ISSN: 1003-6326
CN: 43-1239/TG

Vol. 17    No. 4    April 2007

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Reactions between electrolyte and electrode of
lithium ion batteries at elevated temperature
HU Chuan-yue1, LI Xin-hai2, GUO Jun1, WANG Xing-yan1, YI Tao1
(1. Department of Chemistry and Material Science, Hunan Institute of Humanities,
Science and Technology, Loudi 417000, China;
2. School of Metallurgy Science and Engineering, Central South University, Changsha 410083, China
Abstract: Reactions between Li0.5CoO2 electrode and 1 mol∙L−1 LiPF6 electrolyte at elevated temperature for lithium ion batteries were studied with differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results show that the thermal stability of 1 mol∙L−1 LiPF6 ethylene carbonate (EC)-dimethyl carbonate(DMC)(1׃1, mass ratio) electrolyte decreases by the impurity H2O and ethylmethyl carbonate (EMC) solvent. DEC and DMC are produced from the thermal decomposition reaction of EMC. A large amount of gases and heat are produced through series of chemical reactions among DEC and DMC and PF5 from decomposition of LiPF6. In the presence of sufficient electrolyte, the decomposition reactions of Li0.5CoO2 proceeds in a clear stepwise manner through solid phases as a function of temperature. Electrolyte combustion reactions take place due to the evolved oxygen from the decomposition of Li0.5CoO2 that releases large amounts of heat. The thermal reactions between electrolyte and LiC6 electrode of lithium ion batteries at elevated temperature includes the chipping reaction of solid electrolyte interface (SEI) film, the reaction between electrolyte and LiC6 and the reaction between adhesives and LiC6. However, the crystal structure of graphite does not change after thermal reaction at 160 ℃.
Key words: electrolytes; lithium-ion batteries; differential scanning calorimeter
Superintended by The China Association for Science and Technology (CAST)
Sponsored by The Nonferrous Metals Society of China (NFSOC)
Managed by Central South University (CSU)