Point-of-use upcycling of 3D printing waste for developing 3D-printed Zn–I2 batteries

Abstract

Three-dimensional (3D) printing technology is an effective method to fabricate and develop customized and high surface area electrodes for energy storage devices, but it also produces plastic waste and material scraps during printing and optimization. To address this issue, a more sustainable approach beyond traditional chemical recycling or landfilling is essential. In this work, we upcycle 3D printing filament scrap, specifically carbon nanofiber (CNF)/polylactic acid (PLA) composites, to develop 3D-printed rechargeable Zn–I₂ batteries (3D-ZIBs), transforming scrap into functional energy storage materials. The mechanically upcycled CNF/PLA 3D printing filaments exhibit strong chemical stability, favorable electrochemical properties, and a porous structure, enhancing iodine–iodide redox conversion as a cathode host. They also support parallel-type zinc electrodeposition, enabling long-term zinc plating/stripping with exceptional stability and corrosion resistance. The upcycled CNF/PLA-based 3D ZIB exhibits capacity (195 mA h g⁻¹) comparable to the fresh CNF/PLA electrode (197.7 mA h g⁻¹) and maintains a robust capacity retention of 78.32% after 5000 cycles. Custom designs, including micro lattice-type, brick-shaped, and ring-shaped 3D-ZIBs with gel-based catholyte/electrolyte architecture, offer functionality tailored for wearable or space-constrained applications. This study demonstrates a sustainable approach to upcycling conducting filament scrap, addressing 3D printing plastic scrap, and promoting a circular economy.