Pore modulation in coal-based hard carbon for sodium-ion batteries

Designing the closed-pore structure of hard carbon to improve its low-voltage sodium storage capacity is both significant and challenging for the development of high-performance sodium-ion batteries. We utilized a briquetting process combined with a templating method to modulate the pore architecture. By adjusting the briquette pressure, we can regulate the degree of magnesium ion etching and the degree of cross-linking in the precursor, thereby augmenting the closed-pore content of hard carbon and boosting its sodium-storage performance at low potential. During the pre-carbonization stage, magnesium ions etched the surrounding carbon layers, generating large open pores. Experimental results demonstrated that at 3 MPa, the HC-3 anode exhibited a reversible capacity of 366 mA h g −1 at 20 mA g −1 , with a capacity of 224 mA h g −1 below 0.1 V. This study provides valuable insights into optimizing the pore structure of coal-based hard carbon anodes and enhancing low-potential sodium storage.