Description
Microfluidics provides exceptional control over experimental conditions in electrochemistry, particularly regarding mass transfer and the local distribution of current. This precise control over surface phenomena and transport opens new opportunities for studying metal deposition processes, electrode morphology, and optimizing charge cycles in batteries.
In this work, we leverage microfluidics to investigate the charging behavior of a zinc-air redox battery. The originality of our approach lies in the development of a quantitative charging model based on data extracted from microfluidic experiments. The interfacial dynamics are measured at high electrolyte flux in a microfluidic device using electrodes with a small surface area. The evolution of the deposit surface is monitored and modeled using in-operando techniques based on linear sweep voltammetry (LSV). In the case of zinc, employing the Cachet model, the LSV curve at low potential is sensitive to the morphological state of the electrode, providing a direct measure of the evolution of its surface area.
Based on these measurements, we construct a quantitative model that couples mass transport, interfacial kinetics, and deposit dynamics, enabling the prediction of cell voltage under various experimental conditions, such as electrode size and electrolyte flow rate.
This framework allows us to examine the effect of segmented electrodes on energy efficiency and deposit morphology. Our results demonstrate that optimal electrode spacing significantly reduces dendrite formation and lowers the energy required for charging. For example, at a current density of 30 mA·cm⁻² and a flow rate of 0.125 cm·s⁻¹, no dendrites form when four electrodes are spaced 8–13 mm apart, whereas dendrites appear when electrodes are connected or spaced only 3 mm apart. These findings show that controlling mass transfer, enabled by microfluidics, allows precise manipulation of deposit morphology and optimization of battery energy efficiency.
In conclusion, microfluidics represents a powerful tool for studying and modulating local electrochemical phenomena, with direct applications in the design of safer and more efficient batteries. Our work on the zinc-air battery demonstrates that precise control of charging conditions and electrode segmentation not only prevents dendrite formation but also reduces the energy required for charging. This highlights the potential of microfluidic approaches for enhancing battery performance, optimizing energy efficiency, and guiding the development of advanced electrochemical storage systems.