Revealing Potassium Ion Storage at Individual Prussian Blue Nanoparticles with Distinct Crystallinity via Scanning Electrochemical Cell Microscopy

Abstract

Potassium-ion batteries (KIBs) have gained tremendous attention due to the abundance and low cost of potassium resources. However, challenges such as significant voltage hysteresis and sluggish diffusion kinetics request a deep understanding of the ion storage at the cathode materials. This study investigates the intrinsic electrochemical properties of Prussian blue (PB) nanoparticles, a promising cathode material for KIBs, through single-particle measurements using scanning electrochemical cell microscopy (SECCM). PB nanoparticles with varying crystallinity were prepared by controlling the amount of polyvinylpyrrolidone (PVP) used as a chelating ligand. Our findings reveal that PB nanoparticles with lower crystallinity displayed low K + storage properties, while excessive PVP adsorption on nanoparticle surfaces hampers electrochemical performance. Notably, PB nanoparticles prepared with trace amounts of PVP exhibit significantly enhanced K + storage capabilities due to optimized structural integrity. This research highlights the critical role of particle crystallinity and surface chemistry in tailoring the performance of energy storage materials, providing insights for the design of advanced KIB systems.