Self-Evolving Interfacial Kinetic Highways via Reactive Separator Engineering for Durable Potassium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Potassium metal batteries (KMBs) face challenges with unstable interfacial chemistry, hindering practical deployment.
• Current thick, inert separators in KMBs limit energy density and dynamic interface regulation.

Purpose of the Study:

• To develop a reactive separator engineering strategy for KMBs.
• To create a robust, self-evolving anodic interphase for improved KMB performance.

Main Methods:

• Mechanistic screening identified intercalation compounds as superior separator modulators.
• Polypropylene separators were modified with intercalative WO3 to trigger in-situ formation of a KxWO3 interphase.
• Density functional theory calculations were used to analyze the interphase properties.

Main Results:

• The engineered KxWO3 interphase exhibits a low K+ migration barrier (0.12 eV), facilitating ion transport.
• A rigid-flexible coupling architecture buffers volume fluctuations, templating spatially graded interphase growth.
• K||Cu half cells showed low nucleation overpotential (17 mV at 0.2 mA cm-2).
• K||K symmetric cells achieved an ultralong lifespan (6000 h at 0.05 mA cm-2).
• KMBs demonstrated exceptional stability (>2500 h at 50 mA g-1) with high cumulative capacity.

Conclusions:

• Reactive separator engineering is a viable strategy for stabilizing KMBs.
• The self-evolving KxWO3 interphase significantly enhances KMB electrochemical performance and cycle life.