Electric vehicle (EV) batteries contain 100s to 1000s of individual lithium-ion cells, ordered into modules and packs and controlled by a battery management system. However, cells, modules and packs have not been designed as a “single system” across the battery because of lack of communication along the supply chain. Cell manufacturers optimise the amount of energy stored in their cells, because ‘energy density’ is the metric they use to compete against one another. Battery pack designers select the cell with the highest energy density because this is the only metric they have to compare the performance of cells. The problem is that energy density optimisation is at the expense of almost every other aspect of the cell’s performance, particularly its thermal performance, meaning that the range and lifetime of EVs are not optimised.
|By the numbers|
|100s-1000s||Individual cells in a battery pack|
|10-20%||Expected increase of useable energy at the pack level|
|100-200%||Anticipated improvements in battery lifetime at the pack level|
As temperature affects every aspect of lithium-ion cell performance, effective thermal management of battery packs is critical, and the battery packs in use today have large thermal management systems in an attempt to remove the heat. This substantially reduces the energy density of the battery pack as an overall system.
The Faraday Institution Multi-Scale Modelling project has proposed changes to cell design to improve thermal performance, as well as a new standard – the Cell Cooling Coefficient (CCC) – that allows auto makers to compare the ability to thermally manage commercial lithium-ion batteries across a set of performance targets.
The team is engaging with multiple academic and industry partners globally informing them on how to make CCC measurements, with the explicitly disruptive and transformational goal to ‘change the entire global lithium-ion battery industry.’ The CCC has been introduced more widely to the industry via a paper in Nature and an educational video.
In July 2020 the TOPBAT project was initiated, building on the successes of the Faraday Institution Multi-Scale Modelling project. It aims to position UK cell manufacturers at the forefront of this revolution in cell design by validating its redesign concepts through a cell redesign project on a commercially available cell.