Micro‐Redoxcapacitor: A Hybrid Architecture Out of the Notorious Energy‐Power Density Dilemma

Abstract Insufficient areal energy density along with unstable delivery, resulting from a linearly sloped time‐voltage response rooting in redox‐free/surface‐redox operating mechanisms severely restricts the application scenarios of micro‐supercapacitors. Herein, by coupling silver nanowires (AgNWs) between MXene interlayers with the help of bacterial cellulose (BC) as bio‐dispersant toward MXene/AgNWs&BC hybrid cathode to pair with Zn anode, a novel Zn 2+ ‐Cl − dual‐ions micro‐redox capacitor (MRC) employing polyacrylamide/ZnCl 2 + NH 4 Cl hydrogel electrolyte is first present. The introduced AgNWs nanopillars alleviate the MXene nanosheets restacking to facilitate Cl − transfer kinetics, and concurrently strengthen the charge storage capacity and output stability benefiting from a flat discharge plateau stemming from the extra phase transition behavior (Ag ⇔ AgCl). Thus, an appealing dual energy storage mechanism, featuring i) expedited Cl − diffusion involved de/intercalation and ii) reversible solid‐to‐solid conversion of Ag/AgCl redox couple confined between MXene interlayers, is established and revealed by in situ XRD/Raman analyses. Consequently, remarkably boosted areal energy density up to 227 μ Wh cm −2 along with significantly improved output stability and suppressed notorious self‐discharge behavior, are achieved in the resultant MRC. This work provides a brand new strategy for designing innovative MXene‐based MRC featuring a hybrid charge storage mechanism of ions‐intercalation and phase conversion to simultaneously realize high and steady energy output.