Electrostatic self-assembly of MXene and carbon nanotube@MnO2 multilevel hybrids for achieving fast charge storage kinetics in aqueous asymmetric supercapacitors

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 10; no. 44; pp. 23886 - 23895
• Main Authors: Li, Shulong, Peng, Zhongyou, Huang, Yuting, Tan, Licheng, Chen, Yiwang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 15.11.2022
• Subjects: Asymmetry; Capacitance; Carbon; Carbon nanotubes; Electrochemistry; Electrode materials; Electrodes; Energy storage; Graphene; High voltage; Hybrids; Manganese dioxide; MXenes; Nanostructure; Nanotechnology; Nanotubes; Quartz crystal microbalance; Quartz crystals; Raman spectroscopy; Self-assembly; Sodium perchlorate; Structural stability; Supercapacitors; Synergistic effect
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d2ta07123a

Nanostructured birnessite (δ-MnO2) has a high specific capacitance and virtually perfect capacitive behaviors as an essential electrode material for high-power energy storage devices. However, simultaneously achieving excellent capacitive properties and adequate structural stability is particularly challenging. Herein, a conductive and freestanding pseudocapacitive electrode (Ti3C2Tz/CNT@MnO2 abbreviated as TCM) is fabricated by electrostatically assembling Ti3C2Tz nanosheets and δ-MnO2in situ grown on carbon nanotubes (CNT@MnO2). Benefitting from the unique structure, strong interfacial interactions and synergistic effects between Ti3C2Tz nanosheets and CNT@MnO2, the TCM electrode shows a high capacitance value (384 F g−1 at 0.5 A g−1), excellent rate capability, and superior stability (92.2% retention after 10 000 cycles). The outstanding capacitive charge storage of TCM originates from reversible Na+ intercalation/deintercalation, according to electrochemical quartz crystal microbalance (EQCM) and in situ Raman spectroscopy. Remarkably, an assembled asymmetric supercapacitor (ASC) based on the TCM film and nitrogen-doped reduced graphene oxide (NRGO) delivers landmark energy/power densities (44 W h kg−1 and 43.4 kW kg−1) and ultra-long cycle performance. Furthermore, the ASC exhibits a high voltage of 2.4 V with an impressive energy density of 58 W h kg−1 in 10 M NaClO4 salt-in-water electrolyte. This work offers a vital insight and clues to engineering stable birnessite materials for aqueous supercapacitors.