Regulating microstructure in agar-derived N-doped hard carbon towards enhanced sodium ion storage

• Published in: Journal of energy storage 2025-01, Vol.106, p.114640, Article 114640
• Main Authors: Ji, Yuhan, Wang, Tong, Yao, Xu, Gao, Jingkui, Chu, Yanting, Sun, Jingwen, Dong, Haitao, Sha, Jingquan
• Format: Article
• Language: English
• Subjects: Agar; Hard carbon; Nitrogen doping; Sodium-ion battery
• ISSN: 2352-152X
• DOI: 10.1016/j.est.2024.114640

Hard carbon (HC) with larger interlayer spacing, lower operation potential and stable skeleton is a promising kind of anode materials for sodium-ion batteries (SIBs), where heteroatom doping and structural design have been proved to be effective strategies to improve its Na+ storage performance. Herein, biomass agar-derived N-doped porous carbon (NPC-Ts, T = 750, 900 and 1050 °C) were successfully fabricated by modulating carbonization temperature, where interlayer spacing, specifical surface area (SSA), micro/mesopore amount and N-doping levels and configurations (pyridinic N (N-6), pyrrolic N (N-5) and graphite N (N-Q)) were explored in detail. Among the NPC-900 shows the largest interlayer spacing (0.412 nm), SSA (3991 m2/g) and sum percentage of N-6 and N-5 (76.7 %). When applied as anode material for SIBs, NPC-900 exhibits the highly reversible capacity (430.9 mAh/g at 100 mA/g after 100 cycles) and excellent rate capability (162 mAh/g at 5000 mA/g) and outstanding cycle life (242.6 mAh/g at 1000 mA/g after 5000 cycles). More importantly, when coupled with Na3V2(PO4)3 (NVP) cathode, the Na+ full cell displays the highest practical energy density of 267 Wh/kg to date, to the best our knowledge, revealing its potential practical sodium storage applications. Due to the difference of the activation degree of KOH and the content of nitrogen configuration at different carbonization temperatures, NPC-900 as SIBs anode exhibits an ultrahigh reversible capacity of 430.9 mAh g at 100 mA/g after 100 cycles with an excellent capacity retention of 115.9 %, assisted by the largest interlayer spacing, SSA, pore volume and defects. [Display omitted] •Excessive etching effect of KOH can make macropore collapse and produce more micropores.•The more N-5 content of NPC-900 produced larger interlayer spacing.•An ultrahigh reversible capacity of 430.9 mAh/g at 100 mA/g after 100 cycles was achieved.•The highest energy density of 267 Wh/kg was obtained from Na+ full cell in recent reports.