Formulation of electrodes for aqueous-based systems, focusing on improving the performance of zinc-ion batteries through advanced coatings

Aqueous zinc-ion batteries (ZIBs) offer a high theoretical capacity of 820 mAh/g with benefits such as safety, low cost, and sustainability. However, their performance is limited by persistent issues during reversible zinc cycling, especially dendrite formation, interfacial instability, and side reactions with aqueous electrolytes, which lower zinc utilization, promote hydrogen evolution, and degrade electrolyte integrity. To address these challenges, this work explores the use of a zeolitic imidazolate framework-8 (ZIF-8) coating on zinc anodes, leveraging its microporous structure, mechanical strength, zincophilic sites, and high ionic conductivity to regulate Zn²⁺ deposition and stabilize interfaces. Three cell types were fabricated: symmetric (bare Zn/Zn, ZIF@Zn/ZIF@Zn), asymmetric (bare Zn/Ti, ZIF@Zn/Ti), and full cells with MnO₂-coated titanium cathodes (Zn/MnO₂@Ti, ZIF@Zn/MnO₂@Ti). Electrodes were prepared by optimized blade-coating, and all electrochemical tests used standardized conditions. Electrochemical impedance spectroscopy, cyclic voltammetry, rate performance, and constant current cycling showed that ZIF-8-coated zinc anodes had lower charge transfer resistance, reduced polarization, and more stable voltage profiles than bare Zn. In symmetric cells at 2 mA cm⁻², ZIF@Zn cycled stably for 782 h, with a cumulative areal discharge of 2071.2 mAh cm⁻² over 2072 cycles, showing improved reversibility and stability. Asymmetric ZIF@Zn/Ti cells delivered a stable stripping capacity of 893.2 mAh/g at 70 cycles, outperforming bare Zn/Ti. Full cell results showed ZIF@Zn/MnO₂@Ti achieved a discharge capacity of 94.74 mAh/g and 99.2% coulombic efficiency after 100 cycles, cycling over 500 cycles, while the uncoated cell failed after 260 cycles. ZIF-8 enhanced redox kinetics and Zn²⁺ intercalation, as seen by higher, shifted redox peaks in CV profiles.