Processing and Enhanced Electrochemical Properties of Li7La3Zr2−xTixO12 Solid Electrolyte by Chemical Co-precipitation

Garnet-like solid electrolyte ceramics, Li7La3Zr2−xTixO12 (LLZTO, x = 0, 0.1, 0.2, and 0.3), were successfully synthesized at low temperature via chemical co-precipitation. The composition and phase transformation during the heating of the LLZTO precursors are analyzed using thermal gravimetric and differential thermal analysis and x-ray diffraction. The results indicated that 900°C was the likely activation point of LLZTO precursor powder crystallization and all the samples sintered at 1120°C formed a single phase with cubic garnet-like structure. The different morphologies of the LLZTO are characterized using scanning electron microscopy. As the content of Ti increased, the grain size increased to 20 μm, and few pores are observed on the grain boundaries. Additionally, Ti doping increased the ionic conductivity of LLZO ceramics: the sample with x = 0.1 reaches a maximum total ionic conductivity of 1.91 × 10−4 S cm−1 at 298 K and its activation energy is 0.33 eV, which may be a significant step towards the goal of an ultimate safe solid electrolyte of a solid-state lithium ion battery.