Designing Niobium Oxide Anodes for Flexible and Fast‐Charging Lithium‐Ion Batteries

Flexible lithium-ion batteries (LIBs) are critical for powering emerging technologies such as wearable electronics, biomedical devices, and soft robotics. These systems must maintain stable performance under mechanical deformation while enabling fast-charging capability. However, achieving both high areal capacity and structural durability remains a significant challenge. Increasing the electrode mass loading improves energy density, but it often results in mechanical brittleness and limited ionic transport-issues that are especially pronounced in conventional slurry-based fabrication methods, which typically rely on toxic solvents like N-methyl-2-pyrrolidone. In this work, a flexible anode is presented based on mixed-phase niobium oxide-a defect-engineered material known for its excellent rate performance and stability. The electrode is fabricated using a solvent-free dry process that incorporates carbon nanofibers and polytetrafluoroethylene to form a robust, fibrillated architecture. Moreover, a conductive polymer adhesive, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate, is introduced to enhance interfacial contact between the electrode film and various current collectors, eliminating the need for heat or pressure during assembly. This integrated design not only overcomes the limitations of rigid LIBs under mechanical deformation but also mitigates environmental concerns by avoiding the use of toxic solvents. Overall, the approach offers a promising pathway toward high-performance, readily manufacturable flexible LIBs suitable for practical applications.