posted on 2021-07-19, 17:44authored byEunseok Heo, Ji Eun Wang, Jong Hyuk Yun, Joo-Hyung Kim, Dong Jun Kim, Do Kyung Kim
The battery safety and cost remain
major challenges for developing
next-generation rechargeable batteries. All-solid-state sodium (Na)-ion
batteries are a promising option for low-cost as well as safe rechargeable
batteries by using abundant resources and solid electrolytes. However,
the operation of solid-state batteries is limited due to the low ionic
conductivity of solid electrolytes. Therefore, it is essential to
develop new compounds that feature a high ionic conductivity and chemical
stability at room temperature. Herein, we report a potassium-substituted
sodium superionic conductor solid electrolyte, Na3–xKxZr2Si2PO12 (0 ≤ x ≤ 0.2),
that exhibits an ionic conductivity of 7.734 × 10–4 S/cm–1 at room temperature, which is more than
2 times higher than that of the undoped sample. The synchrotron powder
diffraction patterns with Rietveld refinements revealed that the substitution
of large K-ions resulted in an increased unit cell volume, widened
the Na diffusion channel, and shortened the Na–Na distance.
Our work demonstrates that substituting a larger cation on the Na
site effectively widens the ion diffusion channel and consequently
increases the bulk ionic conductivity. Our findings will contribute
to improving the ionic conductivity of the solid electrolytes and
further developing safe next-generation rechargeable batteries.