Enhanced electrochemical properties of polyethylene oxide-based composite solid polymer electrolytes with porous inorganic–organic hybrid polyphosphazene nanotubes as fillers

Solid composite polymer electrolytes consisting of polyethylene oxide (PEO), LiClO₄, and porous inorganic–organic hybrid poly (cyclotriphosphazene-co-4, 4′-sulfonyldiphenol) (PZS) nanotubes were prepared using the solvent casting method. Differential scanning calorimetry and scanning electron microscopy were used to determine the characteristics of the composite polymer electrolytes. The ionic conductivity, lithium ion transference number, and electrochemical stability window can be enhanced after the addition of PZS nanotubes. The electrochemical impedance showed that the conductivity was improved significantly. Maximum ionic conductivity values of 1.5 × 10⁻⁵ S cm⁻¹ at ambient temperature and 7.8 × 10⁻⁴ S cm⁻¹ at 80 °C were obtained with 10 wt.% content of PZS nanotubes, and the lithium ion transference number was 0.35. The good electrochemical properties of the solid-state composite polymer electrolytes suggested that the porous inorganic–organic hybrid polyphosphazene nanotubes had a promising use as fillers in SPEs and the PEO₁₀–LiClO₄–PZS nanotube solid composite polymer electrolyte might be used as a candidate material for lithium polymer batteries.     

Visible Photoluminescence in Polysilanes

 The photoluminescence spectrum of poly-(methyl-(phenyl)-silanediyl) shows a strong narrow peak in the UV region which is of excitonic nature and related to σ^*-σ transitions. The broad emission peak in the visible region is related to polymer branching, charge transfer transitions, and defect electronic states (backbone scission). Chemical substitution of the Si backbone with π-conjugated side groups allows to generate photoluminescence also in the visible region.     

A novel hyperbranched copolymer constituted of triphenylamine and divinyl bipyridyl units

A hyperbranched copolymer (HTP) containing triphenylamine and divinyl bipyridyl units has been synthesized via Heck coupling reaction from 5,5′-divinyl-2,2′-bipyridyl and tris(4-bromophenyl)amine. The polymer had a number-average molecular weight of 1895 and a weight-average molecular weight of 2315, and was readily soluble in common organic solvents, such as THF, DMF and chloroform. The chemical structure of HTP was confirmed by FT-IR, ¹H NMR. Its thermal, electrochemical and optical properties have been investigated. The thermal analysis revealed that the polymer had a good thermal stability with the onset decomposition temperature at ca. 267 °C. The Uv-vis absorption and photoluminescence (PL) spectra exhibited that the Stokes shift between the absorption and emission of HTP was relatively large: 103 for HTP solution and 135 nm for HTP film. The electrochemical analysis showed that the electrochemical band gap of HTP was 0.92 eV. The fluorescence of the polymer in solution can be quenched by various transition metal ions and HTP showed different sensitivity in transition metal ions sensing.     

New confined p-phenylenevinylene (PPV)-type polymer analogue of poly(phenylene sulfide)

A new confined p-phenylenevinylene (PPV)-type polymer (PPVS) has been synthesized using Wittig condensation. The chemical structure of the polymer was well defined by ¹H NMR, ¹³C NMR, and FTIR spectroscopic analysis. PPVS contains oligomeric PPV units separated by sulfide bridges in the main chain; it is fully soluble in common organic solvents and has a number-average molecular weight of 3500 g mol⁻¹. Thermogravimetric analysis and differential scanning calorimetry indicate that PPVS is amorphous, stable up to 360 °C in air and displays a glass transition temperature of 98 °C. The optical properties of the polymer were investigated by UV-visible absorption and photoluminescence spectroscopies. The polymer film absorbs at 375 nm and emits at 517 nm with a narrow emission spectrum. From the cyclic voltammetry analysis, the electrochemical bandgap was estimated to be 2.78 eV. A single-layer diode device of the configuration indium-tin oxide/PPVS/aluminium has been fabricated and has a relatively low turn-on voltage of 3.4 V. An electroluminescent emission similar to photoluminescence is demonstrated in a multilayer device.     

Anion receptor-coated separator for lithium-ion polymer battery

Anion receptor-coated separators were prepared by coating poly(ethylene glycol) borate ester (PEGB) as an anion receptor and poly(vinyl acetate) (PVAc) as a good adhesive material towards electrodes onto microporous polyethylene (PE) separators. Gel polymer electrolytes were fabricated by soaking them in an liquid electrolyte, 1 M LiPF₆ in EC/DEC/PC (30/65/5, wt.%). As the weight ratio of PEGB to PVAc in a coating layer increased, gel polymer electrolytes showed higher cationic conductivity and electrochemical stability. The cationic conductivity and electrochemical stability of the gel polymer electrolyte based on coated separator with PVAc/PEGB (2/5, weight ratio) could reach 2.8 × 10^–4 S cm^–1 and 4.8 V, respectively. Lithium-ion polymer cells (LiCoO₂/graphite) based on gel polymer electrolytes with and without PEGB were assembled, and their electrochemical performances were evaluated.     

New conducting polymers, 3. Doping,stability, electrical,and optical characteristics of poly-(P-phenylphosphoethynediyl)

Studies on direct-current electrical conductivity and optical properties of a new solution of processable conducting polymer are reported. Electrical conductivity of thin films of the polymer on glass plate at room temperature was 6×10⁻⁶ S/cm. Study of conductivity with variation of temperature does not provide any definite thermal activation energy, which is in accordance with the amorphous nature of polymer. Optical absorption data adopting the Bardeen equation showed that maximum ‘optical gap’ (E _g ) is 3.30 eV. Doping with Br₂-vapor was found to be only partially effective in decreasingE _g by 0.43 eV. The polymer was found to be quite stable under normal atmospheric conditions. Environmental stability of both undoped and doped polymer has been discussed. Part 2: [5]     

Visible Photoluminescence in Polysilanes

Summary.  The photoluminescence spectrum of poly-(methyl-(phenyl)-silanediyl) shows a strong narrow peak in the UV region which is of excitonic nature and related to σ^*-σ transitions. The broad emission peak in the visible region is related to polymer branching, charge transfer transitions, and defect electronic states (backbone scission). Chemical substitution of the Si backbone with π-conjugated side groups allows to generate photoluminescence also in the visible region. Received June 23, 2000. Accepted (revised) August 7, 2000     

Polypyrrole-poly(3-methylthiophene) bilayer films electrochemically deposited onto tin oxide

We report the electrochemical successive deposition of layers of polypyrrole and poly(3-methylthiophene), forming conjugated polymer heterostructures onto a tin oxide-covered glass substrate. The polymer bilayer thickness and roughness were determined as a function of deposition conditions, varying the sequence of deposition of the conjugated polymer layers. The charge transport characteristics of these bilayer devices were investigated and an effective charge carrier mobility of the order of 10^–10 cm² V^–1 s^–1 was determined. Electronic Publication     

Copper(II) ion-selective microelectrochemical transistor

A device has been developed for the measurement of copper(II) ions (Cu²⁺) in aqueous medium. The device reported here is an electrochemical transistor which consists of two platinum electrodes separated by 100 μm spacing and bridged with an anodically grown film of polycarbazole. Polycarbazole film (undoped form) is observed to be highly selective for the Cu(II) ions. In a completed device, the conductivity of the polycarbazole film changes on addition of Cu(II) ions. The change in conductivity is attributed to the conformational changes in the polymer phase on occupation of the Cu(II) ions, without affecting electron/proton transfer. The device turns on by adding 2.5 × 10⁻⁶ M Cu(II) ions and reaches a saturation region beyond 10⁻⁴ M Cu(II) ion concentrations. In the above concentration range, the device response [I _D vs. log Cu(II) ion concentration] is linear. The selectivity of the device for other metal ions such as Cu(I), Ni(II), Co(II), Fe(II), Fe(III), Zn(II) and Pb(II) is also studied. Received: 6 April 1999 / Accepted: 20 August 1999     

Potentiometric sensors for Ag+ based on poly(3-octylthiophene) (POT)

Potentiometric ion sensors were prepared from the conjugated polymer poly(3-octylthiopene) (POT). The influence of additional membrane components, including silver 7,8,9,10,11,12-hexabromocarborane (AgCB₁₁H₆Br₆) and potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (KTpFPB) as lipophilic salts, and [2.2.2]p,p,p-cyclophane as silver ionophore, was studied. The membrane components were dissolved in chloroform and membranes were prepared by solution casting on glassy carbon disk electrodes. For comparison, POT-based potentiometric sensors were also prepared by galvanostatic electrosynthesis of POT from the 3-octylthiophene monomer. All the POT-based ion sensors fabricated by solution casting show Nernstian or slightly sub-Nernstian response to Ag⁺, even those based only on POT without any additional membrane components. The potentiometric response of electrochemically polymerized POT depends on the film thickness and the doping anion incorporated in the conducting polymer during polymerization. It is of particular importance that chemically synthesized undoped POT (without any additives) shows a sensitive and selective potentiometric response to Ag⁺ ions although UV-vis results show that POT remains in its undoped form, i.e., POT is not oxidized by Ag⁺. This indicates that undoped POT can exhibit good sensitivity and selectivity to Ag⁺ also in the absence of metallic silver in the polymer film. In this case, the potentiometric response is related to interactions between Ag⁺ and the conjugated polymer backbone. Presented at the 4th Baltic Conference on Electrochemistry, Greifswald, 13–16, 2005     

Poly(vinylferrocenium) perchlorate–polyaniline composite film-coated electrode for amperometric determination of hydroquinone

Poly(vinylferrocenium) perchlorate–polyaniline (PVF⁺–PANI) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture of poly(vinylferrocene) (PVF) polymer and aniline monomer. PVF⁺ polymer in the composite film was used as an electron transfer mediator. The composite coating showed significant electrochemical activity towards hydroquinone (HQ) at pH 4, with high sensitivity and a wide linearity range. The interaction of HQ with PVF⁺ and PANI homopolymer films was investigated electrochemically and spectroscopically. HQ molecules are accumulated on the electrode surface due to trapping by both polymers in the composite film and then oxidized catalytically by PANI. The most significant contribution of PVF⁺ polymer is that it facilitates electron transfer in the composite film. The linear response range was found to be between 1.60 × 10⁻⁴ mM and 115 mM (R ² = 0.999) at 0.45 V vs saturated calomel electrode. The limit of detection (LOD) was 4.94 × 10⁻⁵ mM.     

PVDF-HFP composite polymer electrolyte with excellent electrochemical properties for Li-ion batteries

Poly (vinylidene fluoride-co-hexafluoropropylene)-based composite polymer electrolyte (CPE) was prepared by phase inversion technique. In this work, we first applied a novel surface-modified sub-micro-sized alumina, PC-401, as ceramic filler. Various electrochemical methods were applied to investigate the electrochemical properties of the polymer electrolytes. We found that the CPE with 10 wt.% PC-401 has excellent electrochemical properties, including the ionic conductivity as high as 0.89 mS cm⁻¹ and the Li-ion transference number of 0.46. Polymer Li-ion batteries using LiFePO₄ as cathode active material exhibited excellent cycling and high-temperature performances. PC-401 shows a promising applicability in the preparation of polymer electrolyte with high electrochemical properties.     

Solid-contact Cu(II) ion-selective electrode based on 1,2-di-(<Emphasis Type="Italic">o</Emphasis>-salicylaldiminophenylthio)ethane

The development of Cu(II) solid-contact ion-selective electrodes, based on 1,2-di-(o-salicylaldiminophenylthio)ethane as a neutral carrier, is presented. For the electrodes construction, unmodified carbon ink (type 1 electrode) and polymer membrane-modified carbon ink (type 2 electrode) were used as solid support and transducer layer. Also, carbon ink composite polymer membrane electrode (type 3 electrode) was prepared. The analytical performance of the electrodes was evaluated with potentiometry, while bulk and interfacial electrode features were provided with electrochemical impedance spectroscopy. It is shown that modification of carbon ink with polymer membrane cocktail decreases the bulk contact resistance of the transducer layer and polymer membrane, thus enhancing the analytical performance of the electrode in terms of sensitivity, linear range, and stability of potential. The optimized electrodes of types 2 and 3 exhibit a wide linear range with detection limits of 1.8 × 10⁻⁶ and 1.6 × 10⁻⁶ M, respectively. They are suitable for determination of Cu²⁺ in analytical measurements by direct potentiometry and in potentiometric titrations, within pH between 2.3 and 6.5. The electrodes are selective for Cu²⁺ over a large number of tested transition and heavy metal ions.     

Flexible polyaniline

Flexible polyaniline having excellent mechanical properties (e.g., elongation at break = 41% and tensile strength = 1.8 kg cm^?2) was prepared by electrochemical reduction of ordinary polyaniline in organic solvents. The flexibility is directly related with the polymer morphology which was definitely affected by the nature of electrolyte anion. Perchlorate or tetrafluoroborate anion were found suitable to obtain flexible polyaniline. At the same time, it is essential that the polymer so prepared should be reduced (undoped) in some suitable organic solvents before making a flexible free standing film.     

Corrosion behavior of AA2024-T3 alloy treated with phosphonate-containing TEOS

Protection from corrosion of the aluminum alloy AA2024-T3 coated with a tetraethoxysilicate (TEOS)/aminotrimethyllenephosphonic acid (ATMP) film in a 0.05-mol L⁻¹ NaCl solution was evaluated using electrochemical impedance spectroscopy, scanning electron microscopy, energy disperse spectroscopy, and atomic force microscopy. The present work investigates the influence of different pretreatment procedures of the alloy surface and the ATMP concentration on the corrosion resistance of the coated samples. The undoped sol–gel coatings did not provide adequate corrosion protection. The best corrosion protection was achieved using acetic acid pretreatment and subsequent deposition of an ATMP-modified TEOS film with an optimal concentration of 5.00 × 10⁻⁴ mol L⁻¹ in the deposition bath. The acetic acid pretreatment promotes a decrease in galvanic corrosion and the surface enrichment of aluminum favoring the metalosiloxane and the metal–phosphonic bonds with increasing likely reaction sites, thus promoting the formation of a more homogeneous and compact coating with improved resistance.     

The network gel polymer electrolyte based on poly(acrylate-co-imide) and its transport properties in lithium ion batteries

Poly (acrylate-co-imide)-based gel polymer electrolytes are synthesized by in situ free radical polymerization. Infrared spectroscopy confirms the complete polymerization of gel polymer electrolytes. The ionic conductivity of gel polymer electrolytes are measured as a function of different repeating EO units of polyacrylates. An optimal ionic conductivity of the poly (PEGMEMA₁₁₀₀-BMI) gel polymer electrolyte is determined to be 4.8 × 10^–3 S/cm at 25 °C. The lithium transference number is found to be 0.29. The cyclic voltammogram shows that the wide electrochemical stability window of the gel polymer electrolyte varies from −0.5 to 4.20 V (vs. Li/Li⁺). Furthermore, we found the transport properties of novel gel polymer electrolytes are dependent on the EO design and are also related to the rate capability and the cycling ability of lithium polymer batteries. The relationship between polymer electrolyte design, lithium transport properties and battery performance are investigated in this research.     

Improved properties of polymer electrolyte by ionic liquid PP1.3TFSI for secondary lithium ion battery

A new kind of polymer electrolyte is prepared from N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide (PP1.3TFSI), polyethylene oxide (PEO), and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI). IR and X-ray diffraction results demonstrate that the addition of ionic liquid decreases the crystallization of PEO. Thermal and electrochemical properties have been tested for the solid polymer electrolytes, the addition of the room temperature molten salt PP1.3TFSI to the conventional P(EO)₂₀LiTFSI polymer electrolyte leads to the improvement of the thermal stability and the ionic conductivity (x = 1.27, 2.06 × 10⁻⁴ S cm⁻¹ at room temperature), and the reasonable lithium transference number is also obtained. The Li/LiFePO₄ cell using this polymer electrolyte shows promising reversible capacity, 120 mAh g⁻¹ at room temperature and 164 mAh g⁻¹ at 55 °C.     

Synthesis and electrochemical properties of K-doped LiFePO4/C composite as cathode material for lithium-ion batteries

Li_1 − x K _x FePO₄/C (x = 0, 0.03, 0.05, and 0.07) composites were synthesized at 700 °C in an argon atmosphere by carbon thermal reduction method. Based on X-ray diffraction, scanning electron microscopy, and transmission electron microscopy analysis, the composite was ultrafine sphere-like particles with 100–300 nm size, and the lattice structure of LiFePO₄ was not destroyed by K doping, while the lattice volume was enlarged. The electrochemical properties were investigated by four-point probe conductivity measurements, galvanostatic charge and discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that the capacity performance at high rate and cyclic stability were improved by doping an appropriate amount of K, which might be ascribed to the fact that the doped K ion expands Li ion diffusion pathway. Among the doped materials, the Li_0.97K_0.03FePO₄/C samples exhibited the best electrochemical activity, with the initial discharge capacity of 153.7 mAh g⁻¹ at 0.1 C and the capacity retention rate of about 92% after 50 cycles at above 1 C, 11% higher than undoped sample. Remarkably, it still showed good cycle retention at a high current rate of 10 C.     

Electrochemical polymerization of nano-micro sheaf/wire conducting polymer poly[Ni(salen)] for electrochemical energy storage system

<正>The polymer of complex[Ni(salen)],(N,N'-ethylenebis(salicylideneaminato) nickel(H)),was prepared on graphite electrode by the route of linear sweep potential method.The nano-micro sheaf/wire structures of poly[Ni(salen)]have been obtained by adjusting the polymerization sweep rate of 5,20 and 40 mV·s~(-1).The polymer prepared at 20 mV·s~(-1) had nanoscaled wire structure of ca.100 nm in diameter.The good electrochemical reversibility of poly[Ni(salen)]was investigated by cyclic voltammetry and galvanostatic test in 1.0 mol/L Et_3MeNBF_4/acetonitrile solution.The initial specific gravimetric capacitance of poly[Ni(salen)]at the current density of 0.1 mA·cm~(-2) reached 270.2 F·g~(-1),however,the cycle stability needs to be improved.     

Synthesis and electrochemical characterization of aPEO-based polymer electrolytes

In this paper, the preparation and purification of an amorphous polymer network, poly[oxymethylene-oligo(oxyethylene)], designated as aPEO, are described. The flexible CH₂CH₂O segments in this host polymer combine appropriate mechanical properties, over a critical temperature range from −20 to 60 °C, with labile salt-host interactions. The intensity of these interactions is sufficient to permit solubilisation of the guest salt in the host polymer while permitting adequate mobility of ionic guest species. We also report the preparation and characterisation of a novel polymer electrolyte based on this host polymer with lithium tetrafluoroborate, LiBF₄, as guest salt. Electrolyte samples are thermally stable up to approximately 250 °C and completely amorphous above room temperature. The electrolyte composition determines the glass transition temperature of electrolytes and was found to vary between −50.8 and −62.4 °C. The electrolyte composition that supports the maximum room temperature conductivity of this electrolyte system is n = 5 (2.10 × 10⁻⁵ S cm⁻¹ at 25 °C). The electrochemical stability domain of the sample with n = 5 spans about 5 V measured against a Li/Li⁺ reference. This new electrolyte system represents a promising alternative to LiCF₃SO₃ and LiClO₄-doped PEO analogues.