A study on the effects of vinylene carbonate and fluoroethylene carbonate on thermal runaway in lithium-ion batteries

Vinylene carbonate (VC) and fluoroethylene carbonate (FEC) are widely used to enhance the cycle life of lithium-ion battery (LIB) anodes. However, their effects on the thermal runaway behavior of LIBs remain unclear. This study investigates the impact of VC and FEC on the electrolyte pyrolysis behaviors and gas production characteristics. The electrolyte, consisting of 1 mol/L LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), is analyzed under varying pyrolysis temperatures and durations. VC and FEC are added separately at mass fractions of 1 %, 2 %, and 3 % to assess their influence on the decomposition process. The results indicate that, without the additives, the gas volume produced from the electrolyte at 180 degrees C is 1307.2 mL. The addition of VC and FEC reduces the overall gas volume, suggesting that these additives inhibit the decomposition of the electrolyte. However, the gas compositions become more complex with the presence of the additives, leading to the formation of aldehyde and ester compounds. Notably, higher mass fractions of VC result in an increased concentration of flammable gases, thereby elevating the potential risk of thermal runaway. Finally, the decomposition mechanisms and the potential products formed by the solvents (EC, DMC, EMC) and additives (VC and FEC) are analyzed.