锂电池电解质草酸二氟硼酸锂水解过程及其对理化性能的影响

Hydrolysis and influences on physical and chemical properties for lithium battery electrolyte LiODFB

通过元素分析、红外(FTIR)对自制的高纯草酸二氟硼酸锂(LiODFB)的化学结构和成分进行分析和表征,通过水分暴露实验和电池性能测试综合对比分析LiODFB与LiPF6的水分敏感性和理化性能。研究结果表明:自制LiODFB的元素含量和理论值基本吻合,纯度达到99.93%;各化学键的红外吸收峰都存在,并且未见其他杂质峰;LiODFB在25℃和50%湿度下暴露2 h后,吸潮形成LiODFB.H2O,随暴露时间延长,发生水解反应,生成复杂化合物;LiPF6在25℃和50%湿度下暴露,迅速反应生成LiF和Li3PO4等,同时放出HF气体;电池的放电容量和容量保持率均随着LiODFB和LiPF6的暴露时间延长而变差,在暴露时间相同时,与采用LiPF6的基电解液相比,采用LiODFB基电解液的电池的容量和容量保持率均明显较高。

The chemical structure,composition and phase of the self-made high-purity LiODFB were systematically analyzed and characterized by Fourier transform infrared（FTIR） and elementary analysis.The sensitivity of water and physicochemical properties of LiODFB and LiPF6 were investigated by water exposure experiment and battery performance test.The results show that the element contents of the self-made sample are basically consist with the theoretical values,and the purity is 99.93%.The infrared absorption peaks of the chemical bonds are all present,and no other impurity peaks exist.LiODFB would first absorb moisture to form LiODFB.H2O,then be hydrolyzed to produce complex compound when exposed to 25 ℃,50% humidity.Under the same conditions,LiPF6 is decomposed into LiF,Li3PO4 and HF.The battery performance of the exposed sample gets worse while prolonging the exposed time of the LiODFB and LiPF6.The capacity and capacity retention of the battery with LiODFB-based electrolyte are obviously better than those of the battery with LiPF6-based electrolyte.