Wang Hansen, Yu Zhiao, Kong Xian, Huang William, Zhang Zewen, Mackanic David G, Huang Xinyi, Qin Jian, Bao Zhenan, Cui Yi
Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA.
Department of Chemical Engineering, Stanford University, Stanford, CA, 94305, USA.
Adv Mater. 2021 Jun;33(25):e2008619. doi: 10.1002/adma.202008619. Epub 2021 May 9.
Novel electrolyte designs to further enhance the lithium (Li) metal battery cyclability are highly desirable. Here, fluorinated 1,6-dimethoxyhexane (FDMH) is designed and synthesized as the solvent molecule to promote electrolyte stability with its prolonged -CF - backbone. Meanwhile, 1,2-dimethoxyethane is used as a co-solvent to enable higher ionic conductivity and much reduced interfacial resistance. Combining the dual-solvent system with 1 m lithium bis(fluorosulfonyl)imide (LiFSI), high Li-metal Coulombic efficiency (99.5%) and oxidative stability (6 V) are achieved. Using this electrolyte, 20 µm Li||NMC batteries are able to retain ≈80% capacity after 250 cycles and Cu||NMC anode-free pouch cells last 120 cycles with 75% capacity retention under ≈2.1 µL mAh lean electrolyte conditions. Such high performances are attributed to the anion-derived solid-electrolyte interphase, originating from the coordination of Li-ions to the highly stable FDMH and multiple anions in their solvation environments. This work demonstrates a new electrolyte design strategy that enables high-performance Li-metal batteries with multisolvent Li-ion solvation with rationally optimized molecular structure and ratio.
非常需要新颖的电解质设计来进一步提高锂金属电池的循环性能。在此，设计并合成了氟化1,6-二甲氧基己烷（FDMH）作为溶剂分子，以通过其延长的-CF-主链来提高电解质稳定性。同时，使用1,2-二甲氧基乙烷作为共溶剂，以实现更高的离子电导率并大大降低界面电阻。将双溶剂体系与1 m双（氟磺酰）亚胺锂（LiFSI）相结合，可实现高锂金属库仑效率（99.5%）和氧化稳定性（6 V）。使用这种电解质，20 µm Li||NMC电池在250次循环后能够保持约80%的容量，而Cu||NMC无阳极软包电池在约2.1 µL mAh贫电解质条件下可进行120次循环，容量保持率为75%。这些高性能归因于源自锂离子与溶剂化环境中高度稳定的FDMH和多种阴离子配位的阴离子衍生固体电解质界面。这项工作展示了一种新的电解质设计策略，可以实现具有合理优化分子结构和比例的多溶剂锂离子溶剂化的高性能锂金属电池。
