Innovative manufacturing of nanostructured solid state electrolyte using suspension plasma spray

Abstract

The conventional vacuum-based methods used to fabricate all-solid-state lithium-ion battery (ASSLIB) components are typically expensive, characterized by slow deposition rates and yield mostly amorphous coatings that demand postprocessing to enhance performance. This research explores the advanced fabrication of Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) solid electrolyte coatings using suspension plasma spray (SPS) for ASSLIBs. The LLZTO feedstock suspension was stabilised by identifying most suitable suspension parameters such as zeta potential, particle size, and pH values to obtain uniform flowability. Coatings with thicknesses ranging from 15 to 30 μm were developed by varying stand-off-distance (SOD) and torch surface speed. X-ray diffraction (XRD) reveals the retention of high amounts of 68 % of the cubic-LLZTO phase content in the coatings compared to the raw materials used for making the suspension. Coatings exhibit around 75 % of crystallinity and 7 % porosity, which is favourable for better phase stability at high operating temperatures and restrict the dendritic formation respectively. Moreover, the coatings retained around 4.5 wt% of Li content from an initial 5 wt% in the powder. Furthermore, SPS'ed. LLZTO coatings resulted in ion-conductivity of the order of 10⁻⁸ S cm⁻¹, which is five times the conductivity of the same material obtained by magnetron sputtering, hence, demonstrating the potential of SPS to fabricate ASSLIB components.