An advanced sandwich-type architecture of MnCo2O4@N–C@MnO2 as an efficient electrode material for a high-energy density hybrid asymmetric solid-state supercapacitor

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018, Vol.6 (47), p.24509-24522
• Main Authors: Shrestha, Khem Raj, Kandula, Syam, Rajeshkhanna, G, Srivastava, Manish, Kim, Nam Hoon, Lee, Joong Hee
• Format: Article
• Language: English
• Subjects: Asymmetry; Capacitance; Density; Electrochemical analysis; Electrochemistry; Electrode materials; Electrodes; Energy storage; Flux density; Graphene; Gravimetry; Heterostructures; Hydrogels; Ion transport; Manganese dioxide; Mapping; Metal foams; Nitrogen; Retention; Solid state; Supercapacitors; X ray photoelectron spectroscopy
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta08976k

The design and development of innovative heterostructures with multifunctional properties are technically very important for efficient practical energy storage and conversion applications. Herein, we report the synthesis of a nitrogen-doped carbon (N–C) layer sandwiched between MnCo2O4 and MnO2 (MnCo2O4@N–C@MnO2) as a core@sandwich@shell type heterostructure on Ni foam. The thin layer of sandwiched N–C acts as a “superhighway” for good electron/ion transport and protects the MnCo2O4 and MnO2 from destructive morphological changes during repeated charge–discharge processes. The MnCo2O4@N–C@MnO2 material is well characterized by standard techniques, and its energy storage performance is studied in a three-electrode system and solid-state asymmetric capacitor device. The resultant electrochemical performance is compared with those of MnCo2O4 and MnCo2O4@N–C. The MnCo2O4@N–C@MnO2 electrode exhibits an excellent areal/gravimetric capacity of 0.75 mA h cm−2/312 mA h g−1 at 3 mA cm−2 with ca. 89.6% capacitance retention after 10 000 cycles. A solid-state asymmetric supercapacitor device assembled with MnCo2O4@N–C@MnO2 as a cathode and nitrogen-doped graphene hydrogel as an anode exhibits a high energy density of 68.2 W h kg−1 at 749.2 W kg−1 power density without compromising long cycle life (ca. 91.1% retention after 10 000 cycles). The highly efficient energy storage performance of this new class of heterostructures synthesized with earth-abundant materials enables commercial applications.