Ultrafast Synthesis of Hard Carbon Anodes for Sodium‐ion Batteries: An Intense‐Pulsed‐Light‐Assisted Approach to Photothermal Carbonization of Polymer/Carbon Nanotube Composite Films

Abstract The conventional carbonization process for synthesizing hard carbons (HCs) requires high‐temperature furnace operations exceeding 1000 °C, leading to excessive energy consumption and lengthy processing times, which necessitates the exploration of more efficient synthesis methods. This study demonstrates the rapid preparation of HC anodes using intense pulsed light (IPL)‐assisted photothermal carbonization without the prolonged and complex operations typical of traditional carbonization methods. A composite film of microcrystalline cellulose (MCC) and single‐walled carbon nanotubes (SWCNTs) is carbonized at high temperatures in less than 1 min. The SWCNTs efficiently absorbed light energy, enabling ultrafast heating and eliminating the need for prolonged, high‐energy furnace‐based processes. The IPL‐assisted HC anodes exhibited excellent electrochemical performance, with an initial desodiation capacity of 260.4 mAh g⁻¹_anode and 97.5% capacity retention after 200 cycles. These results are comparable to those achieved using traditional furnace‐based carbonization processes, such as carbonizing HC anodes at 1200 °C, validating the effectiveness of IPL‐assisted processes. Additionally, surface and structural analyses revealed the development of pseudo‐graphitic domains, crucial for enhanced sodium‐ion storage. This research highlights IPL‐assisted photothermal carbonization as a viable, time‐efficient, and energy‐saving alternative to conventional methods, offering a sustainable pathway for the large‐scale production of HC anodes for future sodium‐ion battery technologies.