Investigation of Calcium Alloying with Sb, Sn and Bi As Negative Electrode Materials for Rechargeable Calcium Battery in Non-Aqueous Electrolytes

Abstract

Alloys were suggested as alternative anode materials for Ca metal anode because they have a high specific capacity and low overpotential. [1] A DFT study of CaxM has suggested a variety of alloy-type anode materials and considered the alloying voltage, volume expansion, and specific capacity. The metals such as Si, Sb, Bi, Al, Pt, Pb, and so on were predicted to be promising inexpensive anode candidates. [1] An Sn Nano-particular with a thickness of 25 μm was investigated for both the anode and current collector using 0.8 M Ca(PF6)2 in EC:PC:DMC:EMC (2:2:3:3) electrolytes. [2] It’s showed a high and wide voltage window (up to 4.8 V) and the cell could be cycled more than 300 cycles. The alloying compounds were found to be different phases with finally Ca7Sn6.In this work, we study the fundamentals of the alloying process alloying of Ca thin film of bulk Sb, Sn, and Bi on polycrystalline Au using non-aqueous electrolyte (1.5 M Ca(BH4)2 in THF) at room temperature. Calcium stripping and plating using a Ca(BH4)2 in THF electrolyte shows high Coulombic efficiency (95 %) at room temperature on an Au substrate. [3] The cycling reversibility of alloying/de-alloying with Sb, Sn, and Bi have been demonstrated. The cyclic voltammogram for Ca insertion/de-insertion into Sb, Sn, and Bi-modified electrode shows a positive shift of the onset potential of Ca deposition compared to that at bare Au electrode. The ratio of moles of Ca to Sb, Sn, and Bi agrees with the stoichiometry of CaSb2, CaSn2, and CaBi3 alloy. Potential step were used to study the kinetics of insertion. The diffusion coefficient of Ca into the Sb, Sn, and Bi layers is calculated to be 10−14 \U0001d461\U0001d45c 10−15 cm2s-1. Acknowledgments: The authors acknowledge funding by the Federal Ministry of Education and Research of Germany (BMBF, FKZ; 03EK3027A).[1] Z. Yao, V. I. Hegde, A. Aspuru-Guzik, and C. Wolverton, Advanced Energy Materials 9:1802994 (2019).[2] N. Z. Wu, W. J. Yao, X. H. Song, G. Zhang, B. J. Chen, J. H. Yang, and Y. B. Tang, Advanced Energy Materials 9:7 (2019).[3] D. Wang, X. Gao, Y. Chen, L. Jin, C. Kuss, and P. G. Bruce, Nature Materials 17:16 (2017).