This research will focus on understanding the link between battery degradation and methods of battery thermal management, especially with respect to cells of different sizes.
Exposure to high temperatures and temperature cycling are two of the most significant aggravating factors for battery aging. The trend in automotive applications is for ever increasing cell sizes, with some vehicles now featuring cells of several hundred amp-hours and up to 1m long. As cells sizes increase achieving a uniform temperature across and through the cell is increasingly difficult because only the cell surface is cooled, and because the cooling fluid (air/water/oil) will typically reach some parts of the cell before others. This non-uniform temperature distribution will very likely lead to non-uniform aging of the cells, which this PhD aims to investigate, quantify, understand, and propose mitigation mechanisms against. This is an important topic not only for maximising the lifetime of the cells in the vehicle, but also when considering the potential value of the cells in second life, or how they might be recycled.
Work will focus initially on immersive cooling, where battery cells are directly immersed in a dielectric oil. This is because immersive cooling is considered the most advanced and high-performance approach to thermal management and is a current focus for research. Problems with this include the cost and weight added to the system by the fluid. This trade-off will be examined by considering the possibility of partially filling the battery with fluid so that cells are only partially submerged, reducing fluid weight at the expense of some thermal homogeneity.
Opportunities may exist for synergy with the group working on Structural Batteries, depending on the size scale of the batteries which that group have succeeded in producing by this time. These opportunities will be explored as appropriate, as the relevance of this proposed doctoral research is particularly relevant to structural batteries owing to their increased value and added difficulty in recycling them. The work of the existing group to date has focussed primarily on producing working batteries. Degradation has not yet been investigated, and whilst recyclability has been embedded in materials selection no analysis has been performed in this space.
Electrochemical testing of cells will be possible with charging/discharging experiments and electrochemical impedance monitoring. Microstructural characterisation of the impact of degradation will form a key aspect of the doctoral study. This will involve the use of nanoindentation, electron and atomic force microscopy and/or Focused Ion Beam (FIB) to study internal changes to the microstructure through the preparation of microscale cross-sections and lamella. Synchrotron work (microtomography, X-ray diffraction, and/or spectroscopy) with in-situ electrochemical testing will reveal regions of heating/degradation, formation of stresses locally at anode or cathode, and opportunities for retaining battery performance. These insights will be used to generate enhanced models of degradation, providing crucial insights into predicted lifetimes and potential recycling opportunities associated with these systems at end of life.
This project is offered as part of the Centre for Doctoral Training in Advanced Automotive Propulsion Systems (AAPS CDT). The Centre is inspiring and working with the next generation of leaders to pioneer and shape the transition to clean, sustainable, affordable mobility for all.
Prospective students for this project will be applying for the CDT programme which integrates a one-year MRes with a three to four-year PhD
AAPS is a remarkable hybrid think-and-do tank where disciplines connect and collide to explore new ways of moving people. The MRes year is conducted as an interdisciplinary cohort with a focus on systems thinking, team-working and research skills. On successful completion of the MRes, you will progress to the PhD phase where you will establish detailed knowledge in your chosen area of research alongside colleagues working across a broad spectrum of challenges facing the Industry.
The AAPS community is both stretching and supportive, encouraging our students to explore their research in a challenging but highly collaborative way. You will be able to work with peers from a diverse background, academics with real world experience and a broad spectrum of industry partners.
Throughout your time with AAPS you will benefit from our training activities such mentoring future cohorts and participation in centre activities such as masterclasses, research seminars, think tanks and guest lectures.
All new students joining the CDT will be assigned student mentor and a minimum of 2 academic supervisors at the point of starting their PhD.
Funding is available for four-years (full time equivalent) for Home students.
See our website to apply and find more details about our unique training programme (aaps-cdt.ac.uk)