Planar Zn-Ion Microcapacitors with High-Capacity Activated Carbon Anode and VO₂ (B) Cathode.

Abstract

The downsizing of microscale energy storage devices plays a crucial role in powering modern emerging devices. Therefore, the scientific focus on developing high-performance microdevices, balancing energy density and power density, becomes essential. In this context, we explore an advanced Microplotter technique to fabricate hybrid planar Zn-ion microcapacitors (ZIMCs) that exhibit dual charge storage characteristics, with an electrical double layer capacitor type activated carbon anode and a battery type VO₂ (B) cathode, aiming to achieve energy density surpassing supercapacitors and power density exceeding batteries. Effective loading of VO₂ (B) cathode electrode materials combined with activated carbon anode onto confined planar microelectrodes not only provides reversible Zn²⁺ storage performance but also mitigates dendrite formation. This not only results in superior charge storage performance, including areal energies of 2.34 μWh/cm² (at 74.76 μW/cm²) and 0.94 μWh/cm² (at 753.12 μW/cm²), exceeding performance of zinc nanoparticle anode and activated carbon cathode based ZIMCs, but also ensures stable capacity retention of 87% even after 1000 cycles and free from any unwanted dendrites. Consequently, this approach is directed toward the development of high-performance ZIMCs by exploring high-capacity materials for efficient utilization on microelectrodes and achieving maximum possible capacities within the constraints of the limited device footprint.