Revitalizing multifunctionality of Li-Al-O system enabling mother-powder-free sintering of garnet-type solid electrolytes

초록

Garnet-type Li7La3Zr2O12 (LLZO) is a promising electrolyte for solid-state lithium metal batteries owing to its high ionic conductivity and chemical stability. High-temperature sintering is essential for the fabrication of LLZO, which is often challenged by elemental loss (i.e. lithium volatilization) during sintering and thus causes product reliability issues. Here, we propose a simple and scalable coating strategy to enable LLZO to be sintered efficiently without sacrificial mother powder (or bed powder). We reveal that multifunctional Li-Al-O compounds coated on LLZO electrolytes effectively promote sintering process while mitigating lithium loss upon high-temperature sintering, rendering a highly dense (98.2 %) sintered pellet with high ionic conductivity (8.82 x 10-4 S cm-1) and low electronic conductivity (7.59 x 10-10 S cm-1). The fabricated pellets exhibit a significantly enhanced critical current density along with low charge-transfer resistance at the interface with lithium metals, attributable to the lithophilic Li-Al-O compound distributed across the grain boundaries. The practical viability of the strategy is further showcased by fabrication of high-quality pellets with large sizes up to 16 cm2 (after sintering). We expect that this simple yet effective strategy involving multifunctional agents to simultaneously design materials and their fabrication process expedites the technological advancement of sintering for solid-state oxide electrolytes towards commercialization.

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