Facultad de Ciencias

MgH2-TiH2 nanocomposites. from hydrogen stores to novel anodes of Li-ion batteries

Fecha

27-04-2017

Hora

15:30 h

Lugar

Aula 312 del módulo 0 del Edificio de Ciencias

Descripción

Lithium-ion batteries are today largely used as energy storage systems for mobile electronics and electrical vehicles. However, insertion compounds that currently operate in this technology reach intrinsic limitations. Improved battery performances are expected from novel reaction schemes or technologies, such as conversion reactions or metal-air batteries. In this context, Metal Hydrides (MH_x) have been proposed as potential candidates for negative electrode in Li-ion batteries .

Metal hydrides (MH_x) operate through the conversion reaction: MH_x + xe^- + xLi⁺ ⇌ M +xLiH. They offer high capacity, suitable potential and low polarization. However, reaction kinetics and cycle-life need to be improved for practical applications. During the conversion reaction, the metal hydride disproportionates into metallic species and LiH which should be reformed during electrochemical cycling. Therefore, fast enough mass-transport of solid species has to be attained at room temperature which is only possible while using finely dispersed nanostructured hydrides.

We have demonstrated that nanostructured hydrides can be efficiently produced by mechanical milling of metal powders under hydrogen atmosphere . In particular, MgH₂-TiH₂ nanocomposites with nanosized crystallites ranging from 4 to 12 nm have been synthetized at ICMPE. They are shown to be excellent hydrogen stores at moderate temperatures (300 °C) with outstanding kinetic properties and cycling stability. Based on these results, we have recently studied their properties as negative electrodes of Li-ion batteries using either conventional liquid organic electrolytes or LiBH₄ as solid electrolyte [6]. As a major outcome, a complete all-solid-state novel cell has been successfully built comprising MgH₂-TiH₂ nanocomposite as anode, lithiated sulfur as cathode and LiBH₄ as electrolyte.

 

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