Ionic conductivity and electrochemical stability of poly(methylmethacrylate)-poly(ethylene oxide) blend-ceramic fillers composites

The role of inorganic ceramic fillers namely nanosized Al₂O₃ (15-25 nm) and TiO₂ (10-14 nm) and ferroelectric filler SrBi₄Ti₄O₁₅ (SBT CIT) (0.5 μm) synthesized by citrate gel technique (CIT) on the ionic conductivity and electrochemical properties of polymer blend 15 wt% PMMA+PEO₈:LiClO₄+2 wt% EC/PC electrolytes were investigated. Enhancement in conductivity was obtained with a maximum of 0.72×10⁻⁵ S cm⁻¹ at 21 °C for 2 wt% of SrBi₄Ti₄O₁₅ (SBT CIT) composite polymer electrolyte. The lithium-ion transport number and the electrochemical stability of the composite polymer electrolytes at ambient temperature were analyzed. An enhancement in electrochemical stability was observed for polymer composites containing 2 wt% of SrBi₄Ti₄O₁₅ (SBT CIT) as fillers.     

Thermal history — conductivity relationship in lithium salt-poly (ethylene oxide) complex polymer electrolytes

A.C. conductivity measurements on a number of lithium salt-poly(ethylene oxide) (PEO) complex polymer electrolytes have been correlated with the results of D.S.C. analysis. An enhancement in the conductivity of compositions with O:Li ratios of greater than 6:1 on annealing at above 150°C was attributed to the melting of the polymer crystalline phase and the retention of an amorphous polymer structure in the electrolyte on cooling down to the crystallisation temperature of the pure PEO phase.     

Ionic conductivity of electrolytes based on star-branched poly(ethylene oxide) with high concentration of lithium salts

Electrolytes based on star-branched poly(ethylene oxide) with lithium bis(trifluoromethanesulfone)imide LiTFSI and lithium iodide salts were prepared by casting from solution. The electrical properties of electrolytes subjected to various heating and cooling runs were studied by impedance spectroscopy and impedance spectroscopy simultaneous with optical microscope observation. Differential scanning calorimetry was used for additional characterization. The results indicate that in electrolytes with high content of salt, values of ionic conductivity comparable to that of dilute electrolytes can be achieved. Moreover, electrolytes with high amount of salt seem to show weaker temperature dependence of conductivity. Promising results in terms of ionic conductivity were obtained for mixture of LiTFSI and lithium iodide. A few problems which may decrease the performance of studied system as a solid electrolyte were also identified, from which changes of physical properties of samples subjected to thermal cycles and aging seem to be the most important ones.     

Ionic conductivity of polymer electrolyte membranes based on polyphosphazene with oligo(propylene oxide) side chains

A polyphosphazene [NP(NHR)₂]_n with oligo[propylene oxide] side chains − R = –[CH(CH₃)–CH₂O]_m–CH₃ (m = 6 – 10) was synthesized by living cationic polymerisation and polymer-analogue substitution of chlorine from the intermediate precursor [NPCl₂]_n using the corresponding primary amine RNH₂. The polymer had an average molecular weight of 3.3 × 10⁵ D. Polymer electrolytes with different concentrations of dissolved lithium triflate (LiCF₃SO₃) were prepared. Mechanically stable polymer electrolyte membranes were formed using UV radiation induced crosslinking of the polymer salt mixture in the presence of benzophenone as photoinitiator. The glass transition temperature of the parent polymer was found to be − 75 °C before cross linking. It increases after crosslinking and with increasing amounts of salt to a maximum of − 55 °C for 20 wt.% LiCF₃SO₃. The ionic conductivity was determined by impedance spectroscopy in the temperature range 0–80 °C. The highest conductivity was found for a salt concentration of 20 wt.% LiCF₃SO₃: 6.5 × 10^− 6 S·cm^− 1 at 20 °C and 2.8 × 10^− 4 S cm^− 1 at 80 °C. The temperature dependence of the conductivities was well described by the MIGRATION concept.     

Characterization of poly(ethylene oxide) copper salt polymer electrolytes

The physico-chemical and electrochemical properties of a new class of polymer electrolytes formed by complexes of poly(ethylene oxide) and copper trifluorosulphonate salts have been investigated. The results suggest that these electrolytes are good copper ion conductors. Under particular conditions of concentration and temperature, and apparent electronic transport has also been evidenced.     

Ionic conductivity of gadolinium-doped barium praseodymium oxide

To clarify the ionic conduction of Ba(Pr_0.6Gd_0.4)O_3−α, the electrical conductivity was measured in moist air and hydrogen atmospheres. The ionic transport number was estimated by a steam concentration cell, a hydrogen permeation cell, and a fuel cell. Temperature dependence of the conductivity in a moist air atmosphere differed from that in a moist H₂ atmosphere. The conductivity under reducing conditions increases with time according to the crystal structure change of Ba(Pr_0.6Gd_0.4)O_3−α due to oxygen loss in the lattice site. Under moist air conditions, the dominant conduction species in the Ba(Pr_0.6Gd_0.4)O_3−α electrolyte were mainly holes. However, the species changed into proton, oxide ion and hole by means of structure change in a reducing atmosphere. It was considered that the ionic conduction occurred due to the crystal structure change. It was predicted that this peculiarity of the conductivity of barium praseodymium oxide influenced the nonstoichiometric behaviour of Pr in the crystal structure.     

Microscopic investigation of ionic conductivity in alkali metal salts-poly(ethylene oxide) adducts

We present conductivity, N.M.R. and D.S.C. measurements in two P(EO) complexes : P(EO) ₈LiCF₃SO₃ and P(EO) ₁₀NaI. From N.M.R. experiments, we deduce the respective amount of crystalline and elastomeric phases at all temperatures, as well as the salt concentration in these various phases. The elastomeric phase is shown to be responsible of the ionic conductivity at all temperatures, and to be very dilute (n ? 25 just above the pure P(EO) melting point. The high melting salt-rich complexes are found surstoechiometric (n ? 3.5). The various factors affecting the temperature dependence of the conductivity are discussed, as well as the kinetics problems.     

Stability domain of a complexed lithium salt-poly(ethylene oxide) polymer electrolyte

The redox stability domain of a polyethylene oxide-lithium trifluoromethanesulphonate polymer electrolyte has been investigated using low-sweep-rate voltammetry, in the range 100–170°C. Below 140°C, its voltage stability window is in excess of 3.3 volts, making it a candidate for use with practical electrochemical couples. The electrolyte is not, however, a pure cation conductor, and problems associated with the observed significant anion mobility must be overcome in order to improve the polymer's suitability as a solid-state electrolyte for battery applications.     

A phosphate additive for poly(ethylene oxide)-based gel polymer electrolytes

The influence of an organophosphosphate additive on poly(ethylene oxide) lithium bis(trifluoromethylsulfonyl)imide-based gel polymer electrolytes for secondary lithium battery applications is described. Tris(2-(2-methoxyethoxy)ethyl)phosphate, is compared to the well known gel-battery component, propylene carbonate, through a study of complex impedance analysis, differential scanning calorimetry, and limiting oxygen index combustion analysis. The conductivities of the gels at low concentrations of tris(2-(2-methoxyethoxy)ethyl)phosphate (1.9–4.2 mol%) are higher to those of propylene carbonate-based systems with the same concentration. Despite micro-phase separation at high concentrations of tris(2-(2-methoxyethoxy)ethyl)phosphate (7.0–14.9 mol%), the conductivities remain comparable to systems that use propylene carbonate. The addition of tris(2-(2-methoxyethoxy)ethyl)phosphate to poly(ethylene oxide) gives increased fire retardance, while the addition of propylene carbonate to poly(ethylene oxide) results in increased flammability.     

Lithium ion-poly (ethylene oxide) complexes. I. Effect of anion on conductivity

The ionic conductivities of a series of lithium salt-poly (ethylene oxide) complexes have been studied from ambient temperature to approximately 400 K. Plots of the variation of conductivity with temperature indicate a transition in behaviorr between 330–360 K. The activation energies in the high temperature regime vary from 0.16 eV (LiH₂PO₄) to 1.45 eV (LiNO₃) and in the low temperature regime from 0.86 eV (LiBF₄) to 2.47 eV (LiH₂PO₄). Conductivity values for the salts tested also exhibits wide variation. The lowest measured conductivity was 10^?9 S/cm and the highest was 10^?4 S/cm. The anion plays an important role in the total measured conductivity. Salts with oxygen-containing anions form complexes with an apparent higher conductivity when the sample is vacuum dried. This suggets hydrogen bonding with residual water in the polymer impeding anionic mobility. In one of the salt-complexes (LiBF₄) residual water and thermal history, were shown not to significantly affect conductivity.     

Effect of fillers on magnesium–poly(ethylene oxide) solid polymer electrolyte

A solid polymer electrolyte (SPE) film consisting of poly(ethylene oxide) (PEO) with magnesium chloride as electrolytic salt and B₂O₃ as the filler has been prepared by solution casting technique. The polymeric film was flexible and self-standing with proper mechanical strength and studied for application in a solid-state rechargeable magnesium battery. The interactions between the filler and PEO chains are studied by differential scanning calorimeter and Fourier transform infrared techniques. Composition of SPE is optimized, and maximum conductivity is obtained at 2 wt% B₂O₃. Filler seems to increase the number of free magnesium cations by decoordinating the bond between magnesium cations and ether oxygen of PEO. Cyclic voltammetry results show the reversible capability of magnesium electrode. Solid-state magnesium cell employing magnesium anode, SPE, and manganese oxide was assembled, and its open circuit voltage is found to be 1.9 V.     

Direct-current conductivity of poly(ethylene terephthalate)

There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.     

Electrospun nanofibers of poly(ethylene oxide)/teraamino-phthalocyanine copper(II) hybrids and its photoluminescence properties

Poly(ethylene oxide)/teraamino-phthalocyanine copper (II) (PEO/(NH₂)₄PcCu) hybrid nanofibers with a diameter of 200-300 nm were prepared by electrospinning technique. The hybrid nanofibers membrane was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis), and photoluminescence (PL), respectively. The results indicated that (NH₂)₄PcCu molecule was successfully embedded in the one-dimensional hybrid nanofibers via chemical interaction between PEO and (NH₂)₄PcCu. The PL results showed that the PEO/(NH₂)₄PcCu hybrid nanofibers had an intense emission at about 450 nm. A possible PL mechanism was proposed accordingly.     

Ion and polymer chain motion in a superionic sodium-poly (ethylene oxide) complex

Magnetic resonance measurements have been performed on the ion conducting complex poly(ethylene oxide)_4.5NaClO. Low temperature²³Na NMR spectra suggest a highly symmetric environment for the Na-ions as evidenced by the absence of quadrupole broadening. Proton spin-lattice relaxation measurements provide an estimate of ~4×10^?10 sec for the polymer chain motional correlation time at T = 69C. Correlation times of tumbling paramagnetic probe molecule have been extracted from EPR spectra of¹⁵N-enriched TANOL-doped complex. Changes in polymer chain mobility above T = 120C are inferred from the results and may be consistent with previous scanning calorimetry measurements.     

Ionic conductivity studies of 49% poly(methyl methacrylate)-grafted natural rubber-based solid polymer electrolytes

The potential of 49% poly(methyl methacrylate)-grafted natural rubber (MG49) as a solid polymer electrolyte film in rechargeable batteries system were explored. The flat, thin, and flexible films were prepared by solution casting technique. The ionic conductivity was investigated by alternating current impedance spectroscopy. The highest conductivity of 2.3 × 10⁻⁷ Scm⁻¹ was obtained at 20wt.% of LiBF₄ salts content, while 4.0 × 10⁻⁸ Scm⁻¹ was obtained at 15wt.% LiClO₄ salts loading. The observation on structure performed by X-ray diffraction shows the highest conductivity appears at amorphous phase.     

Effects of preparation method on properties of lithium salt-poly(ethylene oxide) polymer electrolytes

The effects of using different sources of precursor poly(ethylene oxide) (PEO) and acetonitrile solvent on the physical and electrochemical properties of lithium salt-PEO polymer electrolytes were investigated. Although no differences were found due to the use of different types of PEO, the purity of the acetonitrile solvent was found to be critical in controlling the properties of the polymer product. Acetonitrile of nominally relatively low purity produced polymer electrolytes exhibiting largely crystalline type behaviour while the use of nominally high purity solvents gave polymers which were apparently completely amorphous at temperatures above about 50°C. Transport number measurements gave values for the lithium ions of 0.4 at 132°C for the largely crystalline materials and 0.3 at 112°C for the amorphous polymers. Analysis of the acetonitrile solvents revealed the presence of water in the nominally high purity grades and it has been confirmed that water contamination is responsible for the production of the low melting temperature form of the polymer complex.     

Alkali metal ion-poly (ethylene oxide) complexes. II. Effect of cation on conductivity

Complexes of alkali metal salts with various polymers have for some time been recognized as fast ionic conductors. Polymer electrolyte fast ion conductors are currently under consideration for use in high energy density electrochemical cells. In order to aid in our understanding of the mechanism of ionic conductivity we have examined systematically complexes of poly(ethylene oxide) (PEO) with the alkali metal salt series of Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ with both tetraflouroborate (BF₄^-) and trifluoromethanesulfonate (CF₃SO₄^-) anions. The ratio of monomer to salt was 10:1 in all cases. Complex impedance measurements were made on all samples in the temperature range 40°–125°C. With CF₃SO₄^- as the anion a definite trend was apparent with the smallest cation Li⁺ being the worst conductor and Cs⁺, the largest cation, being the best. When BF₄^- salts are used, the Na⁺ complex is found to be the best conductor and Rb⁺ the worst. This study, in connection with our earlier studies, has shown that synergy between cation and anion in the polymer matrix is an important consideration in determining the ionic conductivity.     

离子液体中聚氧化乙烯(PEO)相变过程中的氢键效应

我们把Flory-Huggins模型推广应用到聚合物/离子液体体系,研究聚氧化乙烯(PEO)在离子液体[EMIM][BF_4]中相变过程中的氢键效应,理论模型考虑了三种类型氢键(Ⅰ型:PEO-[EMIM]~+氢键,Ⅱ型:PEO-[BF_4]~-氢键和Ⅲ型:[EMIM]~+-[BF_4]~-氢键)的形成,分析了三种类型的氢键分数随温度、 PEO体积分数的变化.研究发现,三种类型的氢键分数随温度的升高而减少.在较小PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数轻微地减小;在较大PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数急剧减少.Ⅲ型氢键分数随着PEO体积分数的增加而急剧降低.由于三种氢键效应,第二维里系数A_2随温度的增加而减小.通过计算分析不同分子量的PEO在[EMIM][BF_4]中的相图发现,在PEO体积分数较低的条件下,Ⅰ型、Ⅱ型和Ⅲ型氢键是PEO相变的主要驱动力;在PEO体积分数较高的条件下,Ⅰ型和Ⅱ型氢键在PEO相变过程中起到主导作用.     

Morphology and conductivity of electrolytes based on poly(ethylene oxide) - Eu(ClO4)3 films

Solid polymer electrolytes based on a poly(ethylene oxide), (PEO), host have been prepared using the solvent casting method and characterized by conductivity measurements and thermal analysis. The observed ionic conductivity of the novel system based on PEO and europium perchlorate was similar to that of other electrolytes based on the same polymer host with a different trivalent guest species [1]. The presence of the perchlorate anion widened the composition range of amorphous behaviour but limited the thermal stability of the electrolytes produced. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997