A comprehensive computational approach is used to discover potential multivalent (MV)-ion conducting solid electrolytes (SEs) based on the anti-perovskite (AP) crystal structure.
Significance and Impact
Materials with improved performance are needed to make MV batteries viable. Here, ten candidate MV SEs are investigated: Mg3NX, Ca3NX (X = P, As, Sb, or Bi), Ca3PSb, and Ca3AsSb. Out of these candidates, 3 promising compositions, Mg3NAs, Ca3NAs, and Ca3PSb, are predicted to exhibit sufficient ion mobility and stability to warrant further experimental study.
- Several properties of the AP SEs were predicted using first-principles calculations: stability, band gaps, elastic moduli, ion migration barriers, and defect formation energies. All compounds are predicted to be stable at 0 K.
- The most-promising compounds identified, Mg3NAs, Ca3NAs, and Ca3PSb, are predicted to be stable against their respective metal anodes and have percolating barriers for vacancy migration of <∼500 meV (<∼200 meV for interstitial migration).
- Large energies for the formation of vacancies and interstitials in the APs imply that achieving high conductivities will require that defect concentrations are controlled via doping or with compositions that create vacancies or interstitials on the cation sublattice.