Percolation-Based Optimization of Zn–MnO₂ Battery Cathodes Balancing Capacity Density and Electrical Conductivity

Abstract This study introduces a novel, systematic approach to maximize electrode-side capacity density in ZMBs without significantly reducing power density. A percolation-based model was developed to evaluate how usable capacity and electrical conductivity vary with the volume fractions of MnO₂, carbon black (CB), and porosity, overcoming the system's dual non-linear scaling behaviour. The model identifies an optimal composition range for any given porosity and was extensively parameterized and validated through a comprehensive set of targeted electrochemical and structural measurements. Applying this optimal composition to a 75 % porosity cathode increased capacity by 25 mAh cm⁻² (290 mAh g⁻¹) compared to conventional cathodes without preloaded active material, while maintaining a high electrical conductivity of 150 S m⁻¹. This work establishes a novel, general framework for designing high-energy-density composite cathodes.