The demand for inexpensive and effective energy storage technologies is rapidly increasing. The imminent exhaustion of fossil fuel resources and the environmental consequences related to their use, combined with the rapid expansion of renewable energy sources, promote the scientific community to develop advanced energy storage systems. Among the several technologies that are suitable for large-scale energy storage, Sodium-ion batteries (NIB) appear as one of the most appealing options. Sodium natural resources are unlimited everywhere, as sodium is the fourth most abundant element on earth. Additionally, sodium is the second-lightest and smallest alkali metal next to lithium. Indeed, research in this area, reflected in the number of publications, has dramatically increased since 2011.

We will describe a completed study on sodium-ion batteries. With the aim to offer a comprehensive view, we compared all the Na-ion systems studied herein to similar Li-ion systems. Na-ion and Li-ion full cells were investigated, using hard carbon as the anode material, NaNi_0.5Mn_0.5O₂ and LiNi_0.5Mn_0.5O₂ as the cathodes.

A comprehensive description and discussion of the possible use of hard carbons as anode is presented [1]. We explored storage mechanisms, cycling, stability, surface chemistry, and impedance behavior. We examined the choice of the binders, solvent and additives on the electrodes’ performance. The critical effect of the hard carbon anodes pretreatment on the total capacity and stability of full cells will be discussed.

We also offer a detailed description of the structure, phase transition, electrochemical behavior and kinetics of the NaNi_0.5Mn_0.5O₂ cathodes, including interesting comparison with their lithium analog [2]. Using impedance spectroscopy in three electrodes cells we show that the full cell impedance is dominated by the contribution of the cathode side. We discuss possible reasons for capacity fading of these systems, in connection to the cathode’s structure and relevant surface phenomena.

References

1. E. de la Llave, V. Borgel, E. Zinigrad, F. F. Chesneau, P. Hartmann, Y-K. Sun, D. Aurbach, Study of the Most Relevant Aspects related to Hard Carbons as Anode Materials for Na-ion Batteries, Compared to Li-ion Systems. Isr. J. Chem. (2015), 55, 1260-1274. 

2. E. de la Llave, V. Borgel, K.J. Park, J.Y. Hwang, Y.K. Sun, P. Hartmann, F. Chesneau and D. Aurbach, Comparison between Na-ion & Li-ion Cells: Understanding the Critical Roles of the Cathodes Stability and the Anodes Pretreatment on the Cells Behavior, ACS Applied Materials & Interfaces (2015), DOI: 10.1021/acsami.5b09835