Mitigating thermal runaway propagation of pouch-type lithium-ion batteries

• Main Author: Muhammad Ahshiq Bin V M Abdul Muthaliff
• Other Authors: Aravind Dasari
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/165765
• Institution: Nanyang Technological University

Lithium-Ion Batteries (LIB) are a common power source for various applications. Amongst the different types of LIB, pouch cells are widely adopted due to their compact design and excellent performance. However, when subjected to extreme conditions, pouch cells ignite and explode in a phenomenon known as thermal runaway (TR). If multiple pouch cells are present, TR can propagate from the trigger to the neighbouring cell, resulting in catastrophic effects. Previous studies have explored various methods such as extinguishers and active thermal management to prevent TR propagation. Despite their effectiveness, these solutions are challenging to implement due to their high cost, weight and hazards. Hence, passive thermal management remains a strong candidate for development. This project investigated the effectiveness of polymeric and metallic partition boards in mitigating thermal runaway propagation between pouch cells. Two types of intumescent flame retardant (IFR) systems comprising Piperazine Pyrophosphate (PAPP), Melamine Polyphosphate (MPP) and Zinc Borate were incorporated into polyamide-11 (PA11). Neat PA11, PA11-IFR 1 and PA11-IFR 2 partition boards were fabricated using a hot press. Metallic partition boards were constructed from aluminium sheets. The performance of the partition boards was tested via overcharge-induced TR tests. The module used for the TR tests comprised two pouch cells with a partition board in between. Thermocouples inserted between the pouch cells and the boards recorded the temperature profile. The extent of damage suffered by the pouch cells and partition boards were visually assessed. Neat PA11 partition boards completely disintegrated into fragments, resulting in TR propagation and combustion of both cells. However, PA11-IFR 1 and PA11-IFR 2 partition boards retained their structural integrity. Hence, TR propagation was prevented. Only the trigger cell ignited whilst the adjacent cell was bloated. Despite this, no intumescent layer was formed on the PA11-IFR partition boards. TGA analysis of the board samples before and after TR revealed that the IFR had been consumed during TR. This led to the hypothesis that melamine gas from the decomposition of MPP prevented TR propagation due to its dilution effect. Aluminium partition boards experienced minor surface damage and successfully mitigated TR propagation. The adjacent cell was bloated in this case as well. Comparison of peak temperatures across the partition boards proved that aluminium possessed better heat dissipation compared to PA11-IFR 1 and PA11-IFR 2 partition boards. These findings suggest that heat absorption and heat dissipation are both feasible ways to mitigate TR propagation across pouch cells. In future studies, TR tests can be conducted in an enclosed setup with more pouch cells to better simulate the real-world scenario. Additionally, other materials with low thermal conductivity and high working temperature can be used to construct partition boards.