Among all-solid-state batteries, rechargeable Al-ion batteries have attracted most attention because they involve threeelectron-redox reactions with high theoretic specific capacity. However, the solid Al-ion conductor electrolytes are less studied. Here, the microscopic path of Al^(3+)-ion conduction of NASICON-type(Al_(0.2)Zr_(0.8))_(20/19)Nb(PO_4)_3 oxide is identified by temperature-dependent neutron powder diffraction and aberration-corrected scanning transmission electron microscopy experiments.(Al_(0.2) Zr_(0.8))_(20/19) Nb(PO_4)_3 shows a rhombohedral structure consisting of a framework of(Zr,Nb)O_6 octahedra sharing corners with(PO_4) tetrahedra; the Al occupy trigonal antiprisms exhibiting extremely large displacement factors. This suggests a strong displacement of Al ions along the c axis of the unit cell as they diffuse across the structure by a vacancy mechanism. Negative thermal expansion behavior is also identified along a and b axes, due to folding of the framework as temperature increases.
王捷孙春文巩玉栋张怀若Jose Antonio AlonsoMaría Teresa Fernández-Díaz王中林John B Goodenough
