The polymer electrolytes composed of a blend of poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) as a host polymer, mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and LiClO4 as a salt were prepared by a solution casting technique. SEM micrographs show that P(VDF-HFP) is very compatible with PEO. The ionic conductivity of the electrolytes increases with increasing plasticizer content, while the mechanical properties become obviously worse. By addition of a certain content of PEO in P(VDF-HFP) matrix, a good compromise between high ionic conductivity and mechanical stability can be obtained. 相似文献
Fresh silica gels have been used as hosts for liquid organic lithium electrolytes. The residual liquid inside the fresh gels was exchanged by the solutions of selected lithium salts (lithium hexafluorophosphate, lithium tetrafluoroborate) in organic solvents: propylene carbonate (PC), dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), 1,2-diethoxyethane (DEE) and dimethyl carbonate (DMC). The immersion of the gels in solutions based on DEE, DMF and DMC leads to the fast deterioration of the gels. The gels immersed in the solutions based on PC and DMSO exhibit stable conductivities in the range of 10–3Scm–1 at room temperature. That conductivity is close to the conductivity of the corresponding lithium salt solutions. 相似文献
The effects of room-temperature molten salt addition on the micro-structure and electrochemical properties of composite electrolytes (CEs) based on poly(ethylene oxide) (PEO)/ethylene carbonate (EC)/LiBF4 were studied. Additional salt, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4), was found to influence the crystalline structure and heterogeneous morphology, resulting in changes to the ionic conductivity of the CE. The CE containing 0.2 mol of EMIBF4 showed a small crystallinity, 27.9%. These CEs showed the highest ion conductivity, 3.1 × 10−4 S/cm, five times higher than that of the pristine PEO/EC/LiBF4. This enhanced conductivity originated from the decreased crystallinity and improved ion transference due to a Lewis acid-base interaction. The CE containing 0.3 mol of EMIBF4 showed decreased conductivity due to the lower mobility, reflecting the high viscosity of the molten salt. 相似文献
Difluoro(oxalato)borate (ODFB−) is a less symmetric borate anion, which makes it possible to increase the solubility of tetraethylammonium (TEA+) salt in propylene carbonate (PC) and improve the capacitance of electrochemical double-layer capacitors (EDLCs). The use of TEAODFB with PC solvent in EDLCs was investigated in the paper. The results show that TEAODFB has good solubility in PC, and the conductivity is comparable to TEABF4/PC electrolyte. When the molar concentration of TEAODFB reaches to 1.6 M, the TEAODFB/PC electrolyte has superior conductivity of 14.46 mS cm−1 and good capacitor characteristics. Despite the less accessible to the electrode and low energy density was achieved, the specific capacitance of 1.6 M TEAODFB/PC electrolyte is 21.4 F g−1 at 1 A g−1, and the energy density and power density were comparable to 1 M TEABF4/PC electrolyte at 1–5 A g−1. Temperature characteristic was also tested by 3.3 F circular capacitors from −40 to 60 °C, the result demonstrates that capacitors using 1.6 M TEAODFB/PC electrolyte show much higher capacitance and energy density at the investigated temperatures, and the discharge capacitance of capacitors using 1.6 M TEAODFB/PC electrolyte varies with the temperature less than that of 1 M TEABF4/PC electrolyte. 相似文献
The effect of alumina additives bearing various surface groups on conductivity and lithium cation transference numbers in poly(ethylene oxide) dimethyl ether (PEO-DME)-LiClO4 electrolytes is examined. It is demonstrated that an increase in the conductivity and lithium transference number in composite electrolytes compared to pure PEO-DME-LiClO4 electrolyte is observed in the limited salt concentration range. Both quantities seem to depend mostly on ionic species mobility. Also, their salt concentration dependence resembles that of viscosity of electrolytes studied. The conduction mechanism is discussed on the basis of conductivity, transference numbers and ionic association studies. 相似文献
Summary: Highly porous poly[(vinylidene fluoride)‐co‐hexafluoropropylene] (PVdF‐HFP)/TiO2 membranes were prepared by a phase inversion technique, using dimethyl acetamide (DMAc) as a solvent and water as a non‐solvent. Their physical and electrochemical properties were then characterized in terms of thermal and crystalline behavior, as well as ionic conductivity after absorbing an electrolyte solution of 1 M LiPF6 dissolved in an equal weight mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). For comparison, cast films and their electrolytes were also made by a conventional casting method without using the water non‐solvent. In contrast to the case of using N‐methyl‐2‐pyrrolidone (NMP) as a solvent, the PVdF‐HFP/TiO2 composite electrolytes, obtained using DMAc, exhibited superior properties of electrochemical stability and interfacial resistance with a lithium electrode but had lower ionic conductivities. It was also demonstrated that the phase inversion membrane was more effective than the cast film as the polymer electrolyte of a lithium rechargeable battery. As a result, a phase inversion membrane with 50 wt.‐% TiO2 was demonstrated to be the optimal choice for application in a lithium rechargeable battery.
Time evolutions of interfacial resistance between polymer electrolyte and lithium electrodes. 相似文献
The synthesis of dimethyl carbonate by oxidative carbonylation of methanol using Cu salt catalysts in the presence of various room temperature ionic liquids (RTILs) was reported. Among the ionic liquids used, N-butylpyridinium tetrafluoroborate was the most effective promoter in terms of the conversion of methanol and the selectivity to dimethyl carbonate (DMC). The influences of reaction temperature, pressure, time, molar ratio of CO/O2, and amount of the ionic liquid on the oxidative carbonylation of methanol were investigated. The results indicated that under the reaction conditions of 120 °C and 2.4 MPa of a 2:1 mixture of CO and O2, 17.2% conversion of methanol, 97.8% selectivity of DMC and a DMC productivity of 4.6 g g−1 cat h−1 were achieved. The N-butylpyridinium tetrafluoroborate-meditated CuCl catalyst system could be reused at least five recycles with the same selectivity and a slight loss of catalytic activity due to loss of the catalyst during handling and transferring the reaction mixture. 相似文献
In the present study, ion conductivity, optical properties, and glass transition temperatures are characterized for polymer electrolytes composed of poly(ethyleneimine) (PEI), lithium bis(trifluoromethane)sulfonylimide (LiTFSI) salt, propylene carbonate (PC), and ethylene carbonate (EC). It was doped with nanoceramic particles in different ratio (0–15 wt.%) to see the effect of ceramic particles. The salt concentration was fixed as 1.04 mol.kg?1. Although valuable improvement in ion conductivity could not be achieved due to nano-Al2O3 fillers, ion conductivity results are placed between 10?2 and 10?4 S/cm. Differential scanning calorimetry (DSC) measurements and optical measurements of all electrolytes were performed between ?80 and 140 °C, in the wavelength range between 400 and 700 nm for sample with 80 μm thickness, respectively. The results showed that transmittance of electrolytes decreased monotonically for increasing Al2O3 contents. In particular, its transmittance value at 550 nm where human sight is at its greatest sensitivity went from 100% without nanoparticles to 50% for 15 wt% of Al2O3. 相似文献
The use of nonhalogenated electrolyte salts for electrochemical devices is very important from the point of view of safety and cost. We have investigated the physical and electrochemical properties of a series of quaternary ammonium bis(oxalato)borates (QABOBs) and the performance of electric double-layer capacitors (EDLCs). The mass and van der Waals volume of BOB− are higher and larger than those of BF4−. The mass densities, viscosities, and surface tensions of propylene carbonate (PC) solutions containing the QABOBs are higher than those obtained for tetraethylammonium tetrafluoroborate (TEABF4), and the electric conductivities become lower. However, the electrochemical voltage windows measured with an activated carbon electrode and the gravimetric capacitances of 2025-type coin cells are comparable to those obtained for the PC solutions containing the TEABF4. 相似文献
For lithium salts, ionic liquids (ILs) are promising alternatives to conventional solvents in lithium-ion batteries (LIBs) due to a more favorable high-voltage operating window, and due to improved safety through reduction of flammability. Toward better understanding of wetting properties of IL-based electrolytes on a LIB separator, wetting properties affect electrochemical performance, experimental studies were made to determine the influence of solvent, lithium-salt type and salt concentration. Surface tensions and advancing contact angles were measured for two pure ILs ([C4C1im][BF4] and [C4C1im][OTf]) and for four IL/alkylcarbonate solvent blends (1:1 mass ratio, [C4C1im][BF4]/PC, [C4C1im][BF4]/DMC, [C4C1im][OTf]/PC, and [C4C1im][OTf]/ DMC) with several concentrations of a lithium salt (LiClO4, LiPF6, and LiTFSI). A significant improvement of wettability of pure ILs was observed by adding DMC, while adding PC with surface tension higher than that of pure ILs is detrimental to wetting behavior. Contact angles decrease by adding LiTFSI but show almost no change upon addition of LiPF6 or LiClO4. Surface tensions follow the same trend as that for contact angles. Incorporation of TFSI− anion gives favorable separator wettability. Estimates were made for interfacial properties of the separator (dispersive and polar components of the surface free energy for solid-vapor, for liquid–vapor, and for solid–liquid interfacial free energy). 相似文献
In this study, a strategy for synthesizing lithium methacrylate (LiMA)-based self-doped gel polymer electrolytes was described and the electrochemical properties were investigated by impedance spectroscopy and linear sweep voltammetry. LiMA was found to dissolve in ethylene carbonate (EC)/diethyl carbonate (DEC) (3/7, v/v) solvent after complexing with boron trifluoride (BF3). This was achieved by lowering the ionic interactions between the methacrylic anion and lithium cation. As a result, gel polymer electrolytes consisting of BF3-LiMA complexes and poly(ethylene glycol) diacrylate were successfully synthesized by radical polymerization in an EC/DEC liquid electrolyte. The FT-IR and AC impedance measurements revealed that the incorporation of BF3 into the gel polymer electrolytes increases the solubility of LiMA and the ionic conductivity by enhancing the ion disassociations. Despite the self-doped nature of the LiMA salt, an ionic conductivity value of 3.0 × 10−5 S cm−1 was achieved at 25 °C in the gel polymer electrolyte with 49 wt% of polymer content. Furthermore, linear sweep voltammetry measurements showed that the electrochemical stability of the gel polymer electrolyte was around 5.0 V at 25 °C. 相似文献
Polymer nanocomposite gel electrolytes consisting of high molecular weight poly(methyl methacrylate) PMMA-clay nanocomposite, ethylene carbonate (EC)/propylene carbonate (PC) as plasticizer, and LiClO4 electrolyte are reported. Montmorillonite clay was ion exchanged with a zwitterionic surfactant (octadecyl dimethyl betaine) and dispersed in methyl methacrylate, which was then polymerized to synthesize PMMA-clay nanocomposites. The nanocomposite was dissolved in a mixture of EC/PC with LiClO4, heated and pressed to obtain polymer gel electrolyte. X-ray diffraction (XRD) of the gels indicated intercalated clay structure with d-spacings of 2.85 and 1.40 nm. In the gel containing plasticizer, the clay galleries shrink suggesting intercalation rather than partial exfoliation observed in the PMMA-clay nanocomposite. Ionic conductivity varied slightly and exhibited a maximum value of 8 × 10−4 S/cm at clay content of 1.5 wt.%. The activation energy was determined by modeling the conductivity with a Vogel-Tamman-Fulcher expression. The clay layers are primarily trapped inside the polymer matrix. Consequently, the polymer does not interact significantly with LiClO4 electrolyte as shown by FTIR. The presence of the clay increased the glass transition temperature (Tg) of the gel as determined by differential scanning calorimetry. The PMMA nanocomposite gel electrolyte shows a stable lithium interfacial resistance over time, which is a key factor for use in electrochemical applications. 相似文献
Electrolytic characteristics of propylene carbonate (PC)ethylene carbonate (EC) mixed electrolytes were studied, compared with those in PC electrolytes. Conductivity and Li charge—discharge efficiency values increased with EC contents increasing. For example, 1 M LiClO4ECPC (EC mixing molar ratio; [EC]/[PC] = 4) showed the conductivity of 8.5 ohm?1 cm?1, which value was 40% higher than that in PC. Also, 1 M LiClO4ECPC([EC]/[PC] = 5) showed the Li charge—discharge efficiency of 90.5% at 0.5 mA cm?2, 0.6 C cm?2, which value was ca. 25% higher than that in PC. ECPC mixed electrolytes were considered to be practically available for ambient lithium batteries in regard to the high Li+ ion conductivity and also high Li charge—discharge efficiency. 相似文献
Gel polymer electrolytes composed of poly(vinylidene fluoride-hexafluoropropylene) copolymer, poly(vinylidene fluoride) polymer, PC+DEC as plasticizer and LiClO4 as salt have been synthesized by solvent casting technique with varying the plasticizer-salt concentration ratio systematically. Complex impedance spectroscopy has been carried out to investigate ionic conduction in P(VDF-HFP)-(PC+DEC)-LiClO4 and PVDF-(PC+DEC)-LiClO4 electrolyte systems. Transport number measurements have been made by Wagner’s polarization technique. With all other parameters same, P(VDF-HFP) electrolytes exhibit higher ionic conductivity and transport number as compared to PVDF based electrolytes which could be attributed to higher degree of amorphicity in the P(VDF-HFP) system. XRD and FTIR studies have been conducted to investigate the structural and complexation in the polymer gel electrolytes. Microstructural studies by SEM exhibit higher amorphicity and solvent retention capability for P(VDF-HFP)-(PC+DEC)-LiClO4 system than those of PVDF-(PC+DEC)-LiClO4 system. 相似文献
Hyperbranched network-based gel copolymer electrolytes are synthesized by in situ free radical polymerization. This research is separated into two parts: the first is an investigation of modified bismaleimide oligomer (MBMI) as a free volume additive, and the second investigates the salt concentration effect on high power application. A polymer electrolyte with MBMI additive provided more free volume space, and the ionic conductivity of gel copolymer electrolytes was measured as a function of the salt concentration of lithium hexafluorophosphate (LiPF6). The highest ionic conductivity and the lowest activation energy of hyperbranched-network gel copolymer electrolytes were determined to be 7.72 × 10−3 S/cm at 23 °C and 5.41 kJ/mol, respectively. Furthermore, the MBMI additive and the optimal concentration of lithium salt increased the free space for carrier ions and contributed to increasing capacity and working voltage at a high rate discharge (8C). The reliability and cycling ability of lithium polymer batteries are as good as lithium ion batteries for potential electric vehicle (EV) application. 相似文献