Water-tolerant lithium metal cycling in high lithium concentration phosphonium-based ionic liquid electrolytes

Kerr, Robert; Singh, Nikhilendra; Arthur, Timothy S.; Pathirana, Thushan; Mizuno, Fuminori; Takechi, Kensuke; Forsyth, Maria; Howlett, Patrick C.

doi:10.1039/c8se00159f

Cited by 30 publications

(60 citation statements)

References 33 publications

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“…This suggests that, in the presence of some amount of water, the SEI layer formation mechanism is in effect, creating a different surface chemistry and deposit morphology, which appears to lead to more stable long‐term cycling under these conditions. Similar trends were recently observed for lithium‐metal electrochemistry in superconcentrated LiFSI salts in phosphonium ILs . These measurements indicate the importance of more detailed surface characterization studies to understand the formation mechanism of the SEI in superconcentrated ILs and the effect of water addition, which will then support further design of more stable, water tolerant IL electrolytes.…”

Section: Resultssupporting

confidence: 81%

“…Similart rends were recently observed for lithiummetal electrochemistry in superconcentrated LiFSI salts in phosphonium ILs. [36] These measurements indicate the importance of more detailed surface characterization studies to understand the formation mechanism of the SEI in superconcentrated ILs and the effect of water addition, which will then support furtherd esign of more stable, water tolerant IL electrolytes.…”

Section: Symmetrical Cell Cycling Withconstant Current Density For Lomentioning

confidence: 83%

“…Similarly, for Li metal it was reported that high water content (1 vol %) in a LiTFSI solution in N ‐methyl‐ N ‐propylpiperidinium bis‐(trifluoromethanesulfonyl) imide (PP 13 TFSI) (0.352 mol kg −1 ) showed stable polarization potentials during cycling that resulted from the formation of a stabilizing interlayer in which water was actively involved . Recently, it was shown that if high‐concentration LiFSI salt was used in various ILs, stable Li cell cycling was possible at 1.0 mA cm −2 during 1 h polarization for 250 cycles at room temperature in the presence of approximately 5000 ppm water . The authors concluded that, with some key chemical parameters such as Li + concentration and cation structure, exceptional stability for Li cycling in presence of water was possible.…”

Section: Introductionmentioning

confidence: 99%

“…[35] Recently,i tw as shown that if high-concentration LiFSI salt was used in various ILs, stable Li cell cycling was possible at 1.0 mA cm À2 during 1hpolarization for 250 cycles at room temperature in the presence of approximately 5000ppm water. [36] The authors concluded that, with some key chemical parameters such as Li + concentration and cation structure, exceptional stability for Li cycling in presence of water was possible. More generally,i th as also been shown that the presence of water in non-fluorinated IL electrolytes can improvet he cycling performance in al ithium or sodiummetal battery.…”

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confidence: 99%

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Water as an Effective Additive for High‐Energy‐Density Na Metal Batteries? Studies in a Superconcentrated Ionic Liquid Electrolyte

et al. 2019

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The effect of water on the properties of superconcentrated sodium salt solutions in ionic liquids (ILs) was investigated to design electrolytes for sodium battery applications with water as an additive. Water was added to a 50 mol % solution of NaFSI [FSI=bis(fluorosulfonyl)imide] in the ionic liquid N‐methyl‐N‐propylpyrrolidinium bis(fluorosulfonyl)imide (C3mpyrFSI). Although the thermal properties (e.g., glass transition temperature) showed little dependence on the water content, the viscosity and, in particular, the ionic conductivity were strongly affected. The Na|Na symmetrical cell cycling performance was strongly dependent on the applied current density as well as on the water content. At higher current densities (1.0 mA cm−2) the polarization profiles showed a water dependence, suggesting that water was actively involved in the formation of an improved solid electrolyte interface layer (SEI) for high‐water‐content samples (1000–5000 ppm), resulting in improved long‐term cycling stability. The initial impedance of cells cycled at 1.0 mA cm−2 (measured after 20 cycles) was elevated after water addition, and large polarizations occured for the “wet” samples. However, with further cycling the wet cells began to exhibit lower polarization and improved stability compared to the “dry” sample. The Na|NaFePO4 cell cycling performance was also demonstrated with minimal effect on the cell capacity, further highlighting the negligible activity of water in these electrolyte systems. In fact, reduced cell polarization and a more clearly defined charge profile were evident after water addition. The work shown here suggests that water may be used as a convenient and inexpensive additive for superconcentrated sodium IL electrolytes for improved device performance.

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Section: Resultssupporting

confidence: 81%

Section: Symmetrical Cell Cycling Withconstant Current Density For Lomentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Water as an Effective Additive for High‐Energy‐Density Na Metal Batteries? Studies in a Superconcentrated Ionic Liquid Electrolyte

et al. 2019

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“…[8,9] The potential suitability as electrolyte for lithium batteries has been demonstrated for several phosphonium ionic liquids, with electrochemical windows up to 7 V and high cycling stabilities. [10][11][12] However, a common problem is the viscosity, which is often relatively high compared to molecular solvents. This is especially true for large ions or those which might form extended (hydrogen bond) networks.…”

Section: Introductionmentioning

confidence: 99%

Multiple Ether‐Functionalized Phosphonium Ionic Liquids as Highly Fluid Electrolytes

et al. 2018

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Dedicated to the memory of Reiner Wintringer, our lab technician.Ionic liquids (ILs) are promising electrolytes, although their often high viscosity remains a serious drawback. The latter can be addressed by the introduction of multiple ether functionalization. Based on the highly atom efficient synthesis of tris(2ethoxyethyl) phosphine, several new phosphonium ionic liquids were prepared, which allows studying the influence of the ether side chains. Their most important physicochemical properties have been determined and will be interpreted using established approaches like ionicity, hole theory, and the Walden plot. There is striking evidence that the properties of phosphonium ionic liquids with the methanesulfonate anion are dominated by aggregation, whereas the two triple ether functionalized ILs with the highest fluidity show almost ideal behavior with other factors being dominant. It is furthermore found that the deviation from ideality is not significantly changed upon introduction of the ether side chains, although a very beneficial impact on the fluidity of ILs is observed. Multiple ether functionalization therefore proves as a powerful tool to overcome the disadvantages of phosphonium ionic liquids with large cations.

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Lithium Borate Ester Salts for Electrolyte Application in Next‐Generation High Voltage Lithium Batteries

Roy

Cherepanov

Nguyen

et al. 2021

Advanced Energy Materials

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The atmospheric instability and the corrosive tendency of hexafluorophosphate [PF6]− and fluorosulfonylimide [FSI]− based lithium salts, respectively, are among the major impediments towards their application as electrolytes in high voltage lithium batteries. Herein a new class of Li salts is introduced and their electrochemical behavior is explored. The successful synthesis and characterization are reported, including the crystal structure, of lithium 1,1,1,3,3,3‐(tetrakis)hexafluoroisopropoxy borate (LiBHfip). The oxidative stability of electrolytes of this salt in an ethylene carbonate:dimethyl carbonate mixture (v/v, 50:50) is found to be 5.0 V versus Li+/Li on various working electrodes, showing substantial improvement over a LiPF6 based electrolyte. Moreover, a high stability of an aluminum substrate is observed at potentials up to 5.8 V versus Li+/Li; in comparison, a LiFSI based electrolyte shows prominent signs of Al corrosion above 4.3 V versus Li+/Li. Cells tested with high voltage layered LiNi0.8Mn0.1Co0.1O2 (NMC811) and spinel LiMn2O4 (LMO) cathodes show stable cycling over 200 cycles with capacity retention of 76% and 90%, respectively. The LMO|Li cell maintains this same low capacity fade rate for 1000 cycles even after the salt has been exposed for 24 h to atmospheric conditions (water content ≈0.57 mass%).

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Water-tolerant lithium metal cycling in high lithium concentration phosphonium-based ionic liquid electrolytes

Abstract: Cycling stability at high capacities and water-tolerance are two key properties for the operation of high-capacity lithium (Li) metal–air batteries.

Cited by 30 publications

References 33 publications

Water as an Effective Additive for High‐Energy‐Density Na Metal Batteries? Studies in a Superconcentrated Ionic Liquid Electrolyte

Water as an Effective Additive for High‐Energy‐Density Na Metal Batteries? Studies in a Superconcentrated Ionic Liquid Electrolyte

Multiple Ether‐Functionalized Phosphonium Ionic Liquids as Highly Fluid Electrolytes

Lithium Borate Ester Salts for Electrolyte Application in Next‐Generation High Voltage Lithium Batteries

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