High-throughput screening of phosphide compounds for potassium-ion conductive cathode application

Cathode materials are crucial in potassium (K) batteries, directly impacting their performance and lifespan. In this study, we used a combination of geometrical-topological (GT) analysis, bond valence site energy (BVSE), Kinetic Monte Carlo (KMC), and first-principles calculations to screen potential cathode materials for K-ion batteries among inorganic phosphides. Through GT analysis, we screened 143 K- and P-containing compounds and identified 30 with two- or three-dimensional K-ion migration pathways. BVSE further narrowed down 13 compounds with K-ion migration energies below 1 eV. KMC simulations of ionic conductivity led to the selection of K3Cu3P2 for detailed first-principles calculations. It was demonstrated that K3Cu3P2 possesses a reversible capacity of 72.47 mAh·g-1, minimal volume change (1.47%), and a charge compensation mechanism involving Cu and P. Its low migration energy barrier contributes to a high ionic diffusion coefficient and conductivity of 1.87 × 10-3 S·cm-1 at 25 °C, making K3Cu3P2 a promising candidate for stable and efficient K-ion diffusion in cathode applications.