Preparation and Properties of Na_5-xY_1-xZr_xSi₄O₁₂ Sodium-ion Ceramic Solid Electrolyte

In recent years, sodium-ion solid-state batteries have gradually attracted attentions as a member of rechargeable batteries. In solid-state batteries, liquid electrolytes are avoided, thus diminishing the risks such as leakage and explosion. At present, it is still a challenge to increase the ionic conductivity of solid-state electrolytes. In this study, Zr⁴⁺ was introduced into Na₅YSi₄O₁₂ (NYS), where NaNO₃, YN₃O₉·6H₂O, C₈H₂₀O₄Si and ZrO(NO₃)₂·xH₂O were used as starting materials. A solution-assisted solid-phase reaction method (SASSR) was employed to prepare the solid electrolytes Na_5-xY_1-xZr_xSi₄O₁₂ (x=0.04, 0.06, 0.08, 0.10, 0.12) with hexagonal crystal structure. The effect of Zr⁴⁺ on ionic conductivity of Na_5-xY_1-xZr_xSi₄O₁₂ (NYZS) was studied, while the maximum ionic conductivity of 2.13 mS·cm^-1 was achieved at x=0.08, with an activation energy of 0.222 eV. Compared with that of NYS, the conductivity of NYZS is greatly increased, due to the presence of sodium vacancies after Zr⁴⁺ doping. In summary, Na_5-xY_1-xZr_xSi₄O₁₂ is a competitive sodium-ion solid-state electrolyte, which is expected to become promising candidate for new generation of energy conversion.