Research on the Controlled Synthesis of Phenolic Resin‐Based Carbon Microspheres and Their Sodium Storage Behavior

Abstract Phenolic resin is considered a promising precursor for advanced hard carbon anodes in sodium‐ion batteries (NIBs) due to its ease of design, structural stability, and high residual carbon yield. However, the practical application of hard carbon is affected by its closed‐pore content and structure. Here, we achieve fine control over the cross‐linking structure of phenolic resin precursors by adjusting the catalyst content in the system, followed by high‐temperature carbonization to produce phenolic resin‐based carbon microspheres with small sizes (2–4 µm), monodispersity, and a narrow spherical diameter distribution. Based on this, we deeply explore the intrinsic relationship between the microstructure of these resin‐based carbon microspheres and their sodium storage performance in NIBs. This strategy can provide a feasible molecular cross‐linking engineering approach for the development of closed pores in phenolic resin‐based hard carbon to tune electrochemical properties such as the plateau region capacity.