Materials Design Rules for Multivalent Ion Mobility
in Intercalation Structures
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Abstract
The diffusion of ions in solid materials
plays an important role
in many aspects of materials science such as the geological evolution
of minerals, materials synthesis, and in device performance across
several technologies. For example, the realization of multivalent
(MV) batteries, which offer a realistic route to superseding the electrochemical
performance of Li-ion batteries, hinges on the discovery of host materials
that possess adequate mobility of the MV intercalant to support reasonable
charge and discharge times. This has proven especially challenging,
motivating the current investigation of ion mobility (Li<sup>+</sup>, Mg<sup>2+</sup>, Zn<sup>2+</sup>, Ca<sup>2+</sup>, and Al<sup>3+</sup>) in spinel Mn<sub>2</sub>O<sub>4</sub>, olivine FePO<sub>4</sub>, layered NiO<sub>2</sub>, and orthorhombic δ-V<sub>2</sub>O<sub>5</sub>. In this study, we not only quantitatively assess these
structures as candidate cathode materials, but also isolate the chemical
and structural descriptors that govern MV diffusion. Our finding that
matching the intercalant site preference to the diffusion path topology
of the host structure controls mobility more than any other factor
leads to practical and implementable guidelines to find fast-diffusing
MV ion conductors