Polymer Electrolytes For Lithium Batteries Research Articles

Blends of Pegylated Polyoctahedralsilsesquioxanes (POSS-PEG) and Methyl Cellulose as Solid Polymer Electrolytes for Lithium Batteries

Solid polymer electrolytes (SPEs) were prepared by blending LiClO4, methyl cellulose (MC) and an oligometric dendritic polyethylene glycol (PEG), formed from polyoctahedralsilsesquioxane functionalized with ∼ 8 PEG side chains (POSS-PEG) on the SiO1.5 core. Compositions with 80/20, 70/30 and 60/40 POSS-PEG/MC, and LiClO4 (O/Li=16/1) were investigated for their electrochemical, mechanical and morphological properties, where O/Li indicates the molar ratio of ether oxygens from POSS-PEG to Li+ ions. Since compatible blends can be made over a range of compositions, ranging from “tacky” with low amounts of MC, to “hard” with high percentages of MC, this system is a paradigm for preparing batteries with continuous interfaces from the electrodes to the SPE. SEM and TEM images indicate that POSS-PEG/LiClO4(O/Li=16/1)/MC form microporous structures in which the pore walls are microphase separated. In these microphase separated blends, the LiClO4 partitions into the POSS-PEG phase and is amorphous between −100°C and its decomposition temperature, Td ∼ 300°C, as evidenced by an increased glass transition temperature (Tg) for the POSS-PEG/LiClO4 phase, while the MC phase is semicrystalline, as evidenced by x-ray diffraction data, showing the persistance of crystalline regions of MC in the blends. At temperatures below the glass transition temperature (Tg) of POSS-PEG/LiClO4(O/Li=16/1) the moduli of the blends increase with increasing POSS-PEG content, indicating that the POSS-PEG component behaves like high molar mass polyethylene oxide (PEO) reinforced with SiO1.5. At temperatures T>Tg (POSS-PEG/LiClO4), where POSS-PEG/LiClO4 is highly viscous (does not flow under its own weight) but not a true solid, the moduli of the blends increase with MC content, consistent with the high modulus MC forming cross-link sites to the dominant POSS-PEG/LiClO4 phase. It is proposed that these crosslink sites are due to residual primary OH groups from MC that form hydrogen bonds with ether oxygens of POSS-PEG/LiClO4 and result in a rubbery morphology (32 - 156MPa) at room temperature, with the Li+ ions preferentially binding to the ether oxygens in the interior of the microphase separated regions. Conductivities of 1.6×10−5 and 1.1×10−6 S/cm were measured at 30°C and 0°C, respectively, for the 80/20 POSS-PEG/LiClO4 (O/Li=16/1)/MC blend. Stability and reversibility of the blends at 50°C were observed in the range 1.5 to 4.2V.

Single-Ion-Conducting Nanocomposite Polymer Electrolytes for Lithium Batteries Based on Lithiated-Fluorinated-Iron Oxide and Poly(ethylene glycol) 400

A poly(ethylene glycol) 400 (PEG400) matrix doped with different amounts of a fluorinated Fe2O3-based nanofiller (LiFI) featuring a Li+-functionalised surface gives rise to nanocomposite polymer electrolytes (nCPEs) that demonstrate single-ion conduction. A family of nCPEs with general formula [PEG400/(LiFI)y] and y=nFe/nPEG400 ranging from 0 to 8.15 are prepared; they are characterized by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), High-Resolution Thermogravimetric Analysis (HR-TGA), Differential Scanning Calorimetry (DSC), and Fourier-transform vibrational spectroscopy in both the medium (MIR) and far (FIR) infrared. The Li+ transference number, tLi+,is determined and Broadband Electrical Spectroscopy (BES) is used to elucidate the electrical response of the materials in terms of polarization and relaxation events. The combination of the information obtained by all the aforementioned techniques enables us to present a possible conduction mechanism for these nCPEs single-ion conducting systems.

Highly Conducting 3D-Hybrid Polymer Electrolytes for Lithium Batteries Based on Siloxane Networks and Cross-Linked Organic Polar Interphases

The development of polymer electrolytes with high ionic conductivity, high lithium transference number, and high electrochemical stability is one of the main aims in the field of lithium battery research. In this work, we describe the synthesis and the characterization of new electrolyte systems, composed of three-dimensional hybrid inorganic–organic networks doped with LiClO4. The preparation route comprises only three steps, namely a sol–gel reaction, salt dissolution, and an epoxide polymerization reaction. The lithium concentration, and thus the lithium transference number, was modulated by adding lithium hydroxide in the sol–gel step. In this way, seven electrolytes with varying salt concentrations were prepared. The hybrid electrolytes are characterized by good ionic conductivities (up to 8·10–5 S/cm at room temperature) and high thermo-mechanical and electrochemical stabilities. Stability tests versus lithium metal via galvanostatic polarization showed that this material is superior with respect to...

Functionalized polystyrene based single ion conducting gel polymer electrolyte for lithium batteries

Lithium poly(4-styrene sulfonyl (phenylsulfonyl)imide) (PSSPSI) was synthesized through the Hinsberg reaction. Since the bis(sulfonyl)imide anion is immobilized in the polymer chain, the lithium cation transference number was measured to be 0.87. The weight average number molecular weight (Mw) was found to be 105,343 determined by gel permeation chromatography (GPC). A gel polymer electrolyte membrane, comprising of PVDF and PSSPSI, was successfully prepared with the ionic conductivity of 1.1×10−3Scm−1 at room temperature. The membrane exhibits a wide electrochemical window up to 4.5V (vs. Li+/Li) and is thermally and mechanically stable. The material is well suited for applications in lithium-ion batteries.

Multilayer Separator for Lithium Batteries

Lithium metal provides the highest specific energy density and would be a perfect anode material for a lithium ion battery [1]. But so far only polymer batteries based on PEO show a stable interaction with lithium metal [2-3]. However, these electrolytes feature only a low ionic conductivity (up to 10-3 S cm-1) at room temperature. To use lithium metal in combination with liquid electrolytes, a thin layer (10 μm) of polyethylene oxide (PEO) was coated on conventional separators. A simple, solvent free technique was used to combine the polymer electrolyte to the separator (patent pending). To enhance the mechanical stability during the swelling with electrolyte, the polymer was cross-linked after the coating step [4].An application of the polymer/separator system is possible with established positive electrode materials like lithium iron phosphate (LFP) or lithium nickel manganese cobalt oxide (NMC) to enhance the energy density of the system. Even more promising is the use in next generation battery systems like lithium air and lithium-sulfur. The thin layer of PEO optimizes the lithium-electrolyte interface and therefore acts as a protective layer against parasitic reactions like electrolyte decomposition [5]. In Li-O2and Li-S batteries, the PEO could additionally act as a barrier against, respectively, oxygen or polysulfide diffusion to the lithium anode.The PEO layer was found to be mechanically stable during cell assembling and electrolyte application. Due to the cross-linking, even an excess of electrolyte does not dissolve the polymer. By chemical bonding between the PEO and polyethylene (PE) or polypropylene (PP) a loss of connection between the two separator layers is prevented. Partly impregnation of PEO into porous ceramic separators during the coating process shows the same effect after cross-linking. Differential scanning calorimetry (DSC) tests show that PEO and ionic liquids form an amorphous layer on the lithium surface, similar to ternary polymer electrolytes [6].To verify the electrochemical stability of the PEO on the lithium metal surface, stripping-plating tests in symmetrical lithium cells were performed with a broad range of electrolytes. For established cathode materials, carbonate-based solvents like ethylene carbonate (EC) and dimethyl carbonate (DMC) with lithium hexafluorophosphate (LiPF6) were investigated. For next generation batteries or cycling at higher temperatures, tests with tetraethylene glycol dimethyl ether (TEGDME), 1,3-dioxolane and ionic liquids like 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were performed. Finally, cycling tests with NMC and sulfur cathodes were performed.1. Bruce, P.G., et al., Li-O2 and Li-S batteries with high energy storage. Nat Mater, 2012. 11(02): p. 172-172.2. Li, Z., et al., A review of lithium deposition in lithium-ion and lithium metal secondary batteries.Journal of Power Sources, (0).3. Kim, G.T., et al., UV cross-linked, lithium-conducting ternary polymer electrolytes containing ionic liquids. Journal of Power Sources, 2010. 195(18): p. 6130-6137.4. Rupp, B., et al., Polymer electrolyte for lithium batteries based on photochemically crosslinked poly(ethylene oxide) and ionic liquid. European Polymer Journal, 2008. 44(9): p. 2986-2990.5. Peled, E., et al., The sei model—application to lithium-polymer electrolyte batteries. Electrochimica Acta, 1995. 40(13–14): p. 2197-2204.6. Joost, M., et al., Phase stability of Li-ion conductive, ternary solid polymer electrolytes. Electrochimica Acta, 2013. 113(0): p. 181-185.

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.

Application of Highly Ordered Polymer Resin As Gel Polymer Electrolyte for Lithium Batteries

not Available.

A new branched copolyether-based polymer electrolyte for lithium batteries

Abstract A series of novel branched copolyethers, poly((1,3-dioxlolane)-co-((2-(2-methoxylethoxyl)methyl)oxirane)) (P(DXL-co-MEMO)) and poly((1,3-dioxlolane)-co-((2-(2-(2-methoxylethoxyl)ethoxyl)methyl)oxirane)) (P(DXL-co-ME2MO)), were synthesized via cationic polymerization, and the structures of these copolymers were characterized by 1H NMR and GPC. Ionic conductivities of copolyether/lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), polyethylene oxide (PEO)/LiTFSI and PEO/copolyether/LiTFSI were investigated via electrochemical impedance spectroscopy. The results showed that the ionic conductivity of the P(DXL-co-MEMO)/LiTFSI polymer electrolyte was higher than that of the P(DXL-co-ME2MO)/LiTFSI polymer electrolyte, and the room temperature ionic conductivity of the P(DXL-co-MEMO)/LiTFSI polymer electrolyte was up to 2.2 × 10− 4 S cm− 1. Compared with the PEO/LiTFSI polymer electrolyte, the ionic conductivities of the PEO/copolyether/LiTFSI composite polymer electrolytes had a great improvement, but their thermal stabilities did not obviously reduce.

Synthesis by UV-curing and characterisation of polyurethane acrylate-lithium salts-based polymer electrolytes in lithium batteries

AbstractUV-cured caprolactone-based polyurethane acrylate (PUA) polymer blend electrolytes were prepared and characterised. To develop polymer electrolytes suited to ambient temperature, an ionically-conductive and reliable polymer electrolyte based on urethane acrylate resins synthesised from a fluorine-containing di-functional oligomer 6F ethoxylated diacrylate, a di-functional reactive diluent 1,6-hexanediol diacrylate for adjusting the viscosity, and a radical photo-initiator doped with a mixture of lithium salts were used. Free-standing flexible electrolyte films were prepared by UV-curing via free-radical photopolymerisation. The performance of the lithium polymer cell system (Li/PE(F4)/LiCoO2) was determined by electrochemical impedance spectroscopy, cyclic voltammetry, a galvanostatic recurrent differential pulse, chronocoulometry and chronoamperometry. The electrolyte with optimal amounts of fluorine-containing oligomer and optimal salt mixture content exhibited enhanced conductivity, showing a conductivity of 1.00 × 10−4 S cm−1 at ambient temperature. The specific capacity, specific energy and specific power of a Li/PE(F4)/LiCoO2 cell were also determined.

Enhanced Lithium Battery with Polyethylene Oxide‐Based Electrolyte Containing Silane–Al2O3 Ceramic Filler

A solid polymer electrolyte prepared by using a solvent-free, scalable technique is reported. The membrane is formed by low-energy ball milling followed by hot-pressing of dry powdered polyethylene oxide polymer, LiCF3 SO3 salt, and silane-treated Al2 O3 (Al2 O3 -ST) ceramic filler. The effects of the ceramic fillers on the properties of the ionically conducting solid electrolyte membrane are characterized by using electrochemical impedance spectroscopy, XRD, differential scanning calorimeter, SEM, and galvanostatic cycling in lithium cells with a LiFePO4 cathode. We demonstrate that the membrane containing Al2 O3 -ST ceramic filler performs well in terms of ionic conductivity, thermal properties, and lithium transference number. Furthermore, we show that the lithium cells, which use the new electrolyte together with the LiFePO4 electrode, operate within 65 and 90 °C with high efficiency and long cycle life. Hence, the Al2 O3 -ST ceramic can be efficiently used as a ceramic filler to enhance the performance of solid polymer electrolytes in lithium batteries.

Polymer electrolytes integrated with ionic liquids for future electrochemical devices

AbstractThe global energy crisis and an increase in environmental pollution in the recent years have drawn the attention of the scientific community towards the development of efficient electrochemical devices. Polymers containing charged species have the potential to serve as electrolytes in next‐generation devices and achieving high ion transport properties in these electrolytes is the key to improving their efficiency. In this article, we explore ways to improve the ion transport properties of solid polymer electrolytes by focusing on the use of ionic liquids (ILs). The application of IL‐incorporated polymer electrolytes in lithium batteries, high temperature fuel cells, and electro‐active actuators is summarized. For each system, the current level of understanding of the diverse factors affecting the transport properties of polymer electrolytes integrated with ILs is presented, in addition to the challenges encountered and strategies toward obtaining significantly improved device performances. The creation of self‐assembled morphologies in IL‐containing polymer electrolytes by the use of block copolymers is particularly highlighted as a novel prospective technique geared towards obtaining next‐generation electrochemical devices with enhanced performances. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

“Pore/bead” membrane for rechargeable lithium ion batteries

AbstractA special “pore/bead” membrane was prepared with a mesoporous inorganic filler (MCM‐41) and a P(VDF‐HFP) binder. The special “pore/bead” structure of the MCM‐41 filler not only enhanced the puncture strength of the membrane but also improved its ionic conductivity. The puncture strength of the dried “pore/bead” membrane (MCM‐41 : P(VDF‐HFP) = 1 : 1.5) was 18 N, and showed a slight decrease (16 N) after the membrane was wetted by liquid electrolyte. Additionally, the composite membrane showed excellent thermal dimensional stability. The composite membrane could be activated by adding 1M LiClO4‐EC/DMC (1 : 1 by volume). The activated membrane displayed a high ionic conductivity about 3.4 × 10−3 S cm−1 at room temperature. Its electrochemical stability window was up to 5.3 V vs. Li/Li+, indicating that it was very suitable for lithium‐ion battery application. The battery assembled using the composite electrolyte also showed reasonably good high‐rate performance. The approach of preparing a “pore/bead” membrane provides a new avenue for improving both the conductivity and the mechanical strength of polymer electrolytes for lithium batteries. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Anion Effects on Solid Polymer Electrolytes Containing Sulfur Based Ionic Liquid for Lithium Batteries

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 (PF6) and bis(trifluorosulfonyl) imide (TFSI), and all showed ionic conductivity on the order of 1 mS/cm at physiological temperature. TLi+ 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 PF6 is the worst. The other anions demonstrated a range of properties that depending on the needed properties could potentially be favored relative to TFSI.

Solid polymer electrolytes with sulfur based ionic liquid for lithium batteries

The electrochemical properties of a solid hybrid polymer electrolyte for lithium batteries based upon tri-ethyl sulfonium bis(trifluorosulfonyl) imide (S 2TFSI), lithium TFSI, and poly(ethylene oxide) (PEO) is presented. We have synthesized homogenous freestanding films that possess low temperature ionic conductivity and wide electrochemical stability. The hybrid electrolyte has demonstrated ionic conductivity of 0.117 mS cm −1 at 0 °C, and 1.20 mS cm −1 at 25 °C. At slightly elevated temperature ionic conductivity is on the order of 10 mS cm −1. The hybrid electrolyte has demonstrated reversible stability against metallic lithium at the anodic interface and >4.5 V vs. Li/Li + at the cathodic interface.

Electrochemical and mechanical properties of nanochitin-incorporated PVDF-HFP-based polymer electrolytes for lithium batteries

Nanocomposite polymer electrolytes (NCPE) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) and chitin for different concentrations of LiClO4 have been prepared by a hot-press technique. The prepared NCPE films were subjected to XRD, SEM, FTIR and tensile analyses. The thermal stability of NCPE membrane was investigated by TG-DTA. Ionic conductivity studies have also been made as a function of lithium salt concentration for different temperatures ranging from 0 to 80 °C. The polymeric membrane comprising PVDF-HFP/chitin/LiClO4 of ratio 75:20:5 (wt.%) offered maximum ionic conductivity. Thermal study reveals that these membranes are stable up to 260 °C.

A study incorporating nano-sized silica into PVC-blend-based polymer electrolytes for lithium batteries

Blends of poly(vinyl chloride)-poly(methyl methacrylate) (PVC/PMMA) and poly(vinyl chloride)-poly(ethylene oxide) (PVC/PEO) with lithium triflate (LiCF3SO3) as salt, ethylene carbonate (EC), and dibuthyl phthalate (DBP) as plasticizers and nano-sized silica (SiO2) as filler, the first of its kind in such a study, were prepared using the solution-cast technique. This study affirmed that SiO2 added PVC-PMMA and PVC-PEO-blend-based polymer electrolytes have the ability to retain their ionic conductivity and integrity even after 60 days of storage time at room temperature. The reduction of ionic conductivity values in PVC-PMMA-LiCF3SO3-DBP-EC:SiO2-based and SiO2-free membranes are 9 and 30%, respectively. When PVC-PEO-blend was used, the reduction of ionic conductivity values in PVC-PEO-LiCF3SO3-DBP-EC:SiO2-based and SiO2-free system was 16 and 40%, respectively, after 60 days of storage also at room temperature. The SiO2-based complexes were also found to maintain their conductivity at higher temperatures of 60 °C and 90 °C with progressive storage times. This clearly shows that the SiO2-induced stabilizing effect is maintained even at higher temperatures. Silica has brought the conductivity of polymer electrolytes into the useful realm for materials in lithium polymer battery applications.

Ionic Liquids in Polymer Electrolytes for Lithium Batteries

not Available.

Effect of Ion Distribution on Conductivity of Block Copolymer Electrolytes

Energy-filtered transmission electron microscopy (EFTEM) was used to determine the distribution of lithium ions in solid polymer electrolytes for lithium batteries. The electrolytes of interest are mixtures of bis(trifluoromethane)sulfonimide lithium salt and symmetric poly(styrene-block-ethylene oxide) copolymers (SEO). In contrast to current solid and liquid electrolytes, the conductivity of SEO/salt mixtures increases with increasing molecular weight of the copolymers. EFTEM results show that the salt is increasingly localized in the middle of the poly(ethylene oxide) (PEO) lamellae as the molecular weight of the copolymers is increased. Calculations of the inhomogeneous local stress field in block copolymer microdomains, modeled using self-consistent field theory, provide a quantitative explanation for this observation. These stresses, which increase with increasing molecular weight, interfere with the ability of PEO chains to coordinate with lithium cations near the walls of the PEO channels where ion mobility is expected to be low.

Development of electrospun PVdF–PAN membrane-based polymer electrolytes for lithium batteries

Electrospun fibrous membranes of composites of polyvinylidene fluoride and polyacrylonitrile (PVdF–PAN–ESFMs) are prepared with different proportions of PAN (25, 50 and 75%, w/w). The morphology of the ESFMs is examined by field emission scanning electron microscopy (FESEM). FESEM image of PVdF–ESFM reveals that the fibers have uniform diameters and smooth surfaces. However, the fibers of PVdF–PAN–ESFMs are interconnected with large number of voids and cavities of different sizes. These voids are effectively utilized for the preparation of polymer electrolytes by loading lithium perchlorate dissolved in propylene carbonate. PVdF–PAN–ESFM with 25% PAN (designated as PVdF–PAN(25)–ESFM) could load a high amount of lithium salt with electrolyte uptake of more than 300%. PVdF–PAN(25)–ESFM electrolyte exhibits a high conductivity of 7.8 mS cm −1 at 25 °C and electrochemically stable up to 5.1 V. Also, the addition of PAN into PVdF decreases the interfacial resistance with lithium electrode. PVdF–PAN–ESFM electrolytes have complementary advantageous characteristics of PVdF and PAN. The promising results reported here clearly indicate that polymer electrolytes based on PVdF–PAN–ESFMs are most suited for lithium batteries.

Polymer electrolyte for lithium batteries based on photochemically crosslinked poly(ethylene oxide) and ionic liquid

Polymer/ionic liquid composites were investigated as solvent-free electrolytes for lithium batteries. Ternary electrolytes based upon poly(ethylene oxide), an ionic liquid and a conducting salt were UV crosslinked with benzophenone as the photoinitiator. Crosslinking leads to an increase in mechanical stability of the PEO composites. This straight-forward process provides a way to increase the content of ionic liquid and thus to raise ionic conductivity without loss of mechanical stability. Impedance measurements showed that the ionic conductivity of the composites is not affected by the UV curing process. Moreover, the UV curing process causes a decrease in the degree of crystallinity in the PEO composites which contributes to an increase in ionic conductivity. The present work is related to safety issues of lithium batteries.