High-throughput computational discovery of K2CdO2 as an ion conductor for solid-state potassium-ion batteries

Abstract

Inorganic fast ion conductors play an important role in next generation solid-state battery technology, but solid superionic phases are rarely discovered because of the complex relationship between ion transportation and atomic structures. Our screening scheme by a series of high-throughput simulations selects a candidate, K₂CdO₂, for solid potassium ion conductors from 1389 K-containing oxide structures in the Inorganic Crystal Structure Database (ICSD). The migration behavior with very low barriers of 40 meV for a vacancy-assisted mechanism and 13 meV for an interstitial-assisted mechanism is revealed in K₂CdO₂ through nudged elastic band simulations. The evaluation of the defect formation energies indicates that the difficulties in creating vacancies or interstitial carriers are the reason for the limited ionic conductivity of this system. Thus, the scheme of Al-doped K₂CdO₂, aiming at increasing the carrier concentration, is proposed and its effect on further improving the ionic conductivity is confirmed by first-principles molecular dynamic simulations.