Cathode-solid electrolyte interface in solid-state batteries

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 and enabling the safe implementation of Li-metal anodes in an all-solid-state battery (SSBs) configuration. A major challenge in SSBs is to design cathodes with sufficient compliance so that high stresses are avoided when active particles swell or contract, in order to maintain contact upon charge and discharge. Commercial cathodes are strongly oxidising, and thus generally degrade solid electrolytes at interfaces, especially sulphide-based solid electrolytes. Ceramic coatings have been investigated to suppress reactivity, but the mechanical problems remain. A polymer, as a cathode particle coating, with the necessary combination of mechanical properties, adhesion, ionic conductivity and low interfacial impedance, could help maintain contact between the solid electrolyte and the cathode particles upon cycling while minimising its impact on rate capability.
In this project, the cathode/solid electrolyte interface will be studied as a function of charge state, cycling, current density, temperature, and pressure. The student will be trained on electrochemical characterisation (3-electrodes cells) and impedance spectroscopy, morphology studies by plasma-FIB SEM, sample thinning and TEM, operando X-ray tomography and XPS. Isostatic pressing will be combined with electrochemistry to establish the mechanical responses of composites. 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.