Synthesis, structure and Ionic conductivity of pyrochlore-structured LiSrB_2O_6F (B = Nb~(+5), Ta~(+5))

摘要

Lithium ion conductors have attracted much attention for use as solid electrolytes in all-solid-state batteries. Among the solid electrolyte materials proposed, lithium containing oxides are attractive due to their high ionic conductivity and chemical stability over a wide range of operation temperature. However, discovering novel materials is still necessary to satisfy the strict demands of electrochemical devices. Wide verities of structured material have been reported to offer Li-ion conductivities, however, pyrochlore structure with general formula AA'B_2O_6 has not been investigated in details as a lithium ion conductor. In this study, the pyrochlore structure materials LiSrB_2O_6F (B = Nb and Ta) have being focused. Oxy-fluorides, LiSrB_2O_6F, Li_(1+x)Sr_(1-x)B_(2-x)Zr_xO_6F (interstitial lithium system) and LiSr_(1-x)B_2O_6F_(1-2x) (strontium and fluorine vacancy system) solid solutions, were synthesized by a high-pressure method for obtaining the single phase. The crystal structures and ionic conductivities of these solid solutions were investigated and lithium conduction mechanisms in pyrochlore structure are discussed. .