Mapping Chemical, Ionic and Electronic Properties of High Capacity Cathode Materials

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The development of Li-ion batteries (LIBs) with increased energy density and lower cost is a key requirement for the adoption of electric vehicles and reduction in carbon emissions in the global transport sector. Current technology is largely limited by the cathode active material, meaning improvements here will have significant benefits to performance. Nickel-rich cathode materials promise higher capacities, whilst also reducing cost due to their lower cobalt content. However, these materials suffer from accelerated capacity fading, that limits battery lifetime and consequently their commercial viability. To overcome this challenge and develop improved materials requires an understanding of the origins of this capacity fade, including how the structure and chemistry of these materials change as they are repeatedly charged and discharged. This project aims to apply multimodal imaging capabilities to reveal the interplay between local chemical and structural properties of high capacity cathode materials, and their electronic and ionic conductivities. Key to this will be spatially resolving how these properties vary within individual cathode particles at different stages of cycling and after different number of cycles, providing insights into the key degradation mechanisms responsible for capacity fade in these materials. This will involve X-ray spectromicroscopy and electrochemical scanning probe techniques that can achieve spatial resolutions from nanometres up to microns and detect variations in Lithium content, transition metal oxidation state, and electronic and ionic conductivities. The focus will be on studying realistic electrode materials already used as part of a larger Faraday Institution project on battery degradation and these will be electrochemically cycled following established protocols. Methods will be developed for sectioning these samples under inert environments to produce the flat cross-sections needed to get the most information from the proposed spatio-chemical imaging techniques. The understanding developed using these samples will inform the design of cathode materials and cycling protocols to help extend the life of Li-ion batteries.This project falls within the EPSRC research areas of Energy Storage and Analytical Science, where advanced spectromicroscopy techniques will be used to study the correlation between chemical, electronic and ionic properties in battery materials. This will include the use of X-rays methods available at Diamond light source and other international facilities.Faraday funded student