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Las superficies de peróxido de litio son metálicas, mientras que las superficies de óxido de litio no lo son
Maxwell D Radin1, Jill F Rodriguez, Feng Tian
1Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-2125, USA.
Journal of the American Chemical Society
|December 14, 2011
Resumen
Los cálculos de los primeros principios revelan que las superficies estables de peróxido de litio son semimetálicas y ferromagnéticas, a diferencia del aislante óxido de litio. Estas distintas propiedades electrónicas explican las diferencias de reversibilidad electroquímica en las baterías de litio-oxígeno.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- La electroquímica es electroquímica.
- Química computacional es la química computacional.
Sus antecedentes:
- El peróxido de litio (Li(2) O(2) y el óxido de litio (Li(2) O) son productos clave de descarga en las baterías de litio-oxígeno.
- Comprender sus propiedades superficiales es crucial para optimizar el rendimiento de la batería y la vida útil del ciclo.
Objetivo del estudio:
- Caracterizar la estabilidad termodinámica y la estructura electrónica de las superficies Li(2) O(2) y Li(2) O.
- Para identificar facetas superficiales estables utilizando cálculos de primeros principios y la construcción de Wulff.
- Para correlacionar las propiedades superficiales con el comportamiento electroquímico observado en las baterías de litio-oxígeno.
Principales métodos:
- Se emplearon cálculos de la Teoría Funcional de Densidad (DFT) para investigar 40 superficies.
- Se evaluó la estabilidad termodinámica, teniendo en cuenta el error de sobreunión de oxígeno.
- Se analizaron las estructuras electrónicas superficiales, incluidas las propiedades magnéticas.
Principales resultados:
- Se identificaron varias nuevas superficies estables ricas en oxígeno Li(2) O(2) ({0001}, {1 ̅100}).
- Las superficies estables de Li(2) O(2) exhiben un comportamiento semimetálico y ferromagnetismo debido a los oxígenos superficiales.
- Las superficies estables de Li(2) O son aislantes y no magnéticas, y se prefieren las superficies estequiométricas.
Conclusiones:
- La naturaleza semimetálica y ferromagnética única de las superficies de Li(2) O(2), en contraste con el Li(2) O aislante, explica las diferencias en la reversibilidad electroquímica de la batería.
- Las vías superficiales conductivas en Li(2) O(2) pueden mitigar las limitaciones del transporte de electrones a granel, lo que potencialmente mejora la capacidad de la batería.
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