Coal tar pitches (CTPs) can be used to fabricate low-cost hard carbon anodes in sodium-ion batteries (SIBs) via pre-oxidation methods; however, an in-depth analysis of their synthesis processes is still scarce in literature.

Biomass-derived hard carbon materials are considered as the most promising anode materials for sodium-ion batteries (SIBs) due to their abundant sources, environmental friendliness, and excellent electrochemical performance. Although much research exists on the effect of pyrolysis temperature on the microstructure of hard carbon materials, there are few reports that focus on the development of pore structure during the pyrolysis process. In this study, corncob is used as the raw material to synthesize hard carbon at a pyrolysis temperature of 1000~1600 °C, and their interrelationationship between pyrolysis temperature, microstructure and sodium storage properties are systematically studied. With the pyrolysis temperature increasing from 1000 °C to 1400 °C, the number of graphite microcrystal layers increases, the long-range order degree rises, and the pore structure shows a larger size and wide distribution. The specific capacity, the initial coulomb efficiency, and the rate performance of hard carbon materials improve simultaneously. However, as the pyrolysis temperature rises further to 1600 °C, the graphite-like layer begins to curl, and the number of graphite microcrystal layers reduces. In return, the electrochemical performance of the hard carbon material decreases. This model of pyrolysis temperatures–microstructure–sodium storage properties will provide a theoretical basis for the research and application of biomass hard carbon materials in SIBs.

Crystal transformation of metal compound cathodes during charge/discharge processes in alkali metal‐ion batteries usually generates profound impact on structural stability and electrochemical performance, while the theme in anode materials, which always occurs and completes during the first redox cycle, is rarely explored probably due to the fast transformation dynamics. Herein, for the first time, a unique crystal transformation behavior with slow dynamics in anode of sodium‐ion batteries (SIBs) is reported, which further promotes electrochemical performance. Specifically, irreversible γ → β crystal transformation of In₂Se₃ is observed, induced by the persistent size degradation of In₂Se₃ particles during repeated sodiation/desodiation, supported by a series of ex situ characterizations, such as HRTEM, XRD, and XPS of γ‐In₂Se₃/reduced graphene oxide (γ‐In₂Se₃@rGO) nanocomposite. The hybrid electrode shows ultrahigh long‐term cycling stability (378 mA h g⁻¹ at 1.0 A g⁻¹ after 1000 cycles) and excellent rate capability (272 mA h g⁻¹ at 20.0 A g⁻¹). Full battery with Na₃V₂(PO₄)₃ cathode also manifests superior performance, promising β‐In₂Se₃ dominated electrode materials in high‐power and long‐life SIBs. The first‐principle calculations suggest the crystal transformation enhances electric conductivity of β‐In₂Se₃ and facilitates its accessibility to sodium. In combination with the synergistic effect between rGO matrix, substantially enhanced electrochemical performance is realized.