This thesis investigates the synthesis and application of nanomaterials-doped phase change materials (PCMs) as a passive thermal management strategy for lithium-ion batteries, with a particular focus on their ability to mitigate thermal runaway. A dedicated experimental campaign was conducted using nail penetration tests to compare cells with and without PCM encapsulation, while simultaneously monitoring temperature, pressure, and gas composition. Advanced data processing techniques, including interpolation and overlay analysis, were applied to ensure robust interpretation of the results. The findings demonstrate that PCM significantly reduces the severity of thermal runaway. Maximum cell temperature decreased from ~415 °C (no PCM) to ~309 °C (with PCM), while spatial temperature gradients narrowed from ~15 °C to ~5 °C.