Unlocking Self‐antioxidant Capability and Processability of Additive‐free MXene Ink towards High‐performance Customizable Supercapacitors

The solution processing of MXene ink is the feasible strategy to realize its state‐of‐the‐art applications. Nevertheless, achieving high stability and processability of additive‐free MXene ink is particularly challenging. Herein, we propose an oxyanion‐terminated Ti3C2Tx MXene ink that exhibits excellent self‐antioxidant capability and processability. The vertex‐connected polyhedrons of oxyanions capping on the Ti3C2 host serve as an in‐situ antioxidative shield, effectively preventing the attack of free H2O molecules while increasing the robustness of the Ti–C bond and reducing the susceptibility of surface Ti atoms to oxidation. Consequently, the shelf life of MXene ink can be extended up to 5 months at room temperature. Moreover, the high electron accumulation of oxyanions enhances the interlayer interactions among MXene sheets through electrostatic binding, which enables the formation of stable and uniform MXene inks with controlled rheological properties and processability. Inspired by Chinese calligraphy, we utilize the oxyanion‐terminated MXene ink to fabricate high‐performance and customizable paper supercapacitors, which exhibit exceptional flexibility and stability, allowing them to be tailored to desired capacity, stretchability, and shapes. This in‐situ surface chemistry strategy of oxyanion can activate the self‐antioxidant capability and solution processability of MXene, paving the way for its widespread applications in flexible and wearable electronics.