In situ defect engineering in a multifunctional layer with strong zincophilicity and high Zn-ion conductivity on Zn anodes

Abstract

Aqueous zinc ion batteries (AZIBs) are characterized by environmental friendliness, high safety and low cost, but dendrite growth, hydrogen evolution and interfacial side reactions of Zn anodes seriously hamper their industrial commercialization. Herein, a defective zinc-based metal–organic framework (DZ-MOF) multifunctional layer composed of upright nanosheets and compactly anchored nanoparticles is in situ constructed on the metallic Zn foil surface. Different from the traditionally protective layers with zincophilicity or solid electrolyte interphase (SEI) layers with ionic conductivity on Zn anodes, the DZ-MOF layer possesses both strong zincophilicity and high Zn-ion conductivity. Specifically, the outer upright nanosheets of the unique dual-layer structure with open ionic channels can effectively regulate a homogeneous electrolyte ion flux and facilitate Zn ion transport; the inner compactly anchored nanoparticles are able to isolate the Zn anode from the aqueous electrolyte to alleviate hydrogen evolution and corrosion reactions. Moreover, the well-dispersed defects in the DZ-MOF offer homogeneous electric field distribution and sufficient ionic desolvation and nucleation sites to accelerate the kinetics of [Zn(H₂O)₆]²⁺ desolvation, the Zn²⁺ transport process (Zn²⁺ transference number is 0.721) and uniform Zn deposition, which enables a dendrite-free Zn anode. Thanks to the DZ-MOF multifunctional protective layer, the Zn@DZ-MOF//Zn@DZ-MOF symmetric batteries survive up to 2650 h at 1 mA cm⁻², and Zn@DZ-MOF//I₂ full batteries exhibit excellent rate and cycle performances (99.0% capacity retention and 99.95% coulombic efficiency over 2000 cycles).