Scalable fabrication of polyaniline nanodots decorated MXene film electrodes enabled by viscous functional inks for high-energy-density asymmetric supercapacitors

MXene (Ti3C2Tx) films are highly favored in flexible energy storage devices, especially supercapacitors because of ultrathin feature and, more importantly, ultrahigh volumetric capacitance. Compared with MXene-based symmetric supercapacitors, designing asymmetric devices by combing positive materials with negative MXene can widen the operating voltage window and further enhance the volumetric energy density. However, the desirable flexible positive electrodes with volumetric capacitance comparable with pristine MXene film electrode are rare. Herein, we demonstrate rational interlayered heterojunction engineering can make MXene-based electrodes likewise possess ultrahigh volumetric performance (1167F cm−3) under positive potential. Intercalating small PANI nanoparticles (~10 nm) into MXene interlayer enables the compact PANI/MXene film electrodes. Furthermore, functional PANI/MXene inks are exploited to fabricate the composite films on a large scale. In the electrode, MXene nanosheets exhibit integrated functions of dispersing, binding, conduction and flexible substrate for PANI nanoparticles. Meanwhile, PANI nanoparticles act as not only high pseudocapacitive materials but also interlayered conductive pillaring components for reducing MXene stacking and enabling electron and ion transport, thereby obtaining an excellent synergistic effect. Additionally, the assembled asymmetric device consists of all-pseudocapacitive compact film materials and delivers an incredible energy density up to 65.6 Wh L-1 (1687.3 W L-1), suggesting the configuration highly effective.