Recent Progress of Advanced Functional Separators in Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium metal batteries (LMBs) offer high energy density but face challenges like dendrite formation and poor cycling stability.
• Separator modification is a promising strategy to overcome these limitations within existing LMB architectures.

Purpose of the Study:

• To review functional separators designed to address critical issues in LMBs, focusing on both anode and cathode challenges.
• To summarize strategies for mitigating dendrite growth and cathode degradation through advanced separator designs.

Main Methods:

• Review of literature on functional separators for LMBs.
• Classification of separators based on their function (anode protection, cathode stabilization, safety enhancement).
• Analysis of mechanisms like lithiophilic layers, ion channels, interphase formation, impurity scavenging, and shuttle effect inhibition.

Main Results:

• Functional separators can suppress lithium dendrite growth via lithiophilic coatings and uniform ion transport.
• Separators can stabilize the solid electrolyte interphase (SEI) layer through active agent release.
• Strategies are presented to prevent cathode degradation by scavenging acidic impurities, capturing transition metals, and inhibiting polysulfide shuttling.
• Flame-retardant and multifunctional separators are discussed for enhanced safety and performance.

Conclusions:

• Functional separators are crucial for advancing LMB technology by tackling key degradation pathways.
• The development of advanced separators is essential for realizing the full potential of high-energy-density LMBs.
• The principles of functional separator design may extend to other battery chemistries, indicating broad applicability.