Abstract

Hard carbon (HC) is one of the most promising anode materials in sodium‐ion batteries, and its sodium‐storage performance is closely related to its open/closed pore structures. However, modification of the inner pore structure of HC still remains a challenge. In this work, porous HCs are synthesized using pitch as the precursor, and the open and closed pores in HC are modified by NaF to obtain NaF@HC and polypropylene (PP)@NaF@HC, respectively. In the results, it is proved that NaF modification can construct closed pores in HC and improve Na+ transportation. Furthermore, NaF modification of the open pores effectively inhibits the electrolyte decomposition. Both NaF@HC and PP@NaF@HC exhibit excellent sodium‐storage performance, which delivers the reversible specific capacities of 310 and 323 mAh g−1, corresponding to the initial Coulombic efficiency (ICE) of 72.3% and 82.2%, respectively. Even after 200 cycles, their capacity retentions still maintain 99.5% and 92.8%. Nevertheless, NaF modification of the closed pores increases the sodium deposition barrier, leading to a severe capacity fading of the plateau capacity at a high current rate. In this study, the structural regulation of open and closed pores in HC can be guided, thereby improving its sodium‐storage kinetics.

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