天津大学罗加严团队探明了低温下利用局部高浓度电解质中的离子配对和输运实现可逆锂金属阳极。相关研究成果发表在2024年7月20日出版的《德国应用化学》。

-40°C以下的锂金属阳极很少能达到99%以上的库仑效率，这阻碍了高能量密度锂金属电池在极端条件下的实际应用。

该文利用不同溶剂-稀释剂组合的醚基局部高浓度电解质，研究了锂金属可逆性的限制因素。研究发现，除了去溶剂化势垒外，体离子传输特性，包括离子电导率、迁移数和扩散率，也是低温锂沉积行为的关键因素。在具有中等弱溶剂化能力的溶剂和具有最小粘度的稀释剂的组合中，观察到优异的锂金属可逆性，突出了离子传输的作用以及与去溶剂化进行权衡的必要性。

由双（氟磺酰基）酰亚胺锂、甲基正丙基醚和1,1,2,2-四氟乙基甲基醚组成的优化电解质，在电流密度为0.5mA cm^-2的情况下，在-40°C和-60°C下分别具有99.34%和98.96%的库仑效率。此外，Li||LiCoO₂（2.7 mAh cm^-2）电池在这些温度下表现出令人印象深刻的可逆容量和循环稳定性。

该项工作揭示了体离子传输与低温性能的相关性，并为在寒冷环境中运行的锂金属电池的电解质设计提供了指导。

附：英文原文

Title: Leveraging Ion Pairing and Transport in Localized High-Concentration Electrolytes for Reversible Lithium Metal Anodes at Low Temperatures

Author: Zhengfei Zhao, Aoxuan Wang, Aosai Chen, Yumeng Zhao, Zhenglin Hu, Kai Wu, Jiayan Luo

Issue&Volume: 2024-07-20

Abstract: Coulombic efficiency of over 99% is rarely achieved for Li metal anode below -40°C, hindering the practical application of high-energy-density Li metal batteries under extreme conditions. Herein, limiting factors for Li metal reversibility are investigated utilizing ether-based localized high-concentration electrolytes of different solvent-diluent combinations. We find that along with the desolvation barrier, bulk ion transport properties including ionic conductivity, transference number, and diffusivity are also crucial factors for low-temperature Li deposition behavior. Superior Li metal reversibility was observed within the combination of the solvent with moderately weak solvating power and the diluent with minimal viscosity, highlighting the role of ion transport and the necessity for a trade-off with desolvation. The optimized electrolyte composed of lithium bis(fluorosulfonyl)imide, methyl n-propyl ether, and 1,1,2,2-tetrafluoroethyl methyl ether delivers exceptional Coulombic efficiency of 99.34% at -40°C and 98.96% at -60°C under a current density of 0.5 mA cm-2. Furthermore, Li||LiCoO2 (2.7 mAh cm-2) cells demonstrate impressive reversible capacity and cycling stability at these temperatures. This work sheds light on the less-recognized relevance of bulk ion transport to low-temperature performance and provides guidelines for the electrolyte design of Li metal batteries operating in cold environments.

DOI: 10.1002/anie.202412239

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202412239