Robust Pinhole-free Li₃N Solid Electrolyte Grown from Molten Lithium

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Lithium metal anodes offer high energy density but face challenges with reactivity and dendrite formation.
• Existing coatings often lack mechanical robustness, chemical stability, or sufficient ionic conductivity.
• An ideal coating is needed to ensure safety and performance in lithium metal batteries.

Purpose of the Study:

• To develop a novel, pinhole-free, mechanically robust, and ionically conductive coating for lithium metal anodes.
• To improve the electrochemical performance and safety of rechargeable lithium batteries.
• To address the limitations of current coating materials for lithium metal.

Main Methods:

• Synthesized α-Li3N film by reacting molten lithium foil with nitrogen gas.
• Characterized the film's morphology, structure, mechanical properties, and ionic conductivity.
• Tested the coating's stability and performance in Li|Li4Ti5O12 battery cells over 500 cycles.

Main Results:

• Generated a pinhole-free, ionically conductive α-Li3N film directly bonded to lithium metal.
• The film exhibited excellent mechanical robustness, withstanding bending and maintaining integrity during cycling.
• Achieved ionic conductivity of 5.2 × 10^-4 S cm^-1, promoting dendrite-free lithium plating/stripping.
• Demonstrated stable battery cycling for 500 cycles without capacity decay or increased hysteresis.

Conclusions:

• The novel α-Li3N coating effectively addresses key challenges in lithium metal anode technology.
• This coating enhances battery safety and longevity by preventing dendrite growth and electrolyte decomposition.
• The developed synthesis method offers a promising route for advanced lithium metal battery development.