Metal fluorides as conversion electrodes in lithium ion batteries

In collaboration with Prof. Max Fichtner's group, we have characterized the structure of Fe/LiF/C conversion electrodes used as cathode materials in lithium-ion batteries. The conversion materials prepared by pyrolysis of ferrocene with LiF initially consist of iron (and some iron carbide) nanoparticles with a thin graphitic shell, interconnected by MWCNTs (Fig. 3.4). Charging leads to the formation of FeF2/C or FeF3/C nanoparticles with the graphitic shell still present. Both, the graphitic shell and the MWCNTs are crucial for a good cyclic behavior with the graphitic shell presumably responsible for the cyclic stability of the iron nanoparticles and the MWCNTs ensuring electrical contact through the electrode.   

TEM Characterization of Battery Materials

Fig. 3.4: a) BF-TEM overview image of aggregates of Fe/C nanoparticles with LiF in between and interconnected by MWCNTs; b/c) HRTEM images of the Fe/C nanoparticles consisting of an α-iron core and a shell typically of in-situ TEM characterization of up to 3-5 graphene layers.

 

Details have been published at

  • Modified synthesis of [Fe/LiF/C] nanocomposite, and its application as conversion cathode material in lithium batteries, R. Prakash et al. Journal of Power Sources 196 (2011) 5936-5944; DOI: 10.1016/j.jpowsour.2011.03.007.
  • A ferrocene-based carbon-iron lithium fluoride nanocomposite as a stable electrode material in lithium batteries R. Prakash, A.K. Mishra, A. Roth, C. Kübel, T. Scherer, M. Ghafari, H. Hahn, M. Fichtner J. Mat. Chem., 2010, 20(10), 1871-1876; DOI:10.1039/B919097J
  • Carbon encapsulated-iron lithium fluoride nanocomposite as high cyclic stability cathode material in lithium batteries R. Prakash, C. Kübel, M. Fichtner Materials Challenges in Alternative and Renewable Energy, G. Wicks, et al. (Eds.), Ceram. Trans., 2011, 224, 173-182, Wiley Inc., New Jersey; DOI: 10.1002/9781118019467.ch18
  • Synthesis of [Co/LiF/C] nanocomposite and its application as cathode in lithium-ion batteries C. Wall, R. Prakash, C. Kübel, H. Hahn, M. Fichtner J. Alloys Comp., 2012, 530, 121-126; DOI: 10.1016/j.jallcom.2012.03.080