Metal coordination strategy to control the pore structure of hard carbon materials for high-performance sodium storage

Abstract

Hard carbon stands as one of the most promising anode materials for sodium-ion batteries (SIBs), where pore structure regulation is crucial for enhancing sodium storage performance. This study employed polyaniline (PANI) as a precursor and introduced zinc acetate (Zn(Ac) 2 ) for coordination modulation, and then high-temperature carbonization (1300℃) was performed to obtain Zn-modified PANI-derived hard carbon (Zn-HC). The key feature of this approach is that Zn 2+ first coordinates with the -NH-groups along the PANI chains, achieving uniform dispersion prior to carbonization. The coordinated metal regulates the local carbon structure and pore architecture of Zn-HC during carbonization process, promoting the formation of closed pores. Concurrently, the migration and eventual volatilization of zinc creates large vacancy defects within the carbon matrix, leading to oxygen defects. This process also facilitates increased graphitization under high-temperature conditions. Utilizing ex-situ XPS and ex-situ Raman characterization, the coordination regulation mechanism and the sodium storage processes occurring within distinct voltage ranges were elucidated in detail. The optimized Zn-HC anode delivers a high reversible specific capacity of 313.6 mAh g -1 at 0.05 A g -1 and maintains 190.3 mAh g -1 even at a high current density of 2 A g -1 . Furthermore, Zn-HC exhibits excellent rate capability and long-term cycling stability, retaining 75.1% of its capacity after 1000 cycles at 1 A g -1 . Distinct from traditional sacrificial template methods, this synthesis strategy not only boosts the reversible capacity of hard carbon but also streamlines experimental procedures, offering a promising pathway for the large-scale production of hard carbon materials with optimized microstructures.