Methods of producing a lithium carbon fluoride primary battery

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. The fluorinated carbon nanoparticles can be formed by fluorinating carbon nanoparticles using a fluorine-based reactive gas at a temperature in the range from 300 to 600 C., and the fluorinated carbon nanoparticles can further be used to form the cathode of the primary battery. Producing the Li/CFx primary batter can also include heating the fluorinated carbon nanoparticles under an inert atmosphere before the fluorinated carbon nanoparticles are used to form the cathode of the primary battery.

Claims

1. A method of producing a Li/CFx primary battery, the method including: forming fluorinated carbon nanoparticles by fluorinating carbon nanoparticles using a fluorine-based reactive gas at a temperature in the range from 300 to 600 C.; using the fluorinated carbon nanoparticles to form a cathode of the primary battery; and incorporating the cathode that includes fluorinated carbon nanoparticles with a lithium-based anode.

2. A method of producing a Li/CFx primary battery according to claim 1, wherein forming the fluorinated carbon nanoparticles comprises forming fluorinated carbon nanoparticles having a number-weighted diameter distribution in which a D10 particle diameter is at least 10 nm.

3. A method of producing a Li/CFx primary battery according to claim 2, further comprising: measuring the number-weighted diameter distribution by one or more of scanning electron microscopy, transmission electron microscopy, or atomic force microscopy.

4. A method of producing a Li/CFx primary battery according to claim 1, wherein forming the fluorinated carbon nanoparticles comprises forming fluorinated carbon nanoparticles having a number-weighted diameter distribution, as measured by scanning electron microscopy, transmission electron microscopy, or atomic force microscopy, in which a D90 particle diameter is at most 300 nm.

5. A method of producing a Li/CFx primary battery according to claim 1, wherein forming the fluorinated carbon nanoparticles comprises forming fluorinated carbon nanoparticles wherein diameters of substantially all of the fluorinated carbon nanoparticles are in a range from 1 to 500 nm.

6. A method of producing a Li/CFx primary battery according to claim 1, wherein a value of x is at least 0.3.

7. A method of producing a Li/CFx primary battery according to claim 1, wherein a value of x is at most 1.2.

8. A method of producing a Li/CFx primary battery according to claim 1, wherein forming the fluorinated carbon nanoparticles comprises forming fluorinated carbon nanoparticles with a specific surface area of at least 10 m.sup.2/g.

9. A method of producing a Li/CFx primary battery according to claim 1, wherein forming the fluorinated carbon nanoparticles comprises forming equiaxed fluorinated carbon nanoparticles.

10. A method of producing a Li/CFx primary battery according to claim 1, wherein forming the fluorinated carbon nanoparticles comprises forming fluorinated carbon nanoparticles having aspect ratios less than 2.

11. A method of producing a Li/CFx primary battery according to claim 1, wherein the method further includes: heating the fluorinated carbon nanoparticles under an inert atmosphere before the fluorinated carbon nanoparticles are used to form the cathode of the primary battery.

12. A method of producing a Li/CFx primary battery according to claim 11, wherein heating the fluorinated carbon nanoparticles includes heating at a temperature between 100 and 400 C.

13. A method of producing a Li/CFx primary battery according to claim 1, further comprising: separating the cathode and the anode with a separator.

14. A method of producing a Li/CFx primary battery according to claim 13, the separator including one or more of polyethylene, polypropylene, glass fibre, polytetrafluoroethylene, polyimide, or cellulose.

15. A method of producing a Li/CFx primary battery according to claim 8, the specific surface area of at least some of the fluorinated carbon nanoparticles being at least 100 m.sup.2/g.

16. A method of producing a Li/CFx primary battery according to claim 8, the specific surface area of at least some of the fluorinated carbon nanoparticles being at least 200 m.sup.2/g.

17. A method of producing a Li/CFx primary battery according to claim 8, the specific surface area of at least some of the fluorinated carbon nanoparticles being at least 500 m.sup.2/g.

18. A method of producing a Li/CFx primary battery according to claim 8, the specific surface area of the fluorinated carbon nanoparticles being at most 2000 m.sup.2/g.

19. A method of producing a Li/CFx primary battery according to claim 1, the lithium-based anode including one or more of boron or magnesium.

20. A method of producing a Li/CFx primary battery according to claim 1, further comprising: incorporating an electrolyte including one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, dissolved lithium salt, or a molten salt containing lithium and a eutectic composition with at least one of KCl or NaCl.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure is described in conjunction with the appended figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

(2) FIG. 1 shows a typical scanning electron microscopy (SEM) image of a CFx cathode material for use in a Li/CFx primary battery;

(3) FIG. 2 shows a typical diffuse reflectance infrared Fourier transform (DRIFT) spectrum of the CFx cathode material;

(4) FIG. 3 shows a thermal gravimetric analysis (TGA) profile of the CFx cathode material;

(5) FIG. 4 shows a typical X-Ray diffraction pattern of CFx nanoparticles;

(6) FIG. 5A shows a typical X-ray photoelectron spectroscopy (XPS) spectra of survey obtained from the surface of the CFx cathode material;

(7) FIG. 5B illustrates a corresponding C1s XPS scan with respect to FIG. 5A; and

(8) FIG. 5C illustrates the corresponding F1s XPS scan with respect to FIGS. 5A and 5B.

(9) In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

DETAILED DESCRIPTION

(10) 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.

(11) 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.

(12) 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 CF bonds. The Li ion conductivity and activation energy of breaking CF bonds is closely related to the structure and particles size of CFx.

(13) Advantages that nanoparticle structures have over conventional cathode materials are their high packing densities, large exposed surface areas and low activation energies for CF 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 CF bonds from the CFx nanoparticles may facilitate the discharge process, allowing higher capacity to be obtained.

(14) Below are described analyses of suitable CFx carbon nanoparticles.

(15) FIG. 1 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.

(16) FIG. 2 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.sup.1 and the weaker band at 1325 cm.sup.1 are due to the carbon-fluorine stretching frequency of CFx.

(17) FIG. 3 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.

(18) FIG. 4 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 2 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.

(19) FIG. 5A shows a typical X-ray photoelectron spectroscopy (XPS) spectra of survey obtained from the surface of the CFx cathode material. FIGS. 5B and 5C show the corresponding C1s XPS scan and F1 s XPS scan, respectively. The XPS was performed on a K-Alpha X-ray photoelectron spectrometer (Thermo Scientific) with an Al K micro focused monochromated X-ray source. The XPS spectra confirm that the CFx materials are mainly composed of the elements carbon and fluorine.

(20) 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.

(21) 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.

(22) 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.

(23) 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.

(24) 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.

(25) 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.

(26) In some embodiments, the specific surface area of the fluorinated carbon nanoparticles may be at least about 10 m.sup.2/g, and preferably at least about 100, 200 or 500 m.sup.2/g. The specific surface area of the fluorinated carbon nanoparticles may be at most about 2000 m.sup.2/g.

(27) The lithium-based anode may be formed of lithium metal, or a lithium alloy such as LiMg or LiBMg.

(28) 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.

(29) 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.

REFERENCES

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