Inhibition Mechanisms of Lithium-Ion Battery Deflagration by the Free Space and Aerogel Wall Surface Inside an Explosion-Proof Power Enclosure

Abstract Deflagration of lithium-ion battery thermal runaway (TR) products poses a safety challenge for explosion-proof power enclosures in underground coal mines. In this study, sealed-chamber experiments and chemical kinetic simulations were combined to investigate the effects of free-space volume and silica aerogel wall linings on the deflagration of TR products released from commercial 26700 lithium iron phosphate cells. Free-space volume exhibited a pronounced nonmonotonic effect on deflagration intensity. The maximum deflagration pressure (Pmax) reached 0.51 MPa at 53 L, whereas the maximum pressure rise rate ((dP/dt)max) peaked at 7.07 MPa/s at 42 L. Gas composition and kinetic analyses suggested that this behavior reflected the coupled effects of fuel concentration, oxidation progress, and physical confinement. Restricted further oxidation at smaller volumes and stronger fuel dilution at larger volumes contributed to the reduced deflagration intensity. At a reference free-space volume of 84 L, introducing a 3 mm aerogel felt liner reduced Pmax and (dP/dt)max by 33.2% and 34.9%, respectively, while further thickening provided smaller incremental benefits. The suppression may involve gas–solid heat exchange and pressure-wave attenuation, with additional possible contributions from the retention of condensable species and heterogeneous radical loss at pore surfaces. These findings highlight the combined roles of combustion processes and wall interactions in TR product deflagration and provide a basis for free-space allocation and wall-lining design in lightweight safer explosion-proof battery enclosures.