Optimized Synthesis of Multi Metal Prussian Blue Analogues Towards Stable Sodium-Ion Battery Cathode

Abstract

Sodium-ion batteries are increasingly considered a viable alternative to lithium-ion systems for large-scale (stationary) energy storage due to the abundance and low cost of sodium. Among potential cathode materials, Prussian Blue Analogues (PBAs) offer fast sodium-ion diffusion and high operating voltages but often suffer from structural instability and capacity fading during long-term cycling. In this study, multi-metal Prussian Blue Analogues are developed to overcome these limitations by stabilising the framework and enhancing electrochemical performance through synergistic interactions between multiple transition metals. The materials were synthesised using controlled co-precipitation and hydrothermal methods, enabling precise control over composition, morphology, and defect concentration. Structural and electrochemical characterisation using X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic charge–discharge testing, and electrochemical impedance spectroscopy demonstrates improved crystallinity, reduced polarisation, enhanced rate capability, and superior cycling stability compared with single-metal PBAs. The improved performance is attributed to enhanced redox activity and improved structural integrity during repeated sodium insertion and extraction. These results highlight multi-metal Prussian Blue Analogues as promising cathode materials for scalable and durable sodium-ion batteries intended for stationary and grid-level energy storage applications.