Preparation and properties of crosslinked hybrid proton exchange membrane based on sulfonated poly (arylene ether nitrile) with improved selectivity for fuel cell application

Novel sulfonated poly (arylene ether nitrile) with pendant carboxylic group copolymers have been prepared as proton exchange membranes which were applied in direct methanol fuel cells (DMFCs). Compared with others, this work shows two main advantages: the crosslinked method is uncomplicated and the membranes were prepared via the hydroquinonesulfonic acid potassium salt (SHQ) as crosslinker mingled in sulfonated poly (arylene ether nitrile) (SPEN) to avoid the decrease of proton conductivity. The obtained crosslinked membranes exhibited improved dimensional stability; larger tensile strength than that of pure SPEN; and good thermal, mechanical properties. Furthermore, after crosslinking, the membranes had low methanol permeability values (0.78–3.4 × 10^?7 cm² s^?1) and displayed good proton conductivities in the range of 0.0328–0.0385 S·cm^?1 at room temperature. The sample of SPEN-SHQ-5 % showed highest selectivity value of 4.205 × 10⁵ S·s cm^?3, which was 11.9 times higher than that of Nafion 117. All of these results indicated that these membranes would be the potential candidates as proton exchange membranes (PEMs) in DMFCs.     

Fabrication of highly selective PVA-g-GO/SPVA membranes via cross-linking method for direct methanol fuel cells

Organic/inorganic composite membranes were prepared using sulfonated poly(vinyl alcohol) (SPVA), mixed and cross-linked with different amounts of poly(vinyl alcohol)-grafted graphene oxide (PVA-g-GO). The introduction of PVA-g-GO to the membranes not only reduced the methanol permeability but also positively affected the mechanical properties: Increasing the PVA-g-GO content increased the blocking effect of GO. The PVA-g-GO/SPVA membranes were cross-linked with glutaraldehyde, resulting in the formation of cross-linking chains within the matrix, as well as between the matrix and the filler. Therefore, the microstructure of the PVA-g-GO/SPVA cross-linking membrane was different from that of the existing membranes. This structure also reduced the methanol permeability. The composite membranes exhibited proton conductivities ranging from 0.0141 to 0.0319 S/cm at 60 °C, and low methanol permeability ranging from 3.13?×?10^?7 to 1.53?×?10^?7 cm² s^?1 at 25 °C.     

Preparation and characterization of hexagonal boron nitride and PAMPS-NMPA-based thin composite films and investigation of their membrane properties

The preparation, thermal, morphological, and ion-conducting properties of new composite membranes based on poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and nitrilotri(methylphosphonic acid) (NMPA)/hexagonal boron nitride (hBN) were carried out throughout this work. Fourier transform infrared (FTIR) spectroscopy was used to characterize the interactions between host polymer, NMPA, and inorganic additive, hBN. Thermal properties of the materials were examined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) tests. TGA results illustrated that all composite membranes are thermally stable up to 200 °C. The surface topography of the films was investigated by scanning electron microscopy (SEM) and verified that hBN uniformly dispersed into the PAMPS-NMPA matrix. The crystallinity of the membranes was characterized by using X-ray diffraction (XRD). X-ray patterns support semicrystalline nature of the composite materials. At anhydrous conditions, the maximum proton conductivity was found as 3.2?×?10^?5 S cm^?1 at 150 °C for PAMPS-NMPA-3hBN via impedance analyzer.     

Influence of the carboxylic acid groups on the structure and properties of sulfonated poly(arylene ether nitrile) copolymer

A series of novel sulfonated poly(arylene ether nitrile) (SPEN) containing carboxylic acid group was successfully synthesized by direct aromatic nucleophilic substitution polycondensation of 2,6-difluorobenzonitrile (DFBN), potassium 2,5-dihydroxybenzenesulfonate (SHQ), phenolphthalin (PPL), and 4,4′-biphenol (BP). The expected chemical structure of copolymers was confirmed by using FTIR and ¹H NMR. To balance the performance for PEM applications, the proportion of four different components were controlled. The influences of the carboxylic acid groups on the structure and properties of SPEN, including thermal and mechanical properties, oxidative stability, water uptake, swelling, proton conductivity, and methanol permeability, were investigated in detail. The results revealed that SPEN membranes containing nitrile and carboxylic acid groups could lead low water absorption, swelling, and methanol penetration. In such a way, efficient proton transport channels were constructed by the formation of the hydrogen bonds. The proton conductivity of SPEN with high sulfonation degree (DS >?0.6) was higher than 0.05 S/cm and increased with increasing temperature. Especially, the conductivity of SPEN-0.6 and SPEN-0.7 reached up to 0.157 and 0.267 S/cm at 80 °C, respectively. Meanwhile, SPEN membranes exhibit low methanol permeability (0.13 ×?10^-6– 0.52 ×?10^-6 cm²·s^?1). Consequently, the highest selectivity of SPEN-0.6 reaches 2.02 ×?10⁵ S·cm^?3·s, which is about 4.5 times higher than that of Nafion 117 (0.45 ×?10⁵ S·cm^?3·s). All the data prove that this series of membranes exhibits excellent comprehensive performance and might have potential applications in direct methanol fuel cells.     

Investigation on (EC/DMC)(70−x)wt% to LiBETI(x)wt% impact on PVdF-co-HFP/octadecylamine-MMT(montmorillonite) nano clay composite electrolytes

The composition dependence of plasticizer (ethylenecarbonate(EC)/dimethyl carbonate(DMC))_(70?x)wt% to Lithium bis(perfluoroethanesulfonyl)imide(LIBETI)_(x)wt% salt (where x?=?1.5, 3.0, 4.5, 6.0 wt%) on PVdF-co-HFP (25 wt%)/surface modified octadecylamine containing montmorrillonite (ODA-MMT) nano clay (5 wt%) matrix has been investigated by AC impedance, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dielectric and cyclic voltammetry studies. The enhanced conductivity 2.1?×?10^?5 Scm^?1 is noted in salt rich phase (EC/DMC)_(70–6)wt% /LiBETI_(x=6)wt% (VK4). In XRD, 2θ at 20.9° confirms β-phase. In FTIR studies, vibrational bands 838, 522 and 611 cm^?1 confirm β-phase of PVdF due to clay intercalation. In DSC studies, the melting of α-phase crystallites is noted between 140–150 °C. In SEM studies, one of the membranes presents fern leaf texture confirming swelling of clay. The increase in dielectric constant and dielectric loss with decrease in frequency is attributed to high contribution of charge accumulation at the electrode–electrolyte interface. In cyclic voltammetry studies, salt-rich phase membrane (VK4) shows good cyclability than other membranes.     

Novel cross-linked membrane for direct methanol fuel cell application: sulfonated poly(ether ether nitrile)s

In order to reduce water uptake, swelling ratio, and methanol permeability in sulfonated proton exchange membranes (PEM), novel-sulfonated aromatic poly(ether ether nitrile)s-bearing pendant propenyl groups had been synthesized by direct copolymerization method. All the results showed that the propenyl groups were suitable cross-linkable groups, and that this method was an effective way to overcome the drawbacks of sulfonated polymers at high ion exchange capacity (IEC) values. By cross-linking, the water uptake, swelling ratio, and methanol diffusion could be restricted owing to the formation of compact network structure. For example, CSPEN-60 membranes showed the proton conductivity of 0.072 S cm^?1 at 80 °C, while the swelling ratios and water uptake (17.9 and 60.7 %) were much lower than that of the SPEN-60 membrane (60.8 and 295.2 %). Meanwhile, a 1.1 × 10^?7 cm² s^?1 of methanol diffusion was obtained which was much lower than that of Nafion 117 (14.1 × 10^?7 cm² s^?1). Although the proton conductivity of the CSPEN-60 membranes is lower than that of the SPEN-60 membrane, the selectivity is much higher. The CSPEN-60 membrane exhibited the highest selectivity among the tested membranes, about 5.8 times higher compared with that of Nafion117.     

Lithium garnet oxide dispersed polymer composite membrane for rechargeable lithium batteries

Free-standing composite polymer membranes comprising of high molecular weight poly (ethylene oxide) (PEO) complexed with lithium perchlorate (LiClO₄) and Li₆La₂BaTa₂O₁₂ (LLBTO) garnet oxide as filler were developed via standard solution-casting method. The as-synthesized composite membranes were investigated through powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and impedance spectroscopy techniques for their phase, thermal, morphological, and electrical properties, respectively. The lithium ion conductivity of polymer composite membranes consisting of PEO₈/LiClO₄ with various weight percents (5, 10, 15, 20, 25, and 30) of LLBTO were evaluated. We demonstrated a significant enhancement in Li⁺ conductivity with the addition of LLBTO to the polymer-lithium salt complex. Among the investigated membranes, the composite containing 20 LLBTO wt% garnet oxide exhibits maximized room temperature (30 °C) Li⁺ conductivity of 2.03 × 10^?4 S cm^?1 and electrochemical stability greater than 4.5 V.     

Novel nanocomposite membranes based on polybenzimidazole and Fe<Subscript>2</Subscript>TiO<Subscript>5</Subscript> nanoparticles for proton exchange membrane fuel cells

In this work, Fe₂TiO₅ nanoparticles were used for improving the proton conductivity, and water and acid uptake of polybenzimidazole (PBI)-based proton exchange membranes. The nanocomposite membranes have been prepared using different amounts of Fe₂TiO₅ nanoparticles and dispersed into a PBI membrane with the solution-casting method. The prepared membranes were then physico-chemically and electrochemically characterized for use as electrolytes in high-temperature PEMFCs. The PBI/Fe₂TiO₅ membranes (PFT) showed a higher acid uptake and proton conductivity compared with the pure PBI membranes. The highest acid uptake (156 %) and proton conductivity (78 mS/cm at 180 °C) were observed for the PBI nanocomposite membranes containing 4 wt% of Fe₂TiO₅ nanoparticles (PFT₄). The PFT₄ composite membrane showed 380 mW/cm² power density and 760 mA/cm² current density in 0.5 V at 180 °C at dry condition. The above results indicated that the PFT₄ nanocomposite membranes could be utilized as proton exchange membranes for high-temperature fuel cells.     

Influences of interfacial adhesion on gas barrier property of functionalized graphene oxide/ultra-high-molecular-weight polyethylene composites with segregated structure

The segregated graphene oxide(GO)/ultra-high-molecular-weight polyethylene (UHMWPE) composite films with various interfacial adhesion property were prepared by mechanical blending method from UHMWPE, GO, dodecyl amine (DA) functionalized graphene oxide(DA–GO) or uniform DA–GO/high density polyethylene (DA–GO/HDPE) powder. The results of XRD and XPS indicated that DA chain was successfully grafted onto GO sheets via a chemical method, which enhanced the interfacial adhesion between UHMWPE particles and GO sheets. The characterizations of POM and SEM proved that good segregated structure was only obtained in DA–GO/UHMWPE or DA–GO/HDPE/UHMWPE composite. Strong interfacial adhesion between fillers and matrix exhibits positive effect on gas barrier property. Compared to the GO/UHMWPE composite film, dramatic decrease in O₂ permeability coefficient by 42.2 and 48.1%, from 15.4 × 10^?14 to 8.9 × 10^?14 and 8.0 × 10^?14 cm³ cm cm^?2 s^?1 Pa^?1, is achieved upon the addition of only 0.5 wt% fillers, respectively. The DSC results demonstrated that the enhanced gas barrier performance was ascribed to the strong interfacial adhesion between DA–GO/HDPE and UHWMPE matrix, rather than the crystallinity of UHWMPE matrix. Additionally, the decrease in UHMWPE particle size might be conducive to improving the gas barrier property of composite films due to the formation of more isolation layers perpendicular to the film plane.     

Surface and Bulk Structure Characterization of Proton (3 MeV) Irradiated Polycarbonate

Polycarbonate (Makrofol‐N) thin films were irradiated with protons (3 MeV) under vacuum at room temperature with the fluence ranging from 1×10¹⁴ to 1×10¹⁵ protons cm^?2. The change in surface morphology, optical properties, degradation of the functional groups, and crystallinity of the proton‐irradiated polymers were investigated with atomic force microscopy (AFM), UV‐VIS, and Fourier‐transform infrared (FTIR) spectroscopy, and X‐ray diffraction (XRD) techniques, respectively. AFM shows that the root mean square (RMS) roughness of the irradiated polycarbonate surface increases with the increment of ion fluence. The UV‐VIS analysis revealed that in Makrofol‐N the optical band gap decreased by 30% at highest fluence of 1×10¹⁵ protons cm^?2. The band gap can be correlated to the number of carbon atoms, M, in a cluster with a modified Robertson's equation. The cluster size in the proton‐irradiated Makrofol‐N increased from 112 to 129 atoms with the increase of fluence from 1×10¹⁴ to 1×10¹⁵ protons cm^?2. FTIR spectra of proton (3 MeV) irradiated Makrofol‐N showed a strong decrease of almost all absorption bands at about 1× 10¹⁴ protons cm^?2. However, beyond a higher critical dose an increase in intensity of almost all characteristic bands was noticed. The appearance of a new peak at 3,500 cm^?1 (‐OH groups) was observed at the higher fluences in the FTIR spectra of proton‐irradiated polycarbonate. XRD measurements showed an increase of full width at half maximum (FWHM) and the average intermolecular spacing of the main peak, which may be due to the increase of chain scission and the introduction of ‐OH groups in the proton irradiated polycarbonate.     

Preparation and properties of sulfonated polybenzimidazole-polyimide block copolymers as electrolyte membranes

Sulfonated polybenzimidazole-polyimide block copolymers are synthesized through condensation polymerization at high temperature. The length of the polyimide chain is varied to give a series of block copolymers with various block lengths. The as-synthesized block polymers are used to prepare the corresponding membranes through the solvent evaporation method. The structure of the block copolymers is characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Their mechanical strength, thermal behavior, water uptake, swelling ratio, and proton conductivity, as well as oxidative stability are also investigated. All the block copolymers exhibit good thermal stability, dimensional stability, mechanical strength, and proton conductivity. Compared to the random sulfonated polyimide-containing benzimidazole membranes with the same degree of sulfonation, the membranes prepared from the block copolymers show higher proton conductivities. The proton conductivities of the block copolymer membranes range from 6.2?×?10^?4 to 1.1?×?10^?2?S cm^?1 at 105 °C. The block copolymer membrane doped with phosphoric acid exhibits proton conductivity higher than 0.2 S cm^?1 at 160 °C, indicating its potential applications in proton exchange membrane fuel cells operated under high temperature and low humidity conditions.     

Conductivity of Nafion-117 membranes intercalated by polar aprotonic solvents

The Nafion-117 membranes in the Li⁺ form with pore-intercalated aprotonic organic solvents were prepared. The prepared materials were characterized by IR, impedance, and ⁷Li NMR spectroscopy. The solvent uptake of the membranes is shown to be controlled by the composition of organic solvents and their mixtures as well as by the conditions of the preliminary treatment of the initial membranes. For the Nafion-117 membrane, the degree of solvation can be improved by the preliminary treatment with alcohols, especially by the thermal treatment in methanol. Conductivity of the membranes is shown to increase with increasing content of the sorbed solvents. The best conductivity at 25 °C (2.5 × 10^?3 and 1.6 × 10^?3 S cm^?1) was attained for the electrolytes based on the Nafion-117 membrane in lithium form with sorbed ethylene carbonate-propylene carbonate and ethylene carbonate-dimethoxyethane mixtures, respectively.     

Influence of pyrazole on the photovoltaic performance of dye-sensitized solar cell with polyvinylidene fluoride polymer electrolytes

We investigate the influence of the pyrazole content on the polyvinylidene fluoride (PVDF)/KI/I₂ electrolytes for dye-sensitized solar cells (DSSCs). The solid polymer electrolyte films consisting of different weight percentage ratios (0 20, 30, 40, and 50 %) of pyrazole doped with PVDF/KI/I₂ have been prepared by solution casting technique using N,N-dimethyl formamide (DMF) as a solvent. The as-prepared polymer electrolyte films were characterized by various techniques such as Fourier transform infrared spectroscopy (FT-IR spectroscopy), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), alternate current (AC)-impedance analysis, and scanning electron microscopy (SEM). The 40 wt% pyrazole-PVDF/KI/I₂ electrolyte exhibited the highest ionic conductivity value of 9.52?×?10^?5 Scm^?1 at room temperature. This may be due to the lower crystallinity of PVDF and higher ionic mobility of iodide ions in the electrolyte. The DSSC fabricated using this highest ion conducting electrolyte showed an enhanced power conversion efficiency of 3.30 % under an illumination of 60 mW/cm² than that of pure PVDF/KI/I₂ electrolyte (1.42 %).     

Green electrolytes based on dextran-chitosan blend and the effect of NH<Subscript>4</Subscript>SCN as proton provider on the electrical response studies

Dextran-chitosan blend added with ammonium thiocyanate (NH₄SCN)-based solid polymer electrolytes are prepared by solution cast method. The interaction between the components of the electrolyte is verified by Fourier transform infrared (FTIR) analysis. The blend of 40 wt% dextran-60 wt% chitosan is found to be the most amorphous ratio. The room temperature conductivity of undoped 40 wt% dextran-60 wt% chitosan blend film is identified to be (3.84?±?0.97)?×?10^?10 S cm^?1. The inclusion of 40 wt.% NH₄SCN to the polymer blend has optimized the room temperature conductivity up (1.28?±?0.43)?×?10^?4 S cm^?1. Result from X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analysis shows that the electrolyte with the highest conductivity value has the lowest degree of crystallinity (χ _c) and the glass transition temperature (T _g), respectively. Temperature-dependence of conductivity follows Arrhenius theory. From transport analysis, the conductivity is noticed to be influenced by the mobility (μ) and number density (n) of ions. Conductivity trend is further verified by field emission scanning electron microscopy (FESEM) and dielectric results.     

Acid-base high temperature proton exchange membranes prepared from phosphonic acid functionalized siloxane

One kind of acid-base high temperature proton exchange membranes has been prepared from amino trimethylene phosphonic acid (ATMP), epoxycyclohexyethyltrimethoxysilane (EHTMS), and 3-aminopropyltriethoxysilane (APTES) by sol-gel process. The structural characteristics of these membranes with different amount of APTES were investigated by FT-IR, XRD, and SEM. These membranes showed excellent dimensional stability in water with the contribution of flexible ionic network structure and were thermally stable up to about 200 °C. In addition, the proton conductivity of the membranes increased with increasing temperature over the range of 20 to 140 °C, up to a maximum of 2.63 × 10^?2 S cm^?1 at 140 °C under anhydrous condition. The high proton conductivity was attributed to the formation of hydrogen bond network through the synergistic effect of N and P. The activation energy value of membranes became lower from 0.46 to 0.30 eV because of the acid-base pairs. The variable-temperature FT-IR further proved the formation of hydrogen bond network in the membrane.     

Lithium diffusion in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-based electrodes: a joint analysis of electrochemical impedance,cyclic voltammetry,pulse chronoamperometry,and chronopotentiometry data

In order to establish the mechanism and to determine the parameters of lithium transport in electrodes based on lithium-vanadium phosphate (Li₃V₂(PO₄)₃), the kinetic model was designed and experimentally tested for joint analysis of electrochemical impedance (EIS), cyclic voltammetry (CV), pulse chronoamperometry (PITT), and chronopotentiometry (GITT) data. It comprises the stages of sequential lithium-ion transfer in the surface layer and the bulk of electrode material’s particles, including accumulation of lithium in the bulk. Transfer processes at both sites are of diffusion nature and differ significantly, both by temporal (characteristic time, τ) and kinetic (diffusion coefficient, D) constants. PITT data analysis provided the following D values for the predominantly lithiated and delithiated forms of the intercalation material: 10^?9 and 3 × 10^?10 cm² s^?1, respectively, for transfer in the bulk and 10^?12 cm² s^?1 for transfer in the thin surface layer of material’s particles. D values extracted from GITT data are in consistency with those obtained from PITT: 3.5–5.8 × 10^?10 and 0.9–5 × 10^?10 cm² s^?1 (for the current and currentless mode, respectively). The D values obtained from EIS data were 5.5 × 10^?10 cm² s^?1 for lithiated (at a potential of 3.5 V) and 2.3 × 10^?9 cm² s^?1 for delithiated (at a potential 4.1 V) forms. CV evaluation gave close results: 3 × 10^?11 cm² s^?1 for anodic and 3.4 × 10^?11 cm² s^?1 for cathodic processes, respectively. The use of complex experimental measurement procedure for combined application of the EIS, PITT, and GITT methods allowed to obtain thermodynamic E,c dependence of Li₃V₂(PO₄)₃ electrode, which is not affected by polarization and heterogeneity of lithium concentration in the intercalate.     

Study on performance of a novel P(VDF-HFP)/SiO2 composite polymer electrolyte using urea as pore-forming agent

Novel poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))-based composite polymer electrolyte (CPE) membranes doped with different contents of nano-SiO₂ using urea as a pore-forming agent were prepared by phase inversion method, and the desired CPEs were obtained by being immersed into 1.0 M LiPF₆-EC/DMC/EMC electrolytes for 0.5 h. The physicochemical properties of the CPEs were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). The results show that the CPEs doped with 10 % nano-SiO₂ exhibit the best performance, in which the SEM images of the as-prepared polymer membranes present homogeneous surface and abundant micropores; the uptake ratio is up to 107.4 %; EIS and LSV analysis also show that the ionic conductivity at room temperature and electrochemical stability window of the modified membrane can reach 3.652 mS cm^?1 and 5.0 V, respectively; the interfacial resistance R _i is 380 Ω cm^?2 in the first day,then increases rapidly to a stable value about 500 Ω cm^?2 in a 5-day storage at room temperature. The Li/As-fabricated CPEs/LiCoO₂ cell also shows excellent charge-discharge performance, which suggests that it can be a potential electrolyte for the lithium-ion battery.     

Nonlinear absorption and optical damage threshold of carbon-based nanostructured material embedded in a protein

Physical processes in laser–matter interaction used to be determined by generation of fast electrons resulting from efficient conversion of the absorbed laser radiation. Composite materials offer the possibility to control the absorption by choice of the host material and dopants. Reported here strong absorption of ultrashort laser pulse in a composite carbon-based nanomaterial including single-walled carbon nanotubes (SWCNTs) or multilayer graphene was measured in the intensity range between 10¹² and 10¹⁶ W cm^?2. A protein (lysozyme) was used as the host. The maximum absorption of femtosecond laser pulse has reached 92–96 %. The optical damage thresholds of the coatings were registered at an intensity of (1.1 ± 0.5) × 10¹³ W cm^?2 for the embedded SWCNTs and at (3.4 ± 0.3) × 10¹³ W cm^?2 for the embedded graphene. Encapsulated variant of the dispersed nanomaterial was investigated as well. It was found that supernatant protein in the coating material tends to dominate the absorption process, independently of the embedded nanomaterial. The opposite was observed for the encapsulated material.     

Study of biopolymer I-carrageenan with magnesium perchlorate

The green revolution has led to the study of biopolymer for development of polymer electrolyte for electrochemical devices. Cellulose acetate, pectin, chitosan, and carrageenan are some of the biopolymers. Biopolymer-based membrane for proton conduction and lithium ion conduction have developed and characterized by different techniques. But the study of biopolymer based on Mg²⁺ ion is rare in literature. So, biopolymer based on I-carrageenan with magnesium has been studied. I-carrageenan biopolymer membrane with different concentration of magnesium perchlorate has been prepared by solution casting technique. Developed biopolymer membrane have been characterized by X-ray diffraction analysis (XRD), FTIR, differential scanning calorimetry (DSC), and AC impedance techniques. Pure I-carrageenan has shown a conductivity value of 5.90?×?10^?5 S/cm. I-carrageenan membrane with 0.6 wt% of magnesium perchlorate has shown a conductivity of 2.18?×?10^?3 S/cm. A primary Mg²⁺ ion battery has been constructed and its performance is studied. XRD has been undertaken to study the amorphous/crystalline nature of the sample. I-carrageenan with 0.6 wt% of magnesium membrane has shown highest amorphous nature. FTIR study confirms the complex formation between polymer and salt. AC impedance technique has been used to study the conductivity of the samples.     

Li+ transportation kinetics of FeF3 · 0.33H2O/C nanocomposite synthesized by one-step solid state method

A new cathode material for lithium ion battery FeF₃?·?0.33H₂O/C was synthesized successfully by a simple one-step chemico-mechanical method. It showed a noticeable initial discharge capacity of 233.9 mAh g^?1 and corresponding charge capacity of 186.4 mAh g^?1. A reversible capacity of ca.157.4 mAh g^?1 at 20 mA g^?1 can be obtained after 50 charge/discharge cycles. To elucidate the lithium ion transportation in the cathode material, the methods of electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) were applied to obtain the lithium diffusion coefficients of the material. Within the voltage level of 2.05–3.18 V, the method of EIS showed that \( {D}_{{\mathrm{Li}}^{+}} \) varied in the range of 1.2?×?10^?13?~?3.6?×?10^?14 cm² s^?1 with a maximum of 1.2?×?10^?13 cm² s^?1 at 2.5 V. The method of GITT gave a result of 8.1?×?10^?14?~?1.2?×?10^?15 cm² s^?1. The way and the range of the variation for lithium ion diffusion coefficients measured by the GITT method show close similarity with those obtained by the EIS method. Besides, they both reached their maximum at a voltage level of 2.5 V.