ADVANCED MATERIALS & PROCESSES | APRIL 2024 26 handling and storage of materials feedstocks by combining chemical modifications and gas-tight sealings of the ready-to-print feedstocks. The last option, and the less evident, is to store the feedstock and perform 3D printing under an inert atmosphere or a dry room with controlled humidity. Accelerated aging tests and environmental durability studies should become the norm to evaluate long-term performance and stability, even at the laboratory scale. Another limitation is the need for the printed battery components to be subjected to costly post-processing steps. As reported in our previous studies[7,16,19], electrodes printed by means of the filament extrusion, as with powder bed fusion, or vat photo- polymerization, still contain a high amount of polymer matrix that is necessary to ensure good printability, but regrettably is non-electrochemically active. Printed electrodes are therefore subjected to thermal post-processing steps (i.e., debinding and sintering), to allow polymer removal and improve the electrochemical performance[19,20]. During these steps, the electrodes shrink considerably, which often compromises the assembly of the complete battery. Despite these challenges, a handful of companies have emerged in this field: Sakúu, producing solid- state battery cells with custom form factors for electric vehicles and mass- market via binder jetting; Blackstone Resources AG, a company using screen printing method that affirms their technology will be 30% cheaper than traditional battery manufacturing and will be compatible with liquid- electrolyte and solid-state batteries; Photocentric, using resin-based vat photopolymerization, has developed polymer electrolytes and electrodes resins that would enable low-cost mass manufacture of lightweight batteries for the U.K. market; and Dynamic Battery Corp., a start-up using inkjet printing to manufacture microstructured electrodes with honeycomb pore networks that promise to enhance fast charging. While these commercial aspects of 3D batteries are encouraging, the complete battery architecture remains planar. With a view to achieve fully 3D intertwined electrodes structures, the development and optimization of multi-material 3D printing systems, allowing the precise deposition of multiple materials within a single printed layer, becomes crucial. Such multi- material options already exist[6] but are not necessarily adapted for composite materials, nor commercially accessible. In the context of battery manufacturing, multi-material printers would ultimately enable the manufacturing of complex battery structures with all different materials tailored to specific functions (e.g., positive electrode, negative electrode, solid electrolyte, current collectors, and even casing). CONCLUSIONS Additive manufacturing, thanks to its ability to build on-demand complex geometries and shape-conformable battery components with tailored properties, appears as a unique transformative technology to revolutionize battery manufacturing. While 3D printing offers significant potential, careful consideration related to the material feedstock’s composition, stability, and printability, printing parameter optimization, production speed, quality control, mechanical integrity, and electrochemical performance of the printed components, must be thoroughly examined. Ongoing research and development efforts require interdisciplinary scientists, with knowledge in mechanical engineering, materials science, chemistry, and electrochemistry, to focus on addressing these challenges to advance the reliability and scalability of 3D printed batteries for a wide range of applications. The journey toward a future powered by efficient and customizable batteries is well underway, with additive manufacturing leading the charge. ~AM&P For more information: Ana C. Martínez and Alexis Maurel, College of Engineering, The University of Texas at El Paso, 500 W. University Ave., El Paso, TX 79968, acmartinezm@utep.edu and amaurel@utep.edu. References 1. V. Egorov, et al., Adv. Mater., 32, p e2000556, 2020, dx.doi.org/10.1002/ adma.202000556. 2. A. Maurel, et al., IEEE Access, 9, p 140654–140666, 2021, dx.doi.org/ 10.1109/ACCESS.2021.3119533. Fig. 3 — Graphic outlines the current challenges that must be addressed in the field of 3D printing of batteries.
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