Elucidating the Process–Structure–Property Relationships in Spray-Dried K3V2(PO4)3/C Microspheres for High-Performance Potassium-Ion Batteries

Polyanion-based K3V2(PO4)3 (KVP) has emerged as a promising cathode material for potassium-ion batteries (KIBs); however, its practical application is severely hindered by intrinsically low electronic conductivity and structural degradation during cycling. Although spray-drying (SD) has been suggested as a scalable solution for constructing uniform 3D microspheres, conventional empirical optimization leaves a critical knowledge gap regarding how synthesis variables dictate the microstructural evolution. Herein, we systematically engineer high-performance KVP/carbon microspheres by precisely elucidating the process–structure–property relationships. We comprehensively investigate the synergistic effects of the calcination temperature and the citric acid (CA) ratio, where CA acts as a vital dual agent for precursor chelation and in situ carbonization. Our analysis reveals that precise parameter control is imperative to prevent premature crust-induced droplet rupture and multi-phase impurity formation. Consequently, the optimized KVP-0.5-750 composite secures a highly crystalline framework integrated with a conformal, conductive carbon network (9.2 wt %). This tailored architecture drastically accelerates electron/ion transport kinetics and effectively buffers mechanical stress during repeated K+ (de)intercalation. As visually confirmed by ex situ analysis, this matrix completely prevents particle pulverization, enabling outstanding cycling stability with 42 mA h g−1 retained after 200 cycles, while exhibiting exceptional practical viability in full-cell configurations.