Achieving Superior Electrochemical Performance of Polypyrrole‐Based Micro‐Supercapacitors Via Redox ZnI ₂ and Water‐In‐Salt ZnCl ₂ Electrolytes

Abstract Planar micro‐supercapacitors (MSCs) are emerging as crucial power sources within the realm of microelectronics technology, yet their development is hindered by limitations such as low energy density and significant self‐discharge issues frequently found in dual‐layer MSCs. Recently, water‐in‐salt electrolytes are identified as viable alternatives, offering an expansive voltage range compared to traditional electrolytes and opening new avenues for improved performance. Moreover, redox electrolytes add further enhancements by providing pseudocapacitive benefits. A promising strategy involves using a bipolar redox mediator in water‐in‐salt electrolytes to enhance energy storage capability. Herein, this study introduces symmetric polypyrrole‐based MSCs utilizing redox ZnI 2 and ZnCl 2 water‐in‐salt electrolytes (ReWISE). The assembled MSCs exhibit a capacity of 316 mAh cm −3 , an energy density of 351.4 mWh cm −3 , and a power density of 2 W cm −3 , surpassing the performance of conventional carbon‐based MSCs. These MSCs reveal impressive durability, with the device maintaining 76.3% of its initial capacity after 10,000 charging cycles and ensuring the stability of the voltage platform for consistent power output. These findings emphasize the immense potential of ReWISE for advancing MSCs technology, offering a significant leap forward in creating high‐performance, energy‐dense solutions necessary for modern microelectronics.