An electron-blocking interface for garnet-based quasi-solid-state lithium-metal batteries to improve lifespan

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Garnet oxides like Li6.4La3Zr1.4Ta0.6O12 (LLZTO) are promising solid electrolytes for solid-state lithium metal batteries.
• Traditional interface layers fail to prevent electron migration, leading to lithium dendrite penetration and battery failure.

Purpose of the Study:

• To develop a highly electron-blocking interlayer for LLZTO solid electrolytes.
• To enhance the stability and cycle life of solid-state lithium metal batteries.
• To investigate an integrated strategy for high-performance quasi-solid-state lithium metal batteries.

Main Methods:

• Deposition of a potassium fluoride (KF) interlayer on LLZTO.
• In-situ transformation of KF to KF/LiF upon reaction with lithium metal.
• Screening of an ionic liquid (LiTFSI in C4mim-TFSI) for wetting LLZTO|LiNi0.8Co0.1Mn0.1O2 (NCM) interfaces.
• Electrochemical testing of Li symmetric cells and Li|KF-LLZTO|NCM full cells.

Main Results:

• The KF/LiF interlayer effectively blocked electron leakage and inhibited lithium dendrite growth.
• Li symmetric cells demonstrated long cycle lives of ~3000 hours at 0.2 mA cm⁻² and >350 hours at 0.5 mA cm⁻².
• Li|KF-LLZTO|NCM cells achieved a specific capacity of 109.3 mAh g⁻¹, 3500 cycles, 72.5% retention at 2C, and 99.99% average coulombic efficiency.

Conclusions:

• The KF interlayer provides a simple and effective method to improve the performance of garnet oxide-based solid-state lithium metal batteries.
• This integrated strategy enhances interfacial stability and suppresses dendrite formation.
• The developed quasi-solid-state batteries show potential for high energy density and long-term cycling stability.