Exploiting the high-energy density of lithium metal as a negative electrode for lithium batteries is considered a prerequisite to satisfy the continually increasing demand for extended driving range of electric vehicles and fully electrify our mobility and transportation. However, such lithium-metal batteries face critical safety and life-span concerns. This work outlines a clear route toward realizing safe high-energy-density lithium-metal batteries with excellent cycling stability through the use of a non-flammable and low-volatile ionic liquid electrolyte.

For the development of advanced flexible and wearable electronic devices, functional electrolytes with excellent conductivity, temperature tolerance, and desirable mechanical properties need to be engineered. Herein, an alkaline doublenetwork hydrogel with high conductivity and superior mechanical and antifreezing properties is designed and promisingly utilized as the flexible electrolyte in all-solid-state zinc−air batteries. The conductive hydrogel is comprised of covalently cross-linked polyelectrolyte poly(2-acrylamido-2-methylpropanesulfonic acid potassium salt) (PAMPS-K) and interpenetrating methyl cellulose (MC) in the presence of concentrated alkaline solutions. The covalently cross-linked PAMPS-K skeleton and interpenetrating MC chains endow the hydrogel with good mechanical strength, toughness, an extremely rapid self-recovery capability, and an outstanding antifatigue property. Gratifyingly, the entrapment of a concentrated alkaline solution in the hydrogel matrix yields an extremely high ionic conductivity (105 mS cm −1 at 25 °C) and an excellent antifreezing capacity. The hydrogel retains comparable conductivity and eligible strength to withstand various mechanical deformations at −20 °C. The all-solid-state zinc−air batteries using PAMPS-K/MC hydrogels as flexible alkaline electrolytes exhibit comparable values of specific capacity (764.7 mAh g −1 ), energy capacity (850.2 mWh g −1 ), cycling stability, and mechanical flexibility. The batteries still possess competitive electrochemical performances even when the operating temperature drops to −20 °C.

Vanadium oxides have been recognized to be among the most promising positive electrode materials for aqueous zinc metal batteries (AZMBs). However, their underlying intercalation mechanisms are still vigorously debated. To shed light on the intercalation mechanisms, high-performance δ-V 2 O 5 is investigated as a model compound. Its structural and electrochemical behaviors in the designed cells with three different electrolytes, i.e., 3 m Zn(CF 3 SO 3 ) 2 /water, 0.01 M H 2 SO 4 /water, and 1 M Zn(CF 3 SO 3 ) 2 /acetonitrile, demonstrate that the conventional structural and elemental characterization methods cannot adequately clarify the separate roles of H + and Zn 2+ intercalations in the Zn(CF 3 SO 3 ) 2 /water electrolyte. Thus, an operando pH determination method is developed and used toward Zn/δ-V 2 O 5 AZMBs. This method indicates the intercalation of both H + and Zn 2+ into δ-V 2 O 5 and uncovers an unusual H + /Zn 2+ -exchange intercalation–deintercalation mechanism. Density functional theory calculations further reveal that the H + /Zn 2+ intercalation chemistry is a consequence of the variation of the electrochemical potential of Zn 2+ and H + during the electrochemical intercalation/release.

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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

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Ionic liquids (ILs) have been widely explored as alternative electrolytes to combat the safety issues associated with conventional organic electrolytes. However, hindered by their relatively high viscosity, the electrochemical performances of IL‐based cells are generally assessed at medium‐to‐high temperature and limited cycling rate. A suitable combination of alkoxy‐functionalized cations with asymmetric imide anions can effectively lower the lattice energy and improve the fluidity of the IL material. The Li/Li1.2Ni0.2Mn0.6O2 cell employing N‐N‐diethyl‐N‐methyl‐N‐(2‐methoxyethyl)ammonium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (DEMEFTFSI)‐based electrolyte delivered an initial capacity of 153 mAh g−1 within the voltage range of 2.5–4.6 V, with a capacity retention of 65.5 % after 500 cycles and stable coulombic efficiencies exceeding 99.5 %. Moreover, preliminary battery tests demonstrated that the drawbacks in terms of rate capability could be improved by using Li‐concentrated IL‐based electrolytes. The improved room‐temperature rate performance of these electrolytes was likely owing to the formation of Li+‐containing aggregate species, changing the concentration‐dependent Li‐ion transport mechanism.

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