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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.

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(a) 1st discharge-charge curves at current density of 100 mA·g−1. (b) Discharge capacities as a function of applied current. (c) Cyclability measured using the limited capacity discharge mode for the Li-O2 cells containing oxygen electrodes composed of only KB, KB-MCO, and FSMCO, respectively. (d) Electrochemical impedance spectra for the three-electrode Li-O2 cells containing FSMCO oxygen electrodes as a working electrode, obtained after various discharge or charge stages; pristine, after partial discharge up to 1000 mAh g−1, after full discharge, and after full charge.
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f4: (a) 1st discharge-charge curves at current density of 100 mA·g−1. (b) Discharge capacities as a function of applied current. (c) Cyclability measured using the limited capacity discharge mode for the Li-O2 cells containing oxygen electrodes composed of only KB, KB-MCO, and FSMCO, respectively. (d) Electrochemical impedance spectra for the three-electrode Li-O2 cells containing FSMCO oxygen electrodes as a working electrode, obtained after various discharge or charge stages; pristine, after partial discharge up to 1000 mAh g−1, after full discharge, and after full charge.

Mentions: Further, the galvanostatic charge-discharge tests on the Li-O2 cell containing the oxygen electrodes composed of KB, KB-MCO, and FSMCO were carried out to evaluate the electrochemical performances of the cells in the potential ranging from 2.0 to 4.2 V. Figure 4a shows the first discharge-charge profiles for the Li-O2 cells tested using discharge-charge current density of 100 mA·g−1. For the Li-O2 cell containing the KB electrode, the first discharge capacity of 3830 mAh·g−1 was comparable to that obtained from similar carbon black electrodes in the TEGDME electrolyte2526. For the cell containing the KB-MCO electrode, the discharge capacity was improved to 8650 mAh·g−1. Furthermore, the discharge capacity of 10520 mAh·g−1 corresponding to the specific area capacity 6.8 mAh·cm−2 was the highest for the cell containing the FSMCO electrode. In addition, the ORR and OER polarizations in the Li-O2 cell were obviously reduced by introducing the MnCo2O4 (MCO) catalyst to the oxygen electrode, compared with the cell without MCO. The Li–O2 cell containing the FSMCO electrode exhibited a discharge potential plateau of 2.79 V, which is higher by 180 and 80 mV than that of the cells containing KB and KB-MCO, respectively. This result clearly indicates that FSMCO can effectively facilitate the ORR and that the catalyst with relatively higher content of MCO is more functional. In the subsequent charge process, the charge potential plateau of the cell with FSMCO was lower by 320 and 720 mV than that of the cells with KB-MCO and KB, respectively. The remarkably decreased overpotentials may be ascribed to the significantly enhanced OER activity on the carbon free FSMCO. In addition, highly porous FSMCO can supply more three-phase (oxygen/catalyst/electrolyte phases, i.e. gas/solid/liquid three-phase) reaction active sites to decompose Li2O2; especially the chestnut bur-like superstructures, can offer more active sites and enough transmission paths for O2 and Li+ ions. Although the explicit mechanism for the catalytic behavior has not yet been elucidated27, we ascertain that MCO can accelerate the kinetics of both the ORR and OER, which should be ascribed to this unique combination and hierarchical structure of MnCo2O4.


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)

(a) 1st discharge-charge curves at current density of 100 mA·g−1. (b) Discharge capacities as a function of applied current. (c) Cyclability measured using the limited capacity discharge mode for the Li-O2 cells containing oxygen electrodes composed of only KB, KB-MCO, and FSMCO, respectively. (d) Electrochemical impedance spectra for the three-electrode Li-O2 cells containing FSMCO oxygen electrodes as a working electrode, obtained after various discharge or charge stages; pristine, after partial discharge up to 1000 mAh g−1, after full discharge, and after full charge.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: (a) 1st discharge-charge curves at current density of 100 mA·g−1. (b) Discharge capacities as a function of applied current. (c) Cyclability measured using the limited capacity discharge mode for the Li-O2 cells containing oxygen electrodes composed of only KB, KB-MCO, and FSMCO, respectively. (d) Electrochemical impedance spectra for the three-electrode Li-O2 cells containing FSMCO oxygen electrodes as a working electrode, obtained after various discharge or charge stages; pristine, after partial discharge up to 1000 mAh g−1, after full discharge, and after full charge.
Mentions: Further, the galvanostatic charge-discharge tests on the Li-O2 cell containing the oxygen electrodes composed of KB, KB-MCO, and FSMCO were carried out to evaluate the electrochemical performances of the cells in the potential ranging from 2.0 to 4.2 V. Figure 4a shows the first discharge-charge profiles for the Li-O2 cells tested using discharge-charge current density of 100 mA·g−1. For the Li-O2 cell containing the KB electrode, the first discharge capacity of 3830 mAh·g−1 was comparable to that obtained from similar carbon black electrodes in the TEGDME electrolyte2526. For the cell containing the KB-MCO electrode, the discharge capacity was improved to 8650 mAh·g−1. Furthermore, the discharge capacity of 10520 mAh·g−1 corresponding to the specific area capacity 6.8 mAh·cm−2 was the highest for the cell containing the FSMCO electrode. In addition, the ORR and OER polarizations in the Li-O2 cell were obviously reduced by introducing the MnCo2O4 (MCO) catalyst to the oxygen electrode, compared with the cell without MCO. The Li–O2 cell containing the FSMCO electrode exhibited a discharge potential plateau of 2.79 V, which is higher by 180 and 80 mV than that of the cells containing KB and KB-MCO, respectively. This result clearly indicates that FSMCO can effectively facilitate the ORR and that the catalyst with relatively higher content of MCO is more functional. In the subsequent charge process, the charge potential plateau of the cell with FSMCO was lower by 320 and 720 mV than that of the cells with KB-MCO and KB, respectively. The remarkably decreased overpotentials may be ascribed to the significantly enhanced OER activity on the carbon free FSMCO. In addition, highly porous FSMCO can supply more three-phase (oxygen/catalyst/electrolyte phases, i.e. gas/solid/liquid three-phase) reaction active sites to decompose Li2O2; especially the chestnut bur-like superstructures, can offer more active sites and enough transmission paths for O2 and Li+ ions. Although the explicit mechanism for the catalytic behavior has not yet been elucidated27, we ascertain that MCO can accelerate the kinetics of both the ORR and OER, which should be ascribed to this unique combination and hierarchical structure of MnCo2O4.

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