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Ionic Conduction and Solution Structure in LiPF6 and LiBF4 Propylene Carbonate Electrolytes
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-08-20 , DOI: 10.1021/acs.jpcc.8b06035
Sunwook Hwang , Dong-Hui Kim , Jeong Hee Shin , Jae Eun Jang , Kyoung Ho Ahn 1 , Chulhaeng Lee 1 , Hochun Lee
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-08-20 , DOI: 10.1021/acs.jpcc.8b06035
Sunwook Hwang , Dong-Hui Kim , Jeong Hee Shin , Jae Eun Jang , Kyoung Ho Ahn 1 , Chulhaeng Lee 1 , Hochun Lee
Affiliation
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Expanding the performance limit of current Li-ion batteries requires ion–ion and ion–solvent interaction, which governs the ion transport behavior of the electrolytes, to be fully understood as a matter of crucial importance. We herein examine the ionic speciation and conduction behavior of propylene carbonate (PC) electrolytes of 0.1–3.0 M LiPF6 and LiBF4 using Raman spectroscopy, dielectric relaxation spectroscopy (DRS), and pulsed-field gradient NMR (PFG-NMR) spectroscopy. In both LiPF6–PC and LiBF4–PC, free ions and a solvent-shared ion pair (SIP) are dominant species at dilute salt concentrations (<0.8 M), and SIP becomes dominant at intermediate concentrations (0.8–1.5 M). At higher concentrations (1.5–3.0 M), the solvent-shared dimer (SSD) and contact dimer (CD) are dominant in LiPF6–PC, whereas the contact ion pair (CIP), CD, and agglomerate (AGG) prevail in LiBF4–PC. Ionic conduction in 0.1–1.5 M LiPF6–PC and LiBF4–PC is governed by the migration of free ions and SIP. Notably, above 1.5 M of the two PC electrolytes, SSD participates in ionic conduction via the migration mode as well. Furthermore, it is suggested that the large number of CIPs present in LiBF4–PC may contribute to ionic conduction via a Grotthuss-type mechanism.
中文翻译：
LiPF 6和LiBF 4碳酸丙烯酯电解质中的离子传导和溶液结构
扩大当前锂离子电池的性能极限需要离子-离子和离子-溶剂的相互作用，这决定了电解质的离子传输行为，这是至关重要的。我们在这里使用拉曼光谱，介电弛豫光谱（DRS）和脉冲场梯度NMR（PFG-NMR）光谱检查了0.1–3.0 M LiPF 6和LiBF 4的碳酸亚丙酯（PC）电解质的离子形态和导电行为。在LiPF 6 –PC和LiBF 4中–PC，自由离子和溶剂共享离子对（SIP）在稀盐浓度（<0.8 M）时占优势，而SIP在中等浓度（0.8–1.5 M）时占优势。在较高浓度（1.5–3.0 M）下，LiPF 6 –PC中溶剂共享的二聚体（SSD）和接触二聚体（CD）占主导地位，而接触离子对（CIP），CD和团聚体（AGG）则占主导地位。 LiBF 4 –PC。0.1–1.5 M LiPF 6 –PC和LiBF 4 –PC中的离子传导受自由离子和SIP迁移的支配。值得注意的是，两种PC电解液中的1.5 M以上，SSD也会通过迁移模式参与离子传导。此外，建议在LiBF 4中存在大量CIP–PC可能通过Grotthuss型机制促进离子传导。
更新日期：2018-08-20
中文翻译：
LiPF 6和LiBF 4碳酸丙烯酯电解质中的离子传导和溶液结构
扩大当前锂离子电池的性能极限需要离子-离子和离子-溶剂的相互作用，这决定了电解质的离子传输行为，这是至关重要的。我们在这里使用拉曼光谱，介电弛豫光谱（DRS）和脉冲场梯度NMR（PFG-NMR）光谱检查了0.1–3.0 M LiPF 6和LiBF 4的碳酸亚丙酯（PC）电解质的离子形态和导电行为。在LiPF 6 –PC和LiBF 4中–PC，自由离子和溶剂共享离子对（SIP）在稀盐浓度（<0.8 M）时占优势，而SIP在中等浓度（0.8–1.5 M）时占优势。在较高浓度（1.5–3.0 M）下，LiPF 6 –PC中溶剂共享的二聚体（SSD）和接触二聚体（CD）占主导地位，而接触离子对（CIP），CD和团聚体（AGG）则占主导地位。 LiBF 4 –PC。0.1–1.5 M LiPF 6 –PC和LiBF 4 –PC中的离子传导受自由离子和SIP迁移的支配。值得注意的是，两种PC电解液中的1.5 M以上，SSD也会通过迁移模式参与离子传导。此外，建议在LiBF 4中存在大量CIP–PC可能通过Grotthuss型机制促进离子传导。
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