Fabrication of high-performance dual carbon Li-ion hybrid capacitor: mass balancing approach to improve the energy-power density and cycle life

Most lithium-ion capacitor (LIC) devices include graphite or non-porous hard carbon as negative electrode often failing when demanding high energy at high power densities. Herein, we introduce a new LIC formed by the assembly of polymer derived hollow carbon spheres (HCS) and a superactivated carbon (AC), as negative and positive electrodes, respectively. The hollow microstructure of HCS and the ultra large specific surface area of AC maximize lithium insertion/diffusion and ions adsorption in each of the electrodes, leading to individual remarkable capacity values and rate performances. To optimize the performance of the LIC not only in terms of energy and power densities but also from a stability point of view, a rigorous mass balance study is also performed. Optimized LIC, using a 2:1 negative to positive electrode mass ratio, shows very good reversibility within the operative voltage region of 1.5-4.2V and it is able to deliver a specific cell capacity of 28mAh(-1) even at a high current density of 10Ag(-1). This leads to an energy density of 68Wh kg(-1) at an extreme power density of 30kWkg(-1). Moreover, this LIC device shows an outstanding cyclability, retaining more than 92% of the initial capacity after 35,000 charge-discharge cycles.Spanish Ministry of Economy and Competiveness (MINECO/FEDER) (RTI2018-096199-B-I00) and the Basque Government (Elkartek 2018) are acknowledge for the financial support of this work. We also thank Maria Echeverria and Maria Jauregui for the acquisition of the TEM images and the XRD patterns, respectively

Charge carrier transport and contact selectivity limit the operation of PTB7-based organic solar cells of varying active layer thickness

In this work we study the different electrical loss pathways occurring during the operation of bulk heterojunction solar cells by using a variety of electrical and optical characterization techniques beyond the current density–voltage curve (J–V): Impedance Spectroscopy (IS), Charge Extraction (CE) and Transient Photovoltage (TPV). Two sets of devices are analyzed: the first is based on the donor polymer P3HT, known to provide efficient cells using thick active layers (i.e. 270 nm), and the recently developed PTB7 which offers maximum efficiencies for devices with thinner layers (i.e. 100 nm). Devices fabricated with P3HT:PC60BM are not limited by transport of carriers and large active layer thickness may be used. Importantly, increasing the active layer thickness does not modify the contact selectivity. This is supported by analysis of the diode curve measured in the dark (similar leakage currents) and by capacitance–voltage measurements (similar fullerene content covering the cathode). Under these conditions the current density curve under illumination is mainly defined by the recombination processes taking place in the bulk of the active layer. In contrast, transport of carriers and contact selectivity are both limiting factors for the PTB7:PC60BM system. In this case, best efficiencies are obtained with a low active layer thickness and a high fullerene ratio. Reduced active layer thickness minimizes undesired electrical resistances related to carrier transport through the bulk of the active layer. High fullerene content enhances the amount of fullerene molecules at the cathode leading to decreased leakage currents. Then, the overall device efficiency will be a combination of the recombination kinetics in the bulk of the active layer, undesired resistance to transport of carriers and leakage current present due to low selectivity of the contact. The use of additives has also been explored which enhances charge generation and extraction. Overall, this work provides a comprehensive guide on how to interpret results obtained from some of the most widely used optoelectronic techniques employed to analyse operating devices

Graphene as Vehicle for Ultrafast Lithium Ion Capacitor Development Based on Recycled Olive Pit Derived Carbons

Herein we report a series of lithium ion capacitors (LICs) with extraordinary energy-to-power ratios based on olive pit recycled carbons and supported on graphene as a conducting matrix. LICs typically present limited energy densities at high power densities due to the sluggish kinetics of the battery-type electrode. To circumvent this limitation, the hard carbon (HC) was embedded in a reduced graphene oxide (rGO) matrix. The addition of rGO into the negative electrode not only forms a 3D interpenetrating carbon network but also wraps HC particles, facilitating ion diffusion and enhancing the electronic conductivity notably at high power densities. Electrochemical impedance spectroscopy (EIS) analysis reveals that charge-transfer resistance at electrode-electrolyte interphase and the charge-transport resistance within the electrode are considerably lower in the presence of rGO. In addition, charge-transport resistance remains constant upon cycling even at increasing current densities. Capacity gain at high current densities, owing to the reduction of the electrode resistance, triggers the overall LIC performance, allowing for the assembly of an ultrafast LIC delivering up to 200 Wh kg(AM)(-1) at low power rates and 100 Wh kg(AM)(-1). (C) The Author(s) 2019. Published by ECS.We thank the European Union (Graphene Flagship, Core 2, grant number 785219), the Spanish Ministry of Science and Innovation (MICINN/FEDER) (RTI2018-096199-B-I00) and the Basque Government (Elkartek 2018) for the financial support of this work. M. Arnaiz thanks the Spanish Ministry of Science, Innovation and Universities for her FPU pre-doctoral fellowship (FPU15/04876)

Metodología de transformación digital para incrementar la competitividad de las pymes de logística ligera en el Perú

El objetivo de la investigación fue diseñar e implementar una metodología basada en la transformación digital de forma ágil y en un corto periodo que permita a las pymes del sector de logística ligera del Perú incrementar su competitividad bajo un enfoque de investigación mixto con un diseño exploratorio secuencial (DEXPLOS), observacional y experimental. La población de estudio estuvo constituida por 750 pymes, la muestra estuvo conformada por 255 empresas y se realizó un muestreo probabilístico estratificado. Los criterios de inclusión fueron contar con estrategias competitivas definidas, un año de operación como mínimo y licencias de funcionamiento y código postal. El instrumento de investigación fue un cuestionario compuesto por 189 preguntas distribuidas en variables, tales como estrategia, rentabilidad, nivel técnico, productividad, calidad y trazabilidad. Se concluye que la implementación de la metodología propuesta permitió la transformación digital de las empresas objeto de estudio en un plazo de cuatro meses, por lo tanto, incrementaron su competitividad

Kinetics of occupancy of defect states in poly(3-hexylthiophene): fullerene solar cells

Energetics and kinetics of defects in the effective band gap of organic bulk heterojunctions are determined by means of capacitance methods. The technique consists of calculating the junction capacitance derivative with respect to the angular frequency of the small voltage perturbation applied to thin film poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester solar cells, varying the temperature. The analysis reveals the presence of defect bands (shallow acceptors) centered at E0 = 35 meV above the highest-occupied molecular orbital level of P3HT. The total density of defects results of order 1016 cm− 3. Characteristic frequency is obtained to be situated within the range of 1–10 Hz. Defect bands acting as negatively charged levels are responsible for the p-doping of the active layer and the band-bending near the cathode contact, as derived from Mott–Schottky capacitance–voltage analysis

Superkondentsadoreak: Energia Biltzeko Gailuak

Lan honetan superkondentsagailuen esparruan energia biltegiratzeko zenbait teknologiaren berri laburra emango dugu, beren funtzionamenduarekin batera. Hainbat superkondentsagailu motaren azterketa egin dugu, bai ikerketa, bai aplikazioen ikuspuntutik; gainera, aztergai hartuko ditugu konfigurazio bakoitzaren abantailak eta desabantailak eta propietateak, hala nola, gainazal azalera espezifikoa, kapazitantzia eta energia eta potentzia dentsitateak. Azkenik, CIC Energigunen superkondentsagailuen inguruan zenbait ikerketa lerrotan lortutako azken emaitzak aurkeztu ditugu.

Capacidades básicas : resolución de capacidades básicas deficitarias en ciclos formativos de Fabricación Mecánica

Convocatoria de Premios Nacionales de Investigación e Innovación Educativa 2006, modalidad innovación educativa, mención honoríficaProyecto elaborado por profesores del Instituto de Máquina Herramienta (Elgoibar, Guipúzcoa). El objetivo es desarrollar una serie de cuadernos digitales que permitan a los alumnos de Formación Profesional adquirir unas capacidades básicas que no tienen o tienen poco asentadas cuando se incorporan a los ciclos formativos que se imparten en el IMH. El proyecto surge como respuesta a la necesidad planteada por el profesorado del IMH, al identificar deficiencias en el alumnado ante ciertas capacidades básicas, relacionadas con materias como matemáticas, física, expresión escrita y oral o comportamiento. Se opta por explotar las posibilidades que ofrecen las nuevas tecnologías para el desarrollo de contenidos didácticos, elaborando los recursos en formato digital. La metodología seguida consta de las siguientes fases: 1. Identificación de capacidades básicas deficitarias. 2. Búsqueda de recursos. 3. Elaboración de casos aplicados a fabricación mecánica. 4. Elaboración de unidades didácticas. 5. Montaje del material en formato Web. 6. Experimentación en el aula, conclusiones y difusión. Del conjunto de capacidades básicas deficitarias identificadas, se priorizan y desarrollan en este proyecto las siguientes: Trigonometría, manejo de la calculadora científica, Matemáticas básicas y, por último, habilidades de comunicación. Las actividades diseñadas se basan en casos reales relacionados con la Fabricación Mecánica..País VascoBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 Planta; 28014 Madrid; Tel. +34917748000; Fax +34917748026; [email protected]

Carrier recombination losses in inverted polymer: Fullerene solar cells with ZnO hole-blocking layer from transient photovoltage and impedance spectroscopy techniques.

In this study, full coincidence between impedance spectroscopy and transient photovoltage techniques in measuring recombination kinetics of photogenerated charge carriers in inverted polymer:fullerene organic solar cells with ZnO hole-blocking layer is reported. Carrier lifetime exhibits values at illumination intensities near 1 sun within the microseconds time scale. Photogenerated charge carrier density attains values within 1015–1016 cm−3. Decay kinetics is analyzed by means of a bimolecular recombination law with a recombination coefficient slightly dependent on the charge density, which lies within the order of k ∼ 10−12 cm3 s−1. It is also demonstrated that inverted-processed cells exhibit capacitance, recombination resistance, and lifetime parameters comparable to those extracted from regular cells, despite the great differences between the contact structures of these kinds of devices