Tuning V Redox Couple By Metal-Ion Substitution in Na 3 V 2 (PO 4 ) 3 Cathode Material for High Energy Density Na-Ion Batteries
Recently, the demand for renewable energy has raised with the increase of environmental issues and exhaustion of crude oil. To acquire efficient utilization of the renewable energy, large-scale energy storage systems (ESSs) are necessary that balance the discrepancy between production of and the tim...
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| Published in | Meeting abstracts (Electrochemical Society) Vol. MA2016-02; no. 5; p. 651 |
|---|---|
| Main Authors | , , , , , |
| Format | Journal Article |
| Language | English |
| Published |
01.09.2016
|
| Online Access | Get full text |
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| Summary: | Recently, the demand for renewable energy has raised with the increase of environmental issues and exhaustion of crude oil. To acquire efficient utilization of the renewable energy, large-scale energy storage systems (ESSs) are necessary that balance the discrepancy between production of and the time required to consume renewable energy. Li-ion batteries have been considered as candidates for large-scale ESSs because they provide high energy density and a long cycle life. However, due to the lack of Li reserves in the Earth and the corresponding growing cost problems, Na-ion batteries have been received great attention as alternative candidates for Li-ion batteries. The Na-ion batteries can replace the Li-ion batteries in the aspects of abundant Na resources, low cost, and easily accessible reserves. Furthermore, the similarity of the electrochemical reaction mechanisms of Na-ion batteries to that of Li-ion batteries has accelerated the development of the Na-ion batteries; thus, various research studies have been conducted to find proper electrode materials for Na-ion batteries.
Among various cathode materials of sodium-ion batteries for large-scale applications, NASICON-Na
3
V
2
(PO
4
)
3
is an attractive candidate for the cathode material of Na-ion batteries due to its thermal and structural stabilities. Also, Na
3
V
2
(PO
4
)
3
shows 117.6 mAh·g
-1
theoretical capacity at 3.4 V vs. Na/Na
+
using the V
3+/4+
redox couple. However, the operating voltage of Na
3
V
2
(PO
4
)
3
should be improved to replace the conventional Li-ion battery cathode materials. If V
4+/5+
redox reaction, which utilizes higher operating voltage, can be employed in this material, higher operating voltage could be achieved. Herein, we suggest a simple method to enhance the operating voltage of Na
3
V
2
(PO
4
)
3
.
In this work, non-transition metal ions are substituted for V-ions in Na
3
V
2
(PO
4
)
3
to utilize V
4+/5+
redox reaction. During the (de)intercalation of Na-ions, the oxidation state of the non-transition metal ions is not changed. Hence, some V
3+
ions in Na
3
V
2
(PO
4
)
3
should be oxidized until V
5+
instead of non-transition metal ions while two Na-ions are extracted. Therefore, some part of capacity reacts at 3.4 V using V
3+/4+
redox couple and the other part reacts at voltage higher than 3.4 V using V
4+/5+
redox couple. Through the tuning of V redox couple, not only the enhancement of energy density of the cathode material but the cost reduction of expensive V source also is possible. The figure shows the initial charge profiles of Na
3
V
2
(PO
4
)
3
/C and metal-ion substituted Na
3
V
1.5
M
0.5
(PO
4
)
3
/C. In case of Na
3
V
1.5
M
0.5
(PO
4
)
3
/C, a high voltage V
4+/5+
redox reation was clearly observed as the cell was charged above 3.5 V vs. Na/Na
+
. In the presentation, the detailed structural analyses and electrochemical performance of the materials will be shown.
Figure 1 |
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| ISSN: | 2151-2043 2151-2035 |
| DOI: | 10.1149/MA2016-02/5/651 |