BATTERY CELL THERMAL RUNAWAY BARRIER

A thermal runaway barrier for at least significantly slowing down a thermal runaway event within a battery assembly. The thermal runaway barrier includes a layer of a nonwoven fibrous thermal insulation comprising a fiber matrix of inorganic fibers, thermally insulative inorganic particles of fumed silica and aerogel particles dispersed within the fiber matrix, and a binder dispersed within the fiber matrix so as to hold together the fiber matrix, and an organic encapsulation layer enclosing the layer of nonwoven fibrous thermal insulation.