Kim Soohwan, Seo Bumjoon, Ramasamy Hari Vignesh, Shang Zhongxia, Wang Haiyan, Savoie Brett M, Pol Vilas G
Davidson School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, United States.
School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, United States.
ACS Appl Mater Interfaces. 2022 Sep 21;14(37):41934-41944. doi: 10.1021/acsami.2c09338. Epub 2022 Sep 9.
Despite the essential role of ethylene carbonate (EC) in solid electrolyte interphase (SEI) formation, the high Li desolvation barrier and melting point (36 °C) of EC impede lithium-ion battery operation at low temperatures and induce sluggish Li reaction kinetics. Here, we demonstrate an EC-free high salt concentration electrolyte (HSCE) composed of lithium bis(fluorosulfonyl)imide salt and tetrahydrofuran solvent with enhanced subzero temperature operation originating from unusually rapid low-temperature Li transport. Experimental and theoretical characterizations reveal the dominance of intra-aggregate ion transport in the HSCE that enables efficient low-temperature transport by increasing the exchange rate of solvating counterions relative to that of solvent molecules. This electrolyte also produces a <5 nm thick anion-derived LiF-rich SEI layer with excellent graphite electrode compatibility and electrochemical performance at subzero temperature in half-cells. Full cells based on LiNiCoMnO||graphite with tailored HSCE electrolytes outperform state-of-the-art cells comprising conventional EC electrolytes during charge-discharge operation at an extreme temperature of -40 °C. These results demonstrate the opportunities for creating intrinsically robust low-temperature Li technology.
尽管碳酸亚乙酯（EC）在固体电解质界面（SEI）形成中起着至关重要的作用，但EC的高锂去溶剂化能垒和熔点（36°C）阻碍了锂离子电池在低温下的运行，并导致锂反应动力学迟缓。在此，我们展示了一种无EC的高盐浓度电解质（HSCE），它由双（氟磺酰）亚胺锂盐和四氢呋喃溶剂组成，具有增强的零下温度运行性能，这源于异常快速的低温锂传输。实验和理论表征揭示了HSCE中聚集体内离子传输的主导地位，通过提高溶剂化抗衡离子相对于溶剂分子的交换速率，实现了高效的低温传输。这种电解质还能产生厚度小于5nm的富含阴离子衍生LiF的SEI层，在零下温度的半电池中具有优异的石墨电极兼容性和电化学性能。基于LiNiCoMnO||石墨并采用定制HSCE电解质的全电池在-40°C的极端温度下进行充放电操作时，性能优于包含传统EC电解质的现有技术电池。这些结果证明了创造本质上强大的低温锂技术的机会。
