SnF₂-Catalyzed Lithiophilic-Lithiophobic Gradient Interface for High-Rate PEO-Based All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Polyethylene oxide (PEO)-based all-solid-state lithium metal batteries (ASSLMBs) face challenges with lithium dendrite growth and poor ion transport at high rates.
• Suboptimal interfacial chemistry and kinetics hinder the cycling stability and performance of ASSLMBs.

Purpose of the Study:

• To develop a stable and efficient solid electrolyte interphase (SEI) for high-rate ASSLMBs.
• To investigate the role of a lithiophilic-lithiophobic gradient SEI in suppressing dendrite growth and enhancing Li+ transport.
• To improve the overall performance and safety of ASSLMBs.

Main Methods:

• In situ formation of a SnF2-catalyzed lithiophilic-lithiophobic gradient SEI (SCG-SEI) composed of Li$_{x}$Sn$_{y}$/LiF-Li$_{2}$O.
• Characterization of the SEI layer's structure, composition, and properties.
• Electrochemical testing of symmetrical cells and full cells (LiFePO$_{4}$ and LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_{2}$ cathodes) under various conditions.

Main Results:

• The SCG-SEI features a LiF-Li$_{2}$O rich upper layer for ionic conductivity and a Li$_{x}$Sn$_{y}$ alloy layer to reduce nucleation overpotential and promote electron transport.
• Achieved over 46.7-fold and 3.5-fold improvements in lifespan and critical current density of symmetrical cells, respectively.
• Demonstrated over 1000 cycles with 80.0% capacity retention at 5 C in LiFePO$_{4}$-based ASSLMBs and excellent performance/safety at 100 °C.

Conclusions:

• The developed lithiophilic-lithiophobic gradient interfacial chemistry is crucial for high-rate and safe ASSLMBs.
• The SCG-SEI effectively mitigates dendrite growth and enhances Li+ kinetics, paving the way for practical applications.
• This strategy offers a promising approach for designing next-generation solid-state batteries.