“Runaway” heat release in lithium ion batteries usually starts with loss of integrity of the solid-electrolyte interface (SEI). The electrolyte then contacts the anode, reacting and generating heat, leading to electrolyte decomposition, further reaction, and thus to cathode decomposition.
Cathode decomposition is critical, because it releases oxygen and so can cause fire or explosion. Fire protection of both electrolyte and cathode are therefore necessary to improve lithium ion battery safety. In these studies, the mineral PIN flame retardant boehmite [aluminium oxide hydroxide AlO(OH)] was tested for lithium-iron-phosphate (LiFePO4) cathodes. Fire risk was reduced by up to 50% (reduction in self extinguishment time), without deterioration of cathode electrochemical performance, by addition of 15% of microparticulate boehmite encapsulated in poly(urea formaldehyde). Non-encapsulated boehmite or larger particles were less effective.
“Encapsulation of flame retardants for application in lithium-ion batteries”, P.-H. Huang et al., J. Power Sources 338 (2017) 82e90 http://dx.doi.org/10.1016/j.jpowsour.2016.11.026 and “Boehmite-based Microcapsules as Flame-retardants for Lithium-ion Batteries”, P.-H. Huang et al., Electrochimica Acta 2017 http://dx.doi.org/doi:10.1016/j.electacta.2017.01.094