Alberto Zanelli

Polymer Selection and Cell Design for Electric‐Vehicle Supercapacitors

Supercapacitors are devices for applications requiring high operating power levels, such as secondary power sources in electric vehicles (EVs) to provide peak power for acceleration and hill climbing. While electronically conducting polymers yield different redox supercapacitor configurations, devices with the n-doped polymer as the negative electrode and the p-doped polymer as the positive one are the most promising for EV applications. Indeed, this type of supercapacitor has a high operating potential, is able to deliver all the doping charge and, when charged, has both electrodes in the conducting (p- and n-doped) states. This study reports selection criteria for polymer materials and cell design for high performance EV supercapacitors and experimental results of selected polymer materials.

Supercapacitors Based on Composite Polymer Electrodes

The cyclability performance of several composite polymer electrodes based on poly(thiophene) (pTh), poly(3-methylthiophene) (pMeT), and poly[3-(4-fluorophenyl)thiophene] (pFPT), carbon, and a binder is reported. These composites were tested for use as positive and negative electrodes in supercapacitors for electric vehicle (EV) applications. The pTh composites were characterized for use as a positive electrode, the pFPT as negative, and the pMeT as both positive and negative electrode. Different types of symmetric and unsymmetric composite polymer supercapacitors were developed and characterized in propylene carbonate-tetraethylammonium tetrafluroborate electrolyte by several thousand deep, galvanostatic charge-discharge cycles at selected currents to restrict the discharge time to EV-suitable values (<100 s). The best device as to specific energy and power was the unsymmetric pMeT/pTh composite supercapacitor.

An electrochromic device combining polypyrrole and WO3—I. Liquid electrolyte

Abstract In this work we assembled an electrochromic device using as active materials an organic conductive polymer and a transition metal oxide. We studied the materials used to assemble the device separately, and in complete devices. These materials were: polypyrrole doped with dodecylsulfate and tungsten oxide. The substrates used were glass slides coated with tin doped indium oxide, and the electrolyte was a propylene carbonate solution of lithium perchlorate. We adjusted the charge balance and the chromatic contrast of the devices by controlling the thickness of the polypyrrole films. To illustrate the results obtained, we describe two devices with different polypyrrole film thicknesses. The chromatic contrast in the visible and near-infrared wavelength range is 40% and the electrical and optical properties of the devices remain unchanged after 10 4 double potential chronoamperometric steps.

An electrochromic device combining polypyrrole and WO3 II: solid-state device with polymeric electrolyte

Abstract In this work we describe the assembling of a solid-state electrochromic device using, as active materials, an organic conductive polymer and a transition metal oxide. The optically active materials were dodecylsulfate doped polypyrrole and tungsten oxide. The substrates used were glass slides coated with tin-doped indium oxide and the solid elastomeric electrolyte was the copolymer of ethylene oxide and epichlorohydrin containing lithium perchlorate. Initially, we studied separately the materials used to assemble the device and, in sequence, we assembled and characterized the complete devices. The thickness of the polypyrrole and the electrolyte films were varied to obtain the highest chromatic contrast, stability over a high number of redox cycles, and short response times. The characterizations were made by spectroelectrochemistry using the techniques of cyclic voltammetry and chronoamperometry. To illustrate the results obtained, we described two devices with different polypyrrole and electrolyte film thicknesses. The chromatic contrast in the visible and near-infrared wavelength range is 30% and the electric and optical properties of the devices remain unchanged after 1.5×10 4 double potential chronoamperometric steps.

Reliability of lithium batteries with crosslinked polymer electrolytes

Polymer electrolyte films were prepared by chemical crosslinking of polyethylene glycol 2000 (PEG) containing LiSO3CF3 or Li[(SO2CF3)2N]; polyethylene glycol dimethylether 500 (PEGDME) was also added to a PEG-LiSO3CF3 electrolyte. The electrochemical properties of these three electrolytes were investigated for ionic conductivity, electrochemical stability window, steady state current fraction, interface resistance and lithium/electrolyte interface stability. Furthermore, we tested prototype Li cells with a LiMn2O4 composite cathode to ascertain the effective viability of these electrolytes in solid-state Li batteries. The Li[(SO2CF3)2N] salt in the crosslinked electrolyte presents a steady-state current fraction too low for battery application, while the addition of PEGDME improves conductivity, interface resistance and battery performance.

Graphene transistors via in situ voltage-induced reduction of graphene-oxide under ambient conditions.

Here, we describe a simple approach to fabricate graphene-based field-effect-transistors (FETs), starting from aqueous solutions of graphene-oxide (GO), processed entirely under ambient conditions. The process relies on the site-selective reduction of GO sheets deposited in between or on the surface of micro/nanoelectrodes. The same electrodes are first used for voltage-induced electrochemical GO reduction, and then as the source and drain contacts of FETs, allowing for the straightforward production and characterization of ambipolar graphene devices. With the use of nanoelectrodes, we could reduce different selected areas belonging to one single sheet as well.

Thienopyrrolyl dione end-capped oligothiophene ambipolar semiconductors for thin film- and light emitting transistors

The design, synthesis and structure-property investigation of a new thienopyrrolyl dione substituted oligothiophene material showing reduced band gap energy, low lying LUMO energy level and ambipolar semiconducting behaviour is described.

Improved composite materials for rechargeable lithium metal polymer batteries

Abstract The performance of several polymer electrolytes for lithium metal batteries for electric vehicle applications are reported. The best performing electrolyte is the composite PEO 20 LiCF 3 SO 3 –γLiAlO 2 , which was prepared by a solvent-free procedure. It showed coulombic efficiency values of the lithium deposition–stripping process of 94%–96%. Electrochemical tests of lithium polymer battery (LPB) prototypes based on a 3 V LiMn 2 O 4 composite cathode material laminated together with the PEO 20 LiCF 3 SO 3 –γLiAlO 2 electrolyte gave promising results for electric vehicle applications. Even under non-optimized battery design, the prototypes delivered, at the C/3 rate and at 94°C, 40%–30% of theoretical capacity over 100 charge–discharge cycles.

Electrochromic devices: A comparison of several systems

Abstract The great variety of colour contrast achieved with electronically conducting polymers is the most significant characteristic of this class of ion-insertion organic materials. The performance of selected electrochromic devices based on electronically conducting polymers, with organic or inorganic materials as optically passive or electrochromic in complementary mode counter-electrodes, is reported and the advantages and drawbacks of each system discussed.

Poly(3-buthyl-co-3,4-dibuthylthiophene)s: synthesis and electrochromic characterization

Abstract We have prepared a series of soluble, processable copolymers containing both 3-buthylthiophene and 3,4-dibuthylthiophene units in well defined percentages. The modification of the copolymer composition produces materials with various π-electron conjugation length and with diverse electrochromic properties tested for applications in electrochromic devices.