High-throughput Computational Discovery of K2CdO2 as an Ion Conductor for Solid-State Potassium-Ion Batteries
Inorganic fast ion conductors play an important role for the next generation solid-state battery technology, but rare solid superionic phases are discovered because of the complex relationship between ion transportation and atomic structures. Our screening scheme by a series of high-throughput simulations select a candidate, K2CdO2, for solid potassium ion conductors from 1389 K-contained oxide structures in the Inorganic Crystal Structure Database (ICSD). The migration behavior with very low barriers of 40 meV for vacancy-assisted mechanism and 13 meV for intersitital-assisted mechanism is revealed in K2CdO2 through the nudged elastic band simulations. The evaluation of the defect formation energies indicates that the difficulities to create vacancy or interstitial carriers are the reason to limit its ionic conductivity in this system. Thus, the scheme of Al-doped K2CdO2, aiming at increase the carrier concentraion, is proposed and its effect on further imporving the ionic conductivity is confirmed by the ab-initio molecular dyanmic simulations.