Robust Zn anode enabled by a hydrophilic adhesive coating for long-life zinc-ion hybrid supercapacitors

Artificial polymer coating on Zn metal anode is an available strategy to address a series of notorious parasitic side reactions at Zn anode/aqueous electrolyte in aqueous Zn-based electrochemical devices. However, most hydrophilic polymer layers suffer from risks of being dissolved in aqueous electrolyte during long-term cycle process. The traditional coatings with strong adhesion to metal are often hydrophobic which intensely increase the interfacial resistance at Zn electrode/aqueous electrolyte and further restrain the interfacial ion transportation/migration. In this study, a hydrophilic adhesive coating (HAC) with proportionally distributed amides and acrylates is designed to circumvent this hydrophilicity/adhesion trade-off. The layer shows great ion-regulating capability in Zn2+ plating/stripping, thanks to the evenly distributed abundant carbonyl adsorption sites at the molecular level. Benefiting from the hydrophilic nature and long-lasting adhesion of the coating to the electrode, the HAC-modified Zn-Zn symmetric cell is able to deliver a long cycle life of 880 h at 5 mA cm−2/5 mAh cm−2, compared to 20 h for Bare Zn. The Zn-Ti asymmetric cell also exhibits excellent reversibility with an average coulombic efficiency of 97.6% after 200 cycles at 5 mA cm−2. The HAC-modified Zn-AC ion hybrid supercapacitor retains 100% of the initial capacity for a long life of 14,000 cycles. This hydrophilic functionalization of hydrophobic coating provides new design strategies and prospects for Zn anode artificial interface towards practically useful zinc-ion energy storage devices.