A fundamental stability study for amorphous LiLaTiO₃ solid electrolyte

In this study, amorphous lithium lanthanum titanate (LLTO) powders were prepared by a sol-gel method with an all alkoxide based route. Results showed that unlike its crystalline counterpart which turns into an electronic conductor in direct contact with lithium metal, amorphous LLTO remains to be an ionic conductor and hence is compatible with lithium metal as solid electrolyte although it also undergoes lithium insertion and the consequent reduction of Ti⁴⁺ to Ti³⁺. This striking difference between crystalline and amorphous LLTO could be ascribed to the atomic configuration difference, ordered versus disordered. The electronic states of a disordered system could be localized. It was found that the transference number of lithium ions of amorphous LLTO is over 82%. Our results on electrochemical measurements indicated that amorphous LLTO is stable with blocking electrodes up to 12 V, which can potentially be used with high voltage cathode materials.