Enhanced electrochemical performance of garnet Li7La3Zr2O12 electrolyte by efficient incorporation of LiCl

Abstract

Garnet-type Ta-doped Li₇La₃Zr₂O₁₂ (LLZO) lithium-ion-conducting ceramic electrolytes has become the promising and critical candidate for developing the high-energy-density all-solid-state lithium batteries, due to the satisfied Li⁺ conductivity, stability against metallic lithium anode, and the feasible preparation under ambient air. Here, to further increase the lithium-ion conductivity of LLZO comparable to that of the commercial organic liquid electrolytes, lithium chloride (LiCl) is effectively introduced to synthesize the garnet-type ceramic electrolytes with the nominal composition (Li_6.5La₃Zr_1.5Ta_0.5O₁₂)_1-x–(LiCl)_x (x = 0, 5mol%, 10mol%, 15mol%, 20mol%, and 25mol%) via high-temperature calcination process. The cubic structure with highly conductive performance is confirmed from X-ray diffraction measurement as well as Raman spectra analysis. Structural information is observed according to field emission scanning electron microscope equipped with energy dispersive spectrometer and density measurements. Among above investigated ceramic compositions, the prepared (Li_6.5La₃Zr_1.5Ta_0.5O₁₂)_0.85–(LiCl)_0.15 ceramic electrolyte sheet sintered at 1200 °C for 12h presents the room-temperature Li-ion conductivity of 1.22 × 10⁻³ S·cm⁻¹ by alternating current (AC) impedance analysis along with the corresponding activation energy of 0.262eV through Arrhenius equation calculation. The electronic conductivity measurements are also done by direct-current polarization to confirm the ionic nature for all investigated ceramics. Furthermore, the Li|(Li_6.5La₃Zr_1.5Ta_0.5O₁₂)_0.85–(LiCl)_0.15 |Li symmetric batteries can possess the small interfacial resistance of 92.3 Ω cm² and stably run for 1000 h at 0.1 mA cm⁻² without a short circuit at room temperature. The hybridized lithium-sulfur battery with (Li_6.5La₃Zr_1.5Ta_0.5O₁₂)_0.85–(LiCl)_0.15 electrolyte delivered excellent initial room-temperature discharge capacity of 1204mAh·g⁻¹ and 1152 mAh·g⁻¹ under the current density of 0.1C and 0.2C respectively, large coulombic efficiency, and great cycling stability. Moreover, the lithium-sulfur batteries also can show excellent cycling performances under different current densities and a good capacity recoverability. The above investigation results suggest that the low-melting-point LiCl incorporation in Li_6.5La₃Zr_1.5Ta_0.5O₁₂ electrolyte is an effective measurement to synthesize the cubic and dense Li-stuff garnet ceramic sheets for the high-performance rechargeable next-generation solid-state batteries.