Modified solid-state metathesis route to ternary lithium silicon nitrides: Li2SiN2

Ternary nitride Li2SiN2, a promising fast ionic conductor, has been successfully synthesized by using SiO2, SiO or Si and Li3N as precursors via a simple modified solid-state metathesis (exchange) route. All the reflections of Li2SiN2 before 50° in 2θ can be well indexed on the basis of a primitive tetragonal cell with a lattice parameter of a = 9.902(1) Å and c = 15.012(5) Å. It has been found that X-ray-pure phase of Li2SiN2 can be definitely obtained by three kinds of silicon sources and the formation of lithia or Li14.10Si6 is likely to be serving as the driving force. By varying the ratio of Li3N to silicon sources, only Li2SiN2 can be approached. Ionic conductivity measurements showed a conductivity of 1.26 × 10− 3 S cm− 1 at 730 K. This study provides a low-cost and facile pathway to Li2SiN2 without the assistance of any addition.