Electricity generation and electrochemical insight of zinc-air battery via microfluidic flow control

Abstract

With the evolving demands towards the ever-growing portable and wearable electronics, Zn-air battery (ZAB) has attracted considerable attention as their higher energy density and abundant material reservations compared with other electrochemical energy-conversion systems. Herein, we provide an effective and powerful microfluidic platform for ex-site observing the zinc electrode variation in the electrolytes under different operational situations. The power generation properties of microfluidic ZAB (μZAB) are facilely controlled via the microfluidic flow control. The device delivers the maximum power density of 194 mW/cm2 at the current density of 242 mA/cm2, outperforming previously reported power supplies with similar working volume. More importantly, the combination of ZAB with microfluidic control provides a platform to study the impacts of laminar shear stress and discharging situation on the zinc-electrode behaviors. It indicates on the condition of limited laminar shear stress at zinc anode surface, as the laminar shear stress increases, the passivation of zinc anode is reduced. The amount of zinc oxide deposition on the electrode surface decreases with the increasing of laminar shear stress, and the power-generation property is obviously improved. The zinc anode can expose a large amount of active area during the discharge process. When the laminar shear stress is greater than 120 dyn/cm2, the increase of laminar shear stress has no obvious effect on the reduced passivation anymore. It demonstrates the potential of utilizing microfluidic tool to screen and optimize the operational environments of zinc-electrode in flow battery and fuel cell.