Scalable Self-Assembly of Composite Nanofibers into High-Energy-Density Li-Ion Battery Electrodes.

The application of nanosized active particles in Li-ion batteries has been the subject of intense investigation, yielding mixed results in terms of overall benefits. While nanoparticles have shown promise in improving rate performance and reducing issues related to cracking, they have also faced criticism due to side reactions, low packing density, and consequent subpar volumetric battery performance. Interesting processes such as self-assembly have been proposed to increase packing density, but these tend to be incompatible with scalable processes such as roll-to-roll coating, which are essential to manufacture electrodes at scale. Addressing these challenges, this research demonstrates the long-range self-assembly of carbon-decorated V 2 O 5 nanofiber cathodes as a model system. These nanorods are closely packed into thick electrode films, exhibiting a high volumetric capacity of 205 mA h cm -3 at 0.2 C. This surpasses the volumetric capacity of unaligned V 2 O 5 nanofiber electrodes (82 mA h cm -3 ) under the same cycling conditions. We also demonstrate that these energy-dense electrodes retain an excellent capacity of up to 190.4 mA h cm -3 (<2% loss) over 500 cycles without needing binders. Finally, we demonstrate that the proposed self-assembly process is compatible with roll-to-roll coating. This work contributes to the development of energy-dense coatings for next-generation battery electrodes with high volumetric energy density.