An aluminum–ion battery comprised of fluorinated natural graphite cathode, aluminum anode and AlCl3 containing imidazolium based ionic liquid as electrolyte is reported for the first time. Electrochemical method of preparation of fluorinated natural graphite lead to formation of non-covalent C-F bonds. The cycle life studies (40 cycles) of the battery indicated very stable electrochemical behavior and the discharge capacity of the battery is 225 mAh g−1.
For the first time, natural graphite is successfully fluorinated electrochemically using triethylamine tri(hydrofluoride) (C 2 H 5 ) 3 N.3HF adduct. The nature of the C-F bond formed in graphite fluoride is deduced from FT-IR, Raman and XPS spectroscopy. Electrochemical discharge of the semi-ionic fluorinated graphite as cathode in magnesium cell is investigated and the discharge capacity of the C-F electrode is found to be 548 mAh/g. Graphite-fluorine cathode prepared by this procedure showed rechargeable nature in combination with magnesium anode. Fluorine based materials have a prominent place in energy storage and conversion systems. Its use stems from the intrinsic stability and ability to generate high electrochemical energy as electrodes. These attributes are direct result of the extraordinary electro negativity of fluorine and exceptionally high free energy of formation of fluorides.The surface modification or fluorination of graphite 1-3 has been assumed to yield important electrode modifications by Tressaud et al.,4 i.e., Surface oxygen is reduced to some extent. The surface area of the electrode material is increased, with a subsequent increase of metal-ion intercalation and/or adsorption in the electrode. This latter property may be due to two factors: (i) an increase in the structural disorder caused by fluorination which probably diminishes the length of the graphitic domains and induces the formation of surface nanopores in which excess metal can be accommodated.Graphite fluorides have been studied as cathode materials in lithium 5-8 or aluminum batteries 9 Nakajima et al. 10 had shown that a low fluorination of graphite can improve the capacitance of C-F in Li battery system during the insertion into the resulting materials in comparison with graphite. As a matter of fact the treated graphite samples, which contain small amounts of fluorine (0.5-3.7 atom %), exhibit discharge capacities of about 380 mAh/g. Giraudet et al. 11 had reported the preparation method of semi-ionic graphite fluoride material and used in lithium battery system, which showed a capacitance value of 530 mAh/g. Rechargeable metal-ion batteries are well adapted for portable electronic devices, research in this field mostly concerns lithium intercalation batteries. These batteries have two major limitations, cost of the battery and their environmental impact. Magnesium is an appropriate alternative for lithium, because it is less harmful and naturally more abundant than lithium.Preliminary work on Mg/graphite fluoride system 12 showed that graphite fluorides could be an interesting cathode for magnesium ion-transfer batteries, 13-17 the graphite fluoride used was prepared from iodine fluoride, hydrogen fluoride and fluorine gas. The nature of C-F bond in the graphite fluoride prepared by this method was covalent. One of reasons for poor efficiency of the system was difficult diffusion of Mg 2þ into the graphite fluoride material due to hindering of the IF z species in the material.Fluorine-graphite intercalation compounds...
Rechargeable battery with pure magnesium metal as anode and electrolytically fluorinated natural graphite cathode with gelatinized ionic liquid based electrolyte is developed. The self assembled gel electrolyte is beneficial in enhancing the cell performance by improving the reversibility of the electrodes. The fluorinated natural graphite facilitates Mg intercalation and de-intercalation. The specific capacity of the cell is 100 mAhg −1 , average discharge voltage is 1.6 V at constant current discharge of 0.1 mAcm −2 .
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