(Invited) Dynamic Plating/Stripping Behavior of Zn Anode in an Operating Aqueous Zn-Ion Battery

Abstract

To circumvent the fossil resource depletion and to reduce the carbon emission, electrochemical energy storage technique undergoes blooming developments over the past few decades. A promising candidate for electrochemical energy storage is the rechargeable Zn aqueous battery, which has the merits of rich Zn abundance, low cost, high safety, and environmental friendliness. Despite of enormous research and engineering investments, the practical implementation and deployment of Zn aqueous battery are still hindered by challenges concerning several different aspects of the electrochemical reaction involving Zn-ions. One of the main obstacles is that the Zn anode suffers from a low Coulombic efficiency, and the underlying mechanism is related with the non-ideal reversibility of the Zn plating/stripping process. The behavior of Zn plating and stripping is sophisticated and can be modulated by several co-existing and intertwined factors, including the electrode configurations, the charging/discharging protocols, and the composition of the electrolyte.For example, it has been demonstrated that the anode morphology can affect the dendrite growth. By fabricating Zn anode with a 3D sponge structure, the Ni-Zn cells could exhibit an improved cycle performance and a suppressed dendrite formation. Plating with high current density could exacerbate the electrochemical polarization and tends to form Zn dendrites. As a mitigation, the Zn dendrites can be dissolved by applying a small current during the stripping process. In addition, surface chemistry on anode plays a critical role in the Zn plating/stripping process. The reactions involving the solid-liquid interphase are often complicated and may vary depending on the electrolyte used. A holistic investigation of the structural, dynamic, and chemical features in Zn-ion batteries under operating conditions is key to the development of high-performance Zn-ion battery.In this talk, I will present our recent study using in-situ X-ray tomography and operando X-ray radiography to investigate the Zn plating/stripping behaviors in an in-house developed aqueous zinc-ion battery cell. We electrochemically plate Zn on a three-dimensional Cu foam and reveal how the electrode configuration and the local morphology collectively regulate the Zn plating behavior. Through advanced quantification and analysis of the tomographic data, we uncover that the Zn deposition in ZnSO4 electrolyte exhibits a substrate-curvature dependence. We further investigate how the current density would modulate the Zn plating using operando X-ray radiography. I will also briefly discuss the possibility of utilizing a novel tri-contrast x-ray imaging method to image dendric structures with better sensitivity and contrast.