Manipulating Zn anode reactions through salt anion involving hydrogen bonding network in aqueous electrolytes with PEO additive

Abstract The reaction kinetics, reversibility and long-term stability of Zn anodes are crucial for rechargeable aqueous Zn batteries. Polymer electrolyte additives are low cost and effective to modify the deposition behavior of Zn anodes. Here, an interesting phenomenon appears that cycling stability and Coulombic efficiency of Zn anodes are improved by PEO additive in dilute aqueous electrolytes with different Zn salts, while the overpotential and long-term stability of Zn anodes vary significantly with different anions. Systematic electrochemical analysis coupled with NMR and MD simulation was performed to reveal the crucial role of salt anion in tuning the specific solvation structures and hydrogen bonding network of aqueous electrolytes with PEO additive, and interfacial double layer capacitance structures. The reaction kinetics and stability of Zn anodes were, therefore, intensively tuned by salt anions in aqueous electrolytes with PEO additives. The cycle life of Zn anode can be improved by 7–10 times with significantly reduced overpotential in bulky anion such as TFSI- based aqueous electrolyte than compact anion such as SO42- in PEO containing aqueous electrolytes. This work provides useful and low-cost concepts to effectively improve Zn anodes reaction dynamics and cycle life by choosing optimal electrolyte salts and additives.