Fully Printed, High‐Temperature Micro‐Supercapacitor Arrays Enabled by a Hexagonal Boron Nitride Ionogel Electrolyte

Abstract The proliferation and miniaturization of portable electronics require energy‐storage devices that are simultaneously compact, flexible, and amenable to scalable manufacturing. In this work, mechanically flexible micro‐supercapacitor arrays are demonstrated via sequential high‐speed screen printing of conductive graphene electrodes and a high‐temperature hexagonal boron nitride (hBN) ionogel electrolyte. By combining the superlative dielectric properties of 2D hBN with the high ionic conductivity of ionic liquids, the resulting hBN ionogel electrolyte enables micro‐supercapacitors with exceptional areal capacitances that approach 1 mF cm⁻². Unlike incumbent polymer‐based electrolytes, the high‐temperature stability of the hBN ionogel electrolyte implies that the printed micro‐supercapacitors can be operated at unprecedentedly high temperatures up to 180 °C. These elevated operating temperatures result in increased power densities that make these printed micro‐supercapacitors particularly promising for applications in harsh environments such as underground exploration, aviation, and electric vehicles. The combination of enhanced functionality in extreme conditions and high‐speed production via scalable additive manufacturing significantly broadens the technological phase space for on‐chip energy storage.