Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Non-Aqueous Electrolytes

Rechargeable Mg batteries have been identified as a candidate storage system for the next-generation high energy density rechargeable batteries because of the possibility of pairing a non-dendrite forming Mg metal anode (~2.37 V vs. SHE) with high theoretical specific capacity (2205 A h kg -1 ) [1] with a Mg intercalation-based cathode. However, several daunting problems still prevent the realization of Mg-battery: (i) the limited selectivity of electrolyte systems that display reversible Mg deposition, (ii) the narrow electrochemical window of the electrolyte, (iii) lack of high-voltage cathode materials, (iv) irremediable interruption of the battery functions by passivation of the anode material. While it is well established that Mg can be deposited reversibly from complex ethereal solutions of Mg-Chloro complex reagents, the stripping/deposition mechanism at the anode is still debated [2,3]. In this talk we present a detailed atomistic DFT study of the interaction of solvent molecules i.e. THF, and the salts (Mg-Chloro complex) when in contact with Mg-anode surfaces, focusing on the competitive absorption of these chemical species at the interface [4]. Ab initio molecular dynamics results will complement adsorption calculations providing a better understanding of the morphology of the electrolyte/anode interface. These models are essential to clarify the challenging electron-transfer mechanism occurring at the electrode/solvent interface [4]. References: [1] D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, and E. Levi, Nature 407 , 724–727 (2002). [2] N. Pour, Y. Gofer, D. T Major, and D. Aurbach, J. Am. Chem. Soc. 133 , 6270–6278 (2011). [3] R. E. Doe, R. Han, J. Hwang, A. J. Gmitter, I. Shterenberg, H. D. Yoo, N. Pour, and D. Aurbach, Chem. Commun. 50 , 243–245 (2014). [4] P. Canepa, G. S. Gautam, R. Malik, S. Jayraman, Z. Rong, K. R. Zavadil, K. Persson, G. Ceder, Chem. Mater. 10.1021/acs.chemmater.5b00389