Room-temperature sodium-ion batteries have aroused interest for large-scale electrical energy storage in renewable energy and smart grid owing to the abundant sodium resources and low cost. Recently, many layered NaxMeO2 oxides have been proposed as cathode materials for sodium-ion batteries. Amongst them, in general, only layered oxides containing Ni or Co transition metal show promising Na storage performance. 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 batteries1. 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: Mg, Al, etc.) layered oxides2,3. The preliminary results are very promising and will be presented in this talk (Fig. 1). References 1. Xu, S.Y.; Wu, X.Y.; Li, Y.M.; Hu, Y. -S.; Chen, L.Q. Chin. Phys. B 2014, 23,118202. 2. Hu, Y. -S.; et al. Several Chinese patents have been filed. 3. Mu, L. Q.; Hu, Y. -S.; et al. 2014, To be submitted.

Novel copper-based layered oxide cathode for room-temperature sodium-ion batteries

249th National Meeting (2015)

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