Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries due to the natural abundance and low cost of sodium resources. However, the relatively large ionic radius of sodium ions hinders their intercalation into conventional graphite anodes, necessitating the development of advanced anode materials. In this study, high-performance hard carbon materials were synthesized from ZIF-8 precursors through controlled carbonization at various temperatures. Among the samples, ZIF-800, which is carbonized at 800 °C, exhibited the highest reversible capacity (156.63 mAh/g after 100 cycles at 100 mA/g) and excellent cycling stability. This superior performance is attributed to the optimized combination of high specific surface area (700.35 m2/ g), well-developed pore structure, and enhanced defect concentration, as indicated by a low IG/ ID ratio. The capacitive-dominant charge storage behavior further contributes to the improved electrochemical characteristics. These findings highlight the critical role of tuning carbonization temperature to achieve a balanced microstructure, offering valuable insights for the rational design of high-performance hard carbon anodes for SIBs.

Structural effect of ZIF-8 derived carbon on sodium-ion storage behavior
    Abstract
    1 Introduction
    2 Results and discussion
        2.1 Physical properties of ZIF-8 and ZIF-8 derived carbon
        2.2 Electrochemical performances of ZIF-8 derived carbon
        2.3 Ex situ Raman spectroscopy analysis of ZIF-8 derived carbon
    3 Conclusion
    4 Experimental section
        4.1 Materials synthesis
        4.2 Materials characterization
    Acknowledgements 
    References

• Kitak Kim(Department of Materials Science and Engineering, Myongji University, Gyeonggi‑Do 17058, Republic of Korea)
• Jongyeop Choi(Department of Materials Science and Engineering, Myongji University, Gyeonggi‑Do 17058, Republic of Korea)
• Seunghoon Nam(Department of Materials Science and Engineering, Myongji University, Gyeonggi‑Do 17058, Republic of Korea) Corresponding author