Novel Copper-Containing Layered Oxide Cathode for Room-Temperature Stationary Sodium-Ion Batteries
Searching for suitable electrode materials to satisfy the long-term stability requirement is an important step to realize the large-scale energy storage. Recently, many layered NaxMO2 (M: 3d transition metals) oxides have been proposed as positive electrode materials for sodium-ion batteries. Amongst them, in general, only layered oxides containing Ni or Co transition metal show promising Na storage performance in terms of high storage capacity, high rate capability and long cycling stability. However, Ni and Co are toxic and their oxides are relatively expensive, which would certainly increase the cost of the battery and is unfavorable for large-scale energy storage applications. Herein, we found that Cu2+/Cu3+ redox couple in such layered oxides is electrochemically active and highly reversible in sodium-ion batteries12. Take P2-Na0.68Cu0.34Mn0.66O2 as the first example, this material shows a reversible capacity of ca. 70 mAh/g with an average storage voltage of 3.8 V vs. Na+/Na. To the best of our knowledge, this is the first time to realize the reversible change of Cu2+/Cu3+ redox couple with high Na storage voltage and small polarization. Copper is harmless, and is already very common in our daily life. In addition, the cost of copper oxide is only half of that of nickel oxide. Based on this important finding, it is possible to use copper to design new layered oxides with similar Na storage performance as that of Ni or Co containing layered oxides. Therefore, we further optimize a series of air-stable NaaDxMnyFezCu1-x-y-zO2 (D(Dopant): Mg, Al, etc.) layered oxides13,14. The preliminary results are very promising and will be presented in this talk (Figure 1).
. Pan, H. L.; Hu, Y.-S.; Chen, L. Q. Energy Environ. Sci. 2013, 6, 2338-2360.
. Jian, Z. L.; Zhao, L.; Pan, H. L.; Hu, Y.-S.; et al. Electrochem. Commun. 2012, 14, 86-89.
. Jian, Z. L.; Han, W. Z.; Lu, X.; Yang, H. X.; Hu, Y.-S.; et al. Adv. Energy Mater. 2013, 3, 156-160.
. Jian, Z. L.; Yuan, C. C.; Han, W. Z.; Lu, X.; Gu, L.; Xi, X. K.; Hu, Y.-S.; et al. Adv. Funct. Mater. 2014, 24, 4265-4272.
. Zhao, L.; Pan, H. L.; Hu, Y.-S.; Li, H.; Chen, L. Q. Chin. Phys. B 2012, 21, 028201.
. Sun, Y.; Zhao, L.; Pan, H. L.; Lu, X.; Gu, L.; Hu, Y.-S.; et al. Nature Communications 2013, 4, 1870.
. Yu, X. Q.; Pan, H. L.; Wan, W.; Ma, C.; Bai, J. M.; Meng, Q. P.; Ehrlich, S. N.; Hu, Y.-S.; Yang, X. Q. Nano Lett. 2013, 13, 4721-4727.
. Zhao, L.; Zhao, J. M.; Hu, Y.-S.; et al. Adv. Energy Mater. 2012, 2, 962-965.
. Pan, H. L.; Lu, X.; Yu, X. Q.; Hu, Y.-S.; Li, H.; Yang, X. Q.; Chen, L. Q. Adv. Energy Mater. 2013, 3, 1186-1194.
. Wang, Y. S.; Yu, X. Q.; Xu, S. Y.; Bai, J. M.; Xiao, R. J.; Hu, Y.-S.; et al. Nature Communications 2013, 4, 2365.
. Li, Y. M.; Xu, S. Y.; Wu, X. Y.; Yu, J. Z.; Wang, Y. S.; Hu, Y.-S.; et al. J. Mater. Chem. A 2014, DOI: 10.1039/C4TA05451B.
. Xu, S.Y.; Wu, X.Y.; Li, Y.M.; Hu, Y.-S.; Chen, L.Q. Chin. Phys. B 2014, 23,118202.
. Hu, Y.-S.; et al. Several Chinese patents have been filed.
. Mu, L. Q.; Hu, Y.-S.; et al. 2014, To be submitted.
Figure 1. The typical charge/discharge curves of the air-stable NaaDxMnyFezCu1-x-y-zO2 (D: Mg, Al, etc.) positive electrodes (a) and full cell using hard carbon as the negative electrode (b).