Comprehensive Understanding of Steric-Hindrance Effect on the Trade-Off Between Zinc Ions Transfer and Reduction Kinetics to Enable Highly Reversible and Stable Zn Anodes

Abstract

The electrode interface concentration polarization attributed to the contradiction between sluggish mass transfer process and rapid electrochemical reduction kinetics significantly restricts the practical application of Zn anode. Creating a moderate Zn ions transfer and reduction chemistry is essential for durable zinc-ion batteries. In this work, this trade-off effect is realized by selecting large-size 4-Aminomethyl cyclohexanecarboxylic acid (AMCA) molecule as the electrolyte additive. Intriguingly, AMCA molecules reorganize the Zn²⁺ solvation structure via the robust coordination with Zn²⁺ and reconstruct H-bond networks, giving a pulled desolvation process. Meanwhile, AMCA enlarges the Zn²⁺ solvation size with a push force, confining the rapid electrochemical reduction kinetics. The balanced chemical environment is maintained via the moderate pull-push interplay. Besides, AMCA can anchor on zinc surface to create a water-poor microenvironment, fostering homogeneous Zn (002) deposition and effectively restricting water-induced side-reactions. Notably, the Zn||Zn symmetric cell with AMCA operates stably over 167 days at 20 mA cm⁻². Moreover, the Zn||VOX full cell employed AMCA ensures outstanding capacity retention of 99.15% after 590 cycles at 2 A g⁻¹, even with low N/P (4.3), lean electrolyte (50 µL mAh⁻¹) and ultrathin Zn foil of 10 µm. This work reveals unique insights into the balanced interfacial chemistry design toward high-performance zinc batteries.