Ultrafast Microwave-Assisted Resin Curing Forming a Dense Cross-Linked Network on Bamboo: Toward High-Performance Hard Carbon Anodes for Sodium-Ion Batteries

Resin curing coating is an effective approach to mitigate the intrinsic defects of lignocellulosic biomass-derived hard carbon, which facilitates its large-scale application in sodium-ion batteries due to their improved specific capacity, initial coulombic efficiency, and carbon yield. However, current traditional curing processes suffer from issues such as uneven cross-linking encapsulation and long curing cycles, significantly affecting the electrochemical performance of the derived carbon and production efficiency/cost. In this study, a phenolic resin solution impregnation combined with microwave-accelerated curing has been employed, and its curing process, along with the electrochemical performance of the derived carbon, was investigated. The results show that uniformly phenolic resin-coated bamboo could be achieved within 120 s. A dense cross-linked network not only leads to a high hard carbon yield and low specific surface area but also creates an abundant pseudographene-like structure with more closed pores. Under optimal crosslinking conditions, the obtained hard carbon sample shows a significantly enhanced reversible capacity (371.73 mAh g−1) and high initial coulombic efficiency of 84.54%, far exceeding the bamboo-derived hard carbon (229.23 mAh g−1, 74.90%) and the hard carbon sample prepared by traditional heating curing (304.31 mAh g−1, 80.63%). Additionally, the designed sample displays excellent structural stability, maintaining 80% of their capacity after 500 cycles at a high current density of 300 mA g−1. This fast and simple resin coating strategy shows great potential for the scalable synthesis of high-performance hard carbon anode materials.