Catalyst‐Assisted Chemical Vapor Deposition Engineering of Hard Carbon with Abundant Closed Pores for High‐Performance Sodium‐Ion Batteries

Abstract Hard carbon is recognized as a promising anode material for sodium‐ion batteries due to its low voltage plateau and abundant availability. However, designing advanced hard carbon anodes that exhibit both high specific capacity and high initial Coulombic efficiency (ICE) remains a substantial challenge. This study introduces a catalyst‐assisted chemical vapor deposition (CA‐CVD) method utilizing CH ₄ as the gas precursor and porous carbon as the substrate to prepare hard carbon with controllable graphite domains and rich closed pores. The optimized Fe catalyst can reduce the decomposition energy barrier of CH ₄ , thereby enhancing the decomposition efficiency. Besides, it can promote microstructure rearrangement of pyrolytic carbon, which extends the graphite domains and minimizes surface defects. This level of precise control allows the synthesized hard carbon to achieve a high reversible specific capacity of 457 mAh g ⁻¹ and an impressive ICE of 90.6%. Furthermore, pairing such hard carbon anode with an O3‐NaFe _1/3 Ni _1/3 Mn _1/3 O ₂ cathode, the assembled pouch cell maintains a specific capacity of over 400 mAh g ⁻¹ . This work paves the way for future advancements in the synthesis and application of hard carbon anodes, contributing significantly to the development of high‐energy‐density sodium‐ion batteries.