Garnet-type solid electrolyte and method for preparing the same

A method for preparing a garnet solid electrolyte including Al which substitutes at least a portion of Li, the method comprising:

• preparing a mixture of LiOH, La(OH)3, ZrO2, and Al2O3;
• first calcinating the mixture for 5 to 7 hours at 800 to 1000° C.;
• dry mixing the calcinated mixture after natural cooling;
• preparing pellets of 8 to 12 mm using 10 to 80% by weight of the mixture at 120 to 150 MPa, and covering the pellets with the remaining mixture in a powder state;
• and
• preparing a cubic phase garnet solid electrolyte by second calcinating the prepared pellets for 10 to 40 hours at 1100 to 1300° C.