N-Doped Porous Nanosheets Based on the Facile Assembly Method of N-Rich/Programed Cross-Linkable Molecular Precursors and Fe³⁺ for High-Performance Sodium-Ion Anodes

Sodium-ion batteries (SIBs) are promising for energy storage due to abundant sodium resources and their inherent safety. The most promising hard carbon anode materials still suffer from low capacity and poor rate performance. Hence, there is an urgent need for advanced carbon-based anode materials with high capacity and superior rate capability. Herein, nitrogen-doped porous nanosheets (NPNs) with outstanding rate performance, high reversible capacity, and excellent cyclic stability were readily produced via a facile, eco-friendly, and scalable method. It was based on assembling of N-rich/programed cross-linkable molecular precursors of triangular topology and Fe³⁺ ions in an aqueous phase. The NPNs maintained a reversible capacity of 180 mA h/g at a current density of up to 10 A/g. After 1000 cycles, the reversible capacities of NPNs maintained a capacity of 223 mA h/g at 1 A/g and 155 mA h/g with a capacity retention of 84.2% at 1 A/g and 89.1% at 10 A/g. The thin nanosheets' morphology, hierarchical porosity, and N-doped content play a crucial role in enhancing the capacity and rate performance. Additionally, capacitive contributions correlate positively with Na⁺ diffusion coefficients. These results offer valuable insights for the design of high-performance anode materials for next-generation SIBs.