H^{δ -}-H^{δ +} Comproportionation Enables Stable Li-N-H-F Solid Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Nitride compounds are early candidates for solid electrolytes (SEs).
• Key challenges include improving electrochemical stability without sacrificing Li-ion conductivity and Li metal compatibility.

Purpose of the Study:

• To synthesize a novel Li-N-H-F solid electrolyte with enhanced electrochemical stability and Li-ion transport.
• To investigate the structural and interfacial properties of the new material for all-solid-state batteries.

Main Methods:

• Synthesis of Li-N-H-F complex via comproportionation of LiH and NH4F.
• Density functional theory (DFT) calculations to analyze structural and electronic properties.
• Fabrication of solid electrolyte films via cold pressing.
• Electrochemical cycling tests of Li||Li, Li||TiS2, and Li||LiCoO2 cells.

Main Results:

• A Li-N-H-F complex (Li2+xNHFx matrix with dispersed LiF nanoparticles) was synthesized.
• DFT calculations revealed improved Li-ion pathways and reduced migration barriers due to F incorporation.
• In situ formed Li4NH/LiF interphases effectively suppressed interfacial side reactions.
• The Li4NH interphase demonstrated fast Li-ion migration and stability against Li metal.
• Stable cycling was achieved in Li||Li, Li||TiS2, and Li||LiCoO2 all-solid-state batteries using the developed SE.

Conclusions:

• The novel Li-N-H-F solid electrolyte offers a promising solution for enhancing electrochemical stability and performance in all-solid-state batteries.
• The self-limiting interphase formation is crucial for stable Li metal cycling.
• This material demonstrates potential for practical applications in next-generation energy storage devices.