Lithium mobility along conduction channels of ceramic LiTa2PO8
K. Kwatek, Wioleta Ślubowska, E. Kwiatkowska, J.L. Nowiński, Agnieszka Krawczyńska, Isabel Sobrados, V. Diez–Gómez, J. Sanz
Abstract
In the next generation of lithium-ion batteries, the liquid electrolyte is considered to be replaced by its solid counterpart. Recently, a novel Li-ion conductor based on metal oxides emerged – LiTa2PO8. Due to the high value of bulk conductivity of ca. 10−3 S∙cm−1, it is believed to be a potential candidate for application as a solid electrolyte in all-solid-state battery technology. In this work, we investigate LiTa2PO8 ceramics synthesized by a conventional solid-state reaction method with an excess of the lithium-containing substrate to compensate for the loss of Li+ during sintering. The properties of LiTa2PO8 ceramics were studied using X-ray diffractometry (XRD), 6Li and 31P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), thermogravimetry (TG), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), impedance spectroscopy (IS), DC potentiostatic polarization technique and density method. Referring to the experimental results, increasing of the Li+ content above the stoichiometric one lowers the total ionic conductivity. The reasons for the deterioration and correlations between microstructure, phase composition, and ionic conductivity are presented and discussed. The MAS NMR spectroscopy has been used to explain high bulk ionic conductivity of LiTa2PO8 ceramics. A maximum value of total ionic conductivity, 4.5 × 10−4 S∙cm−1, was obtained at room temperature for the sample without any excess of Li+ source.