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Safe, Stable Cycling of Lithium Metal Batteries with Low‐Viscosity, Fire‐Retardant Locally Concentrated Ionic Liquid Electrolytes
Author(s) -
Lee Sukhyung,
Park Kisung,
Koo Bonhyeop,
Park Changhun,
Jang Minchul,
Lee Hongkyung,
Lee Hochun
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202003132
Subject(s) - electrolyte , materials science , ionic liquid , anode , faraday efficiency , chemical engineering , lithium (medication) , thermal stability , separator (oil production) , inorganic chemistry , organic chemistry , electrode , chemistry , medicine , engineering , endocrinology , catalysis , physics , thermodynamics
Ionic liquid (IL) electrolytes with concentrated Li salt can ensure safe, high‐performance Li metal batteries (LMBs) but suffer from high viscosity and poor ionic transport. A locally concentrated IL (LCIL) electrolyte with a non‐solvating, fire‐retardant hydrofluoroether (HFE) is presented. This rationally designed electrolyte employs lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 1‐methyl‐1‐propyl pyrrolidinium bis(fluorosulfonyl)imide (P13FSI) and 1,1,2,2‐tetrafluoroethyl 2,2,3,3‐tetrafluoropropyl ether (TTE) as the IL and HFE, respectively (1:2:2 by mol). Adding TTE enables a Li‐concentrated IL electrolyte with low viscosity and good separator wettability, facilitating Li‐ion transport to the Li metal anode. The non‐flammability of TTE contributes to excellent thermal stability. Furthermore, synergy between the dual (FSI/TFSI) anions in the LCIL electrolyte can help modify the solid electrolyte interphase, increasing Li Coulombic efficiency and decreasing dendritic Li deposition. LMBs (Li||LiCoO 2 ) employing the LCIL electrolyte exhibit good rate capability (≈89 mAh g −1 at 1.8 mA cm −2 , room temperature) and long‐term cycling (≈80% retention after 400 cycles).