NANOSTRUCTURED LITHIUM CERAMIC AND POLYMER COMPOSITE ELECTROLYTES FOR ALL-SOLID-STATE LITHIUM BATTERIES

Abstract

Bulk solid electrolyte-enabled solid-state lithium batteries with high energy density and better safety features are proposed to revolutionize battery-operated electric vehicles and other defense appliances. However, poor contact, high interfacial resistance, and inhomogeneous metallic lithium growth are the severe concerns associated with inorganic solid electrolytes. In this context development of high conducting solid electrolyte with improved interface are utmost required. Amongst all the solid state electrolyte, Li based garnet (LLZO) are highly promising due to its high ionic conductivity and large electrochemical potential window. To improve the ionic conductivity of LLZO further, the hetrovalent doping at Zr-site and Al-doping at Li site was done for the optimization of Li concentration in LLZO. This, co-doping strategy is an effecting tool to tailor the Li concentration inside the garnet, and the stimulate the morphological dependent dielectric and transport properties of the LLZO framework. In order to realize high-performing and safer all-solid-state battery technology, dedicated efforts have been devoted in the recent past. Amongst all, the polymer composite-based solid electrolyte utilization in the Li battery system is appealing, where the in-organic filler is infiltrated in the polymeric matrix, acting as a quasi-solid electrolyte membrane. On the other hand, flexible, non-leaking, and nonflammable characteristics of solid polymer electrolytes make them promising options for solid-state lithium batteries. It is worthwhile mentioning that simply adding active inorganic filler into the polymer matrix does not contribute to high ionic conductivity. There is a high chance of aggregation of such microcrystalline inorganic particles into the polymeric matrix. By Kussy’s percolation theory, for dispersion of filler particles with continuous segregation into a polymer matrix, a critical volume Vc is essential. The required volume fraction may achieve by optimizing the particle size and the aspect ratio of filler particles. Thus, to obtain a continuous and segregated dispersion of filler particles into a polymer matrix, a strategy has to be developed to optimize the geometry of continuous filler particles with a definite aspect ratio. Further, the excess use of such ionic conducting additives reduces overall mechanical and thermal properties, which in turn results in the poor performance of lithium batteries.