Experimental and Theoretical Analysis of Li-Stuffed Garnet-Type Electrolytes

Abstract

Rechargeable lithium-ion batteries (LIBs) are one of the dominant technologies for electrochemical energy storage. They are widely used in portable electronics, electrical vehicles, and large-scale energy storage systems. Current LIBs use organic polymer based electrolytes and they have several problems such as dendrite formation, flammability and leakage.1 Therefore, there is much attention on developing a solid-state Li-ion electrolyte that is thermally and chemically stable. Among the various inorganic solid Li-ion conducting electrolytes, garnet structured compounds have shown great promise as potential electrolytes for all-solid-state lithium batteries due to their high ionic conductivities (10-4 S/cm), compatibility with Li metal anode, and wide electrochemical window (~ 6V vs Li/Li+).2 The present study reports a comparison of the experimental and theoretical data of garnet type Li-ion solid electrolytes. The solid electrolytes, Li6.5La2.9A0.1Ta0.6Zr1.4O12 (A = Ca, Sr, Ba) were prepared by conventional solid state sintering and spark plasma sintering method. The formation of the ‘‘single-phase’’ garnet-type structure was analysed by powder X-ray diffraction (PXRD). Li-ion conductivity was determined using electrochemical impedance spectroscopy (EIS) and all the members have exhibited ionic conductivity in the order of 104 S/cm at 25 °C. Interfacial resistance of the garnet samples and Li metal was measured using EIS and the interfacial stability of the same was confirmed by DC galvanostatic cycling experiments. Li-ion conductivity and activation energy of the prepared compounds were also calculated using a statistical mechanical approach and the estimated values are in good agreement with the experimental values.