Gallium-substituted Nasicon Na3Zr2Si2PO12 solid electrolytes

As a possible solid electrolyte material for solid-state sodium-based batteries, gallium-substituted Na3Zr2Si2PO12 in the structure of Nasicon (sodium super ion conductor) has received hardly any attention so far, though Ga3+ has similar ionic radius close to that of Zr4+. Herein, a series of gallium-substituted Na3Zr2Si2PO12 with formula of Na3+xZr2-xGaxSi2PO12 (0 ≤ x ≤ 0.4) have been prepared through solid-state synthesis. The electrical, microstructural, and crystallographic performances of the developed solid electrolytes are systematically studied. In particular, the gallium-substituted Na3.1Zr1.9Ga0.1Si2PO12 shows superior ionic conductivity of 1.06 × 10−3 S cm−1 at 25 °C, which is almost one order of magnitude higher than that of the pristine Na3Zr2Si2PO12, as well as low electronic conductivity of 6.17 × 10−8 S cm−1 and wide electrochemical stability window of 5 V vs. Na/Na+. This work demonstrates a new substituted strategy for exploring Na+-ion solid electrolytes. [Display omitted] •Substitution of Ga3+ for octahedral Zr4+ in Na3Zr2Si2PO12 is proposed.•Tenfold increase in conductivity for Na3.1Zr1.9Ga0.1Si2PO12 is achieved.•Conductivity dependence of bottleneck is demonstrated.