Interface behavior in negative current collectors for sodium‖zinc liquid metal batteries: Implications for enhanced energy storage performance

Abstract

All-liquid structure and elevated operational temperatures of liquid metal batteries (LMBs) cause severe corrosion of the current collector, impacting cycling performance. This investigation explores the interaction behaviors between negative current collectors (Mo, W, Fe) and the negative active material (Na) within Na|NaCl-CaCl2|Zn LMB. Experiment results indicate that the Na|NaCl-CaCl2|Zn LMB with Fe current collector displays higher cycle stability and smaller polarization than that using Mo or W current collector. The capacity fading rates of 1.23 %, 1.03 %, and 0.23 % in 40 cycles for Mo, W, and Fe current collectors, respectively. Characterizations of materials indicate that Fe4Zn9, W-Zn solid solution and MoZn7 are formed on the Fe, W, and Mo interfaces. Theoretical calculations reveal that the adsorption energy of Na atom on Fe/Fe4Zn9 surpassed that on other current collectors, which indicates the superior charge-transfer kinetics of Na+ on the Fe electrode. The high performance of Fe current collector is attributed to the formation of a dense structure of Fe-Zn alloy and fast charge-transfer ability. Our study contributes to a deeper understanding of the intricate electrochemical processes at the negative electrode interface and provides a practical framework for optimizing the performance of Na‖Zn LMBs.