Composite materials containing nanoparticulate PEDOT in a polymer electrolyte matrix containing either a Cu–Cu2+ or Fe2+–Fe3+ redox couples show rapid and reversible decreases of up to 500-fold in their electrical and microwave impedances when small DC or AC electric fields are applied across coaxial line and strip samples from their edges, which are much larger than microparticulate PEDOT composites and make signification progress in this field. The composites show large field-dependent resistances at low applied fields and good electrochemical stability.

7Li and 19F NMR linewidths and impedance spectra are reported for low-dimensional CmOn (I):LiBF4 mixtures. Data for the ionophilic polymer C18O5 is compared with that for the ionophobic C18O1 and the block copolymer C16O1O5(21%) (21mol% of C16O5). In C18O5:LiBF4 (1:1) narrow 7Li linewidths, which were observed in the liquid crystal phase above the side chain melting temperature (∼50°C), persist in the crystal down to ca. 0°C and broaden below −20°C. However, in C18O1:LiBF4 (1:0.6) narrow 7Li linewidths were also observed down to −20°C suggesting highly mobile neutral aggregates of salt since this system is non-conductive. In the copolymer C16O1O5(21%):LiBF4 (1:0.7) the linewidths were even narrower down to −70°C with weak temperature dependence. In all systems 19F linewidths were significantly broader than 7Li linewidths. The complex plane plots obtained by impedance spectroscopy exhibit characteristic minima identified with ‘grain boundary’ resistance and, following heat treatment, minima with weak temperature dependence identified with ‘internal crystal’ resistance, Ri, and conductivities, σi≥10−4Scm−1. Four-component mixtures of copolymers CmO1O5 and CmO1O4 with LiBF4 and ‘salt-bridge’ poly(tetramethylene oxide)–dodecamethylene copolymers gave conductivities of ca. 4×10−4Scm−1 at 20°C with weak temperature dependence. A novel carrier-hopping mechanism of lithium transport decoupled from side chain melting in the crystalline state is postulated.

DSC indicates that first-heating endotherms at 95 and 100–115°C in poly(tetramethylene oxide)-based polymers with LiClO4 and LiBF4, respectively, arise from the decomposition of phase-separated LiClO4·3H2O and a pre-melting transition in phase-separated LiBF4 and not from organized adducts with poly(tetramethylene oxide) as asserted by Akbulut et al. and other literature. Water in the LiClO4 system, at least (absent in freeze-dried samples), could account for higher conductivities reported by Akbulut et al. than observed by the present authors. Irreversibility of logσ versus1/T in these weakly ionophilic systems apparently arises from slow dissolution of lithium salts together with morphological changes in mixtures of the self-organising systems CmOn (I) with the ‘grain boundary bridging’ copolymer –[–(CH2)4–O–]x–(CH2)12– (II). A three-component system I:II:LiBF4 to which 9wt% of tetrahydrofuran had been purposefully added showed deterioration in conductivity compared with the system without THF addition. This suggests that solvent-inhibition of self-organization is contrary to the suggestion by Akbulut et al. that irreversible transformation to a high ambient conductivity (σ=10−4 to 10−3Scm−1) regime arises from plasticization by the 3wt% of volatiles, generated by thermal decomposition of II in a three-component mixture, that they report. The irreversible transformation to higher conductivities is also observed in systems heated to maximum temperatures between 50 and 80°C for which degradation was shown to be negligible.

Diodes composed of a nanoparticulate composite of poly(3,4-ethylenedioxythiophene) and a Cu-Cu2+ redox couple in a poly(ethylene oxide)-LiBF4 polymer-electrolyte matrix between Ag and Zr electrodes show rectifications in excess of 50000 at applied fields of 4 V These large changes are considered to arise from both rectification at the Zr/ZrO2 composite interface and from the switching of the composite material between two conductivity states by the application of a low potential field. preparation and electrochemical characterisation of these novel active devices are discussed.

The structure of two amphiphilic low-dimensional copolymer electrolytes I of similar overall composition but prepared by different synthetic procedures is described. I are copolymers of poly [2,5,8,11,14-pentaoxapentadecamethylene(5-alkyloxy-1,3-phenylene)] (CmO5) and poly[2,-oxatrimethylene(5-alkyloxy-1,3-phenylene)] (CmO1) where the alkyl side chains having m carbons are mixed dodecyl/octadecyl (50/50). 1H NMR shows that the copolymers have only 18 and 13% of CmO5 units in which LiBF4 ions are separated by Li+ encapsulation in tetraethoxy segments but molecular modelling suggests that in ionophobic CmO1 units the salt is mostly present as neutral aggregates decoupled from the polymer. Conductivities of microphase-separated mixtures with salt-bridge amphiphilic polyethers II and III of each system are similar. They have low temperature dependence over the range 20–110°C at ∼10−3Scm−1. A conduction mechanism is proposed whereby Li+ hopping takes place along rows of decoupled aggregates in an essentially block copolymer structure. Subambient measurements to −10°C gave a conductivity of 4×10−5Scm−1.

The structure of amphiphilic low-dimensional copolymer electrolytes I of similar overall composition but prepared by different synthetic procedures X and Y are described. I are copolymers of poly[2,5,8,11,14-pentaoxapentadecamethylene(5-alkyloxy-1,3-phenylene)] (CmO5) and poly[2,-oxatrimethylene(5-alkyloxy-1,3-phenylene)] (CmO1) where the alkyl side chains having m carbons are hexadecyl or mixed dodecyl/octadecyl (50/50). 1H NMR shows that the copolymers have 50% (m=16) or only 18 and 13% of CmO5 units and DSC indicates that the copolymers have ‘block’ sequencing of CmO1 and CmO5 segments. Molecular dynamics modelling indicates that in CmO5 Li+ and BF4− ions are separated by Li+ encapsulation in tetraethoxy segments but in ionophobic CmO1 units the salt is mostly present as neutral aggregates decoupled from the polymer. Conductivities of these microphase-separated mixtures with salt-bridge amphiphilic polyethers II and III of each system are similar. They have low temperature dependence over the range 20°C to 110°C at ∼10−3Scm−1. 7Li NMR linewidth measurements confirm high lithium mobilities at −20°C. A conduction mechanism is proposed whereby Li+ hopping takes place along rows of decoupled aggregates (dimers/quadrupoles) within an essentially block copolymer structure. Subambient measurements to −10°C gave a conductivity of 4×10−5Scm−1.

The amphiphilic polymers poly[2,5,8,11,14-pentaoxapentadecamethylene(5-hexadecyloxy-1,3-phenylene)] I (abbrev. C16O5), its homologues C16On, n = 1-4, and its copolymers with C16O1 have been synthesised by two Williamson procedures. Method X gives polyether-esters; method Y gives pure polyethers. DSC, optical microscopy, small-to-wide angle X-ray diffraction and complex impedance spectroscopy have been used to investigate organisation and ionic conductivities of the C16On and the C16O5-C16O1 copolymer series and their complexes with LiClO4 and LiBF4. Four-component mixtures of the latter systems (polymers I) with polyoxytetramethylene-decamethylene copolymer (II) and an octadecyl-terminated ABA block copolymer (III) (interfacial stabiliser) ('type D' systems) gave high ambient conductivities ( > or = 10(-4) S cm(-1)) with low temperature dependence. Highest conductivities (8 x 10(-4) S cm(-1) at 20 degrees C) were observed with a type D system based upon C12C18O5X.

Two Williamson procedures for the synthesis of the amphiphilic polymers poly[2,5,8,11,14-pentaoxapentadecamethylene(5-alkyloxy-1,3-phenylene)]I(abbrev. CmO5) are compared. Method X gives polyether-esters; method Y gives pure polyethers. In both, a dehydration reaction gives rise to CmO5-CmO1 copolymers. Two-phase systems of I with polyoxytetramethylene and polyoxytrimethylene copolymers (II) and LiBF(4) have been prepared with and without an interfacial stabiliser copolymer III. Highest and most stable conductivities (>5 x 10(-4) S cm(-1) at ambient) with low temperature dependence were observed with III, but I from method Y showed a tendency to phase separate at ambient.

The development of solvent-free low-dimensional polymer electrolytes intended for use in solvent-free lithium batteries operating at ambient or sub-ambient temperatures is described. The synthetic routes to the amphiphilic polymers I having 5-alkoxy-3,4-phenylene units connected with oligoethoxy segments via polyester-ether or pure polyether links (abbrev. CmOn, in = 12, 16, 18, n = 1-5) and to the copolymers CmO1-CmOn are described. The structures, thermal properties and SAXS long spacings of their complexes with lithium salts (type A) and with long chain n-alkane or alkyl side chain intercalation (type 13) are discussed. However, high ambient conductivities (10(-4)-10(-3) Scm(-1)) are observed in type C systems when a second copolymer based on polytetramethylene oxide segments (II) is incorporated as a microphase between the lamellae of I and serving as an ion bridge or "glue". DC polarization between Li electrodes also gives ambient conductivities greater than or equal toca. 10(-3) S cm(-1). In type D systems the I/II interface is stabilized by including a copolymer III, promoting high reproducibility in performance. Copolymers I of CmO1-CmO5 having CmO1 in excess give optimum conductivities with low temperature-dependence. This, together with molecular modeling, suggests uncoupled ion mobilities by hopping between small aggregates in the interlamellar spaces. (C) 2004 The Japan Chemical journal Forum and Wiley Periodicals, Inc.

Composite materials comprising microparticles of the environmentally stable conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT), a transition metal/metal salt redox couple in a solid polymer electrolyte matrix have been prepared and characterised. These materials show rapid and reversible changes in their DC and microwave impedances when small DC or AC fields are applied across them from the edges. The composites may be switched from a high impedance state to a low impedance state with the imposition of the fields for more than one thousand switching operations with little or no deterioration in performance. When the fields are removed, the initial high impedance state is restored. The extent of the change is very dependent on the choice of redox pair and also on the composition of the polymer electrolyte phase. Copper has been shown to give the largest changes in microwave impedance from 750Ohm at 0V to 5Ohm at 5V. In this paper, we present a series of waveguide results for composites containing 26wt% PEDOT together with a comparison with other conducting polymer composites, the effect of redox couple on the extent of switching and a proposed mechanism for the switching process.

The three-component low-dimensional polymer electrolyte complexes of blends of the amphiphilic helical polymer poly[2,5,8,11,14-pentaoxapentadecamethylene(5-hexadecyloxy-1,3-phenylene)] (I), the block copolymer of poly(tetramethylene oxide)-co-dodecamethylene (II) with LiClO4, LiBF4 and Li(CF3SO2)N have been studied by polarised light optical microscopy, DSC and SAXS together with AC complex impedance measurements using ITO glass, silver and lithium electrodes. In systems with LiClO4 a well-defined spherulitic morphology with lamellae of 1–3 μm in thickness were observed following heat treatment. The lamellae were shown to consist of de-blended polymer I:LiClO4 complex with polymer II forming an interlamellar ion-conducting layer. Complex impedance measurements with ITO and Ag electrodes give σ∼10−3 S cm−1 with low temperature dependence over ambient to 100 °C and Z′ versus Z″ planes featuring a new small semicircle on de-blending consistent with a Maxwell series layered dielectric system. A galvanic cell with LiCoO2 composite cathode discharged at 20 °C with 0.1 mA cm−2. In corresponding systems with LiBF4, blocks of lamellae separate from a blended matrix which give temperature-dependent AC conductivities. DC polarisation of LiBF4 based systems between Li electrodes give ambient conductivities 10−3–10−2 S cm−1 in good accord with AC impedance measurements. Long spacings from SAXS measurements indicate the I-salt occupancies in blends with the various salts, which correlates to their de-blending tendency.

The preparation and dc and microwave characterisation of a new microparticulate mixed polymeric conductor containing poly(3,4-ethylenedioxythiophene) (PEDOT) and copper metal in a poly( ethylene oxide)-Cu(BF4)(2)-LiBF4 polymer electrolyte matrix is described. The composites exhibit large, rapid and reversible changes in their microwave transmission coefficients when small dc or ac fields (5-7 V) are applied radially across annular samples (13 mm o.d.) from the edges. At 1 GHz, changes of 2 6 dB (0 V) to 15 dB (5 V) with switching speeds of less than or equal to250 ms were observed, and -2 to -12 dB at slower rates. Single cell experiments show that redox processes are confined to thin surface layers of the PEDOT particles. A mechanism for switching involving the polarisation of PEDOT particles under an applied field is proposed.

AC and DC conductivities of complexes of Li salts with the amphiphilic helical polyether poly[2,5,8,11,14-pentaoxapentadecamethylene(5-hexadecyloxy-1,3-phenylene)] (I) (Type A complexes) and blends of I with copolymers of poly(tetramethylene oxide) oligomer coupled with either — (CH2-)- (polymer IIC1) or — (CH2)12 — (IIC12) (Type C complexes) are reported. Whereas Type A complexes give reversible AC impedance plots log σ vs. 1/T plots which are ca. 10−7 S cm−1 at ambient, the Type C blends rise to ca. 10−3 S cm−1 at 100 °C and on cooling to ambient maintain this high level. In Type C systems with IIC12 this transformation is stable and permanent. Optical microscopy reveals phase separation of extensive well-organised lamellae of the Type A phase from the Type C blend following heating. Polymer II resides in thin layers in the interlamellar spaces serving to transfer ions between them. DC data at ambient temperatures for Li | I : II : Li salt | Li cells indicate conductivities 10−3 to 10−2 S cm−1 over extended periods (24 hours).

The preparation of polymer electrolyte blends of the amphiphilic helical poly[2,5,8,11,14-pentaoxapentadecarnethylene(5-a1kyloxy-1,3-phenylene)] (polymer I), a copolymer of tetrarnethylene oxide with –(CH2)12– segments (polymer II) and lithium salts, either Li(CF3SO3)2N (Li TFSI) or a 50/50 mixture of LiBF4 and LiCIO4 is described. The DC polarisation of cells Li|I:II:LiX|Li gives polymer electrolyte conductivities σ=10−4 S cm−1 at 20 °C for TFSI anions, slightly higher than complex impedance measurements (4×10−5 S cm−1) for the same system. However, conductivities ca. 10−2 S cm−1 at 30 °C are observed for the LiBF4–LiClO4 mixture. The higher results for the latter are attributed to more extensive ionic pathways. Furthermore, the use of polymer II incorporating –(CH2)12– segments gives higher results than in their absence. This is attributed to improved blending by interactions between the –(CH2)12– segments and the alkyl sidechains of I.

Recent developments in polymer electrolyte materials for lithium batteries are reviewed in this article. Four general classifications are recognized: (1) solvent-containing systems in which a liquid electrolyte solution either is fully miscible with a single-phase swollen polymer matrix (gel) or is a two-phase system in which “free” liquid occupies micropores within a swollen polymer network (hybrid), and conductivity (≥~1 mS cm^−1 at ambient temperature) is essentially independent of the polymer segmental motion (the thermal motion of segments of atoms along the backbone of a flexible polymer chain); (2) solvent-free, ion-coupled systems (typically polyether-Li salt complexes) in which both anions and cations are mobile within an amorphous, rubbery phase (conductivity ≤ 0.1 mS cm^−1 at ambient temperature); (3) “single-ion” systems with anions fixed to the polymer backbone or systems with anion mobilities reduced by incorporation within larger molecules or by associations with the chain (conductivity ≥~10^−5 mS cm^−1 at ambient temperature); and (4) decoupled systems in which ionic mobility through channeled structures involves minimal local segmental displacements (conductivity 0.12-1 mS cm^−1 at ambient temperature).

Solvent-free polymer electrolyte blends of the amphiphilic polyethoxide (I) and the polytetrahydrofuran copolymer (II) with LiClO4 or LiClO4/LiBF4 mixture have been prepared.[GRAPHICS]In II -A- is either -CH2- (IIC1) or -CH2C(=CH2)CH2- (IID4), dc measurements using Li electrodes on the cells (Li / I/II-Li salt / Li) demonstrate a 'self-tracking' process over ca. 24 h during which time conductivities increase from ca. 10(-6) to 10(-3) S cm(-1) at 25 and 30 degreesC. The de results are supported by ac impedance measurements using indium tin oxide (ITO) electrodes in which the complexes undergo transitions at ca. 90 degreesC to give a conductivity after cooling of 6 x 10(-4) S cm(-1) at 20 degreesC with low temperature dependence. Structural analysis and molecular dynamics modelling indicate that the cations occupy unimpeded helices of I and anions are located in the interhelical spaces. Mechanisms of 'tracking' involving shear-induced orientation of polymer I by polymer II and the redistribution of ions between I and II following imposition of the field are proposed. (C) 2001 Elsevier Science B.V. All rights reserved.

A solvent-free, low-dimensional polymer electrolyte blend is described demonstrating a novel process of 'self-tracking' along the field direction in DC polarisation between lithium electrodes and giving ambient DC and AC conductivities upto 10−3 S cm−1 with low temperature dependence of conduction.

LB films and bulk samples of complexes of (CF3SO2)2NLi and LiClO4 with polymers CH2OCH2- [(C6H3OR)CH2O(CH2OCH2)n−1] where R = –C16H33 or –C18H37 and n = 5 have been compared. Three-component systems incorporating equimolar proportions to the repeating unit of ‘expander' C16H33OH or C18H38 are also discussed. The laminar structures of the complexes have been modelled by molecular dynamics. The LB multilayer films (400–600 A) have been characterised using surface pressure–area isotherms, low angle X-ray scattering and impedance spectroscopy. Conductivity measurements both in the plane of the films and normal to the plane are reported and compared with measurements on bulk (100 μm) films. Temperature-independent conductivity is observed in the ‘normal-to-plane' LB measurements. We propose that a morphological transformation occurs at the first heating during which the ion-mobile interlamellar planes become oriented normal to the electrodes.