cm9b00207_si_001.pdf (27.46 MB)
Solid-State Divalent Ion Conduction in ZnPS3
journal contribution
posted on 2019-03-15, 00:00 authored by Andrew
J. Martinolich, Cheng-Wei Lee, I-Te Lu, Sarah C. Bevilacqua, Molleigh B. Preefer, Marco Bernardi, André Schleife, Kimberly A. SeeNext-generation batteries based on
divalent working ions have the
potential to both reduce the cost of energy storage devices and increase
performance. Examples of promising divalent systems include those
based on Mg2+, Ca2+, and Zn2+ working
ions. Development of such technologies is slow, however, in part due
to the difficulty associated with divalent cation conduction in the
solid state. Divalent ion conduction is especially challenging in
insulating materials that would be useful as solid-state electrolytes
or protecting layers on the surfaces of metal anodes. Furthermore,
there are no reports of divalent cation conduction in insulating,
inorganic materials at reasonable temperatures, prohibiting the development
of structure–property relationships. Here, we report Zn2+ conduction in insulating ZnPS3, demonstrating
divalent ionic conductivity in an ordered, inorganic lattice near
room temperature. Importantly, the activation energy associated with
the bulk conductivity is low, 351 ± 99 meV, comparable to some
Li+ conductors such as LTTO, although not as low as the
superionic Li+ conductors. First-principles calculations
suggest that the barrier corresponds to vacancy-mediated diffusion.
Assessment of the structural distortions observed along the ion diffusion
pathways suggests that an increase in the P–P–S bond
angle in the [P2S6]4– moiety
accommodates the Zn2+ as it passes through the high-energy
intermediate coordination environments. ZnPS3 now represents
a baseline material family to begin developing the structure–property
relationships that control divalent ion diffusion and conduction in
insulating solid-state hosts.