Metal-Coated Fiber Additive Selection for Resistance Reduction in a Battery and Battery Materials

Abstract

The electrical resistance of active cathodic and anodic films may be significantly reduced by the addition of small fractions of conductive additives within a battery system. The decrease in resistance in the cathode and/or anode leads to easier electron transport through the battery, resulting in increases in power, capacity and rates while decreasing joules heating losses.

Claims

1. A metal-coated additive selection method for enhanced electrical conductivity in a battery y having an operating voltage, a cathode, an anode and electrolyte, the cathode comprising an active base cathode material, the anode comprising an active base anode material, and the electrolyte having cations being transported from the anode to the cathode, the metal-coated additive selection method comprising the steps of: (a) establishing the operating voltage of the battery by: (i) determining the first voltage potential of the active base cathode material against the electrolyte cation, (ii) determining the second voltage potential of the active base anode material against the electrolyte cation, and (iii) determining the difference between the first voltage potential and the second voltage potential, thereby establishing the operating voltage of the battery, (b) selecting a metal-coated additive candidate comprising a metal, (c) determining a reaction voltage potential of the selected metal-coated additive candidate against the electrolyte cation by determining the galvanic potential of the metal in the metal-coated additive candidate against the electrolyte cation, and (d) provided the galvanic potential of the metal in the metal-coated additive candidate against the electrolyte cation is less than the operating voltage of the battery, dispersing the metal-coated additive into the active base cathode material.

2. A battery cathode with enhanced electrical conductivity for use in a battery having an operating voltage and an electrolyte, the battery cathode comprising: An active base cathode material having a voltage potential as against the electrolyte; and at least one additive dispersed within the active base cathode material creating a dispersed mixture, the at least one additive comprising: a plurality of metal-coated fibers having a diameter of from 3 microns to 20 microns, a metal-coating thickness between 0.1 micron and 3 microns; and a fiber length of from 0.1 mm to 1.0 mm, the metal-coated fibers comprising a metal having an galvanic potential as against the electrolyte, the selection of the metal for the metal-coating of the metal-coated fiber being such that the galvanic potential of the metal against the electrolyte is less than the operating voltage of the battery.

3. The battery cathode of claim 2, wherein the active base cathode material comprises lithium iron phosphate (LFP) and the electrical conductivity between the conductive metal-coated fibers is further enhanced by the addition of branching nickel filamentary structures.

4. The battery cathode of claim 3, wherein metal-coated fibers comprise nickel-coated fibers.

5. The battery cathode of claim 2, wherein the active base cathode material is selected from the group of active base cathode materials consisting of lithium iron phosphate (LFP) and lithium nickel manganese cobalt oxide (MNC) and the metal-coated fibers comprise aluminum-coated fibers.

6. The battery cathode of claim 2, wherein the fiber is selected from the group of materials consisting of carbon, pan ox, silica, quartz, silicates, alumina, aluminosilicates, borosilicates, glass, minerals, carbides, nitrides, borides, polymers, cellulose, inorganic fibers, and organic fibers.

7. The battery cathode of claim 2, wherein the metal-coated fiber is precision chopped to a desired length such that the metal-coated fibers range within ±10% of the desired length.

8. The battery cathode of claim 2, wherein the metal-coated fiber is dispersed into the active base cathode material in a loading weight range of up to 15% whereby the battery cathode exhibits a decrease in volume resistivity and interface resistivity over unloaded base cathode material.

9. A battery anode with enhanced electrical conductivity for use in a battery having an operating voltage and an electrolyte, the battery anode comprising: an active base anode material having a voltage potential as against the electrolyte; and at least one additive dispersed within the active base anode material creating a dispersed mixture, the at least one additive comprising: a plurality of metal-coated fibers having a diameter of from 3 microns to 20 microns, a metal-coating thickness between 0.1 micron and 3 microns; and a fiber length of from 0.1 mm to 1.0 mm, the metal-coated fibers comprising a metal selected from the group of metals consisting of nickel and copper.

10. The battery anode of claim 9, wherein the electrical conductivity between the conductive fibers is further enhanced by the addition of addition branching nickel filamentary structures.

11. The battery anode of claim 10, wherein metal-coated fibers comprise nickel-coated fibers

12. The battery anode of claim 9, wherein the base anode material comprises a carbon powder of finely divided carbon powder particles.

13. The battery anode of claim 9, wherein the fiber is selected from the group of materials consisting of carbon, pan ox, silica, quartz, silicates, alumina, aluminosilicates, borosilicates, glass, minerals, carbides, nitrides, borides, polymers, cellulose, inorganic fibers, and organic fibers.

14. The battery anode of claim 9, wherein the plurality of metal-coated fibers is dispersed into the base anode material in a loading weight range up to 15%.

15. The battery anode of claim 9, wherein the improved electrical and mechanical properties of the anode dispersed mixture over the active base anode material comprises improved electrical conductivity in the battery anode and at least one of the improvements in the group of improvements consisting of lower resistance, lower impedance, an increase in voltage capacity, an increase in amperage capacity, increased rates and power, lower Joule heating, lower and safer operating temperatures, and commensurate higher capacities.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Exemplary embodiments of the present invention are described more fully hereinafter with reference to the accompanying drawings, in which multiple exemplary embodiments of the invention are shown. Like numbers used herein refer to like elements throughout. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be operative, enabling, and complete. Accordingly, the arrangements disclosed are meant to be illustrative only and not limiting the scope of the invention, which is to be given the full breadth of the appended claims and all equivalents thereof. Moreover, many embodiments, such as adaptations, variations, modifications, and equivalent arrangements, will be implicitly disclosed by the embodiments described herein and fall within the scope of the present invention.

[0068] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Unless otherwise expressly defined herein, such terms are intended to be given their broad ordinary and customary meaning not inconsistent with that applicable in the relevant industry and without restriction to any specific embodiment hereinafter described. As used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one”, “single”, or similar language is used. When used herein to join a list of items, the term “or” denotes at least one of the items but does not exclude a plurality of items of the list. Additionally, the terms “operator”, “user”, and “individual” may be used interchangeably herein unless otherwise made clear from the context of the description.

[0069] The drawings are schematic depictions of various components and embodiments and are not drawn to scale. Schematic depictions are being used in this application to assist in the understanding of relative relationships between the components. Understanding that these drawings depict only typical exemplary embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail with reference to the accompanying drawings in which:

[0070] FIG. 1 is a schematic depiction of an exemplary embodiment of a discharging lithium-ion battery as generally known in the prior art.

[0071] FIG. 2 is a schematic depiction of the exemplary embodiment of the lithium-ion battery of FIG. 1 during recharging as generally known in the prior art.

[0072] FIG. 3 is a representative depiction of a portion of an exemplary embodiment of a cathode as generally known in the prior art showing an active base cathode material.

[0073] FIG. 4 is a representative depiction of a portion of an exemplary embodiment of an enhanced cathode showing metal-coated fibers dispersed throughout the active base cathode material of FIG. 3.

[0074] FIG. 5 is a representative depiction of a portion of an exemplary embodiment of an alternative enhanced cathode showing metal-coated fibers and conductive filamentary structures dispersed throughout the active base cathode material of FIG. 3.

[0075] FIG. 6 is a representative depiction of a portion of an exemplary embodiment of an anode as generally known in the prior art showing an active base anode material.

[0076] FIG. 7 is a representative depiction of a portion of an exemplary embodiment of an enhanced anode showing metal-coated fibers dispersed throughout the active base anode material of FIG. 6.

[0077] FIG. 8 is a representative depiction of a portion of an exemplary embodiment of an alternative enhanced anode showing metal-coated fibers and conductive filamentary structures dispersed throughout the active base anode material of FIG. 6.

[0078] FIG. 9 is a representative depiction of a portion of an exemplary embodiment of an alternative enhanced electrode (anode or cathode) showing conductive filamentary structures dispersed throughout the base electrode material.

[0079] FIG. 10 is a chart depicting data regarding improving volume resistivity in a cathode by adding various conductors into an LFP battery cathode.

TABLE-US-00003 REFERENCE NUMERALS lithium-ion battery or battery 10 standard cathode or cathode 12 active base cathode material 14 standard anode or anode 16 active base anode material 18 electrolyte 20 separation barrier 22 anode current collector foil 24 cathode current collector foil 26 battery housing 28 schematic flow path 30 lithium ions 32 additive(s) 34 enhanced cathode 36 metal-coated fibers 38 high aspect ratio conductors 40 conductive filamentary structures enhanced anode 44 42 Arrow A (discharging direction) Dashed Arrow B (discharging direction) Arrow C (charging direction) Dashed Arrow D (charging direction)

DETAILED DESCRIPTION OF THE INVENTION

[0080] The exemplary embodiments of the present disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the exemplary embodiments of the present invention, as generally described and illustrated in the figures and examples herein, could be arranged and designed in a wide variety of different arrangements. Thus, the following more detailed description of the exemplary embodiments, as represented in the figures and examples, is not intended to limit the scope of the invention, as claimed, but is merely representative of exemplary embodiments of the disclosure.

[0081] This detailed description, with reference to the drawings, describes a representative rechargeable lithium-ion battery 10 as known in the prior art that operates with a standard cathode 12 made of an active base cathode material 14 and a standard anode 16 made of an active base anode material 18. The exemplary embodiments of the present invention comprise modified electrodes with increased conductive that separately or together may be components of an enhanced battery.

[0082] Turning to FIG. 1, a representative rechargeable lithium-ion battery 10 as known in the prior art is depicted schematically. The lithium-ion battery 10 comprises the standard cathode 12 made of the active base cathode material 14, the standard anode 16 made of the active base anode material 18, an electrolyte 20, a separation barrier 22, an anode current collector foil 24, and a cathode current collector foil 26 encased within a battery housing 28. The active base cathode material 14 may be any of many cathode compounds known to be of use in batteries; however, for the purposes of this description, the battery 10 is a lithium-ion battery 10 and exemplary active base cathode materials 14 may include lithium iron phosphate (LFP) and the lithium nickel manganese cobalt oxide (NMC) and any other cathode material used in lithium-ion batteries. The active base anode material 14 may be any of the anode materials known to be of use in batteries; however, for the purposes of this description, the battery 10 is a lithium-ion battery 10 and exemplary active base anode materials 14 may include carbon power, graphite powder, and any other cathode material used in lithium-ion batteries. Such compounds also contain a small amount of a polymer used as a binder. Also, the most used electrolyte 20 in lithium-ion batteries 10 is lithium salt, such as LiPF6 in an organic solution. The key role of electrolyte 20 is transporting positive lithium ions (cations) between the cathode 12 and anode 16.

[0083] The battery 10 operates to transport electrons through the system of components. In FIG. 1, in the discharging mode the electron transport starts with the anode current collector foil 24, then through the anode foil/active mass interface to the anode active mass (in this case, the standard anode 16). The discharging direction of electron flow (shown by schematic flow path 30) is shown generally at Arrow A from negative to positive. Positively charged lithium ions 32 travel within the electrolyte 20 (in this case, the lithium accepting an electron at the standard anode 16 when charging), that electron and lithium (of the lithium ions 32) pass across the separation barrier 22 (as shown by Dashed Arrows B) to the standard cathode 12. Separation of the electron from the lithium (of the lithium ions 32) occurs in the standard cathode 12. The electron is transported through the cathode active mass (standard cathode 12) to the active mass/foil interface then moves the electrons out of the cathode current collector foil 26 to the device it services.

[0084] FIG. 2 shows the battery 10 of FIG. 1 during charging. The charging direction of electron flow (shown by schematic flow path 30) is reversed as shown generally at Arrow C from positive to negative. Positively charged lithium ions 32 travel within the electrolyte 20 from the standard cathode 12 passing across the separation barrier 22 (as shown by Dashed Arrows D) to the standard anode 14.

[0085] Significant improvement in the conductivity of either the anode or the cathode or both leads to lower resistivity, not only across or through the respective cathodic or anodic film, but also generally across the entire battery cell. As a result, a lower resistance leads to higher voltage to move a given current or move a higher current at a given voltage. This, in turn, leads to faster charging or discharging, or the ability to move an electron at greater ease through thicker films, thus increasing capacity. There will also be a decrease in joule heating, with a corresponding reduction in temperature and in energy loss. A decrease in operating temperature also results in a more efficient and safer battery.

[0086] Described in this disclosure are exemplary conductive additives 34 (see FIGS. 4, 5, 7, 8, and 9) for the anode 16 and the cathode 12 that significantly improve conductivity enhancing the performance of these components 12, 16 and the battery 10 within which they are used. By dispersing some of these exemplary additives 34 within the active base cathode material 14 and/or the active base anode material 18, the resultant, enhanced cathode 36 and/or enhanced anode 44 exhibit increased conductivity and ion transport within the battery system is facilitated. It is also postulated that the non-carbon surfaces of the highly conductive anode additives may inhibit SEI growth.

[0087] FIG. 3 is a representative depiction of a portion of an exemplary embodiment of cathode 12 as generally known in the prior art showing an active base cathode material 14 from which the cathode 12 is made. As noted above, the active base cathode material 14 may be any of many cathode compounds known to be of use in batteries.

[0088] An exemplary embodiment of an enhanced cathode 36 showing metal-coated fibers 38 dispersed throughout the active base cathode material 14 is depicted in FIG. 4. The depiction of FIG. 4 is not drawn to scale, nor does it suggest any specific level of loading. Rather, the depiction is merely intended to give context to the dispersion of metal-coated fibers 38 within the active base cathode material 14.

[0089] FIG. 5, a magnification compared to FIG. 4, depicts an alternative exemplary embodiment of the enhanced cathode 36 showing metal-coated fibers 38 and conductive filamentary structures 42 (which are high aspect ratio conductors 40) dispersed throughout the active base cathode material 14. The structures of the conductive filamentary structures additive 42 are smaller than the metal coated fibers 38 in at least one material physical aspect, such as diameter, weight, or volume and may also exhibit branching. The electrical conductivity between the conductive metal-coated fibers 38 is further enhanced by the addition of the conductive filamentary structures additive 42. Again, the depiction of FIG. 5 is not drawn to scale, nor does it suggest any specific level of loading. Rather, the depiction is merely intended to give context to the dispersion of metal-coated fibers 38 and conductive filamentary structures additive 42 within the active base cathode material 14.

[0090] FIG. 6 is a representative depiction of a portion of an exemplary embodiment of an anode 16 as generally known in the prior art showing an active base anode material 18 from which the anode 16 is made. As noted above, the active base anode material 16 may be any of the active anode materials known to be of use in batteries.

[0091] An exemplary embodiment of an enhanced anode 44 showing metal-coated fibers 38 dispersed throughout the active base anode material 18 is depicted in FIG. 7. The depiction of FIG. 7 is not drawn to scale, nor does it suggest any specific level of loading. Rather, the depiction is merely intended to give context to the dispersion of metal-coated fibers 38 within the active base anode material 18.

[0092] FIG. 8, a magnification compared to FIG. 4, depicts an exemplary embodiment of an alternative enhanced anode 44 showing metal-coated fibers 38 and conductive filamentary structures 42 (which are high aspect ratio conductors 40) dispersed throughout the active base anode material 18. The structures of the conductive filamentary structures additive 42 are smaller than the metal coated fibers 38 in at least one material physical aspect, such as diameter, weight, or volume and may also exhibit branching. The electrical conductivity between the conductive metal-coated fibers 38 is further enhanced by the addition of conductive filamentary structures additive 42.

[0093] FIG. 9, a representative schematic depiction of a portion of an exemplary embodiment of an alternative enhanced electrode (anode or cathode), shows conductive filamentary structures additive 42 dispersed throughout the active base electrode material. Being schematic, FIG. 9 serves a dual function in that the depiction is the same for an exemplary active base cathode material 14 as for an exemplary active base anode material 18 even though such active materials likely differ from one another. Accordingly, reference numbers are provided in the alternative for cathode-related and anode-related references. The purpose of FIG. 9 is to clarify that conductive filamentary structures additive 42 may be used alone as conductive additive or may be used in combination with metal-coated fiber additive 38 as depicted in FIGS. 5 and 8.

[0094] The chart of FIG. 10 shows data regarding improving volume resistivity in a cathode by adding various conductors as additives; namely, PCF (precision chopped fiber) alone, nanostrands alone, NFP or NiFP (nickel filamentary power such as Type 255 powder (and its derivatives)) alone, PCF with nanostrands, and PCF with NiFP into an LFP battery cathode.

[0095] For purposes of this disclosure PCF comprises metal-coated precision chopped fiber wherein the metal may be either nickel or aluminum and the nickel coating may be of any known type including coatings made by vacuum processes (physical vapor deposition (PVD), sputtering, evaporation, etc.), wet chemistry processes (electroplating, electroless plating) and Chemical Vapor Deposition (CVD) and the aluminum coating may be of any known type including coatings made by vacuum processes (physical vapor deposition (PVD), sputtering, evaporation, etc.) and Chemical Vapor Deposition (CVD).

[0096] Though PCF, nanostrands, and NiFP are relatively new conductive materials, the inventor of the present invention has determined during conductive polymer (paints, adhesives, and plastics) work that 1) precision chopped fibers (PCF) are a very effective conductive additive, 2) Nanostrands are even more effective conductors, 3) filamentary nickel powders (NiFP) are marginally effective on their own, and 4) the positive effect of combining the fibers as “logs” and either the filamentary powders or nanostrands as “tumbleweeds” or the fibers and particles as “highways and byways”. In these combined applications, the nanostrands are a much better “tumbleweeds”, but the filamentary powders are more than adequate.

[0097] Nevertheless, making polymers conductive by dispersing the above-mentioned additives within polymers differs markedly from enhancing conductivity in battery systems. Batteries present a much different electron transport phenomenon, one wherein there is a very high-power direct current experienced both during charging and discharging cycles. In the case of batteries, the need to provide a high current capacity through the high aspect ratio of fibers and multiplicity of electronic pathways through logs and tumbleweeds becomes even more essential to reducing DC resistance and AC impedance.

[0098] To demonstrate these concepts in a battery cathode, a master batch of LFP cathode material was mixed. The mixture was formed into cathode films at 2.5%, 5%, 7.5% and 10% for precision chopped fiber (PCF), nanostrands (NS), and commercial nickel filamentary powder (NiFP). Then a 5% PCF mixture was loaded with 2.5% and 5% NS, and with 5% and 10% NiFP. The weight and through-thickness resistance of each film was measured. Then the chart provided as FIG. 10 was prepared as a compilation of graphs formulated from the data derived showing the films compared as a function of their additives and loading amount and normalizing these results to indicate how much of an improvement each one gives over the others. Examples #7 and #8, discussed below, are related to the results shown in the chart provided in FIG. 10. Comparing the data shows that the results are not identical, because the results are derived by different methods; however, the data values do correlate.

[0099] The following observations may be drawn from FIG. 10 and known cost and manufacturing considerations. NiFP alone yields very little improvement, but such marginal improvement may be viable for some batteries. PCF alone, which is both manufacturable and affordable, yields a decent improvement. Though relatively expensive, NS alone works best, but a commercial manufacturing process for large amounts of NS is still in development. The logs and tumbleweeds network using either NiFP or NS in conjunction with PCF works well; however, PCF+NS clearly works better.

[0100] Consequently, because the above-mentioned additives provide enhanced conductivity universally in all polymers within which dispersal is possible, the data represented in FIG. 10 evidences enhanced conductivity in all batteries within which the additives are dispersible and non-corrosively compatible.

EXAMPLES

[0101] Following are a few representative examples that demonstrate the concepts and advancements disclosed herein:

[0102] Fiber choice (Examples 1 through 3)

[0103] Example #1—Nickel-coated carbon fiber in a cathode. A nickel-coated carbon fiber (7 microns diameter, with 40% nickel coating, or 0.25 micron thick, precision chopped to 0.50 mm) provided excellent conductivity in the cathode. Adding 2% by weight of the described fiber moved the through thickness resistance of a 100 microns film from 3.5 ohms (no fiber) down to 1.5 ohms (2% fiber). However, the lithium-ion NMC coin cells made from these films would not cycle. It was discovered that the cell corroded at 3.8 volts, before reaching the 4.2 volts operating condition. This is because the half-cell potential of nickel and lithium is 3.8 volts. However, this did demonstrate that the conductivity could be greatly improved and suggested that the nickel-coated fiber should work in systems that remain below about three and a half volts (see LFP cathode examples below).

[0104] Example #2—Aluminum-coated fiber in a cathode and a coin cell. The half-cell potential of aluminum and lithium is 4.7 volts. Thus, an aluminum-coated fiber should survive a cathode having a 4.2-volt operating voltage lithium. In this case, a 0.2-micron coating of aluminum was plated over a 0.1-micron coating of nickel on carbon fiber. The dually coated fiber was chopped to 0.50 mm length. When this fiber was added to the cathode at 3%, by weight, the cell was able to successfully cycle for about a week, before the underlying nickel entered into the reaction. When these cathode films were produced, the standard cathode (made of an active base cathode material) was 130 microns thick and the fiber-loaded cathode (active base cathode material metal-coated fiber loaded) was 165 microns thick. This could likely be because the added fibers added support and drag to pull a slightly thicker film. The table below compares the thickness, resistance, voltage, and capacity of these two cells. (Each value is the average of three samples).

TABLE-US-00004 Thickness Capacity film microns Resistance Voltage mAhr standard 130 0.86 ohm 3.53 V 3.29 2% Al on Ni on 165 0.86 ohm 3.76 V 4.05 carbon fiber difference +27% same same +23%

[0105] Note that the fiber loaded film is 27% thicker than the standard film but exhibits the same resistance indicating lower resistivity. The lower resistivity resulted in a higher voltage. The implication of the higher voltage would manifest a higher rate. As the fiber loaded cathode was 27% thicker, the capacity of the fiber-loaded film was increased by 23%.

[0106] Example #3—Process of coating various fibers with CVD aluminum. Many of the previously mentioned fibers have been coated by an aluminum CVD (chemical vapor deposition) process, precision chopped to 0.5 mm and added to the cathode. Fiber examples include (but are not limited to) silicon carbide, borosilicate, quartz, mineral (basalt), surface modified carbon and organic (aramid-Kevlar). In each of these cases, the addition of 1% to 5% of the precision chopped, aluminum-CVD coated fiber improved the conductivity of the coating by values similar to that of Example #1 above. Each of these fibers will add certain advantages, or disadvantages, unique to that particular fiber, but they all work to improve the conductivity of the cathode.

[0107] Cathodes (Example 4)

[0108] Example #4—Aluminum-coated fibers precision chopped to 0.5 mm. These coated fibers were dispersed into a standard cathode mix at 3% by weight (always reserving a portion of the mix for a control). This was repeated several times, the largest variable being a batch to batch or fiber type variation in the aluminum-coated fiber conductivity.

[0109] Films were extruded onto aluminum foil with a doctor blade, the height of the blade being adjusted to achieve a consistent film thickness and weight, depending on the desired thickness and the solvent-to-solids ratio of the mix. After drying, the uncalendared films were tested for volume resistivity per ASTM Method D2739. The table below reports several of these comparative batches.

TABLE-US-00005 Volume resistivity Volume resistivity Sample control ohm-cm modified ohm-cm Improvement A 1750 615 2.8× B 2215 687 3.2× C 1617 413 3.9× D 2175 790 2.8×

[0110] With sample set D, the samples were calendared and measured for composite Volume Resistivity (CVR) and interface resistivity (IR).

TABLE-US-00006 CVR IR control 15.4 1.06 modified 12.5 0.50 improvement 1.2× 2.1×

[0111] Example #5—Higher fiber loading in cathode. A standard cathode mixture was loaded with 3%, 4%, 5% and 6% of 0.5 mm precision chopped, nickel-coated fiber having a 40% nickel coating (250 nm thickness). Attempts to mix above 6% resulted in poorer dispersion. However, the following table illustrated the improvement in through thickness volume resistivity when films of equal thickness were pulled from these mixtures.

[0112] Volume resistivity of cathode films modified with precision-chopped nickel-coated carbon fiber at 40% nickel and 0.5 mm length.

TABLE-US-00007 Weight percent of fiber added Volume resistivity ohm-cm 0% (standard film) 43.6 3% 6.55 4% 1.30 5% 0.90 6% 0.69

[0113] This effect is visualized in the graph below:

[0114] Anodes (Examples 6 and 7)

[0115] Example #6—Anode with copper-coated carbon fibers. Copper is more conductive than nickel, so copper-coated carbon fiber is more conductive than nickel-coated carbon fiber. Because the current collector of the anode is copper foil, copper-coated carbon fibers may be a viable candidate for anode improvement. In this example, up to 8% of a copper-coated carbon fiber was added to the anode. The copper coating is 40% by weight on an AS4 fiber. The copper coated carbon fiber was obtained from Technical Fiber Products of Schenectady, N.Y., and precision chopped to 0.50 mm length. The CVR of the resulting anode was reduced from 244 mohms to 56 mohms, or a 435% improvement in the CVR, while the IR was reduced from 27 mohms to 8 mohms, a 337% improvement. As a result, the voltage of the standard cell at 10 C discharge rate was 3.5V, while the voltage of the PCF copper treated cell was 3.5V at 20 C discharge rate, indicating that the treated cell discharged twice the current at the same voltage.

[0116] Example #7—Filamentary branching structures. Nickel powders produced by chemical vapor decomposition may be produced in two distinct geometrical classes; either spherical (type 1 powders) or filamentary (type 2 powders). Type 1 powders are of little use in increasing conductivity until loadings are exceptionally high, due to the need for the particles to come in close contact to each other. However, the filamentary powders become conductive at lower loadings due to the higher aspect ratio, and in part due to filamentary powders generally exhibiting some degree of branching. These powders in larger diameter format (generally above one micron in diameter of the main branch) are available through Vale or Novamet, notably as Type 255 powder (and its derivatives). Nanostrands are a filamentary branching metal having a smaller diameter with more extensive branching. Nanostrands are available from The Conductive Group, Heber City, Utah.

[0117] The type 255 powder alone did little to increase the conductivity of the system. However, the nanostrands did show a significant increase in the conductivity of the anode mix.

[0118] Of interest are the combinations of the NiPCF fibers (Nickel-coated, precision-chopped fibers) with the filamentary branching structures, forming a “logs and tumbleweeds” network.

[0119] The following table compares the CVR and IR of standard anode films to that of 5% NiPCF, 5% type 255, 5% nanostrands, and 5%+5% NiPCF/255 and 5%+5% NiPCF/nanostrands:

TABLE-US-00008 Percent Percent improvement improvement compared to compared to Additive CVR standard IR standard Standard - carbon powder 0.77  0% 0.60    0% only NiPCF fiber 5% 0.91 −15% 0.57  +6% Type 255 powder (est.) 1.0 −29% 0.40  +50% Nanostrands (est.) 0.77  0% 0.28 +115% NiPCF plus type 255 0.65 +19% 0.28 +115% NiPCF plus nanostrands 0.66 +18% 0.11 +447%
As the standard anode is already fairly conductive, it was postulated that the effect if these nickel bearing conductors will not be as dramatic as in the cathode. However, the efficacy of the NiPCF plus the nanostrands is of note. Also, adding just nickel-coated PCF shows a degree of efficacy. Hence, armed with this disclosure, it should be evident to one skilled in the art that combining nanostrands with the copper PCF of Example #6 will yield a significantly better result.

[0120] It is noted that the CVR of individual additives seem to not be very effective, but the combinations do move the CVR somewhat. They all have some effect on the IR, some very significant. This is likely because none of the additives individually are much more conductive than the carbon powder. But the “logs and tumbleweeds” provides a more complex electron transport opportunity. The IR, the interfacial resistance, suggests that the combinations of additives multiple paths directly to the underlying foil across the ever-present polymer binder barrier. Calendaring likely provides additional physical impression of the conductors into the foil.

[0121] In the anode where the carbon particles are tens of microns in size, it has been observed that the filamentary branching structures (tumbleweeds) not only provide a multiplicity of high aspect ratio paths to the nickel-coated fibers (logs), but they also tend to lay on, or tend to touch the carbon particles in multiple places (each such touching hereinafter being referred to as a “touch point”). With the more open and branched nanostrands, they tend to wrap themselves around and envelop the carbon particles, like a spider web or net, creating a nanonet and exhibiting a multiplicity of touch points. It is this fashion of multiple touching and nanonetting that adds significantly more conduction opportunities. It becomes a “logs and tumbleweeds and nanonet” model and is structured uniquely in its ability to collect current at higher rates, higher amperages, and lower voltages.

[0122] Example #8—Cathodes with branched filamentary structures. As these branching filamentary conductors are made of nickel, they can only be applied to LFP cells. Cathodes were made with no additives (control sample) and with NiPCF (chopped to a shorter 0.25 mm, refer to Example #9 below), with the branched Type 255 powder (larger diameter and less branching) alone, with the nanostrands (smaller diameter, more branching) alone, and with combinations thereof, as follows. The volume resistivity of each was reported (volume resistivity is similar, but not the same as CVR).

TABLE-US-00009 Type 255 nano- volume PCF Powder strands resistivity -mohm PCF only none none none 136 5% none none 53 10%  none none 8.1 Nanostrands only none none 2.5% 1.3 none none   5% 1.2 255 Powder only none 5% none 39 none 10%  none 20 PCF + nanostrands 5% none 2.5% 0.4 5% none 2.5% screened 3.1 PCF + 255 Powder 5% 5% none 21

[0123] Nanostrands demonstrate tremendous efficacy, both alone and with PCF. Nanostrands may be screened, such as through a 100 mesh.

[0124] Armed with this disclosure, one skilled in the art may surmise that the use of the copper- coated PCF will yield better results, though they may not be nearly as dramatic, due to the extreme efficacy of nanostrands.

[0125] Example #9—PCF length. In some battery embodiments, depending on the type and makeup of the battery, 0.50 mm PCF may prove to be too long and penetrate the separator. There are two immediate solutions to this occurrence; 1) Implement a thicker separator or a double separator (which has been found to work) or 2) make the fiber shorter. As mentioned above, making the fiber shorter may require a greater loading to achieve the same CVR. The IR, however, is not affected as much. These concepts are shown in the following table:

TABLE-US-00010 Fiber length Fiber loading CVR IR 0.50 mm 5% 50 4.1 0.25 mm 5% 70 4.2 0.25 mm 7.5%   52 4.0 0.25 mm 10%  52 4.2

[0126] Pouch Cell Batteries (Example 10)

[0127] Example #10—The example of a modified cathode is given in Example #6 above. Example #10 demonstrates the performance of two sets of lithium iron phosphate cells, one with a standard cathode and one with an additive loading of 5% by weight of nickel-coated PCF at 40% nickel and precision chopped to a 0.50 mm length. After a successful build and conditioning cycle, each of the cells were cycled to C/10 discharge rates to determine their capacities. Then each population was subjected to a series of increasing discharge rates as follows: C/2. 1C, 2C and 3C. This demonstrated that at any equivalent voltage, the nickel-coated PCF cells discharge 2.1 times faster than the standard cell, which implies that the treated cell will develop 2.1 times the power. To one skilled in the art, it should be recognized that, armed with this disclosure and according to Ohm's law, that the demonstrated increase in current at the same voltage (or increase in voltage at the same current, or reduction in resistance/impedance, both of which were also observed) leads to less Joule (resistive) heating, which will simultaneously return that energy to the battery for greater increased efficiency and a safer, lower operating temperature.

[0128] For exemplary methods or processes of the invention, the sequence and/or arrangement of steps described herein are illustrative and not restrictive. Accordingly, although steps of various processes or methods may be shown and described as being in a sequence or temporal arrangement, the steps of any such processes or methods are not limited to being carried out in any specific sequence or arrangement, absent an indication otherwise. Indeed, the steps in such processes or methods generally may be carried out in different sequences and arrangements while still falling within the scope of the present invention.

[0129] Additionally, any references to advantages, benefits, unexpected results, preferred materials, or operability of the present invention are not intended as an affirmation that the invention has been previously reduced to practice or that any testing has been performed. Likewise, unless stated otherwise, use of verbs in the past tense (present perfect or preterit) is not intended to indicate or imply that the invention has been previously reduced to practice or that any testing has been performed.

[0130] Exemplary embodiments of the present invention are described above. No element, act, or instruction used in this description should be construed as important, necessary, critical, or essential to the invention unless explicitly described as such. Although only a few of the exemplary embodiments have been described in detail herein, those skilled in the art will readily appreciate that many modifications are possible in these exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the appended claims.

[0131] In the claims, any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. Unless the exact language “means for” (performing a particular function or step) is recited in the claims, a construction under Section 112 is not intended. Additionally, it is not intended that the scope of patent protection afforded the present invention be defined by reading into any claim a limitation found herein that does not explicitly appear in the claim itself.

[0132] While specific embodiments and applications of the present invention have been described, it is to be understood that the invention is not limited to the precise configuration and components disclosed herein. Various modifications, changes, and variations which will be apparent to those skilled in the art may be made in the arrangement, operation, and details of the methods and systems of the present invention disclosed herein without departing from the spirit and scope of the invention.

[0133] Those skilled in the art will appreciate that the present embodiments may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.