Correlated Migration Invokes Higher Na+‐Ion Conductivity in NaSICON‐Type Solid Electrolytes

Schematic plots of single ion migration and correlated migration mechanism, and the energy barrier profiles for the two diffusion mechanisms in the bc plane in Na3Zr2Si2PO12.

Scientific Achievement

Our theoretical studies reveal that correlated migration is the dominant conduction mechanism in NaSICON-type materials. This can be invoked by increasing the Na+-ion concentration, as confirmed by experimental X-ray diffraction and impedance studies, while neutron diffraction studies identified the existence of a new high energy Na site in the lattice.

Most importantly, an important strategy was experimentally validated to enhance ion conductivity; namely by forcing cations into high-energy sites via repulsive forces, the energy barrier for cation migration can be lowered.

Significance and Impact

The deep understanding on the effects of cation-cation interaction on cation diffusion are beneficial for the design of new highly conductive solid electrolyte materials.

Research Details

  • AIMD and CI-NEB calculations indicate that Na+-ion transport within the NaSICON structure occurs mainly through correlated migration.
  • Increasing Na+-ion concentration leads to increased Coulombic repulsion, further activating correlated migration.
  • The enhanced Na+-ion conductivity stems from the lowered energy barrier for ion conduction by pushing cations into high energy sites.

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DOI: 10.1002/aenm.201902373

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