Stress-induced volume expansion suppression in silicon films on carbon nanotubes grown on carbon fibers for ultrahigh-stability flexible lithium-ion battery anodes

Herein, a flexible, binder-free carbon-fiber cloth supported silicon@nitrogen-doped carbon nanotubes (Si@NCNT/CC) anode is developed using chemical-vapor-deposition (CVD) and radio-frequency plasma magnetron sputtering (RF-PMS) techniques. The three-dimensional conductive network skeleton of NCNT/CC meticulously designed by the CVD method not only facilitates the release of volumetric stress of Si during cycling but also improves the overall electronic conductivity of the composite anode. Combined with the single-atom Si deposition via RF-PMS technology, it enables the precise design of amorphous Si films that fit the dimensions of the NCNT skeleton. This design notably boosts lithium-ion diffusion and accelerates reaction kinetics, while simultaneously demonstrating superb mechanical flexibility. When employed as an anode in flexible lithium-ion batteries (FLIBs), it demonstrates a discharge capacity of 1166.1 mAh g⁻¹ at 0.5 A g⁻¹, retaining 82.4 % of its capacity after 200 cycles. Even at 5 A g⁻¹, it still achieves a discharge capacity of 338.1 mAh g⁻¹ and maintains 81 % capacity after 500 cycles. The full cells are assembled with Si@NCNT/CC as the anode, while the cathodes are made of LiNi_0.8Co_0.1Mn_0.1O₂ and LiFePO₄ coated on CC, respectively, both exhibiting excellent cycling and rate performance. Practical pouch cell tests confirm the anode's flexibility and stable electrochemical performance under mechanical deformation.