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

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.