Mechanistic Understanding of Cathode–Electrolyte Interphases in Sulphide Solid-State Batteries

Sulphide solid electrolytes exhibit a narrow electrochemical stability window and decompose against high-voltage oxide cathodes, limiting the long-term stability of solid-state batteries. Although cathode coatings are widely proposed to mitigate these reactions, the mechanisms governing interphase formation and growth remain poorly understood. This project will investigate the chemistry and kinetics of cathode–electrolyte interphases in sulphide-based solid-state batteries using advanced operando and in situ diagnostics developed in our group.

Custom three-electrode cells will enable temperature-, pressure-, and state-of-charge-dependent electrochemical impedance spectroscopy (EIS) to extract mechanistic growth laws [1-3]. Interfacial chemistry will be studied using in situ XPS sputtering experiments, where argyrodite films are deposited while X-rays monitor the evolving composition under electrochemical bias [4]. Ex situ 4D-STEM analysis of FIB lift-outs, performed in collaboration with ePSIC, will resolve interphase nanostructure with minimal beam damage.

Model systems will include coated NMC811 and thin-film cathodes paired with Li₆PS₅Cl and related argyrodite electrolytes. By systematically varying coating chemistry and thickness, the project aims to establish design rules for stable cathode interfaces in high-energy solid-state batteries. The project funded, by the Faraday Institution and in collaboration with Nissan Motor will also include a three-month research internship with Nissan to explore the industrial relevance of interphase engineering strategies for next-generation automotive batteries.

This project is fully funded by a Faraday Institution studentship. The 4-year studentship is open to applicants with Home fees status only and it will cover course fees and pay a stipend of at least £20,780 per year.

Details on fees can be found on https://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other.... 

References
[1] Kotakadi et al., Joule (2025).
[2] Burton et al., Nature Communications (2025).
[3] Olbrich et al., ACS Electrochemistry (2025).
[4] Narayanan et al., Nature Communications (2022).