The i-CoBat project—a collaboration between M&I Materials, WMG and Ricardo —aims to develop and to demonstrate a new form of EV battery cooling technology based on cell immersion cooling using dielectric fluid.

This innovation promises improved power output and cell longevity, faster charging rates and lower costs, significantly addressing the key consumer issue of range anxiety.

As the automotive industry seeks to electrify its product ranges, the thermal management of high capacity batteries used for electric vehicles (EVs) is proving a significant challenge. The performance and efficiency of battery cells can deteriorate—and their ageing can be accelerated—if operating temperatures exceed the upper or lower limits of a comparatively narrow range. In extreme cases, exceeding upper operating limits can risk thermal runaway of cells, leading to catastrophic failure and potentially, fire.

For market acceptability—and in particular, to persuade owners of liquid-fuelled vehicles to switch to an EV—charging times can be a significant challenge in terms of alleviating range anxiety. Consumers seek fast recharging times, good performance and range, and competitive prices; during fast charging, however, battery cells can produce up to three times more heat energy than in normal driving and charging operations; with heating of the cells being a dominant factor in battery ageing and performance degradation. Using current battery cell technology, therefore, the requirement for thermal optimization of pack design and operation is a vitally important one.

Current EV batteries packs tend to use air cooling or cold plate cooling using water/ethylene glycol or a refrigerant. The limitations of such thermal management systems act to restrict charging rates or the number of fast charge cycles that can be carried out each day. One possible answer to range anxiety could be to increase pack size, but this would significantly increase costs.

Led by M&I Materials, the i-CoBat projectis part of the UK government’s Faraday Battery Challenge and will test an immersion cooled battery pack concept using M&I Materials’ biodegradable dielectric cooling fluid, MIVOLT. The chemistry of MIVOLT fluids allows them to act as a dielectric coolant, removing heat directly from all areas of a battery cell surface.

MIVOLT’s dielectric fluids do not conduct and can therefore come into direct contact with battery packs. Direct liquid immersion cooling with MIVOLT means that heat transfer begins at the source with no reliance on a secondary indirect cooling system. Direct liquid immersion cooling inherently enables a simpler thermal management solution, negating the need for complex systems.

M&I Materials have been working in advanced materials and electrical insulation for more than 100 years, with a core specialism in dielectric fluids for more than 40. The innovation promises improved power output and cell longevity, faster charging rates and lower costs, significantly addressing the key consumer issue of range anxiety.

As we seek to extract the maximum possible energy and durability from a battery, and to replenish it as quickly as possible, thermal management becomes critical. It’s no longer just a matter of keeping the battery cool—it’s about optimizing the temperature for any given operation. There are many cooling mechanisms used by different manufacturers, and this project allows us to investigate a close-coupled cooling mechanism with a biodegradable coolant.

—Professor David Greenwood, Professor of Advanced Propulsion Systems at WMG, the University of Warwick