Electrochemical behavior of ionically crosslinked polyampholytic gel electrolytes

An ionic complex of anionic and cationic monomers was obtained by protonation of (N,N-diethylamino)ethylmethacrylate (DEA) with acrylic acid (AAc). Free radical copolymerization of the ionic complex and acrylamide (AAm), yielded the ionically crosslinked polyampholytic gel electrolytes [poly(AAc-DEA-AAm), designated as PADA] using two types of organic solvents containing a lithium salt. The PADA gel electrolyte exhibited good thermal stability shown by the DSC thermogram. The impedance analysis at temperatures ranging from −30 to 75 °C indicated that the ionic conductivities of the PADA gel electrolytes were rather close to those of liquid electrolytes. The temperature dependence of the ionic conductivities was found to be in accord with the Arrhenius equation. Moreover, the ionic conductivities of PADA gel electrolytes increased with an increase of the molar ratios of cationic/anionic monomers. The ionic conductivities of PADA gels prepared in solvent mixtures of propylene carbonate, ethyl methyl ether and dioxolane (3:1:1, v/v) were higher than those of PADA gels prepared in propylene carbonate only. Significantly, the ionic conductivities of two kinds of PADA gel electrolytes were in the range of 10⁻³ and 10⁻⁴ S cm⁻¹ even at −30 °C. The electrochemical windows of PADA gel electrolytes measured by cyclic voltammetry were in the range from −1 V to 4.5 V.     

A series of LiI/acetamide phase transition electrolytes and their applications in dye-sensitized solar cells

A new series of electrolytes composed of LiI and acetamide have been investigated in dye-sensitized solar cells (DSSCs). These electrolytes melt at about 50 °C and their ionic conductivities vary drastically below and above the melting points (T_m). They tend to form large crystals at low temperature, leading to poor penetration and contact within porous TiO₂ anode film. This shortage is improved by introducing nano-SiO₂ particles into the electrolyte. A total conversion efficiencies (η) of 0.3% at 35 °C and 4.2% at 75 °C are achieved respectively under AM 1.5 simulated solar light illumination when a LiI/acetamide (1:16) electrolyte with 8 wt% nano-SiO₂ is used. It is expected that the DSSC using phase transition electrolyte could show high efficiency for operation at high temperature and high stability for storage at low temperature.     

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.     

Synthesis and characterization of poly(1-vinyl-3-alkylimidazolium) iodide polymers for quasi-solid electrolytes in dye sensitized solar cells

A series of new poly(1-vinyl-3-alkylimidazolium) iodide polymers with different alkyl derivatives such as methyl, propyl and perflurodecyl have been synthesized. The alkyl substituent influenced some properties such as solubility, thermal stability, glass transition and crystallinity of the polymers. For instance, polymer having the propyl substituent was soluble in solvents of intermediate polarity such as acetonitrile, chloroform and THF, the one with the methyl substituent was only soluble in very polar solvents such as water and methanol and the fluorinated polymer was only soluble in DMF. The alkyl substituent also influenced the thermal stability in the order methyl > propyl > perflurodecyl and all the polymers thermally decomposed between 250 and 400 °C in nitrogen. The poly(1-vinyl-3-alkyl-imidazolium) iodide polymers having propyl and methyl substituents were amorphous polymers showing a glass transition temperature of 43 and 21 °C, respectively; and perflurodecyl polymers were semi-crystalline with a Tm at 153 °C and a Tg at 20 °C, as indicated by differential scanning calorimetry.Polymer electrolytes were formulated as mixtures of the ionic liquid 1-methyl-3-propylimidazolium iodide and the poly(1-vinyl-3-alkylimidazolium) iodide polymers. These polymer electrolytes showed ionic conductivities in the range of 10⁻³ to 10⁻⁷ S/cm at room temperature which strongly depended on the ionic liquid content. Finally, poly(1-vinyl-3-propyl-imidazolium) iodide was used to obtain gel electrolytes by adding it to a typical acetonitrile electrolyte used in dye sensitized solar cells (DSSCs). Solar cells with 1 cm² area prepared using the polymer gel electrolyte yielded a maximum light-to-electricity conversion efficiency of 3.73%.     

Solvents in salt electrolyte: Benefits and possible use as electrolyte for lithium-ion battery

An EC/DEC [40:60% (v/v)] solvent mixture has been added in various amounts to the ionic liquid (IL) hexyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N₁₁₁₆-NTf₂) in the presence of LiNTf₂ (lithium bis(trifluoromethylsulfonyl)imide) as lithium salt for possible use as electrolytes in lithium-ion batteries. These electrolytes exhibit a larger thermal stability than the reference electrolyte EC/DEC [40:60] + LiNTf₂ 1 M when the percentage of the IL exceeds 30% (v/v). All studied electrolytes are glass forming ones with an ideal glass transition temperature of ca. −85 °C(±5 °C), which has been determined by application of the VTF theory to conductivity and viscosity measurements and confirmed by DSC (T_g = −90 ± 5 °C). An electrochemical window of about 5 V versus Li/Li⁺ was measured at a glassy carbon electrode. The cycling ability of the optimized electrolyte N₁₁₁₆-NTf₂/EC:DEC (40/60% (v/v)) + 1 M LiNTf₂ has been investigated at a titanate oxide (Li₄Ti₅O₁₂) and a cobalt oxide (Li_xCoO₂) electrodes. Cycling the positive and the negative electrodes was conducted successfully with a high capacity and without any significant fading.     

Microstructural and electrical behavior of Bi4V2−xCuxO11−δ (0 ≤ x ≤ 0.4)

Cation substituted bismuth vanadate possesses high oxygen ion conductivity at lower temperatures. The ionic conductivity of this material at 300 °C is 50–100 times more than any other solid electrolyte. Three phases (α, β, γ) are observed in the substituted compound; α and γ are low and high conducting phase, respectively. Samples of Bi₄V_2−xCu_xO_11−δ (x = 0–0.4) were prepared by solid-state reaction technique. Impedance spectroscopy measurements were carried out in the frequency range of 100 Hz to 100 kHz using gold sputtered cylindrical shaped pellets to obtain bulk ionic conductivities as a function of the substitution and temperature. The change of slopes observed in the Arrhenius plots is in agreement with the phase transitions for all the compositions. The highest ionic conductivity of the Cu-substituted compound was observed in Bi₄V_1.8Cu_0.2O_11−δ which is attributed to its lower activation energy. Microstructural studies indicated the stabilization of high temperature γ-phase at low temperature in those samples whose ionic conductivity observed was higher.     

Synthesis and electrochemical properties of lithium methacrylate-based self-doped gel polymer electrolytes

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.     

Physical and electrochemical properties of 1-(2-hydroxyethyl)-3-methyl imidazolium and N-(2-hydroxyethyl)-N-methyl morpholinium ionic liquids

Various ionic liquids (ILs) were prepared via metathesis reaction from two kinds of 1-(2-hydroxyethyl)-3-methyl imidazolium ([HEMIm]⁺) and N-(2-hydroxyethyl)-N-methyl morphorinium ([HEMMor]⁺) cations and three kinds of tetrafluoroborate ([BF₄]⁻), bis(trifluoromethanesulfonyl)imide ([TFSI]⁻) and hexafluorophosphate ([PF₆]⁻) anions. All the [HEMIm]⁺ derivatives were in a liquid state at room temperature. In particular, [HEMIm][BF₄] and [HEMIm][TFSI] showed no possible melting point from −150 °C to 200 °C by DSC analysis, and their high thermal stability until 380-400 °C was verified by TGA analysis. Also, their stable electrochemical property (electrochemical window of more than 6.0 V) and high ionic conductivity (0.002-0.004 S cm⁻¹) further confirm that the suggested ILs are potential electrolytes for use in electrochemical devices. Simultaneously, the [HEMMor]⁺ derivatives have practical value in electrolyte applications because of their easy synthesis procedures, cheap morpholinium cation sources and possibilities of high Li⁺ mobility by oxygen group in the morpholinium cation. However, [HEMMor]⁺ derivatives showing high viscosity usually had lower ionic conductivities than [HEMIm]⁺ derivatives.     

Effect of surface modified porous inorganic-organic hybrid polyphosphazene nanotubes on the properties of polyethylene oxide based solid polymer electrolytes

2-(2-methyloxyethoxy)ethanol modified poly (cyclotriphosphazene-co-4,4′-sufonyldiphenol) (PZS) nanotubes were synthesized and solid composite polymer electrolytes based on the surface modified polyphosphazene nanotubes added to PEO/LiClO₄ model system were prepared. Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) were used to investigate the characteristics of the composite polymer electrolytes (CPE). The ionic conductivity, lithium ion transference number and electrochemical stability window can be enhanced after the addition of surface modified PZS nanotubes. The electrochemical investigation shows that the solid composite polymer electrolytes incorporated with PZS nanotubes have higher ionic conductivity and lithium ion transference number than the filler SiO₂. Maximum ionic conductivity values of 4.95 × 10⁻⁵ S cm⁻¹ at ambient temperature and 1.64 × 10⁻³ S cm⁻¹ at 80 °C with 10 wt % content of surface modified PZS nanotubes were obtained and the lithium ion transference number was 0.41. The good chemical properties of the solid state composite polymer electrolytes suggested that the inorganic-organic hybrid polyphosphazene nanotubes had a promising use as fillers in solid composite polymer electrolytes and the PEO₁₀-LiClO₄-PZS nanotubes solid composite polymer electrolyte can be used as a candidate material for lithium polymer batteries.     

Electrochemical investigations of ionic liquids with vinylene carbonate for applications in rechargeable lithium ion batteries

Ionic liquids based on methylpropylpyrrolidinium (MPPY) and methylpropylpiperidinium (MPPI) cations and bis(trifluoromethanesulfonyl)imide (TFSI) anion have been synthesized and characterized by thermal analysis, cyclic voltammetry, impedance spectroscopy as well as galvanostatic charge/discharge tests. 10 wt% of vinylene carbonate (VC) was added to the electrolytes of 0.5 M LiTFSI/MPPY.TFSI and 0.5 M LiTFSI/MPPI.TFSI, which were evaluated in Li || natural graphite (NG) half cells at 25 °C and 50 °C under different current densities. At 25 °C, due to their intrinsic high viscosities, the charge/discharge capacities under the current density of 80 μA cm⁻² were much lower than those under the current density of 40 μA cm⁻². At 50 °C, with reduced viscosities, the charge/discharge capacities under both current densities were almost indistinguishable, which were also close to the typical values obtained using conventional carbonate electrolytes. In addition, the discharge capacities of the half cells were very stable with cycling, due to the effective formation of solid electrolyte interphase (SEI) on the graphite electrode. On the contrary, the charge/discharge capacities of the Li || LiCoO₂ cells using both ionic liquid electrolytes under the current density of 40 μA cm⁻² decreased continually with cycling, which were primarily due to the low oxidative stability of VC on the surface of LiCoO₂.     

Low temperature performance of graphite electrode in Li-ion cells

We studied low temperature performance of Li/graphite cell. Results show that capacity of the graphite electrode falls significantly in the temperature range of 0 to −20 °C. When lithiation and delithiation are both carried out at −20 °C, graphite only retains 12% of the room temperature capacity. However, delithiation capacity of graphite increases to 92% of the room temperature value if the lithiation is carried out at room temperature. We believe that the poor low temperature performance of the cell is due to slow kinetics of lithium ion diffusion in graphite rather than low ionic conductivity of electrolyte and solid electrolyte interface (SEI) on the graphite surface. During lithiation and delithiation processes, lithium ion has the similar apparent chemical diffusion coefficient of 10⁻⁹-10⁻¹⁰ cm²/s at 20 °C, depending on the state of lithiation of graphite. We observed a dramatic decrease in lithium ion diffusivity in the temperature range of 0 to −20 °C, and that at low temperatures of <−20 °C, lithium ion has higher diffusivity in the delithiated graphite than in the lithiated one. We also observed that temperature dependence of cycling behavior of the Li/graphite cell follows the change of lithium ion diffusivity.     

Dye sensitized solar cells with poly(acrylonitrile) based plasticized electrolyte containing MgI2

Polymer electrolytes can be used favorably in photo-electrochemical solar cells. A possible electrolyte for this purpose is a polyacrylonitrile-MgI₂ complex with plasticizers such as ethylene carbonate and propylene carbonate. The best ionic conductivity was obtained for samples containing 60 wt% of MgI₂ salt with respect to the weight of polyacrylonitrile, for example, at 30 °C the conductivity is 1.9 × 10⁻³ S cm⁻¹. The ionic contribution to the conductivity is dominant as shown by dc polarization tests. Furthermore, the glass transition temperature showed a minimum, −103.0 °C, for the sample with the highest conductivity indicating the importance of polymer chain flexibility for the conduction process. Measurements on a fabricated solar cell with this electrolyte exhibited an overall energy conversion efficiency of 0.84%. The short circuit current density, open circuit voltage and fill factor of the cell were 2.04 mA cm⁻², 692 mV and 59.3%, respectively.     

Preparation and characterization of 10 mol% Gd doped CeO2 (GDC) electrolyte for SOFC applications

Ceria-based materials are prospective electrolytes for low and intermediate temperature solid oxide fuel cells. In the present work, fully dense CeO₂ ceramics doped with 10 mol% gadolinium (Gd_0.1Ce_0.9O_1.95, GDC) have been prepared with a Pechini method. Characterization studies were realized with thermo-gravimetric analysis (TGA), differential thermal analysis (DTA), mass spectroscopy (MS), high temperature FT-IR (HT-FTIR) and X-ray diffraction analysis (XRD). A single-phase with a fluorite type structure was found to form at a relatively low calcination temperature of 500 °C. Dense GDC pellets having 98% of the relative density were obtained at sintering temperature of 1400 °C/6 h, which gave significantly higher total ionic conductivity of 3.4×10⁻² S cm⁻¹ at 500 °C in air. The present work showed that the Pechini method is a relatively low-temperature preparation technique to synthesize Gd_0.1Ce_0.9O_1.95 powders that provided high sinterability and good ionic conductivity.     

Proton-conducting electrolyte membranes based on hyperbranched polymer with a sulfonic acid group for high-temperature fuel cells

The hyperbranched polymers (HBP-SA-Acs) with both a sulfonic acid group as a functional group and an acryloyl group as a cross-linker at terminals in different ratios of sulfonic acid group/acryloyl group (SO₃H/Ac) were successfully synthesized as a new thermally stable proton-conducting electrolyte. The cross-linked hyperbranched polymer electrolyte membranes (CL-HBP-SAs) were prepared by thermal polymerizations of the HBP-SA-Acs using benzoyl peroxide, and their ionic conductivities under dry condition and thermal properties were investigated. The ionic conductivities of the CL-HBP-SAs were found to be in the range of 2.2 × 10⁻⁴ to 3.3 × 10⁻⁶ S/cm, depending upon the SO₃H unit contents, at 150 °C under dry condition, and showed the Vogel-Tamman-Fulcher (VTF) type temperature dependence, indicating that proton transfer is cooperated by local polymer chain motion. All CL-HBP-SAs were thermally stable up to 260 °C, and they had suitable thermal stability as electrolyte membranes for the high-temperature fuel cells under dry condition. Fuel cell measurement using a single membrane electrode assembly cell with a cross-linked electrolyte membrane was successfully performed under non-humidified condition. It was demonstrated that applying the concept of dry polymer system to proton conduction is one possible approach toward high-temperature fuel cells.     

Ionic conductivity in polyethylene-b-poly(ethylene oxide)/lithium perchlorate solid polymer electrolytes

The ionic conductivity and phase arrangement of solid polymeric electrolytes based on the block copolymer polyethylene-b-poly(ethylene oxide) (PE-b-PEO) and LiClO₄ have been investigated. One set of electrolytes was prepared from copolymers with 75% of PEO units and another set was based on a blend of copolymer with 50% PEO units and homopolymers. The differential scanning calorimetry (DSC) results, for electrolytes based on the copolymer with 75% of PEO units, were dominated by the PEO phase. The PEO block crystallinity dropped and the glass transition increased with salt addition due to the coordination of the cation by PEO oxygen. The conductivity for copolymers 75% PEO-based electrolyte with 15 wt% of salt was higher than 10⁻⁵ S/cm at room temperature and reached to 10⁻³ S/cm at 100 °C on a heating measurement. The blend of PE-b-PEO (50% PEO)/PEO/PE showed a complex thermal behavior with decoupled melting of the blocks and the homopolymers. Upon salt addition the endotherms associated with PEO domains disappeared and the PE crystals remained untouched. The conductivity results were limited at 100 °C to values close to 10⁻⁴ S/cm and at room temperature values close to 3 × 10⁻⁶ S/cm were obtained for the 15 wt% salt electrolyte. Raman study showed that the ionic association of the highly concentrated blend electrolytes at room temperature is not significant. Therefore, the lower values of conductivity in the case of the blend with 50% PEO can be assigned to the higher content of PE domains leading to a morphology with lower connectivity for ionic conduction both in the crystalline and melted state of the PE domains.     

A highly conductive organic-inorganic hybrid electrolyte based on co-condensation of di-ureasil and ethylene glycol-containing alkoxysilane

Organic-inorganic hybrid electrolytes based on di-ureasil backbone structures by reacting poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminopropyl ether) (ED2000) with 3-(triethoxysilyl)propyl isocyanate (ICPTES), followed by co-condensation with methoxy(polyethylenoxy)propyl trimethoxysilane (MPEOP) in the presence of LiClO₄ were prepared and characterized by a variety of techniques. The hybrid electrolytes showed good resistance to crystallization and excellent conductivity for use in lithium-ion batteries, as determined by differential scanning calorimetry (DSC) and impedance measurements, respectively. The temperature dependence of the ionic conductivity exhibited a VTF (Vogel-Tamman-Fulcher)-like behavior for all the compositions studied and a maximum ionic conductivity value of 6.9 × 10⁻⁵ S cm⁻¹, a relatively high value for solid polymer electrolytes, was achieved at 30 °C for the hybrid electrolyte with a [O]/[Li] ratio of 16. A microscopic view of the dynamic behavior of the polymer chains (¹³C) and the ionic species (⁷Li) was provided by the ¹H and ⁷Li line widths measured from 2D ¹H-¹³C WISE (Wideline Separation) and variable temperature ⁷Li static NMR, respectively, to elucidate the influence of the mobility of the polymer chains and the charge carriers on the observed ionic conductivity. The present salt-free hybrid electrolyte after plasticization with 1 M LiClO₄ in EC/PC solution exhibited a swelling ratio of 275% and reached an ionic conductivity value up to 8.3 × 10⁻³ S cm⁻¹ at 30 °C, which make it a good candidate for the further development of advanced rechargeable lithium-ion batteries.     

Cation driven actuation for free standing PEDOT films prepared from propylene carbonate electrolytes containing TBACF3SO3

Free standing PEDOT [poly(3,4-ethylenedioxythiophene)] films (with surface conductivities of 200-400 S cm⁻¹) were generated in tetrabutylammonium trifluromethanesulfonate (TBACF₃SO₃) electrolytes by potentiostatic (E_P 1.05 V vs. Ag wire) electropolymerisation in propylene carbonate (at −27 °C) and methyl benzoate (at −4 °C). Films obtained in the TBACF₃SO₃ electrolytes showed a length increase of 2-3% during scans to negative potentials under isotonic (constant load 1.35 MPa) and stress of 0.3 MPa under isometric (constant length) conditions. Cation movement occurred due to immobilisation of CF₃SO₃⁻ anions during electropolymerisation. The system showed good stability and low creep during square wave electrochemical cycling in the potential range from 0.0 to 1.0 V. The surface morphology (SEM) of the PEDOT films showed that the polymer structure is dependent upon the solvent used during the polymerisation process.     

Plastic-polymer composite electrolytes for solid state dye-sensitized solar cells

Three types of alkyl-substituted poly(N-alkyl-1-vinyl-imidazolium) iodides were synthesized and plasticized using succinonitrile as a solid plasticizer to develop a series of novel solvent-free plastic-polymer composite electrolytes. All these electrolytes appeared as a soft solid at room temperature and became sticky gel state at high temperature of 100 °C. Among the as-prepared plastic-polymer electrolytes, the SCN-PMVII (succinonitrile-poly(1-vinyl-3-methylimidazolium) iodide) electrolytes with a SCN content of 40-60 wt.% showed a room temperature conductivity of 1.0-1.6 mS cm⁻¹and a photoconversion efficiency of >4.1%, which are comparable to those observed from liquid organic carbonate electrolyte and the DSSCs using the liquid electrolyte at the same experimental conditions. Also, the DSSCs assembled with the SCN-PMVII electrolytes maintained their photoconversion efficiency very steadily during aging test of 50 days despite of being placed at 40 °C under 1 sun illumination or stored at 60 °C in an oven. Since these plastic-polymer electrolytes are solvent-free, highly conductive and electrochemically compatible, it is possible to use this type electrolyte for development of practical DSSCs.     

Soft matter electrolytes based on polymethylmetacrylate dispersions in lithium bis(trifluoromethanesulfonyl)imide/1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquids

Ion transport in a polymer-ionic liquid (IL) soft matter composite electrolyte is discussed here in detail in the context of polymer-ionic liquid interaction and glass transition temperature. The dispersion of polymethylmetacrylate (PMMA) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF₆) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) resulted in transparent composite electrolytes with a “jelly-like” consistency. The composite ionic conductivity measured over the range −30 °C to 60 °C was always lower than that of the neat BMITFSI/BMIPF₆ and LiTFSI-BMITFSI/LiTFSI-BMIPF₆ electrolytes but still very high (>1 mS/cm at 25 °C up to 50 wt% PMMA). While addition of LiTFSI to IL does not influence the glass T_g and T_m melting temperature significantly, dispersion of PMMA (especially at higher contents) resulted in increase in T_g and disappearance of T_m. In general, the profile of temperature-dependent ionic conductivity could be fitted to Vogel-Tamman-Fulcher (VTF) suggesting a solvent assisted ion transport. However, for higher PMMA concentration sharp demarcation of temperature regimes between thermally activated and solvent assisted ion transport were observed with the glass transition temperature acting as the reference point for transformation from one form of transport mechanism to the other. Because of the beneficial physico-chemical properties and interesting ion transport mechanism, we envisage the present soft matter electrolytes to be promising for application in electrochromic devices.     

Conductivity study of a gelatin-based polymer electrolyte

Natural polymers are particularly interesting due to their richness in nature, very low cost and principally biodegradation properties. For these reasons different solid polymeric electrolytes (SPE) have been obtained using cellulose derivatives, starch, chitosan and rubber. This work presents the results of gelatin-based protonic SPEs, which were characterized by impedance spectroscopy, X-ray diffraction, UV-vis-NIR spectroscopy and scanning electron microscopy (SEM). The ionic conductivity results obtained for these SPEs were 4.5 × 10⁻⁵ S/cm and 3.6 × 10⁻⁴ S/cm at room temperature and 80 °C, respectively. Temperature-dependent ionic conductivity measurements were taken to analyze the mechanism of ionic conduction in polymer electrolytes. Good conductivity results combined with transparency and good adhesion to the electrodes have shown that gelatin-based SPEs are very promising materials to be used as solid electrolyte in electrochromic devices.