Low-temperature processing of Garnet-type Ion Conductive Cubic Li7La3Zr2O12 Powders and Films for All Solid-type Li-ion Batteries

Garnet type cubic Li7La3Zr2O12 (LLZO) has recently attracted much attention, because of their higher ionic conductivity among all other current oxide electrolyte systems (Nasicon-type, perovskite-type etc.). However, its crystallization temperature is very high (> 750 oC), hence, many researchers have been aimed to synthesize LLZO at lower calcination temperatures. Synthesized LLZO powders are essentially molded to form green compact with higher density and sintered at higher temperatures (>900 oC), in order to exhibit the higher ionic conductivity for using it as an electrolyte. This step is limiting the practical utility of LLZO in commercial Li-ion batteries. If such oxide electrolytes powders can be designed as paint slurry consisted of the LLZO powders and an appropriate Li-ion conductive binders, we can prepare a complete battery on any arbitrary surface. It would have significant impact on the design, integration and performance of the resulting energy storage devices.Our main objective of this study is to develop LLZO based thick films with high ionic conductivity using a Li-ion conductive binder from LLZO powders and to find an approach to realize all paintable glovebox free Li-ion battery. In this paper, we demonstrate the intensive studies of an advanced energy material i.e. lithium polyacrylate (Li-PAA) binder assisted LLZO paste which is proven to be a surprisingly unique, multifunctional binder for high-voltage Li-ion batteries1. LLZO powders were synthesized at lower calcination temperatures i.e. at 750 oC by novel solid-state reaction (Two-step reaction). LLZO thick films were developed on Cu foil using Li-PAA binder. XRD, Raman, FTIR, FE-SEM and TEM measurements were conducted to investigate crystallographic and microstructural characteristics of the films. As a result, the impedance plot for the LLZO films delivered an ionic conductivity of 8.3 ☓10-5 S/cm. Further an attempt have been made to realize all solid type paintable Li-ion battery, and corresponding electrochemical observations have been discussed.