<p>With stringent regulations enforced to cut down vehicular emissions, original equipment manufacturers (OEMs) are in a transition phase of electrifying their vehicle fleet, and Li-ion battery (LiB)-based energy storage systems remain at the forefront of vehicle electrification, predominantly due to their higher energy densities compared to other energy storage alternatives. However, there is always a safety risk associated with LiBs. The existing LiB technologies are extremely sensitive to ambient temperatures and have inherently flammable liquid electrolyte. When used for vehicular applications they shall encounter several scenarios which can potentially lead to a Li-ion battery fire, an event commonly referred to as “thermal runaway”. Numerous safety measures (both active and passive) are generally adopted to ensure the safety of LiBs used in automobiles. Stringent regulatory targets such as the one mentioned in the ECE 324 R100 Rev 3 for the European market, or the GB 38031-2020 for the Chinese market, mean a resound passive fire safety mechanism needs to be deployed in Li-ion battery packs used in automobiles. In this paper, a system-level picture of passive fire mitigation strategies for Li-ion battery packs is presented. Different types of thermal barrier materials (TBMs) suitable for passive fire protection at pack, module and cell levels have been investigated. The performance of TBMs are evaluated experimentally using three different test procedures. The results reveal the most suitable type of TBMs for pack, module and cell-level passive fire protection of LiBs.</p>