Electrochemical and thermal properties of 2,4,6-tris(trifluoromethyl)-1,3,5-triazine as a flame retardant additive in Li-ion batteries

Abstract

Triazines are well known as flame retardants, however, their properties for battery applications have not been much explored. Flame retardants can play an important role in preventing dangerous situations that may occur when battery packs malfunction or are misused. However, the addition of flame retardants to batteries can degrade their performance due to the non-ionic properties of the additives. In order to overcome this drawback of additives, fluorinated material has been investigated, because fluorination frequently prevents deterioration of performance. A fluoride-rich triazine used as an additive to the electrolyte, 2,4,6-tris(trifluoromethyl)-1,3,5-triazine (TTFMT), showed excellent thermal stability with charged cathodes and anodes. Addition of 5 wt.% TTFMT to the electrolyte reduced the exothermic heat from the oxygen release reaction in the cathode by 54%. Surface film formation on the cathode is discussed with reference to cyclic voltammetry combined with impedance spectroscopy and differential scanning calorimetry. The properties of the film were influenced by the additive so as to markedly reduce the charge-transfer resistance, which enhanced the charge retention during cycle life, the capacity, and the high-rate discharge capacity of the battery.