Synthesis Of Bis (2,2,2-trifluoroethyl) Carbonate And Its Application In Lithium-ion Battery

Nowadays battery safety performance requirements are high, especially for people electric vehicles, hybrid electric vehicles and high-capacity storage battery needs. Safety performance of the battery is difficult with changing the positive and negative battery materials to improve, so adding some flame retardants to the electrolyte to improve safety performance of the battery is currently a hot research. Fluoro-carbonate such as bis (2,2,2-trifluoroethyl) carbonate (TFEC) as an electrolyte additive can significantly improve the safety performance of the battery.In this paper, with DPC and CF3CH2OH as raw materials using transesterification to synthesize a new lithium-ion battery flame-bis (2,2,2-trifluoroethyl) carbonate (TFEC) to select the best reaction conditions among catalyst, amount of catalyst, reaction time, temperature, material ratio such as the impact of various factors on the reaction. Then by adding different proportions TFEC to the battery to research the amount of TFEC impacting on the battery including the conductivity of the electrolyte, self-extinguishing time of combustion; investigated for the battery capacity, charge-discharge characteristics, cycle characteristics impact resistance; the performance in terms of the main battery overcharge protection test, acupuncture test and thermal shock experiments and other research, were studied in order to select the best of TFEC dosage.First, researching reaction conditions including the conversion of the DPC, the yield and selectivity of TFEC, choosing sodium hydride as catalyst efficiency, m (NaH):m (DPC)=1.0%, the reaction mass ratio of n(DPC):n (TFET-OH)=1:4, the reaction time is 8 hours and the reaction temperature is 120 ℃. Under optimum conditions the conversion rate of DPC is 67.8%, yield of TFEC is 51.1%, selectivity of TFEC is 75.4%, purity of TFEC is 99.5% after purification, the water content of TFEC is 150 ppm less than 200ppm.Secondly, the electrochemical performance of the battery by adding TFEC is researched. Adding an appropriate amount of electrolyte can improve conductivity of the electrolyte TFEC. But when the amount exceeds 5 wt.%, the conductivity decreased. This can be obtained from the AC impedance spectra of the verification, when the additive content of 5 wt.% has the minimum resistance, when the additive content at 20 wt.% internal resistance of battery is larger than without additives. Excess TFEC additive adding to the battery capacity has a negative effect, when the doping amount of TFEC exceeds 5 wt%, the battery capacity is significantly decreased; TFEC doping a small magnification for the battery (0.5C) charge and discharge 100 cycles, no negative effect; different rate charge and discharge test indicates TFEC has no significant effect for the low rate charge and discharge, but in the high-rate discharge conditions, the battery capacity significantly reduces decay rate, significantly improving discharge platform; cyclic voltammograms Ann curve shows a small amount of TFEC helps reduce oxidation peak and reduction peak potential difference, so that the oxidation peak current and peak current ratio is closer to 1. Adding a small amount of TFEC help to improve the cycle performance of the battery, when the doping amount of 5 wt.% shows the best cycling performance, but when the doping amount exceeds 5 wt.% is not conducive to improve the cycle performance of the battery.Further, the impact of TFEC on the safety performance of battery is studied. TFEC can significantly reduce the electrolyte self-extinguishing burning time, and the greater amount of TFEC dropping,the less electrolyte burning time is more obvious; TFEC can significantly improve the oxidation potential of the battery under charge conditions in the past (750mA,6V) of to improve the characteristics of the battery voltage, the greater the pressure and the doping amount of performance improvement is more obvious; Experiments show that adding acupuncture can significantly reduce the temperature of the battery under short-circuit conditions, and the more the amount of TFEC added, the temperature reducing is the more obvious; under high temperature conditions of heat shock experiments show TFEC can significantly improve battery endurance time, when adding 20 wt.% TFEC comparing without TFEC increased 73%. Integrated self-extinguishing electrolyte combustion experiments, anti-overcharge test, acupuncture test and thermal shock test are analyzed, show that TFEC can significantly improve battery safety performance. Comprehensive analysis TFEC electrochemical performance of the battery with the safety effect of the performance, the amount of TFEC is 5 wt.% for the best.