High-performance planar Zn-ion micro-capacitors

Abstract

Planar Zn-ion-based micro-capacitors (ZIMCs) present intriguing potential due to their unique blend of characteristics: battery-like anode properties and supercapacitor-like cathode attributes, offering intermediate energy storage capabilities with higher energy density than supercapacitors, superior power density compared to batteries, long-term cycling stability, slow self-discharge rates, and compatibility with ambient air processing. While electrodeposition facilitates the loading of Zn onto microelectrodes, incorporating high-capacity activated carbon cathode materials onto microelectrodes poses challenges, especially when the interdigitated electrode gap is less than 300 μm. Nevertheless, narrowing this gap is crucial to enhance ion transport, reduce charge transfer resistance, and maximize the effective utilization of the device's active area within its footprint. This study aims to achieve efficient loading of Zn and activated carbon onto gold interdigitated micro-electrodes to develop high-performance ZIMCs, utilizing a straightforward Microplotter technique capable of loading diverse materials onto microelectrodes effectively. The formed ZIMCs exhibit superior charge storage performance, including an areal energy of 1.2 μW h cm⁻² at an areal power of 46.56 μW cm⁻², and 77% capacity retention after 1000 cycles. Further, our ZIMCs shows slow self-discharge response with only 26% voltage drop after 30 h.