Multiprocess 3D printing of sodium-ion batteries via vat photopolymerization and direct ink writing

Abstract In this work, the ability to print shape-conformable batteries with multi-process additive manufacturing is reported. Vat photopolymerization (VPP) 3D printing process is employed to manufacture gel polymer electrolytes (GPEs) for sodium-ion batteries (SIBs), while direct ink writing process is used to prepare positive electrodes. The sodium-ion chemistry has proven to be an adequate substitute to lithium-ion due to the availability of resources and their potential lower production cost and enhanced safety. Three-dimensional printing technologies have the potential to revolutionize the production of shape-conformable batteries with intricate geometries that have been demonstrated to increase the specific surface area of the electrode and ion diffusion, thus leading to improved power performances. This study shows the preparation of composite UV-photocurable resins with different polymer matrix-to-liquid electrolyte ratios, designed to act as GPEs once printed via VPP. The impact of the liquid electrolyte ratio within the GPEs is thoroughly examined through a variety of electrochemical techniques. The exposure time printing parameter is optimized to ensure adequate print accuracy of the GPE. Using the optimized resin composition as material feedstock, shape-conformable 3D printed GPE exhibiting an ionic conductivity of 3.3 × 10⁻³ S·cm⁻¹ at room temperature and a stability window up to 4.8 V vs. Na⁰/Na⁺ is obtained. In parallel, a composite ink loaded with Na_0.44MnO₂ and conductive additives is developed to 3D print via direct ink writing positive electrodes. After demonstrating the functionality of the independent 3D printed components in SIBs, the last part of this work is focused on combining the 3D printed Na_0.44MnO₂ electrode and the 3D printed GPE into the same battery cell to pave the way towards the manufacturing of a complete 3D printed battery thanks to different additive manufacturing processes.