Hydrophilicity and Zincophilicity Coincorporated Zwitterionic Additives for High-Performance Zinc Metal Batteries
Shiyu Xu, Xinxin Yang, Peng Zhang, Shengyang Huang, Yuanyuan Sun, Lirui Mao, Ho Seok Park, Pil J. Yoo
Abstract
Despite the potential of Zn metal batteries (ZMBs) due to their low cost, environmental benefits, and favorable Zn 2+ /Zn redox potential, challenges such as low Zn utilization and parasitic reactions hinder their performance. These issues arise from the thermodynamic instability of the Zn anode and high-desolvation energy barriers. To overcome these challenges, this study investigates two zwitterionic compounds with hydrophilic and zincophilic functional groups, BES (N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid) and MES (2-(N-morpholino)ethanesulfonic acid), selecting BES as the optimal electrolyte additive. The zwitterionic effect of BES promotes Zn 2+ dissociation, reduces concentration polarization, and enhances Zn 2+ kinetics, forming a dynamic electric double layer (EDL) that guides uniform Zn deposition. As a result, Zn||Zn symmetric cells with BES demonstrate dendrite-free plating/stripping for over 3300 h at 1 mA cm –2 and 2 mAh cm –2 . At a high current density (5 mA cm –2 ) and a high areal capacity (10 mAh cm –2 ), stable operation is achieved for over 450 h. Zn||ZnVO full cells show over 2700 cycles at 2 A g –1 with 88% capacity retention. Zn||I 2 full cells cycle stably for over 30,000 cycles at 10 A g –1 with negligible capacity decay, highlighting significant performance improvement of BES.