To find and understand the influence DC ripple current has on lithium-ion cells in automotive applications

The battery cell is probably the most critical component of an EV and electrification, especially in passenger cars is key to more sustainable transport solutions. Currently, most battery testing is performed using very "clean" DC test currents whereas in real world situations there is significant amounts of noise introduced by the switching of power inverters as well as motor characteristics. These AC components are of various frequencies, and it is crucial to understand how they affect the performance of the battery in the long run, for which current literature offers differing opinions.

To characterise how Li-ion cells react to ripple current, the project aims to conduct experiments applying various types of ripple to various lithium-ion cells with electrochemical modelling used to inform decisions on the design of experiment. Additionally, if this modelling provides different results to those eventually found experimentally, it will serve to highlight the limitations of that model and aid any future work done to improve the model. The experimental stage will then be conducted, varying the chosen variables (e.g. waveform, frequency, cell chemistry, cell format etc.) whilst concurrently recording chosen indicators (e.g. EIS, capacity/power fade) before performing post-cycling characterization. This characterisation is expected to include various scanning and dissection, so as the specific type of degradation can be determined. This will aid in the final objective of the project which will be to seek an explanation for the experimental results in electrochemical theory. This is crucial as the ripple current may enhance or emphasise specific type of degradations and so imply methods to negate this deterioration, and any further understanding of the working of lithium-ion cells is a valuable addition to literature.

This work will not only add to the lithium-ion knowledge base, but the project will also look to exploit the results found to inform best practice in the design of battery management systems, such as removal of power filters or modifications of switching frequencies. Hence this work has the potential to not only improve battery lifetime by reducing degradation, but also impact the way power electronic subsystems are designed. This potential simplification or improvement of performance of battery management systems shows the relevance to both AVL and UKRI is significant.

Impact Summary

This proposal has been developed from the ground up to guarantee the highest level of impact. The two principal routes towards impact are via the graduates that we train and by the embedding of the research that is undertaken into commercial activity. The impact will have a significant commercial value through addressing skills requirements and providing technical solutions for the automotive industry - a key sector for the UK economy.

The graduates that emerge from our CDT (at least 84 people) will be transformative in two distinct ways. The first is a technical route and the second is cultural.

In a technical role, their deep subject matter expertise across all of the key topics needed as the industry transitions to a more sustainable future. This expertise is made much more accessible and applicable by their broad understanding of the engineering and commercial context in which they work. They will have all of the right competencies to ensure that they can achieve a very significant contribution to technologies and processes within the sector from the start of their careers, an impact that will grow over time. Importantly, this CDT is producing graduates in a highly skilled sector of the economy, leading to jobs that are £50,000 more productive per employee than average (i.e. more GVA). These graduates are in demand, as there are a lack of highly skilled engineers to undertake specialist automotive propulsion research and fill the estimated 5,000 job vacancies in the UK due to these skills shortages. Ultimately, the CDT will create a highly specialised and productive talent pipeline for the UK economy.

The route to impact through cultural change is perhaps of even more significance in the long term. Our cohort will be highly diverse, an outcome driven by our wide catchment in terms of academic background, giving them a 'diversity edge'. The cultural change that is enabled by this powerful cohort will have a profound impact, facilitating a move away from 'business as usual'.

The research outputs of the CDT will have impact in two important fields - the products produced and processes used within the indsutry. The academic team leading and operating this CDT have a long track record of generating impact through the application of their research outputs to industrially relevant problems. This understanding is embodied in the design of our CDT and has already begun in the definition of the training programmes and research themes that will meet the future needs of our industry and international partners. Exchange of people is the surest way to achieve lasting and deep exchange of expertise and ideas. The students will undertake placements at the collaborating companies and will lead to employment of the graduates in partner companies.

The CDT is an integral part of the IAAPS initiative. The IAAPS Business Case highlights the need to develop and train suitably skilled and qualified engineers in order to achieve, over the first five years of IAAPS' operations, an additional £70 million research and innovation expenditure, creating an additional turnover of £800 million for the automotive sector, £221 million in GVA and 1,900 new highly productive jobs.

The CDT is designed to deliver transformational impact for our industrial partners and the automotive sector in general. The impact is wider than this, since the products and services that our partners produce have a fundamental part to play in the way we organise our lives in a modern society. The impact on the developing world is even more profound. The rush to mobility across the developing world, the increasing spending power of a growing global middle class, the move to more urban living and the increasingly urgent threat of climate change combine to make the impact of the work we do directly relevant to more people than ever before. This CDT can help change the world by effecting the change that needs to happen in our industry.