Comparable Investigation of Phosphorus-Based Flame Retardant Electrolytes on LiFePO4 Cathodes

Improving the flame retardant and electrochemical properties of electrolytes is of great significance to enhance the safety of lithium-ion batteries (LIBs). In this work, the effect of cresyl diphenyl phosphate (CDP), dimethyl methyl phosphonate (DMMP), trimethyl phosphate (TMP) and triphenyl phosphate (TPP) as flame retardant additives in the standard electrolyte on the performance of LiFePO 4 /Li cell are comprehensively studied. The results show that when the mass fraction of flame retardant is less than 20%, the purpose of flame retardant can be achieved in the electrolyte. When the cells without and with 20 wt% of CDP, DMMP, TMP, and TPP additives are, respectively, their capacity retentions are 80, 46, 82, 84, and 57% after 100 cycles at 0.5C. According to characterization analysis, DMMP and TMP can facilitate the formation of stable interface films on cathode and subsequently improve the battery performance. Compared with expensive or complicated synthetic flame retardants, conventional flame retardants like CDP, DMMP, TMP, and TPP have great potential for application in electrolytes to improve the safety of LIBs. This work can provide useful scientific research and industry in the study of phosphorus-based flame retardant electrolytes.