Conductivity versus structure dependence investigation of Na1+xZr2SixP3-xO12 (0 ≤ x ≤ 3) through composition optimization by adjusting Si/P ratio

Presently, the low ionic conductivity of Na super ionic conductor (NASICON) electrolytes is one of the main obstacles to the development of solid-state sodium batteries . Most researchers focus on the modified NASICON by doping with foreign elements and have not paid much attention to the effect of the composition changing by adjusting the ratio of elements in Na 1+x Zr 2 Si x P 3-x O 12 (0 ≤ x ≤ 3) on the ionic conductivity . In order to clarify the relationship between the ionic conductivity and the structure/composition of Na 1+x Zr 2 Si x P 3-x O 12 , the ionic conductivity dependence on the Si/P ratio is systematically investigated in this study. The obtained results demonstrate that the ionic conductivity variation of NASICON is close to an order of magnitude i.e. the ionic conductivity of Na 1+x Zr 2 Si x P 3-x O 12 is much more sensitive to the Si/P ratio in the structure. This means that it is crucial to control the composition during the preparation process to obtain the electrolyte with high ionic conductivity. The strong composition-dependent property of Na 1+x Zr 2 Si x P 3-x O 12 can be attributed to the change of current carrier concentration, crystal structure, and sintering property resulting from the Si/P ratio. The results are insightful for further understanding the conducting characteristics of Na 1+x Zr 2 Si x P 3-x O 12 material and its derivatives.