Probing the Electrolyte-Dependent Zinc Deposition in Aqueous Zinc-Ion Batteries by in Situ Electrochemical Liquid-Cell TEM

Recently, zinc trifluoromethanesulfonate (Zn(OTf)2) has been widely used as a key component in zinc-ion battery electrolytes due to its superior performance. However, the early stages of zinc electrodeposition from Zn(OTf)2 remain unexplored by using in situ electrochemical liquid-phase transmission electron microscopy (EC-LPTEM). Here, we directly compare zinc electrodeposition in 0.1 M ZnSO4 and 0.1 M Zn(OTf)2 electrolytes using in situ EC-LPTEM, complemented by ex situ electrochemical tests on symmetric Zn∥Zn and V2O5∥Zn full cells. The results reveal distinct electrolyte-dependent differences in early stage nucleation, deposit morphology, and chemical composition. Notably, highly crystalline metallic zinc residues derived from the stripping process are identified in both electrolytes, indicating a common degradation pathway involving irreversible active material loss. This study provides mechanistic insights for designing advanced electrolytes that promote high reversibility, suppress side reactions, and mitigate dendrite formation in zinc-ion batteries.