铜卟啉金属有机框架材料用于高性能锂硫电池

利用卟啉配体与金属离子的配位特性,通过后修饰将铜离子与卟啉基金属有机框架材料(PCN-222)配位,得到铜卟啉金属有机框架材料(PCN-222-Cu),并首次用于锂硫电池。借助紫外可见光谱(UV-Vis)、粉末X射线衍射(PXRD)、N_2吸附-脱附测试、扫描电子显微镜(SEM)、循环伏安(CV)和恒电流充放电测试等表征手段对材料的晶相结构、形貌和电化学性能进行了系统的研究。其中UV-Vis结果表明,Cu~(2+)与卟啉环成功配位。电化学测试结果表明,负载硫的PCN-222-Cu(S-in-PCN-222-Cu)电极在1C的倍率下循环300周后可逆比容量为840 mAh·g~(-1)。当倍率提高到3C时,循环800周后的容量仍保持430 mAh·g~(-1),每周容量衰减率为0.042%。S-in-PCN-222-Cu电极的电化学性能远优于S-in-PCN-222,说明配体上的Cu~(2+)与卟啉环的协同作用能有效降低电化学极化,从而显著提升卟啉基金属有机框架材料用作硫载体的电化学性能和循环稳定性。

Cu-Porphyrin Based Metal Organic Frameworks for High-Performance Lithium-Sulfur Batteries

Copper ions can be coordinated into porphyrin ligands of PCN-222 directly to form PCN-222-Cu, which is first used for lithium-sulfur batteries in this study. The crystal structure, morphology and electrochemical properties were characterized systematically by ultraviolet-visible (UV-Vis) spectra, powder X-ray diffraction (PXRD), N₂ adsorption-desorption test, scanning electron microscope (SEM), cyclic voltammetry (CV) and galvanostatic charge-discharge test. UV-Vis spectra indicate Cu²⁺ was successfully coordinated into the porphyrin. The electrochemical test results showed that the reversible specific capacity of S-in-PCN-222-Cu electrodes could maintain 840 mAh·g^-1 after 300 cycles at 1C. When the rate was increased to 3C, S-in-PCN-222-Cu electrode could still maintain a high reversible specific capacity of 430 mAh·g^-1 after 800 cycles, and the capacity decay rate was only 0.042% per cycle, which was much better than that of S-in-PCN-222 electrode. This result indicates that the synergistic effect of Cu²⁺ and N atoms in the porphyrin rings can effectively decrease the electrochemical polarization, thus significantly improve the electrochemical performance and cycling stability of the porphyrin-based metal-organic framework as sulfur hosts.