Dual-Mode Porous and Highly Graphitized 3D Nitrogen-Doped Carbon Network as an Advance Anode Material for Sodium-Ion Batteries

The practical application of hard carbons as the most appealing anode material for sodium-ion batteries is hampered by their poor cycling and rate performances, emanating from poor electrochemical stability, low electroconductivity, and sluggish Na+ transport. Designing a single remedial method for these challenges often involves complex and energy-intensive processes, contradicting the core concept of cost-effectiveness for practical energy storage technology. Herein, we employed trifunctional silica (SiO2): as colloidal silica to ice template micron-sized pores, as a hard template for nanopores, and as a catalyst for the graphitization of carbon for the synthesis of a highly graphitized, efficiently nitrogen-doped, high-surface-area, three-dimensional porous carbon network (3D PNC) with dual-mode porosity (nanopores and micron-sized pores). As an anode material, the obtained 3D PNC exhibits a reversible capacity of 262 mAh g–1 at a current density of 100 mA g–1, an ultrahigh rate capability of 173 mAh g–1 at 1 A g–1, and a stable cycling life of 1000 cycles at a high current density of 100 mA g–1 with almost 100% capacity retention. The galvanostatic intermittent titration technique (GITT) reveals facile sodium diffusion kinetics with an average diffusion coefficient of an order of ∼10–9 (cm2 s–1), which is fairly low compared to most reported HC anodes for SIBs. This work demonstrates how a merger of two or more synthesis methodologies can be employed for the advanced microstructure engineering of carbon materials, opening up new avenues for the rational design of anode materials in SIBs.