Anion-functionalized interfacial layer for stable Zn metal anodes

Zinc metal anodes suffer from severe dendrite growth and parasitic hydrogen evolution in aqueous electrolyte, which impede their practical application. Herein, a negatively charged protection layer combining metal-organic framework (UIO-66-SO3H) and flexible sulfonated poly (ether ether ketone) (SPEEK) binder is introduced on the Zn anode to suppress dendrites and side reactions (denoted as USL-Zn). The USL film with zincophilic –SO3− functional groups uniformizes the Zn2+ flux and guides even Zn deposition. In addition, this protective layer functions as a physical barrier and manipulates the local electrolyte structure to mitigate the hydrogen evolution reaction and passivation on Zn anode surface. As a result, USL-Zn electrodes deliver high cycling stability at various current densities and capacities (700 h at 5 mA cm−2, 5 mAh cm−2 and 300 h at 10 mA cm−2, 10 mAh cm−2), and enable high average Coulombic efficiency of 99.34 % (1 mA cm−2 for 1 h). Moreover, enhanced rate capacity and prolonged lifespan can be attained in Zn//VO2 full cells. This proposed strategy provides insight into the design of SEI layers in aqueous batteries and promotes the potential application of Zn metal batteries.