Thick-Network Electrode: Enabling Dual Working Voltage Plateaus of Zn-ion Micro-Battery with Ultrahigh Areal Capacity

Aqueous Zn-ion micro-batteries (AZMBs) have been recently shown to be promising integrated and safe micropower sources for portable electronics but with wide commercial adoption greatly constrained by their relatively low areal capacity. Although increasing the electrode thickness is proposed, the performance is compromised due to sluggish reaction kinetics, slow ion diffusion rate, and underutilization of active materials. Herein, the technique of utilizing a 3D thick-network electrode, consisting of closely interweaved MnO₂ nanowires (MnO₂ NWs), silver nanowires (AgNWs), and carbon nanotubes (CNTs) is presented. The technique readily enables electrode realization up to a thickness of 351 μm, where the porous structure, high hydrophilicity, and fast electrolyte infiltration jointly contribute to fast kinetics. Matching with a Zn metal anode, the prototyped AZMBs acquire an ultra-high areal capacity/power density of 809 μAh cm^-2/1951 μW cm^-2. Additionally, as MnO₂ NWs and AgNWs collectively participate in the reaction as active substances, the AZMBs deliver dual voltage plateaus to further improve the areal energy density, realizing a maximum value of 896 μWh cm^-2. The 3D thick-network electrode supporting dual working voltage plateaus can provide a path forward for developing AZMBs with simultaneously ultra-high areal capacity and energy density. © 2023 Wiley-VCH GmbH.