A Lewis Acid-Base Cooperative Separator Stabilizing Electrolytes in Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Stable solid electrolyte interphase (SEI) formation is crucial for lithium metal battery (LMB) longevity.
• Controlling electrolyte decomposition, particularly with LiPF₆-based electrolytes, remains a challenge for high-temperature battery operation.

Purpose of the Study:

• To design a novel separator that suppresses LiPF₆ electrolyte decomposition.
• To promote the formation of a stable, LiF-rich SEI and cathode electrolyte interface.
• To enhance the high-temperature cycling stability of lithium metal batteries.

Main Methods:

• Development of a cooperative Lewis acid-base aramid nanofibers/poly(ethylene-co-acrylic acid) (ANFs/EAA) separator.
• Investigation of the separator's role in suppressing PF₅ formation and reactivity.
• Assembly and testing of LiFePO₄||Li cells using the developed separator at elevated temperatures (60 °C).

Main Results:

• The ANFs/EAA separator effectively suppressed LiPF₆ electrolyte decomposition.
• A LiF-rich SEI and cathode interface were promoted, enhancing interfacial stability.
• Cells with ANFs/EAA separators achieved over 200 cycles at 60 °C, demonstrating ≈2.2 times longer stability than PE separators.
• Significantly improved high-temperature (50-70 °C) cycling performance compared to previous studies.

Conclusions:

• The Lewis acid-base cooperative separator provides an effective strategy for stabilizing LiPF₆-based electrolytes.
• This separator engineering approach enables robust cycling of LMBs at high temperatures.
• The ANFs/EAA separator offers a promising solution for enhancing the safety and lifespan of lithium metal batteries.