I. Cantero

Conducting polymers as positive electrodes in rechargeable lithium-ion batteries

The influence of the conditions of synthesis, such as both monomer and electrolyte concentrations, the electric potential of synthesis and temperature of work or the chosen solvent, on the properties of the polymeric material to be used as cathode of lithium-ion batteries, was studied. A similar study was performed to obtain three conducting polymers, as polypyrrole, polythiophene or poly-3-methylthiophene. Specific charges of the obtained materials, as a function of the conditions of synthesis were analysed.

Solvent effects on the charge storage ability in polypyrrole

Abstract Solvent effect on the charge storage ability of the polypyrrole have been studied in two different ways: analyzing both the ion–solvent and polymer–solvent interactions and by a multiple regression procedure. The first way was not sufficient to explain all the results obtained. By the multiple regression, influence of the four different variables of the solvents simultaneously has been obtained. Solvents having high dipole moments and low polarizability and having a high capacity to donate electrons are the best solvents among those investigated in this paper to obtain high charge storage abilities.

Conformational relaxation in conducting polymers: effect of polymer–solvent interactions

Abstract Oxidation chronoamperograms of compacted polypyrrole films allow one to study the effect of the solvent on the rate of electrochemical switching controlled by conformational relaxation processes. Experimental behaviour has been analyzed on the basis of the electrochemically stimulated conformational relaxation (ESCR) model and compared to theoretical results extracted from free volume theories in amorphous polymers

Influence of Carbon Content on LiFePO4 / C Samples Synthesized by Freeze-Drying Process

The influence of the carbon content in LiFeP0 4 /C composites synthesized by the freeze-drying method was studied by varying the citric acid (chelating agent): Fe ratio. Diminishing this ratio from 1:1 to 0.33:1 led to a gradual reduction of the carbon content from 16.1 to 7.2% wt and different morphologies. Transmission electron microscopy micrographs of the composite with the greatest carbon percentage (16%) show mainly 30 nm LiFeP0 4 particles homogeneously embedded in a carbon network. Samples containing less carbon exhibit only one type of morphology, 200-700 nm aggregates made up of an intimate mixture of LiFeP0 4 particles and carbon. Galvanostatic cycling from 2 to 4 V vs Li/Li + evidences the typical LiFePO 4 redox behavior at 3.4 V, and a second contribution at 2.65 V probably related to the carbon content. At a high rate, a good specific capacity value is observed for the nanoparticulate sample (16% wt C), whereas poorer performance is observed for low carbon content samples (11 and 7.2 wt % C). Heterogeneous and insufficient carbon covering together with phosphate particle aggregation in these latter samples can account for this behavior. Two carbon distribution models are proposed to explain different electrochemical responses. In all cases, a good capacity retention is observed after prolonged cycling.

Statistical design to optimize specific charges in polypyrrole by electrosynthesis

A design of experiments was employed to optimize the conditions of synthesis in order to electrogenerate thick polypyrrole films suitable for application as a cathode in polymeric batteries or supercapacitors. The influence of five main variables: potential of polymerization, generation time, monomer concentration, electrolyte concentration, and temperature, and their second-order interaction on the specific charge were studied and optimized through three stages. The initial stage requires the synthesis of 16 films (design matrix). Every film is weighed and checked in the background solution to obtain the stored charge and the specific charge. The resulting statistical significance shows that optimization only is possible at low potentials. In a second stage a design matrix with eight new experiments allowed the determination of the variables of synthesis affecting the specific charge and the direction of change of those variables to optimize this property. By changing the conditions of synthesis in that direction three more experiments resulted in a designed film 0.5 μm thick and 104 Ah kg -1 .

Electropolymerization of acrylamide at high current density in aqueous media

The flow of high current densities (j > 20 mA cm−2 through aqueous solutions of acrylamide and NaNO3 from platinum electrodes promotes the generation of polyacrylamide. The polymer product remains soluble. The kinetics of the process was followed by gravimetric determination of polymer production. A straightforward polymerization occurs at times longer than 15 min. The empirical kinetics followed through the second region was proportional to [acrylamide]12[NaNO3]−34 and decreases linearly when the current density increases. The activation energy of the overall process was 79 k mol−1. These results, including the variations of the average viscosimetric molar mass of samples, the number of electrons consumed to generate a molecule of polymer and the number of monomeric units incorporated in the polymer per consumed electron, as a function of the chemical variables of synthesis, can be explained through the simultaneous presence of monomer, water and nitrate ion oxidation on the electrode. Gel formation occurs around the electrode for short times of current flow.

EAP as multifunctional and biomimetic materials

Polyconjugated and electroactive materials are, when used for electrochemical devices, soft, wet and complex materials. Polymeric chains, water and inorganic ions are the main constituents, mimicking the composition of those organs constituents of the living creatures. During reverse electrochemical reactions, those electroactive polymers change, under control of the consumed charge: volume, color, stored charge, composition, porosity, etc. Those changes allow the design of devices such as artificial muscles, smart skins, electric organs, nervous interfaces, smart medical dosage, smart membranes, all of them working under electrochemical control. This multifunctionality will be reviewed.

GREENLION Project: Advanced Manufacturing Processes for Low Cost Greener Li-Ion Batteries

GREENLION is a Large Scale Collaborative Project within the FP7 (GC.NMP.2011-1) leading to the manufacturing of greener and cheaper Li-Ion batteries for electric vehicle applications via the use of water soluble, fluorine-free, high thermally stable binders, which would eliminate the use of VOCs and reduce the cell assembly cost. The project has 6 key objectives: (i) development of new active and inactive battery materials viable for water processes (green chemistry); (ii) development of innovative processes (coating from aqueous slurries) capable of reducing electrode production cost and avoid environmental pollution; (iii) development of new assembly procedures (including laser cutting and high temperature pre-treatment) capable of substantially reduce the time and the cost of cell fabrication; (iv) lighter battery modules with easier disassembly through eco-designed bonding techniques; (v) waste reduction, which, by making use of the water solubility of the binder, allows the extensive recovery of the active and inactive battery materials; and (vi) development of automated process and construction of fully integrated battery module for electric vehicle applications with optimized electrodes, cells, and other ancillaries. Achievements during the first 18 months of the project, especially on materials development and water-based electrode fabrication are reported herein.

Development of Novel Solid Materials for High Power Li Polymer Batteries (SOMABAT). Recyclability of Components

SOMABAT aims to develop more environmental friendly, safer and better performing high power Li polymer battery by the development of novel breakthrough recyclable solid materials to be used as anode, cathode and solid polymer electrolyte, new alternatives to recycle the different components of the battery and life cycle analysis. This challenge is being achieved by using new low-cost synthesis and processing methods in which it is possible to tailor the different properties of the materials. Development of different novel synthetic and recyclable materials based carbon based hybrid materials, novel LiFePO4 and LiFeMnPO4 based nanocomposite cathode with a conductive polymers or carbons, and highly conductive polymer electrolyte membranes based on fluorinated matrices with nanosized particles and others based on a series of polyphosphates and polyphosphonates polymers respond to the very ambitious challenge of adequate energy density, lifetime and safety. An assessment and test of the potential recyclability and revalorisation of the battery components developed and life-cycle assessment of the cell will allow the development of a more environmental friendly Li-polymer battery in which a 50 % weight of the battery will be recyclable and a reduction of the final cost of the battery up to 150 €/kWh is achievable. The consortium is made up of experts in the field and is complementary in terms of R&D expertise and geographic distribution.

Artificial muscles working in aqueous solutions or in air

Macroscopic electrochemomechanical devices formed by bilayers or triple layers between electroactive polymers and a non conducting, adherent and flexible poplymer, able to describe angular movements in liquid electrolytes under electrochemical control are presented. Using a polymeric electrolyte, able to conduct ions, sandwiched between two polypyrrole layers, a muscle working in air was constructed. Any of those devices work under electrochemical control of the conformational changes occurring in polymeric chains. They act simultaneously as actuators and sensors. Similitudes with natural muscles are underlined.