Christopher Behling , Janik Lüchtefeld , Karl J.J. Mayrhofer , Balázs B. Berkes
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In this work, we examine the influence of lithium hexafluorophosphate (LiPF<sub>6</sub>) addition to LiTFSI-based electrolytes via cyclic voltammetry (CV) in an electroanalytical flow cell (EFC) coupled on-line to an inductively coupled plasma mass spectrometer (ICP-MS) for continuous downstream elemental analysis. This setup allows the potential resolved quantification of Al dissolution with unprecedented precision in real-time. With that, we found that already very small amounts of 0.02 M LiPF<sub>6</sub> added to 0.98 M LiTFSI will drastically reduce the total dissolved amount of Al during one CV cycle by a factor of ∼ 20, while electrolytes containing 0.30 M LiPF<sub>6</sub> (and 0.70 M LiTFSI) completely suppress the dissolution of Al. 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引用次数: 0
摘要
双(三氟甲烷磺酰)亚胺锂(LiTFSI)具有更高的稳定性和离子导电性,是未来锂离子电池(LIB)电解质的理想候选材料。然而,这种盐的一个主要缺点是能够溶解铝,从而导致锂离子电池中的电流收集器随着时间的推移而退化。表面钝化添加剂可以减少甚至完全抑制溶解。然而,只有确定理想的(即最小的)添加剂用量,才能实现真正具有成本和材料效益的抑制作用。因此,有必要对添加剂的溶解抑制效果进行量化,以创建最佳的电解质混合物。在这项工作中,我们通过在电分析流动池(EFC)中与电感耦合等离子体质谱仪(ICP-MS)在线耦合的循环伏安法(CV)来研究六氟磷酸锂(LiPF6)添加到基于 LiTFSI 的电解质中对下游元素进行连续分析的影响。这种装置可以对铝的溶解进行前所未有的实时精确定量。我们发现,在 0.98 M LiTFSI 中加入极少量的 0.02 M LiPF6 就能在一个 CV 循环中将铝的总溶解量大幅减少 ∼ 20 倍,而含有 0.30 M LiPF6(和 0.70 M LiTFSI)的电解质则能完全抑制铝的溶解。这些发现允许替代大量的 LiPF6,从而能够生产出更安全的 LIB,而不会有集流器降解的风险。
Quantitative evaluation of LiPF6 as corrosion inhibiting additive for Al in LiTFSI-based battery electrolytes – An on-line mass spectrometric study
Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is a promising candidate for future lithium-ion battery (LIB) electrolytes because of its increased stability and ionic conductivity. One major drawback of this salt, however, is its ability to dissolve Al, leading to a degradation of current collectors in LIBs over time. Surface passivating additives can reduce or even completely suppress the dissolution. A truly cost and material-efficient suppression, however, can only be achieved by identifying the ideal (i.e., minimal) amount of additive. Therefore, quantifying the dissolution-suppressing effect of additives is necessary to create an optimum electrolyte mixture. In this work, we examine the influence of lithium hexafluorophosphate (LiPF6) addition to LiTFSI-based electrolytes via cyclic voltammetry (CV) in an electroanalytical flow cell (EFC) coupled on-line to an inductively coupled plasma mass spectrometer (ICP-MS) for continuous downstream elemental analysis. This setup allows the potential resolved quantification of Al dissolution with unprecedented precision in real-time. With that, we found that already very small amounts of 0.02 M LiPF6 added to 0.98 M LiTFSI will drastically reduce the total dissolved amount of Al during one CV cycle by a factor of ∼ 20, while electrolytes containing 0.30 M LiPF6 (and 0.70 M LiTFSI) completely suppress the dissolution of Al. These findings allow the substitution of large portions of LiPF6, enabling the production of safer LIBs without risking current collector degradation.
期刊介绍:
Electrochemistry Communications is an open access journal providing fast dissemination of short communications, full communications and mini reviews covering the whole field of electrochemistry which merit urgent publication. Short communications are limited to a maximum of 20,000 characters (including spaces) while full communications and mini reviews are limited to 25,000 characters (including spaces). Supplementary information is permitted for full communications and mini reviews but not for short communications. We aim to be the fastest journal in electrochemistry for these types of papers.