Abstract
Superionic solid electrolytes are key to the development of advanced solid-state Li batteries. In recent years, various materials have been discovered, with ionic conductivities approaching or even exceeding those of carbonate-based liquid electrolytes used in high-performance Li-ion batteries. Among the different classes of inorganic solid electrolytes under study, lithium thiophosphates are one of the most promising due to their high Li-ion conductivity at room temperature and mechanical softness. Here, we report about the effect of synthesis parameters on the crystallization behavior and charge-transport properties of Li4PS4I. We show that thermally induced crystallization of Li4PS4I (P4/nmm), starting from the glassy phase 1.5Li2S–0.5P2S5–LiI, adversely affects the material’s conductivity. However, both conductivity and crystallization temperature can be significantly increased by applying pressure during the preparation.
Highlights
Superionic solid electrolytes are key to the development of advanced solid-state Li batteries
The reflections of LiI largely vanished upon increasing the temperature to 200 or 250 °C, while those of L i4PS4I increased in intensity and decreased in broadening
Structural changes upon annealing were probed by ex situ X-ray diffraction (XRD), while the conductivity was measured by electrochemical impedance spectroscopy (EIS)
Summary
Superionic solid electrolytes are key to the development of advanced solid-state Li batteries. We detail how the synthesis route, temperature and pressure affect both crystallization and conductivity. The Li4PS4I SE was prepared at temperatures from 175 to 250 °C using wet-chemical, solid-state and hot-press routes.
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