Thermally-responsive, nonflammable phosphonium ionic liquid electrolytes for lithium metal batteries: operating at 100 degrees celsius

Lin, Xinrong; Kavian, Reza; Lu, Yi‐Chun; Hu, Qichao; Shao‐Horn, Yang; Grinstaff, Mark W.

doi:10.1039/c5sc01518a

Cited by 41 publications

(21 citation statements)

References 59 publications

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“…al have shown that a hydrophobic phosphonium-based IL electrolyte could operate a Li|LiCoO 2 metal battery at elevated temperature (100 °C). 26 The authors also found that an increase in the Li salt concentration (up to 1.6 M Li salt in the IL) led to a higher capacity retention (90%) than that obtained with lower salt concentrations. One of our recent studies revealed that trimethyl(isobutyl)phosphonium FSI IL (P 111i4 FSI) readily dissolved high amounts of LiFSI salt and the highly concentrated electrolyte (3.8 mol•kg −1 , i.e., a 1:1.2 molar ratio of IL/salt) supported reversible and efficient Li cycling even at switching potentials as negative as −1.1 V versus Li/Li + , indicating high electrolyte stability for Li batteries.…”

Section: Introductionmentioning

confidence: 91%

“…This study revealed that a highly concentrated IL electrolyte can, in principle, outperform an organic liquid electrolyte (1 M LiPF 6 in EC:DMC). More recently, novel phosphonium-based ILs have demonstrated superior transport properties compared to their ammonium-based counterparts. − Lin et. al have shown that a hydrophobic phosphonium-based IL electrolyte could operate a Li|LiCoO 2 metal battery at elevated temperature (100 °C) .…”

Section: Introductionmentioning

confidence: 99%

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Role of Li Concentration and the SEI Layer in Enabling High Performance Li Metal Electrodes Using a Phosphonium Bis(fluorosulfonyl)imide Ionic Liquid

et al. 2017

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In this study the performance of the lithium (Li) anode is characterized in two alternative ionic liquid electrolytes: (i) a solution of 0.5 mol·kg–1 of lithium bis(fluorosulfonyl)imide (LiFSI) in trimethyl(isobutyl)phosphonium FSI (P111i4FSI) and (ii) an equimolar mixture of these two salts, effectively an inorganic–organic mixture IL. We have investigated the formation of the solid electrolyte interphase (SEI) at the lithium electrode and its influence on the polarization potential, the electrode surface impedance and deposition morphologies. Lithium metal cycling is revealed to be significantly more stable in the electrolyte with high lithium salt concentration due to the creation of a more uniform SEI. Stable and effective cycling was demonstrated at high applied currents (up to 12 mA·cm–2) with large areal capacities being transferred with each polarization cycle (up to 6 mAh·cm–2 at 50 °C). An average Coulombic efficiency of not less than 99.2% was demonstrated under these conditions and SEM observations of the cycled electrode surfaces show a uniform and compact deposit. Combined with spectroscopic characterization of the electrolyte and electrode surface, these observations indicate a role for the speciation and transport properties of these high concentration ionic liquid electrolytes in modifiying the physicochemical properties of the SEI which result in enhanced cycling performance of the Li metal electrode.

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Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Role of Li Concentration and the SEI Layer in Enabling High Performance Li Metal Electrodes Using a Phosphonium Bis(fluorosulfonyl)imide Ionic Liquid

et al. 2017

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“…Moving to all-solid-state brings significant advantages, among which their increased thermal stability and high energy density stand out. It is widely recognized that solid state batteries provide a wide thermal operation window of more than 400ºC, superior to liquid/polymer based electrolytes that are often restricted to 120°C as a maximum during operation [3][4][5] . The improved thermochemical stability gives opportunity to employ alternative high voltage electrode materials, which are often instable towards standard liquid-based Li-battery electrolytes but provide higher capacity (see review by Dudney group [6] ).…”

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confidence: 99%

Glass‐Type Polyamorphism in Li‐Garnet Thin Film Solid State Battery Conductors

Garbayo

Struzik

Bowman

et al. 2018

Advanced Energy Materials

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Ceramic Li7La3Zr2O12 garnet materials are promising candidates for the electrolytes in solid state batteries due to their high conductivity and structural stability. In this paper, the existence of “polyamorphism” leading to various glass‐type phases for Li‐garnet structure besides the known crystalline ceramic ones is demonstrated. A maximum in Li‐conductivity exists depending on a frozen thermodynamic glass state, as exemplified for thin film processing, for which the local near range order and bonding unit arrangement differ. Through processing temperature change, the crystallization and evolution through various amorphous and biphasic amorphous/crystalline phase states can be followed for constant Li‐total concentration up to fully crystalline nanostructures. These findings reveal that glass‐type thin film Li‐garnet conductors exist for which polyamorphism can be used to tune the Li‐conductivity being potential new solid state electrolyte phases to avoid Li‐dendrite formation (no grain boundaries) for future microbatteries and large‐scale solid state batteries.

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“…15,16 Replacing conventional electrolytes with ionic liquids is one solution that addresses the inherent safety issues in current Li-ion batteries, and could enable high temperature applications. [17][18][19][20][21][22][23][24][25][26][27] To illustrate the general synthetic and material processing methods utilized to construct lithium ion batteries containing ionic liquids for high temperature applications, we describe the synthesis, thermal properties, and electrochemical characterization of mono-and di-phosphonium ionic liquids paired with either the chloride (Cl) or bis(trifluoromethane)sulfonimide (TFSI) anion. Different concentrations of lithium bis(trifluoromethane)sulfonimide (LiTFSI) are subsequently added to the phosphonium ionic liquids to give electrolytes.…”

Section: 11mentioning

confidence: 99%

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

Lin

Varela

Grinstaff

2016

JoVE

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The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion batteries for use in devices operating at elevated temperatures require thermally stable and non-flammable electrolytes. Ionic liquids (ILs), which are non-flammable, non-volatile, thermally stable molten salts, are an ideal replacement for flammable and low boiling point organic solvent electrolytes currently used today. We herein describe the procedures to: 1) synthesize mono- and di-phosphonium ionic liquids paired with chloride or bis(trifluoromethane)sulfonimide (TFSI) anions; 2) measure the thermal properties and stability of these ionic liquids by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA); 3) measure the electrochemical properties of the ionic liquids by cyclic voltammetry (CV); 4) prepare electrolytes containing lithium bis(trifluoromethane)sulfonamide; 5) measure the conductivity of the electrolytes as a function of temperature; 6) assemble a coin cell battery with two of the electrolytes along with a Li metal anode and LiCoO2 cathode; and 7) evaluate battery performance at 100 °C. We additionally describe the challenges in execution as well as the insights gained from performing these experiments.

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Thermally-responsive, nonflammable phosphonium ionic liquid electrolytes for lithium metal batteries: operating at 100 degrees celsius

Abstract: Lithium metal battery cycling at 100 °C is enabled by thermally-responsive, nonflammable phosphonium ionic liquid electrolytes.

Cited by 41 publications

References 59 publications

Role of Li Concentration and the SEI Layer in Enabling High Performance Li Metal Electrodes Using a Phosphonium Bis(fluorosulfonyl)imide Ionic Liquid

Role of Li Concentration and the SEI Layer in Enabling High Performance Li Metal Electrodes Using a Phosphonium Bis(fluorosulfonyl)imide Ionic Liquid

Glass‐Type Polyamorphism in Li‐Garnet Thin Film Solid State Battery Conductors

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

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