Development of a 3D Zinc-Entrained Activated Charcoal Anode for Air-Breathing Battery

A 3D zinc-entrained activated charcoal anode was developed to address the problem of low output current density in conventional planar-anode air-breathing batteries. The anode was a compacted and sintered mix of activated charcoal (AC), polyethylene (PE) and ammonium bicarbonate (ABC). These serve as matrix, binder and pore-former respectively. Samples were compacted at varying ratios of (AC/PE) : ABC and evaluated for suitability as anode structure using Water absorption, Hydrophobicity and Electrical conductivity tests. They were infused under vacuum with ZnSO4 solutions of 0.1, 0.2, 0.3, 0.4, and 0.5 M. It was followed by in-situ galvanostatic electroreduction of Zn ion to elemental zinc to achieve zinc entrainment inside the matrix. This was carried out at varying time intervals. The anode was characterized using Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and X-Ray Fluorescence (XRF). The 3D zinc-entrained anode and a planar zinc anode were evaluated and compared in air-breathing battery configuration using polarisation experiments. Optimal composition of the anode was determined to be 25% (AC/PE) and 10% ABC while optimal conditions for zinc entrainment was 0.4 M ZnSO4 and 150 mins electroreduction time. The microstructures reveal that zinc is being preferentially deposited around the rim of pores and on ridge lines. Polarisation studies showed that the 3D zinc-entrained activated charcoal anode exhibited output current density 2.5 times that of conventional planar zinc anode and a slightly higher Open Circuit Voltage of 1.44 V.. KeywordsAir-cathode, battery, electrodeposition, zinc ◆