Identification of failure mechanisms in Ni rich cathodes relevant to the safety of a battery cell

This project offers the opportunity to study the safety behaviour of Ni rich cathode materials at different SoH's and identify changes/weaknesses in the material with age. The primary focus is to analyse how safety characteristics evolve with the lifetime of the cathode material (focus on commercially available NMC 811) conducting abusive tests at different SoH's. Macro-, micro- and nano-CT measurements will inform in-situ microstructural changes within the battery, in situ XRD will elucidate structural changes in the cathode materials. Post-test analysis on the cathode materials - conducted using the facilities at JM (potentially supported by the University partner to fill in gaps) - will be undertaken to investigate compositional and structural changes at both the electrode's surface and the electrolyte. In tandem, electrochemical testing could be undertaken, alongside a portfolio of additional techniques including calorimetry, colorimetry thermal imaging and acoustic measurements to inform SoH.
We will pursue parallel work streams on proprietary and model materials, the latter providing a platform for technique development and wider opportunities for publication without compromising IP, as well as alignment to the Faraday Institution projects, providing opportunities for wider correlative studies.
Main Objectives:
- Link micro/structural changes in the electrodes with changes in the electrochemical and ultimately the safety behaviour of the cells.
- Understand the influence of physical product features on safety properties (e.g. primary and secondary particle size, density).
- Develop a non-destructive test to determine the SoH of a cell.
- Develop a strategy to further improve the safety performance of eLNO materials by using learnings to inform product development.
Year 1: Development of a strategy and a detailed test plan for pouch cells including electrochemical characterisation (e.g EIS, GITT or PITT) and abusive safety tests. Abusive tests include, amongst others, accelerated rate calorimetry (ARC), nail penetration, overcharging and crush testing. Conduct first electrochemical abusive tests on pouch cells, post mortem X-ray imaging and tear down analysis. Establish links with Faraday Institution projects.
Year 2: Development methods for correlated thermal/mechanical abuse tests with operando X-ray imaging. Systematic studies of NMC vs eLNO materials to determine safety and SoH characteristics, and development/implementation of accelerated stress tests. Beam time applications where appropriate, focussing on non-proprietary materials.
Year 3: Correlation between chemical/morphological evolution in response to AST's and establish links to durability/failure. Establish platform capability for evaluation of safety performance for materials across time/length scales. Translation of synchrotron tools to lab environment.
Year 4: Dissemination of findings, contribution to new standards/methodologies for cell safety.
This project builds on, and is complementary to, an existing PhD project in collaboration with UCL (Drasti Patel is currently developing imaging and calorimetry techniques for JM battery materials): it tackles open questions relating to battery safety, but also strongly profits from the fundamental work which has already been conducted.