Abstract
Antiperovskite structure compounds (X3AB, where X is an alkali cation and A and B are anions) have the potential for highly correlated motion between the cation and a cluster anion on the A or B site. This so-called “paddle-wheel” mechanism may be the basis for enhanced cation mobility in solid electrolytes. Through combined experiments and modeling, the first instance of a double paddle-wheel mechanism, leading to fast sodium ion conduction in the antiperovskite Na3−xO1−x(NH2)x(BH4), is shown. As the concentration of amide (NH2−) cluster anions is increased, large positive deviations in ionic conductivity above that predicted from a vacancy diffusion model are observed. Using electrochemical impedance spectroscopy, powder X-ray diffraction, synchrotron X-ray diffraction, neutron diffraction, ab initio molecular dynamics simulations, and NMR, the cluster anion rotational dynamics are characterized and it is found that cation mobility is influenced by the rotation of both NH2− and BH4− species, resulting in sodium ion conductivity a factor of 102 higher at x = 1 than expected for the vacancy mechanism alone. Generalization of this phenomenon to other compounds could accelerate fast ion conductor exploration and design.
Original language | English |
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Article number | 2203284 |
Journal | Advanced Energy Materials |
Volume | 13 |
Issue number | 7 |
DOIs | |
State | Published - Feb 17 2023 |
Funding
P.‐C.T. and S.M. contributed equally to this work. The authors thank Dr. Hasan Celik and UC Berkeley's NMR facility in the College of Chemistry (CoC‐NMR) for spectroscopic assistance. This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. This work made use of the MRL Materials Research Science and Engineering Center (MRSEC) Shared Experimental Facilities at MIT, supported by the National Science Foundation under Award DMR‐1419807. P.‐C.T. thanks the Ministry of Science and Technology, Taiwan, for postdoctoral fellowship support (MOST 110‐2222‐E‐011‐006‐MY3). P.-C.T. and S.M. contributed equally to this work. The authors thank Dr. Hasan Celik and UC Berkeley's NMR facility in the College of Chemistry (CoC-NMR) for spectroscopic assistance. This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. This work made use of the MRL Materials Research Science and Engineering Center (MRSEC) Shared Experimental Facilities at MIT, supported by the National Science Foundation under Award DMR-1419807. P.-C.T. thanks the Ministry of Science and Technology, Taiwan, for postdoctoral fellowship support (MOST 110-2222-E-011-006-MY3). Neutron powder diffraction measurements used resources at the Spallation Neutron Source (NOMAD), a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This research used 11-BM beamline and electrochemistry laboratory resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The sentences regarding neutron powder diffraction measurements and the Advanced Photon Source were added to the acknowledgements after initial online publication, on February 17, 2023.
Keywords
- anion dynamics
- paddle-wheel effect
- solid-state electrolytes