+, etc.) or protons (H+) on the surface of MnO2 can improve the theoretical pseudocapacitance in the redox reactions. However, the poor electrical conductivity and vulnerability to agglomeration and dissolution during the redox reactions on MnO2 have hampered practical application. In this work, a network composed of TiC/C nanowires is prepared on Ti6Al4V to produce a conductive three-dimensional substrate on which two-dimensional MnO2 nanosheets are fabricated to form a multi-dimensional MnO2 @TiC/C composite electrode. The three-dimensional TiC/C nanowire network increases the specific surface area between the active species and electrolyte and electron transport efficiency to yield a specific capacitance of 284.8 F g(-1) or 76.0 mAh g(-1). To further improve the conductivity and increase the active sites on the pseudocapacitive materials, nitrogen is incorporated into MnO2 to form the N+ MnO2 @TiC/C electrode with a specific capacity of 371.1 F g(-1) or 103 mAh g(-1) rendering it very attractive to high-performance supercapacitors. After nitrogen doping, the cyclic stability of the electrode is improved greatly, and 91% retention of the gravimetric capacity is accomplished after 50,0 0 0 cycles. The mechanism is investigated by analyzing the pseudocapacitances of the composite electrodes with and without N doping. Nitrogen doping not only changes the elemental composition of the electrode and enhances the conductivity, but also increases the active sites on MnO2. As a result, the pseudocapacitance contribution increases from 66.4% to 76.3% at 1 mV s(-1). The supercapacitor constructed with N+ MnO2 @TiC/C as the positive electrode and nickel foam coated with activated carbon (AC) as the negative electrode shows excellent power density of 5400 W kg(-1) at 23.9 Wh kg(-1). Owing to the excellent electrochemical characteristics and cycling stability, the materials and associated design concept have large potential in energy storage applications. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study developed a composite electrode of MnO2 @TiC/C with nitrogen doping for high-performance supercapacitors. By incorporating nitrogen into MnO2, the conductivity and active sites of the electrode were enhanced, leading to improved specific capacitance and cycling stability. The resulting supercapacitor demonstrated excellent power density and energy storage performance, highlighting the great potential of the materials and design concept in energy storage applications.