Enhanced Li⁺ Transport in Ionic Liquid‐Based Electrolytes Aided by Fluorinated Ethers for Highly Efficient Lithium Metal Batteries with Improved Rate Capability

Abstract

FSI − -based ionic liquids (ILs) are promising electrolyte candidates for longlife and safe lithium metal batteries (LMBs). However, their practical application is hindered by sluggish Li + transport at room temperature. Herein, it is shown that additions of bis(2,2,2-trifluoroethyl) ether (BTFE) to LiFSI-Pyr 14 FSI ILs can effectively mitigate this shortcoming, while maintaining ILs′ high compatibility with lithium metal. Raman spectroscopy and small-angle X-ray scattering indicate that the promoted Li + transport in the optimized electrolyte, [LiFSI] 3 [Pyr 14 FSI] 4 [BTFE] 4 (Li 3 Py 4 BT 4 ), originates from the reduced solution viscosity and increased formation of Li + -FSI − complexes, which are associated with the low viscosity and non-coordinating character of BTFE. As a result, Li/LiFePO 4 (LFP) cells using Li 3 Py 4 BT 4 electrolyte reach 150 mAh g −1 at 1 C rate (1 mA cm −2 ) and a capacity retention of 94.6% after 400 cycles, revealing better characteristics with respect to the cells employing the LiFSI-Pyr 14 FSI (operate only a few cycles) and commercial carbonate (80% retention after only 218 cycles) electrolytes. A wide operating temperature (from −10 to 40 °C) of the Li/Li 3 Py 4 BT 4 /LFP cells and a good compatibility of Li 3 Py 4 BT 4 with LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC532) are demonstrated also. The insight into the enhanced Li + transport and solid electrolyte interphase characteristics suggests valuable information to develop IL-based electrolytes for LMBs.The ORCID identification number(s) for the author(s) of this article can be found under

An Ionic Liquid Electrolyte with Enhanced Li+ Transport Ability Enables Stable Li Deposition for High‐Performance Li‐O2 Batteries

“…Results show that every single parameter influenced the Li + draining phenomenon and dominated Li deposition behavior in the way mentioned above.T herefore,rationally improving the Sandstime of electrolyte could effectively enhance the LTAo fe lectrolytes and eventually lead to ar obust and uniform Li deposition behavior. [19] Since the influence on these three parameters induced by the variation of LiTFSI and OTE could not be decoupled, we designed orthogonal electrolyte recipes with the varied mole S2). Thec omponent ratio is normalized based on 2a).…”

Difluorobenzene‐Based Locally Concentrated Ionic Liquid Electrolyte Enabling Stable Cycling of Lithium Metal Batteries with Nickel‐Rich Cathode

“…The early adopted cosolvents (e.g., carbonate esters), strongly coordinating to Li + and interrupting the Li + -anions solvation, are unstable toward LMAs, leading to unstable SEIs and low lithium plating/stripping CEs. [29,30] In recent years, nonsolvating hydrofluoroethers (HFEs) have been proposed as a new class of cosolvents for ILEs, [29][30][31][32] which is inspired by a similar approach applied to organic-solvent-based concentrated electrolytes. [33][34][35][36][37][38][39] Due to the poor solvation capability of HFEs toward Li + , the ILEs, needing a high Li + concentration to unlock non-vehicular Li + transport, [40,41] are diluted, but with the local Li + coordination preserved.…”

“…This, and HFEs' high compatibility toward LMAs, promote Li + transport in ILEs without compromising the CE of Li stripping/plating. [29][30][31][32] The ILEs diluted with nonsolvating cosolvent are usually named locally concentrated ionic liquid electrolytes (LCILEs).…”

“…The rational design, including the organic cation, [32] anion, [30] and components' concentrations, [29][30][31] of HFE-based LCILEs allows fast charge/discharge (up to 2 mA cm −2 ) and high lithium stripping/plating CE (up to 99%), resulting in ILEs stepping further on their road to practical application. Nonetheless, the cyclability of high-voltage LMBs employing HFE-based LCILEs is still unsatisfactory under the conditions of high cathode mass loadings and/or high current densities, particularly for those employing NMC cathodes.…”

Novel poly(epichlorohydrin)-based matrix for monolithic ionogel electrolyte membrane with high lithium storage performances

“…Owing to high ionic conductivity, excellent electrochemical properties and remarkable thermal stability, ionic liquids (ILs) have been used as the organic plasticizers. 30 ILs not only act as plasticizers but also charge carriers in polymer electrolytes; therefore, the conductivity of GPEs featuring ILs as the plasticizers is much higher than the counterparts using organic solvents as plasticizers. Furthermore, GPEs featuring ILs present good flexibility and compatibility with electrode interfaces.…”