Changes in local structure during electrochemical Li insertion into A-site deficient perovskite oxides, La1/3NbO3

A detailed investigation of the local structural changes with lithiated perovskite oxides, LixLa1/3NbO3, has been carried out using extended X-ray absorption fine structure (EXAFS) measurements. From Nb K-edge EXAFS measurement, the interatomic distance of first shell Nb-O interaction increased with the composition x by electrochemical Li-x insertion. This behavior ascribed to the expansion of Nb ion due to the reduction of Nb5+ to Nb4+. On the other hand, La K-edge EXAFS measurement showed that the interatomic distance of the first shell La-O interaction decreased with the lithiation reaction. Furthermore, those of second shell Nb-La and third shell Nb-Nb and La-La bonds tended to be unchanged with reaction. Such a complicated behavior in the change of each interatomic distance with lithium insertion can be understood by the model of tilting of NbO6 octahedra in the perovskite structure.