Correlating Buffering Agents' Premier pH with Interface Stability Toward Long-Term Zn Metal Anodes.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous zinc batteries face challenges from hydrogen evolution reactions (HER) and dendrite growth due to fluctuating electrolyte pH.
• Buffering agents are used to stabilize pH, but their initial pH's impact on interface stability is understudied.

Purpose of the Study:

• To investigate the correlation between the initial pH of buffering agents and the interface stability in aqueous zinc metal batteries.
• To determine the optimal initial pH for buffering agents to enhance battery performance.

Main Methods:

• Two types of buffering agents (single amphoteric and conjugate acid-base pairs) were tested with varying initial pH values.
• Zinc metal anode interface stability and battery cycling performance were evaluated.

Main Results:

• An optimal initial pH of 3.3 was identified for buffering agents, maximizing Zn metal anode lifetime.
• Low pH (<3.3) led to excessive HER, while high pH (>3.3) caused passivation layer issues.
• The optimized pH condition resulted in 99.61% average Coulombic efficiency over 1500 cycles at 5 mA cm⁻², outperforming pristine electrolytes (345 cycles).

Conclusions:

• The initial pH of buffering agents critically influences interface stability in aqueous zinc batteries.
• An optimized initial pH of 3.3 significantly enhances cycling stability and Coulombic efficiency.
• Stable Zn/activated carbon full batteries were achieved for over 15,000 cycles with the optimized buffering strategy.