Propagation-resistant glass fibre reinforced polymer sleeves for the reinforcement of lithium-ion cells under thermal abuse conditions

Thermal runaway propagation can turn small, contained failures of lithium-ion cells into a catastrophic failure of an entire battery pack. The addition of safety materials to contain such an event is therefore crucial. Sidewall rupture events are likely to result in propagation as failure is directed towards adjacent cells. However, sidewall rupture conditions are less studied due to their difficulty to initiate. Using recently published methods to reliably initiate sidewall rupture under thermal abuse, lightweight sleeve materials have been studied to expand upon our understanding of the performance of these interstitial material solutions. Thermal abuse was achieved via a heating coil at a heating rate near to 100 W, maintaining above 250 °C throughout heating at the coil. Cells were abused at 100 % state of charge. Our research involves the use of glass fibre reinforced polymer composite sleeves to reinforce the sidewall casing of cylindrical cells. At the single-cell level, tests show reinforcement sleeves survived the event and forced ejecta upward and downward from the sleeves. At the cluster level, without sleeves propagation was total with all adjacent cells suffering sidewall rupture. With sleeves, propagation prevention was 100 % effective with no voltage or mass loss to adjacent cells, maintaining 4.2 V and 66 g in all adjacent cells. This research underpins the material selection and improved systems designs of future battery systems for a range of applications including road transport, aerospace and domestic energy storage.