Improved Stability and Rate Capability of Ionic Liquid Electrolyte with High Concentration of LiFSI
Improved Stability and Rate Capability of Ionic Liquid Electrolyte with High Concentration of LiFSI
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DOI：
10.1149/2.0381910jes
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发表时间：
2019
影响因子：
3.9
通讯作者：
Ashley M. Heist;Sehee Lee
中科院分区：
文献类型：
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作者：
Ashley M. Heist;Sehee Lee
离子液体（IL）电解质提供了优于常规碳酸盐基电解质的许多优点，但由于其相对低的离子电导率和高粘度，通常在高充电和放电速率下具有较差的性能。虽然增加IL电解质的锂盐含量超过最佳水平会加剧这两种特征，但这项工作证明了高度浓缩的IL电解质的惊人动力学能力。本文呈现的结果显示，与较低浓度的IL溶液相比，在具有高浓度LiFSI的PYR 13 FSI中循环的NMC-811半电池表现出优异的上级倍率性能。此外，延长的循环表明，较高的LiFSI浓度促进了长期循环期间的稳定性增强，显著优于常规有机电解质的能力。迁移数计算，微分容量分析和电化学阻抗谱被用来阐明在高浓度下有助于性能改善的潜在机制，最终揭示了LiFSI摩尔浓度在形成能够促进快速锂离子传输以及稳定的长期循环的坚固和导电的固体电解质界面层中的重要性。这项研究的结果突出了IL电解质的独特能力，使成功实施具有挑战性的高能量电极材料。
Ionic liquid (IL) electrolytes offer a number of advantages over conventional carbonate-based electrolytes but commonly suffer from poor performance at high charge and discharge rates due to their relatively low ionic conductivity and high viscosity. While increasing the lithium salt content of an IL electrolyte beyond optimal levels exacerbates both of those characteristics, this work demonstrates the surprising kinetic capabilities of highly concentrated IL electrolytes. Results presented herein show that NMC-811 half-cells cycled in PYR 13 FSI with a high-concentration of LiFSI exhibit superior rate performance as compared to lower-concentration IL solutions. Furthermore, extended cycling shows that higher LiFSI concentrations promote enhanced stability during long-term cycling, significantly outperforming the capabilities of a conventional organic electrolyte. Transference number calculations, differential capacity analyses, and electrochemical impedance spectroscopy were used to illuminate the underlying mechanisms contributing to the performance improvements at high concentrations, ultimately revealing the significance of LiFSI molarity in the formation of a robust and conductive solid-electrolyte interphase layer capable of promoting rapid lithium-ion transport as well as stable long-term cycling. The results of this study highlight the unique capability of IL electrolytes to enable successful implementation of a challenging high-energy electrode material.