Abstract
Double-perovskite-type La2/3-xLi3xTiO3 (LLT) crystals were grown by the travelling solvent floating zone (TSFZ) method. When the floating zone (FZ) crystal growth method was applied, the La2Ti2O7 phase was deposited as an inclusion in the initial growth region. Using the TSFZ crystal growth method, however, inclusion-free LLT crystals were obtained for a 10 mol% La2Ti2O7-poor composition solvent relative to the stoichiometric LLT crystals. The molten zone was initially unstable as a result of habit plane formation during the crystal growth; however, the molten zone was stably maintained for a long period of time by decreasing the feed rate compared with the growth rate. Hence, LLT crystals of approximately 5 mmφ and 37 mm in length were obtained. The anisotropic ionic conductivity of the crystals annealed in air was σ[110]/σ[001] ≈ 3, with σ[110] = 1.64 × 10−3 S cm−1 and σ[001] = 5.26 × 10−4 S cm−1. LLT single crystals are candidates for high-performance solid-state electrolytes in all-solid-state Li ion batteries.
Highlights
Conventional Li ion batteries incorporating liquid electrolytes are widely used in electric and portable devices; these batteries are associated with various potential problems such as electrolyte leakage and fire
The travelling solvent floating zone (TSFZ) method was expected to be effective for LLT crystal growth as it can suppress deposition of La2Ti2O7 inclusions and decrease the growth temperature to reduce Li evaporation from the molten zone
LLT was confirmed to be an incongruent-melting compound and larger LLT single crystals were grown by the TSFZ method
Summary
Conventional Li ion batteries incorporating liquid electrolytes are widely used in electric and portable devices; these batteries are associated with various potential problems such as electrolyte leakage and fire. All-solid-state Li ion batteries with a solid electrolyte are highly safe, being non-flammable and having zero leakage. Allsolid-state Li ion batteries offer significant advantages over conventional batteries, such as thermal stability and large potential windows allowing the use of high-voltage cathode materials and/or metallic Li anodes [1 – 3]. All-solidstate Li ion batteries are promising as next-generation storage batteries. Inorganic solid electrolytes comprise sulfide and oxide solid electrolytes. Sulfide solid electrolytes are reported to possess high ionic conductivities (s) of 1022 S cm comparable to those
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