Synthesis of the Materials Used in All-Solid-State Lithium Secondary Batteries

Conventional electrolytes in Li-ion batteries based on organic solvents or polymers with a dissolved Li-salt pose serious limitations such as flammability, difficulty of miniaturization, and serious impact to the environment if poorly disposed of or recycled.

As a replacement, stable inorganic solid electrolyteswith high Li conductivity and suppressed electronic conductivity has become increasingly appealing, with several advantages including nontoxicity, ease of preparation, and low cost.

So far, Li ion conductors with garnet-type structure are considered as promising electrolytes because of their high conductivity and excellent stability.

Li7La3Zr2O12 (LLZO) has recently become of high interest as a result of its potential as a solid state Li-ion conductor, because it has good ionic conductivity (>10−4 S/cm) and is stable against lithium. However, for the case of LLZO two phases exist; cubic and tetragonal.

The cubic phase is preferred, because reports estimate a theoretical lattice conductivity of ~5×10-4 S/cm compared to ~1.6×10−6 S/cm, for the tetragonal phase.

Thus, it is important to understand how to prepare the cubic phase.

In general, calcination temperatures in excess of 1180 °C are required to obtain cubic LLZO.

In this study, we aim to synthesis of cubic LLZO using a hydrothermal synthesis method.