Combined Spray‐Drying and Flame‐Based Synthesis of Aluminum‐Doped Lithium Lanthanum Zirconate (LLZO) Solid Electrolytes

ABSTRACT Al‐doped lithium lanthanum zirconate (Li 7 La 3 Zr 2 O 12 , LLZO) is a promising solid electrolyte material for all‐solid‐state lithium batteries due to its high ionic conductivity and thermal stability. Flame‐based synthesis is an effective method for synthesizing nanoscale LLZO particles. In the present study, we propose a combined spray‐drying and flame‐based synthesis (SD‐FS) process for producing cubic‐phase LLZO, using a rotating‐plane premixed stagnation flame (RPSF) apparatus with cost‐effective feedstocks (including nitrate salt, water, and ethanol), followed by sintering processes to obtain a high‐performance LLZO solid electrolyte. The combined SD‐FS mechanism and the effect of sintering methods on the ionic conductivity of final LLZO solid electrolytes are investigated. Experiments and mathematical models reveal that the fed droplets undergo the stages of solvent evaporation, spherical shell precipitation, precursor melting and evaporation, nucleation, and collision, ultimately forming nanoparticles. The nano‐sized morphology and the hot‐pressing sintering, which involves a high pressure (40 MPa) with heating (1473 K for 2 h), are proven beneficial to the ionic conductivity of the sintered electrolyte pellets. Al‐doped LLZO SSE pellets with an ionic conductivity of 4.7 × 10 ‒4 S·cm ‒1 are synthesized using ethanol‐blended nitrate aqueous solution as the precursor and employing the hot‐pressing method as the sintering process.