(1. 湖南人文科技学院 化学与材料科学系，娄底 417000;
2. 中南大学 冶金科学与工程学院，长沙 410083)
摘 要: 采用DSC和XRD方法研究了1 mol∙L−1 LiPF6电解液的热行为，发现EMC和H2O降低了1 mol∙L−1 LiPF6 电解液(溶剂为EC\DML，质量比为1׃1)的热稳定性。电解液热分解反应是EMC分解生成DEC和DMC，而DEC和DMC与LiPF6的分解产物PF5发生系列化学反应，释放大量反应热与气体。由于可燃性电解液与Li0.5CoO2 的热分解产物O2之间发生燃烧反应，使Li0.5CoO2发生复杂的热分解反应。高温下电解液与LiC6电极的热反应主要是：固体电解质膜(SEI膜)的碎裂反应，LiC6与粘结剂和电解液之间的反应。热反应主要发生在石墨的表面，而石墨的晶形结构在160 ℃热反应前后没有变化。
关键字: 电解液；锂离子电池；DSC
lithium ion batteries at elevated temperature
（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
