Measuring the thermal properties of a lithium-ion pouch cell

Abstract

Electrified transport will be essential if we are to significantly reduce greenhouse gas emissions whilst improving air quality. However, their potential is hampered by limitations in the battery thermal management system (BTMS) design which can significantly reduce the lifetime of battery packs. This research pinpoints the model inputs as the source of significant error before presenting new characterisation methods to improve the model accuracy. Following this an optimum thermal model is proposed which allows for integration of these characterisation methods in a computationally efficient manner.

Utilising methodological innovations, novel methods were developed for thermal diffusivity measurement. These methods overcome a previous measurement flaw which was particularly problematic when measuring the thermal properties of batteries. A bespoke reference sample was used to validate the method which showed <10 % errors before demonstration on a pouch cell was performed. By measuring the thermal diffusivity, this allowed for calculation of the thermal conductivity. These methods were then patented and published for peer review. Alongside this the tab thermal resistance was identified as being difficult to characterise. Using a bespoke state of the art temperature controller, a method was presented which allowed for the simple characterisation of this property. These properties were then combined into a demonstration electro-thermal model which showed how these characterisation methods could be used to capture key physics causing battery degradation.

Through the establishment of About:Energy, a spin-out company founded by the author, this novel technology was commercialised. Since then the characterisation and modelling methods developed in this research have been used by a number of industry leaders across domains such as manufacturing, automotive, motorsport, and aerospace.