Nuevos materiales híbridos para electrodo negativo en baterías de ion litio basados en compuestos de estaño o titanio modificados con carbono o poliacrilonitrilo

Para la realización de esta Tesis Doctoral han sido sintetizados y caracterizados nuevos materiales híbridos basados en compuestos de estaño o de titanio modificados con carbono o con poliacrilonitrilo para su empleo como electrodo negativo en baterías de ion litio. Con el objeto de proceder a una exposición ordenada de los resultados obtenidos, este resumen ha sido dividido en tres bloques: 1- Materiales híbridos de cobalto-estaño y fase carbonosa. 2- Materiales híbridos de cobalto-estaño y poliacrilonitrilo. 3- Películas finas electrodepositadas. 1- Materiales híbridos de cobalto-estaño y fase carbonosa. Se han preparado diferentes compuestos de Co-Sn-carbono mediante reducción carbotermal de los óxidos metálicos en presencia de un precursor de carbono. Con este fin, se han empleado diferentes precursores de carbono, desde un gel orgánico resorcinol-formaldehido a diferentes residuos del petróleo proporcionados por Repsol, como son un coque verde de petróleo y un residuo de pirólisis de fuel oil. Los dos últimos ejemplos constituyen subproductos de bajo coste de la industria del petróleo a los que se pretende aportar un valor añadido mediante su aplicación en baterías de iónlitio. Con el objeto de conseguir una mezcla homogénea de los materiales, se han empleado procedimientos tales como la gelificación en reflujo, la molienda mecánica de precursores sólidos y la agitación de precursores fluidos. Para cada uno de estos materiales, se han empleado diferentes proporciones Sn/Co y metal/carbono con el fin de evaluar el papel, tanto de los elementos metálicos como de la fase carbonosa en el comportamiento electroquímico. Los diagramas de difracción de rayos X de las muestras carbonizadas han presentado un grupo de reflexiones estrechas que fueron atribuidas a la presencia de varias fases metálicas como Sn, CoSn2 y CoSn. También se ha observado, en menor medida para aquellas muestras con gran contenido en cobalto, un conjunto de reflexiones que fueron asignadas a Co3Sn2 e incluso a Co3SnC0.7. La evaluación de los...In this doctoral thesis new hybrid materials based on tin or titanium composite modified with carbon or polyacrylonitrile have been synthesized and characterized for using as negative electrode in lithium ion batteries. In order to clearly describe the results, the report is sectioned in three main chapters: 4- Hybrid materials of cobalt-tin and carbonaceous phase. 5- Hybrid materials of cobalt-tin and polyacrylonitrile. 6- Electrodeposited thin films. 1- Hybrid materials of cobalt-tin and carbonaceous phase. Various Sn-Co-C composites are prepared by carbothermal reduction of metal oxides in the presence of a carbon precursor. We chose different carbon precursors, including a resorcinol-formaldehyde organic gel and different petroleum residua, as a green coke petroleum and a Fuel Oil Pyrolysis, both provided by Repsol. The latter ones are low cost by-product from the petroleum industry. In order to achieve a homogeneous mixture of these materials, procedures such as gelification under reflux, mechanical milling of solid precursors or stirring of fluid precursors are employed. For each of these materials, different Sn/Co and metal/carbon ratios are proposed in order to evaluate the role of both of the metallic elements and the carbonaceous phase in the electrochemical behaviour. The X-ray diffraction patterns of the annealed samples show a set of narrow reflections that are ascribed to the presence of various intermetallic phases as Sn, CoSn2 y CoSn. Also, a set of reflections ascribable to Co3Sn2 and Co3SnC0.7 are observed to a lesser extent for those samples with high cobalt content. The evaluation of the patterns suggests an efficient carbothermal reduction during the carbonization at 800º C. The electron micrographs show that the presence of cobalt and carbonaceous phase favors the formation of nanosized metal particles highly dispersed in the carbon matrix. 119Sn Mössbauer spectroscopy evidenced to be a useful technique to reveal the presence of Co-Sn amorphous phases and therefore undetectable by X-ray diffraction. Thus, a high..

Compuestos intermetálicos nanodispersos: nuevos materiales de electrodo

II Encuentro sobre nanociencia y nanotecnología de investigadores y tecnólogos de la Universidad de Córdoba. NANOUC

Compuestos metal-carbono derivados del petróleo para electrododos de batería ión-litio

III Encuentro sobre Nanociencia y Nanotecnología de Investigadores y Tecnólogos Andaluce

On the Mechanism of Magnesium Storage in Microand Nano-Particulate Tin Battery Electrodes

This study reports on the electrochemical alloying-dealloying properties of Mg2Sn intermetallic compounds. 119Sn Mössbauer spectra of -Sn powder, thermally alloyed cubic-Mg2Sn, and an intermediate MgSn nominal composition are used as references. The discharge of a Mg/micro-Sn half-cell led to significant changes in the spectra line shape, which is explained by a multiphase mechanism involving the coexistence of c-Mg2Sn, distorted Mg2����� Sn, and Mg-doped -Sn. Capacities and capacity retention were improved by using nanoparticulate tin electrodes. This material reduces significantly the diffusion lengths for magnesium and contains surface SnO and SnO2, which are partially electroactive. The half-cell potentials were suitable to be combined versus the MgMn2O4 cathodes. Energy density and cycling properties of the resulting full Mg-ion cells are also scrutinize

NASICON-type Na3V2(PO4)3 as a new positive electrode material for rechargeable aluminium battery

Although rechargeable aluminium-ion batteries could be very promising, there are only a few materials described in the literature that can insert aluminium. NASICON-type Na3V2(PO4)3 (NVP) is here investigated as a new positive electrode, using aluminium chloride dissolved in O2-free water as electrolyte solution. The reversible capacity is around 60–100 mAh g−1, depending on the cycling conditions. The electrochemical, analytical, NMR, XPS and XRD results all together corroborate that sodium is deinserted during first charge and then aluminium is inserted during the discharge. Both bulk insertion and surface capacitance can contribute to the specific capacity. This is the first report about true insertion of a trivalent cation into a NASICON-type structure. In addition, this material is also electrochemically active vs. Al metal in non-aqueous cell, using ionic liquid as electrolyte solution, with a revesible capacity about 60–70 mAh g−1 at ca. 1.25 V vs. Al. However, in the case of using ionic liquid, sodium (and not aluminium) is reversibly (de)inserted [23]. The results demonstrate that NVP is promising as electrode for rechargeable aluminium batteries, and that the electrolyte solution strongly influence on the electrochemical reaction