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Control de la superestructura de la histeresis de tensión del primer ciclo en cátodos de oxígeno-redox
Robert A House1, Urmimala Maitra1, Miguel A Pérez-Osorio1
1Department of Materials, University of Oxford, Oxford, UK.
Nature
|December 10, 2019
Resumen
La histeresis de voltaje en los cátodos ricos en álcali está vinculada a su superestructura. Una superestructura de cinta suprime la migración de iones y la liberación de oxígeno, lo que permite un rendimiento estable de la batería y evita la pérdida de energía durante el ciclo.
Área de la Ciencia:
- Ciencias de los materiales
- La electroquímica
- Química del estado sólido
Sus antecedentes:
- Los cátodos de intercalación ricos en álcali ofrecen una mayor densidad de energía en las baterías al utilizar óxido y iones de metal de transición redox.
- La histeresis de voltaje del primer ciclo, una pérdida de energía durante la carga y descarga iniciales de la batería, es un desafío significativo.
- Esta histeresis a menudo se atribuye al desplazamiento de iones de metal de transición y a los procesos redox de oxígeno.
Objetivo del estudio:
- Investigar el papel de la superestructura del cátodo en la determinación de la histeresis de voltaje del primer ciclo.
- Para comparar dos cátodos de intercalación relacionados con diferentes superestructuras: Na0.75[Li0.25Mn0.75]O2 y Na0.6[Li0.2Mn0.8]O2.
- Identificar estrategias para mitigar la histeresis de voltaje en los cátodos de oxígeno-reducción.
Principales métodos:
- Análisis comparativo de dos materiales de cátodo de intercalación con distintas superestructuras.
- Ciclo electroquímico y caracterización.
- Espectroscopia de absorción de rayos X para sondear los cambios en la estructura electrónica.
Principales resultados:
- La superestructura de panal en Na0.75[Li0.25Mn0.75]O2 se pierde al cargar, lo que lleva a la formación de oxígeno molecular y la migración de iones de manganeso.
- Este cambio estructural causa una pérdida de voltaje irreversible (histeresis) durante la descarga.
- La superestructura de cinta en Na0.6[Li0.2Mn0.8]O2 suprime el trastorno del manganeso y la formación de oxígeno, reduciendo significativamente la histeresis.
Conclusiones:
- La histeresis de voltaje del primer ciclo en los cátodos de oxígeno-redox depende críticamente de la superestructura del cátodo.
- Una superestructura de cinta suprime efectivamente la migración del metal de transición y la liberación de oxígeno, minimizando así la histeresis.
- El diseño de cátodos con superestructuras específicas, como el tipo de cinta, es clave para lograr un rendimiento estable y eficiente de la batería.
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