Highly Reversible Zn Anodes through a Hydrophobic Interface Formed by Electrolyte Additive

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc ion batteries face instability due to hydrogen evolution and dendrite growth during zinc plating/stripping.
• These interfacial issues at the electrolyte/electrode hinder the reversibility and lifespan of zinc anodes.

Purpose of the Study:

• To enhance the stability and reversibility of zinc anodes in aqueous zinc ion batteries.
• To investigate the effect of a novel hydrophobic electrolyte additive on the zinc plating/stripping process.

Main Methods:

• Introduction of a hydrophobic group as an electrolyte additive in aqueous zinc sulfate electrolytes.
• Testing of zinc//zinc symmetric batteries and zinc//titanium asymmetric cells.
• Evaluation of Zn//MnO2 full batteries to assess performance.

Main Results:

• The hydrophobic additive effectively excludes free water from the zinc anode surface, minimizing water-induced side reactions.
• Optimal electrolyte (2 M ZnSO4 with 2 g·L-1 Tween-85) demonstrated suppressed hydrogen evolution and improved cycling stability.
• Zinc//zinc symmetric batteries achieved over 1300 hours of stable cycling, with high performance at 5 mA·cm-2 and 5 mAh·cm-2.
• Zinc//titanium cells showed an average Coulombic efficiency of 98.11% after 300 cycles.
• Zn//MnO2 full batteries maintained 88.6% capacity retention after 1000 cycles.

Conclusions:

• The hydrophobic electrolyte additive significantly improves the stability and Coulombic efficiency of aqueous zinc anodes.
• This approach offers a promising strategy for developing high-performance and long-lasting aqueous zinc ion batteries.