Journal
ADVANCED MATERIALS
Volume 33, Issue 25, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202008619
Keywords
anode‐ free batteries; Coulombic efficiency; electrolytes; fluorinated solvents; Li‐ metal batteries
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Funding
- U.S. Department of Energy, under the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies
- Battery Materials Research (BMR) Program, and Battery 500 Consortium
- National Science Foundation [ECCS-1542152]
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Novel electrolyte designs, including fluorinated 1,6-dimethoxyhexane and 1,2-dimethoxyethane as solvent molecules, along with lithium bis(fluorosulfonyl)imide, enable high-performance lithium metal batteries with improved stability and ionic conductivity. The use of a dual-solvent system contributes to the anion-derived solid-electrolyte interphase and enhances the overall battery performance.
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 -CF2- 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 mu m Li||NMC batteries are able to retain approximate to 80% capacity after 250 cycles and Cu||NMC anode-free pouch cells last 120 cycles with 75% capacity retention under approximate to 2.1 mu L mAh(-1) 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.
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