Effect of Charge Transfer Resistance on Morphology of Lithium Electrodeposited in Ionic Liquid (original) (raw)
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Journal of The Electrochemical Society, 2014
The morphology of electrodeposited lithium in room-temperature ionic liquids was investigated by ex situ SEM observations, and the dependence of the distribution of the electrodeposited lithium nuclei on current density was discussed with respect to the lithium-ion diffusion coefficient. It was concluded that the deposits are better distributed with a decreased size when the current density is increased in the current range where the deposition is charge-transfer controlled. Under a larger current density at which the deposition is diffusion controlled, larger dendritic deposits are observed, although deposits are well distributed over a large area. Under so large current density that the diffusion of lithium ions is slower than the lithium ion reduction, the electrode potential becomes highly negative. Abovementioned tendency is very common for the electrodeposition of noble metals from an aqueous solution, but it was firstly presented for lithium metal. It is probably due to very low reactivity of the ionic liquid used with lithium in this study.
Ionic liquids as electrolytes for Li-ion batteries--An overview of electrochemical studies
Journal of Power Sources, 2009
The paper reviews properties of room temperature ionic liquids (RTILs) as electrolytes for lithium and lithium-ion batteries. It has been shown that the formation of the solid electrolyte interface (SEI) on the anode surface is critical to the correct operation of secondary lithium-ion batteries, including those working with ionic liquids as electrolytes. The SEI layer may be formed by electrochemical transformation of (i) a molecular additive, (ii) RTIL cations or (iii) RTIL anions. Such properties of RTIL electrolytes as viscosity, conductivity, vapour pressure and lithium-ion transport numbers are also discussed from the point of view of their influence on battery performance.
Structure−Properties Relationships of Lithium Electrolytes Based on Ionic Liquid
The Journal of Physical Chemistry B, 2010
and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs, including melting point, glass transition, and degradation temperatures; viscosity; density; ionic conductivity; diffusion coefficient; and electrochemical stability, were determined. Heteronuclear Overhauser NMR spectroscopy experiments were also performed to point out the presence of pair correlation between the different moieties. The LiTFSI addition effect on the IL properties was studied with the same methodology. Some nanoscale organization with segregation of polar and apolar domains was observed. ILs with small alkyl chain length or fluorinated ammonium exhibit very high electrochemical stability in oxidation.
Development of ionic liquid-based lithium battery prototypes
Journal of Power Sources, 2012
The lab-scale manufacturing of Li/LiFePO 4 and Li 4 Ti 5 O 12 /LiFePO 4 stacked battery prototypes and their performance characterization are described here. The prototypes were realized in the frame of an European Project devoted to the development of greener and safer lithium batteries, based on ionic liquid electrolytes, for integration with photovoltaic panels. N-Butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR 14 TFSI) and N-butyl-N-methylpyrrolidinium bis(fluoromethanesulfonyl)imide (PYR 14 FSI), selected as the ionic liquids (ILs), were used to formulate the poly(ethylene oxide)-LiN(SO 2 CF 3 ) 2 -PYR 14 TFSI (PEO-LiTFSI-PYR 14 TFSI) polymer electrolyte and the LiTFSI-PYR 14 FSI liquid electrolyte, which were employed to produce lithium metal and lithium-ion prototypes, respectively. The composite electrodes for the lithium metal and lithium-ion prototypes were prepared through, respectively, a solvent-free and a water-based procedure route. The performance of the lithium battery prototypes was evaluated in terms of specific capacity, energy, cycle life and coulombic efficiency at different current densities. The results have indicated high reproducibility and the feasibility of scaling-up solvent-free, lithium batteries based on ionic liquids for low and mid rate applications such as renewable energy storage.
Ionic liquids and their derivatives for lithium batteries: role, design strategy, and perspectives
Energy Materials, 2023
Lithium-ion batteries (LIBs) are the predominant power source for portable electronic devices, and in recent years, their use has extended to higher-energy and larger devices. However, to satisfy the stringent requirements of safety and energy density, further material advancements are required. Due to the inherent flammability and incompatibility of organic solvent-based liquid electrolytes with materials utilized in high energy devices, it is necessary to transition to alternative conductive mediums. The focus is shifting from molecular materials to a class of materials based on ions, including ionic liquids (ILs) and their derivatives such as zwitterionic ILs, polymerized ILs, and solvated ILs, which possess high levels of safety, stability, compatibility, and the ability to rationally design ILs for specific applications. Ion design is crucial to achieve superior control of electrode/electrolyte interphases (EEIs) both on anode and cathode surfaces to realize safer and higher-energy lithium-metal batteries (LMBs). This review summarizes the different uses of ILs in electrolytes (both liquid and solids) for LMBs, reporting the most promising results obtained during the last years and highlighting their role in the formation of suitable EEIs. Furthermore, a discussion on the use of deep-eutectic solvents is also provided, which is a class of material with similar properties to ILs and an important alternative from the viewpoint of sustainability. Lastly, future prospects for the optimization of IL-based electrolytes are summarized, ranging from the functional design of ionic structures to the realization of nanophases with specific features.
Homogeneous Lithium Electrodeposition with Pyrrolidinium-Based Ionic Liquid Electrolytes
ACS Applied Materials & Interfaces, 2015
In this study, we report on the electroplating and stripping of lithium in two ionic liquid (IL) based electrolytes, namely N-butyl-N-methylpyrrolidinium bis-(fluorosulfonyl) imide (Pyr 14 FSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr 14 TFSI), and mixtures thereof, both on nickel and lithium electrodes. An improved method to evaluate the Li cycling efficiency confirmed that homogeneous electroplating (and stripping) of Li is possible with TFSI-based ILs. Moreover, the presence of native surface features on lithium, directly observable via scanning electron microscope imaging, was used to demonstrate the enhanced electrolyte interphase (SEI)-forming ability, that is, fast cathodic reactivity of this class of electrolytes and the suppressed dendrite growth. Finally, the induced inhomogeneous deposition enabled us to witness the SEI cracking and revealed previously unreported bundled Li fibers below the pre-existing SEI and nonrod-shaped protuberances resulting from Li extrusion.
Lithium-Ion-Conducting Electrolytes: From an Ionic Liquid to the Polymer Membrane
Journal of the Electrochemical Society, 2009
This work concerns the design, the synthesis, and the characterization of the N-butyl-Nethylpiperidinium N,N-bis(trifluoromethane)sulfonimide (PP 24 TFSI) ionic liquid (IL). To impart Liion transport, a suitable amount of lithium N,N-bis-(trifluoromethane)sulfonimide (LiTFSI) is added to the IL. The Li-IL mixture displays ionic conductivity values on the order of 10 −4 S cm −1 and an electrochemical stability window in the range of 1.8-4.5 V vs Li + /Li. The voltammetric analysis demonstrates that the cathodic decomposition gives rise to a passivating layer on the surface of the working electrode, which kinetically extends the stability of the Li/IL interface as confirmed by electrochemical impedance spectroscopy measurements. The LiTFSI-PP 24 TFSI mixture is incorporated in a poly(vinylidene fluoride-co-hexafluoropropylene) matrix to form various electrolyte membranes with different LiTFSI-PP 24 TFSI contents. The ionic conductivity of all the membranes resembles that of the LiTFSI-IL mixture, suggesting an ionic transport mechanism similar to that of the liquid component. NMR measurements demonstrate a reduction in the mobility of all ions following the addition of LiTFSI to the PP 24 TFSI IL and when incorporating the mixture into the membrane. Finally, an unexpected but potentially significant enhancement in Li transference number is observed in passing from the liquid to the membrane electrolyte system. The growing large-scale production of batteries all over the world is mainly due to the increasing demand for energy-storage and portable devices. Focusing on the purpose of achieving maintenance-free, high energy density battery systems, the lithium secondary batteries have become the most attractive candidates. 1 With respect to the state-of-the-art of such devices, however, further improvements are required, especially in terms of cycling performances and safety. The presence of a highly reactive Li metal as the anode material requires the use of very stable electrolyte solvents. Moreover, the volatility of such solvents is a serious drawback when considering the scaling-up of the battery systems, and the presence of liquids requires special battery pack sealing to prevent leakage. To circumvent safety concerns, research has pursued the implementation of advanced electrolyte solvents. From this viewpoint, ionic liquids (ILs), which are nonvolatile, nonflammable molten salts with high ionic conductivity, 2, 3 are very promising candidates.
Ionic Liquid Electrolytes for Safer Lithium Batteries
Journal of The Electrochemical Society
In this paper we report on the investigation of ionic liquid-based electrolytes with enhanced characteristics. In particular, we have studied ternary mixtures based on the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt and two ionic liquids sharing the same cation (N-methyl-N-propyl pyrrolidinium, PYR 13), but different anions, bis(trifluoromethanesulfonyl)imide (TFSI) and bis(fluorosulfonyl)imide (FSI). The LiTFSI-PYR 13 TFSI-PYR 13 FSI mixtures, found to be ionically dissociated, exhibit better ion transport properties (about 10 −3 S cm −1 at −20 • C) with respect to similar ionic liquid electrolytes till reported in literature. An electrochemical stability window of 5 V is observed in carbon working electrodes. Preliminary battery tests confirm the good performance of these ternary electrolytes with high-voltage NMC cathodes and graphite anodes. Ionic liquid electrolyte mixtures, PYR 13 TFSI, PYR 13 FSI.
Ionic liquid electrolytes for Li-air batteries: lithium metal cycling
International journal of molecular sciences, 2014
In this work, the electrochemical stability and lithium plating/stripping performance of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) are reported, by investigating the behavior of Li metal electrodes in symmetrical Li/electrolyte/Li cells. Electrochemical impedance spectroscopy measurements and galvanostatic cycling at different temperatures are performed to analyze the influence of temperature on the stabilization of the solid electrolyte interphase (SEI), showing that TFSI-based ionic liquids (ILs) rank among the best candidates for long-lasting Li-air cells.