LiSr1.65 square 0.35B1.3B ' O-1.7(9) (B = Ti, Zr; B ' = Nb, Ta): New lithium ion conductors based on the perovskite structure

We describe the design and synthesis of new lithium ion conductors with the formula, LiSr(1.65)rectangle(0.35)B(1.3)B'O-1.7(9) (rectangle = vacancy; B = Ti, Zr; B' = Nb, Ta), on the basis of a systematic consideration of the composition-structure-property correlations in the well-known lithium-ion c onductor, La-(2/3-x)Li(3x)rectangle((1/3)-2x)TiO3 (I), as well as the perov skite oxides in Li-A-B,B'-O (A = Ca, Sr, Ba; B = Ti, Zr; B' = Nb, Ta) syste ms. A high lithium-ion conductivity of ca. 0.12 S/cm at 360 degrees C is ex hibited by LiSr(1.65)rectangle(0.35)Ti(1.3)Ta(1.7)O(9) (III) and LiSr(1.65) rectangle(0.35)Zr(1.3)Ta(1.7)O(9) (IV), of which the latter containing stab le Zr(IV) and Ta(V) oxidation states is likely to be a candidate electrolyt e material for all-solid-state lithium battery application. More importantl y, we believe the approach described here could be extended to synthesize n ewer, possibly better, lithium ion conductors.