Synthesis, ionic conductivity, and chemical compatibility of garnet-like lithium ionic conductor Li 5La 3Bi 2O 12

Abstract

Garnet-like Li 5La 3Bi 2O 12 powders with particle size of 80–100 nm were prepared by the Pechini method using lithium carbonate, bismuth nitrate, and lanthanum nitrate as precursors, and high density Li 5La 3Bi 2O 12 ceramics were synthesized at 1023 K from these powders. The lowest temperature to synthesize the pure garnet-like Li 5La 3Bi 2O 12 phase is only 923 K by the Pechini method, 125 K lower than that in the solid state reaction method, and the reaction time in the Pechini method (~ 5 h) is much shorter than that in the solid state reaction route (~ 48 h). The total (bulk plus grain boundary) conductivity of polycrystalline Li 5La 3Bi 2O 12 ceramics prepared by the Pechini method was as high as 2.4 × 10 −5 S/cm at room temperature with an activation energy of 0.40 eV. The Li 5La 3Bi 2O 12 compounds were chemically stable against the widely used cathode materials LiCoO 2 up to 873 K but not chemically stable against the LiMn 2O 4 if the temperature is higher than 673 K.