Electronic Structure of Sodium Superoxide Bulk, (100) Surface, and Clusters using Hybrid Density Functional: Relevance for Na-O2 Batteries.
Clarifying the electronic structure of sodium superoxide (NaO2) is a key step in understanding the electrochemical behavior of Na-O2 batteries. Here we report a density functional theory study to explore the effect of atomic structure and morphology on the electronic properties of different model systems: NaO2 bulk, (100) surface, and small (NaO2)n clusters (n = 3-8). We found that a correct description of the open-shell 2p electrons of O2(-) requires the use of a hybrid functional, which reveals a clear insulating nature of all of the investigated systems. This sheds light onto the capacity limitations of pure NaO2 as a discharge product and highlights the need for developing new strategies to enhance its electron transport in the optimization of Na-O2 cells.
†CIC Energigune, Albert Einstein 48, 01510 Miñano, Álava, Spain.
Oier
O
Arcelus
†CIC Energigune, Albert Einstein 48, 01510 Miñano, Álava, Spain.
Chunmei
C
Li
†CIC Energigune, Albert Einstein 48, 01510 Miñano, Álava, Spain.|‡Departamento de Química Inorgánica, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, 48080 Bilbao, Spain.
Teófilo
T
Rojo
†CIC Energigune, Albert Einstein 48, 01510 Miñano, Álava, Spain.
Javier
J
Carrasco
Na-air battery; NaO2; density functional theory; electronic properties of NaO2; energy storage