Lithium-ion batteries raise safety, environmental, and cost concerns, which mostly arise from their nonaqueous electrolytes. The use of aqueous alternatives is limited by their narrow electrochemical stability window (1.23 volts), which sets an intrinsic limit on the practical voltage and energy output. We report a highly concentrated aqueous electrolyte whose window was expanded to ~3.0 volts with the formation of an electrode-electrolyte interphase. A full lithium-ion battery of 2.3 volts using such an aqueous electrolyte was demonstrated to cycle up to 1000 times, with nearly 100% coulombic efficiency at both low (0.15 coulomb) and high (4.5 coulombs) discharge and charge rates.

Metallic zinc (Zn) has been regarded as an ideal anode material for aqueous batteries because of its high theoretical capacity (820 mA h g), low potential (-0.762 V versus the standard hydrogen electrode), high abundance, low toxicity and intrinsic safety. However, aqueous Zn chemistry persistently suffers from irreversibility issues, as exemplified by its low coulombic efficiency (CE) and dendrite growth during plating/ stripping, and sustained water consumption. In this work, we demonstrate that an aqueous electrolyte based on Zn and lithium salts at high concentrations is a very effective way to address these issues. This unique electrolyte not only enables dendrite-free Zn plating/stripping at nearly 100% CE, but also retains water in the open atmosphere, which makes hermetic cell configurations optional. These merits bring unprecedented flexibility and reversibility to Zn batteries using either LiMnO or O cathodes-the former deliver 180 W h kg while retaining 80% capacity for >4,000 cycles, and the latter deliver 300 W h kg (1,000 W h kg based on the cathode) for >200 cycles.

Lithium metal is an ideal battery anode. However, dendrite growth and limited Coulombic efficiency during cycling have prevented its practical application in rechargeable batteries. Herein, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide salt enables the high-rate cycling of a lithium metal anode at high Coulombic efficiency (up to 99.1%) without dendrite growth. With 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane as the electrolyte, a lithium|lithium cell can be cycled at 10 mA cm−2 for more than 6,000 cycles, and a copper|lithium cell can be cycled at 4 mA cm−2 for more than 1,000 cycles with an average Coulombic efficiency of 98.4%. These excellent performances can be attributed to the increased solvent coordination and increased availability of lithium ion concentration in the electrolyte. Further development of this electrolyte may enable practical applications for lithium metal anode in rechargeable batteries.

Rechargeable Li-metal batteries using high-voltage cathodes can deliver the highest possible energy densities among all electrochemistries. However, the notorious reactivity of metallic lithium as well as the catalytic nature of high-voltage cathode materials largely prevents their practical application. Here, we report a non-flammable fluorinated electrolyte that supports the most aggressive and high-voltage cathodes in a Li-metal battery. Our battery shows high cycling stability, as evidenced by the efficiencies for Li-metal plating/stripping (99.2%) for a 5 V cathode LiCoPO (~99.81%) and a Ni-rich LiNiMnCoO cathode (~99.93%). At a loading of 2.0 mAh cm, our full cells retain ~93% of their original capacities after 1,000 cycles. Surface analyses and quantum chemistry calculations show that stabilization of these aggressive chemistries at extreme potentials is due to the formation of a several-nanometre-thick fluorinated interphase.

A many-body polarizable force field has been developed and validated for ionic liquids (ILs) containing 1-methyl-3-alkylimidazolium, 1-alkyl-2-methyl-3-alkylimidazolium, N-methyl-N-alkylpyrrolidinium, N-alkylpyridinium, N-alkyl-N-alkylpiperidinium, N-alkyl-N-alkylmorpholinium, tetraalkylammonium, tetraalkylphosphonium, N-methyl-N-oligoetherpyrrolidinium cations and BF(4)(-), CF(3)BF(3)(-), CH(3)BF(3)(-), CF(3)SO(3)(-), PF(6)(-), dicyanamide, tricyanomethanide, tetracyanoborate, bis(trifluoromethane sulfonyl)imide (Ntf(2)(-) or TFSI(-)), bis(fluorosulfonyl)imide (FSI(-)) and nitrate anions. Classical molecular dynamics (MD) simulations have been performed on 30 ionic liquids at 298, 333, and 393 K. The IL density, heat of vaporization, ion self-diffusion coefficient, conductivity, and viscosity were found in a good agreement with available experimental data. Ability of the developed force field to predict ionic crystal cell parameters has been tested on four ionic crystals containing Ntf(2)(-) anions. The influence of polarization on the structure and ion transport has been investigated for [emim][BF(4)] IL. A connection between the structural changes in IL resulting from turning off polarization and slowing down of ion dynamics has been found. Developed force field has also provided accurate description/prediction of thermodynamic and transport properties of alkanes, fluoroalkanes, oligoethers (1,2-dimethoxyethane), ethylene carbonate, propylene carbonate, dimethyl carbonate, hydrazine, methyhydrazine, dimethylhydrazine, acetonitrile, dimethyl amine, and dimethyl ketone.