A novel PEO-based composite polymer electrolyte with absorptive glass mat for Li-ion batteries

A novel PEO (polyethylene oxide)-based composite polymer electrolyte (CPE) using absorptive glass mat (AGM) as filler was prepared and characterized. Scanning electronic micrograph (SEM) images showed that the addition of Li salt and modified AGM may improve the surface morphology of CPE. The results of Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeters (DSC) indicated that the inclusion of LiClO₄ salt and the addition of AGM filler can reduce the crystallinity of PEO. It was concluded that the addition of AGM plays two roles in PEO-based CPEs, namely, interruption of the PEO recrystallization and reinforcement of CPEs, accordingly enhancing room temperature ionic conductivity of CPEs and improving its mechanical strength and electrochemical stability at high temperatures.     

Preparation and ionic conductivity of solid polymer electrolyte based on polyacrylonitrile‐polyethylene oxide

The transparent and flexible solid polymer electrolytes (SPEs) were fabricated from polyacrylonitrile‐polyethylene oxide (PAN‐PEO) copolymer which was synthesized by methacrylate‐headed PEO macromonomer and acrylonitrile. The formation of copolymer is confirmed by Fourier‐transform infrared spectroscopy (FTIR) measurements. The ionic conductivity was measured by alternating current (AC) impedance spectroscopy. Ionic conductivity of PAN‐PEO‐LiClO₄ complexes was investigated with various salt concentration, temperatures and molecular weight of PEO (Mn). And the maximum ionic conductivity at room temperature was measured to be 3.54 × 10^?4 S/cm with an [Li⁺]/[EO] mole ratio of about 0.1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 461–464, 2006     

Physicochemical properties of poly(ethylene oxide)-based composite polymer electrolytes with a silane-modified mesoporous silica SBA-15

Mesoporous silica SBA-15 was surface-modified by γ-glycidoxypropyltrimethoxy silane (GPTMS), and novel poly(ethylene oxide) (PEO)-based composite polymer electrolytes (CPE) using the silane-modified SBA-15 (SBA-15-GPTMS) as filler were prepared and characterized. The results of the low-angle X-ray diffraction (XRD) patterns and Fourier-transform infrared (FT-IR) spectroscopy indicated that GPTMS has been successfully attached to the surface of SBA-15 with a high degree of mesoscopic hexagonal pore structure. The incorporation of SBA-15-GPTMS in the PEO-LiClO₄ matrix effectively reduced the PEO crystallinity and obviously improved the conductivity and electrochemical stability of the CPEs. The CPE with 10 wt.% SBA-15-GPTMS provided the highest conductivity among all the tested CPEs, about 2-3 orders of magnitude higher than that of the PEO-LiClO₄ matrix below the melting temperature of PEO. The reasons that the CPEs using SBA-15-GPTMS as filler showed higher conductivity than that with SBA-15 were discussed.     

Li NMR spectroscopy and ion conduction mechanism of composite gel polymer electrolyte: A comparative study with variation of salt and plasticizer with filler

Microporous composite gel polymer electrolyte (CGPE) has been prepared by incorporating the home-made silica aerogel (SAG) particles into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) copolymer/LiClO₄ matrix. The ionic transport behavior of the electrolyte is studied with various experimental techniques such as AC impedance, X-ray diffraction (XRD), infrared (IR) spectra, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA), etc. The results reveal that the SAG particles are well dispersed in the electrolytes and incorporate with the other components of the CGPEs. The solid-state ⁷Li NMR study has confirmed the interactions of lithium ion with SAG, polymer and plasticizers, causing to form the microporous structure and reduce the glass transition temperature and crystallinity, resulting in an increase in ionic conductivity of the CGPE. The best ionic conductivity (1.04 × 10⁻² S/cm at room temperature) is obtained from the composite polymer electrolyte containing 4 wt% of SAG, which is approximately four times higher than the ionic conductivity of the electrolyte without the filler.     

Solid polymer electrolytes VIII: effect of LiClO4-doped level on the microstructure and ionic conductivity of a chemical-covalently polyether-siloxane hybrid electrolyte

A new hybrid polymer electrolyte system based on chemical-covalently polyether and siloxane phases is designed and prepared in the presence of lithium perchlorate (LiClO₄) which acted as both ionic source and the epoxide ring-opening catalyst. The effect of salt-doped level on the microstructure and ionic conductivity of these composite electrolytes were investigated by means of Fourier transform infra-red spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, a.c. impedance and multinuclear solid-state nuclear magnetic resonance measurements. DSC results indicate that the formation of transient cross-links between Li⁺ ions and the ether oxygens on complexation with LiClO₄ results in an increase in polyether segment T_g. However, the polyether segment T_g decreases at the highest salt concentration (5.0 mmol LiClO₄/g PEGDE), ascribing to the plasticizing effect. The behavior of ion transport is coupled with the segmental motions of polymer chains and also correlated with the interactions between ions and polymer host.     

Influences of Bentonite on conductivity of composite solid alkaline polymer electrolyte PVA-Bentonite-KOH-H2O

The influence of the dopant Bentonite, on the ionic conductivity of the PVA-KOH-H₂O alkaline solid polymer electrolyte (ASPE) is studied. The results show that the addition of Bentonite has both positive and negative effects on the ionic conductivity of ASPE. At lower KOH and H₂O contents, the addition of Bentonite can break the continuous ion conducting phase of the ASPE, and therefore decrease the ASPE conductivity. However, the addition of Bentonite can also increase the KOH content in PVA matrix. This greatly increases the conductivity of the ASPE especially at higher water content. A highest ionic conductivity of 0.11 S cm⁻¹ is reached at room temperature. A maximum ionic conductivity value is observed at relative lower water content for different amount of Bentonite-doped ASPE. The temperature dependence of the ionic conductivity is of the Arrhenius type. The ion transfer activation energy Ea, in the order of 4-6 kJ mol⁻¹, heavily depends on the Bentonite content. XRD and SEM tests show that PVA in the Bentonite-doped ASPE is of amorphous structure, and there are lots of interspaces in the composite ASPE inner structure. The composite electrolyte has good electrochemical stability window and good charged-discharge property in secondary Zn-Ni cells at low charge-discharge rate.     

Novel composite polymer electrolyte comprising poly(ethylene oxide) and triblock copolymer/mesostructured silica hybrid used for lithium polymer battery

Ordered mesoporous materials, due to its potential applications in catalysis, separation technologies, and nano-science have attracted much attention in the past few years. In this work, a novel PEO-based composite polymer electrolyte by using organic-inorganic hybrid EO₂₀PO₇₀EO₂₀ @ mesoporous silica (P123 @ SBA-15) as the filler has been developed. The interactions between P123 @ SBA-15 hybrid and PEO chains are studied by X-ray diffraction (XRD), differential scanning calorimeter (DSC), and FT-IR techniques. The effects of P123 @ SBA-15 on the electrochemical properties of the PEO-based electrolyte, such as ionic conductivity, lithium ion transference number are studied by electrochemical ac impedance spectroscopy and steady-state current method. The experiment results show that P123 @ SBA-15 can enhance the ionic conductivity and increase the lithium ion transference number of PEO-based electrolyte, which are induced by the special topology structure of P123 in P123 @ SBA-15 hybrid, at the same time. The excellent lithium transport properties and broad electrochemical stability window suggesting that PEO-LiClO₄/P123 @ SBA-15 composite polymer electrolyte can be used as candidate electrolyte materials for lithium polymer batteries.     

Study of a new polymer electrolyte poly(ethylene oxide): NaClO3 with several plasticizers for battery application

Sodium ion conducting thin film polymer electrolytes based on poly(ethylene oxide) (PEO) complexed with NaClO₃ were prepared by a solution‐casting method. Characterization by XRD, IR spectroscopy and AC conductivity has been carried out on these thin film electrolytes to analyse their properties. The conductivity studies show that the conductivity value of PEO:NaClO₃ complex increases with the increase in salt concentrations. Increase in conductivity was found in the electrolyte system by the addition of low molecular weight polymer poly(ethylene glycol) (PEG) and the organic solvents dimethylformamide (DMF) and propylene carbonate (PC). Using these electrolyte systems, cell parameters were measured from the discharge study with the application of load 100 kΩ at room temperature with common cell configuration Na|electrolyte|C:I₂:electrolyte. The open circuit voltage (OCV) ranges from 2.81 to 3.23 V and the short circuit current (SCC) ranges from 340 to 1180 µA. © 2001 Society of Chemical Industry     

Study of ionic conductivity and microstructure of a cross-linked polyurethane acrylate electrolyte

A cross-linked polyurethane acrylate (PUA) was synthesized by end capping 4,4′-methylene bis(cyclohexyl isocyanate), H₁₂MDI/poly-(ethylene glycol), PEG based prepolymer with hydroxy ethyl acrylate (HEA). Significant interactions of the Li⁺ ions with the soft and hard segments of the host polymer have been observed for the PUA complexed with lithium perchlorate (LiClO₄) by means of differential scanning calorimetry (DSC), Fourier transform infra-red (FTIR) spectroscopy, ⁷Li magic angle spinning (MAS) NMR measurements and thermogravimetric analysis (TGA). The ⁷Li MAS NMR investigation of the PUA indicates the presence of at least three distinct Li⁺ sites at lower temperature, which merge to a single one at higher temperature in similar line with uncross-linked polyurethane. The results of TGA, DSC and FTIR spectroscopy support the formation of different types of complexes by the interaction of the Li⁺ ions with different coordination sites of PUA. No detectable interactions could be observed between Li⁺ ions and groups in HEA. The DSC data indicates the formation of transient cross-links with the ether oxygens of the soft segment and mixing of soft and hard phases induced by the Li⁺ ions. In addition, a Vogel-Tamman-Fulcher (VTF) like temperature dependence of ionic conductivity implies coupling of the ion movement with the segmental motion of the polymer chains in the cross-linked environment. Predominant formation of contact ion pairs of LiClO₄ has been consistently observed through AC conductivity, DSC and NMR spectroscopic results. Swelling measurements of PUA with plasticizers reveal the improved dimensional stability for these cross-linked PUA in comparison with uncross-linked polyurethane.     

Improved photovoltage and performance by aminosilane-modified PEO/P(VDF-HFP) composite polymer electrolyte dye-sensitized solar cells

A PEO/P(VDF-HFP) composite polymer electrolyte was modified by different amounts of NH₂-end functional silane (3-amonopropyltriethoxysilane, APTS). Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were carried out to examine the configuration changes of the polymer electrolyte. The newly formed Si-O-Si network and interactions influenced the ionic conductivity of the APTS-modified polymer electrolyte and also enhanced the connection of the polymer electrolyte with the electrodes of the dye sensitized solar cells (DSSCs). The cyclic voltammograms and electrochemical impedance measurements indicated that the APTS deprotonated the TiO₂ photoanode surface and negatively changed the Fermi energy level and the conduction band edge to the vacuum level. This effectively reduced the interface recombination in the DSSC and improved the open circuit voltage. With moderate APTS content (0.1 M) modification, the DSSC exhibited a 58 mV improvement of photovoltage and an improved performance of 5.08% compared with 3.74% of the original DSSC.     

Synthesis and electrochemical characterization of PEO-based polymer electrolytes with room temperature ionic liquids

New gel polymer electrolytes containing 1-butyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide (BMPyTFSI) ionic liquid are prepared by solution casting method. Thermal and electrochemical properties have been determined for these gel polymer electrolytes. The addition of BMPyTFSI to the P(EO)₂₀LiTFSI electrolyte results in an increase of the ionic conductivity, and at high BMPyTFSI concentration (BMPy⁺/Li⁺ = 1.0), the ionic conductivity reaches the value of 6.9 × 10⁻⁴ S/cm at 40 °C. The lithium ion transference numbers obtained from polarization measurements at 40 °C were found to decrease as the amount of BMPyTFSI increased. However, the lithium ionic conductivity increased with the content of BMPyTFSI. The electrochemical stability and interfacial stability for these gel polymer electrolytes were significantly improved due to the incorporation of BMPyTFSI.     

Poly(acrylonitrile)-montmorillonite nanocomposites: Effects of the intercalation of the filler on the conductivity of composite polymer electrolytes

In this work, a series of composite polymer electrolytes (CPEs) basically constituted by polyacrylonitrile (PAN) and a clay, montmorillonite (Bentonite), as filler have been developed, in which the clay in its lithiated form was used both as prepared and intercalated with PAN .The effect of these two forms of nanoceramic active filler on the properties of the CPEs was analyzed. Results show that the ionic conductivity of the CPEs using as filler Bentonite-Li⁺-polyacrylonitrile nanocomposite is about one order of magnitude higher than that using Bentonite-Li⁺ under the same conditions. The effect of the concentration of the filler on the conductivity of the products is discussed.     

Crystallinity,thermal properties,morphology and conductivity of quaternary plasticized PEO‐based polymer electrolytes

Quaternary plasticized solid polymer electrolyte (SPE) films composed of poly(ethylene oxide), LiClO₄, Li_1.3Al_0.3Ti_1.7(PO₄)₃, and either ethylene carbonate or propylene carbonate as plasticizer (over a range of 10–40 wt%) were prepared by a solution‐cast technique. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) indicated that components such as LiClO₄ and Li_1.3Al_0.3Ti_1.7(PO₄)₃ and the plasticizers exerted important effects on the plasticized quaternary SPE systems. XRD analysis revealed the influence from each component on the crystalline phase. DSC results demonstrated the greater flexibility of the polymer chains, which favored ionic conduction. SEM examination revealed the smooth and homogeneous surface morphology of the plasticized polymer electrolyte films. EIS suggested that the temperature dependence of the films' ionic conductivity obeyed the Vogel–Tamman–Fulcher (VTF) relation, and that the segmental movement of the polymer chains was closely related to ionic conduction with increasing temperature. The pre‐exponential factor and pseudo activation energy both increased with increasing plasticizer content and were maximized at 40 wt% plasticizer content. The charge transport in all polymer electrolyte films was predominantly reliant on lithium ions. All transference numbers were less than 0.5. Copyright © 2006 Society of Chemical Industry     

Ion-conductive properties of mesoporous silica-filled composite polymer electrolytes

We have synthesized mesoporous silica (MPSi) as a novel type of inorganic filler for polyether-based electrolytes and have characterized the effect of addition on ionic conduction. Both poly(ethylene oxide) (PEO) and PMEO composites filled with MPSi showed higher ionic conductivity than the original and the composites filled with particle silica (pSiO₂). It was considered that the increase is caused by the difference in the surface area between MPSi and pSiO₂. In the PEO composites, the addition of MPSi gave rise to the reduction of crystal PEO and crystalline complex domains. The glass transition temperature of the PMEO composites increased with the addition of the MPSi, in spite that the conductivity increased with increasing the filler contents. It has been suggested that the Lewis acid-base interactions between ions, ether chains and filler surface strongly affect on the ionic conduction in the composite electrolytes.     

Enhanced high-temperature polymer electrolyte membrane for fuel cells based on polybenzimidazole and ionic liquids

Polybenzimidazole (PBI)/ionic liquid (IL) composite membranes were prepared from an organosoluble, fluorine-containing PBI with ionic liquid, 1-hexyl-3-methylimidazolium tri?uoromethanesulfonate (HMI-Tf). PBI/HMI-Tf composite membranes with different HMI-Tf concentrations have been prepared. The ionic conductivity of the PBI/HMI-Tf composite membranes increased with both the temperature and the HMI-Tf content. The composite membranes achieve high ionic conductivity (1.6 × 10⁻² S/cm) at 250 °C under anhydrous conditions. Although the addition of HMI-Tf resulted in a slight decrease in the methanol barrier ability and mechanical properties of the PBI membranes, the PBI/HMI-Tf composite membranes have demonstrated high thermal stability up to 300 °C, which is attractive for high-temperature (>200 °C) polymer electrolyte membrane fuel cells.     

Ionic conductivities of solid polymer electrolyte/salt systems for lithium secondary battery

We establish a new ionic conductivity model based on the Nernst-Einstein equation in which the diffusion coefficient is derived from modified double lattice-nonrandom-Pitzer-Debye-Hückel (MDL-NR-PDH) model. The proposed model takes into account the mobility of the salt and the motion of the polymer host simultaneously by expressing the effective chemical potential as the sum of chemical potentials of the salt and the polymer. To describe the segmental motion of the polymer chain, which is the well-known conduction mechanism for solid polymer electrolyte (SPE) systems, the effective co-ordinated unit parameter is introduced. The obtained co-ordinated unit parameter for each state is used to describe the behavior of the ionic conductivities of the given systems. Good agreement is obtained upon comparison with experimental data of various PEO and salt systems in the interested ranges.     

Solid polymer electrolytes V: microstructure and ionic conductivity of epoxide-crosslinked polyether networks doped with LiClO4

A crosslinked polyether network was prepared from poly(ethylene glycol) diglycidyl ether (PEGDE) cured with poly(propylene oxide) polyamine. Significant interactions between ions and polymer host have been observed for the crosslinked polyether network in the presence of LiClO₄ by means of FT-IR, DSC, TGA, and ⁷Li MAS solid-state NMR. Thermal stability and ionic conductivity of these complexes were also investigated by TGA and AC impedance measurements. The results of FT-IR, DSC, TGA and ⁷Li MAS solid-state NMR measurements indicate the formation of different types of complexes through the interaction of ions with different coordination sites of polymer electrolyte networks. The dependence of ionic conductivity was investigated as a function of temperature, LiClO₄ concentration and the molecular weight of polyether curing agents. It is observed that the behavior of ion transport follows the empirical Vogel-Tamman-Fulcher (VTF) type relationship for all the samples, implying the diffusion of charge carrier is assisted by the segmental motions of polymer chains. Moreover, the conductivity is also correlated with the interactions between ions and polymer host, and the maximum ionic conductivity occurs at the LiClO₄ concentration of [O]/[Li⁺]=15.     

Ionic conductivity of PEO9: Cu(CF3SO3)2: Al2O3 nano-composite solid polymer electrolyte

Cu⁺⁺ ion containing solid polymer electrolytes exhibit interesting electrochemical properties. In particular, the polymer electrolyte PEO₉:Cu(CF₃SO₃)₂ made by complexing copper triflate (CuTf₂) with PEO appears to show scientifically intriguing transport properties. Although some copper ion transport in these systems has been seen from plating stripping processes, the detailed mechanism of ionic transport and the species involved are yet to be established. In order to obtain enhanced ionic conductivities and also to contribute towards understanding the ionic transport process in Cu⁺⁺ ion containing, PEO based composite polymer electrolytes, we have studied the system PEO₉: CuTf₂: Al₂O₃ incorporating 10 wt.% of alumina filler particles of grain size 10 μm, 37 nm, 10–20 nm and also particles of pore size 5.8 nm. Thermal and electrical measurements show that the system remains amorphous down to room temperature. The composite electrolyte is predominantly an ionic conductor with electronic conductivity less than 2%. The triflate (CF₃SO₃⁻) anions appear to be the dominant carriers. The presence of alumina grains has enhanced the conductivity significantly from room temperature up to 100 °C. The nano-porous grains with 5.8 nm pore size and 150 m²/g specific surface area exhibited the maximum conductivity enhancement. This enhancement has been attributed to Lewis acid–base type surface interactions of ionic species with O²⁻ and OH⁻ groups on the filler grain surface.     

Electrical conductivity of YSZ-SDC composite solid electrolyte synthesized via glycine-nitrate method

Yttria-stabilized zirconia (YSZ) is a common solid electrolyte for solid oxide fuel cells (SOFCs) because of its high electrical conductivity and high ionic transference number in both oxidizing and reducing atmospheres. Samarium doped ceria (SDC) has also been considered as an alternative electrolyte material to YSZ for intermediate temperature SOFC because of its high conductivity at relatively low temperatures. Due to improved ionic conductivity of YSZ at high temperature (~ 800 °C) and good conductivity of SDC in the intermediate temperature range (600–800 °C), the electrical properties of YSZ-SDC composites were investigated. Composites of YSZ and SDC with weight ratio 9.5:0.5, 9:1 and 8.5:1.5 were synthesized via glycine-nitrate route. XRD pattern of the systems revealed the formation of composite phases. Biphasic electrolyte microstructures were observed, in which SDC grains are dispersed in YSZ matrix. Relative density of the compositions was found to be more than 92% to the theoretical density. It was observed that the interface provides a channel for ionic transport, leading to a notable ionic conductivity. With increase in SDC weight ratio the electrical conductivity was found to increase. For weight ratio 8.5:1.5 the electrical conductivity was found to be greater than that of YSZ in the temperature range 400–700 °C. Further, for weight ratio more than 8.5:1.5, conductivity was found to decreases due to the formation of a few other insulating impurity phases. The electrode polarisation was also found to reduce significantly with SDC in the composite electrolyte system. Thus, such composite system may be useful for improving the ionic conductivity of the composite electrolytes.     

Study on performance of composite polymer films doped with modified molecular sieve for lithium-ion batteries

To improve the tensile strength and ionic conductivity of composite polymer films for lithium-ion batteries, molecular sieves of MCM-41 modified with sulfated zirconia (SO₄²⁻/ZrO₂, SZ), denoted as MCM-41/SZ, were doped into a poly(vinylidene fluoride) (PVdF) matrix to fabricate MCM-41/SZ composite polymer films, denoted as MCM-41/SZ films. Examination by transmission electron microscope (TEM) shows that modified molecular sieves have lower aggregation and a more porous structure. Tensile strength tests were carried out to investigate the mechanical performance of MCM-41/SZ films, and then the electrochemical performance of batteries with MCM-41/SZ films as separators was tested. The results show that the tensile strength (σ_t) of MCM-41/SZ film was up to 7.8 MPa; the ionic conductivity of MCM-41/SZ film was close to 10⁻³ S cm⁻¹ at room temperature; and the coulombic efficiency of the assembled lithium-ion battery was 92% at the first cycle and reached as high as 99.99% after the 20th cycle. Meanwhile, the charge-discharge voltage plateau of the lithium-ion battery presented a stable state. Therefore, MCM-41/SZ films are a good choice as separators for lithium-ion batteries due to their high tensile strength and ionic conductivity.