3D interpenetrating assembly of partially oxidized MXene confined Mn–Fe bimetallic oxide for superior energy storage in ionic liquid

Abstract

Owing to unique diatomic synergistic effect and electron-occupied states at Fermi level, Mn–Fe bimetallic oxides hold great promise for high-efficiency supercapacitors (SCs). However, their energy storage behaviors are exploited in the aqueous electrolytes with narrow potential window, consequently leading to the low energy density of SCs. Herein we put forward a novel electrode (Ti3C2TX@MFNDs) with a 3D interpenetrating assembly by confining MnFe2O4 nanodots (MFNDs) in hierarchically layered Ti-MXene (Ti3C2TX), which shows superior energy storage in high-voltage ionic liquid (IL) electrolyte. Remarkably, 3D architecture is effectively constructed by the confinement of MFNDs in partially oxidized Ti3C2TX with high conductivity and abundant active sites, providing multiple and continuous conductive paths for the efficient charge transport, as well as improving the structural stability of MFNDs in the electrode, demonstrated by ex-situ XRD analysis. Furthermore, the Ti3C2TX@MFNDs electrode exhibits a high diffusion coefficient (1.04 × 10−8 m2 s−1) and good wettability in IL electrolyte, indicating its superior IL ion dynamics. As a proof of concept, flexible ionogel SCs (FISCs) are fabricated, presenting high energy density (62.95 Wh kg−1), high power density, remarkable rate capability and long-term durability. Such FISCs can be also charged by harvesting sustainable energy and effectively supply power for practical applications.