  Multivalent batteries are an energy storage technology with the potential to
surpass lithium-ion batteries, however their performance has been limited by
the low voltages and poor solid-state ionic mobility of available cathodes. A
computational screening approach to identify high-performance multivalent
intercalation cathodes among materials that do not contain the working ion of
interest has been developed which greatly expands the search space that can be
considered for materials discovery. This approach has been applied to magnesium
cathodes as a proof of concept and four resulting candidate materials (NASICON
V$_2$(PO$_4$)$_3$, birnessite NaMn$_4$O$_8$, tavorite MnPO$_4$F, and spinel
MnO$_2$) are discussed in further detail. In examining the ion migration
environment and associated Mg$^{2+}$ migration energy in these materials, local
energy maxima are found to correspond with pathway positions where Mg$^{2+}$
passes through a plane of anion atoms. While previous works have established
the influence of local coordination on multivalent ion mobility, these results
suggest that considering both the type of local bonding environment as well as
available free volume for the mobile ion along its migration pathway can be
significant for improving solid-state mobility.
