Electrochemistry of carbon subfluorides
Subfluorinated carbonaceous materials obtained through direct fluorination of graphite or coke particles are provided. One set of subfluorinated carbonaceous materials has an average chemical composition CF x in which 0.63<x≦0.95, 0.66<x≦0.95 or 0.7<x≦0.95. The subfluorinated carbonaceous materials are capable of electrochemical performance superior to commercial CF at relatively high rates of discharge.
1. A subfluorinated graphite material having an average chemical composition CFx in which 0.63≦x≦0.95, and comprising
i) carbon strongly bound to fluorine and carbon weakly bound to fluorine or
ii) carbon strongly bound to fluorine, carbon weakly bound to fluorine and unfluorinated carbon,
wherein the relative amount of unfluorinated carbon and carbon weakly bound to fluorine is greater than or equal to 5% and less than 37% and 13 C nuclear magnetic resonance spectroscopy analysis of the subfluorinated graphite material provides a spectrum comprising a chemical shift peak centered from 130 to 150 ppm relative to TMS, a chemical shift peak centered at 84 to 89 ppm relative to TMS, and a chemical shift peak centered at 43 to 49 ppm relative to TMS.
2. The subfluorinated graphite material of claim 1 , wherein 0.66≦x≦0.95.
3. The subfluorinated graphite material of claim 2 , wherein 0.7≦x≦0.95.
4. The subfluorinated graphite material of claim 1 , wherein the spectrum comprises a chemical shift peak centered at approximately 140 ppm relative to TMS.
5. The subfluorinated graphite material of claim 1 , wherein the relative amount of unfluorinated carbon and carbon weakly bound to fluorine is greater than or equal to 10% and less than or equal to 20%.
6. An electrochemical device comprising an anode, a cathode, and an ion-transporting material therebetween, wherein the cathode comprises a subfluorinated graphite material according to claim 1 .
7. The electrochemical device of claim 6 , wherein 0.66≦x≦0.95.
8. The electrochemical device of claim 7 , wherein 0.7≦x≦0.95.
9. The electrochemical device of claim 6 , wherein the relative amount of unfluorinated carbon and carbon weakly bound to fluorine is greater than or equal to 10% and less than or equal to 20%.
10. An electrochemical device of claim 6 , wherein the 13 C NMR spectrum comprises a chemical shift peak centered at approximately 140 ppm relative to TMS.
11. The device of claim 6 , wherein the anode comprises a source of ions of a metal selected from Groups 1, 2, and 3 of the Periodic Table of Elements.
12. The device of claim 11 , wherein the ions are lithium ions.
13. The electrochemical device of claim 6 , wherein an x-ray diffraction spectrum of the subfluorinated graphite does not comprise a substantial peak at 2θ in the range 26.3-26.4 degrees, using CuKα radiation.
14. The electrochemical cell of claim 6 , wherein the subfluorinated graphite material is present in a composition containing a conductive diluent and a binder, the subfluorinated graphite material representing about 70 wt % to about 90 wt % of the composition.
15. A method for making a subfluorinated carbonaceous material, the method comprising the steps of
a. providing graphite particles;
b. exposing the graphite particles to a flowing gaseous source of elemental fluorine;
c. heating the graphite particles to a selected reaction temperature, the selected temperature being between 330° C. and 600° C., wherein the average size of the particles is between 2 microns and 200 microns; and
d. maintaining the graphite particles at the selected temperature for a time between 2 hours and 30 hours to obtain a subfluorinated graphite material having an average chemical composition CF x in which 0.63<x≦0.95 and comprising
i). carbon strongly bound to fluorine and carbon weakly bound to fluorine or
ii) carbon strongly bound to fluorine, carbon weakly bound to fluorine and unfluorinated carbon,
wherein the relative amount of unfluorinated carbon and carbon weakly bound to fluorine is greater than or equal to 5% and less than 37% and 13 C nuclear magnetic resonance spectroscopy analysis of the subfluorinated graphite material provides a spectrum comprising a chemical shift peak centered from 130 to 150 ppm relative to TMS, a chemical shift peak centered at 84 to 89 ppm relative to TMS, and a chemical shift peak centered at 43 to 49 ppm relative to TMS.
16. The method of claim 15 , wherein the graphite particles are held at the selected temperature for a time between 8 and 20 hours.