ENGINEERING THE PERFORMANCE AND STABILITY OF GARNET-RELATED LITHIUM LANTHANUM ZIRCONIUM OXIDE (LI7LA3ZR2O12) IN ALL-SOLID-STATE LITHIUM BATTERIES

Abstract

Garnet-type Li7La3Zr2O12 is a promising solid electrolyte due to its high Li+ ion conductivity and stability against metallic lithium. However, Li+ can be exchanged by protons in the presence of moisture, which poses concerns about the suitability of garnets as solid electrolytes. Here, the formation mechanism of Ta-Ga co-doped garnet, Li6.75La2.95Zr1.75Ta0.25Ga0.05O12 and its chemical stability against humidity is studied. It is found that Li+/H+ occurs spontaneously turning the fast Li+ conductor Li6.75La2.95Zr1.75Ta0.25Ga0.05O12 into a moderate H+ conductor on long-time water immersion. In order to realize all-solid-state lithium batteries using garnet solid electrolyte, a compatible electrodes composite slurry is explored for direct tape casting on the garnet phase thereby reducing the solid electrode|electrolyte interface while preserving the properties of the pristine cubic garnet phase. Lastly, an all-solid-state lithium-ion full-cell is realized combining Li6.75La2.95Zr1.75Ta0.25Ga0.05O12 with LiFePO4 cathode and Li4Ti5O12 anode composites achieving a reversible capacity of 62 mAh/g at 60 °C.