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Unraveling the storage mechanism in organic carbonyl electrodes for sodium-ion batteries.

Wu X, Jin S, Zhang Z, Jiang L, Mu L, Hu YS, Li H, Chen X, Armand M, Chen L, Huang X - Sci Adv (2015)

Bottom Line: We take Na2C6H2O4 as an example to unravel the mechanism.It consists of alternating Na-O octahedral inorganic layer and π-stacked benzene organic layer in spatial separation, delivering a high reversible capacity and first coulombic efficiency.The experiment and calculation results reveal that the Na-O inorganic layer provides both Na(+) ion transport pathway and storage site, whereas the benzene organic layer provides electron transport pathway and redox center.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.

ABSTRACT
Organic carbonyl compounds represent a promising class of electrode materials for secondary batteries; however, the storage mechanism still remains unclear. We take Na2C6H2O4 as an example to unravel the mechanism. It consists of alternating Na-O octahedral inorganic layer and π-stacked benzene organic layer in spatial separation, delivering a high reversible capacity and first coulombic efficiency. The experiment and calculation results reveal that the Na-O inorganic layer provides both Na(+) ion transport pathway and storage site, whereas the benzene organic layer provides electron transport pathway and redox center. Our contribution provides a brand-new insight in understanding the storage mechanism in inorganic-organic layered host and opens up a new exciting direction for designing new materials for secondary batteries.

No MeSH data available.


Related in: MedlinePlus

Structure evolution during sodiation and desodiation.In situ XRD patterns collected during the first and second discharge/charge of the Na/Na2C6H2O4 cell under a current rate of C/20 at the voltage range between 1.0 and 2.0 V. (A and B) Structure evolution in the first cycle. (C and D) Structure evolution processes in the second cycle. a.u., arbitrary units.
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Figure 3: Structure evolution during sodiation and desodiation.In situ XRD patterns collected during the first and second discharge/charge of the Na/Na2C6H2O4 cell under a current rate of C/20 at the voltage range between 1.0 and 2.0 V. (A and B) Structure evolution in the first cycle. (C and D) Structure evolution processes in the second cycle. a.u., arbitrary units.

Mentions: To understand the structure evolution during sodium insertion and extraction, we performed the electrochemical in situ XRD experiment. Figure 3 (A and B) shows the structure evolution of the Na2C6H2O4 electrode in the first discharge and charge process. At the beginning of discharging, all peaks from the electrode are indexed to triclinic Na2C6H2O4 except for one peak at 18° from the polytetrafluoroethylene (PTFE) binder and a few peaks at 38.5°, 41.2°, and 44° from BeO on the Be window of in situ cell, respectively. The existence of two quinone groups allows for two sodium insertion and extraction. It can be observed that in the initial discharge, Na2C6H2O4 (Na2 phase) converts into Na4C6H2O4 (Na4 phase) through a two-phase reaction, evidenced by a set of Na4 phase peaks emerging at 14.6°, 24.9°, 31.8°, and 37.5° [which can be indexed to be (010), (101), (022), and (121) peaks in the later discussion] and a disappearing of Na2 phase (010), (011), (−111), and (121) peaks at 15.2°, 16.7°, 31°, and 40.6°. The first charge curve is divided into two equal plateaus at 1.3 and 1.6 V, indicating that the two inserted sodium atoms are separately extracted, implying an intermediate radical tri-anion. After charging to 1.4 V, Na4C6H2O4 (Na4 phase) first transforms into an intermediate-phase Na3C6H2O4 (Na3 phase), which is evidenced by the emergence of a new (100) peak at 25.8° and (101) peak at 27.3°. When both two sodium are extracted, the XRD pattern is converted back to the pristine Na2 phase. After the first cycle, the peak shift of Na2 phase is negligible, whereas the relative intensity of some peaks obviously changes, especially (1–11) peak at 2θ=31°. Compared with the XRD pattern of the powder sample, the relative intensity of (1–11) peak is higher in pristine electrode, suggesting that the preferred orientation occurs along the a axis in the composite electrode. After the first discharge and charge processes, the relative intensity is reduced, implying that the length of the a axis declines during the electrochemical reaction. These observations indicate that the first sodium insertion in this material involves a two-phase reaction, whereas the sodium extraction process includes two two-phase reactions. The phase evolution is also in good agreement with the shape of first discharge and charge curves, which consist of one discharge plateau and two charge plateaus, respectively.


Unraveling the storage mechanism in organic carbonyl electrodes for sodium-ion batteries.

Wu X, Jin S, Zhang Z, Jiang L, Mu L, Hu YS, Li H, Chen X, Armand M, Chen L, Huang X - Sci Adv (2015)

Structure evolution during sodiation and desodiation.In situ XRD patterns collected during the first and second discharge/charge of the Na/Na2C6H2O4 cell under a current rate of C/20 at the voltage range between 1.0 and 2.0 V. (A and B) Structure evolution in the first cycle. (C and D) Structure evolution processes in the second cycle. a.u., arbitrary units.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643786&req=5

Figure 3: Structure evolution during sodiation and desodiation.In situ XRD patterns collected during the first and second discharge/charge of the Na/Na2C6H2O4 cell under a current rate of C/20 at the voltage range between 1.0 and 2.0 V. (A and B) Structure evolution in the first cycle. (C and D) Structure evolution processes in the second cycle. a.u., arbitrary units.
Mentions: To understand the structure evolution during sodium insertion and extraction, we performed the electrochemical in situ XRD experiment. Figure 3 (A and B) shows the structure evolution of the Na2C6H2O4 electrode in the first discharge and charge process. At the beginning of discharging, all peaks from the electrode are indexed to triclinic Na2C6H2O4 except for one peak at 18° from the polytetrafluoroethylene (PTFE) binder and a few peaks at 38.5°, 41.2°, and 44° from BeO on the Be window of in situ cell, respectively. The existence of two quinone groups allows for two sodium insertion and extraction. It can be observed that in the initial discharge, Na2C6H2O4 (Na2 phase) converts into Na4C6H2O4 (Na4 phase) through a two-phase reaction, evidenced by a set of Na4 phase peaks emerging at 14.6°, 24.9°, 31.8°, and 37.5° [which can be indexed to be (010), (101), (022), and (121) peaks in the later discussion] and a disappearing of Na2 phase (010), (011), (−111), and (121) peaks at 15.2°, 16.7°, 31°, and 40.6°. The first charge curve is divided into two equal plateaus at 1.3 and 1.6 V, indicating that the two inserted sodium atoms are separately extracted, implying an intermediate radical tri-anion. After charging to 1.4 V, Na4C6H2O4 (Na4 phase) first transforms into an intermediate-phase Na3C6H2O4 (Na3 phase), which is evidenced by the emergence of a new (100) peak at 25.8° and (101) peak at 27.3°. When both two sodium are extracted, the XRD pattern is converted back to the pristine Na2 phase. After the first cycle, the peak shift of Na2 phase is negligible, whereas the relative intensity of some peaks obviously changes, especially (1–11) peak at 2θ=31°. Compared with the XRD pattern of the powder sample, the relative intensity of (1–11) peak is higher in pristine electrode, suggesting that the preferred orientation occurs along the a axis in the composite electrode. After the first discharge and charge processes, the relative intensity is reduced, implying that the length of the a axis declines during the electrochemical reaction. These observations indicate that the first sodium insertion in this material involves a two-phase reaction, whereas the sodium extraction process includes two two-phase reactions. The phase evolution is also in good agreement with the shape of first discharge and charge curves, which consist of one discharge plateau and two charge plateaus, respectively.

Bottom Line: We take Na2C6H2O4 as an example to unravel the mechanism.It consists of alternating Na-O octahedral inorganic layer and π-stacked benzene organic layer in spatial separation, delivering a high reversible capacity and first coulombic efficiency.The experiment and calculation results reveal that the Na-O inorganic layer provides both Na(+) ion transport pathway and storage site, whereas the benzene organic layer provides electron transport pathway and redox center.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.

ABSTRACT
Organic carbonyl compounds represent a promising class of electrode materials for secondary batteries; however, the storage mechanism still remains unclear. We take Na2C6H2O4 as an example to unravel the mechanism. It consists of alternating Na-O octahedral inorganic layer and π-stacked benzene organic layer in spatial separation, delivering a high reversible capacity and first coulombic efficiency. The experiment and calculation results reveal that the Na-O inorganic layer provides both Na(+) ion transport pathway and storage site, whereas the benzene organic layer provides electron transport pathway and redox center. Our contribution provides a brand-new insight in understanding the storage mechanism in inorganic-organic layered host and opens up a new exciting direction for designing new materials for secondary batteries.

No MeSH data available.


Related in: MedlinePlus