辐照交联制备低分子量聚丙烯腈纤维锂硫电池正极材料及其储硫机理 高等学校化学学报    2022, 43 (3): 20210632-.   DOI:10.7503/cjcu20210632

Fig.9 Cycling performance(A) and electrochemical impedance spectra(B) of SPAN electrodes with different cross?linking degrees

正文中引用本图/表的段落

探究了不同交联度下SPAN复合材料作正极时电池的性能. 图9（A）示出了3种电极材料组装成电池后100圈下的循环特性.在0.2C倍率下， 由SPAN组装的电池的首次放电比容量约为1197 mA?h/g， 循环100圈后的容量保持率约为89%（从第二圈开始计算）， 而由SPAN-IR200和SPAN-IR300组装的电池在0.2C倍率下首次放电比容量分别为1059 mA?h/g和994 mA?h/g， 因辐照导致SPAN-IR200及SPAN-IR300的载硫量下降， 所以相较于SPAN， 其比容量受载硫量影响略有降低， 但硫利用率相差不大， 循环100圈后两电池的容量保持率分别提升至93%和98%. SPAN-IR200及SPAN-IR300电池的容量衰减趋势表现在循环曲线的平缓走势上， 两电池的容量衰减程度均小于SPAN， 说明前期交联有利于提高SPAN电极的循环稳定性. 对比3种电极材料的阻抗谱图［图9（B）］可见， 交联度最高的SPAN-IR300电极材料在高频区域的半圆直径最小， 表明其电荷转移电阻最小. 相比之下SPAN-IR200和SPAN的电阻逐渐增大. 由此可知交联度增加可有效减少电极极化， 对材料电化学循环稳定性起促进作用， 与循环性能曲线分析一致. 交联使PAN硫化过程中环化加剧， 形成更加规整有利于电子传导的结构， 虽然阻碍了硫的接入， 但使SPAN主链框架的电化学稳定性提升.

本文的其它图/表

• Fig.1  SEM image of the profiled PAN fiberInset: cross?sectional image.
• Fig.2  Morphology(A) and gel fraction diagram(B) Irradiation under different irradiation doses
• Fig.3  Polarizing optical microscopy images of profiled PAN fibers at different temperatures and under different irradiation dosesIrradiation dose/kGy: (A₁—A₅) 0; (B₁—B₄) 200; (C₁—C₄) 250; (D₁—D₄) 300; (E₁—E₄) 350.Temperature/℃: (A₁—E₁) r.t.; (A₂—E₂) 220; (A₃—E₃) 250; (A₄—E₄) 270; (A₅) 290.
• Table 1  Elemental analysis of profiled PAN fibers with different cross-linking degrees
• Fig.4  FTIR(A) and ¹³C NMR(B) spectra of PAN fibers with different cross?linking degreesa. PAN； b. PAN?IR200； c. PAN?IR300.
• Scheme 1  Possible reaction sites and structures during PAN cross?linking
• Table 2  Elemental analysis of SPAN with different cross-linking degrees
• Fig.5  SEM images(A₁—C₁) and corresponding elemental mappings(A₂—A₄, B₂—B₄, C₂—C₄) of SPAN with different cross?linking degrees
• Fig.6  XRD patterns of SPAN with different cross?linking degrees
• Fig.7  FTIR(A) and Raman(B) spectra of SPAN with different cross?linking degrees
• Fig.8  S_2p (A—C) and N_1s (D—F) XPS spectra of SPAN with different cross?linking degrees(A, D) SPAN?IR300; (B, E) SPAN?IR200; (C, F) SPAN.
• Scheme 2  Structure diagram of cross?linking and vulcanization reaction
• Fig.10  Rate performance curves(A) and charge?discharge curves in the second cycle(B) of the SPAN cathode with different cross?linking degrees
• Fig.11  CV curves of the SPAN cathode with different cross?linking degrees(A) SPAN; (B) SPAN?IR200; (C) SPAN?IR300.