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Definición de los centros redox en las reacciones de intercalación de litio en polimorfos

Haifeng Li¹, Srinivasan Ramakrishnan², John W Freeland³

¹Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, United States.

Journal of the American Chemical Society

|April 10, 2020

Resumen

Los óxidos en capas ricos en litio ofrecen una mayor capacidad de la batería de iones de litio al involucrar oxígeno redox. Li3RuO4 demuestra la intercalación y extracción reversibles de Li, destacando los desafíos en la estabilización de los estados de oxígeno para el diseño avanzado de la batería.

Área de la Ciencia:

Ciencias de los materiales
La electroquímica
Almacenamiento de energía

Sus antecedentes:

Los cátodos LiMO2 en capas limitan la densidad de energía de las baterías de iones de litio para vehículos eléctricos.
La estoiquiometría de litio puede aumentar la capacidad más allá de la redox tradicional del metal de transición.
El papel de los ligandos de óxido en esta capacidad adicional no se entiende bien.

Objetivo del estudio:

Investigar la actividad redox del rutenio (Ru) y el oxígeno (O) en Li3RuO4 como sistema modelo.
Evaluar el efecto de la ordenación Li/Ru en las propiedades electroquímicas.
Comprender los mecanismos detrás de la capacidad adicional en materiales ricos en litio.

Principales métodos:

Análisis electroquímico completo de Li3RuO4 bajo diversas condiciones.
Evaluación de los efectos del orden Li/Ru.
Estudio de la actividad redox que involucra tanto metales de transición como ligandos de óxido.

Principales resultados:

El Li3RuO4 exhibe una intercalación reversible de Li a Li4RuO4 por debajo de 2,5 V a través de la redox Ru5+/Ru4+.
La extracción de Li anódico ocurre a 3,9 V, involucrando significativamente estados O y compitiendo con reacciones secundarias.
La reintercalación después de la extracción de alta tensión sigue una vía diferente de Ru5+/Ru4+ por encima de 2,5 V, mostrando histeresis química pero reversibilidad en ciclos posteriores.

Conclusiones:

La estabilización de estados de O altamente agotados, incluso con metales 4d como Ru, presenta un desafío.
Los materiales pueden acceder a la misma pareja redox en diferentes potenciales basados en cambios estructurales.
La comprensión de la covalencia de óxido es crucial para el diseño de materiales de almacenamiento de litio de alta capacidad.

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