Oxygen-scavenging MnO₂ nanoparticles enabled thermally stable and oxidation-resistant MXene inks for 3D-printed flexible asymmetric supercapacitors

Abstract MXenes have emerged as promising candidates for flexible and printed energy storage systems due to their metallic electrical conductivity and hydrophilicity. However, their practical application is severely hindered by the restacking of delaminated sheets and rapid oxidative degradation under ambient or elevated temperatures. To address these critical challenges, we propose a strategy using redox-active 0D manganese dioxide (MnO 2 ) nanoparticles decorated on 2D MXene sheets to serve as effective oxygen scavengers. Density functional theory (DFT) simulations and X-ray photoelectron spectroscopy (XPS) analyses confirm that MnO 2 preferentially interacts with oxygen species, thereby significantly mitigating the oxidation of the MXene backbone. Furthermore, by incorporating 1D silver nanowires (AgNWs) to optimize ink rheology and conductivity, we developed a 0D/1D/2D hybrid ink capable of direct ink writing (DIW) 3D printing without the need for additional metal current collectors. The resulting fully printed asymmetric supercapacitor exhibited a high areal capacitance of 565.1 mF cm − 2 and an areal energy density of 0.2 mWh cm − 2 . Notably, the device demonstrated exceptional durability with 98.52% capacitance retention after 10,000 charge-discharge cycles and maintained stable electrochemical performance across a wide temperature range from 10 to 50 °C. This work presents a robust solution for overcoming the intrinsic instability of MXenes, paving the way for reliable, high-performance flexible electronics.