Recycled niobium oxide nanochannels from spent lithium-ion batteries: Enhanced performance for supercapacitor applications

Lithium-ion batteries (LIBs) are essential for modern energy storage but pose significant environmental and safety challenges due to the increasing volume of spent batteries. This study explores the reutilization of niobium oxide nanochannels (NONCs), initially employed as LIB anodes, as electrodes for supercapacitors. NONC electrodes, fabricated via electrochemical anodization, underwent structural and crystallographic transformations during charge-discharge cycling. The key findings demonstrate that these transformations, including an amorphous-to-crystalline phase transition, significantly improved ion transport efficiency and enhanced specific capacitance from 6.30 mF cm−2 to 18.54 mF cm−2. Highly crystalline NONC structures exhibited superior stability, maintaining their morphology and active surface area, thereby optimizing charge storage mechanisms. In contrast, substantial structural changes resulted in decreased capacitive performance due to a reduction in surface area and an increase in diffusion-controlled contributions. The study underscores a sustainable strategy for reusing LIB materials, highlighting the potential of waste NONC electrodes for high-performance supercapacitor applications. By bridging the gap between recycling and advanced energy storage, this work supports the principles of a circular economy, offering a scalable solution to LIB waste management. These findings provide valuable insights into the relationship between material properties, structural integrity, and electrochemical performance, contributing to the development of sustainable energy technologies.