Hard carbon with abundant closed-pore structures holds significant promise as an anode material for sodium-ion batteries. In this work, a one-step process was pioneered to produce porous carbon with abundant open-pore structures from walnut shells. Subsequently, small aromatic compounds derived from the pyrolysis of polystyrene were deposited into the pores of the porous carbon, forming hard carbon material with abundant closed-pore structures. The resulting hard carbon anode (WS-PS-1200) demonstrated a high capacity of 385 mAh g−1 at 50 mA g−1, with a corresponding plateau capacity of 225 mAh g−1. It also exhibited an impressive initial Coulombic efficiency (ICE) of 88 % and excellent rate performance, compared to an ICE of only 57.5 % in the anode obtained by direct carbonization. By utilizing 3D time-of-flight secondary-ion mass spectrometry (3D TOF-SIMS) and depth-profiling X-ray photoelectron spectroscopies (XPS) characterization methods to analyze the solid electrolyte interface (SEI), the results indicate that reducing the open-pore structure can minimize the decomposition of the electrolyte, leading to an SEI composition that tends towards inorganic phases. To verify the practical applicability of WS-PS-1200, it was assembled into a full cell with Na3V2(PO4)3, achieving a capacity of 305 mAh g−1 (0.03 A g−1) and excellent rate performance. Moreover, the assembled all-carbon sodium-ion hybrid capacitor exhibits an energy density of 101 Wh kg−1. This study not only introduces a new strategy for preparing hard carbon with closed pores but also successfully converts waste polystyrene and walnut shells into high-value materials, offering an innovative method for synthesizing hybrid capacitor electrode materials.

中文翻译：

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钠离子电池用闭孔硬碳的创新合成与储钠增强


具有丰富闭孔结构的硬碳作为钠离子电池的负极材料具有重要的前景。在这项工作中，开创了一种一步法工艺，从核桃壳中生产具有丰富开孔结构的多孔碳。随后，聚苯乙烯热解衍生的小芳香族化合物沉积到多孔碳的孔中，形成具有丰富闭孔结构的硬碳材料。所得硬碳阳极 （WS-PS-1200） 在 50 mA g-1 时表现出 385 mAh g-1 的高容量，相应的平台容量为 225 mAh g-1。它还表现出令人印象深刻的 88% 的初始库仑效率 （ICE） 和出色的倍率性能，而通过直接碳化获得的阳极 ICE 仅为 57.5%。通过利用 3D 飞行时间二次离子质谱 （3D TOF-SIMS） 和深度剖析 X 射线光电子能谱 （XPS） 表征方法分析固体电解质界面 （SEI），结果表明，减少开孔结构可以最大限度地减少电解质的分解，导致 SEI 组成趋向于无机相。为了验证 WS-PS-1200 的实际适用性，它用 Na3V2（PO4）3 组装成一个完整的电池，实现了 305 mAh g-1 （0.03 A g-1） 的容量和出色的倍率性能。此外，组装的全碳钠离子混合电容器的能量密度为 101 Wh kg-1。本研究不仅介绍了一种制备封闭孔隙硬碳的新策略，而且成功地将废弃的聚苯乙烯和核桃壳转化为高价值材料，为合成混合电容器电极材料提供了一种创新方法。