Recycling spent masks to fabricate flexible hard carbon anode toward advanced sodium energy storage

The massive discard of spent masks during the COVID-19 pandemic imposes great environmental anxiety to the human society, which calls for a reliable and sustainable outlet to mitigate this issue. In this work, we demonstrate a green design strategy of recycling the spent masks to fabricate hard carbon fabrics toward high-efficient sodium energy storage. After a simple carbonization treatment, flexible hard carbon fabrics composed of interwoven microtubular fibers are obtained. When serving as binder-free anodes of sodium-ion batteries, a large Na-ion storage capacity of 280 mAh g⁻¹ is achieved for the optimized sample. More impressively, the flexible anode exhibits an initial coulombic efficiency of as high as 86% and excellent rate/cycling performance. The real-life practice of the flexible hard carbon is realized in the full-cells. The present study affords an enlightening approach for the recycling fabrication of high value-added hard carbon materials from the spent masks for advanced sodium energy storage.