Vertically Integrated Silicon–Carbon Nanotube Architectures for High-Capacity and Robust Lithium-Ion Battery Anodes

Lithium-ion batteries (LIBs) are going through a metamorphosis, progressing toward energy sources and storage that span wearables to grid-based storage; they are now moving toward bionic and space applications too. The performance of LIBs is often hindered by conventional anode materials, which suffer from restricted capacity, excessive volumetric expansion, dendrite formation, and an unstable solid electrolyte interphase (SEI) layer. This study introduces a breakthrough approach to fabricate vertically integrated silicon–carbon nanotube (VISiCNT) structures directly on copper foil. This architecture not only achieves exceptionally high capacities but also effectively accommodates volumetric expansion and mitigates material delamination. In addition, the high-quality growth of CNTs on copper foil is demonstrated at a rapid rate of 21 μm/min, suitable for roll-to-roll scale-up and large-scale manufacture. An unprecedented systematic investigation of various VISiCNT structural variants revealed that shorter CNTs (<5 μm) with a higher defect density (ID/IG ≥ 1) deliver some of the highest reversible capacities, exceeding 3500 mAh g–1, albeit at low loadings, while also exhibiting good cyclic stability. This research delineates a clear pathway for the development of VISiCNT anode structures that combine exceptionally high capacity with enhanced cyclic stability, thereby providing valuable insights for advancing next-generation energy storage solutions.