| The depletion of energy and environmental pollution have made the green,pollution-free,recyclable,high-energy density lithium ion batteries come into being in response to the situation,and has been widely used in a short time.Mobile phones,laptops,electric cars and other lithium ion devices have been an indispensable part of people’s daily life.However,as a double-edged sword,lithium-ion batteries not only bring convenience to people,but also safety issues,which has become a key factor restricting the development of lithium-ion batteries.Flame retardants have a significant effect on improving the safety of lithium-ion batteries,and it is particularly meaningful to study the ignition and combustion characteristics of electrolytes containing flame retardants to provide data reference for the control of safety accidents of lithium batteries and the prevention of fires.Therefore,this paper conducts an experimental study on the ignition and combustion characteristics of the pool fire and jet combustion modes that may occur after thermal runaway of lithium-ion batteries.Firstly,an experiment and measurement system that can be used to quantitatively study the ignition and combustion characteristics of the electrolyte pool fire and jet combustion modes was designed and built.The experimental system can provide up to 300℃experimental temperature,0-55L/min air intake,7%-21% oxygen content,0-4bar injection pressure,and has high reliability.Secondly,based on the pool fire combustion experiment system,the ignition time,combustion time,average combustion rate,flame height,combustion intensity and other relevant data were measured by adding different ethoxy-(pentafloro)-cyclotriphosphazene(PFPN)electrolyte under different temperature and oxygen content conditions.The results show that PFPN has a significant flame retardant effect during the electrolyte ignition stage in the pool fire combustion mode,but a small flame retardant effect during the combustion stage.With the increase of temperature or oxygen content,the electrolyte with different PFPN content showed the characteristics of shorter ignition time,higher average combustion rate,higher flame height and higher combustion intensity.The emission intensity of CH·,OH· and P particles in the flame was analyzed by spectrograph,and the effect of flame retardant of PFPN in the combustion process was obtained from the microscopic perspective.Finally,based on the jet combustion experimental system,the flammable point,combustion time and combustion intensity of the electrolyte with different contents of ethoxy-(pentafluoro)-cyclotriphosphazene(PFPN)under different intake air flow,oxygen content,and temperature conditions were studied,and the influence of environmental factors on the ignition combustion characteristics of the jet combustion containing PFPN electrolyte was analyzed.The results show that the inlet flow rate and oxygen content have little effect on the flammability point of the electrolyte containing PFPN jet combustion,while the increase of temperature can greatly improve the flammability and combustion time of the electrolyte jet combustion. |
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