Synthesis of ZIF-8 powders and their electrochemical role as a protective layer minimizing dendrite formation and elevating anode stability in Zn-ion batteries

Abstract

A Zn-based metal-organic framework (Zn-MOF) was synthesized via a solvothermal process using Zn(NO<inf>3</inf>)<inf>2</inf>·6H<inf>2</inf>O and 2-methylimidazole (2-Hmim) in ethanol at 120 °C for 24 h, yielding a crystalline structure consistent with ZIF-8, exhibiting a high surface area (1820.73 m² g⁻¹) and a large pore size (1.47 nm). The ZIF-8 powder was coated onto a Zn plate (ZIF-8@Zn) and evaluated as a Zn-ion battery anode, demonstrating significantly enhanced cycling stability, with a lifespan up to 200 h across all current densities, outperforming bare Zn (132, 49, 34, 36, and 20 h for 1–5 mA cm⁻²) in a 2 M ZnSO<inf>4</inf> electrolyte. Post-plating/stripping analysis revealed that ZIF-8@Zn maintained a smooth morphology, whereas bare Zn exhibited pronounced roughness and dendrite formation. Cross-sectional SEM images confirmed a swollen ZIF-8 layer with reduced Zn thickness at higher plating/stripping current densities, and XRD analysis detected Zn<inf>4</inf>SO<inf>4</inf>(OH)<inf>6</inf>·4H<inf>2</inf>O and Zn<inf>4</inf>SO<inf>4</inf>(OH)<inf>6</inf>·5H<inf>2</inf>O byproducts on both electrodes. The ZIF-8@Zn||V<inf>2</inf>O<inf>5</inf> full-cell exhibited superior capacity (314.03 vs. 251.75 mAh g⁻¹ at 100 mA g⁻¹) and long-term stability, with a 22.71 % capacity increase after 1000 cycles, in contrast to an 11.52 % reduction in the Zn||V<inf>2</inf>O<inf>5</inf> cell, highlighting ZIF-8@Zn's potential for stable Zn-ion batteries.