高氯酸消解-ICP-OES测定炭复合磷酸铁锂中的锂、铁、磷

Determination of Lithium,Iron and Phosphorus in Carbon Composite Lithium Iron Phosphate by Perchloric Acid Digestion-Inductively Coupled Plasma Optical Emission Spectrometry

磷酸铁锂是锂电行业主要的产业化原料之一,与传统钴酸锂相比,在比能量、寿命、成本、环境兼容性上有显著优势。以锂离子电池用正极材料炭复合磷酸铁锂为研究对象,采用电感耦合等离子体发生光谱仪(ICP-OES)同时测定其中的锂、铁、磷含量。对样品消解、谱线选择、仪器工作参数、溶剂效应消除、谱线背景干扰消除、分析方法正确度、精密度进行了讨论。炭复合磷酸铁锂样品中含约5%的碳单质,0.1 g样品用5 mL高氯酸加热消解至目视澄清后,再反复加蒸馏水-加热冒烟2次,可完全消解。样品消解情况用三维视频显微镜确认,目视澄清的消解液经30倍放大后,仍可见有未消解的颗粒物;继续加蒸馏水-加热冒烟2次后,消解液经30倍放大观察,确认样品已消解完全。消解后的试液定容至100 mL,按10∶100稀释,得到同时测定锂、铁、磷含量的溶液。样品消解仅使用高氯酸一种试剂,操作便捷,样品中的碳单质被完全消解,消除了碳单质包覆样品对测定结果准确性的影响。仪器最佳工作条件为:高频功率:1.1 kW;雾化器流量:0.8 L·min^(-1);分析谱线-观测方向/高度:Li610.365 nm-轴向、Fe259.940 nm-径向/12 mm、P178.222 nm-轴向、P213.618 nm-径向/12 mm。使用随样品消解同时处理的试剂空白,按基体匹配法配制标准溶液,能最大程度减小溶剂基质效应。对于Li610.365 nm使用快速自动曲线拟合技术(FACT)消除仪器工作气体氩气的Ar610.564 nm背景干扰,显著提高校准曲线的线性系数及分析精密度。在仪器最佳工作条件下,测定范围为锂1%~9%,铁20%~40%,磷10%~30%;校准曲线线性关系系数r>0.9990;重复测定样品的相对标准偏差(RSD,n=7)在0.35%~1.01%之间;加标回收率在91.2%~112%之间;实验室双人内部循环(IRR)结果使用F,t(双样本异方差假设)检验进行差异性评价,两人平行试验结果无明显差异。分析方法具有推广应用价值。

Lithium iron phosphate is one of the main industrial raw materials for the lithium-ion polymer battery industry.Compared with traditional raw material lithium cobalt oxides,lithium iron phosphate has significant advantages in specific energy,battery life,cost and environmental compatibility.Lithium iron phosphate,which is carbon composite cathode material for lithium-ion batteries,is selected as the research object.The content of lithium,iron and phosphorus was determined simultaneously by inductively coupled plasma optical emission spectrometry(ICP-OES).Sample digestion,analytical wavelength,parameters of instrument,solvent effect,background interference for analytical wavelength,accuracy and precision of the method had been discussed.Carbon composite lithium iron phosphate contains about 5%carbon.0.100 g Sample was digested with 5 mL perchloric acid,heated the digestion solution to clarify visual,and continued heated the solution to smoke and repeated the operation twice as the sample could be digested completely.The sample digestion was checked by the three-dimensional(3D)video microscope.The visual clarify solution was checked by 30 magnification times.It showed that there still had an insoluble matter in the solution.After repeated the operation of added water and continue heated to smoke twice,checked digestion solution by 30 magnification times again;it showed that the sample had been digested completely.The digestion solution was transferred to a 100 mL volumetric flask,diluted to volume and mixed.The analytical solution was prepared as followed:diluted the constant volume digestion solution with the rate of 10∶100 to a 100 mL volumetric flask.The best parameters of ICP-OES for this method were:High-frequency power,1.1 kW.Atomizer flow:0.8 L·min^(-1).Analytical wavelength,observe direction&observe height:Li610.365 nm-axial,Fe259.940 nm-radial/12 mm,P178.222 nm-axial,P213.618 nm-radial/12mm.Calibration solutions were prepared according to matrix matching with regent blank prepared with sample simultaneously,the preparation of calibration solution can minimize the solvent effect.For Li 610.365 nm,fast,automated curve-fitting(FACT)was used to eliminate background interference of Ar 610.564 nm.Under the optimal conditions,the analytical ranges were:Li,1%~9%,Fe,20%~40%,P,10%~30%.The coefficient of the calibration curve,r>0.9990.The relative standard deviation(RSD,n=7)was 0.35%~1.01%.The standard recovery rate was 91.2%~112%.Internal round robins(IRR)result was evaluated by F,t-test,the result showed no obvious difference between the test results of two operators.The method has promotional value for application in the lithium-ion polymer battery industry.