Vat Photopolymerization Additive Manufacturing of Shape-Conformable Copper-Based Current Collector for Lithium-Ion Battery

High-resolution additive manufacturing (AM) has the potential to revolutionize the fabrication of electronics¹, and particularly energy storage devices such as lithium-ion batteries^1-3. Relegated to two-dimensional (2D) sheets, commercial lithium-ion batteries consist of stacked leaflets, which are only manufactured in restricted geometries. By leveraging the geometric freedom of additive manufacturing technologies, colloquially known as 3D printing, and its most recent advancements, next-generation shape-conformable and structural 3D batteries can be co-designed together with the application, so that dead-volume and weight are minimized, while energy and power densities as well as safety are enhanced⁴. In this presentation, a brief overview of our recent works on 3D printing of lithium-ion battery current collector via vat photopolymerization and thermoplastic material extrusion will be presented⁵. A particular attention will be devoted to our latest work regarding the development and optimization of a printable copper-based composite resin that can be used as material feedstock for a classical vat photopolymerization 3D printer, offering a resolution ranging between 5 and 35 μm. With a view to prevent traditional light scattering due to the presence of solid particles within the photocurable resin, our team developed an innovative Cu-based resin made from a polymer matrix, a photoinitiator and soluble metallic precursors. After printing, the copper-based object is subjected to thermal post-processing (debinding and sintering steps) to obtain pure copper complex 3D lattices that can be employed as current collector in a classical lithium-ion battery. Impact of the thermal post-processing parameters on the copper microstructure will be discussed thoroughly. An electrophoretic deposition (EPD) process based on well-known work⁶, has been optimized to create electroactive coating corresponding to the negative electrode onto the afore-printed 3D copper substrate. First step consisted in submerging the 3D copper structure on an EPD bath containing the electroactive material (graphite), surfactant, binder, charging agent and conductive carbon. Then a voltage between 50-75 V was applied for up to 20 minutes. The resulting coatings containing the electroactive negative electrode material e.g. graphite, appear homogeneous with only few cracks. High magnification scanning electron microscopy images of the structures will be presented. This work, focused on the development of 3D complex copper structures by means of additive manufacturing, paves the way towards the development of next generation energy storage devices but it can also be expanded to other applications for electronics, sensors and circuits as well as catalyst for CO₂ reduction.<br/><br/><b>References</b><br/>1 MacDonald, E. <i>et al.</i> Multiprocess 3D printing for increasing component functionality. <i>Science</i> <b>353</b>, doi:10.1126/science.aaf2093 (2016).<br/>2 Maurel, A.<i> et al.</i> Toward High Resolution 3D Printing of Shape-Conformable Batteries via Vat Photopolymerization: Review and Perspective. <i>IEEE Access</i> <b>9</b>, 140654-140666, doi:10.1109/ACCESS.2021.3119533 (2021).<br/>3 Yee, D. W.<i> et al.</i> Hydrogel-Based Additive Manufacturing of Lithium Cobalt Oxide. <i>Advanced Materials Technologies</i>, doi:10.1002/admt.202000791.<br/>4 Maurel, A.<i> et al.</i> Considering lithium-ion battery 3D-printing via thermoplastic material extrusion and polymer powder bed fusion. <i>Additive Manufacturing</i>, 101651, doi:https://doi.org/10.1016/j.addma.2020.101651 (2020).<br/>5 Maurel, A.<i> et al.</i> Ag-Coated Cu/Polylactic Acid Composite Filament for Lithium and Sodium-Ion Battery Current Collector Three-Dimensional Printing via Thermoplastic Material Extrusion. <i>Frontiers in Energy Research</i> <b>9</b>, doi:10.3389/fenrg.2021.651041 (2021).<br/>6 Mazor, H. <i>et al. </i>Electrophoretic deposition of lithium iron phosphate cathode for thin-film 3D-microbatteries. <i>Journal of Power Sources</i> <b>198</b>, 264-272, doi:10.1016/j.jpowsour.2011.09.108 (2012).