Probing the chemical degradation of cathode material interfaces in Li-ion Batteries

For future generations of lithium ion batteries to be implemented in electric vehicles, significant improvements in their lifetime and power densities are required. One of the most important aspects in achieving a long battery lifetime is the stability of the cathode materials (positive electrode). Over many charge-discharge cycles or when operated under extreme temperatures, undesirable side reactions occur at the surface of these materials such as electrolyte decomposition, transition metal dissolution and gas evolution. Current techniques to look at these electrode-electrolyte interfaces must be performed after the battery has been disassembled, due to the major challenge of accessing such buried interfaces. However, such approaches are unreliable as battery interfaces are usually highly reactive and liable to change during disassembly and transfer to the measurement system.

This project aims to investigate the changes occurring at interfaces between the cathode (positive electrode) and electrolyte in Li-ion batteries during operation. This will make use of novel electrochemical cells that incorporate thin membranes through which hard X-ray photoelectron spectroscopy (HaXPES) and X-ray Absorption Spectroscopy (XAS) can be performed. It will also use a specially designed chamber for assembling and disassembling batteries in a vacuum environment that can be directly connected to surface-sensitive characterisation tools. These approaches will be used to reveal the reversible and irreversible reactions occurring, such as the formation of surface layers, transition metal dissolution and the subsequent plating of these species onto the anode (negative electrode). Application-relevant battery materials will be studied to obtain novel insights about their interfacial stability, and this understanding will inform the design of cathode materials and cycling protocols to help extend the life of Li-ion batteries. The use of new characterisation tools will also help demonstrate the capabilities these can provide to the battery research community.


This project is linked with Johnson Matthey and will involve work with both the Battery Materials and Advanced Surface Characterisation Groups at Johnson Matthey's Technology Centre. In situ and operando X-ray measurements will be performed at Diamond Light Source and other international synchrotron facilities. This project falls within the EPSRC research areas of Energy Storage and Physical Sciences, where advanced characterisation techniques will be used to study chemical changes occuring in battery materials.