New, ionic liquid-based membranes for lithium battery application (original) (raw)
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Ionic Liquid Based Polymer Gel Electrolyte Membranes for Lithium Ion Rechargeable Batteries
Li-ion conducting polymeric membranes containing 1-butyl-3-methylimidazolium tetrafluroborate (BMIMBF 4) , polymer poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), and Lithium bis(trifluoromethanesulfonyl)imide) (LiTFSI) salt have been synthesized and characterized by various techniques. The synthesized polymeric membrane have good free-standing characteristics, good thermal stability (300-400 o C) and also have a wide electrochemical window (ECW) ~ 4.0 to 4.50V. The room temperature ionic conductivity of the membrane (PVdF-HFP+20 wt.% LiTFSI) + 60%
Ionic Liquid-Based Electrolyte Membranes for Medium-High Temperatures Lithium Polymer Batteries
2018
Li+-conducting polyethylene oxide-based membranes, incorporating the N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, are as electrolyte separators for all-solid-state lithium polymer batteries operating at medium-high temperatures. The incorporation of the ionic liquid remarkably improves the thermal, ion-transport and interfacial properties of the polymer electrolyte, which, in combination with the wide electrochemical stability even at medium-high temperatures, allow high current rates without any appreciable lithium anode degradation. Battery tests carried out at 80 °C have shown excellent cycling performance and capacity retention even at high rates, never tackled by ionic liquid-free polymer electrolytes. No dendrite growth onto the lithium metal anode was observed.
Australian Journal of Chemistry, 2013
In batteries the separator plays a crucial role within the cell. Commercially available separators, e.g. polyolefins, glass fibres, or polyolefins with ceramic coatings, do not have ideal compatibility with ionic liquid (IL) electrolytes. In this study, we report on the use of electrospinning to fabricate poly(vinylidene fluoride) (PVDF) membranes for use with IL electrolyte based batteries. Four electrospun membranes have been prepared; a neat PVDF, PVDF doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and two LiTFSI-doped membranes based on either thermal or UV crosslinking. The membranes were characterised by a number of techniques and the key characteristics of all electrospun membranes included small fibre sizes and high porosity. The tensile strengths of the cross-linked membranes approached those of commercial membranes. Electrochemical performance was measured using coin cell cycling and the thermally cross-linked membrane gave the lowest cell overpotential as well as the lowest cell resistance.
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 TFSI͒ ionic liquid ͑IL͒. To impart Li-ion transport, a suitable amount of lithium N,N-bis-͑trifluoromethane͒sulfonimide ͑LiTFSI͒ 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 poly͑vinylidene fluoride-co-hexafluoropropylene͒ 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.
PVdF-HFP and Ionic-Liquid-Based, Freestanding Thin Separator for Lithium-Ion Batteries
ACS Applied Energy Materials, 2018
Lithium-ion batteries are the key for modern electricity-based transportation systems and more generally for sustainable large scale energy applications. However, typical commercial batteries seldom meet the safety regulations due to the presence of organic, flammable and volatile liquid electrolytes, and viable alternatives need to be found. Ionic liquids (IL) are considered to be one of the most promising candidates, when combined with a polymer matrix to form the so-called gel polymer electrolyte, working as separator. Along this line, a new, purely water-based methodology has been developed in this work to produce thin separators. This involves the formation of fractal polymer clusters (PCs) through intense sheardriven gelation of PVdF-HFP nanoparticles in water, impregnation of the IL (Pyr13TFSI-LiTFSI) solution into the dried PCs, and hot-pressing to form continuous, porous, and transparent membranes. Due to the large amount of pores generated in the fractal structures with well-defined pore dimensions, the impregnated IL solution forms a continuous phase in the PC-IL matrix without any dead volume, thus forming a bicontinuous structure and presenting good ionic conductivity. The formed membrane has been used as the separator to assemble a half-coin cell having LiFePO 4 and Li as the cathode and the counter electrode, respectively, which is
High-performance gel-type lithium electrolyte membranes
Electrochemistry Communications, 1999
Battery-grade solution products have been used for the synthesis of new types of poly(acrylonitrile) PAN-based polymer electrolyte membranes. Basically, two classes of membranes have been prepared differing by the type of lithium salt in the ethylene carbonate-dimethyl carbonate (EC-DMC) solution trapped in the PAN matrix, i.e. LiPF 6 or LiC(CF 3 SO 2 ) 3 lithium methide salt, respectively. The results demonstrate that both classes of membranes have high conductivity and very good chemical and electrochemical stability. These unique characteristics make the membranes suitable for applications in high-voltage, rechargeable lithium batteries.
Electrochimica Acta, 2014
Ionic liquid gel polymer electrolyte (IL-GPE) was prepared in situ by photocuring of a mixture containing N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (IL), lithium bis(trifluoromethanesulphonyl)imide and ethoxylated bisphenol A diacrylate. The obtained IL-GPE was characterized by differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), cyclic and linear sweep voltammetry (CV and LSV) and galvanostatic charging/discharging. Ionic conductivity of the IL-GPE reached 0.64·10 −4 S cm −1 at 25 • C and increased with a rise in temperature to 4.8 10 −3 S cm −1 at 95 • C. Electrochemical stability of the IL-GPE is ca. 4.8 V vs. Li/Li + . The assembled cell consisting of the Li/IL-GPE/LiFePO 4 exhibited stable cycle properties and high capacity above 162 mAh g −1 after 50 cycles (96% of theoretical capacity, which for LiFePO 4 is 170 mAh g −1 ) at the C/20 rate and 25 • C. The results obtained indicate that the new IL-GPE is a promising candidate as an electrolyte for flexible lithium ion batteries.
Li Ion Conducting Polymer Gel Electrolytes Based on Ionic Liquid/PVDF-HFP Blends
Journal of The Electrochemical Society, 2007
Ionic liquids thermodynamically compatible with Li metal are very promising for applications to rechargeable lithium batteries. 1-methyl-3-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P 13 TFSI) is screened out as a particularly promising ionic liquid in this study. Dimensionally stable, elastic, flexible, nonvolatile polymer gel electrolytes (PGEs) with high electrochemical stabilities, high ionic conductivities and other desirable properties have been synthesized by dissolving Li imide salt (LiTFSI) in P 13 TFSI ionic liquid and then mixing the electrolyte solution with poly(vinylideneco-hexafluoropropylene) (PVDF-HFP) copolymer. Adding small amounts of ethylene carbonate to the polymer gel electrolytes dramatically improves the ionic conductivity, net Li ion transport concentration, and Li ion transport kinetics of these electrolytes. They are thus favorable and offer good prospects in the application to rechargeable Li batteries including open systems like Li/air batteries, as well as more "conventional" rechargeable lithium and lithium ion batteries. As is well known, Li is the most electropositive and lightest metal, and thus has the greatest theoretical specific capacity of 3860 Ah/kg.1 , 2 This has attracted worldwide efforts of researchers and manufacturers to develop advanced battery technologies based on lithium. To date, the rechargeable lithium ion battery has already been one of the best choices in view of specific capacity and cycle stability. 1 However, rechargeable lithium metal batteries with even higher specific capacities are still unavailable in the market, especially lithium/air batteries which possess the highest theoretical specific energy (as high as 13,000 Wh/g, excluding the oxygen from the air). Conventional Li/air batteries based on aqueous electrolytes suffer from fast capacity loss due to corrosion of lithium by water and are also nonrechargeable. Abraham and Jiang first reported a rechargeable lithium/oxygen cell using organic polymer gel electrolytes and demonstrated its advantages such as an all solid state design, rechargeablity and a high capacity. 3 Read studied the effect of electrolyte and air cathode formulation on the electrochemical properties of an Li/O 2 organic electrolyte cell and found that electrolyte composition has the largest effect on discharge capacity and rate capability. 4 Both groups incorporated common organic solvents in the electrolyte, i.e., ethylene carbonate (EC), propylene carbonate (PC), 1,2-dimethoxyethane, diethyl carbonate (DEC), dimethyl carbonate, γ-butyrolactone, tetrahydrofuran, or tetrahydropyran. 3, 4 The highly reactive lithium metal cannot, however, be thermodynamically compatible with common organic solvents. The fact that the air cathode of Li/air cells must be open to the ambient environment poses
Solid polymer electrolytes with sulfur based ionic liquid for lithium batteries
Journal of Power Sources, 2011
Solid polymer electrolytes for lithium batteries possess increased safety over traditional carbonate electrolytes, but have not been shown effective at temperatures close to ambient. The inclusion of triethyl sulfonium based ionic liquids (IL) into poly(ethylene oxide) (PEO) homopolymers has demonstrated the ability to reach the necessary figures of merit for use in a lithium battery below physiological temperature. The effect of the anion for the IL and the lithium salt was measured for bis(perfluoroethylsulfonyl) imide, bis(oxalato) borate, perchlorate, hexafluorophosphate (PF 6 ) and bis(trifluorosulfonyl) imide (TFSI), and all showed ionic conductivity on the order of 1 mS/cm at physiological temperature. T Li + ranged from 0.19-0.31 for the systems and some anions demonstrated stability exceeding 5 V vs. Li/Li + . The ability to reversibly plate and strip lithium was also measured and was largely influenced by the resistance of the electrolyte-electrode interface. This research demonstrated that TFSI is the best choice of anions for the solid polymer electrolyte system, while PF 6 is the worst. The other anions demonstrated a range of properties that depending on the needed properties could potentially be favored relative to TFSI.