Bifunctional Alloy/Solid-Electrolyte Interphase Layer for Enhanced Potassium Metal Batteries Via Prepassivation.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium (K) metal batteries offer advantages in cost and energy density but suffer from dendrite growth and environmental sensitivity.
• Effective interface engineering is crucial for stabilizing K metal anodes and enabling commercial development.

Purpose of the Study:

• To design and implement bifunctional layers for prepassivating the interface between current collectors and K metal.
• To improve K-ion flux accommodation, inhibit dendrite growth, and suppress parasitic reactions.

Main Methods:

• Fabrication of bifunctional layers comprising an O/F-rich Sn-K alloy and a preformed solid-electrolyte interphase (SEI).
• Characterization of the Sn-K alloy's potassiophilicity and the SEI layer's protective capabilities.
• Electrochemical testing of K metal batteries with the modified interface.

Main Results:

• The Sn-K alloy demonstrated strong potassiophilicity, guiding homogeneous K metal deposition.
• The preformed SEI layer effectively suppressed initial side reactions, leading to a stable KF-rich SEI.
• Achieved low nucleation overpotential (0.066 V), high Coulombic efficiency (99.1%), and long-term stability (>900 h).

Conclusions:

• Bifunctional layers provide an effective strategy for K metal deposition and protection, addressing key challenges in K metal batteries.
• This interface engineering approach enables high-voltage, high-energy, and high-power K metal batteries using Prussian blue analogue cathodes.
• The study presents a paradigm for passivating fragile interfaces in alkali metal anodes for advanced energy storage.