Effect of lithium ion concentration on the microstructure evolution and its association with the ionic conductivity of cubic garnet-type nominal Li7Al0.25La3Zr2O12 solid electrolytes

The Li + concentration in nominal Li 7 Al 0.25 La 3 Zr 2 O 12 (LALZO) solid electrolyte are believed to pose significant effect on its electrical conductivity . The affecting mechanism of Li + concentration on microstructure evolution and its relationship with Li ionic conductivity is investigated. Results show that Li + occupancy in octahedral site (LiO 6 ) increases with the increase of Li + concentration and Li + arrangement becomes a certain degree ordered in tetragonal site (LiO 4 ) at 6.72   moles Li + concentration. The structural evolution indicates that higher Li + concentration in LiO 6 as well as disordered Li + arrangement in LiO 4 will enhance the grain conductivity which infers the best Li + concentration of 6.35   moles. The tested electrical property show the highest grain ionic conductivity of 1.35   ×   10 −   3   S   cm −   1 at Li + concentration of 6.35   moles which is in good agreement with prediction made from the structural evolution. It is concluded that Li + concentration affects Li ionic conductivity via changing Li + distribution in the grain.