Solid glass electrolytes for Li-metal batteries

Lead Research Organisation: University of Oxford
Department Name: Materials

Abstract

The conventional Li-ion battery chemistry is approaching its physicochemical limit. High energy active materials need to be implemented to develop the high energy density, low-cost and safe batteries that can meet the requirements of the expanding electric vehicle market and empower novel applications such as electric flight. This could be achieved by replacing the organic liquid electrolyte with a solid electrolyte, enabling the safe implementation of Li-metal anodes.

Solid glassy electrolytes have attracted much attention mainly due to their advantages over the crystalline counterparts, namely isotropic ionic conduction, absence of grain-boundaries and associated resistance and ease of fabrication into films. In addition, the ion conductivity of amorphous glasses is generally higher than that of their crystalline counterparts because of their open structure.

Li-ion conducting glasses can be divided into two main categories: oxides and sulfides. Oxide glassy electrolytes are chemically stable and display a wide electrochemical stability window nevertheless their lithium-ion conductivity at room temperature is too low to be practical for high energy batteries (10E-6-10E-8 S/cm). Sulphide glasses, on the other hand, display high lithium-ion conductivities at room temperature (10E-3 - 10E-5 S/cm) thanks to the high polarisability of sulphide ions. Unfortunately, they can react with ambient moisture and generate the toxic hydrogen sulphide gas.

Oxy-halide glassy electrolytes derived from anti-perovskite lithium hydroxy halides (Li2OHX, X=Cl, Br) have recently shown potential in bridging the gap between the electrochemical stability of oxides and ionic conductivity of sulphides.

In this project the student will explore the synthesis and characterization (structural, physico-chemical and electrochemical) of oxy-halide solid glassy electrolytes, compatible with the lithium metal anode. The effect of composition and morphology on mechanical properties and ion transport will be investigated in detail. The mechanism of ion conduction will be explored both experimentally (solid-state NMR and electrochemical impedance spectroscopy) and by first-principle calculations. The lithium metal-solid electrolyte interphase will be probed by XPS (ex-situ, in-situ and operando), AFM and advanced electron microscopy techniques.

This project falls within the EPSRC Energy research area. The aim of this theme is for the UK to meet its environmental and energy targets.

The project is partially sponsored (DTP-CASE) and will be carried out in collaboration with Morgan Advanced Materials.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/T517811/1 01/10/2020 30/09/2025
2599358 Studentship EP/T517811/1 01/10/2021 30/09/2025