Researchers at Oak Ridge National Laboratory (ORNL) have developed a thin film, highly conductive solid-state electrolyte made of a polymer and ceramic-based composite for lithium metal batteries.
The electrolyte’s novel design is a three-dimensional interconnected structure that can provide mechanical robustness and high lithium ionic conductivity at room temperature.
The key to improving density in solid-state batteries is in developing a powerful, thin, solid electrolyte that is also scalable.
To achieve this, the team combined the advantages of solid polymer electrolytes (flexible and low cost but with low conductivity) with ceramic electrolytes (better conductivity but are too brittle to process) to form a thin composite film.
ORNL’s Xi Chen said: “The film was formed by partially sintering a three-dimensionally interconnected ceramic structure and the polymer filled the pores to make a robust membrane.”
The team initially formed a doped-lithium aluminum titanium phosphate ceramic thin film with thickness of ~25μm by aqueous spray coating.
The film was then partially sintered to form a three-dimensionally interconnected structure with a dense backbone.
It was then backfilled with a crosslinkable poly(ethylene oxide) (PEO)-based polymer electrolyte.
The scientists reported the composite had a ceramic loading of 77wt% (61 vol%) and an ionic conductivity of 3.5 × 10 -5 S/cm at 20°C with an activation energy of 0.43 eV.
The team said the main ion transport pathway was through the ceramic network, predicted by modelling and verified by experiments.
Because of the interconnected structure of the ceramic, the composite electrolyte exhibited much improved mechanical strength.
Image: A thin film solid-state electrolyte with a three-dimensionally interconnected structure was fabricated by ORNL researchers. The structure increased conductivity through the ceramic base. Credit: Xi Chen/Oak Ridge National Laboratory, U.S. Dept. of Energy