High-Efficiency Lithium Metal Batteries with Fire-Retardant Electrolytes

Abstract

Rechargeable lithium metal batteries are regarded as the ''holy grail'' of energy storage systems, but their practical applications have long been hindered by poor cyclability and severe safety concerns. In this work, we report a fire-retardant localized high-concentration electrolyte consisting of 1.2 M lithium bis(fluorosulfonyl)imide in a mixture of flame-retardant triethyl phosphate/bis(2,2,2-trifluoroethyl) ether (1:3 by mol) for 4-V class lithium metal batteries. This electrolyte enables stable, dendrite-free cycling of lithium metal anodes with high Coulombic efficiency of up to 99.2%. Moreover, it exhibits excellent anodic stability even up to 5.0 V and greatly enhances the cycling performance of lithium metal batteries. A LijjLiNi 0.6 Mn 0.2 Co 0.2 O 2 battery using this electrolyte can retain >97% capacity after 600 cycles at 1 C rate (ca. 1.6 mA cm À2 ), corresponding to a negligible capacity decay of <0.005% per cycle. Therefore, this new electrolyte can enable safe operation of high-energy lithium metal batteries for practical applications.

High‐Energy Rechargeable Metallic Lithium Battery at −70 °C Enabled by a Cosolvent Electrolyte

“…[1] To achieve the low-T operation for rechargeable batteries,many efforts have been focused on modifying the electrolyte formulation, such as the utilization of mixed solvents, [2] novel salts and electrolyte additives, [3] and new solvents. [5] However,t he narrower liquid range,lower ionic conductivity and higher viscosity are great challenges for the development of concentrated electrolyte, especially at low-T.Aproper diluent can be applied to lower the viscosity.T he challenge is that it should have little or no impact on the solvation structure of cation-anion aggregates (AGGs), which are responsible for the expanded stable window in the concentrated electrolyte. Unfortunately,an ew challengethe narrow electrochemical window (1.5-4.7 V, vs.L i + /Li)o f the 2mol kg À1 EA-based electrolyte-hinders the application of the Li metal anode for high energy-density batteries.Thus, an ovel electrolyte with enhanced stability to Li-metal is of importance.R esearches show that highly concentrated electrolytes exhibited enhanced oxidative/reductive stability, which offered as olution for an expanded electrochemical stable potential window.…”

“…Unfortunately,an ew challengethe narrow electrochemical window (1.5-4.7 V, vs.L i + /Li)o f the 2mol kg À1 EA-based electrolyte-hinders the application of the Li metal anode for high energy-density batteries.Thus, an ovel electrolyte with enhanced stability to Li-metal is of importance.R esearches show that highly concentrated electrolytes exhibited enhanced oxidative/reductive stability, which offered as olution for an expanded electrochemical stable potential window. [5] However,t he narrower liquid range,lower ionic conductivity and higher viscosity are great challenges for the development of concentrated electrolyte, especially at low-T.Aproper diluent can be applied to lower the viscosity.T he challenge is that it should have little or no impact on the solvation structure of cation-anion aggregates (AGGs), which are responsible for the expanded stable window in the concentrated electrolyte. [6] Moreover,i ti s desirable if the diluent can improve electrolyte conductivity and wettability.D ichloromethane (DCM, CH 2 Cl 2 ), an electrochemically "inert" and poorly solvating solvent, has alow viscosity of 0.44 MPa s, which can meet these requirements.…”

Li-Ion Battery Fire Hazards and Safety Strategies

“…The molar concentration of LiFSA is higher than 3 M. This electrolyte is nonflammable, and has the potential to work as a fire extinguisher to put out the fire on other battery components. However, the high-concentration electrolyte (HCE) has certain disadvantages such as high cost, high viscosity, and poor wettability [39]. Chen et al [39] developed a localized high-concentration electrolyte (LHCE) by diluting the electrolyte (3.2 M LiFSI in TEP) with bis(2,2,2-trifluoroethyl) ether (BTFE).…”

“…However, the high-concentration electrolyte (HCE) has certain disadvantages such as high cost, high viscosity, and poor wettability [39]. Chen et al [39] developed a localized high-concentration electrolyte (LHCE) by diluting the electrolyte (3.2 M LiFSI in TEP) with bis(2,2,2-trifluoroethyl) ether (BTFE). Their test results on lithium batteries proved that the electrochemical performance of the LHCE is better than the HCE.…”

A Selection Rule for Hydrofluoroether Electrolyte Cosolvent: Establishing a Linear Free‐Energy Relationship in Lithium–Sulfur Batteries

“…[8,9] First introduced as an electrolyte cosolvent ad ecade ago, [10] hydrofluoroethers (HFEs) have rapidly been employed by researchers all over the world to construct functional electrolytes for high-voltage lithium-ion, [10][11][12] lithium-metal, [13] lithium-sulfur (Li-S), [14] lithium-air, [15,16] lithium/selenium-sulfur, [17] and even sodium-ion batteries. [13,[23][24][25] Significantly,they have gained popularity in Li-S batteries because of their effectiveness in suppressing the lithium polysulfides (LiPS) shuttle effect. [13,[23][24][25] Significantly,they have gained popularity in Li-S batteries because of their effectiveness in suppressing the lithium polysulfides (LiPS) shuttle effect.…”