The Department for Transport of UK government announced to ban petrol and diesel vehicles by 2030 to facilitate Net Zero strategy. Being a major part of transportation electrification, the electric vehicle (EV) market is growing quickly; there are 190,727 new registrations of pure-EVs in 2021, 76.3% increase compared to 2020. Despite such success, the driving range and fast charge capability of EVs are recognised as predominant factors limiting further market penetration. Unfortunately, the physics of these requirements results in a trade-off of the lithium-ion battery design strategy. For instance, cells with high energy density provide maximum range but cannot deliver fast charging, because thicker electrodes suffer more acutely from the concentration polarisation across the electrode due to the slow ionic transport. Likewise, cells with high power density are capable of fast charging, but suffer from low mileage. More impetus in fundamental studies on physical processes of battery and the interplay between microstructure and performance are needed to eliminate range anxiety and charge-time trauma of EVs. Graphite/silicon composite electrode is regarded as one of the most promising candidates for next-generation automotive LiBs due to its high energy density. However, it suffers from the major drawbacks such as (1) volume expansion, cracking and pulverization of Si particles; (2) fast decay of capacity due to side reactions, consuming electrolyte rapidly. There is great potential to mitigate the degradation mechanisms by improved compositional and structural design based on better understanding of the ambiguous synergistic effect between the two types of particles. Moreover, lithium plating on the graphitic negative electrode is regarded as the foremost safety concern restricting the fast charge capability, leading to the consumption of lithium, electrolyte decomposition, formation of lithium dendrite and even thermal runaway. Therefore, it is critical to suppress lithium plating employing electrode design, manufacturing and rational protocols to address the longstanding challenge of battery fast charging. In this project, we aim to develop scalable and widely applicable innovations to facilitate the advancement of battery technologies for transport electrification. Correlative in operando experiment coupling the chemical, structure, crystallographic and electrochemical information from 2D to 4D will be conducted to elucidate the failure mechanisms of the graphite/Si composite electrode at the micrometer scale, particularly the synergistic dynamics of charge transfer, lithiation and deformation. Structural evolution is characterised as a function of SOC, C-rates and Si content, and linked to the capacity decay. Advanced 3D microstructure-resolved electro-chemo-mechanical model will be developed to analyse the performance limiting mechanisms, the impact of microstructural evolution on the reaction heterogeneities and predict the cycle life; in operando experiment and 3D microstructure-resolved phase field modelling will be employed to reveal the interplay between 3D microstructure of the electrode with the phase separation phenomenon, spatial dynamics of lithiation and plating. In addition, the physical processes of the relaxation behaviour, such as lithium exchange and redistribution will be elucidated by the 3D model, which will provide valuable guidelines for the refinement of fast charge protocols in terms of the timing and period of the rest steps. Finally, building on the insights of the study above, graphite/Si composite electrodes with novel structures will be fabricated, aiming to achieve at least 280 Wh kg-1 at the cell level with 20 mins charging for 50% of the capacity, corresponding to 15% increase in energy density and over 30% decrease of charging time compared to the commercial cells; an advanced physics-based fast charge protocol will be delivered to mitigate the plating risk and capacity fade.

Delivery of bespoke, tailored functional materials for specific applications often requires multistep and/or custom manufacturing processes which may not always be transferable. This programme of research brings together experts from across the UK with the goal of designing, developing and deploying sustainable microwave manufacturing processes that deliver bespoke inorganic functional materials not accessible at scale by current manufacturing methods. Microwave processing affords unique control and heating characteristics which, when coupled with judicious reactant choice, can shorten reaction times (from days to minutes), avoid unwanted side-reactions which can lead to unwanted additional products and improve short-range crystallinity by alleviating defect formation. These benefits represent considerable advantanges over traditional methods, where processing can lead to defects which plague performance. Synthesis of state-of-the-art, tailored functional materials currently requires additional resource demands, be they multistep processes or more energy-intensive treatments. Solving the production of such materials represents a key challenge in delivering materials with demanding performance criteria, e.g. nanostructured cathodes for high power density applications or textured electrodes for long cycle life. The unique properties of microwaves offer a greener, faster, and more targeted manufacturing route to achieving high value functional materials. Here, we target the scaled-up (kg/day) synthesis of nanostructured and faceted cathode particles, with the key delivery of (i) a microwave flow reactor producing high quality Li-ion battery cathode materials with primary particle morphologies and performances not accessible by traditional synthetic routes and (ii) a sustainable route to the reduction of manufacturing resource use, to just the amount required, through delivery of resource efficiency, multi-level optimization and circular economy principles. Realising this sustainable microwave manufacturing route to high value energy storage cathodes of immediate interest for next-generation electric vehicle applications has the opportunity to contribute in a significant way to a UK economic chemical industry opportunity worth a potential £2.7B per year.

In highly engineered materials, microscale defects can determine failure modes at the compo-nent/system scale. While X-ray CT is unique in being able to image, find, and follow defects non-destructively at the microscale, currently it can only do so for mm sized samples. This currently presents a significant limitation for manufacturing design and safe life prediction where the nature and location of the defects are a direct consequence of the manufacturing process. For example, in additive manufacturing, the defects made when manufacturing a test-piece may be quite different from those in a three dimensionally complex additively manufactured engineering component. Similarly, for composite materials, small-scale samples are commonly not large enough to properly represent all the hierarchical scales that control structural behaviour. This collaboration between the European Research Radiation Facility (ESRF) and the National Research Facility for laboratory CT (NRF) will lead to a million-fold increase in the volume of material that can be X-ray imaged at micrometre resolution through the development and exploitation of a new beamline (BM18). Further, this unparalleled resolution for X-rays at energies up to 400keV enables high Z materials to be probed as well as complex environmental stages. This represents a paradigm shift allowing us to move from defects in sub-scale test-pieces, to those in manufactured components and devices. This will be complemented by a better understanding of how such defects are introduced during manufacture and assembly. It will also allow us to scout and zoom manufactured structures to identify the broader defect distribution and then to follow the evolution of specific defects in a time-lapse manner as a function of mechanical or environmental loads, to learn how they lead to rapid failure in service. This will help to steer the design of smarter manufacturing processes tailored to the individual part geometry/architecture and help to establish a digital twin of additive and composite manufacturing processes. Secondly, we will exploit high frame rate imaging on ID19 exploiting the increased flux available due to the new ESRF-extremely bright source upgrade to study the mechanisms by which defects are introduced during additive manufacture and how defects can lead to very rapid failures, such as thermal runaway in batteries In this project, we will specifically focus on additive manufacturing, composite materials manufacturing and battery manufacturing and the in situ and operando performance and degradation of such manufactured articles, with the capabilities being disseminated and made more widely available to UK academics and industry through the NRF. The collaboration will also lead to the development of new data handling and analysis processes able to handle the very significant uplift in data that will be obtained and will lead to multiple site collaboration on experiments in real-time. This will enable us to work together as a multisite team on projects thereby involving less travelling and off-setting some of the constraints on demanding experiments posed by COVID-19.