Abstract：The content of free acid in the electrolyte of lithium hexafluorophosphate (LiPF6) is an important index influencing the performance of lithium-ion battery, so it should be timely determined. Since the thermal stability of LiPF6 electrolyte is poor and easily hydrolyzed at room temperature, a method for the determination of free acid content in LiPF6 electrolyte by linear titration with equal addition amount was proposed at low temperature. Hydrofluoric acid-carbonate ester solution was used as testing objective in experiments. The formation constant of hydrofluoric acid at 0 ℃ was determined and used as the basis for the subsequent calculations. The measurement temperature was controlled to be about 0 ℃. Then 0.50 mol/L KCl solution was mixed with LiPF6 electrolyte sample at the volume ratio of 1∶1 to prepare the testing solution. 0.010 mol/L NaOH standard solution was used as the titrant, and pH 7.0 was the endpoint. Johansson function was used for calculation and plotting to obtain the endpoint of titration. Finally, the content of free acid in electrolyte was obtained. The effect of common additives and carbonate solvents in LiPF6 electrolyte on the determination was discussed. The results showed that their influences could be ignored. The proposed method was applied for the analysis of actual samples, and the found results were basically consistent with those obtained by the potentiometric titration. The relative standard deviations (RSD, n = 5) of determination results were between 0.35% and 1.1%, and the spiked recoveries were between 99.6% and 101%.
陈田田, 唐卓, 金玲, 靳素荣, 蔡宏伟. 线性滴定法测定六氟磷酸锂电解液中游离酸[J]. 冶金分析, 2022, 42(2): 47-52.
CHEN Tiantian, TANG Zhuo, JIN Ling, JIN Surong, CAI Hongwei. Determination of free acid in lithium hexafluorophosphate electrolyte by linear titration. , 2022, 42(2): 47-52.
[1] Choi S,Wang G.Advanced lithium-ion batteries for practical applications:technology,development,and future perspectives[J].Advanced Materials Technologies,2018,3(9):116-118. [2] Stich M,Goettlinger M,Kurniawan M,et al.Hydrolysis of LiPF6 in carbonate-based electrolytes for lithium-ion batteries and in aqueous media[J].Journal of Physical Chemistry C,2018,122(16):8836-8842. [3] Kawamura T,Kimura A,Egashira M,et al.Thermal stability of alkyl carbonate mixed-solvent electrolytes for lithium ion cells[J].Journal of Power Sources,2002,104(2):260-264. [4] Handel P,Fauler G,Kapper K,et al.Thermal aging of electrolytes used in lithium-ion batteries-An investigation of the impact of protic impurities and different housing materials[J].Journal of Power Sources,2014,267:255-259. [5] Wang Q,Jiang L,Yu Y,et al.Progress of enhancing the safety of lithium ion battery from the electrolyte aspect[J].Nano Energy,2019,55(1):93-114. [6] 中华人民共和国工业和信息部.SJ/T 11723—2018锂离子电池用电解液[S].北京:中国标准出版社,2018. [7] 左晓希,苏达根,李伟善,等.锂离子蓄电池电解液中氢氟酸的定量分析[J].电源技术,2006,30(1):66-69. ZUO Xiaoxi,SU Dagen,LI Weishan,et al.Quantitative analysis of HF content in electrolyte for Li-ion battery[J].Chinese Journal of Power Sources,2006,30(1):66-69. [8] Huang C R,Shen C C,Jin L,et al.The determination of trace free acid content in lithium-ion battery electrolytes by coulometric titration in non-aqueous media[J].Analyst,2020,145(2):582-587. [9] Lux S F,Lucas I T,Pollak E,et al.The mechanism of HF formation in LiPF6 based organic carbonate electrolytes[J].Electrochemistry Communications,2011,14(1):47-50. [10] G 杜格拉德,J-F 马丁.用于检测并测定锂电池的包含六氟磷酸锂LiPF6的电解液内的氢氟酸的方法:中国,CN104781647A[P].2015-07-15. [11] 张云.计算滴定分析法的分类及其进展[J].分析科学学报,2006,22(6):731-736. ZHANG Yun.Classification and development of calculating titrimetric analysis[J].Journal of Analytical Science,2006,22(6):731-736. [12] Jiang X,Chen L,Zhong W.A new linear potentiometric titration method for the determination of deacetylation degree of chitosan[J].Carbohydrate Polymers,2003,54(4):457-463. [13] Matsushita Kuan.Simultaneous estimation of the dissociation constant and concentration by the linear titrimetry[J].The Chemical Society of Japan,1976,25(8):1322-1325.
