Achieving high performance for aluminum stabilized Li 7 La 3 Zr 2 O 12 solid electrolytes for all solid‐state Li‐ion batteries: A thermodynamic point of view

Summary For the solid‐state reaction synthesis of Al containing Li 7 La 3 Zr 2 O 12 , various precursors have been used. Since there is a lack of general agreement for choosing precursors, a quantitative approach to build a consensus is required. In this study, a thermodynamic point of view for selecting the precursors in the field of Li 7 La 3 Zr 2 O 12 synthesis was covered according to the Gibbs free energy and enthalpy change of precursors' decomposition reactions. In terms of Gibbs free energy change calculations, LiOH, La(OH) 3 , and Al(OH) 3 were favorable whereas, LiOH, La 2 O 3 , and Al(OH) 3 were the preferred precursors for the enthalpy change calculations. Pellets prepared by using the favored precursors calculated from enthalpy change showed improved densification, higher ionic conductivity (2.11 × 10 −4  S/cm), and lower activation energy (0.23 eV) compared with Gibbs free energy change. As a thermodynamically favored aluminum precursor, Al(OH) 3 was discussed in the present study and hinders the ionic conductivity in comparison to Al 2 O 3 .