(Digital Presentation) A 2.8V Reversible Sn-Li Battery

Abstract

Tin (Sn) is a metal that is commonly used in our daily life. With the rapid development of lithium-ion battery in the past decades, Sn and its alloy, such as Sn-Cu[1], and Sn-Ni[2], Sn-Co[3] and Sn-Fe[4] have been used as anode for lithium-ion battery because they can undergo alloying/dealloying process with lithium ions and exhibit high capacity and suitable working voltage of about 0.4 V vs. Li/Li+. Sn can also undergo an oxidation reaction to Sn2+, with an electrode potential of about -0.14 V vs. SHE. It is therefore possible to also use Sn as a cathode material.Herein, we are first to demonstrate a metal-metal battery made up of Sn metal as the cathode and Li metal as the anode in organic electrolyte (see Fig. a). Sn foil and Li foil are simply assembled with 3M LiTFSI in dimethoxyethane/propylene carbonate (DME/PC) electrolyte in an Ar-filled glove box to form a pouch cell. During charging, Sn will give out two electrons and dissolves into the electrolyte as Sn2+, while during discharging, the metal ions will be re-deposited onto the cathode. Thus, the energy is stored in the form of Sn2+ in the electrolyte. The charge-discharge curves in Fig. b show that the operating voltage of the battery is about 2.8 V.Since Sn2+ that is dissolved into the electrolyte from the cathode has higher potential than the Li metal anode, any Sn2+ ions cross-over to the anode will be spontaneously reduced, decreasing the efficiency of the battery. To suppress such self-discharge process, an anion exchange membrane based on poly(ionic liquid) polymer coated on common polypropylene separator is adopted. The Sn-Li battery with the modified separator tested in a current rate of 0.2 mA cm-2 with a capacity limitation of 0.1 mAh cm-2 gives an average Coulombic efficiency about 99.5% and can be cycled for more than 1500 cycles(See Fig. c).We found that the stripping/deposition of Sn on the cathode, and its polarization depend strongly on the type of electrolyte used. With 3M LiTFSI in DME/PC electrolyte, the discharge voltage is lowered by about 0.05 V when the current density is increased from 0.2 mA cm-2 to 1 mA cm-2. More results on the factors affecting the charge-discharge performance of Sn-Li batteries will be discussed at the meeting.[1]X. F. Tan, S. D. McDonald, Q. Gu, Y. Hu, L. Wang, S. Matsumura, T. Nishimura, K. Nogita, Journal of Power Sources 2019, 415, 50.[2]H. Zhang, T. Shi, D. J. Wetzel, R. G. Nuzzo, P. V. Braun, Advanced Materials 2016, 28, 742.[3]J. Yang, J. Zhang, X. Zhou, Y. Ren, M. Jiang, J. Tang, ACS Applied Materials & Interfaces 2018, 10, 35216.[4]Z. Lin, X. Lan, X. Xiong, R. Hu, Materials Chemistry Frontiers 2021, 5, 1185. Figure 1