A P2‐Type Layered Superionic Conductor Ga‐Doped Na 2 Zn 2 TeO 6 for All‐Solid‐State Sodium‐Ion Batteries

Here, a P2‐type layered Na 2 Zn 2 TeO 6 (NZTO) is reported with a high Na + ion conductivity ≈0.6×10 −3  S cm −1 at room temperature (RT), which is comparable to the currently best Na 1+ n Zr 2 Si n P 3− n O 12 NASICON structure. As small amounts of Ga 3+ substitutes for Zn 2+ , more Na + vacancies are introduced in the interlayer gaps, which greatly reduces strong Na + –Na + coulomb interactions. Ga‐substituted NZTO exhibits a superionic conductivity of ≈1.1×10 −3  S cm −1 at RT, and excellent phase and electrochemical stability. All solid‐state batteries have been successfully assembled with a capacity of ≈70 mAh g −1 over 10 cycles with a rate of 0.2 C at 80 °C. 23 Na nuclear magnetic resonance (NMR) studies on powder samples show intra‐grain (bulk) diffusion coefficients D NMR on the order of 12.35×10 −12  m 2  s −1 at 65 °C that corresponds to a conductivity σ NMR of 8.16×10 −3  S cm −1 , assuming the Nernst–Einstein equation, which thus suggests a new perspective of fast Na + ion conductor for advanced sodium ion batteries.