Stabilizing lithium and sodium fast-ion conduction in solid polyhedral-borate salts at device-relevant temperatures

By a variety of techniques including X-ray powder diffraction, quasielastic neutron scattering, and AC impedance, we have probed the effect of mechanical milling on the phase behaviors of the different lithium and sodium closo-borate salt compounds containing B12H122-, B10H102-, and CB11H12- anions. We have found that the crystallite-size reduction and disordering effects of such milling enables the room-T stabilization of their high-T-like superionic-conducting phases. This demonstrates a viable strategy for better exploiting the impressive cation mobilities that are typically restricted to somewhat higher temperatures for this class of compounds.