Nanoengineered RF-Sputtered Mn₃O₄ Cathode Thin Films for Aqueous Zinc-Ion Batteries: Insights into Diffusion Dynamics...

Manganese oxides are a promising cathode material for aqueous zinc-ion batteries (AZIBs), but thin-film configurations remain underexplored. This study investigates the electrochemical dynamics of 60 nm thin Mn₃O₄ thin films, fabricated via RF magnetron reactive sputtering. It addresses the highest reported capacity (25 mAh/g) in thin film form, stability over 500 cycles, effective performance across varying current rates, surpassing previous studies and challenges such as phase stability, and capacity fading over extended cycling, aiming to enhance uniformity, minimizing diffusion barriers for improved performance. EIS reveals Zn²⁺ diffusion coefficients of 1.503 × 10^-7, 1.336 × 10^-16, and 1.947 × 10^-20 cm²/s in precycle, charged, and discharged states, respectively, highlighting evolving diffusion dynamics during cycling. Structural instability during discharge leads to a decline in diffusion performance, emphasizing the need for material and interfacial optimizations to enhance stability and mitigate degradation. These findings underscore the critical role of interfacial engineering and structural stability in maintaining high ion diffusion rates and minimizing morphological degradation during cycling. The present study explores the critical role of targeted engineering in unlocking their full potential for lightweight, miniaturized, high-performance microbatteries for energy storage applications.