As demand for scalable, low-cost energy storage surges, sodium-ion batteries (SIBs) are emerging as a front-runner for grid-scale applications. Yet their energy density still lags behind that of lithium-ion systems. Now, a team led by Prof. Hongshuai Hou at Central South University has published a landmark review revealing how “closed pores” in hard carbon anodes could be the key to unlocking high-energy, high-efficiency SIBs.
Why Closed Pores Matter
Hard carbon (HC) is the anode material of choice for SIBs due to its low cost and stable cycling. However, its amorphous microstructure has long puzzled researchers. While traditional models focused on open pores and graphitic interlayers, they failed to explain the low-voltage plateau capacity—a critical region for boosting energy density.
This review introduces a unified framework centered on closed pores: nanoscale voids that are inaccessible to gas adsorption but accessible to sodium ions. These pores enable the formation of quasi-metallic sodium clusters, dramatically increasing reversible capacity (up to 500 mAh g -1 ) and initial Coulombic efficiency (ICE > 90%).
Key Insights and Innovations
Examples include:
Future Outlook
The authors propose a molecular-level design paradigm for hard carbon, integrating:
They emphasize that closed pores are not just structural features—they are electrochemical active sites. Mastering their design could bridge the energy density gap between sodium- and lithium-ion technologies.
Conclusion
This comprehensive review redefines how we understand and engineer hard carbon anodes. By shifting the focus from open porosity to closed-pore architecture, it offers a clear roadmap for designing next-generation SIBs with higher energy, longer life, and lower cost.
Stay tuned for more breakthroughs from Prof. Hongshuai Hou and the team at Central South University as they continue to push the boundaries of sodium-ion battery science.
Nano-Micro Letters
Experimental study
Comprehensive Understanding of Closed Pores in Hard Carbon Anode for High‑Energy Sodium‑Ion Batteries
7-Jul-2025