Patent Application: US-201514935043-A

Abstract:
a li / cfx primary battery having a lithium - based anode and a fluorinated carbon cathode . the fluorinated carbon cathode includes fluorinated carbon nanoparticles . the structure and size distribution of the carbon precursor carbon nanotubes are configured to provide improved battery performance .

Description:
the ensuing description provides preferred exemplary embodiment ( s ) only , and is not intended to limit the scope , applicability or configuration of the invention . rather , the ensuing description of the preferred exemplary embodiment ( s ) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the invention , it being understood that various changes may be made in the function and arrangement of elements without departing from the scope of the invention . specific details are given in the following description to provide a thorough understanding of the embodiments . however , it will be understood by one of ordinary skill in the art that embodiments maybe practiced without these specific details . in an embodiment of the present disclosure , use of carbon nanoparticles as a substrate for fluorination and their subsequent use in high temperature batteries is provided . as discussed above , in some embodiments , the performance of the cfx material may depend on the fluorination process and the interplay between the carbon and fluorine ratio . too much fluorine brings about poor conductivity of the cathode and too little fluorine results in insufficient li ion uptake to operate as a cathode , and therefore a low capacity . furthermore , the discharge process in li / cfx batteries is associated with li ion intercalation as well as breaking of c — f bonds . the li ion conductivity and activation energy of breaking c — f bonds is closely related to the structure and particles size of cfx . advantages that nanoparticle structures have over conventional cathode materials are their high packing densities , large exposed surface areas and low activation energies for c — f bonds . the large surface areas allow a higher degree of fluorination sites to be achieved per unit weight of carbon material , with higher fluorination allowing higher capacities to be achieved . in addition , due to higher packing densities , the x value in cfx can be reduced , allowing greater conductivity in the cathode material compared to conventional cathode materials . low activation energies for c — f bonds from the cfx nanoparticles may facilitate the discharge process , allowing higher capacity to be obtained . fig1 shows a typical scanning electron microscopy ( sem ) image of a cfx cathode material for use in a li / cfx primary battery . the sem was carried out using an fei xl30 feg environmental scanning electron microscope to characterize the particle size and structure . from the image , the particle diameter of the cfx material is in the range from 10 to 200 nm . fig2 shows a typical diffuse reflectance infrared fourier transform ( drift ) spectrum of the cfx cathode material recorded on an infrared spectrometer ( nicolet 6700 , thermo scientific ) using a spectra - tech collector diffuse reflectance accessory . the principal band at 1212 cm − 1 and the weaker band at 1325 cm − 1 are due to the carbon - fluorine stretching frequency of cfx . fig3 shows a thermal gravimetric analysis ( tga ) profile of the cfx cathode material , carried out on a thermal gravimetric analyzer ( ta instrument , q5000ir ) under helium gas atmospheres . helium purge gas ( bip , air products ) was introduced at a flow rate of 10 ml / min in all experiments . from the profile , the weight loss is 67 % when the material is heated to 690 ° c . at a ramp rate of 20 ° c ./ min . fig4 shows a typical x - ray diffraction pattern of the cfx nanoparticles collected on a bruker d8 - advance x - ray diffractometer with cu ka radiation ( 0 . 1542 nm ) at an operating voltage of 40 kv4 . the pattern shows two diffraction peaks at 28 of around 13 ° and approximately 41 °. according to reported results ( 15 ) which use graphite as the cfx precursor , these peaks can be indexed to the diffraction of { 001 } and { 100 } planes . the broadening of the peaks probably results from the small size of the nanoparticles . fig5 shows ( a ) a typical x - ray photoelectron spectroscopy ( xps ) spectra of survey obtained from the surface of the cfx cathode material , ( b ) the corresponding c1s xps scan , and ( c ) the corresponding f1s xps scan . the xps was performed on a k - alpha x - ray photoelectron spectrometer ( thermo scientific ) with an al kα micro focused monochromated x - ray source . the xps spectra confirm that the cfx materials are mainly composed of the elements carbon and fluorine . cathodes can be prepared from a mixture of the cfx carbon nanoparticles , carbon additive ( s ) and a binder , such as polyvinylidene difluoride ( pvdf ), polytetrafluoroethylene ( ptfe ), polyethylene glycol ( peo ) and / or poly ( acrylonitrile ) ( pan ), in a suitable solvent . the resultant dough can be pressed using jewellers rolls , or similar , to form a sheet . the sheet can then be vacuum dried and electrodes cut to size from the sheet . test cells can be made incorporating the cfx cathode , a lithium - based anode and an organic solvent based electrolyte containing dissolved lithium salt . a separator ( e . g . formed from polyethylene , polypropylene , glass fibre , ptfe , polyimide and / or cellulose ) can be used to separate the cathode and anode to prevent a short circuit . in one embodiment , fluorinated carbon nanoparticles may be produced by fluorinating carbon nanoparticles using a fluorine - based reactive gas ( such as fluorine ) at a temperature in the range from 300 to 600 ° c . the fluorinated carbon nanoparticles may then be used , in accordance with an embodiment of the present disclosure to form a cathode of a primary battery . in one embodiment , the fluorinated carbon cathode may substantially entirely consist of fluorinated carbon nanoparticles . in some embodiments , the fluorinated carbon nanoparticles may be heated under an inert atmosphere before the fluorinated carbon nanoparticles are used to form the cathode of the primary battery . for example , the heating may be at a temperature in the range from 100 to 400 ° c . in some embodiments of the present disclosure , the fluorinated carbon nanoparticles may have a number - weighted diameter distribution , in which the d10 particle diameter is at least about 10 nm , and preferably at least about 30 nm . the fluorinated carbon nanoparticles may have a number - weighted diameter distribution , as measured by scanning electron microscopy , transmission electron microscopy and / or atomic force microscopy , in which the d90 particle diameter is at most about 300 nm , and preferably at most about 200 , 100 or 70 nm . the number - weighted diameter distribution may be obtained by : examining a microscope image of the nanoparticles and identifying at least about 50 , and preferably at least about 100 , discrete nanoparticles in the image , measuring the imaged diameters of the identified nanoparticles , and converting the imaged diameters to nanoparticles diameters using the scale of the image . in some embodiments , he particle diameters of substantially all of the fluorinated carbon nanoparticles may be in the range from about 1 to 500 nm , and preferably in the range from 1 to 100 nm . in some embodiments , the fluorinated carbon nanoparticles may be substantially equiaxed . thus the aspect ratios of substantially all of the fluorinated carbon nanoparticles may be less than about 2 , and preferably less than about 1 . 5 . in some embodiments , the value of x may be at least about 0 . 3 . the value of x may be at most about 1 . 2 . in some embodiments , the specific surface area of the fluorinated carbon nanoparticles may be at least about 10 m 2 / g , and preferably at least about 100 , 200 or 500 m 2 / g . the specific surface area of the fluorinated carbon nanoparticles may be at most about 2000 m 2 / g . the lithium - based anode may be formed of lithium metal , or a lithium alloy such as limg or libmg . the battery may have an electrolyte which is an organic solvent , such as ethylene carbonate , dimethyl carbonate , diethyl carbonate or a mixture of any two or more such organic solvents , containing dissolved lithium salt . for high temperature applications , the electrolyte can be a molten salt , such as molten salt containing lithium ions . for example , the molten salt can be licl or a composition containing licl , such as a eutectic composition with kcl and / or nacl . the foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure . those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and / or achieving the same advantages of the embodiments introduced herein . those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure , and that they may make various changes , substitutions and alterations herein without departing from the spirit and scope of the present disclosure . 1 . ruff , o ., bretschneider , o . z . anorg . allg . chem ., 217 , 1 ( 1937 ). 2 . rudorff , w ., riidorff , g . z . anorg . allg . chem ., 253 , 281 ( 1947 ). 3 . rudorff , w . adv . inorg . chem . radiochem ., 1 , 230 ( 1959 ). 4 . hamwi , a . daoud , m . coussems , j . c . synth . met ., 89 , 26 ( 1988 ). 5 . hany , p ., yazami , r ., hamwi , a . j . of power sources 708 , 68 ( 1997 ). 6 . fukuda , m ., iijima , t . international power sources symposium committee , international power sources symposium , 9th , brighton , sussex , england , september 17 - 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