摘要
Hard carbon is widely regarded as one of the most promising anode materials for sodium-ion batteries(SIBs),yet achieving high energy density requires a significant enhancement of the low-voltage plateau capacity near~0.1 V(vs.Na^(+)/Na).Although closed-pore structures dominate plateau storage,their formation mechanisms remain elusive.We present a synergistic strategy combining CO_(2) etching with high-temperature carbonization to systematically elucidate the evolution of closed pores and their influence on sodium storage behavior.CO_(2) etching generates open pores that reorganize into closed pores during secondary treatment.Crucially,precursor selection dictates closed-pore density,with N-rich chitosan-derived hard carbon developing denser closed-pore architecture than exclusively O-doped precursors.The optimized hard carbon anode delivers a high reversible capacity of 388.8 mAh·g^(−1) at 0.05 A·g^(−1),with excellent cycling stability(83.8%capacity retention after 800 cycles at 0.5 A·g^(−1)).In-situ and ex-situ analyses demonstrate that Na+ions reversibly fill the engineered closed pores,accounting for over 200 mAh·g^(−1)(approximately 57%of the total reversible capacity)via a plateau-dominated storage.Consequently,full cells assembled with this optimized hard carbon anode achieve an energy density of 165.2 Wh·kg^(−1).This work offers new mechanistic insights into pore evolution and provides a practical route for tailoring high-performance hard carbon anodes for next-generation SIBs.
基金
the financial supports from the National Natural Science Foundation of China(No.22179123)
the Taishan Scholar Program of Shandong Province,China(No.tsqn202211048)
the Major Basic Research Projects of Shandong Natural Science Foundation(No.ZR2024ZD37).
