Naturally-derived thermal barrier based on fiber-reinforced hydrogel for the prevention of thermal runaway propagation in high-energetic lithium-ion battery packs

Due to the constant increase in energy density of lithium-ion batteries (LIBs), safety concerns in case of a thermal runaway event become more critical. Thermal runaway propagation (TP) can destroy an entire LIB pack, rapidly releasing energy and material through heat and fire. A solution for TP that minimally affects the LIB pack remains one of the main unsolved safety-related issues in battery systems. This paper presents an eco-friendly thermal barrier made of a high water-content hydrogel derived from natural polymers reinforced by a flame-retardant fiber material. The 2-mm-thick barrier, when placed between 50 Ah LIB cells, was able to prevent thermal propagation in 2-cell modules. Once the barrier temperature reaches around 100 °C, it can absorb a large amount of energy due to water vaporization. Afterward, the remaining low thermally conductive fiber material provides thermal insulation between cells. In addition, the mechanical properties of the barrier, such as compressive strength and flexibility, make it a suitable material to be placed between LIB cells. Furthermore, its ease of manufacturing and biodegradability enable the barrier to provide higher safety for LIB packs while maintaining the cost and environmental impact to a minimum.