(1. 湖南人文科技學(xué)院 化學(xué)與材料科學(xué)系，婁底 417000;
2. 中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 采用DSC和XRD方法研究了1 mol∙L−1 LiPF6電解液的熱行為，發(fā)現(xiàn)EMC和H2O降低了1 mol∙L−1 LiPF6 電解液(溶劑為EC\DML，質(zhì)量比為1׃1)的熱穩(wěn)定性。電解液熱分解反應(yīng)是EMC分解生成DEC和DMC，而DEC和DMC與LiPF6的分解產(chǎn)物PF5發(fā)生系列化學(xué)反應(yīng)，釋放大量反應(yīng)熱與氣體。由于可燃性電解液與Li0.5CoO2 的熱分解產(chǎn)物O2之間發(fā)生燃燒反應(yīng)，使Li0.5CoO2發(fā)生復(fù)雜的熱分解反應(yīng)。高溫下電解液與LiC6電極的熱反應(yīng)主要是：固體電解質(zhì)膜(SEI膜)的碎裂反應(yīng)，LiC6與粘結(jié)劑和電解液之間的反應(yīng)。熱反應(yīng)主要發(fā)生在石墨的表面，而石墨的晶形結(jié)構(gòu)在160 ℃熱反應(yīng)前后沒有變化。
關(guān)鍵字: 電解液；鋰離子電池；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
