Ionic liquid based lithium battery electrolytes: fundamental benefits of utilising both TFSI and FSI anions?

Kerner, Martin; Plylahan, Nareerat; Scheers, Johan; Johansson, Patrik

doi:10.1039/c5cp01891a

Cited by 180 publications

(133 citation statements)

References 84 publications

(257 reference statements)

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“…We, however, did not see any reduction in Td with respect to the lithium salt content increase for set A, while in fact a minor improvement was observed for set B. This increased thermal stability is most likely due to the lithium salt itself having a higher Td [8] than poly((DDA)(FSI))/Pyr14FSI. These higher thermal stabilities are rather kinetic effects than inherently thermodynamic, why we performed isothermal TGA for more precise determinations of the PILel thermal stabilities, resulting in no mass loss for set A at 125 °C, but mass losses between 6.5 and 9.5 wt% were seen for set B, hence, not truly stable at this temperature.…”

Section: Thermal Stabilitymentioning

confidence: 55%

“…Overall, the ionic conductivities are lower compared to set A and only B 6:1 and 3:1 reach 1 mS/cm at 100 • C and 80 • C, respectively. This indicates a higher mobility of the Li + (or indeed other ions) in set A, possibly originating in the FSI anions of set B predominantly creating large complexes of three FSI solvating Li + , rather than two TFSI solvating Li + in set A, as previously found for ILs with exclusively FSI or TFSI present [8]. Another possibility/speculation is that the size of the FSI anion affects more macroscopic material properties.…”

Section: Ionic Conductivitiesmentioning

confidence: 64%

“…180 °C earlier than for set A at 350 °C (Figure 3a). This difference in thermal stability between FSI and TFSI based systems has previously been observed for EMI cation based ILel [8], possibly related to a lower thermal stability of the FSI anion when lithium ions are present. The Td of set A at ca.…”

Section: Thermal Stabilitymentioning

confidence: 84%

“…Both sets show higher current densities for higher concentrations of LiTFSI, and as the current produced is proportional to the amount of reduced material, this strongly points to TFSI reduction. Altogether, the decreased electrochemical stability of set A stands in contrast to IL based electrolytes, where TFSI based ILel are more stable than FSI based ILel [8]. The evolution of the interfacial resistance at 80 °C as a function of time was investigated by EIS and found to increase during the first 40 hours and then stabilize (Figure 6a).…”

Section: Electrochemical Studiesmentioning

confidence: 99%

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Pyrrolidinium FSI and TFSI-Based Polymerized Ionic Liquids as Electrolytes for High-Temperature Lithium-Ion Batteries

Kerner

Johansson

2018

Batteries

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Promising electrochemical and dynamical properties, as well as high thermal stability, have been the driving forces behind application of ionic liquids (ILs) and polymerized ionic liquids (PILs) as electrolytes for high-temperature lithium-ion batteries (HT-LIBs). Here, several ternary lithium-salt/IL/PIL electrolytes (PIL el ) have been investigated for synergies of having both FSI and TFSI anions present, primarily in terms of physico-chemical properties, for unique application in HT-LIBs operating at 80 • C. All of the electrolytes tested have low T g and are thermally stable ≥100 • C, and with TFSI as the exclusive anion the electrolytes (set A) have higher thermal stabilities ≥125 • C. Ionic conductivities are in the range of 1 mS/cm at 100 • C and slightly higher for set A PIL el , which, however, have lower oxidation stabilities than set B PIL el with both FSI and TFSI anions present: 3.4-3.7 V vs. 4.2 V. The evolution of the interfacial resistance increases for all PIL el during the first 40 h, but are much lower for set B PIL el and generally decrease with increasing Li-salt content. The higher interfacial resistances only influence the cycling performance at high C-rates (1 C), where set B PIL el with high Li-salt content performs better, while the discharge capacities at the 0.1 C rate are comparable. Long-term cycling at 0.5 C, however, shows stable discharge capacities for 100 cycles, with the exception of the set B PIL el with high Li-salt content. Altogether, the presence of both FSI and TFSI anions in the PIL el results in lower ionic conductivities and decreased thermal stabilities, but also higher oxidation stabilities and reduced interfacial resistances and, in total, result in an improved rate capability, but compromised long-term capacity retention. Overall, these electrolytes open for novel designs of HT-LIBs.

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Section: Thermal Stabilitymentioning

confidence: 55%

Section: Ionic Conductivitiesmentioning

confidence: 64%

Section: Thermal Stabilitymentioning

confidence: 84%

Section: Electrochemical Studiesmentioning

confidence: 99%

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Pyrrolidinium FSI and TFSI-Based Polymerized Ionic Liquids as Electrolytes for High-Temperature Lithium-Ion Batteries

Kerner

Johansson

2018

Batteries

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“…LiFSI and LiTFSI have received increasing attention as alternative Li salts for LIBs due to their higher chemical and thermal stability relative to LiPF 6 28. Of note, impurities and residual moistures in LiFSI affect its thermal stability.…”

Section: Discussionmentioning

confidence: 99%

Research Progress towards Understanding the Unique Interfaces between Concentrated Electrolytes and Electrodes for Energy Storage Applications

et al. 2017

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The electrolyte is an indispensable component in all electrochemical energy storage and conversion devices with batteries being a prime example. While most research efforts have been pursued on the materials side, the progress for the electrolyte is slow due to the decomposition of salts and solvents at low potentials, not to mention their complicated interactions with the electrode materials. The general properties of bulk electrolytes such as ionic conductivity, viscosity, and stability all affect the cell performance. However, for a specific electrochemical cell in which the cathode, anode, and electrolyte are optimized, it is the interface between the solid electrode and the liquid electrolyte, generally referred to as the solid electrolyte interphase (SEI), that dictates the rate of ion flow in the system. The commonly used electrolyte is within the range of 1–1.2 m based on the prior optimization experience, leaving the high concentration region insufficiently recognized. Recently, electrolytes with increased concentration (>1.0 m) have received intensive attention due to quite a few interesting discoveries in cells containing concentrated electrolytes. The formation mechanism and the nature of the SEI layers derived from concentrated electrolytes could be fundamentally distinct from those of the traditional SEI and thus enable unusual functions that cannot be realized using regular electrolytes. In this article, we provide an overview on the recent progress of high concentration electrolytes in different battery chemistries. The experimentally observed phenomena and their underlying fundamental mechanisms are discussed. New insights and perspectives are proposed to inspire more revolutionary solutions to address the interfacial challenges.

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Ionic Liquid and Polymer‐Based Electrolytes for Sodium Battery Applications

Forsyth¹,

Makhlooghiazad²,

Chen³

et al. 2022

Sodium‐Ion Batteries

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Ionic liquid based lithium battery electrolytes: fundamental benefits of utilising both TFSI and FSI anions?

Cited by 180 publications

References 84 publications

Pyrrolidinium FSI and TFSI-Based Polymerized Ionic Liquids as Electrolytes for High-Temperature Lithium-Ion Batteries

Pyrrolidinium FSI and TFSI-Based Polymerized Ionic Liquids as Electrolytes for High-Temperature Lithium-Ion Batteries

Research Progress towards Understanding the Unique Interfaces between Concentrated Electrolytes and Electrodes for Energy Storage Applications

Ionic Liquid and Polymer‐Based Electrolytes for Sodium Battery Applications

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