Self-Assembled Monolayer in Hybrid Quasi-Solid Electrolyte Enables Boosted Interface Stability and Ion Conduction

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Hybrid quasi-solid electrolytes (HQSE) face challenges due to complex inorganic solid electrolyte (ISE) and liquid electrolyte (LE) interactions, impacting interface stability and ionic conductivity.
• Investigating the influence of ISE surface modification on ionic conductivity is crucial for developing advanced battery technologies.

Purpose of the Study:

• To improve the interface stability and ionic conductivity of hybrid quasi-solid electrolytes (HQSE) by modifying the surface of Li$_{6.4}$La$_{3}$Zr$_{1.4}$Ta$_{0.6}$O$_{12}$ (LLZTO) inorganic solid electrolyte.
• To explore the mechanisms behind enhanced ionic conduction and interfacial stability in the modified HQSE system.

Main Methods:

• Fabrication of a self-assembled monolayer (SAM) using 4-chlorobenzenesulfonic acid (CBSA) on LLZTO surfaces.
• Incorporation of the modified LLZTO into a PEGDA-based in situ polymerized HQSE.
• Electrochemical characterization, including ionic conductivity and transference number measurements.
• Advanced characterization using density functional theory (DFT), Raman spectra, and ⁷Li solid-state nuclear magnetic resonance.

Main Results:

• The CBSA-modified LLZTO significantly improved LLZTO/LE interface stability and optimized solvation structure.
• Achieved favorable ionic conductivity of 1.19 mS·cm^-1 and an increased Li⁺ transference number of 0.647.
• Demonstrated excellent long-term cycling stability with no short-circuits in Li|SAM-HQSE|Li cells after 1000 hours.
• Achieved high capacity retention in LFP|SAM-HQSE|Li and LFP|SAM-HQSE|Graphite pouch cells.

Conclusions:

• The SAM strategy effectively enhances the surface micro-environment of LLZTO, boosting and homogenizing Li⁺ conduction in HQSE.
• This facile approach offers a promising pathway for constructing stable and high-performance hybrid quasi-solid electrolytes for advanced lithium-ion batteries.