Propylene Carbonate Content Research Articles

CO2 separation from biogas with ionic liquid-based hybrid solvents: From properties to process

In this work, ionic liquids (ILs)-based hybrid solvents, consisting of 1-butyl-3-methylimidazolium acetate (BMAC)-propylene carbonate (PC), were developed for CO2 separation from biogas. The impacts of IL mass fraction and temperature on the absorption capacity, viscosity, and density were studied. Feed gases, including pure CO2, pure CH4, and synthetic biogas, were tested, and the results were evaluated and compared. Thermodynamic modeling was used to represent the newly measured results together with literature data, and a systematic process simulation and evaluation were conducted. The measurements show an enhanced CO2 solubility with an increased BMAC mass fraction and decreased temperature. An increased viscosity was observed with increasing BMAC mass fraction and decreasing temperature. In addition, the type of feed gas holds a neglectable effect on CO2 and CH4 absorption capacities. To find an optimal mass fraction of BMAC-PC and quantify the performance, in the process simulation and evaluation, two types of regeneration blocks, i.e., air-blow regeneration and thermal regeneration, were involved. It shows that the process with thermal regeneration block requires less energy and lower capture cost than the process with the air-blow regeneration, which indicates a superior affinity to thermal regeneration when BMAC is presented in the solvent system. Also, the decrease in PC content firstly decreases and then increases the energy demand, and the minimum energy demand of 23.4 kW can be found with wIL = 0.3, which reduces by 33.5% compared to pure PC. Similarly, the minimum capture cost of 68 $/ton-CO2 can be found with wIL = 0.3, representing a 21% reduction from the case with pure PC. The further analysis concludes a major reduction in the utility cost by 48%.

Process parameters of microsphere preparation based on propylene carbonate emulsion-precursors

Aim This study aimed for a detailed understanding of the impact of different process parameters involved during celecoxib-loaded microsphere preparation based on propylene carbonate emulsion-precursors. Methods Microspheres were prepared by a modified emulsification-solvent extraction method. Performed investigations included polymer solubility and viscosity, microsphere size, morphology and stability, propylene carbonate content as well as celecoxib solid state, content and release. Results Rough-walled round microspheres with sizes between 21 µm and 122 µm and an internal sponge-like structure filled with residual propylene carbonate (content between 1.9 ± 0.1% and 6.7 ± 0.5% w/w) were obtained. Encapsulation efficiencies varied between 28.3 ± 0.1% and 66.8 ± 1.0%. The release rates were affected by the polymer concentration, the emulsion phase ratio and the residual propylene carbonate content (t50% varied between 2.2 hours and 23.4 hours). Conclusions This study identified the most relevant process parameters for this new preparation method for the model drug celecoxib.

Facile Room-Temperature Preparation of Flexible Polyurethane Foams from Carbon Dioxide Based Poly(ether carbonate) Polyols with a Reduced Generation of Acetaldehyde.

Carbon dioxide (CO2) is becoming more attractive as a renewable feedstock for chemical synthesis. In this study, CO2 was incorporated into poly(ether carbonate) (PEC) polyols by using a double-metal-cyanide catalyst. By adjusting the CO2 pressure, the content of propylene carbonate units in the PEC polyols was controlled, indicating successful and semiquantitative incorporation of CO2 into the PEC polyols. Polyurethane foams (PUFs) with different propylene carbonate content were easily prepared at room temperature by employing the PEC polyols due to their adequate viscosity under ambient conditions. The firmness of the PUFs increased as the amount of propylene carbonate units increased due to the rigidity of the carbonate linkage, representing predictable mechanical properties. Interestingly, reduced generation of volatile organic compounds (VOCs) from the PUFs, namely acetaldehyde, was observed with a high content of propylene carbonate units at 120 °C, indicating good stability of the carbonate units against thermo-oxidative decomposition. This study demonstrates the importance of CO2 as an environmental-friendly and renewable resource that can provide not only industrially important but also problem-solving products in terms of processability and low generation of VOCs.

Monochromatic "Photoinitibitor"-Mediated Holographic Photopolymer Electrolytes for Lithium-Ion Batteries.

A new polymer electrolyte based on holographic photopolymer is designed and fabricated. Ethylene carbonate (EC) and propylene carbonate (PC) are introduced as the photoinert substances. Upon laser‐interference‐pattern illumination, photopolymerization occurs within the constructive regions which subsequently results in a phase separation between the photogenerated polymer and unreacted EC–PC, affording holographic photopolymer electrolytes (HPEs) with a pitch of ≈740 nm. Interestingly, both diffraction efficiency and ionic conductivity increase with an augmentation of the EC–PC content. With 50 wt% of EC–PC, the diffraction efficiency and ionic conductivity are ≈60% and 2.13 × 10−4 S cm−1 at 30 °C, respectively, which are 60 times and 5 orders of magnitude larger than the electrolyte without EC–PC. Notably, the HPEs afford better anisotropy and more stable electrochemical properties when incorporating N,N‐dimethylacrylamide. The HPEs exhibit good toughness under bending, excellent optical transparency under ambient conditions, and astonishing capabilities of reconstructing colored images. The HPEs here open a door to design flexible and transparent electronics with good mechanical, electrical, and optical functions.

Evaluating performance of wet unencapsulated PEDOT trilayer actuators operating in air and water

Ionically electroactive devices with no encapsulation dry out in air if a solvent-based electrolyte is used, and exchange ions in wet environments, both of which cause the performance of the device to vary over time. In this paper, we investigate the behavior of bare poly(3, 4-ethylenedioxythiophene) trilayer actuators both in intermittent use and continuous cycling in open air and in water, in order to understand how their response changes with time and solvent loss. Not surprisingly, the devices slow as solvent evaporates, but, unexpectedly, the active displacement increases until a large fraction of the solvent is gone. The electrolyte used in these 360 μm thick devices is a 1 M solution of Bis(trifluoromethane)sulfonimide lithium salt (Li+TFSI−) in propylene carbonate (PC). The trilayers lose all their solvent within 8 d, with ∼40% loss within a day, when stored in an environment with controlled temperature and relative humidity of (23 ± 2)°C and (50 ± 3)%, respectively. The devices’ speeds slow as the PC evaporates from the device (staying within 10% of their initial value after losing ∼20% of its PC content). Intermittent testing shows displacement of the device actually increases until only ∼14% of the PC content remains which would take almost 4 d if the device is stored in the controlled conditions mentioned above. This is largely due to the reduction of thickness in the trilayers, which then leads to higher curvature. Cycling in open air or in water leads to immediate displacement decrease: dropping 60% over one hour cycling in air and over 12 min cycling in water-due to the reduction of charge transfer rate. Overall, for applications where speed is not critical and operation is only needed for a matter of hours or days, encapsulation may not necessary. We expect that encapsulation will be beneficial to maintain the intermittent operation of the device and to maintain speed for longer periods of use (beyond 4 d and 12 h, respectively in the case studied). Encapsulation should also allow a stable displacement amplitude over time.

Identification of the behavior of properties of a cold-hardening glass-liquid mixture with propylene-carbonate different in dosing components

The object of research are models that describe the effect of liquid glass and propylene carbonate as a hardener of the molding mixture on its properties. One of the most problematic places is determination of the behavior of the properties of the mixture under conditions of deviation from the optimal values of the content of liquid glass as a binder and propylene carbonate as a hardener. The definition of such behavior is important because it will improve the processes of regulating the loading of mixers in automated systems for the manufacture of the mixture in foundries.The methods of canonical transformation of response surfaces are used, describing the effect of the content of liquid glass and propylene carbonate on the following properties of the mixture: survivability, compressive strength after 1 hour, after 3 hours, after 24 hours, crumbling. The mechanisms of chemical reactions that lead to the process of mixture curing are described and the possibility of obtaining qualitative characteristics of the mixture is substantiated by analyzing the chemistry of the process.An analytical description of the response surface in the stationary region in the factor space transformed after the standard procedure “liquid glass content – propylene carbonate content” is obtained in canonical form. Such a transformation allows to estimate the nature of the response surface by analyzing the ratios of the eigenvalues included in its canonical description in terms of size and sign. Such an approach used has an important feature, since it allows one to directly determine the behavior of the properties of the mixture in the event of deviations from the optimal values of the content of liquid glass and propylene carbonate.This makes it possible to determine measures or technical solutions for the work or to improve the systems for regulating dosing processes in automated systems for the production of a mixture in foundries. At the same time, adaptation to any known dosing systems of binder and hardeners of cold-hardening mixtures is possible. This opens up prospects for stabilizing the quality of the molding or core mixture and improving the quality of shaped castings for mechanical engineering, in particular, responsible and basic cast parts of internal combustion engines (ICE).

Synergistic film-forming effect of oligo(ethylene oxide)-functionalized trimethoxysilane and propylene carbonate electrolytes on graphite anode

Oligo(ethylene oxide)-functionalized trialkoxysilanes can be used as novel electrolytes for high-voltage cathode, such as LiCoO2 (4.35 V) and Li1.2Ni0.2Mn0.6O2 (4.6 V); however, they are not well compatible with graphite anode. In this study, a synergistic solid electrolyte interphase (SEI) film-forming effect between [3-[2-(2-methoxyethoxy)ethoxy]propyl]-trimethoxysilane (TMSM2) and propylene carbonate (PC) on graphite electrode was investigated. Excellent SEI film-forming capability and cycling performance was observed in graphite/Li cells using the electrolyte of 1 M LiPF6 in the binary solvent of TMSM2 and PC, with the PC content in the range of 10–30 vol.%. Meanwhile, the graphite/Li cells delivered higher specific capacity and better capacity retention in the electrolyte of 1 M LiPF6 in TMSM2 and PC (TMSM2:PC = 9:1, by vol.), compared with those in the electrolyte of 1 M LiPF6 in TMSM2 and EC (TMSM2:EC = 9:1, by vol.). The synergistic SEI film-forming properties of TMSM2 and PC on the surface of graphite anode was characterized by electrolyte solution structure analysis through Raman spectroscopy and surface analysis detected by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR) analysis.

(Invited) CsPF6 and Propylene Carbonate in Conventional LiPF6/Carbonate Electrolytes for Enhanced Lithium-Ion Battery Performances in Wide Temperature Range

Lithium-ion batteries (LIBs) have achieved great successes in portable electronic devices and have now started to enter the large-scale energy storage applications in transportations (such as pure electric vehicles and plug-in hybrid electric vehicles) and smart grid. Graphite is widely used as the anode material in the state-of-the-art LIBs. However, the graphite anode is usually only compatible with an ethylene carbonate (EC)-based electrolyte. In a propylene carbonate (PC)-containing electrolyte, which is advantageous over the EC-based counterpart due to its wider temperature range and lower cost, the graphite anode experiences significant exfoliation problem by the PC intercalation during the Li+ intercalation at charging steps. Thus a PC-containing electrolyte cannot be used in LIBs with graphite anode unless some solid electrolyte interphase (SEI) film-formation additives are included in the electrolytes. Such SEI formation additives normally contain unsaturated bonds or are unstable cyclic compounds, e.g. vinylene carbonate (VC), fluoroethylene carbonate (FEC), and lithium bis(oxalato)borate (LiBOB). They play an important role in the protection of the graphite structure from destruction by PC intercalation. However, these additives usually result in a thick SEI layer, which greatly reduces rate capability, limits low-temperature performance and hampers cycling stability at elevated temperatures through additional impedance and poor thermal stability.Recently, we have demonstrated that cesium cation (Cs+) as a novel electrolyte additive can direct the formation of a uniform, ultrathin and compact SEI layer on graphite electrode surface in EC-PC-containing electrolytes.[1] This SEI can not only significantly improve the compatibility between graphite anode and PC-containing electrolyte, but also lead to superior rate capability, enhanced low-temperature discharge performance, and excellent cycling stability at elevated temperatures.We also foundthat PC content in the electrolytes has great effect on the performances of graphite anode in half cells and full cells, and an optimal PC content of 20% by weight in solvent mixtures is identified.[2] The synergistic effects of Cs+ additive and appropriate amount of PC enable the formation of a robust, ultrathin and compact SEI layer on the surface of graphite electrode, which is only permeable for de-solvated Li+ ions and allows fast Li+ transport through it. In the continuation study, we further optimized the electrolyte formulations with CsPF6 additive by adjusting the EC and PC contents in electrolytes and evaluated the performances of graphite||LiNi0.80Co0.15Al0.05O2 full cells in terms of cycling at room temperature and elevated temperature, rate capacity and low-temperature discharge. One optimized electrolyte formulation is found to give about 70% discharge capacity retention at -40°C when compared to the room temperature discharge of the full cells, and simultaneously maintains other excellent performances. It is indicated that the optimal electrolyte consisting of CsPF6 and PC in conventional LiPF6/EC-based electrolyte is of great potential use in the state-of-the-art LIBs. The details of the results will be reported at the meeting. Acknowledgements This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, the Advanced Battery Materials Research Programs of the U.S. Department of Energy (DOE), and the Laboratory Directed Research and Development (LDRD) Project under the Technology Investment Program at Pacific Northwest National Laboratory (PNNL). The microscopy and spectroscopy measurements were performed at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL.

Controlled synthesis of CO2-diol from renewable starter by reducing acid value through preactivation approach

Synthesis of polyols from carbon dioxide (CO2) is attractive from the viewpoint of sustainable development of polyurethane industry; it is also interesting to adjust the structure of the CO2-polyols for versatile requirement of polyurethane. However, when renewable malonic acid was used as a starter, the copolymerization reaction of CO2 and propylene oxide (PO) was uncontrollable, since it proceeded slowly (13 h) and produced 40.4 wt% of byproduct propylene carbonate (PC) with a low productivity of 0.34 kg/g. A careful analysis disclosed that the acid value of the copolymerization medium was the key factor for controlling the copolymerization reaction. Therefore, a preactivation approach was developed to dramatically reduce the acid value to ~0.6 mg(KOH)/g by homopolymerization of PO into oligo-ether-diol under the initiation of malonic acid, which ensured the controllable copolymerization, where the copolymerization time could be shortened by 77% from 13 to 3 h, the PC content was reduced by 76% from 40.4 wt% to 9.4 wt%, and the productivity increased by 61% from 0.34 to 0.55 kg/g. Moreover, by means of preactivation approach, the molecular weight as well as the carbonate unit content in the CO2-diol was also controllable.

Effects of Propylene Carbonate Content in CsPF6-Containing Electrolytes on the Enhanced Performances of Graphite Electrode for Lithium-Ion Batteries

The effects of propylene carbonate (PC) content in CsPF6-containing electrolytes on the performances of graphite electrode in lithium half cells and in graphite∥LiNi0.80Co0.15Al0.05O2 (NCA) full cells are investigated. It is found that the performance of graphite electrode is significantly affected by PC content in the CsPF6-containing electrolytes. An optimal PC content of 20% by weight in the solvent mixtures is identified. The enhanced electrochemical performance of graphite electrode can be attributed to the synergistic effects of the PC solvent and the Cs(+) additive. The synergistic effects of Cs(+) additive and appropriate amount of PC enable the formation of a robust, ultrathin, and compact solid electrolyte interphase (SEI) layer on the surface of graphite electrode, which is only permeable for desolvated Li(+) ions and allows fast Li(+) ion transport through it. Therefore, this SEI layer effectively suppresses the PC cointercalation and largely alleviates the Li dendrite formation on graphite electrode during lithiation even at relatively high current densities. The presence of low-melting-point PC solvent improves the sustainable operation of graphite∥NCA full cells under a wide temperature range. The fundamental findings also shed light on the importance of manipulating/maintaining the electrode/electrolyte interphasial stability in various energy-storage devices.

NMR study of the polyethylene glycol diacrylate-LiBF4-1-butyl-3-methylimidazolium tetrafluoroborate-propylene/ethylene carbonate electrolyte system

The 1-butyl-3-methylimidazolium tetrafluoroborate-propylene carbonate-ethylene carbonate system in a reticular polymer electrolyte based on polyethylene glycol diacrylate and LiBF4 was studied by high-resolution and pulsed field gradient NMR. The 1H, 13C, 7Li, and 19F NMR spectra of the electrolyte systems were analyzed. During the electrolyte synthesis, propylene undergoes structural changes in the ionic liquid, which adversely affects the ion conductivity (the maximum conductivity in this system is 8.46 × 10−4 S/cm at 20°C) and the self-diffusion coefficients of the lithium ions. When the propylene carbonate content in the polymer electrolyte increased from 15 to 32 wt %, the proportion of lithium ions with a high self-diffusion coefficient (10−11 m2/s) decreased from 24 to 7%. In the case of ethylene carbonate, this effect was less pronounced, the conductivity in these systems reaching 2.46 × 10−3 S/cm at 20°C. The high-resolution NMR study did not reveal any structural changes in the ionic liquid and ethylene carbonate during the modeling of radical polymerization.

Ionic conductivity and dielectric permittivity of PEO-LiClO4 solid polymer electrolyte plasticized with propylene carbonate

We have studied ionic conductivity and dielectric permittivity of PEO-LiClO4 solid polymer electrolyte plasticized with propylene carbonate. Differential scanning calorimetry and X-ray diffraction studies confirm minimum volume fraction of crystalline phase for the polymer electrolyte with 40 wt. % propylene carbonate. The ionic conductivity exhibits a maximum for the same composition. The temperature dependence of the ionic conductivity has been well interpreted using Vogel-Tamman-Fulcher equation. Ion-ion interactions in the polymer electrolytes have been studied using Raman spectra and the concentrations of free ions, ion-pairs and ion-aggregates have been determined. The ionic conductivity increases due to the increase of free ions with the increase of propylene carbonate content. But for higher content of propylene carbonate, the ionic conductivity decreases due to the increase of concentrations of ion-pairs and ion-aggregates. To get further insights into the ion dynamics, the experimental data for the complex dielectric permittivity have been studied using Havriliak–Negami function. The variation of relaxation time with temperature obtained from this formalism follows Vogel-Tamman-Fulcher equation similar to the ionic conductivity.

A polymerized vinylene carbonate anode binder enhances performance of lithium-ion batteries

We investigated the use of polymerized vinylene carbonate (polyVC) as a binder for graphite anodes in lithium-ion cells. It functions not only of a traditional binder, but also plays an important role in surface stabilization of graphite in propylene carbonate (PC)-based electrolytes. In an electrolyte with PC content as high as 30 wt%, the polyVC binder enhanced battery performance, with a reversible capacity of ∼170 mAh g−1 at a delithiation rate of 1 C, whereas a comparable graphite cell fabricated with a polyvinylidene fluoride (PVDF) binder failed to cycle.

Conductivity Study on PEO Based Polymer Electrolytes Containing Hexafluorophosphate Anion: Effect of Plasticizer

AbstractPEO based polymer electrolytes containing ammonium hexafluorophosphate (NH4PF6) and hexafluorophosphoric acid (HPF6), both with PF anion have been studied. The effect of the addition of propylene carbonate (PC) to PEO‐NH4PF6 and PEO‐HPF6 has been observed to increase in ionic conductivity which is attributed to an increase in free ion concentration due to the dissociation of ion aggregates present at higher acid/salt concentrations. The plasticized polymer electrolytes containing HPF6 show relatively higher conductivity (σmax = 1.02 × 10−4 S/cm at 10 wt% HPF6) as compared to electrolytes containing NH4PF6 (σmax = 1.09 × 10−5 S/cm at 10 wt% NH4PF6). Presence of free ions, ion aggregates and their dissociation with the addition of PC has been studied by Fourier Transform Infrared Spectroscopy (FTIR). The change in amorphous phase with PC content was also studied by X‐Ray Diffraction (XRD). The variation of conductivity with temperature shows Vogel–Tammen–Fulcher (VTF) behavior, which is associated with the highly amorphous nature of electrolytes. 1H Nuclear magnetic Resonance (NMR) spectra at different temperatures shows line narrowing and suggests the onset of long range ion diffusional motion. Change in surface morphology of polymer electrolytes with the addition of PC is also checked by Scanning Electron Microscopic (SEM) studies.

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.

Structural Investigation of Polyurethane Based Gel Polymer Electrolytes Using Small Angle X-ray Scattering (SAXS)

Cross linked polymers PU (polyurethane) gel electrolytes have been synthesized from polyethylene oxide triol (PEO triol) and 4,4-methylenediphenyl diisocyanate (MDI). The minimum and maximum intake of liquid electrolyte by this gel is 35 and 65 wt % respectively. WAXD patterns for PU gel electrolytes shows featureless behaviour indicating absence of crystalline phase. SAXS pattern of polyurethane gel exhibits a broad peak at lower q value (∼0.7 nm -1 ) that is attributed to the presence of two phases, namely hard domains and soft domains. The structure of the gel was inferred as a continuous soft phase with dispersed hard domains. The shape and interface of the hard domains were determined from the slope of the curve in log ( I ( q )) versus log ( q ) plot. The slope of the curve decreases with increase in propylene carbonate (PC) content. The decrease in slope from -1.5 to -0.2 suggest that the shape of the hard domains changed from diffused ellipsoidal to the diffused spherical when the PC content was increased from 35 to 60 wt % in gels. PU-PC(60 wt %) gel electrolyte shows the maximum conductivity 2.53 ×10 -3 S/cm at room temperature.

Novel in situ preparation of crosslinked ethylene-vinyl alcohol copolymer foams with propylene carbonate

A novel in situ crosslinking and foaming process for ethylene-vinyl alcohol copolymers (EVOH) by propylene carbonate was investigated. The crosslinking process was believed to result from the ester-exchange reaction between propylene carbonate and EVOH, during which the 1, 2-propanediol by-product subsequently acts as the foaming agent for the crosslinked EVOH. The effects of propylene carbonate content, foaming condition, nucleating agent as well as plasticizer on the expansion ratio, morphology, and mechanical properties of the crosslinked EVOH foams were explored. Propylene carbonate not only acted as both crosslinking agent and foaming agent but also worked as plasticizer for the EVOH foams. The addition of nucleating agent or plasticizer led to foams with higher cell density and smaller cell size. Gel content, crystallization behavior, and thermal stability of the crosslinked EVOH foams were determined. The results revealed that the gel content and decomposition temperature increased with increasing propylene carbonate content, while the melting point, crystallization temperature and crystallinity decreased.

Novel in situ crosslinking reaction of ethylene-vinyl alcohol copolymers by propylene carbonate

The gel content, crystallization and melting behavior, tensile strength, and thermal stability of crosslinked ethylene–vinyl alcohol copolymer (EVOH) with propylene carbonate were investigated using modulated differential scanning calorimetry (MDSC), tensile tester, differential thermal analysis/thermal gravimetric analysis (DTA/TGA), respectively. The crosslinking process was believed to be resulted from the ester-exchange reaction between propylene carbonate and EVOH. Increasing propylene carbonate content resulted in the increase of gel content and tensile strength of crosslinked EVOH, and the decrease of elongation at break. However, increasing propylene carbonate content decreased the melting temperature, crystallization temperature, and crystallinity. The resulting crosslinked EVOH exhibited a higher thermal decomposition temperature than neat EVOH.

Polymer electrolytes derived from polynorbornenes with pendent cyclophosphazenes: poly(ethylene glycol) methyl ether (PEGME) derivatives

A novel elastomeric polymer electrolyte was developed by the linkage of poly(ethylene glycol) methyl ether (PEGME) side chains and norbornene-based units to a cyclotriphosphazene ring, followed by polymerization of the norbornene units by ring-opening metathesis polymerization (ROMP). This yielded an organic polymer backbone with ion co-ordinative cyclic phosphazene side groups. Adjustment of the norbornene content in the starting monomer allowed the degree of branching and cross-linking to be controlled and, in turn, the mechanical properties of the material to be tuned. The polymers were complexed with fixed molar ratios of LiN(SO 2CF 3) 2 and LiSO 3CF 3 and examined as solid polymer electrolytes. Polymer gel electrolytes were then formulated by the addition of variable amounts of propylene carbonate to the polynorbornenes. Films of solvent-free and solvent-containing polymers were homogeneous, flexible and self-standing materials. The ionic conductivities of the solvent-free polymers were in the range of 4×10 −5 S/cm at 30°C in the presence of 40 mol% of LiSO 3CF 3 or LiN(SO 2CF 3) 2. The conductivities of the solvent-containing (gel) systems increased with increases in the propylene carbonate content to a value of 2×10 −3 S/cm at 30°C in the presence of 50 wt.% of propylene carbonate and with the use of LiN(SO 2CF 3) 2 at a constant O:Li + ratio of 8:1. Even with this high concentration of propylene carbonate, the electrolyte was a solid elastomer rather than a viscous liquid. In general, the conductivities are twice as high with the use of LiN(SO 2CF 3) 2 compared to LiSO 3CF 3. The T g values were determined by DSC analysis, and these decreased with increased amounts of propylene carbonate in the system.

Physical Properties of $LiPF_6/PC+EC+DEC$ Electrolyte by the Variation of PC Fraction and Initial Electrochemical Properties of Carbon Anode in the Electrolyte

The exfoliation of graphite (layer) was progressed due to the irreversible insertion of PC molecules between graphene layers, when propylene carbonate (PC) solvent was used as the organic solvents. The problem could be mitigated by the replacement of PC by ethylene carbonate (EC). But, the freezing point of EC-based electrolyte increased due to the high freezing point of . Therefore, EC+PC mixed electrolyte is expected as a good organic electrolyte for lithium ion battery. The EC-based organic electrolyte containing PC within pertinent quantity can be expected to have high molar conductivity and reduced exfoliation of graphite layer. The dielectric constant and molar conductivity of electrolyte was investigated with a variation in the PC content. The electrochemical properties of carbon electrode in the electrolyte were also investigated. Molar conductivity and dielectric constant increased linearly by increasing the PC volume fraction in the electrolyte. The results of charge-discharge test for carbon/electrolyte/Li cell indicated that the initial irreversible specific capacity(IIC) of MCMB-6-28s and MPCF3000 decreased by the addition of of PC, but increased with PC content over than . In the case of MPCF3000 and PCG100 having less than PC, IIC was lower than 50 mAh/g. The discharge specific capacities varied with carbon material, but did not vary with PC content in the electrolyte.