Boosting sodium-ion batteries performance by N-doped carbon spheres featuring porous and hollow structures

Carbon materials are considered among the most promosing candidates for sodium ion batteries because of their competitive performance. Nevertheless, they suffer from low initial coulombic efficiencies (ICEs) and limited electrochemical performance. Herein, nitrogen-doped hollow carbon spheres (NHCSs) with a distinct porous structure are developed by a template-assisted carbonization of dopamine, followed by a template removal procedure. This advanced structural design, coupled with the surface chemistry of carbonized polydopamine, leads to an impressive ICE of 89.18% and a reversible capacity stabilized at ∼700 mA h g^-1 at 50 mA g^-1 after 100 cycles. Compared to commercial hard carbon anodes, NHCSs demonstrate superior rate performance, delivering a capacity of ∼200 mA g h^-1 at 5 A g^-1 with minimal capacity fading of ∼0.057 mA h g^-1 per cycle over 1000 cycles. These findings highlight the potential of NHCSs as a high-performance anode material for sodium-ion batteries, offering both high efficiency and excellent cycling stability.