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<p>Asphalt represents an economical and high-carbon-yield starting material suitable for producing hard carbon (HC) anodes in sodium-ion batteries (SIBs). Nevertheless, a significant drawback of its direct pyrolysis is the formation of a densely packed graphitic architecture, which severely hinders the diffusion of Na<sup>+</sup> ions. To address this, we propose an air oxidation cross-linking pretreatment to regulate the microstructural evolution during carbonization. By precisely controlling oxidation duration, varying concentrations of oxygen-containing functional groups were incorporated. This approach effectively suppressed the ordered alignment of carbon layers, resulting in a highly disordered turbostratic structure. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the successful introduction of carboxyl groups (-COOH), with the 9-hour oxidized sample (OA-9) exhibiting the highest -COOH content. X-ray diffraction (XRD) and Raman spectroscopy revealed that the carbonized OA-9 product (HC-9) possesses an expanded interlayer spacing (d₀₀₂ = 3.78 Å) and an increased I<sub>D</sub>/I<sub>G</sub> ratio (1.95), indicating that -COOH incorporation inhibits graphitization and enhances structural disorder. Morphological studies further demonstrated a porous, short-range ordered architecture in the derived HC. Electrochemically, HC-9 delivers exceptional rate capability, attributable to abundant active sites from its high -COOH content, and outstanding cycling stability (99.20% capacity retention after 500 cycles at 1&#xa0;C). A full-cell with HC-9 anode and Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> cathode achieves 206.43 Wh kg<sup>− 1</sup> and maintains 94.94% capacity over 300 cycles at 2&#xa0;C. This work elucidates the microstructural regulation of asphalt-derived HC via air oxidation cross-linking, providing both experimental evidence and mechanistic insights for synthesizing low-cost, high-performance SIB anodes.</p>

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Tailoring closed pores and interlayer spacing by air oxidation cross-linking: high-performance hard carbon anodes for Sodium-Ion batteries

  • 期刊论文

  • 发表日期：

    2026年1月31日

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  • Hongming Dai,
  • Li Xiao,
  • Jianfeng Yang,
  • Pengcheng Liu,
  • Pan Tang,
  • Jing Li,
  • Sheqiang Niu

摘要

Asphalt represents an economical and high-carbon-yield starting material suitable for producing hard carbon (HC) anodes in sodium-ion batteries (SIBs). Nevertheless, a significant drawback of its direct pyrolysis is the formation of a densely packed graphitic architecture, which severely hinders the diffusion of Na+ ions. To address this, we propose an air oxidation cross-linking pretreatment to regulate the microstructural evolution during carbonization. By precisely controlling oxidation duration, varying concentrations of oxygen-containing functional groups were incorporated. This approach effectively suppressed the ordered alignment of carbon layers, resulting in a highly disordered turbostratic structure. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed the successful introduction of carboxyl groups (-COOH), with the 9-hour oxidized sample (OA-9) exhibiting the highest -COOH content. X-ray diffraction (XRD) and Raman spectroscopy revealed that the carbonized OA-9 product (HC-9) possesses an expanded interlayer spacing (d₀₀₂ = 3.78 Å) and an increased ID/IG ratio (1.95), indicating that -COOH incorporation inhibits graphitization and enhances structural disorder. Morphological studies further demonstrated a porous, short-range ordered architecture in the derived HC. Electrochemically, HC-9 delivers exceptional rate capability, attributable to abundant active sites from its high -COOH content, and outstanding cycling stability (99.20% capacity retention after 500 cycles at 1 C). A full-cell with HC-9 anode and Na3V2(PO4)3 cathode achieves 206.43 Wh kg− 1 and maintains 94.94% capacity over 300 cycles at 2 C. This work elucidates the microstructural regulation of asphalt-derived HC via air oxidation cross-linking, providing both experimental evidence and mechanistic insights for synthesizing low-cost, high-performance SIB anodes.