GarnetT-PEO Composite Solid Electrolytes: A Multiscale View on Li~+ Transport

摘要

The fast-expanding sector of portable electronics and electric vehicles look for new solutions to overcome safety and performance limitations of liquid electrolyte-based Li-ion batteries. A promising new technology is the so-called Li metal Solid State Battery (SSB), which aims to replace the flammable liquid electrolyte by solid electrolyte materials, such as ceramics or polymers. Ceramic electrolytes are the best candidates for SSB in terms of high Li~+ conductivity, though they are strongly limited by their interfacial mechanical stability with Li metal anode [1]. An alternative is to combine the desirable properties of ceramic and polymeric electrolytes into a composite concept. Generating knowledge about interactions between composite components and their influence on Li-ion mobility, electrochemical stability and Li electrodeposition properties is thus, essential to progress towards practical applications. In this contribution, we focus on the composite solid electrolyte system based on PEOLiTFSI polymeric matrix enriched with Li_(6.55)La3Zr2Ga_(0.15)O_(12) garnet fillers [2].To accurately investigate the Li-ion transport properties and avoid the typical segregation issues of these immiscible mixtures, we apply a new processing method that ensures a high degree of structural and chemical homogeneity, even at the local scale, and across a broad range of ceramic filler content. Solid-state NMR and Electron microscopy were used to locally characterize the structure of the composites. The local mobility of Li-ion was investigated by 2D NMR to understand and propose possible transport mechanism. The effect of garnet filler on salt dissociation, ions interactions and correlation between local and global ion nobilities were reconsidered. The impact of garnet filler content on the macroscopic Li-ion conductivity will be discussed as well as their influence on mechanical behavior and the polymer matrix stability with metallic Li anode. Finally, the implementation of these composite electrolytes in Li metal all-solid-state full cell device will be presented. All in all, in this work we show how the combination of hard-soft electrolyte materials can enhance the interfacial stability with Li metal anode upon cycling, offering new opportunities to prevent Li dendrite formation in solid-state batteries.