Reddy M Anji, Breitung Ben, Kiran Chakravadhanula Venkata Sai, Helen M, Witte Ralf, Rongeat Carine, Kübel Christian, Hahn Horst, Fichtner Maximilian
Helmholtz Institute Ulm (HIU), Electrochemical Energy Storage Helmholtzstr. 11 D-89081 Ulm Germany
Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT) Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen Germany.
RSC Adv. 2018 Oct 31;8(64):36802-36811. doi: 10.1039/c8ra07378c. eCollection 2018 Oct 26.
Transition metal fluorides are an important class of cathode materials for lithium batteries owing to their high specific energy and safety. However, metal fluorides are electrical insulators, exhibiting slow reaction kinetics with Li. Consequently, metal fluorides can show poor electrochemical performance. Instead, carbon-metal fluoride nanocomposites (CMNFCs) were suggested to enhance electrochemical activity. Chemical synthesis of CMNFCs poses particular challenges due to the poor chemical stability of metal fluorides. Recently, we reported a facile one-step method to synthesize carbon-FeF nanocomposites by reacting fluorinated carbon (CFx) with iron pentacarbonyl (Fe(CO)) at 250 °C. The method resulted in C-FeF nanocomposites with improved electrochemical properties. Here, we have synthesized four different C-FeF nanocomposites by reacting four different CFx precursors made of petro-coke, carbon black, graphite, and carbon-fibers with Fe(CO). Electrochemical performance of all four C-FeF nanocomposites was evaluated at 25 °C and 40 °C. It is shown that the nature of CFx has a critical impact on the electrochemical performance of the corresponding C-FeF nanocomposites. The C-FeF nanocomposites were characterized by using various experimental techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, resistivity measurement, and Fe Mössbauer spectroscopy to shed light on the differences in electrochemical behaviour of different C-FeF nanocomposites.
过渡金属氟化物因其高比能量和安全性，是锂电池重要的一类阴极材料。然而，金属氟化物是电绝缘体，与锂的反应动力学缓慢。因此，金属氟化物可能表现出较差的电化学性能。相反，有人提出碳-金属氟化物纳米复合材料（CMNFCs）可增强电化学活性。由于金属氟化物化学稳定性差，CMNFCs的化学合成面临特殊挑战。最近，我们报道了一种简便的一步法，通过在250°C下使氟化碳（CFx）与五羰基铁（Fe(CO)₅）反应来合成碳-氟化铁纳米复合材料。该方法得到了具有改善电化学性能的C-FeF纳米复合材料。在此，我们通过使由石油焦、炭黑、石墨和碳纤维制成的四种不同CFx前驱体与Fe(CO)₅反应，合成了四种不同的C-FeF纳米复合材料。在25°C和40°C下评估了所有四种C-FeF纳米复合材料的电化学性能。结果表明，CFx的性质对相应C-FeF纳米复合材料的电化学性能有至关重要的影响。通过使用各种实验技术，如X射线衍射、扫描电子显微镜、透射电子显微镜、电阻率测量和Fe穆斯堡尔谱，对C-FeF纳米复合材料进行了表征，以阐明不同C-FeF纳米复合材料电化学行为的差异。
