Enhanced Surface Interactions Enable Fast Li⁺ Conduction in Oxide/Polymer Composite Electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Composite polymer electrolytes are crucial for advanced batteries.
• Lithium-ion (Li+) conductivity in these electrolytes is often limited by ceramic fillers.
• Li+-conducting oxides are typically preferred over Li+-insulating oxides.

Purpose of the Study:

• To investigate the potential of Li+-insulating oxides as ceramic fillers in polymer electrolytes.
• To explore the mechanism of Li+ transport enhancement by these insulating oxides.
• To evaluate the performance of resulting composite electrolytes in all-solid-state Li-metal cells.

Main Methods:

• Fabrication of poly(ethylene oxide) (PEO)-based composite electrolytes using Li+-insulating oxides (Gd0.1Ce0.9O1.95 and La0.8Sr0.2Ga0.8Mg0.2O2.55).
• Measurement of Li+ conductivity using electrochemical impedance spectroscopy.
• Analysis of Li+ ion environments using Li solid-state Nuclear Magnetic Resonance (NMR).
• Assembly and testing of all-solid-state Li-metal cells.

Main Results:

• Achieved Li+ conductivity above 10^-4 S cm^-1 at 30°C with both types of Li+-insulating oxides.
• NMR studies revealed an increase in Li+ ions in the mobile A2 environment (>10%).
• Observed strong interactions between Li-salt anions and oxide surface oxygen vacancies facilitated Li+ transport.
• Demonstrated small interfacial resistance and good cycling performance in Li-metal cells at 35°C.

Conclusions:

• Li+-insulating oxides with high oxygen vacancy concentrations can effectively enhance Li+ conductivity in PEO-based electrolytes.
• The enhanced conductivity is attributed to improved Li+ ion mobility and interfacial interactions.
• These composite electrolytes show promise for developing stable and high-performance all-solid-state Li-metal batteries.