Low temperature synthesis of Al-doped Li7La3Zr2O12 solid electrolyte by a sol–gel process

• Al-doped Li7La3Zr2O12 (LLZ) was prepared by a sol–gel process.
• Single phase of cubic LLZ was obtained by a heat treatment at 700 °C.
• The LLZ powders were sintered at 900 °C with LiBO2 or Li3BO3.
• In the sintering with LiBO2, La2Zr2O7 was formed.
• In the sintering Li3BO3, single phase of cubic LLZ with dense structure was obtained.

Al-doped Li7La3Zr2O12 (LLZ) was prepared by a sol–gel process using lithium nitrate, lanthanum nitrate hexahydrate, zirconium propoxide and aluminum tri-sec-butoxide as starting materials. Single phase of cubic LLZ was obtained by a heat treatment at 700 °C, which is lower than that in the solid state reaction process. The LLZ powders were sintered at 900 °C using LiBO2 or Li3BO3 to form composite solid electrolyte. In the composite sintered with LiBO2, La2Zr2O7 was formed as an impurity phase. On the other hand, in the composite sintered with Li3BO3, single phase of cubic LLZ was obtained. The composite of Al-doped LLZ and Li3BO3 sintered at 900 °C showed the total electrical conductivity of 1.9 × 10− 5 S cm− 1, while Al-doped LLZ pellet without additives showed 1.6 × 10− 6 S cm− 1.