P. Prosperi

Study of the electrochromism of polypyrrole/dodecylsulfate in aqueous solutions

Abstract Galvanostatic synthesis of polypyrrole on indium tin oxide (ITO)-coated glass electrodes at low current density in an aqueous solution containing sodium dodecylsulfate produces thin electrochromic films. The white light film transmittance passes from 50% to 98% during cycling from −0.9 to 0.6 V vs sce with color changes from brown to violet and finally to yellow. Absorption spectra at different potentials and change of transmittance at different wavelengths as a function of potential are furnished. The polypyrrole/dodecylsulfate films show a higher cyclability than polypyrrole obtained with other inorganic counter-ions.

Characteristics of electrochemically synthesized polymer electrodes in lithium cells—II. Polythiophene

The characteristics of electrochemically synthesized polythiophene electrodes have been examined in view of their application in rechargeable lithium, organic electrolyte batteries. The kinetics of the electrochemical doping process of polythiophene in LiClO4-propylene carbonate electrolyte are quite fast, especially for polymers grown from the 2,2′-dithiophene dimer. The polythiophene electrodes behave very satisfactorily in terms of charge-discharge efficiency and cyclability. However, also this type of electrodes seems to be affected by the self-discharge processes commonly experienced by semiconducting polymers in lithium, organic electrolyte batteries.

Characteristics of electrochemically synthesized polymer electrodes in lithium cells—IV. Effects of the synthesis conditions on the performance of polypyrrole

Abstract The performance of polymer electrodes in lithium cells strongly depends on the conditions of electrosynthesis. In this work we describe the role of current density and of total charge of preparation on the cyclability of polypyrrole electrodes in a 1 M LiClO 4 solution in propylene carbonate.

Properties of electrochemically synthesized polymer electrodes—IX. The effects of surfactants on polypyrrole films

Abstract The electrochemical behaviour of polypyrrole film electrodes synthesized in the presence of sodium dodecylsulphate, has been investigated by cyclic voltammetry and frequency response analysis. The results indicate that the surfactant anion favours redox processes which are faster and more reversible than those associated to usual polypyrrole electrodes. The modified, surfactant-based polypyrrole electrodes have been successfully used in lithium, organic electrolyte batteries having improved power density and cyclability characteristics.

Kinetics of semiconducting polymer electrodes in lithium cells

Abstract Recently, there has been a growing interest in semiconducting polymers as electrodes in rechargeable lithium batteries. A number of polymers have been

Properties of electrochemically synthesized polymers—V. The polymer electrode/polymer electrolyte interface

Abstract A solid-state lithium-polypyrrole cell having a polymeric electrolyte based on the lithium perchlorate—poly(ethylene oxide) complex, has been assembled. Results based on cyclic voltammetry, frequency response analyses and charge—discharge cycles, show that the polymer/polymer interface is characterized by favourable kinetics in the temperature range where the conductivity of the electrolyte is sufficiently high. Therefore using proper cell design, the solid-state polymeric systems may be considered for the realization of interesting devices, such as ultrathin batteries, electrochromic displays and thermal sensors.

Electrochemical stability of electrosynthesized heterocyclic semiconducting polymers as cathode-active materials in advanced batteries

Abstract The data from a comparative study of cyclability and stability in LiClO 4 -propylene carbonate of electrosynthesized polymers: polypyrrole, polythiophene, polydithienothiophene and polythienothiophene are reported and discussed in view of their use as cathode-active materials in lithium-organic electrolytic batteries. Whereas cyclability data suggest that all these polymers, despite performance differences, could be used as cathode-active materials in rechargeable lithium batteries, the stability data seem to indicate, however, that polypyrrole is much more stable than the other polymers in an electrolytic medium of interest in the development of rechargeable lithium batteries.

Polymer electrolytes based on poly-phosphazene with pendant 12-crown-4 groups and monovalent salts

A series of poly-phosphazenes with pendant 12-crown-4 ether have been prepared starting from poly-bis(1,1,1-trifluoroethoxy)-phosphazene; the ring is spaced from the polymer backbone by zero or six methylene units. The former system has been complexed with lithium salt, the latter with lithium, sodium and potassium salts and the ionic conductivity, as a function of temperature, has been measured at different salt concentrations. The highest ionic conductivity has been obtained with the system having the six methylene flexible spacer complexed with LiBF4. The conductivity σ reached the value of 10−5 S cm−1 at room temperature.

Electrochemical characterization of a polymer/polymer rechargeable lithium solid-state cell

Abstract The characteristics of solid-state lithium cells, using (PEO) 20 LiClO 4 as electrolyte and the electrosynthesized polymers polypyrrole, polybithiophene and polydithienothiophene as positive electrodes, were investigated by cyclic voltammetry, charge-discharge galvanostatic cycles and a.c. impedance spectroscopy. The experimental data suggest that solid-state polymeric systems can be employed in ultrathin batteries at 70°C operating temperature.

Polymer electrolytes based on crosslinked silylated poly-vinyl-ether and lithium perchlorate

Abstract Poly-vinylethers (PVE) containing triethoxy-silyl groups in the side-chains were synthesised and crosslinked during membrane processing in the presence of LiClO 4 . The electrolytic membranes had excellent dimensional stability and showed promising ionic conductivity, approaching the value of 10 −5 S / cm at 25°C. The effect of the side chain length, in term of EO units, and of the salt concentration on conductivity was also investigated.