Thick, asymmetric electrodes enable high-energy-density 3D-printed flexible quasi-solid-state micro-supercapacitors

Achieving thick electrodes concurrent with efficient ion and electron transport remains a critical bottleneck in enhancing the areal energy density of micro-supercapacitors (MSCs). Herein, a quasi-solid-state MSC with bicontinuous thick electrodes is constructed, in which an asymmetric geometry composed of nickel hexacyanoferrate (NiHCF) and activated carbon (AC) is employed. This electrode architecture provides both continuous electron pathways and interconnected porosity, supporting high mass loading simultaneously with fast transport dynamics. The resulting NiHCF//AC MSCs show a wide potential window of 1.6 V, a superior areal capacitance up to 1826 mF cm −2 at 1 mA cm −2 , a notable energy density of 649 μWh cm −2 , and excellent cycling stability (90.2% retention of the initial capacitance after 2000 cycles). Moreover, the MSCs demonstrate excellent mechanical toughness and can be integrated into series–parallel configurations for tunable output. This work mitigates the trade-off between mass loading and charge transport, offering a feasible route toward high-energy-density, flexible, and scalable micro-energy storage systems. 3D-printed quasi-solid-state asymmetric NiHCF//AC micro-supercapacitors achieve a wide voltage window (1.6 V), high areal capacitance (1826 mF cm −2 ), and outstanding energy density (649 μWh cm −2 ), demonstrating their potential for flexible energy storage applications. • 3D-printed asymmetric NiHCF//AC micro-supercapacitors deliver a wide voltage window of 1.6 V and a high areal capacitance of 1826 mF cm −2 • A porous thick-electrode architecture enables efficient ion and electron transport at high mass loading • The devices exhibit excellent mechanical flexibility and integration capability