Single-ion-conducting nanocomposite polymer electrolytes based on PEG400 and anionic nanoparticles: Part 1. Synthesis,structure and properties

The synthesis and the properties of single-ion-conducting nanocomposite polymer electrolytes (nCPEs) are described. The nCPEs are obtained by doping polyethylene glycol 400 (PEG400) with different amounts of a fluorinated TiO₂-based nanofiller (LiFT^®) that is surface-functionalized with Li⁺ cations. Electrolytes with general formula [PEG400/(LiFT)_y] and y = n_Ti/n_PEG ranging from 0 to 26.4 are obtained. The materials are characterized by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Fourier-Transform Infrared Spectroscopy in both the medium (FT-MIR) and far infrared (FT-FIR). In the [PEG400/(LiFT)_y] electrolytes the concentration of LiFT nanofiller strongly affects the thermal stability and transitions of PEG400. In addition, vibrational measurements allow us to reveal the interactions occurring between: (a) different PEG400 chains; (b) PEG400 and Li⁺ cations; and (c) PEG400 and LiFT nanoparticles (NPs). On LiFT nanofiller concentration, results show three compositional regions in [PEG400/(LiFT)_y] electrolytes which are correlated to the presence of three different interaction environments between LiFT NPs and PEG400 chains.     

Electrical and electrochemical studies of poly(vinylidene fluoride)-clay nanocomposite gel polymer electrolytes for Li-ion batteries

A study is conducted on the electrical and electrochemical properties of nanocomposite polymer electrolytes based on intercalation of poly(vinylidene fluoride) (PVdF) polymer into the galleries of organically modified montmorillonite (MMT) clay. A solution intercalation technique is employed for nanocomposite formation with varying clay loading from 0 to 4 wt.%. X-ray diffraction results show the β phase formation of PVdF on intercalation. Transmission electron microscopy reveals the formation of partially exfoliated nanocomposites. The nanocomposites are soaked with 1 M LiClO₄ in a 1:1 (v/v) solution of propylene carbonate (PC) and diethyl carbonate (DEC) to obtain the required gel electrolytes. The structural conformation of the nanocomposite electrolytes is examined by Fourier transform infrared spectroscopy analysis. Examination with a.c. impedance spectroscopy reveals that the ionic conductivity of the nanocomposite gel polymer electrolytes increases with increase in clay loading and attains a maximum value of 2.3 × 10⁻³ S cm⁻¹ for a 4 wt.% clay loading at room temperature. The same composition exhibits enhancement in the electrochemical and interfacial properties as compared with that of a clay-free electrolyte system.     

锂电池用全固态聚合物电解质的研究进展

目前大规模商业化的锂二次电池普遍采用有机碳酸酯类的液态电解质,易泄露、易燃烧、易爆炸等安全问题限制了该类电解质的进一步应用。全固态聚合物电解质（all-solid-state polymer electrolytes,ASPEs）电池具有安全性能好、能量密度高、工作温度区间广、循环寿命长等优点,是锂离子电池领域的研究热点之一。ASPEs通常还具有优异的力学性能,可以很好地抑制锂金属电极在充放电过程中的枝晶生长,所以在锂金属电池领域也具有十分重要的应用前景。作者综述了研究较多的几种ASPEs体系,包括聚氧化乙烯（PEO）基体系、聚碳酸酯基体系、聚硅氧烷基体系、聚合物锂单离子导体体系。PEO基ASPEs是研究最早且研究最多的一类ASPEs材料,但其高结晶性造成室温Li+迁移困难、离子电导率低等问题,所以研究人员研发了一系列降低PEO结晶度、提升体系离子电导率的改性手段。聚碳酸酯基ASPEs主链结构中含有强极性碳酸酯基团而且室温无定形态,使得锂盐更容易解离,且室温离子电导率一般较PEO基要高,是比较有潜力的PEO基ASPEs替代材料。除了碳链聚合物,玻璃化转变温度较低的聚硅氧烷基ASPEs体系也因为其较高的离子电导率受到研究人员关注。在锂电池充放电过程中,Li+才是有效载荷子,电解质中阴离子的迁移会增加电解质体系的浓差极化,所以阴离子不发生迁移、Li+迁移数接近于1的聚合物锂单离子导体也是一类具有研究价值的ASPEs材料。最后,本综述讨论了全固态聚合物电解质的应用前景及未来发展方向,指出了PEO基体系的研究重点在于发展有机-无机复合体系、聚碳酸酯基体系的研究重点在于发展与其它聚合物的共混体系、聚硅氧烷基体系的研究重点在于增强体系力学性能、聚合物锂单离子导体体系的研究重点在于设计离子电导率更高的新型聚阴离子锂盐。     

Conductivity and characterization of plasticized polymer electrolyte based on (polyacrylonitrile-b-polyethylene glycol) copolymer

A block copolymer polyacrylonitrile-b-polyethylene glycol was synthesized by the macroinitiator method. The copolymer mixed with a plasticizer—propylene carbonate (PC) and LiClO₄ to form plasticized polymer electrolytes. FT-IR spectra show that the lithium ion interacts with the groups that contain the un-bonded electrons. The results of FT-IR also indicate that the EO segment can improve the dissociation of lithium salt. The differential scanning calorimeter (DSC) used to study the thermal behaviors of different compositions. In this study, the conductivity increases with the content of PEG. Additionally, the plasticized polymer electrolyte based on the block copolymer has a good conductivity and can retain good mechanical strength.     

Hybrid inorganic-organic nanocomposite polymer electrolytes based on Nafion and fluorinated TiO2 for PEMFCs

In this report, three hybrid inorganic-organic proton-conducting membranes based on a novel fluorinated titania labeled TiO₂F dispersed in Nafion were prepared. The mass fraction of TiO₂F nanofiller ranged between 0.05 and 0.15. The water uptake and the proton exchange capacity of the membranes were determined; the membranes were further characterized by TG, DMA and FT-IR ATR investigations. Finally, the hybrid membranes were used in the fabrication of membrane-electrode assemblies (MEAs), which were tested in operating conditions as a function of the back pressure and of the hydration degree of the reagents streams. It was demonstrated that, with respect to pristine recast Nafion, at 25%RH the MEA fabricated with the membrane including a mass fraction of TiO₂F equal to 0.10 yielded a higher maximum power density (0.206 W cm⁻² vs. 0.121 W cm⁻²). Finally, it was proposed a coherent structural model of this family of hybrid membranes accounting for both the properties determined from “ex-situ” characterizations and for the performance obtained from measurements in a single fuel cell in operating conditions.     

Synthesis and characterization of composite electrolytes based on samaria-doped ceria and Na/Li carbonates

Samaria-doped ceria-based composites with a 2:1 addition of Li and Na carbonates (or simple Na carbonate as admixture) were prepared mixing nanosized powders of the ceramic phase with the remaining constituents. Samples fired at relatively low temperatures (below 700 °C) were characterized by X-ray diffraction, scanning electron microscopy combined with energy dispersive spectroscopy and impedance spectroscopy in air. These composites showed a complex but homogeneous distribution of both phases, with one ceramic skeleton of bonded nanosized grains surrounded by the carbonate-based phase. Impedance spectroscopy data was used to confirm the impressive electrical conductivity of these materials, but also to put into evidence the complex nature of the charge transport process, clearly deviating from classical electrolytes.     

Iodide-conducting plastic crystals based on N,N-dimethyl-2-(methylsilyloxy) ethanaminium cations (MESEA) for application in dye-sensitized solar cells

This report describes the synthesis and the properties of twelve iodide-conducting Plastic Crystal Electrolytes (PCEs) based on N,N-dimethyl-2-(methylsilyloxy) ethanaminium cations (MESEAⁿ⁺) and I⁻/I₃⁻ anions for application in dye-sensitized solar cells (DSSCs).     

Novel proton exchange membranes based on proton conductive sulfonated PAMPS/PSSA-TiO2 hybrid nanoparticles and sulfonated poly (ether ether ketone) for PEMFC

Nanocomposite membranes based on sulfonated poly (ether ether ketone) (SPEEK) and sulfonated core-shell TiO₂ nanoparticles were prepared. TiO₂ nanoparticles were sulfonated by redox polymerization method by using sodium styrene sulfonate (SSA) and 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) monomers. The resultant hybrid nanoparticles (PAMPS-gTiO₂ and PSSA-g-TiO₂) were introduced to SPEEK with a sulfonation degree of 68%. Grafting of sulfonated polymers onto TiO₂ nanoparticles enhanced the content of proton transport sites in the membrane, leading to an increase in proton conductivity and power density. Besides, the mechanical and dimensional stabilities of the nanocomposite membranes were also improved compared with pure SPEEK membrane. The maximum power density for membranes containing 7.5 wt% of PAMPS-gTiO₂ and PSSA-g-TiO₂ nanoparticles at 80 °C obtained 283 mW cm⁻² and 245 mW cm⁻², respectively.     

Development and characterization of polymer electrolyte membranes based on ionical cross-linked poly(1-vinyl-1,2,4 triazole) and poly(vinylphosphonic acid)

The fabrication, thermal and proton conducting properties of complex polymer electrolytes based on poly(vinylphosphonic acid) (VPA) and poly(1-vinyl-1,2,4-triazole) (PVTri) were investigated throughout this work. The membrane materials were produced by complexation of PVPA with PVTri at various concentrations to get PVTriP(VPA)_x where x designates the molar ratio of the polymer repeating units and varied from 0.25 to 4. The complexed structure of the polymers was confirmed by FT-IR spectroscopy. The TGA results verified that the presence of PVTri in the complex polymer electrolytes suppressed the formation of phosphonic acid anhydrides up to 150 °C. The DSC and SEM results demonstrated the homogeneity of the materials. Proton conductivity, activation energy and water/methanol uptake of these membranes were also measured. PVTriP(VPA)₂ showed a proton conductivity of 2.5 × 10⁻⁵ S cm⁻¹ at 180 °C in the anhydrous state. After humidification (RH = 50%), PVTri-P(VPA)₄ and PVTri-P(VPA)₂ showed respective proton conductivities of 0.008 and 0.022 S cm⁻¹ at 100 °C, where the conductivity of the latter is close to Nafion 117 at the same humidity level.     

Preparation,characterization and properties of proton exchange nanocomposite membranes based on poly(vinyl alcohol) and poly(sulfonic acid)-grafted silica nanoparticles

Nanocomposite membranes based on the poly(vinyl alcohol) (PVA)/poly(sulfonic acid)-grafted silica nanoparticles (PSA-g-SN) were prepared via solvent casting of PVA cross linked by glutardialdehyde in the presence of various amounts (0–20 wt%) of silica nanoparticles (SN), poly(styrene sulfonic acid)- (PSSA-g-SN) and poly (2-acrylamido-2-methyl-1-propane sulfonic acid)-grafted silica nanoparticles (PAMPS-g-SN) as hydrophilic inorganic modifiers. PSA-g-SN nanoparticles were synthesized by surface-initiated redox grafting of SSA and AMPS monomers from the surface of the aminopropylated silica nanoparticles. Membranes were then characterized by FTIR, impedance spectroscopy, thermogravimetric analysis (TGA), water uptake, tensile strength test and SEM. The best proton conductivity was observed for membranes containing 5 wt% of nanoparticles. Among three nanoparticles used, the highest proton conductivity (10.4 mS/cm) was observed for PVA membrane prepared in the presence of 5 wt% PAMPS-g-SN nanoparticles. Results showed that grafting of sulfonated monomer onto the silica nanoparticles enhances various properties, for example proton conductivity, of the polymer electrolyte membranes (PEMs).     

Preparation and electrochemical characterization of polymer electrolytes based on electrospun poly(vinylidene fluoride-co-hexafluoropropylene)/polyacrylonitrile blend/composite membranes for lithium batteries

Apart from PEO based solid polymer electrolytes, tailor-made gel polymer electrolytes based on blend/composite membranes of poly(vinylidene fluoride-co-hexafluoropropylene) and polyacrylonitrile are prepared by electrospinning using 14 wt% polymer solution in dimethylformamide. The membranes show uniform morphology with an average fiber diameter of 320-490 nm, high porosity and electrolyte uptake. Polymer electrolytes are prepared by soaking the electrospun membranes in 1 M lithium hexafluorophosphate in ethylene carbonate/dimethyl carbonate. Temperature dependent ionic conductivity and their electrochemical performance are studied. The blend/composite polymer electrolytes show good ionic conductivity in the range of 10⁻³ S cm⁻¹ at ambient temperature and good electrochemical performance. All the Polymer electrolytes show an anodic stability >4.6 V with stable interfacial resistance with storage time. The prototype cell shows good charge-discharge properties and stable cycle performance with comparable capacity fade compared to liquid electrolyte under the test conditions.     

New inorganic-organic proton conducting membranes based on Nafion and hydrophobic fluoroalkylated silica nanoparticles

In this report, a new nanofiller consisting of silica “cores” bearing fluoroalkyl surface functionalities is synthesized and adopted in the preparation of a series of hybrid inorganic-organic proton conducting membranes based on Nafion. The hybrid materials are obtained by a solvent-casting procedure and include between 0 and 10 wt.% of nanofiller. The resulting systems are extensively characterized by Thermogravimetry (TG), Modulated Differential Scanning Calorimetry (MDSC) and Dynamic Mechanical Analysis (DMA), showing that the hybrid materials are stable up to 240 °C and that their overall thermal and mechanical properties are affected both by the polar groups on the surface of the silica “cores” and by the fluoroalkyl surface functionalities of the nanofiller. The electric properties of the hybrid materials are investigated by broadband dielectric spectroscopy (BDS). It is shown that proton conductivity of the materials is not compromised by the lower water uptake arising from the hydrophobic character of the nanofiller. With respect to a pristine Nafion recast membrane, the hybrid material characterized by 5 wt.% of nanofiller, [Nafion/(Si₈₀F)_0.7], shows the highest conductivity in all the investigated temperature range (5 ≤ T ≤ 155 °C). Indeed, [Nafion/(Si₈₀F)_0.7] features the lowest water uptake and presents a conductivity of 0.083 S cm⁻¹ at 135 °C. This result is consistent with the good performance of the membrane in single fuel cell tests.     

Novel nanocomposite membranes based on PBI and doped-perovskite nanoparticles as a strategy for improving PEMFC performance at high temperatures

In this work, Sr²⁺ dopant effects of Ba_0.9Sr_0.1TiO₃ and La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles on increasing proton conductivity, fuel cell performance, and mechanical and thermal stability of polybenzimidazole-based nanocomposite membranes were studied. The Sr²⁺ dopant creates cation vacancies in Ba_0.9Sr_0.1TiO₃ doped-perovskite nanoparticles and oxygen vacancies in La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles. The oxygen vacancies, which decrease columbic repulsion between protons and positive ions, have a more important role than the cation vacancies. They provide high surface area and high interfacial interaction between La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles, phosphoric acid, and polybenzimidazole for proton transfer and increase the proton conductivity of the nanocomposite membranes. In addition, the results of relative humidity effects showed that the ordered arrangement of oxygen vacancies of the La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles creates a specific pathway in the nanocomposite membranes for increasing proton transfer in the presence of relative humidity. Furtheremore, at phosphoric acid doping level of 13 mol phosphoric acid per monomer unit, proton conductivity of the nanocomposite membranes containing 8 wt.% La_0.9Sr_0.1CrO_3-δ doped-perovskite nanoparticles was obtained as 126 mS cm^-1 at 180°C and 6% relative humidity. The nanocomposite membrane showed the best performance and the power density of 0.62 W cm^-2 at 180°C and 0.5 V.     

A comparative study of gel polymer electrolytes based on PVDF-HFP and liquid electrolytes, containing imidazolinium ionic liquids of different carbon chain lengths in DSSCs

The photoelectrochemical characteristics of titanium dioxide (TiO₂)-based dye-sensitized solar cells (DSSCs) containing gel polymer electrolyte (GPE) and organic liquid electrolyte (OLE) were studied in detail. GPE was prepared by adding poly(vinyidene fluoride-co-hexafluoro propylene) (PVDF-HFP) to imidazolinium ionic liquids (IILs) of the type, 1-methyl-3-alkyl imidazolinium iodides (alkyl is C_nH_2n+1, where n=3–10) in methoxy propionitrile (MPN) and the OLE contained the above molten salt in MPN. The IILs were synthesized in the laboratory and characterized by ¹H nuclear magnetic resonance spectroscopy (NMR). The conductivities (σ) of both GPE and OLE decrease with increase in chain length (n) of the alkyl group of IILs; however, the effect is more drastic in the former case. The performance of the DSSCs containing OLE increases with the increase in alkyl chain length of IIL from C3 to C7, whereas, there is a linear decrease in the efficiency of the DSSCs incorporated with GPE containing IIL of alkyl chain length from C3 to C10. The change in short circuit current density (J_SC) determines the cell efficiency as the V_OC of the DSSCs remains almost the same with increase of alkyl chain length of IILs for both the electrolytes. The change in J_SC values and the consistency of the V_OC of the DSSCs for both the electrolytes may be explained on the basis of increase in viscosity of IILs from C3 to C10 and the dominating role of the 4-tertiary butyl pyridine (TBP), respectively, on the phenomenon of charge recombination.     

Magnetic field aligned nanocomposite proton exchange membranes based on sulfonated poly (ether sulfone) and Fe2O3 nanoparticles for direct methanol fuel cell application

Sulfonated poly (ether sulfone) (SP-ES) are prepared and optimized considering the transport properties and physicochemical stability. Afterward, nanocomposite membranes composed of SP-ES containing various loading weights of γ-Fe₂O₃ nanoparticles are fabricated. Nanoparticles assembled into an aligned form across the membrane by applying magnetic field during solvent casting. The effect of nanoparticles orientation is studied by consideration of the water uptake, membrane ionic conductivity, and activation energy as well as methanol permeability. Aligned membranes have a higher proton conductivity and also lower activation energy for proton migration as well as lower water uptake and methanol permeability. It is also noted that nanocomposite membranes have sufficient thermal stability and high electrochemical performance. Consequently, the anisotropic nanocomposite membranes with oriented nanoparticles demonstrate the ability to have potential application in fuel cells as well as ionic actuators.     

Highly conductive and electrochemically stable plasticized blend polymer electrolytes based on PVdF-HFP and triblock copolymer PPG-PEG-PPG diamine for Li-ion batteries

A new plasticized poly(vinylidene fluoride-co-hexafluoropropylene (PVdF-HFP)/PPG-PEG-PPG diamine/organosilane blend-based polymer electrolyte system has been synthesized and characterized. The structural and electrochemical properties of the electrolytes thus obtained were systematically investigated by a variety of techniques including differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile test, Fourier transform infrared spectroscopy (FTIR), ¹³C and ²⁹Si solid-state NMR, AC impedance, linear sweep voltammetry (LSV) and charge-discharge measurements. The FTIR and NMR results provided the information about the interaction among the constituents in the blend polymer membrane. The present blend polymer electrolyte exhibits several advantageous electrochemical properties such as ionic conductivity up to 1.3 × 10⁻² S cm⁻¹ at room temperature, high value of Li⁺ transference number (t₊ = 0.82), electrochemical stability up to 6.4 V vs. Li/Li⁺ with the platinum electrode, and stable charge-discharge cycles for lithium-ion batteries.     

Inorganic-organic polymer electrolytes based on poly(vinyl alcohol) and borane/poly(ethylene glycol) monomethyl ether for Li-ion batteries

In this study, poly(vinyl alcohol) (PVA) was modified with poly(ethylene glycol) monomethyl ether (PEGME) using borane-tetrahydrofuran (BH₃/THF) complex. Molecular weights of both PVA and PEGME were varied prior to reaction. Boron containing comb-branched copolymers were produced and abbreviated as PVA1PEGMEX and PVA2PEGMEX. Then polymer electrolytes were successfully prepared by doping of the host matrix with CF₃SO₃Li at several stoichiomeric ratios with respect to EO to Li. The materials were characterized via nuclear magnetic resonance (¹H NMR and ¹¹B NMR), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry (TG) and differential scanning calorimeter (DSC). The ionic conductivity of these novel polymer electrolytes were studied by dielectric-impedance spectroscopy. Li-ion conductivity of these polymer electrolytes depends on the length of the side units as well as the doping ratio. Such electrolytes possess satisfactory ambient temperature ionic conductivity (>10⁻⁴ S cm⁻¹). Cyclic voltammetry results illustrated that the electrochemical stability domain extends over 4 V.     

Preparation and electrochemical characterization of gel polymer electrolyte based on electrospun polyacrylonitrile nonwoven membranes for lithium batteries

Electrospun membranes of polyacrylonitrile are prepared, and the electrospinning parameters are optimized to get fibrous membranes with uniform bead-free morphology. The polymer solution of 16 wt.% in N,N-dimethylformamide at an applied voltage of 20 kV results in the nanofibrous membrane with average fiber diameter of 350 nm and narrow fiber diameter distribution. Gel polymer electrolytes are prepared by activating the nonwoven membranes with different liquid electrolytes. The nanometer level fiber diameter and fully interconnected pore structure of the host polymer membranes facilitate easy penetration of the liquid electrolyte. The gel polymer electrolytes show high electrolyte uptake (>390%) and high ionic conductivity (>2 × 10⁻³ S cm⁻¹). The cell fabricated with the gel polymer electrolytes shows good interfacial stability and oxidation stability >4.7 V. Prototype coin cells with gel polymer electrolytes based on a membrane activated with 1 M LiPF₆ in ethylene carbonate/dimethyl carbonate or propylene carbonate are evaluated for discharge capacity and cycle property in Li/LiFePO₄ cells at room temperature. The cells show remarkably good cycle performance with high initial discharge properties and low capacity fade under continuous cycling.     

The effect of receptor-polymer matrix compatibility on properties of PEO-based polymer electrolytes containing a supramolecular additive: Part 1. Studies on phenomenon of compatibility

This paper presents the results of studies of poly(ethylene oxide)-based solid polymer electrolyte with the addition of anion receptor. The main stress is put on the influence of the anion receptor-polymeric matrix compatibility on the morphology of the composite. The comparison of the properties of two supramolecular compounds (calix[4]arene derivatives) having identical groups active in anion coordination in the narrow rim but with wide rim modified by groups having structure non-compatible and compatible to poly(ethylene oxide), is analyzed. The research of the system is made by means of vibrational (both IR and Raman) spectroscopies to evaluate the anion receptor-polymer–salt interactions. Raman and EDS mapping are used to determine the local concentration of the additive and salt. DSC and XRD determine the membrane crystallinity. Imaging techniques (both SEM and polarized light micrographs) allow to observe the morphology of membrane surface. The presented results show that additive distribution depends on the type of the receptor used and the phase of the polymer matrix (amorphous or crystalline).     

Organic–inorganic hybrid solar cells based on conducting polymer and SnO2 nanoparticles chemically modified with a fullerene derivative

Organic–inorganic hybrid solid solar cells were fabricated by using a conjugated polymer (MDMO-PPV) and SnO₂ nanoparticles chemically modified with C₆₀C(COOH)₂. The cell performance was improved by the chemical modification, suggesting that the modification with photoelectrochemically active organic materials is useful for establishing good electronic junction at the organic–inorganic interface. The short-circuit current density J_SC increased with increasing thickness of MDMO-PPV up to 40 nm, and then decreased gradually. This thickness dependence was explained by the fluorescence quenching of MDMO-PPV by Au electrode and the film resistance of MDMO-PPV.