Effects of solvents and salt on the thermal stability of charged LiCoO2

Lithium-ion batteries safety is an issue that should be solved. The thermal stability of Li{sub 0.5}CoO{sub 2} in the presence of solvents/electrolyte and LiPF{sub 6} salt were studied by using C80 micro-calorimeter in this paper. It was found that the thermal stability of Li{sub 0.5}CoO{sub 2} either in the presence of cyclic carbonate or linear carbonate is decreased greatly, especially for the linear carbonate-Li{sub 0.5}CoO{sub 2} coexisting system, and the thermal stability of dimethyl carbonate-Li{sub 0.5}CoO{sub 2} coexisting system is the least stable one. LiPF{sub 6} can prevent oxygen releasing from Li{sub 0.5}CoO{sub 2} at low temperature, but the delayed reaction will generate more heat at higher temperature. At last, thermal stability of two kinds of electrolytes with Li{sub 0.5}CoO{sub 2} was explored. The LiPF{sub 6}/ethylene carbonate + dimethyl carbonate + ethylmethyl carbonate-Li{sub 0.5}CoO{sub 2} system shows less thermal stability, which is attributed to the activity between dimethyl carbonate and Li{sub 0.5}CoO{sub 2}, as well as agree with the thermal experiment on dimethyl carbonate-Li{sub 0.5}CoO{sub 2} coexisting system.