Engineering multi-functionalized molecular skeleton layer for dendrite-free and durable zinc batteries

Abstract

Aqueous Zn batteries are subject to uncontrollable dendrite growth and water-induced parasitic side reactions, resulting in poor Zn2+ kinetics and limited lifespan. Herein, a self-consistent ultrathin multifunctional layer by integrating hydrophobic siloxane-based block and zincophilic diphosphate-building block into molecular skeletons on Zn foils (MTSi-Hedp-Zn) is proposed by a scalable and low-cost dip-coating technique. Experimental results combined with theoretical calculation (DFT) and COMSOL Simulations reveal that abundant O-Si-CH3 groups as hydrophobic block in the top of molecular skeletons is the contributing factor in precluding solvated H2O corrosion. Zincophilic PO bonds on organic phosphate block in the backbone work as attraction area for fast Zn2+ adsorption and transport kinetics. Simultaneously, such a combination enables surface-preferred (002) crystal planes on Zn metal, synergistically homogenizing the electric field at the interface and achieving preferentially flat growth without dendrites and side reactions. Accordingly, the MTSi-Hedp-Zn electrode exhibits an extended lifespan of over 2000 h and a much low voltage polarization of ~24.3 and 67.5 mV at 1 and 10 mA cm−2, respectively. Practical full cells coupled with commercial cathodes (CNT/MnO2 and V2O5) both perform much better capacity retention than the bare Zn case. The proposed hydrophobic-zincophilic interface by silane-organic phosphoric acid provides a significant construction tactic for designing dendrite-free and corrosion-free Zn electrodes and beyond.