摘要
As a promising candidate for solid-state electrolytes, garnet solid electrolyte Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) with high ionic conductivity and excellent electrochemical performance has attracted more and more attention due to the increasingly urgent safety and energy density concerns of lithium-ion batteries. However, there is still a big challenge to prepare the high-quality LLZTO ceramic electrolyte with fine grains, high ion conductivity and high density because of the serious Li-loss, porous microstructure and the abnormal grain growth during the long-time high-temperature conventional sintering process. Herein, Fe 2 O 3 as a sintering aid has been introduced to prepare the high-quality LLZTO ceramic electrolyte by low temperature sintering, which is an effective strategy to obtain high density and inhibit Li-loss. The densification behavior, phase composition, microstructure and electrochemical performance have been systematically investigated for LLZTO ceramics with different amount of Fe 2 O 3 additive. High density (ρ r = 94.7 %), high ionic conductivity of 6.82 × 10 −4 S cm −1 and low electronic conductivity of 9.09 × 10 −9 S cm −1 at 25 °C are achieved for the LLZTO-5 mol% Fe 2 O 3 ceramics sintered at the lower temperature of 1075 °C for 3 h. Meantime, the garnet electrolyte exhibits excellent electrochemical performance. Li/LLZTO-5 mol% Fe 2 O 3 /Li symmetric cell exhibits good stability after cycling more than 800 h at a current density of 0.1 mA·cm −2 . The LiFePO 4 /LLZTO-5 mol% Fe 2 O 3 /Li full cell delivers an initial discharge capacity of 115.2 mAh·g⁻¹ and retains a good capacity of 88 % after 80 charge-discharge cycles at 0.2 C. This suggests that the introduction of Fe 2 O 3 as a sintering aid provides a promising strategy of energy-saving, low-cost and high-efficient to achieve high-quality LLZTO-based solid electrolytes for advanced energy storage systems.
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