Thin film solid electrolyte batteries

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This project is part of a new activity on the deposition and characterisation of solid state electrolytes (SSE) in Li-ion batteries, and will benefit from close interaction with the SOLBAT project of the Faraday Institution (https://www.solbat-faraday.org/). The project will explore reliable methods for the growth of thin films of promising electrolyte materials by sputtering and pulsed laser deposition (PLD). The choice of materials to study will be informed by other projects in the SOLBAT collaboration, and will include oxides with the garnet structure and possibly sulphides, and other novel materials as they are discovered. A wide range of parameters (substrate temperature, gas phase pressure, laser/sputter power and composition) can be varied to optimise the ionic conductivity and the critical, and hard to control, problem of ensuring film uniformity. These properties will be measured initially by routine electrochemical impedance spectroscopy (EIS) measurements, phase purity by XRD, and microstructural analysis and uniformity by SEM. The properties of amorphous thin film materials will also be explored since there is very recent evidence that these can have surprisingly good ionic conductivities. PLD processes are ideal for this work, with a very high degree of control over the degree of crystallinity being readily provided by changing deposition parameters. These amorphous electrolytes may also offer interesting opportunities to manage the serious problem of Li dendrite growth in all kinds of SSE battery designs. Once reproducible growth processes have been established, a second stage of the project will be to study the electrolyte/electrode interactions that control the performance of complete batteries. The methodology employed will be the sequential deposition of electrode and electrolyte materials, and electron microscopy and secondary ion mass spectroscopy (SIMS) techniques to study chemical and morphological interactions after heat treatments, and later on, after current cycling of symmetric structures. In-situ and in-operando experiments on multi-layered samples and complete battery structures using the Diamond light Source will also be explored. The overall aim of the project is to offer to the SOLBAT project a route to prototype battery manufacture based on a thin film strategy. There is no current work in the UK, and very little published internationally, on thin film electrolytes, and none at all on interfacial reactions and degradation mechanisms in these materials, and so the proposed research methodology has a high degree of novelty. The student will work closely with other members of the SOLBAT team, in Oxford and in partner universities, and so gain valuable experience with complementary electrochemistry and mechanical measurement techniques. This project falls within the EPSRC Energy Storage research area in the Energy Theme.