Design of Porous 3D Interdigitated Current Collectors and Hybrid Microcathodes for Zn-Ion Microcapacitors

Zinc-ion microcapacitors (ZIMCs) have gained considerable attention for their intrinsic charge storage mechanisms, combining a battery-type anode with a capacitor-type cathode. However, their development is constrained by challenges related to electrode material selection and microscale device design, especially given the limited footprint of such devices. Despite their potential, exploration of smart electrode processing and hybrid materials for on-chip ZIMCs remains limited. In this work, we introduce 3D gold interdigitated electrodes (3D Au IDEs) as highly porous current collectors, loaded with zinc (Zn) as the anode and hybrid activated carbon coated with PEDOT (AC-PEDOT) as the cathode, using an advanced microplotter fabrication technique. Compared with planar Zn//AC ZIMCs, where Zn and AC materials are loaded onto planar Au IDEs, the 3D Au Zn//AC-PEDOT ZIMCs demonstrate significantly enhanced performance. This is attributed to the critical role of IDEs in increasing the charge storage capacity, improving long-term cycling stability, and boosting capacitive-controlled charge storage contributions. The 3D Au Zn//AC-PEDOT ZIMCs achieve an areal capacity of 1.3 μAh/cm², peak areal energy of 1.11 μWh/cm², and peak areal power of 640 μW/cm², surpassing most reported microsupercapacitors. This study highlights how optimized collectors and hybrid electrodes enhance microdevice charge storage while maximizing performance within a constrained footprint.