Unraveling Microporosity in Hard Carbons: Insights Into Sustainable Sodium‐Ion Battery Materials

A comprehensive methodology is proposed for the quantitative analysis of microporosity in HC for SIBs anodes. SAXS coupled with the Ruland–Smarsly approach enables the detection of closed pores and accurate estimation of surface area and pore‐size distribution beyond BET limitations. Two representative materials, a petroleum‐based and a biowaste‐derived HC, were compared to correlate nanostructural features with electrochemical behavior. Complementary XRD, Raman spectroscopy, and SEM support the SAXS interpretation by revealing differences in crystallinity and morphology. The results show that sustainable biowaste‐derived carbons achieve performance comparable to commercial ones. This SAXS‐based framework provides a reproducible route to probe nanoscale disorder in carbon anodes and guides the rational design of efficient and low‐impact materials for next‐generation SIBs.