Sodium (Na) shares similar chemical properties with lithium (Li) in many aspects, and Na has more positive potential, so it should be able to be used in the majority of the organic electrolytes which have been used in Li ion batteries. More importantly, Na is one of the most abundant elements in the Earth’s crust. Therefore rechargeable sodium batteries are the ideal alternative to LIBs ^[1-3] in many applications. Na-ion batteries (NIBs) consist of sodium intercalation materials for both positive and negative electrodes, which are electronically separated by electrolyte as a pure ionic conductor. Na ions are cycled back and forth from host electrodes, which is similar to LIBs. This design avoids the use of reactive metallic Na. So the research of NIBs is mainly focused on the development of the cathode materials, and the study of the metallic Na electrode has drawn few attentions in the past. As the Li⁺ deposition-stripping is crucial to LIBs, the nature of the metallic Na, especially electro-deposition-stripping characteristics, is also worthy of in-depth and systematic research.

In this work, the electrodeposition and stripping characteristics of metallic Na in the electrolyte of 1 mol L^-1 NaClO₄/EC+DMC (1:1 vol. %) were studied and the deposition-stripping behavior of Na⁺ on Cu and Sn substrates were compared. The deposition-stripping cycling performances of Na on the substrates were studied through galvanostatic charge-discharge method and cyclic voltammetry. The morphologies of the substrates before and after Na⁺ deposition were investigated through digital video microscopy. The kinetics of the Na⁺ electrodeposition on the different substrates was studied through galvanostatic pulse method. The solid electrolyte interface films of Na⁺ deposits on the substrates were characterized via electrochemical impedance spectroscopy. The results indicate that the nature of the substrate can significantly affect the electrodeposition characteristics of Na⁺. The high reactivity of metallic sodium with the organic electrolyte solvents and the dendrite formation during metallic Na deposition are even more problematic than metallic Li anodes. Sn is a more suitable substrate than Cu for Na⁺ electrodeposition due to the formation of Na—Sn alloy during the deposition of Na⁺.

References

[1] M. D. Slater, D. Kim, E. Lee, C. S. Johnson, Adv. Funct. Mater., 2013, 23, 947.

[2] S. Komaba, W. Murata, T. Ishikawa, N. Yabuuchi, T. Ozeki, T. Nakayama, A. Ogata, K. Gotoh, K. Fujiwara, Adv. Funct. Mater., 2011, 21, 3859.

[3] S. W. Kim, D. H. Seo, X. H. Ma, G. Ceder, K. Kang, Adv. Energy Mater., 2012, 2, 710.

Relating topic:

New Na based Electrodes