Three-dimensional porous ceramic framework reinforcing composite electrolyte

Abstract

All solid-state lithium batteries demonstrate excellent characteristics of high safety and energy density, which make them very promising energy storage devices. Among various kinds of solid electrolytes, rigid-flexible coupling composite electrolyte combines the advantages of rigid solid inorganic ceramic electrolytes, i.e., excellent room temperature ionic conductivity, and of flexible solid polymer electrolytes, i.e., the flexibility, and thereby is considered to be one of the most ideal electrolyte candidates for all solid-state lithium batteries. Dispersing 0- or 1-dimensional inorganic fillers is a widespread method to fabricate rigid-flexible coupling composite, where the ionic conductivity of polymer can be improved by one order of magnitude mainly due to the decreased degree of crystallinity. However, aim to further increase the ionic conductivity by increasing the filler content cannot be accomplished because of the fillers' tendency to aggregation. what's more, the highly conductive inorganic fillers are separated by the polymer phase and thus cannot form fast and continuous Li<sup>+</sup> transportation channels. Accordingly, inorganic fillers which can provide percolated pathway for Li<sup>+</sup> transportation and avoid aggregating are highly desirable. To this end, different from adding 0- or 1-dimensional inorganic fillers into polymer matrices, polymers can be cast into porous inorganic substrates, that is, 3-dimensional porous ceramic framework, to obtain organic-inorganic composite electrolyte, in which organic phase, inorganic phase, and organic/inorganic interfacial phase are all continuous for fast Li<sup>+</sup> transportation. And meanwhile, its self-supported structure prevents the agglomeration of inorganic particles. In recent years, the 3-dimensional porous ceramic framework has been more and more frequently used in rigid-flexible coupling composite electrolytes. To have a deep insight into the positive function of 3-dimensional porous ceramic framework, in this review, we firstly reveal the mechanism of the huge improvement in the ionic conductivity and thermostability of the composite electrolyte. Then, we summarize the frequently used preparation methods of the 3-dimensional porous ceramic framework reported recently. Finally, for the future perspective of rigid-flexible coupling composite electrolyte development, we propose two feasible improvement strategies. This review can thereby provide great significance of designing solid electrolytes with comprehensive performance for all solid-state lithium batteries with high energy density and superior safety.