A different zirconia precursor for Li7La3Zr2O12 synthesis

Abstract

Li7La3Zr2O12 (LLZO) is a promising solid electrolyte for all-solid-state lithium-ion batteries. Some studies on LLZO synthesis have been conducted without considering the crystal structure of ZrO2 as the main precursor. In this research, different-precursors have been used for LLZO synthesis which was a monoclinic ZrO2 powder (m-ZrO2) and tetragonal ZrO2 powder (t-ZrO2). The reaction was conducted at 950 °C 6 h and followed by sintering at 1000 °C 6 h under Argon gas flow. The result shows that LLZO made from m-ZrO2 (LLZO(A)) and t-ZrO2 (LLZO(B)) contains t-LLZO and c-LLZO which is surprisingly having a similar c/t ratio of 0.124–0.125. The LLZO(A) and LLZO(B) provide a silver blocking ionic conductivity of 1.245 x 10−6 Scm−1 and 1.647 x 10−6 Scm−1, respectively. In addition, LLZO(B) provides lower specific resistance than LLZO(A) in between LiCoO2 and meso-carbon microbeads (mcmb) electrodes. CV analysis of the symmetrical Li-LLZO(B)–Li cell shows an electrochemical potential of 3.3 V (vs Li/Li+) oxidation and 3.4 V reduction (vs Li/Li+). A time-based Galvanostatic charge–discharge to Li-LLZO(B)–Li shows a capacity drop after the 1st 40 cycles from 0.0383C/cm2 into 0.0303C/cm2 during the 2nd 40 cycles, and it remains stable up to 120 cycles. It confirms the long-term electrochemical stability of LLZO(B) which was produced from t-ZrO2. The solid-state reaction method provides less expensive production and environmentally friendly by the absence of organic solvent.

Keywords

• Li7La3Zr2O12
• Crystal structure
• Precursor
• Monoclinic ZrO2
• Tetragonal ZrO2