Diagnosing the current-density-dependent zinc electrodeposition by in-situ liquid cell TEM

Session

Poster Session One

Authors

Dr. Zixuan Li (1), Prof. Peter Bruce (1), Dr. Alex Robertson (2)

Affiliations

1. University of Oxford
2. University of Warwick

Keywords

Liquid cell TEM, Zn dendrite, Zn electrolyte

Abstract text

In this work, by in situ liquid cell TEM, the initial nucleation process of Zn seeds, the later growth, and the dissolution of Zn in Zn electrolyte are visualised; also the influence of current density to the Zn deposition including morphology and crystal orientation are studied. 

Aqueous zinc-ion batteries are compelling next-generation energy storage devices due to the merits of zinc metal including mineral abundance, stable electrochemical activity, low cost, and environmental friendliness. However, one of the issues leading to zinc-ion battery capacity decay is zinc dendrite growth which may puncture the separator and generate “dead zinc”. Different kind of method like electrolyte manipulation, anode surface modification and the structure design for zinc anode have been adopted to achieve flat and uniform zinc anode. Since the final morphology of Zn anode largely depends on the initial nucleation stage, understanding the initial nucleation and further growth of Zn electrodeposition is of great importance. 

This work comprehensively studied the initial nucleation process of zinc seeds under different deposition conditions (current density and capacity) by liquid cell TEM and the postmodern morphology of Zn anode by SEM. We found that in the most widely used zinc electrolyte ZnSO₄, the nuclei density of deposited zinc will increase with the increasing current density from 1 mA cm^-2 to 120 mA cm^-2. It’s found that a high current density like 120 mA cm^-2 can generate more nuclei active sites, thus uniform surface of Zn is achieved. We attribute it to the thermodynamics factor, which means high current density can enable high energy nucleation seeds while low current density can only active low energy nucleation sites like grain boundary. The crystallographic orientation of zinc texture behaviour was also studied by XRD with the indicator of the peak intensity ratio of (002)Zn and (101)Zn. The deposited zinc at ultrahigh current density 120 mA cm^-2 shows the highest I002:I101, which means the surface is (002) plane dominated. Since (002)Zn is parallel to the electrode, more (002) plane indicates the electrode is more uniform and flatter, which is consistent with the previous result. This work not only unravels the nucleation behaviour of zinc from low current density to high current density, but also could provide effective strategy to achieve long-term zinc-ion battery.