Experimental study on fire hazard of LiCoO2-based lithium-ion batteries with gel electrolyte using a cone calorimeter

Abstract

• A higher SOC/ incident heat flux leads to a more violent combustion of GPE batteries. • The inverse of the TTI has an exponential relationship with the SOC and a linear relationship with the incident heat flux. • The MLR is proportional to the SOC and incident heat flux. • If completely combusted, battery with a higher SOC/or exposed to a higher heat flux generally has a higher pkHRR. • If completely combusted, batteries with higher SOCs and at higher incident heat fluxes possess greater fire risk. Compared with traditional liquid electrolyte batteries, lithium-ion batteries with gel polymer electrolytes are preferable due to their lower risk of electrolyte leakage or mechanical abuse. However, the safety qualities of gel polymer electrolyte batteries appear to be overestimated, as a catastrophic fire risk is ignored. In the present study, cone calorimeter tests were conducted to comprehensively evaluate the fire hazards of gel batteries. The effects of the states of charge and incident heat flux were studied, enabling the derivation of a critical state of charge and critical heat flux, especially in regard to the time to ignition, mass loss rate, and heat release rate. Several fire hazard evaluation systems were also introduced and the potential burning risk of the gel battery was discussed. The total heat release, fire growth index, and effective heat of combustion were calculated to evaluate the risks of batteries with various states of charge and various incident heat fluxes. The results showed that gel batteries have a higher risk of heat contribution when possessing states of charge higher than 25% and heat flux values above 15 kW/m 2 . By providing these necessary data, this work helps better understand the fire hazards of gel polymer electrolyte batteries and also provides a method for engineers or manufacturers to assess the corresponding fire risks.