Locally Concentrated Ionic Liquid Electrolytes Enabling Low‐Temperature Lithium Metal Batteries

Abstract

Lithium metal is a promising anode material for next‐generation high‐energy‐density batteries but suffers from low stripping/plating Coulombic efficiency and dendritic growth particularly at sub‐zero temperatures. Herein, a poorly‐flammable, locally concentrated ionic liquid electrolyte with a wide liquidus range extending well below 0 °C is proposed for low‐temperature lithium metal batteries. Its all‐anion Li+ solvation and phase‐nano‐segregation solution structure are sustained at low temperatures, which, together with a solid electrolyte interphase rich in inorganic compounds, enable dendrite‐free operation of lithium metal anodes at −20 °C and 0.5 mA cm−2, with a Coulombic efficiency of 98.9 %. As a result, lithium metal batteries coupling thin lithium metal anodes (4 mAh cm−2) and high‐loading LiNi0.8Co0.15Al0.05O2 cathodes (10 mg cm−2) retain 70 % of the initial capacity after 100 cycles at −20 °C. These results, as a proof of concept, demonstrate the applicability of locally concentrated ionic liquid electrolytes for low‐temperature lithium metal batteries.

Binding FSI− to Construct a Self‐Healing SEI Film for Li‐Metal Batteries by In situ Crosslinking Vinyl Ionic Liquid

“…These results collectively validated the presence of FSI − anions and PEO in both F‐film and V‐film [25] . However, V‐film displayed new XPS peaks at 286.1 and 401.9 eV, which should be related to the C 1s and N 1s regions of C−N bonds derived from the imidazole cations of V‐film [26–28] . Furthermore, the signals of nitrogen and sulfur in FSI − anions showed a small shift in the F‐film spectrum (Figure S6), [29,30] which should be attributed to the strong effect of imidazole cations with anions.…”

Low-temperature electrolytes for electrochemical energy storage devices: bulk and interfacial properties

“…In batteries, occasional strategies involving the use of ILs combined with organic solvents are employed to improve performance. Liu et al [97] into PMMA-IL-TFSI nanospheres. This nanoparticle formed bonds with TFSI anions by a strong electrostatic attraction with the grafted cations, thereby restricting anions and allowing Li + to migrate more freely.…”

Locally Concentrated Ionic Liquid Electrolytes for Wide‐Temperature‐Range Aluminum‐Sulfur Batteries

“…[36,37] Even more recently, this strategy has been extended to concentrated electrolytes based on chemically stable ionic liquids. [38][39][40][41][42][43] Herein, the use of such emerging non-solvating co-solvents to AlCl 3 -EmimCl binary ILEs to construct locally concentrated ionic liquid electrolytes (LCILEs) is explored to address the aforementioned issues. In fact, to the best of our knowledge, LCILEs for aluminum metal batteries have not been reported yet.…”

“…Recently, non‐solvating and relatively inert co‐solvents, e.g., 1,2‐difluorobenzene (dFBn), [30] have been reported allowing to dilute high‐viscosity concentrated electrolytes without affecting the local solvation of Li + , [31–33] Na + , [34] and K + , [35] and forming the so‐called locally concentrated electrolytes [36,37] . Even more recently, this strategy has been extended to concentrated electrolytes based on chemically stable ionic liquids [38–43] . Herein, the use of such emerging non‐solvating co‐solvents to AlCl 3 ‐EmimCl binary ILEs to construct locally concentrated ionic liquid electrolytes (LCILEs) is explored to address the aforementioned issues.…”