Bis Trifluoromethane Sulfonimide Lithium Research Articles

Transport and Dynamics of Ionic Species in Block Copolymer Electrolytes Obtained from NMR

Solvent-free block copolymers electrolytes are the strongest candidates for solid-state lithium metal batteries, as new polymers based on polyethylene oxide (PEO) and lithium bis(trifluoromethane)sulfonimide (LiTFSI) prevent the formation of lithium dendrites and ensure sufficient conductivity. Block copolymers based on PEO and either polystyrene (PS) or grafted PS-TFSI were compared to PEO by Nuclear Magnetic Resonance spectroscopy (NMR) in order to quantify and distinguish the transport and dynamics of Li+ and TFSI- and the effect of the polymer matrix. The self-diffusion coefficients of Li+ and TFSI- can be measured at various temperatures with pulsed-field-gradient (PFG) experiments and compared with electrical conductivity measurements, providing insights on lithium transport properties in each system. We measured 7Li NMR relaxation rates at various magnetic fields and temperatures, and we were able to extract complex correlation functions describing the fluctuations of the 7Li quadrupolar interaction inside the polymer matrix, yielding insights into cation dynamics with three different timescales. These results obtained from NMR can be compared to molecular dynamics or theoretical calculations.

Semi-interpenetrating polymer network of poly(methyl methacrylate) and ether-modified polysiloxane

Solid polymer electrolyte membranes are prepared as semi-interpenetrating networks (semi-IPN) by solution casting technique composed of poly(methyl methacrylate) (PMMA) as polymeric host matrix, polysiloxane-comb-propyloxymethoxytriglycol (PSx) as ion conducting component and lithium bis(trifluoromethane)sulfonimide (LiTFSI) as conducting salt. The resulting semi-IPN (net-poly(methyl methacrylate))-sipn-(polysiloxane-comb-propyloxymethoxytriglycol), is investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and impedance spectroscopy (IS). DSC measurements show two glass transitions (Tg-PSx, Tg-PMMA) indicating an independent coexistence of the PMMA host matrix and the PSx conducting component. FTIR spectroscopy reveals interactions between Li+ ions and the ether-functionality of PSx, whereas PMMA does not interact with the Li+. In order to distinguish PMMA and PSx contributions to the ionic transport, the effective ionic conductivity of PSx was calculated. The ionic conductivity of the semi-IPN is 3.1×10−6Scm−1 at room temperature.

Investigating polypropylene-poly(ethylene oxide)-polypropylene triblock copolymers as solid polymer electrolytes for lithium batteries

Abstract Syndiotactic polypropylene- b -poly(ethylene oxide)- b -syndiotactic polypropylene (PEOP) triblock copolymers were synthesized and solid polymer electrolytes were prepared by mixing with lithium bis(trifluoromethane)sulfonimide (LiTFSI) salt. PEOP formed strongly-segregated morphologies in the absence and presence of LiTFSI. LiTFSI inhibited poly(ethylene oxide) crystallization without affecting polypropylene crystallinity. The conductivity exhibited a non-monotonic dependence on molecular weight ( M n ) with a maximum near 20 kg/mol. In contrast, polystyrene- b -poly(ethylene oxide) electrolytes exhibit conductivity increasing monotonically with M n , up to a plateau in the high- M n limit. This suggests that non-conducting semi-crystalline microphases interfere with conducting pathways, while non-conducting amorphous microphases formed well-connected conducting pathways.

Study of carbamate-modified disiloxane in porous PVDF-HFP membranes: new electrolytes/separators for lithium-ion batteries.

A gel electrolyte membrane is obtained through the absorption of a carbamate-modified liquid disiloxane-containing lithium bis(trifluoromethane)sulfonimide (LiTFSI) by using macroporous poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) membranes. The porous membranes are prepared by means of a phase inversion technique. The resulting gel electrolyte membrane is studied by using differential scanning calorimetry, Fourier-transform infrared (FTIR) spectroscopy, and microscope mapping through coherent anti-Stokes Raman scattering (CARS) confocal microscopy and impedance spectroscopy. The ionic conductivity of the gel electrolyte is 10(-4) S cm(-1) at 20 °C. FTIR spectroscopy reveals interactions between LiTFSI and the carbonyl moiety of the disiloxane. No interactions between LiTFSI and PVDF-HFP or between disiloxane and PVDF-HFP are detected by FTIR spectroscopy. Furthermore, the distribution of the α and β/γ phases of PVDF-HFP and the homogeneous distribution of disiloxane/LiTFSI in the gel electrolyte membranes are examined by FTIR mapping. CARS confocal microscopy is used to image the three-dimensional interconnectivity, which reveals a reticulated structure of macrovoids in the porous PVDF-HFP framework. Owing to properties such as electrochemical and thermal stability of the disiloxane-based liquid electrolyte and the mechanical stability of the porous PVDF-HFP membrane, the gel electrolyte membranes presented herein are promising candidates for applications as electrolytes/separators in lithium-ion batteries.

Improving the self-discharge behavior of sulfur-polypyrrole cathode material by LiNO3 electrolyte additive

Self-discharge characteristics of Li/S cells using pure sulfur and sulfur-polypyrrole (S-PPy) cathode materials and lithium bis(trifluoromethane)sulfonimide (LiTFSI) as the electrolyte salt were investigated by monitoring the open circuit voltage, the electrochemical impedance change, and the capacity loss during or after storage at room temperature. Corrosion behavior of the aluminum current collector was studied using linear sweep voltammetry and optical microscope observations of aluminum substrate in aged cells. The results showed that the cell with a pure sulfur cathode suffered from severe self-discharge, which is attributed to the corrosion of the current collector by LiTFSI and a rapid shuttle mechanism. However, a PPy coating on the surface of sulfur particles can suppress the shuttle effect, giving better self-discharge performance. LiNO3 was investigated as a suitable electrolyte additive to prevent the self-discharge of Li/S cells. A self-discharge rate of 3.1 % was obtained for a cell with an S-PPy cathode and a modified electrolyte containing 0.4 M LiNO3. It was found that LiNO3 acts both as a corrosion inhibitor and a shuttle inhibitor. This respectively reduces the transformation of solid sulfur to soluble lithium polysulfides and prevents the dissolved sulfur and generated polysulfides from chemical reaction with the Li anode.

Simulation Study of the Lithium Ion Transport Mechanism in Ternary Polymer Electrolytes: The Critical Role of the Segmental Mobility

We present an extensive molecular dynamics (MD) simulation study of the lithium ion transport in ternary polymer electrolytes consisting of poly(ethylene oxide) (PEO), lithium-bis(trifluoromethane)sulfonimide (LiTFSI), and the ionic liquid N-methyl-N-propylpyrrolidinium bis(trifluoromethane)sulfonimide (PYR13TFSI). In particular, we focus on two different strategies by which the ternary electrolytes can be devised, namely by (a) adding the ionic liquid to PEO20LiTFSI and (b) substituting the PEO chains in PEO20LiTFSI by the ionic liquid. To grasp the changes of the overall lithium transport mechanism, we employ an analytical, Rouse-based cation transport model (Maitra et al. Phys. Rev. Lett. 2007, 98, 227802), which has originally been devised for binary PEO-based electrolytes. This model distinguishes three different microscopic transport mechanisms, each quantified by an individual time scale. In the course of our analysis, we extend this mathematical description to account for an entirely new transport mechanism, namely, the TFSI-supported diffusion of lithium ions decoupled from the PEO chains, which emerges for certain stoichiometries. We find that the segmental mobility plays a decisive role in PEO-based polymer electrolytes. That is, whereas the addition of the ionic liquid to PEO20LiTFSI plasticizes the polymer network and thus also increases the lithium diffusion, the amount of free, mobile ether oxygens reduces when substituting the PEO chains by the ionic liquid, which compensates the plasticizing effect. In total, our observations allow us to formulate some general principles about the lithium ion transport mechanism in ternary polymer electrolytes. Moreover, our insights also shed light on recent experimental observations (Joost et al. Electrochim. Acta 2012, 86, 330).

Superhydrophobic Conducting Polymers Based on Hydrocarbon Poly(3,4‐Ethylenedioxyselenophene)

We report the first studied example of wettability of conducting polymers based on poly(3,4-ethylenedioxyselenophene). Hydrocarbon 3,4-ethylenedioxyselenophene (C2H5 to C12H25) derivatives are synthesized and electropolymerized in propylene carbonate using lithium tetrafluoroborate (LiBF4) and lithium bistrifluoromethanesulfonimidate (LiTf2N) as electrolyte. Highly structured films are obtained from a C8H17 chain independent of the electrolyte used. Superhydrophobic properties with high adhesion are specifically reached if using a C12H25 chain and LiBF4. The surface morphology is porous and highly structured as the films consist of assemblies of nanofibrils.

Effect of thermal history on the ionic conductivity of block copolymer electrolytes

ABSTRACTWe have studied the effect of thermal history on ionic conductivity of block copolymer electrolytes. Previous work on block copolymer electrolytes composed of polystyrene‐b‐poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfone) imide (LiTFSI) salt was restricted to lamellar morphologies. This study addresses both cylindrical and lamellar morphologies. The conductivity of low molecular weight samples decreases after they are annealed. In contrast, the conductivity of high molecular weight samples is generally unaffected by annealing. These results are explained in the context of connectivity and composition of the conducting phase. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2013, 51, 927–934

Ionic Conductivity of Low Molecular Weight Block Copolymer Electrolytes

The ionic conductivity and glass transition temperatures of nanostructured block copolymer electrolytes composed of polystyrene-b-poly(ethylene oxide) (SEO) doped with lithium bis(trifluoromethanesulfone)imide (LiTFSI) were studied in the small molecular weight limit (between 2.7 and 13.7 kg mol–1). In this range, the annealed conductivity exhibits a nonmonotonic dependence on molecular weight, decreasing with increasing molecular weight in the small molecular weight limit before increasing when molecular weight exceeds about 10 kg mol–1. We show that annealed electrolyte conductivity is affected by two competing factors: the glass transition temperature of the insulating polystyrene (PS) block and the width of the conducting poly(ethylene oxide) (PEO) channel. In the low molecular weight limit, all ions are in contact with both PS and PEO segments. The intermixing between PS and PEO segments is restricted to an interfacial zone of width, λ. Our experiments suggest that λ is about 5 nm. The fraction of io...

A new series of cross-linked (meth)acrylate polymer electrolytes for energy storage

A series of methacrylate-crosslinked polymers were investigated as potential polymer electrolytes for energy storage application. Methacrylate ester crosslinkers (25–50mol.%) with different spacer lengths and MMA as comonomer were polymerised into thin films. Mixtures of ethylene carbonate and propylene carbonate (EC/PC) or alternatively the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI), both doped with lithium bis(trifluoromethane)sulfonimide (LiTFSI), fulfilled the role of electrolyte and porogen simultaneously. Ionic conductivity increased with increasing porogen content, Li ion concentration, and decreasing amounts of crosslinker (maximum values: 0.5mS/cm (EC/PC) and 4.5mS/cm (EMIM TFSI)). Thin films with permanent porosity were obtained for both electrolyte systems. The flexibility of the films increased with a lower concentration of crosslinker or the choice of a crosslinker with a longer spacer. The relationship between pore size, pore morphology, glass transition temperature and ionic conductivity on the other hand was complex and did not exhibit distinct trends. High thermal stability, ionic conductivity and tunable mechanical properties make these polymer thin films attractive candidates as in situ filled Li ion battery separator films either preformed or directly printed.

Electrochemical performance of a hybrid lithium-ion capacitor with a graphite anode preloaded from lithium bis(trifluoromethane)sulfonimide-based electrolyte

A hybrid LiC capacitor combining a lithium-ion battery type (graphite) electrode and an electrical double-layer (activated carbon) one has been developed by preloading graphite from 2molL−1 lithium bis(trifluoromethane)sulfonimide (LiTFSI) organic electrolyte. The graphite intercalation compound was formed by applying ca. 10 successive charge/self-discharge pulses. The optimized hybrid device operates in the voltage range from 1.5 to 4.2V and displays 60% higher gravimetric capacitance than an electric double-layer (EDL) capacitor using the same activated carbon for both electrodes. As a result, the energy density reaches 80Whkg−1, which is four times higher than the value for the EDL capacitor with the same total mass of carbon.

UV-curable semi-interpenetrating polymer network-integrated, highly bendable plastic crystal composite electrolytes for shape-conformable all-solid-state lithium ion batteries

Download options Please wait... Article information DOI https://doi.org/10.1039/C2EE03025J Article type Paper Submitted 31 Oct 2011 Accepted 17 Jan 2012 First published 17 Feb 2012 Download Citation Energy Environ. Sci., 2012,5, 6491-6499 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions UV-curable semi-interpenetrating polymer network-integrated, highly bendable plastic crystal composite electrolytes for shape-conformable all-solid-state lithium ion batteries H. Ha, E. Kil, Y. H. Kwon, J. Y. Kim, C. K. Lee and S. Lee, Energy Environ. Sci., 2012, 5, 6491 DOI: 10.1039/C2EE03025J To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Hyo-Jeong Ha Eun-Hye Kil Yo Han Kwon Je Young Kim Chang Kee Lee Sang-Young Lee

Conductivity of liquid lithium electrolytes with dispersed mesoporous silica particles

The electrical conductivity of disperse electrolytes was systematically measured as a function of temperature (0 °C to 60 °C) and filler content for different types of fillers with a range of pore geometry, pore structure and specific surface area. As fillers mesoporous silicas SBA-15, MCM-41 and KIT-6 with pore ranges between 3 nm and 15 nm were dispersed in commercially available liquid lithium electrolytes. As electrolytes 1 M of lithium hexafluorophosphate (LiPF 6) in a mixture of ethylene carbonate (EC) and diethylene carbonate (DEC) at the ratio 3:7 (wt/wt) and the same solvent mixture with 0.96 M lithium bis(trifluoromethanesulfon)imide (LiTFSI) were used. No conductivity enhancement could be observed, but with respect to safety aspects the highly viscous disperse pastes might be useful. The conductivity decrease varied considerably for the different fillers.

Effect of molecular weight on conductivity of polymer electrolytes

The ionic conductivity, σ, of mixtures of poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfone)imide (LiTFSI) was measured as a function of molecular weight of the PEO chains, M, over the range 0.2–5000 kg/mol. Our data are consistent with an expression σ = σ 0 + K/ M proposed by Shi and Vincent [Solid State Ionics 60 (1993)] where σ 0 and K are exponential and linear functions of inverse temperature respectively. Explicit expressions for σ 0 and K are provided.

New high-throughput methods of investigating polymer electrolytes

Polymer electrolyte films have been prepared by solution casting techniques from precursor solutions of a poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), lithium-bis(trifluoromethane) sulfonimide (LiTFSI), and propylene carbonate (PC). Arrays of graded composition were characterised by electrochemical impedance spectroscopy (EIS), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) using high throughput techniques. Impedance analysis showed the resistance of the films as a function of LiTFSI, PC and polymer content. The ternary plot of conductivity shows an area that combines a solid-like mechanical stability with high conductivity, 1×10−5Scm−1 at the composition 0.55/0.15/0.30wt% PVdF-HFP/LiTFSI/PC, increasing with PC content. In regions with less than a 50wt% fraction of PVdF-HFP the films were too soft to give meaningful results by this method. The DSC measurements on solvent free, salt-doped polymers show a reduced crystallinity, and high throughput XRD patterns show that non-polar crystalline phases are suppressed by the presence of LiTFSI and PC.

Understanding the Lithium Transport within a Rouse-Based Model for a PEO/LiTFSI Polymer Electrolyte

MD simulations of poly(ethylene oxide) (PEO) doped with lithium-bis(trifluoromethane)sulfonimide (LiTFSI) are analyzed with respect to the cation dynamics, the PEO dynamics as well as their coupling. Different cation transport mechanisms can be identified. These observations can be interpreted in terms of a recently proposed model of cation transport in polymer electrolytes. The model was capable of reproducing the lithium mean square displacement and self-diffusion coefficient. Because of the importance of interchain ion transfers for long-range ion transport, additional focus lies on the analysis of cations coordinated by two PEO chains, which is a common motif in this system.

Lithium-Ion-Conducting Electrolytes: From an Ionic Liquid to the Polymer Membrane

This work concerns the design, the synthesis, and the characterization of the -butyl--ethylpiperidinium -bis(trifluoro- methane)sulfonimide ionic liquid (IL). To impart Li-ion transport, a suitable amount of lithium -bis- (trifluoromethane)sulfonimide (LiTFSI) is added to the IL. The Li–IL mixture displays ionic conductivity values on the order of and an electrochemical stability window in the range of 1.8–4.5 V vs . 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 mixture is incorporated in a poly(vinylidene fluoride-co-hexafluoropropylene) matrix to form various electrolyte membranes with different 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 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.

Lithium solvation in a PMMA membrane plasticized by a lithium‐conducting ionic liquid based on 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide

AbstractThe Raman and Infrared (IR) spectra of poly(methyl methacrylate) (PMMA) membranes plasticized by ionic liquids of the (1 − x)[1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI)],xLiTFSI type, where BMI+ is the 1‐butyl‐3‐methylimidazolium cation and TFSI− the bis(trifluoromethanesulfonyl)imide anion, are analyzed for a lithium bis(trifluoromethane sulfone)imide (LiTFSI) mole fraction x = 0.23 and PMMA contents from 0 to 50 wt%. The lithium is found to have an average coordination of about three CO groups and less than one TFSI− anion. It plays the role of a cross‐linker between the ester groups of PMMA and the nonvolatile ionic liquid. Addition of PMMA to the (1 − x)(BMITFSI),xLiTFSI ionic liquid lowers the conductivity but might improve the lithium transference number by transforming the [Li(TFSI)2]− anionic clusters present in the pure ionic liquid into a mixed coordination by ester groups and TFSI− anions. Copyright © 2008 John Wiley & Sons, Ltd.

Sulfur–mesoporous carbon composites in conjunction with a novel ionic liquid electrolyte for lithium rechargeable batteries

Sulfur coated mesoporous carbon (S–C) composites have been synthesized and physically characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. Firstly, the electrochemical properties of the S–C composite cathode materials were tested in a conventional electrolyte consisting of 1 mol/L lithium bistrifluoromethanesulfonimidate in poly(ethylene glycol) dimethyl ether to compare them with pure sulfur electrode. The capacity and cyclic stability of the S–C composite were improved. Then the S–C composites were tested in a novel ionic liquid electrolyte consisting of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and lithium bistrifluoromethanesulfonimidate. The capacity and cyclic stability of the S–C composite using the ionic liquid electrolyte were much better than for the sample tested in a conventional organic solvent electrolyte.

Transport Properties of LiTFSI-Acetamide Room Temperature Molten Salt Electrolytes Applied in an Li-Ion Battery

In the present work some transport properties of the binary room temperature molten salt (RTMS) lithium bis(trifluoromethane sulfone)imide (LiTFSI)-acetamide [LiN(SO2CF3)2-CH3CONH2], applied in an Li-ion battery, have been investigated. The phase diagram was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The result reveals that the binary RTMS has an eutectic point at 201 K and the 30 mol% LiTFSI composition. The electric conductivity was measured using a direct current computerized method. The result shows that the conductivities of the melts increase with increasing temperature and acetamide content. The densities of all melts decrease with increasing temperature and acetamide content. The equivalent conductivities were fitted by the Arrhenius equation, where the activation energies were 18.15, 18.52, 20.35, 25.08 kJ/mol for 10, 20, 30, 40 mol% LiTFSI, respectively. Besides the relationships between conductivity, density composition and temperature, of the ion interaction is discussed.