柔性碳纳米纤维纸作为独立式高性能阳极，可实现出色的锂存储

摘要：孔隙构造是提升柔性锂离子电池（LIBs）碳纸（CP）阳极能量密度与功率密度的理想策略。然而，关于孔径变化对比容量影响的理论研究尚属罕见。本文，华南理工大学李海龙教授团队在《ACS Appl. Energy Mater》期刊发表名为“Flexible Carb

1成果简介

孔隙构造是提升柔性锂离子电池（LIBs）碳纸（CP）阳极能量密度与功率密度的理想策略。然而，关于孔径变化对比容量影响的理论研究尚属罕见。本文，华南理工大学李海龙教授团队在《ACS Appl. Energy Mater》期刊发表名为“Flexible Carbon Nanofiber Paper with a Rich Mesoporous Structure as a Free-Standing, High-Performance Anode for Excellent Lithium Storage”的论文，研究制备了富含介孔或微孔的柔性多孔碳负极，以揭示孔隙结构与锂存储容量的关系。

通过ZnCl₂活化制备的介孔碳纳米纤维纸（ECNFP）因缺陷作用具有更高的层间距和额外活性位点，从而显著提升容量。其比容量在0.1C循环100次后保持440 mAh·g–1，1C循环1000次后仍达132 mAh·g–1。密度泛函理论（DFT）进一步分析了缺陷双层石墨烯（BLG）层间距变化对作用力的影响。随着石墨烯层间距增大，锂离子对上层石墨烯的排斥作用消失，吸附能(Eads)与结合能(Ebin)同步降低，从而加速锂离子扩散。本研究为优化多孔碳基负极材料的孔径提供了理论指导，并为柔性负极材料的开发奠定了基础性框架。

2图文导读

方案一、Schematic Diagram of PCNFP Preparation。

图1. SEM of the PCNFP. (a) Schematic illustration of PCNFP electrodes with different grammages, (b, c) surface morphology of 40 g·m–2, and (d–g) cross-sectional morphology of 40, 60, 80, and 100 g·m–2.

图2. Material characterization of ECNFP, ICNFP, and CNFP, respectively. (a, c) N2 adsorption/desorption isotherms, (b, d) pore size distribution curves (inset: enlarged figure of the red area), (e, f) XRD pattern, (g) FT-IR spectrum, (h) XPS spectra, (i–k) high-resolution XPS spectra of C 1s, N 1s, and O 1s peak of the ECNFP sample, and (i) element content.

图3. SEM and TEM of ECNFP-4. (a, b) SEM images, (c) TEM images, and (d) HRTEM images, (e) SAED, (f–j) TEM-EDS elemental mapping, and (k–m) digital photograph of flexible ECNFP-4.

图4. (a) First three cycles of CV curves at a scan rate of 0.1 mV·s–1 for the ICNFP-3 and (b) ECNFP-4 electrode. (c–f) Cycling performance and GCD curves of the ICNFP and ECNFP at 0.1 C, respectively. (g) Cycling performance of CNFP, ICNFP-3, and ECNFP-4 at 0.1 C, respectively. (h) Rate performance of ECNFP-4. (i) Cycling performance of ECNFP-4 at 1 C.

图5. (a) CV curve at scan rates from 0.2 to 1 mV·s–1, (b) log(i)–log(v) plots, (c) capacitance control and diffusion control contributions at a scan rate of 1 mV·s–1, (d) capacitive contribution ratio at various scan rates of ECNFP-4. (e) Vme/VT and bR relationship for ECNFP-1, ECNFP-2, ECNFP-3, ECNFP-4, and ECNFP-5, respectively.

图6. Nyquist plots (a) before and (c) after 100 cycling of ECNFP, (b) and (d) ω–1/2–ZRe relationship curve of ECNFP. (e) Schematic illustration of ECNFP storage Li.

图8. Sign(λ2)ρ-colored VMD maps for the weak interaction between BLG and Li, isovalue = 0.01. The coloring method on the right represent the common interpretations of mapped function sign(λ2)ρ in the VMD map. (a) Defect-free BLG with a layer spacing of 0.335 nm. VC4 BLG with a layer spacing of (b) 0.335 nm, (c) 0.350 nm, and (d) 0.400 nm.

3小结

通过采用微/纳米纤维作为前驱体并引入ZnCl₂进行活化，设计了一种具有丰富介孔或微孔的柔性PCNFP作为锂离子电池的自支撑阳极。通过性能测试与表征评估了孔径尺寸与锂存储的关系。研究发现，锂存储性能并非仅由比表面积决定。关键在于：微孔的存在与容量提升无显著相关性，且仅当V++mi增加时才会促进锂不可逆容量。介孔结构通过增大层间距，显著提升了锂离子电池的比容量与倍率性能。ECNFP-4在0.1C倍率下经100次循环后仍保持440 mAh·g⁻¹的比容量，1C倍率下经1000次循环后仍保持132 mAh·g⁻¹的比容量，这归因于65.01%的Vme及若干缺陷位点。密度泛函理论计算表明，具有VC4缺陷结构的碳材料展现出最低的活化能。随着层间距增大，石墨烯层的锂离子吸附能（Eads）和键合能（Ebin）均降低，这显然是作用力减弱的结果。本研究为开发新一代锂离子电池的高性能碳负极材料提供了启示，并为不同孔径多孔碳材料的结构设计提供了关键指导。

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