Cresyl diphenyl phosphate effect on the thermal stabilities and electrochemical performances of electrodes in lithium ion battery

Abstract

To improve the safety of lithium ion battery, cresyl diphenyl phosphate (CDP) is used as a flame-retardant additive in a LiPF 6 based electrolyte. The electrochemical performances of LiCoO 2/CDP-electrolyte/Li and Li/CDP-electrolyte/C half cells are evaluated. The thermal behaviors of Li 0.5CoO 2 and Li 0.5CoO 2–CDP-electrolyte, and Li x C 6 and Li x C 6–CDP-electrolyte are examined using a C80 micro-calorimeter. For the LiCoO 2/CDP-electrolyte/Li cells, the onset temperature of single Li 0.5CoO 2 is put off and the heat generation is decreased greatly except the one corresponding to 5% CDP-containing electrolyte. When Li 0.5CoO 2 coexists with CDP-electrolyte, the thermal stability is enhanced. CDP improves the thermal stability of lithiated graphite anode effectively and the addition of 5% CDP inhibits the decomposition of solid electrolyte interphase (SEI) films significantly. The electrochemical tests on LiCoO 2/CDP-electrolyte/Li and Li/CDP-electrolyte/C cells show that when less than 15% CDP is added to the electrolyte, the electrochemical performances are not worsen too much. Therefore, the addition of 5–15% CDP to the electrolyte almost does not worsen the electrochemical performance of LiCoO 2 cathode and graphite anode, and improves theirs thermal stability significantly; thus, it is a possible choice for electrolyte additive.