Comparative studies on the combustion characters of the lithium-ion battery electrolytes with composite flame-retardant additives

Electrolytes are important parts of lithium-ion batteries, but traditional carbonate-based electrolytes have high flammability which could be an important source of heat generation in the thermal runaway process. The combustion characters of electrolyte and carbonate solvent based on three kinds of composite flame retardants are studied. The influence of lithium salt on the combustion process of carbonate mixed solvents is explored, and the flame-retardant effect of composite flame retardants on solvents is discussed. The results show that lithium salt has a great influence on the flame-retardant effect of carbonate mixed solvent, and changes the combustion rate and flame shape of carbonate mixed solvent. The combustion rate of carbonate solvents containing flame retardants decreases in varying degrees, and the flame state of the solvent samples changes greatly with the addition of flame retardants. Phenoxycyclophosphazene significantly reduces the peak value of the combustion rate of carbonate mixed solvent, reduces the flame height and fuel peak temperature, but has no significant effect on the flame temperature. Melamine phosphate reduces the combustion rate of the control stage of low boiling point component, reduces the flame height and fuel peak temperature, but does not change the peak temperature of carbonate mixed solvent flame. Tris (2-chloropropyl) phosphate has the best flame-retardant effect, because it not only greatly reduces the combustion rate of carbonate solvent, but also reduces the peak temperature of flame and fuel, which significantly improves the safety of carbonate solvent.