Correlative operando and cryogenic microscopy of nanoscale electrochemical interfaces
File(s)
Author(s)
Mulcahy, Neil
Type
Thesis or dissertation
Abstract
The performance and safety of lithium-ion batteries are governed by processes occurring at the electrode–electrolyte interface, including solid–electrolyte interphase (SEI) formation, alloying reactions, and degradation phenomena. Understanding these processes requires characterisation of interfaces in their native state. However, conventional post-mortem preparation methods alter liquid–solid interfaces through electrolyte removal and drying. Existing approaches capable of preserving these interfaces fall into two categories: operando liquid-based microscopy reveals dynamic interfacial evolution but provides limited compositional information, whereas cryogenic microscopy preserves and resolves nanoscale chemistry and structure but cannot independently capture the preceding electrochemical evolution. Consequently, direct mechanistic correlation between interfacial dynamics, chemistry, and electrochemical behaviour remains challenging.
This thesis develops and applies correlative operando–cryogenic microscopy workflows that directly connect dynamic electrochemical processes with preserved nanoscale composition and structure within the same electrochemical system. A cryogenic methodology was established to prepare and transfer liquid–solid interfaces from MEMS-based liquid-cell platforms for cryogenic atom probe tomography (cryo-APT) and cryogenic electron microscopy while maintaining near-native states. The workflow enabled the first cryo-APT analysis of a frozen liquid–solid interface prepared from a MEMS nanochip.
Application of the workflow to a model Pt electrode–Li electrolyte interface revealed direct relationships between heterogeneous lithium deposition, SEI evolution, and electrode degradation during cycling. Correlative cryo-APT identified carbonate-rich interphases and lithium enrichment associated with unstable deposition behaviour and irreversible capacity loss. Integration of in-situ synchrotron hard X-ray nanoprobe spectroscopy further resolved alloy phase transformations from Li₂Pt to LiPt and correlated these changes with interphase evolution from carbonate-rich to LiF-rich compositions and improved electrochemical reversibility.
Overall, this work establishes a correlative operando–cryogenic framework that links electrochemical evolution to preserved nanoscale chemistry and structure, enabling mechanistic insights inaccessible to individual techniques and providing a foundation for the study and design of next-generation electrochemical energy storage materials.
This thesis develops and applies correlative operando–cryogenic microscopy workflows that directly connect dynamic electrochemical processes with preserved nanoscale composition and structure within the same electrochemical system. A cryogenic methodology was established to prepare and transfer liquid–solid interfaces from MEMS-based liquid-cell platforms for cryogenic atom probe tomography (cryo-APT) and cryogenic electron microscopy while maintaining near-native states. The workflow enabled the first cryo-APT analysis of a frozen liquid–solid interface prepared from a MEMS nanochip.
Application of the workflow to a model Pt electrode–Li electrolyte interface revealed direct relationships between heterogeneous lithium deposition, SEI evolution, and electrode degradation during cycling. Correlative cryo-APT identified carbonate-rich interphases and lithium enrichment associated with unstable deposition behaviour and irreversible capacity loss. Integration of in-situ synchrotron hard X-ray nanoprobe spectroscopy further resolved alloy phase transformations from Li₂Pt to LiPt and correlated these changes with interphase evolution from carbonate-rich to LiF-rich compositions and improved electrochemical reversibility.
Overall, this work establishes a correlative operando–cryogenic framework that links electrochemical evolution to preserved nanoscale chemistry and structure, enabling mechanistic insights inaccessible to individual techniques and providing a foundation for the study and design of next-generation electrochemical energy storage materials.
Version
Open Access
Date Issued
2026-03-09
Date Awarded
2026-07-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Conroy, Michele A.
Ryan, Mary P.
Sponsor
Engineering and Physical Sciences Research Council
Grant Number
EP/V038044/1
Publisher Department
Department of Materials
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)