Rapid internal heating of Lithium-ion batteries

This PhD will explore methods of rapidly heating battery cells to operational temperature, including theoretical analysis and a strong element of experimentation.

Thermal management of batteries is an extremely important topic because it directly and significantly impacts many of the batteries’ key performance characteristics, including available energy, efficiency, power availability, and rate of degradation. Much research has been directed towards the effective cooling of batteries, but extremely little has been focussed on rapid heating of batteries. Ideal operating temperatures for batteries are between 10-40°C, however Electric Vehicle batteries are frequently required to operate in colder conditions. Being able to rapidly heat batteries is important for cold-start performance and rapid charging.

Battery heating systems usually use electric heaters to warm the coolant fluid. Heat pumps are an alternative but have poor efficiency at low temperatures. These ‘external heating’ approaches heat the cells from the outside, and so are limited in the temperature uniformity they can achieve across the pack since the working fluid inevitably reaches some cells before others on its path, leading to ‘hot spots’ and ‘cold spots’. The faster the rate of heating, the more exaggerated this effect will be. Both systems are also limited by the power they can draw from their own electrical supplies, incur efficiency losses in DC-DC conversion, and increase the parts count, complexity, and cost of the battery system.

The idea of ‘internal heating’ or ‘self-heating’ of cells has gained traction as a means of avoiding additional heating componentry. The basic principle is to move charge into and out of the battery cells at high frequency using Alternating Current (AC), using the internal resistance of the battery cells to create heat. This project will establish the potential of AC as a means of heating batteries from within. The PhD will compare this internal heating mechanism with common external (surface) heating with respect to achievable heating rate and temperature uniformity across an individual cell and a battery pack. The hypothesis is that AC heating will provide performance benefits in these two areas – rate of heating, and temperature uniformity – which will improve the ability of battery packs to operate in colder climates and facilitate fast charging at short notice. You will explore this through modelling and experimentation, as well as investigating related topics such as effects on battery degradation.

The project is likely to involve aspects of mechanical engineering (thermodynamics), electrical engineering (power control) and chemistry (battery cell modelling). The ideal candidate will have a degree in one of these subjects, and the motivation and initiative to develop in the other two, suitably supported by the supervisory team.

This project is offered as part of the Centre for Doctoral Training in Advanced Automotive Propulsion Systems (AAPS CDT). AAPS CDT is supporting the future leaders of mobility. Bringing together industry, policymakers, academics and researchers to pioneer and shape the transition to clean, sustainable mobility for all.

Prospective students for this project will be applying for the CDT programme which integrates deep research with a unique skills and training programme to give you comprehensive training and detailed knowledge in your chosen specific subject area 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 and 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.

As part of our AAPS community you will benefit from our training activities such mentoring future cohorts and participation in centre activities such as masterclasses, research seminars, research incubators and guest lectures. There are also opportunities to undertake industrial placements and academic secondments.

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 3.5-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)