Laser‐Welded Cellulose‐Carbon Nanotube Nanocomposites as a 3D Scaffold of Si Anodes for High‐Performance Lithium‐Ion Batteries

Abstract To satisfy the demand for high‐performance lithium‐ion batteries (LIBs), silicon (Si) based anodes have attracted attention due to their high theoretical capacity, and there is increasing interest in anode architectures employing conventional micro‐sized Si without sacrificing the electrochemical performance. Herein, a highly conductive 3D nanocomposite scaffold containing entangled networks of cellulose and SWCNTs (C‐CNT) is fabricated via an eco‐friendly method for use as an Si anode. Additionally, localized rapid heating of the Si/C‐CNT film on a Cu current‐collector is newly demonstrated by IR laser‐irradiation in ambient air. This treatment leads to both nanowelding of the SWCNTs onto the Si anode and pyrolysis of the cellulose, thereby increasing the Si loading from 50 to 89.5 wt.%, decreasing the sheet resistance from 9.6 to 7.2 Ω sq −1 , and increasing the specific surface area from 16.9 to 77.1 m 2 g −1 . Structural analysis confirms the generation of covalent Si─C and Si─O─C bonds on the Si surface via photothermal conversion. In the LIB application, the laser‐treated Si/C‐CNT exhibits an enhanced electrochemical performance relative to the untreated anode, with a 37% increase in capacity retention at 3.0C and a more than two‐fold increase in capacity retention after 100 cycles at 1.5 A g −1 .