MXene Triggered Free Radical Polymerization in Minutes toward All‐Printed Zn‐Ion Hybrid Capacitors and Beyond

Additive manufacturing of (quasi‐) solid‐state (QSS) electrochemical energy storage devices (EES) highlights the significance of gel polymer electrolytes (GPEs) design. Creating well‐bonded electrode‐GPEs interfaces in the electrode percolative network via printing leads to large‐scale production of customized EES with boosted electrochemical performance but has proven to be quite challenging. Herein, we report on a versatile, universal and scalable approach to engineer a controllable, seamless electrode‐GPEs interface via free radical polymerization (FRP) triggered by MXene at room temperature. Importantly, MXene reduces the dissociation enthalpy of persulfate initiators and significantly shortens the induction period accelerated by SO− 4·, enabling the completion of FRP within minutes. The as‐formed well‐bonded electrode‐GPEs interface homogenizes the electrical and concentration fields (i.e., Zn2+), therefore suppressing the dendrites formation, which translates to long‐term cycling (50,000 times), high energy density (105.5 Wh kg−1) and power density (9231 W kg−1) coupled with excellent stability upon deformation in the zinc‐ion hybrid capacitors (ZHCs). Moreover, the critical switch of the rheological behaviours of the polymer electrolyte (as aqueous inks in still state and become solids once triggered by MXene) perfectly ensures the direct all‐printing of electrodes and GPEs with well‐bonded interface in between, opening vast possibilities for all‐printed QSS EES beyond ZHCs.