Prof James Marco WMG Energy Group
Significant advances have been made in recent years in our understanding of the electrochemical performance of lithium-ion batteries (LIBs), their degradation, safety, manufacturability and recyclability – in part, through innovations in experimental methods and mathematical modelling.
WMG is at the heart of this research through our involvement in projects such as Multiscale Modelling (MSM), Nextrode, Degradation, SAFEBAT and RECOVARS. Much of our Fundamental or low TRL research is being undertaken in collaboration with other leading UK universities and is funded by the Faraday Institution (FI). The FI is the UK’s independent institute for electrochemical energy storage research, skills development, market analysis, and early-stage commercialisation. In parallel, across many different sectors such as automotive, aerospace, rail and energy, WMG is partnering with OEMs and system integrators to improve system-scale metrics of cost, energy density, power density and sustainability.
This mid-TRL collaborative research is often focused on improving battery system designs, material selection and manufacturing methods. Notwithstanding these innovations, the individual battery fundamentally remains a passive component. Energy transfer is governed by the requirements of the external load (or supply), often with limited insight as to the impact this will have on battery performance, life and safety. This uncertainty is known to drive sub-optimal solutions or increased downstream costs and development time.
Our vision for Smart Battery technology is to transform the LIB from a passive component into a mechatronic device, through the integration of sensing, communication and controller hardware directly within the battery at the point of manufacture. The concept is format and electrochemistry agnostic. We believe a future Smart Battery will:
- Have the ability to modulate or isolate the electrical current flowing through the terminals.
- Have the ability to measure key internal variables such as electrode potentials, current, temperature, mechanical stress and internal pressure.
- Be able to resolve measurements both spatially and temporally.
- Include localised control and communication hardware to integrate the LIB with its external environment without adding complexity via wireless or powerline data-transfer.
WMG are exploring two primary application pathways for our Smart Battery research: advanced characterisation and direct manufacture:
Advanced Characterisation – We use embedded instrumentation to provide insights into commercial battery performance, degradation and life that is not possible with traditional sensing methods. This is achieved by developing new experimental techniques and novel custom fixtures to embed instrumentation directing inside commercially available LIBs.
If you are going to instrument a cell you need to be able to do this reliably and robustly. The process flow diagram illustrates the experimental stages employed for cell instrumentation and includes: sensor fabrication, cell modification and sensor insertion. The diagram highlights the different verification stages for assessing LIB performance, operation and ageing.
As a first stage 21700 cylindrical cells were instrumented with bespoke thermocouples, enabling internal temperature sensing.
A systematic and rigorous methodology has been developed and proven through extensive testing:
- Internal temperature observed to be notably higher than surface temperature.
- Temperature differential between core and surface diverged as battery state of health decreases.
- Cell performance verified pre- & post- instrumentation with negligible degradation.
- Stability and integrity of instrumented cell operation verified via load-profile cycling.
- In comparison to reference cells, no greater differential degradation observed over the long-term.
In addition, for larger format cells, we have measured spatial variations in temperature and mechanical strain that occur during different levels of electrical and thermal loading. Key to this work is the ability to integrate sensors into the battery structure in a method that doesn’t negatively impact is performance (e.g., energy capacity and impedance) and its life.
Direct Manufacture – We are leveraging our capability to build LIB technology, within our Battery Scale-Up Line (BSU), to explore the process challenges of directly manufacturing Smart Batteries for use in high-value systems or niche applications.
Impact – The potential impact of our Smart Battery research across the complete value chain is significant. Within the context of battery manufacturing, the ability to measure internal states of temperature and pressure may underpin optimised formation processes – improving productivity and reducing the energy demands associated with volume manufacture. At the system scale, we are undertaking research to optimise the integration of Smart Batteries into the complete battery pack to further increase performance, safety and end-of-life management.
This research has the potential to drive new physics-informed models of the battery and new approaches to state-of-X (SoX) estimation for the next-generation of battery system management (BMS) designs. The ability to monitor “in-cell” behaviour within a battery pack and manage the distribution of electrical current within individual cells can fundamentally change our approach to battery systems engineering.
- Yifei Yu, Timothy Vincent, Jonathan Sansom, David Greenwood, James Marco, “Distributed internal thermal monitoring of lithium ion batteries with fibre sensors“, Journal of Energy Storage, Volume 50, June 2022, 104291
- T. A. Vincent, B. Gulsoy, J. E. H. Sansom and J. Marco, “A Smart Cell Monitoring System Based on Power Line Communication—Optimization of Instrumentation and Acquisition for Smart Battery Management,” in IEEE Access, vol. 9, pp. 161773-161793, 2021, doi: 10.1109/ACCESS.2021.3131382.
JAMES MARCO received the D.Eng. degree from the University of Warwick, in 2000. He is currently employed at the University of Warwick as a Professor in battery systems engineering, where he leads a research group focused on battery characterization, modeling, and control. His research interests include the challenge of scaling-up individual battery cells to complete energy storage systems. Example areas include model, control and experimental design to quantify electro-thermal heterogeneity at cell and system level, and methods to extend battery useful life through repurposing and re-use.
- The capacity and resistance differences of cells amplify the inhomogeneity at a system level and results in accelerated aging and degradation.
- For the module design, where many cells are in parallel, the BMS typically does not have access to individual cell currents and temperatures.
- We aim to predict current, state of health and temperature of each cell in the module (or pack) via modelling the interaction between cell and busbar and weld quality.