Honeycomb-like structure with excellent thermal regulation and flame-retardant functions boosts Li-ion battery safety

Abstract

The safety of Li-ion batteries urgently needs to be improved due to the rapid expansion of electric vehicles. Herein, a honeycomb-like hydroxyapatite/sodium alginate/boron nitride (HAP/SA/BN) aerogel has been designed to encapsulate sodium thiosulfate pentahydrate (STP) for thermal regulation and flame retardancy. Benefiting from the aligned and porous aerogel, the SHSB composite possesses the properties of large latent heat, high thermal conductivity, superior shape-stability, mechanical strength and flexibility. Consequently, the continuous charge–discharge of a battery pack under a 40 °C environment can be cooled by 15.9 °C with an ultra-stable coulombic efficiency of 100%. When the battery temperature is rapidly increased, causing thermal runaway, the fire can be extinguished through cooling based on the thermal-chemical reaction of the hydrated salt, the strong scaffold effect from the HAP nanorod network, and heat and air isolation via the formation of an impermeable salt layer. The flame retardant works effectively with a small amount of heat release (0.2 kJ g⁻¹), high temperature tolerance (513.5 °C) and long shape-stability (100 s). Hence, the excellent thermal regulation and flame retardancy are potentially two strong defense lines that can substantially boost Li-ion battery safety.