Rationally designed multifunctional hyperbranched polymer as a trace additive for stable zinc anodes

Abstract

Aqueous zinc-ion batteries attract increasing attention due to their promising electrochemical performance and intrinsic safety. However, the parasitic corrosion reactions and uncontrolled Zn dendrite growth impede their practical application. Herein, a hyperbranched polymer, named N-HPG, with repeating hydroxyl groups, ether bonds, and positively charged quaternary ammonium groups, is designed and introduced to regulate the zinc deposition. Taking advantage of the multifunctional groups, a trace amount of the additive (100 mg L⁻¹) is found to be able to simultaneously form a protective layer on the Zn anode, participate in the solvation structure of Zn²⁺, and competitively interact with Zn²⁺ at the protrusions to inhibit the dendrite growth. Based on its exceptional electrochemical properties, the Zn//Zn symmetric cells with N-HPG as the additive achieve lifespans of over 3200 hours at 0.5 mA cm⁻² and 600 hours at 10 mA cm⁻², respectively. Furthermore, the Zn//Cu cells with N-HPG containing electrolyte show a markedly improved coulombic efficiency of 99.8% over 800 cycles. This work demonstrates that employing molecular design to rationally construct novel and highly efficient additives is a promising strategy to improve the stability of Zn anodes in aqueous zinc-ion batteries.