Needs review: This is a short overview with no references. It would benefit from a comparison of the main barrier material types (typical thickness, through-plane thermal conductivity, compression behaviour, dielectric strength, max service temperature) and cited supplier or test data — details that need sourcing and subject-matter judgement rather than an unattended edit.
Thermal barrier materials (TBMs) sit between cells or modules to slow or stop the spread of heat from a cell in thermal runaway to its neighbours. They are one of the primary tools for meeting thermal propagation requirements at pack level.
Common material types include mica sheets, ceramic fibre and ceramic composites, aerogel, and intumescent materials that expand or char when exposed to heat to form an insulating barrier. Phase change materials are sometimes used alongside barrier materials for everyday thermal management, but they serve a different purpose to a dedicated fire barrier and should not be treated as a substitute for one.
Material choice depends on cell chemistry, cell format, pack architecture (modular vs. cell-to-pack), and, most significantly, the legislative requirement being designed to. A pack can pass some regulatory pan-fire tests with very little barrier material, while others require a robust, thickness-engineered barrier strategy to pass.
See also: Thermal Propagation, Fire Mitigation Strategies, Propagation Mitigation, Passive Propagation Resistance (PPR) Test