直接进样-电感耦合等离子体发射光谱(ICP-OES)法测定六氟磷酸锂电解液中17种杂质元素

电解液,被称为锂电池的血液,对锂离子电池的主要性能起着决定作用。六氟磷酸锂(LiPF_(6))是生产电解液的核心材料,电解液中的杂质离子会对电池性能造成极大的负面影响。因此,掌握锂离子六氟磷酸锂电解液中杂质元素的检测方法显得格外重要。传统的消解后测试的方法会造成部分元素损失,会引入新的污染,对低含量的元素难以准确定量,标准推荐的稀释剂需要用到电子级碳酸甲乙酯,成本较高。采用30%(V/V)乙醇水溶液稀释六氟磷酸锂电解液后直接进样,搭配电感耦合等离子体发射光谱(ICP-OES)有机进样系统,采用标准曲线法,测定了六氟磷酸锂电解液中的铝、砷、钙、镉、钴、铬、铜、铁、汞、钾、镁、钼、镍、钠、铅、硫、锌共17种杂质元素含量。实验中对ICP-OES最佳工作条件(包括雾化室温度、雾化气流量、雾化器、蠕动泵转速、电源功率、氧气流量)进行了优化,结果表明,雾化室温度在5℃,雾化气流量在0.6 L/min,使用的雾化器为OneNeb雾化器,蠕动泵转速为50 r/min,电源功率为1150 W,氧气流量为50 mL/min时,各元素的灵敏度、试液的消耗、耗材的磨损能达到最佳效果。结果表明,17种元素标准曲线的线性相关系数(r)不小于0.999,方法检出限在0.016~0.094 mg/L,精密度小于3.4%,加标回收率在90.2%~110%,不同稀释剂处理后的元素含量相对误差在5%以内,证明方法是分析六氟磷酸锂电解液中杂质元素有效、简单且快捷的方法。

Preparation and characterization of lithium hexafluorophosphate for lithium-ion battery electrolyte

A promising preparation method for lithium hexafluorophosphate(LiPF6)was introduced.Phosphorus pentafluoride(PF5) was first prepared using CaF2 and P2O5 at 280℃for 3 h.LiPF6 was synthesized in acetonitrile solvent by LiF and PF5 at room temperature(20-30℃)for 4 h.The synthesized LiPF6 was characterized by infrared spectrometry and X-ray diffraction(XRD). Atomic absorption and ion chromatography results show that the purity of synthesized LiPF6 reaches 99.98%.Thermal stability of self-synthesized LiPF6 was analyzed by differential thermal analysis and thermogravimetry.The results indicate that the self-synthesized LiPF6 has higher purity,lower impurity contents and better thermal stability than the commercial LiPF6.