Synergistic regulation of closed pore architecture and interface engineering in hard carbon for high energy density sodium-ion batteries

Hard carbon with extended low-potential plateau capacity holds promise for commercial sodium-ion batteries (SIBs). However, the complicated microstructure of hard carbon poses significant challenges in rationally designing active sites to improve reversible Na-storage capacity without compromising initial Coulombic efficiency (ICE). Herein, hard carbons with elaborate closed pore structures and tunable pore entrances were successfully fabricated using waste polyolefins-derived activated carbon (PC) as the precursor. The regulation of porosity architecture was realized by adjusting the deposited carbon layer derived from the polypropylene (PP)-based light aromatic compounds. The optimal PP/PC-3 electrode exhibited an ultra-high reversible capacity of 393.5 mAh g⁻¹ and an ICE of up to 88.5% in the ester-based electrolytes. While in the ether-based systems, the Na-storage capacity reached 477.3 mAh g⁻¹, with a capacity of 340.3 mAh g⁻¹ stemming from the low-voltage plateau region. The anode also demonstrates excellent low-temperature compatibility as well as exceptional cycling stability. Additionally, the assembled sodium-ion full battery achieved an energy density as high as 307.3 Wh kg⁻¹, suggesting its prospective application in high-energy-density SIBs. Furthermore, the differences in the Li/Na/K ion storage process within closed pores were elucidated, providing a deep insight into the structure engineering of carbon anode for advanced energy storage devices.