Design and development of composite enclosure with variable thermal conductivity for Li-ion battery module

Abstract

Thermal management of batteries can be accomplished through active or passive built in cooling sources. Air, liquid (mainly water) and phase-changing materials or a combination of these three methods are used in existing thermal management systems. Current solutions with active cooling are adding weight and complexity to EV and HEV batteries. The involvement of phase-changing materials (PCMs) as a passive cooling technique is also adding to the complexity, weight, and the additional thermal resistance in the heat dissipation process of batteries. An innovative idea for a composite casing for car batteries is considered in this project. The composite casing will have variable thermal conductivity, defined by the local volume fraction of carbon fibres and other conductive elements (including copper pins) within the composite. The selectively high thermal conductivity in areas of the casing will create “thermal avenues” close to the hot areas of the battery in order to provide passive heat dissipation in the areas needed the most. The composite casing will provide a low weight, simple thermal management solution that requires minimum maintenance. A 3D model of a Li-ion battery single cell was developed and used to evaluate several geometries of a battery module currently being used by battery manufacturers. Heat transfer simulations are validated by experimental results from a custom jig that emulates the battery module arrangement. Heating elements of similar size and power/heat output to individual cells have been used for the experiments. The composite casing was manufactured using the resin infusion method, and copper pins were inserted into the significant locations of the enclosure during the process of resin infusion. The metallic pin arrangement was validated experimentally with the bespoke test rig. Simulation and experimental results are in better agreement with each other for the scenarios of the composite enclosure and the composite enclosure with the copper pin arrangement. Furthermore, the simulation results, IR thermography results, and experimental results confirmed that the copper pins arrangement is an effective solution to conduct the heat that is accumulated inside the enclosure to the outside without the use of any kind of active cooling methods such as air-cooling or water cooling.