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.
- 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.