Highly Reversible Zinc Metal Anode in a Dilute Aqueous Electrolyte Enabled by a pH Buffer Additive

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc-ion batteries offer safety and cost benefits but suffer from dendrite growth and side reactions on the zinc anode.
• These issues limit the practical application and long-term stability of zinc-based energy storage devices.

Purpose of the Study:

• To introduce ammonium dihydrogen phosphate (NHP) as a multifunctional additive for aqueous zinc-ion batteries.
• To investigate NHP's ability to regulate zinc deposition and suppress undesirable side reactions at the anode.

Main Methods:

• Electrochemical testing of zinc plating/stripping in Zn//Zn and Zn//Cu symmetric cells.
• Evaluation of full cells, including Zn//MnO2 batteries and Zn//active carbon (AC) capacitors, with and without NHP.
• Analysis of the mechanism of NHP's action on the zinc anode surface.

Main Results:

• NHP additive promotes uniform zinc deposition and suppresses dendrite formation.
• NH4+ ions form a protective layer on the zinc surface, blocking water contact.
• NHP helps maintain stable pH at the electrode-electrolyte interface, enhancing reversibility.
• Improved electrochemical performance was observed in Zn//Zn, Zn//Cu, Zn//MnO2, and Zn//AC devices.

Conclusions:

• Ammonium dihydrogen phosphate (NHP) is an effective additive for improving the stability and performance of aqueous zinc-ion batteries.
• NHP offers a general strategy to control zinc plating/stripping and mitigate side reactions in aqueous electrolytes.
• This research paves the way for safer and more efficient aqueous zinc-based energy storage systems.