Thin film electrolytes for novel lithium-ion battery designs

Oxford University is one of the founder members of the Faraday Institution (https://faraday.ac.uk), the UK's new flagship programme for battery science and technology. Rechargeable lithium-ion batteries have revolutionized the portable electronics industry because of their high energy density and efficiency, and are now widely deployed in electric vehicles. However, they suffer from significant safety and reliability issues, many of which are related to the use of flammable liquid electrolytes. There is a world-wide race to design and manufacture solid-state electrolyte materials that could resolve some of these problems. A range of oxide, phosphate and sulphide compounds have rather lower conductivities than liquid electrolytes, but show promise for use in prototype all solid-state battery designs if the thickness of the electrolyte can be reduced. The interfaces between electrodes and electrolytes are also well known to be electrochemically unstable, and strategies to modify the interfacial properties are being widely explored.

This project will use pulsed laser deposition techniques to deposit thin films that modify the chemistry of the interfaces between electrode and electrolyte materials in order to improve the cycling performance of prototype solid state battery designs. While thin film interlayers are attracting a lot of attention In laboratories worldwide, most of the reported work is very empirical - "we add a layer of XXX and the cycling performance improves". The novelty of the research methodology that will be applied in this project lies in the focussed material science approach to identify and control exactly what is being deposited and then to characterise the interfacial regions after cycling to understand the chemical and morphological changes that occur. The first stage of the project will study the influence of the deposition parameters on the phase, microstructure and mechanical properties of the films using XRD and electron microscopy techniques to establish the optimised growth conditions, and the electrochemical performance of promising structures will be measured. Facilities for the growth of complete thin film cells are available (funded by the Faraday Institution and Royce Institute). In the second stage of the project, a combination of more advanced electron microscopy techniques and in-operando synchrotron based tools (XPS/XAS/XRD) have been selected in order to determine the response of the interfacial region to current transfer. In this way we will build up a mechanistic understanding of how interfacial layers can influence the electrochemical performance of thin film battery structures, and be able to propose methods for optimising properties.

This project falls within the EPSRC research area of Energy Storage.