3D Printed Porous LLZO Multi-Layer Scaffolds for Li-Garnet Solid-State Batteries

Garnet-based oxides (Li₇La₃Zr₂O₁₂, LLZO) are promising solid-state electrolyte materials to achieve higher energy density and improved safety for the next-generation solid-state batteries (SSBs) due to their high ion conductivity and chemical stability. To enhance the performance of garnet-based SSBs, a dense-porous design of microstructure has been introduced in recent years. The design consists of a dense layer as the separator and one or two porous layers as the host of anode or cathode active materials [1-3]. The porous structure mitigates volume changes in the anode by accommodating Li in the pores during Li deposition, while the dense layer prevents short circuiting and provides additional mechanical support. Such bi- or tri-layer scaffolds are usually fabricated using tape-casting, in which the porous and dense layers are prepared separately, followed by trimming and stacking into the desired architectures. As a result, this process is challenged by workflow inefficiency due to the multiple separated casting and stacking steps.<br/><br/>To improve the efficiency in fabricating the porous-dense scaffold, we introduce an alternative approach using digital light processing (DLP), a unique 3D printing technology capable of layer-by-layer printing of multiple components and complex architectures in a single print [4]. Using DLP, the entire multilayer structure in the desired dimension is created <i>all-at-once</i> on the same printing platform by alternating printing slurries that respectively form the dense and porous layers. We produce free-standing, sub-millimeter-thick Ta-doped (LLZTO) porous-dense layers and demonstrate that the porosity is tunable by adjusting the particle size and solid loading in the printing slurry. This strategy for controlling the porosity is distinct from current approaches such as adding pore formers or controlling heat treatment conditions. By tuning the porosity in each of the printed layers, we show that a graded porosity can be created across the scaffold. In the future, this DLP printing approach will provide more opportunities to produce various microstructures and chemistries of SSBs with more efficiency and sustainability.<br/><br/>[1] Hitz, Gregory T., Dennis W. McOwen, Lei Zhang, Zhaohui Ma, Zhezhen Fu, Yang Wen, Yunhui Gong et al. "High rate lithium cycling in a scalable trilayer Li garnet electrolyte architecture." Materials Today 22 (2019): 50-57.<br/>[2] Yi, Eongyu, Hao Shen, Stephen Heywood, Judith Alvarado, Dilworth Y. Parkinson, Guoying Chen, Stephen W. Sofie, and Marca M. Doeff. "All solid state batteries using rationally designed garnet electrolyte frameworks." <i>ACS Applied Energy Materials</i> 3, no. 1 (2020): 170-175.<br/>[3] Zhang, Huanyu, Faruk Okur, Claudia Cancellieri, Lars PH Jeurgens, Annapaola Parrilli, Dogan Tarik Karabay, Martin Nesvadba et al. "Bilayer Dense Porous Li7La3Zr2O12 Membranes for High Performance Li Garnet Solid State Batteries." <i>Advanced Science</i> 10, no. 8 (2023): 2205821.<br/>[4] Chaudhary, R., Fabbri, P., Leoni, E., Mazzanti, F., Akbari, R., & Antonini, C. (2022). Additive manufacturing by digital light processing: a review. <i>Progress in Additive Manufacturing</i>, 1-21.