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Simple synthesis of highly catalytic carbon-free MnCo2O4@Ni as an oxygen electrode for rechargeable Li-O2 batteries with long-term stability.

Kalubarme RS, Jadhav HS, Ngo DT, Park GE, Fisher JG, Choi YI, Ryu WH, Park CJ - Sci Rep (2015)

Bottom Line: The highly porous structure of the electrode allows the electrolyte and oxygen to diffuse effectively into the catalytically active sites and hence improve the cell performance.The Li-O2 cell has demonstrated a cyclability of 119 cycles while maintaining a moderate specific capacity of 1000 mAh g(-1).Furthermore, the synergistic effect of the fast kinetics of electron transport provided by the free-standing structure and the high electro-catalytic activity of the spinel oxide enables excellent performance of the oxygen electrode for Li-O2 cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Material Science and Engineering, Chonnam National University, 77, Yongbongro, Bukgu, Gwangju 500-757, South Korea.

ABSTRACT
An effective integrated design with a free standing and carbon-free architecture of spinel MnCo2O4 oxide prepared using facile and cost effective hydrothermal method as the oxygen electrode for the Li-O2 battery, is introduced to avoid the parasitic reactions of carbon and binder with discharge products and reaction intermediates, respectively. The highly porous structure of the electrode allows the electrolyte and oxygen to diffuse effectively into the catalytically active sites and hence improve the cell performance. The amorphous Li2O2 will then precipitate and decompose on the surface of free-standing catalyst nanorods. Electrochemical examination demonstrates that the free-standing electrode without carbon support gives the highest specific capacity and the minimum capacity fading among the rechargeable Li-O2 batteries tested. The Li-O2 cell has demonstrated a cyclability of 119 cycles while maintaining a moderate specific capacity of 1000 mAh g(-1). Furthermore, the synergistic effect of the fast kinetics of electron transport provided by the free-standing structure and the high electro-catalytic activity of the spinel oxide enables excellent performance of the oxygen electrode for Li-O2 cells.

No MeSH data available.


Related in: MedlinePlus

Schematic illustration of the nucleation and growth of Li2O2 on the MnCo2O4 nanorod array.
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f6: Schematic illustration of the nucleation and growth of Li2O2 on the MnCo2O4 nanorod array.

Mentions: Interestingly, the morphological evolution of the discharge product on the FSMCO electrode was highly reversible during the discharge–charge processes. The morphological evolution and the possible growth mechanism of Li2O2 on the MnCo2O4 nanorods can be explained as shown in the schematic illustration of Fig. 6. The growth process of Li2O2 can be simply divided into two steps. In an initial step, the nucleation sites are formed on the surface of MnCo2O4 nanorods and in the subsequent step, Li2O2 grows laterally to completely cover the nanorods. As suggested previously, oxygen diffuses through the oxygen electrodes is bound to the surface of the nanorods via absorption at oxygen vacancies formed due to solid-state redox couples of Mn2+/Mn3+and Co3+/Co2+, and then reduced to form meta-stable O2− in the discharge process3536. Finally, Li2O2 is generated by the subsequent dismutase reaction of superoxide ions with solvated lithium ions in the liquid electrolyte. The extended growth of the formed nucleation site in the preceding step results in the complete coverage of nanorods with the discharge product, as shown in Fig. 5c. Moreover, it can be seen that the discharge products formed on the top of the nanorods are larger than those formed at any other place. This indicates that the open ends of the nanorods are the most active sites due to a higher surface-charge density. Similarly, the most electrochemically active sites at the tips have been reported for NiCo2O4, resulting in the formation of Li2O2 microspheres with nanoflake-like morphology21.


Simple synthesis of highly catalytic carbon-free MnCo2O4@Ni as an oxygen electrode for rechargeable Li-O2 batteries with long-term stability.

Kalubarme RS, Jadhav HS, Ngo DT, Park GE, Fisher JG, Choi YI, Ryu WH, Park CJ - Sci Rep (2015)

Schematic illustration of the nucleation and growth of Li2O2 on the MnCo2O4 nanorod array.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4543937&req=5

f6: Schematic illustration of the nucleation and growth of Li2O2 on the MnCo2O4 nanorod array.
Mentions: Interestingly, the morphological evolution of the discharge product on the FSMCO electrode was highly reversible during the discharge–charge processes. The morphological evolution and the possible growth mechanism of Li2O2 on the MnCo2O4 nanorods can be explained as shown in the schematic illustration of Fig. 6. The growth process of Li2O2 can be simply divided into two steps. In an initial step, the nucleation sites are formed on the surface of MnCo2O4 nanorods and in the subsequent step, Li2O2 grows laterally to completely cover the nanorods. As suggested previously, oxygen diffuses through the oxygen electrodes is bound to the surface of the nanorods via absorption at oxygen vacancies formed due to solid-state redox couples of Mn2+/Mn3+and Co3+/Co2+, and then reduced to form meta-stable O2− in the discharge process3536. Finally, Li2O2 is generated by the subsequent dismutase reaction of superoxide ions with solvated lithium ions in the liquid electrolyte. The extended growth of the formed nucleation site in the preceding step results in the complete coverage of nanorods with the discharge product, as shown in Fig. 5c. Moreover, it can be seen that the discharge products formed on the top of the nanorods are larger than those formed at any other place. This indicates that the open ends of the nanorods are the most active sites due to a higher surface-charge density. Similarly, the most electrochemically active sites at the tips have been reported for NiCo2O4, resulting in the formation of Li2O2 microspheres with nanoflake-like morphology21.

Bottom Line: The highly porous structure of the electrode allows the electrolyte and oxygen to diffuse effectively into the catalytically active sites and hence improve the cell performance.The Li-O2 cell has demonstrated a cyclability of 119 cycles while maintaining a moderate specific capacity of 1000 mAh g(-1).Furthermore, the synergistic effect of the fast kinetics of electron transport provided by the free-standing structure and the high electro-catalytic activity of the spinel oxide enables excellent performance of the oxygen electrode for Li-O2 cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Material Science and Engineering, Chonnam National University, 77, Yongbongro, Bukgu, Gwangju 500-757, South Korea.

ABSTRACT
An effective integrated design with a free standing and carbon-free architecture of spinel MnCo2O4 oxide prepared using facile and cost effective hydrothermal method as the oxygen electrode for the Li-O2 battery, is introduced to avoid the parasitic reactions of carbon and binder with discharge products and reaction intermediates, respectively. The highly porous structure of the electrode allows the electrolyte and oxygen to diffuse effectively into the catalytically active sites and hence improve the cell performance. The amorphous Li2O2 will then precipitate and decompose on the surface of free-standing catalyst nanorods. Electrochemical examination demonstrates that the free-standing electrode without carbon support gives the highest specific capacity and the minimum capacity fading among the rechargeable Li-O2 batteries tested. The Li-O2 cell has demonstrated a cyclability of 119 cycles while maintaining a moderate specific capacity of 1000 mAh g(-1). Furthermore, the synergistic effect of the fast kinetics of electron transport provided by the free-standing structure and the high electro-catalytic activity of the spinel oxide enables excellent performance of the oxygen electrode for Li-O2 cells.

No MeSH data available.


Related in: MedlinePlus