Preparation of Li7La3Zr2O12 solid electrolyte via a sol–gel method

In this research, Li7La3Zr2O12 (LLZ), which has been recognized as a promising solid electrolyte for next-generation Li-ion batteries, is prepared by a sol–gel method to lower the calcination temperature. A precursor sol is prepared from lithium acetate, lanthanum acetate and zirconium tetrabutoxide. After gelation, the gel is heated at 700 °C, and a white powder, which consisted mainly of La2Zr2O7, is obtained. Sintered pellets are prepared by calcination at 1000 °C or 1100 °C. The tetragonal-phase LLZ with low Li-ion conductivity is contained in the pellet calcined at 1000 °C. After the calcination at 1100 °C, the tetragonal LLZ transforms into a cubic phase which possesses high Li-ion conductivity. With the sol–gel method, the cubic-phase LLZ can be obtained after calcination at 1100 °C, which is 130 °C lower than the temperature in conventional solid-state reaction. The Li-ion conductivity of the prepared cubic LLZ is 1.5×10−4 S cm−1, which is comparable with the previously reported values. It is concluded that the cubic LLZ with high Li-ion conductivity can be successfully prepared at low temperature using the sol–gel method.