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~...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.展开更多
Research on hard carbon(HC)anodes for sodium-ion storage has focused on sodium storage mechanisms in both the high-potential slope and low-potential plateau regions,with the latter being particularly critical for enha...Research on hard carbon(HC)anodes for sodium-ion storage has focused on sodium storage mechanisms in both the high-potential slope and low-potential plateau regions,with the latter being particularly critical for enhancing energy density.Herein,a novel approach that combines ion exchange with low-temperature pyrolysis is presented to develop a closed-pore structure within HC.Leveraging a hard-template design,this approach precisely controls pore distribution and morphology,leading to a significant increase in the proportion of closed pores.In-situ characterization,density functional theory(DFT)calculations,and multi-scale simulations are used to investigate the micropore filling by sodium ions and the formation of clusters within the closed-pore structure.The findings underscore the crucial role of these structural features in enhancing electrochemical performance and offer a quantitative framework for the design of advanced HC materials.The optimized HC demonstrates a high reversible capacity of 413 mAh g^(-1)at a current density of 0.1 A g^(-1),excellent rate capability,and exceptional stability over 10,000 cycles.This study offers valuable insights into sodium-ion storage mechanisms in closed-pore HC and lays the groundwork for developing efficient and durable sodium storage materials.展开更多
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).
文摘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supported by the National Natural Science Foundation of China(22269020,U23A20582,42167068)the Outstanding Youth Fund of Gansu Province(20JR5RA539)+1 种基金the Gansu Province Higher Education Industry Support Plan Project(2023CYZC-17)2024 Major Cultivation Project for University Research and Innovation Platforms(2024CXPT-10)。
文摘Research on hard carbon(HC)anodes for sodium-ion storage has focused on sodium storage mechanisms in both the high-potential slope and low-potential plateau regions,with the latter being particularly critical for enhancing energy density.Herein,a novel approach that combines ion exchange with low-temperature pyrolysis is presented to develop a closed-pore structure within HC.Leveraging a hard-template design,this approach precisely controls pore distribution and morphology,leading to a significant increase in the proportion of closed pores.In-situ characterization,density functional theory(DFT)calculations,and multi-scale simulations are used to investigate the micropore filling by sodium ions and the formation of clusters within the closed-pore structure.The findings underscore the crucial role of these structural features in enhancing electrochemical performance and offer a quantitative framework for the design of advanced HC materials.The optimized HC demonstrates a high reversible capacity of 413 mAh g^(-1)at a current density of 0.1 A g^(-1),excellent rate capability,and exceptional stability over 10,000 cycles.This study offers valuable insights into sodium-ion storage mechanisms in closed-pore HC and lays the groundwork for developing efficient and durable sodium storage materials.
