Methods for fabricating high-performance and lightweight lithium-ion batteries based on silicon and cnts

Abstract

A composition for a lithium-ion battery anode includes an active material layer comprising silicon nanoparticles and a conductive binder, and a carbon nanotube current collector. The lithium-ion battery anode is a self-standing lithium-ion battery anode. A method of preparing a lithium-ion battery anode includes spinning a carbon nanotube fabric via chemical vapor deposition, winding the carbon nanotube fabric onto a collector, coating a slurry of silicon nanoparticles onto the carbon nanotube fabric, and optionally annealing the slurry of silicon nanoparticles. A lithium-ion battery includes a cathode, a free-standing anode, a separator, and an electrolyte. The free-standing anode includes a carbon nanotube current collector and an active material layer including silicon nanoparticles and a conductive binder.

Description

METHODS FOR FABRICATING HIGH-PERFORMANCE AND LIGHTWEIGHT LITHIUM-ION BATTERIES BASED ON SILICON AND CNTSSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0001] This invention was made with government support under Grant No. 1842494, awarded by the National Science Foundation. The government has certain rights in the invention. This invention was also made with support from the Welch Foundation under Grant No. C-1668.CROSS REFERNCE TO RELATED APPLICATIONS

[0002] This application claims priority to United States Provisional Application Serial No. 62 / 625,641, filed January 26, 2024, of which the entirety is hereby incorporated by reference.BACKGROUND

[0003] Silicon is generally known as the highest capacity anode material to date for Li- ion batteries (LIBs). Its specific capacity is up to ten times more than graphite, leading to LIBs with an increased energy density in a range of 20% to 40%. However, during repeated charge-discharge cycles, significant volume expansion (up to 300%) leads to electrode fragmentation or pulverization, resulting in the loss of electrical connection. As a result, performance degradation occurs, which has limited the commercialization of silicon-based LIBs. Various techniques to overcome this problem have been reported. For example, composites of silicon and graphite have been attempted, but the small amount of silicon used in the composites have resulted in incremental increases in specific capacity. This has been further aggravated by the fact that the conventional electrode fabrication needs both a polymeric binder and a conductive additive (i.e., carbon black), lessening even more the capacity gain of silicon inclusion in the electrodes. The transition of silicon from only a minor electrode component to the main active material is desirable to realize an energy enhancement at the cell level and hit the energy targets for the next generation of batteries.

[0004] Further LIBs with high energy densities are desirable for a multitude of applications, including electric vehicles, consumer electronics, and renewable energy storage. Conventional current collectors, primarily composed of metal foils, have remained unchanged since the inception of the first commercial lithium-ion battery. However, in addition to being made from critical materials, metal current collectors contribute substantial weight to the electrodes (15-30%) without adding to the battery's capacity. In order to increase the capacity of LIBs, it is crucial not only to utilize energy- dense active materials, but also to reduce the fractional mass of copper current collectors for LIB anodes.SUMMARY

[0005] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0006] In one aspect, embodiments disclosed herein relate to a lithium-ion battery anode composition. The composition may include an active material layer comprising silicon nanoparticles and a conductive binder, and a carbon nanotube current collector. The lithium-ion battery anode may be a self-standing lithium-ion battery anode.

[0007] In another aspect, embodiments disclosed herein relate to a method of preparing a lithium-ion battery anode.] The method may include spinning a carbon nanotube fabric via chemical vapor deposition, winding the carbon nanotube fabric onto a collector, coating a slurry of silicon nanoparticles onto the carbon nanotube fabric, and optionally annealing the slurry of silicon nanoparticles.

[0008] In yet another aspect, embodiments disclosed herein relate to a lithium-ion battery. The lithium-ion battery may include a cathode, a free-standing anode, a separator, and an electrolyte. The free-standing anode may include a carbon nanotube current collector and an active material layer including silicon nanoparticles and a conductive binder.

[0009] Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.BRIEF DESCRIPTION OF DRAWINGS

[0010] FIG. 1 is a schematic of an active layer, according to one or more embodiments.

[0011] FIG. 2 is a schematic of an anode, according to one or more embodiments.

[0012] FIG. 3 is a schematic of a method of making a current collector, according to one or more embodiments.

[0013] FIG. 4A and FIG. 4B are example SEM images, according to one or more embodiments.

[0014] FIG. 5A and FIG. 5B are example XPS spectra, according to one or more embodiments.

[0015] FIG. 6 is an example FTIR spectrum, according to one or more embodiments.

[0016] FIG.7 is an example TGA curve, according to one or more embodiments.

[0017] FIG. 8A and FIG. 8B are example images and SEM images, according to one or more embodiments.

[0018] FIG. 8C is an example diagram of a coin cell, according to one or more embodiments.

[0019] FIG. 8D is an example SEM image, according to one or more embodiments.

[0020] FIG. 9 is an example EDX spectrum, according to one or more embodiments.

[0021] FIG. 10A is an example schematic of a mechanical peel test, according to one or more embodiments.

[0022] FIG. 10B is an example force-displacement curve, according to one or more embodiments.

[0023] FIG. 10C is an example SEM image, according to one or more embodiments.

[0024] FIG. 11 is a plot of electrochemical cycling data, according to one or more embodiments.

[0025] FIG. 12 is a plot of electrochemical cycling data, according to one or more embodiments.

[0026] FIG. 13A and FIG. 13B are example SEM images, according to one or more embodiments.

[0027] FIG. 14A is a plot of electrochemical cycling data, according to one or more embodiments.

[0028] FIG. 14B is a plot of electrochemical cycling data, according to one or more embodiments.

[0029] FIG. 14C is a voltage profile plot, according to one or more embodiments.

[0030] FIG. 14D is a plot of electrochemical cycling data, according to one or more embodiments.

[0031] FIG. 15A is a plot of electrochemical cycling data, according to one or more embodiments.

[0032] FIG. 15B is a plot of electrochemical cycling data, according to one or more embodiments.

[0033] FIG. 15C is a plot of electrochemical cycling data, according to one or more embodiments.

[0034] FIG. 15D is a plot of electrochemical cycling data, according to one or more embodiments.

[0035] FIG. 16A and FIG. 16B are example SEM images of a top of an Si / PPAN / CNTf anode, according to one or more embodiments.

[0036] FIG. 16C and FIG. 16D are example SEM images of a bottom of an Si / PPAN / CNTf anode, according to one or more embodiments.

[0037] FIG. 17A a plot of electrochemical cycling data, according to one or more embodiments.

[0038] FIG. 17B is a plot of electrochemical cycling data, according to one or more embodiments.

[0039] FIG. 17C is a plot of a voltage profile according to one or more embodiments.

[0040] FIG. 17D is a plot of electrochemical cycling data, according to one or more embodiments.

[0041] FIG. 18 is an example bar graph of cell-level specific energies, according to one or more embodiments.

[0042] FIG. 19 is an example SEM image of a Si / CNT film, according to one or more embodiments.

[0043] FIG. 20 is an example of an electrochemical cycling graph, according to one or more embodiments.DETAILED DESCRIPTION

[0044] In one aspect, embodiments disclosed herein relate to a lithium-ion battery anode composition. The composition may include an active material layer including silicon nanoparticles and a conductive binder. The conductive binder may be a material including pyrolyzed polyacrylonitrile, carbon nanotubes, and combinations thereof. Silicon nanoparticles combined with the conductive binder may increase the anode’s capacity and improve cycle life. The lithium-ion battery anode composition includes a carbon nanotube current collector. The carbon nanotube current collector may increase the energy density of the anode without sacrificing capacity. The lithium-ion battery anode may be self-standing.COMPOSITION OF LITHIUM-ION BATTERY ANODE

[0045] In accordance with one or more embodiments of the following disclosure, a lithium-ion battery anode includes an active material layer including silicon nanoparticles and a conductive binder, and a carbon nanotube current collector. The anode may be self-standing. Self-standing anodes are anodes that do not include a metallic current collector. The anode may have a capacity retention of 1000 mAg g'1for a minimum of 700 cycles when tested in a half cell at a current density of 1 A g'1against a lithium metal reference.

[0046] As noted above, the lithium-ion battery anode includes an active material layer. A schematic of the active material layer 100 according to one or more embodiments is shown in FIG. 1. The active material layer 100 may include silicon nanoparticles 110. Silicon nanoparticles store electrons produced at the anode from the splitting of a lithium atom into a lithium ion and electron. The silicon nanoparticles 110 may be any commercial silicon nanoparticles suitable for use in lithium-ion battery anodes. Silicon nanoparticles suitable for use in LIB anodes may have a purity at least 95%. For example, the silicon nanoparticles may be MSE PRO 3N Silicon Nanopowder from MSE Supplies. In one or more embodiments, the silicon nanoparticles 110 have a particle size ranging from 50 to 2000 nanometers (nm) in diameter. For example, the silicon nanoparticles 110 may have a particle size with a lower limit of one of any 50, 100, 250, 500, 750 and 1000 nm with an upper limit of one of any 1000, 1250, 1500, 1750, and 2000 nm, where any lower limit may be combined with any mathematically compatible upper limit. In some embodiments, the silicon may not be nanoparticles, but rather, it may be a bulk silicon layer that has a porous structure.

[0047] The active material layer 100 also includes a conductive binder 120. A conductive binder is used in an anode to improve the cycling of electrons in the anodic material (i.e., the silicon nanoparticles). Conventional conductive binders are generally conductive polymer materials. However, these conventional binders suffer from poor cycle life with silicon anodes, likely due to the expansion and contraction of silicon upon cycling. The conductive binder 120 described herein includes a material selected from the group of pyrolyzed polyacrylonitrile, carbon nanotubes, and combinations thereof. These materials are more robust upon cycling, allowing for longer cycle life of the silicon-based anodes herein. However, some amount of a conductive polymer may be included in the binder of the anodes described herein.

[0048] As noted above, the binder may include pyrolyzed polyacrylonitrile. The pyrolyzed polyacrylonitrile may be made from any commercial polyacrylonitrile suitable for conductive binders. For example, the polyacrylonitrile may be obtained from Sigma-Aldrich. The polyacrylonitrile may be pyrolyzed after being obtained commercially. Pyrolysis may be conducted at temperatures ranging from 250 to 600 °C, and is described in greater detail in subsequent sections. For example, pyrolysismay be conducted at temperatures ranging from a lower limit of one of 250, 300, 350, and 400 °C to an upper limit of one of 450, 500, 550 and 600 °C, where any lower limit may be paired with any mathematically compatible upper limit. In one or more embodiments, the polyacrylonitrile has a molecular weight ranging from 100,000 to 500,000 g / mol.

[0049] The conductive binder 120 may include carbon nanotubes. The carbon nanotubes may include single-walled carbon nanotubes, few-walled carbon nanotubes, and mixtures thereof. The carbon nanotubes in the conductive binder 120 may have from 1 to 5 layers. The carbon nanotubes may be produced by chemical vapor deposition or may be obtained commercially. Examples of suppliers for the commercial carbon nanotubes include OCSiAl, Meijo Nano Carbon, and Nanocyl. The carbon nanotubes may be dispersed in the active material layer 100 to form a conductive network.

[0050] As noted above, in some embodiments, the conductive binder 120 includes some polymer binder. The polymer may include pyrolyzed polyacrylonitrile or any other polymer suitable for use in lithium-ion battery anodes. However, when included, the conductive binder may include less than 30 wt%, or 25 wt%, or 20 wt%, or 15 wt%, or 10 wt%, or 5 wt% or 2 wt% or 1 wt% of the polymer binder. In one or more embodiments, the active material layer includes an amount ranging from 5 to 20 wt% of carbon nanotubes based on the total weight of the active material layer.

[0051] As depicted in FIG. 1, the active material layer 100 includes silicon nanoparticle 110 and a conductive binder 120. When the conductive binder 120 includes carbon nanotubes, the weight ratio between the conductive binder and the silicon nanoparticles 110 may be less than when the conductive binder includes some polymer binder. In one or more embodiments. The weight ratio between the conductive binder 120 and the silicon nanoparticles may range from 2 to 20 wt%. As such, embodiments in accordance with the present disclosure advantageously have a higher percentage of active material.

[0052] The active material layer 100 may be in a particulate form. The particles of the active material layer may have a diameter ranging from 50 nanometer to 5 microns.

[0053] The lithium-ion battery anode also includes a carbon nanotube current collector. As shown in FIG. 2, the active material layer 100 may be adhered to the carbon nano tube current collector 210 in the lithium-ion battery anode. Current collectors are required to collect current generated at the anode and connect to external circuits. Conventional anode current collectors are typically made of copper. By replacing the copper current collector with a carbon nanotube current collector, the overall weight of the lithium-ion battery anode may be reduced and energy density thus increased.

[0054] The carbon nanotube current collector 210 may be a carbon nanotube fabric. The carbon nanotube fabric may include single-walled carbon nanotubes (SWCNTs), few-walled carbon nanotubes (FWCNTs), or mixtures thereof. The SWCNTs and FWCNTs may have carbon nanotubes of different diameters which allows the carbon nanotubes to slide relative to each other. The SWCNTs may have a diameter in the range of 0.5 to 10 nm. The FWCNTs may have less than or equal to 15 layers of carbon nanotubes. The FWCNTs may have a diameter in a range of 1 to 15 nm. Some or all of the SWCNTs and FWCNTs may be flattened. The carbon nanotube fabric may include an amount of SWCNTs and FWCNTs of 85% by mass or more The carbon nanotube fabric may have a thickness ranging from 1 to 50 microns when included as the current collector in the disclosed anode. For example, the thickness of the carbon nanotube fabric may range from a lower limit of one of 1, 5, 10, 15, and 20 microns to an upper limit of one of 25, 30, 35, 40, 45, and 50 microns, where any lower limit may be paired with any mathematically compatible upper limit. In one or more embodiments, the carbon nanotube fabric is non-woven. Non-woven refers to the carbon nanotubes in the fabric not being arranged in a woven pattern, but rather randomly entangled in the fabric.

[0055] The lithium-ion battery anode, according to embodiments described herein, may have an improved capacity retention and cycle life as compared to conventional lithium-ion batteries employing silicon anodes. The improved capacity retention and cycle life may be a result of the use of PPAN or carbon nanotubes as the conductive binder, which is more robust during the expansion and contraction of silicon during cycling. The capacity retention may be 1000 mAg g'1for a minimum of 700, 600, 500, 400 or 300 cycles when tested in a half cell at a current density of 1 A g'1against alithium metal reference. Furthermore, the energy density of the battery overall is higher, due to the use of carbon instead of copper as the current collector.METHOD FOR MAKING LITHIUM-ION BATTERY ANODE

[0056] In accordance with one or more embodiments, a method for preparing a lithium- ion battery anode is depicted in FIG. 3. The method 300 includes generating a carbon nanotube fabric 310 via floating catalyst chemical vapor deposition (FCCVD). The floating catalyst chemical vapor deposition may occur in a vertical reactor 330. In other embodiments, the FCCVD may occur in a horizontal reactor, or a reactor tilted at an angle as appropriate. The carbon nanotube fabric 310 may be spun directly upon leaving the furnace where the carbon nanotubes are generated from the gas phase. In other embodiments, the carbon nanotubes may be assembled in a post-processing step. The FCCVD precursors 320 may include a carbon source, a floating catalyst and optionally a promoter. The carbon source may be a hydrocarbon, alcohol, or other volatile carbon compound, including toluene, benzene, methanol, ethanol, propanol, butanol, methane, biogenic methane, ethane, ethylene, acetylene, propane, propylene, butane, and combinations thereof. The flow rate of gases during the FCCVD process may range from 750 seem (standard cubic centimeters per minute) to 1500 seem, such as a lower limit of any one of 750, 800, 900, 1000, and 1100 seem to an upper limit of any one of 1000, 1100, 1200, 1300, 1320, 1400 and 1500, where any lower limit may be paired with any mathematically compatible upper limit. The carbon source may be mixed in a gas mixture. The gas mixture may include hydrogen and an inert gas, such as helium, neon, argon, or combinations thereof.

[0057] The floating catalyst 340 may be ferrocene, an aerosol of Fe particles, an aerosol of metallic particles, iron pentacarbonyl or other suitable organometallic compounds, and combinations thereof. The promotor may be a compound containing sulfur, selenium, or combinations thereof. Examples of the promotor include thiophene, sublimed sulfur, H2S, and selenium. The floating catalyst chemical vapor deposition may occur at a temperature ranging from 800 to 1500°C.

[0058] Once the carbon nanotubes have been formed via FCCVD, the method may include winding the carbon nanotube fabric onto a collector. The collector may be a Teflon substrate. Other examples of the substrate may include generic plastic, metallicfoil, a porous polymer, or a ceramic substrate. The carbon nanotube fabric may be drawn from the vertical reactor and wound continuously on the collector, as shown by arrow 350. The rate of winding may be between 1 and 50 meters per minute. The winding may occur over a time period ranging from 10 to 150 minutes. The winding time may be adjusted according to the desired thickness of a resulting film (i.e., the carbon nanotube fabric). The thickness of the resulting film may depend on the reactor production rate, the winding rate, the substrate surface area, and the time period for winding. The resulting film may be used as a current collector.

[0059] After winding the carbon nanotube fabric onto a substrate, the method 300 may include densifying the carbon nanotube fabric 310 (not pictured in FIG. 3). Densifying may occur with high purity isopropanol. High purity refers to isopropanol with a purity equal to or greater than 98%. Any other suitable volatile liquid of industrial grade may be used. The carbon nanotube fabric 310 may be densified by wetting or immersing the carbon nanotube fabric into the volatile liquid, followed by evaporation of the volatile liquid.

[0060] The method 300 may include coating a slurry 360 of silicon nanoparticles onto the carbon nanotube fabric 310 or another substrate. The slurry 360 may include a component selected from the group consisting of polyacrylonitrile, carbon nanotubes, and combinations thereof to serve as a conductive binder. The slurry also includes a solvent to disperse the silicon nanoparticles and the conductive binder. The solvent may include a mixture of sulfuric acid and methanesulfonic acid. The silicon nanoparticles may be mixed with the component for a period of time ranging from 10 to 60 minutes to form the slurry, The ratio of silicon nanoparticles to the component may include 85 to 91 wt% of silicon nanoparticles to 9 to 15 wt% of the component. The slurry of silicon nanoparticles including the conductive binder forms an active material layer.

[0061] Prior to addition to the slurry, carbon nanotubes and silicon nanoparticles may be purified. Purifying the carbon nanotubes may include first purifying by furnace oxidation at a temperature ranging from 300 to 500 °C under 80 standard cubic centimeters per minute (seem) nitrogen gas and 20 seem oxygen gas for a period of time of 12 hours. The oxygen and nitrogen gas flow rates may be adjusted as needed. Purifying the carbon nanotubes may then include forming a carbon nanotube solutionby adding the carbon nanotubes to a solvent. The solvent may be sulfuric acid. The carbon nanotube solution may be mixed for a period of time around 12 hours. The carbon nanotube solution may then be speed mixed (i.e. , with a FlackTek mixer) for a period of time of 10 minutes, then added step-wise to a solvent of methanesulfonic acid. Purifying the silicon nanoparticles may include adding the silicon nanoparticles to a solvent mixture of sulfuric acid and methanesulfonic acid and sonicating for a period of time of about 8 hours. After purifying, both the carbon nanotubes and the silicon nanoparticles, each of the mixtures may be added together to form the slurry.

[0062] The coating may be conducted using a technique selected from the group consisting of spray casting, doctor-blading, dip coating, roll-to-roll processing, spin coating, and combinations thereof. In some embodiments, rather than coating directly onto the carbon nanotube fabric, the slurry may be coated on a non-reactive substrate, such as aluminum. After coating the slurry on the non-reactive substrate, the slurry may form layers that may be removed and then adhered to the carbon nanotube fabric current collector.

[0063] In particular embodiments, spray casting may occur using an airbrush (i.e., Model G22, Master Airbrush). The time and rate of spray coating may depend on the viscosity of the slurry. In one or more embodiments, the time of spray coating ranges from 1 to 5 minutes. The resulting layer may have a thickness ranging from 2 to 25 microns.

[0064] In other embodiments, the coating may be conducted by doctor-blading. Doctorblading may include mixing the slurry of silicon nanoparticles and carbon nanotubes in an oleum / methanesulfonic acid solution. Other acids may include chlorosulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and nitric acid. In one or more embodiments, the oleum / methanesulfonic acid solution is at least 6.7 grams of methanesulfonic acid per gram of oleum. The total amount of methanesulfonic acid may be greater than 15 grams per gram of oleum. The slurry of silicon nanoparticles and carbon nanotubes in the oleum / methanesulfonic acid solution may be mixed immediately before casting. Mixing may include rapid stirring via conventional methods for a period of 5 to 60 minutes. After mixing, the slurry may be cast by doctorblading onto a substrate. The substrate may be stainless steel, aluminum, polyethyleneterephthalate (PET), or carbon nanotubes, among others. In one or more embodiment, the substrate is a carbon nanotube current collector. After casting, the slurry may be placed in a coagulation bath to solidify into a film of carbon nanotubes and silicon nanoparticles, which then may be removed from the substrate to form a self-standing anode. The slurry may be placed in the coagulation bath at ambient temperature over a period of time ranging from 5 to 30 minutes. The coagulation bath may include pure water, acetone, or other known coagulation solvents. After the coagulation bath, the slurry may be rinsed with deionized water.

[0065] The method 300 may include annealing the slurry 360 of silicon nanoparticles on the carbon nanotube fabric 310. Annealing may occur in an inert atmosphere, such as in argon gas or nitrogen gas. Annealing comprises heating to a first temperature in a range of 50 to 350 °C and a second temperature in a range of 350 to 600 °C. Heating to the first temperature may occur over a period of time ranging from 15 to 30 minutes. Heating to the second temperature may occur over a period of time ranging from two to three hours. Annealing the slurry may convert the polyacrylonitrile into pyrolyzed polyacrylonitrile. Pyrolyzed polyacrylonitrile may provide continuous electronic conductivity for the anode.COMPOSITION FOR LITHIUM-ION BATTERY

[0066] Embodiments described in the present disclosure relate to a lithium-ion battery. The lithium-ion battery may include a free-standing anode, a cathode, a separator, and an electrolyte. The free-standing anode may include a carbon nanotube current collector and an active material layer comprising silicon nanoparticles and a conductive binder. The carbon nanotube current collector and active material layer are as previously described. The carbon nanotube current collector may be a carbon nanotube fabric. The thickness of the carbon nanotube fabric may range from 1 to 25 microns. For example, the thickness of the carbon nanotube fabric may range from a lower limit of one of 1, 2, 5, 10, and 12 microns to an upper limit of one of 5, 7, 12, 15, 20, and 25 microns, where any lower limit may be paired with any mathematically compatible upper limit.

[0067] The lithium-ion battery includes a cathode. The cathode may be a commercial cathode suitable for use in lithium-ion batteries. For example, the cathode may be LiFePCE (LFP), LiNio.33Coo.33Mno.33O2 (NMC-111), LiNio.4Mno.4Coo.2O2 (NMC-442),LiNio.5Mno.3Coo.2O2 (NMC-532), LiNio.6Mno.2Coo.2O2 (NMC-622), LiNio.8Coo.1Mno.1O2 (NMC-811), LiMn2O4(LMO), LiNio.5Mm.5O4 (LMNO), LiNi0.8Co0.15Al0.05O2 (NCA), Lii.i5Nio.i5Mno.55Coo.i50i.7 (LR-NMC), LiCoO2(LCO), LiMnCh (LMO), LiNiCh (LNO), and combinations thereof. The choice of the cathode may depend on the voltage, power, and energy required for the lithium-ion battery.

[0068] In one or more embodiments, the lithium-ion battery includes a separator. The separator may be a porous membrane. Known materials for the separator may include polyethylene, polypropylene, ceramics, and combinations thereof. Example separators may include Celgard 2325 PP / PE / PP and separators produced by MTI Corp.

[0069] The lithium-ion battery includes an electrolyte. Exemplary electrolytes may include 1 M Li LiPFe (Strem Chemicals, Inc.) in ethylene carbonate / diethylene carbonate (EC / DEC): dimethyl carbonate (DMC):fluoroethylene carbonate (FEC) at 2:1:1 w / w ratio (Novolyte Technologies Inc.). Example cathodes may include LiNio.5Mno.3Coo.2O2, or LiNixMnyCozO2, where X+Y+Z-l (NMC), lithium iron phosphate (LiFePO4), or lithium cobalt oxides (LiCoO2). Example separators may include Celgard 2320 trilayer (polypropylene-polyethylene -polypropylene) microporous membranes.

[0070] In one or more embodiments, the lithium-ion battery anode results in an improved energy density at the cell level, when paired with a commercial cathode. An average energy density improvement in a range of 24% to 29% may occur at the cell level using the lithium-ion battery anode including the carbon nanotube fabric, pyrolyzed polyacrylonitrile, and silicon nanoparticles as compared to conventional copper or aluminum current collectors. Further, the lithium-ion battery anode, as described herein, results in a lower weight with a carbon nanotube current collector, as compared to a conventional copper current collector. The weight may be up to 20% less than the conventional copper current collector.EXAMPLES

[0071] Example 1: Production of Non-woven CNT Fabrics

[0072] The non-woven CNT fabrics (CNTf) were spun directly from the gas phase, generated in a floating-catalyst chemical vapor deposition (FC-CVD) vertical reactorunder hydrogen atmosphere at 1300 °C. The aerogel was formed using toluene as the carbon source, ferrocene catalyst, and thiophene promoter using a known method. The as-prepared aerogels were drawn from the reactor and wound continuously (e.g., with the rate of 28 m min'1) on a Teflon substrate over either 20 or 80 min. The resulting non-woven CNTf were either condensed with high-purity isopropanol (IPA) or used as-is for Si anode deposition. The fabric comprised mostly few-walled CNTs with low residual catalyst amount (-8 wt%), as confirmed by thermal gravimetric analysis (TGA) and Raman spectroscopy. CNTf thickness was measured using a digital electronic micrometer (AccuRemote).

[0073] Example 2: Synthesis of Si / PPAN Anodes

[0074] The Si / PPAN anodes were fabricated by mixing Si nanoparticles (50 nm, MSE Supplies) and polyacrylonitrile (PAN, Mw-150,000, Sigma- Aldrich) at a mass ratio of 70:30 in A,A-dimethylformamide (DMF, >99.9%, Sigma- Aldrich). The well-mixed slurry was spray-coated onto previously prepared CNTf (both condensed and uncondensed versions) using an airbrush (Model G22, Master Airbrush) and then dried under vacuum. Note that for the uncondensed CNTf, the spraying of Si / PAN slurry collapsed the macro-porosity of the CNT structure, embedding some amount of Si nanoparticles into the top layer of the CNTf in the process. This embedding is shown in the scanning electron microscope images FIG. 4A and FIG. 4B, where FIG. 4B is a higher magnification of FIG. 4A. Si / PAN was also spray-coated onto commercial copper foils (MTI Corp.) to make control samples. The anode sheets were subsequently annealed under an inert argon atmosphere at 280 °C for 30 min and 550 °C for 50 min. The pyrolysis converted the PAN to its conjugated form PPAN. This is shown in the x- ray photoelectron spectroscopy (XPS) spectra of FIG. 5A and FIG. 5B, the infrared spectroscopy (FTIR) spectra in FIG. 6, and the TGA curve in FIG. 7. The conjugated form PPAN provides the continuous electronic conductivity of the final Si / PPAN anodes. Error! Reference source not found, summarizes the 3-step synthesis process of the Si / PPAN / CNTf anode sheets. These sheets were punched into disks 12.7 mm in diameter for coin-cell testing.

[0075] Example 3: Characterization of Si / PPAN / CNTf anodes

[0076] The morphologies as well as cross-sections of the Si / PPAN / CNTf electrodes were characterized with scanning electron microscopy (SEM) and energy dispersive X- ray spectroscopy (EDX) using an FEI Helios NanoLab 660 DualBeam system. The electron beam was configured with a low voltage of 2 kV and a beam current of 100 pA to reduce charging effects and minimize sample damage during imaging. The accelerating voltage was increased to 10 kV for EDX spectroscopy.

[0077] Non-woven CNT fabrics (CNTf) were first synthesized with the FC-CVD method. Si / PAN was then spray-coated on top of the CNTf; and the whole electrode was pyrolyzed under inert argon atmosphere to create the final Si / PPAN / CNTf anode, as pictured in Error! Reference source not found. 8 A and FIG. 8B. Before being punched out and assembled into coin cells for testing with Li counter electrodes (as shown in the example diagram in FIG. 8C), the Si / PPAN / CNTf anodes were characterized under SEM-EDX. FIG. 8A and FIG. 8B show the SEM images of the front and back sides of Si / PPAN / CNTf. The front side consists of Si nanoparticles approximately 50 - 100 nanometers in diameter that are bound together by the PPAN polymer matrix. The mass loading of Si within this layer is approximately 80% as confirmed by energy dispersive x-ray spectroscopy (EDX), as shown in FIG. 9 and Table 1, below.

[0078] Table 1 - Elemental composition of Si / PPAN / CNTf front side from EDXThe back side shows the CNT fabric with moderate degree of CNT bundles alignment. FIG. 8D displays a typical cross-section of the Si / PPAN / CNTf anodes under SEM. The total thickness of this particular Si / PPAN / CNTf sample is around 23 pm, with the CNTf occupying the 5- m thick lower layer, while the Si / PPAN residing in the upper layer. It is important to note that the carbon signal (green) not only comes from the CNTf, butalso weakly from the PPAN polymer in the Si / PPAN matrix. The crossing of the silicon and carbon signal intensities right at the interface between Si / PPAN and CNTf clearly exemplifies good contact between the two layers, which is visible in FIG. 8D. Notably, for the Si / PPAN / CNTf electrode version where the CNTf was not condensed with IPA but during the Si / PAN spray-coating step, the deposition embedded a small amount of Si nanoparticles into the top 2-pm layer of the 5-pm thick CNTf, as evidenced in FIG. 4A and FIG. 4B.

[0079] Example 4: Mechanical Peel Test of Si / PPAN electrodes

[0080] The mechanical properties of the Si / PPAN electrodes on CNTf were probed by performing peel tests using a high precision miniaturized Kammrath und Weiss tensile stage equipped with the load cell of 47 N. For a typical peel test, an area of 2 mm (width) x 4 mm (length) of Scotch Tape was attached to the active material face of a 4 mm x 13 mm coupon of the electrode. The specimens were then clamped to the tensile stage and the tape was peeled at a rate of 10 pm s'1while recording the forcedisplacement data. Peel strength was calculated by dividing the recorded force by the width of the sticky tape (2 mm).

[0081] The mechanical properties of the Si / PPAN / CNTf electrodes were probed via the mechanical peel test described above. A schematic representation of the test is depicted in FIG. 10A. The obtained results are depicted in Error! Reference source not found. 10B and FIG. 10C. Postmortem micrograph of the samples (FIG. 10C) demonstrated that a significant portion of the active material (i.e., Si / PPAN) remained on the CNTf layer. This confirms strong adhesion of the Si / PPAN particles to the CNTf layer and suggests that the cohesive failure occurs in the inorganic phase (i.e., the Si / PPAN active material). Such strong adhesion is crucial for preserving the electrical conductivity and impeding active material pulverization over consecutive charge and discharge cycling. The obtained results support desirable adhesion of the active material to the CNTf-based current collectors, in accordance with the obtained results from the cross-sectional microscopy (see FIG. 8C). An exemplary force-displacement curve of the Si / PPAN / CNTf electrode is shown in FIG. 10B, revealing an average peel strength of 3.5 N m .

[0082] Example 4: Electrochemical Testing

[0083] Coin cells (CR2032, MTI Corp.) were used for half-cell testing with Li foil counter-electrodes and Celgard 2325 PP / PE separators. The electrolyte was prepared by dissolving 1 M LiPFe (Strem Chemicals, Inc.) in a solvent system consisting of ethylene carbonate / diethylene carbonate (EC / DEC):dimethyl carbonate (DMC):fluoroethylene carbonate (FEC) at a 2:1:1 w / w ratio (Novolyte Technologies Inc.). Coin-cell assembling was performed in an argon glove box (Innovative Technologies Inc.) with O2 and H2O levels below 0.2 ppm. All battery tests were conducted at room temperature on an Arbin Instruments BT-2143 tester. For galvanostatic charge-discharge studies, coin cells were cycled under two regimes: capacity control where lithiation depth was limited to 1000 mAh g’1with respect to anode mass, and full potential at the voltage range between 0.01 - 1.0 V. For Si / PPAN / CNTf electrodes, the anode mass included all three Si, PPAN, and CNTf components; for Si / PPAN electrodes on Cu, the anode mass did not include the Cu current collector. As the current rates and lithiation depth were set with respect to the anode mass, Si / PPAN in the Si / PPAN / CNTf electrodes utilized higher specific capacities (in capacity-control cycling) at higher effective current densities compared to those in the Si / PPAN / Cu electrodes. Such differences would also be larger as the CNTf percentage increased in the Si / PPAN / CNTf composite. The current rate for both charging and discharging was set at 0.1 A g’1for five formation cycles, then increased to either 0.5 A g’1or 1 A g’1for long-term cycling. Rate capability tests were also performed either with capacity control (i.e., 1000 mAh g’1) or with deep discharge, with current rate gradually ramped up from 0.1 to 0.5, 1, 3, 6 A g’1(10 cycles at each stage), and then back down to 0.5 A g’1for long-term cycling. Cyclic voltammetry was performed for the full voltage range at a scan rate of 0.05 mV s’1.

[0084] The electrochemical performance of Si / PPAN anodes with a copper current collector was evaluated in half-cells with Li foil as the counter and reference electrodes. These examples show how PPAN performs better than the use of conductive carbon, such as “Super P”, a high-purity carbon black material, specifically engineered for use in battery electrodes. Example electrochemical cycling graph FIG. 11 shows that Si / PPAN has a better capacity retention as compared to Si with PAN and 10% conductive carbon. Example electrochemical cycling graph FIG. 12 shows that when the state of charge is controlled to 1000 mAh g-1, Si / PPAN can cycle stable.

[0085] SEM images of the Si / PPAN electrodes before cycling (FIG. 13 A) and after cycling (FIG. 13B) show that the Si undergoes swelling and volume expansion. The scale bar is 500 nanometers.

[0086] The electrochemical performance of Si / PPAN / CNTf anodes was evaluated in half-cells with Ei foil as the counter and reference electrodes. As listed in Table 2, the average mass loading of the total Si / PPAN / CNTf composite electrodes was around 0.90 - 1.10 mg cm'2.

[0087] Table 2 - Thicknesses and mass loadings of major components in the Si-based anodes.

[0088] Coin cells were galvanostatically tested in two cycling regimes: capacity control where lithiation depth is limited to 1000 mAh g’1, and full potential at the voltage range between 0.01 - 1.0 V, as shown in FIG. 14A and FIG. 14B respectively. The current for both charging and discharging was set at 0.1 A g'1for five formation cycles, then increased to either 0.5 A g'1(full-potential regime) or 1 A g'1(capacity-control regime) for long-term cycling. Si / PPAN / CNTf demonstrated an outstanding cycle life in the capacity-control regime, consistently delivering 1000 mAh g'1capacity with respect to total anode mass at 1 A g'1(1 C-rate equivalent) for at least 718 cycles before showing signs of fading (FIG. 14A). The total anode mass here included all three components: Si, PPAN, and CNTf. The initial Coulombic efficiency was 68.14% in the first cycle, while long-term cycling resulted in an average Coulombic efficiency of 99.56%. For full-potential cycling, the lithiation capacity of Si / PPAN / CNTf anodes reached 2958 mAh g'1in the first cycle, with the corresponding Coulombic efficiency of 86.95% (FIG. 14B). It is not unusual for the initial first-cycle Coulombic efficiency to be higher in the case of full-potential cycling than in capacity-control cycling, as a higher amount of Ei ions were used to lithiate Si reversibly in the former case than in the latter case, with respect to the same amount of Ei ions being irreversibly consumed for SEIformation in both cases. For long-term cycling, Si / PPAN / CNTf in the full-potential regime exhibited respectable capacity retention, being capable of retaining 1000 mAh g'1after 365 cycles, with an average Coulombic efficiency of 99.80%. FIG. 14C displays the voltage profiles of the first 2 cycles for both capacity-control and fullpotential cycling regimes. Both cases exhibited a long plateau in the first lithiation curve around 0.1 V due to the phase transition of crystalline Si to amorphous Si during the first alloying with Li. Interestingly, for the capacity-control regime, the depth of lithiation at around 0.1 V was sufficient for the cell to reach 1000 mAh g'1capacity. As clearly demonstrated above, by controlling the lithiation depth to approximately one- third of our Si / PPAN / CNTf anodes’ full-potential capacity, the material’ s cycle life was prolonged due to less volume expansion and associated electrode stress. Also, better cyclability may be correlated to the avoidance of consecutively transitioning between the amorphous LixSi (x<3.75) and crystalline LiisSi4 phases, relieving extra mechanical stress and hence improving cycling performance.

[0089] Additionally, FIG. 14D shows another example electrochemical cycling graph of full-potential cycling test similar to FIG. 14B, but with a rate capability test incorporated at the beginning. For this test, the current was gradually ramped up from 0.1 to 0.5, 1, 3, and 6 A g'1(10 cycles at each stage), then back to 0.5 A g'1for longterm cycling. The cell’s capacity expectedly decreased as the cycling current was increased, sustaining averages of 1592, 978, and 366 mAh g'1at 1, 3, and 6 A g'1respectively. Notably, such high charge-discharge currents did not induce any apparent damage to Si / PPAN / CNTf, as the capacity quickly recovered when the current was switched back to 0.5 A g’1, and the long-term capacity retention was practically identical to the full-potential cycling regime without the rate capability test (FIG. 14B).

[0090] Additional electrochemical testing was performed (results not shown). The cyclic voltammetry demonstrated the anodic and cathodic peaks regularly associated with Si materials, whose current intensities increased over the first 5 cycles due to the gradual activation of Si. After the transition from crystalline to amorphous Si in the first cycle, lithiation of amorphous Si was observed starting at around 0.2 V in the second cycle. In the other direction, two peaks at around 0.3 and 0.5 V represented the reversible delithiation of Li-Si alloy to amorphous Si.

[0091] In addition, half-cell testing of the Si / PPAN / CNTf electrode version, whose CNTf had not been condensed with IPA prior to Si / PAN deposition, was also performed (results not shown). This version of the Si / PPAN / CNTf electrode demonstrated identical electrochemical activity, and most notably, an excellent cycle life of 818 cycles at 1000 mAh g'1lithiation depth and 0.5 A g'1current rate with respect to total anode mass.

[0092] Finally, galvanostatic half-cell tests of Si / PPAN-on-Cu electrodes were also performed and displayed in FIGs. 15A-15D. These tests served as direct comparisons to the Si / PPAN / CNTf results, showcasing practically identical electrochemical performance. In particular, Si / PPAN on Cu exhibited a remarkable cycle life, which was 814 cycles for capacity-control cycling at 1000 mAh g'1with respect to Si / PPAN mass (FIG. 15A and 15C). The full-potential capacity retention and rate capability were also expectedly similar to those of Si / PPAN / CNTf electrodes (FIG. 15B and FIG. 15D). This is despite the fact that the Si / PPAN on Cu experienced lower lithiation depth (in capacity-control cycling) and effective current densities by approximately 13 - 16% due to the testing configurations as mentioned above. Collectively, these results exemplify the successful replacement of the thick and heavy Cu substrate by CNTf, eliminating the non-active current collector mass almost entirely (from 8.60 mg cm'2for Cu to 0.14 mg cm'2for CNTf) without incurring any decrease in electrochemical performance of the Si / PPAN active material.

[0093] SEM images of the top and bottom of the Si / PPAN / CNTf electrodes are shown in FIGs. 16A-16D. FIG. 16A shows the top Si / PPAN before cycling while FIG. 16B shows the top Si / PPAN after cycling. FIG. 16C shows the bottom CNTf before cycling while FIG. 16D shows the bottom CNFf after cycling. These images show how it appears that the silicon is able to penetrate through the CNTf.

[0094] Example 5 : Effects of Increasing CNT Fabric Thickness

[0095] Thicker CNT fabrics with higher mass loadings were also produced for Si / PPAN / CNTf anode synthesis. As shown in Table , the standard CNTf (with a 20- min spinning time) used in the previous section have an average thickness of 5 pm and mass loading of 0.14 mg cm'2, thus contributing minimal non-active weight to the Si / PPAN / CNTf anodes. In contrast, CNTf produced from 80-min spinning time havecorrespondingly 4 times the thickness and mass loading at 20 pm and 0.60 mg cm'2, respectively.

[0096] Table 3 - Mass and thickness comparison of different CNT fabrics

[0097] Such non-active weight from the thick CNTf becomes a substantial contribution to the anode mass when considering the average Si / PPAN mass loading of around 1.00 mg cm'2. This was reflected in the half-cell battery tests of Si / PPAN on thick CNTf demonstrated in FIGs. 17A-17D. Similarly, for these tests, the coin cells were cycled against Li foil in either capacity-control (FIG. 17A and FIG. 17D) or full-potential (FIG. 17B) regime. The current for both charging and discharging was set at 0.1 A g'1for five formation cycles, then increased to 0.5 A g'1for long-term cycling. The capacity-control cycling test illustrated in FIG. 17D incorporated a rate capability test at the beginning, where the current was gradually ramped up from the formation rate of 0.1 A g'1to 0.5, 1, 3, and 6 A g'1(10 cycles at each stage), then back to 0.5 A g'1for long-term cycling. Here, specific capacities and currents were also defined with respect to the total Si / PPAN / CNTf anode mass, including both the Si / PPAN and thick CNTf mass. This indicates that the Si / PPAN in these samples experienced higher lithiation depth in the capacity-control cycling regime (1652 mAh g-lsi / ppA\ for FIG. 17A and 1845 mAh g- lsi / ppA\ for FIG. 17D), as well as higher effective current densities (by around 43 - 54%) than their counterparts on the thin CNTf. Consequently, a shorter cycle life in capacity-control cycling (252 and 306 cycles for FIG. 17A and FIG. 17D, respectively) and lower capacity retention in full-potential cycling (FIG. 17B) was observed. A direct comparison in capacity retention can be made between electrodes with thin and thick CNTfs under full-potential cycling (FIG. 14B and FIG. 17B, respectively): at the 500thcycle, the sample on thin CNTf (FIG. 14B) demonstrated a capacity of 879 mAh g'1or 1025 mAh g-1si / ppAN, while the one on thick CNTf (FIG. 17B) showed a capacity of 576 mAh g'1or 944 mAh g-lsi / ppAN. This highlighted the effect of thick CNTf in adding non-active mass to the overall electrode composition: while the specific capacity with respect to total anode mass was greatly reduced, thespecific capacity with respect to Si / PPAN was comparable. The slightly lower value in the latter sample was likely due to the higher effective current density experienced by the Si / PPAN, as explained previously. In terms of rate capability, Si / PPAN on thick CNTf were able to sustain the lithiation depth of 1000 mAh g'1at 0.1, 0.5, and 1 A g'1current densities, while reducing to averages of 715 mAh g'1and 310 mAh g'1at 3 A g" 1 and 6 A g’1, respectively (FIG. 17D). The capacity then recovered to 1000 mAh g'1as the current was reverted back to 0.5 A g'1for long-term cycling.

[0098] Another effect of higher CNTf mass fraction in the Si / PPAN / CNTf composite was the increased SEI formation throughout the CNTf lower layer. This resulted in lower Coulombic efficiency values during the first cycles in both capacity-control cycling (between 60 - 63%) and full-potential cycling (around 78%) regimes. The activity of the thick CNTf current collector could be detected in the first-cycle voltage profiles of both cycling regimes (FIG. 17C), where the lithiation potential started at around 1.2 V to around 0.095 V, resulting in approximately 315 mAh g'1of capacity. For comparison, the thin CNTf in our earlier tests (FIG. 14C) initiated its lithiation potential at around 0.7 - 0.8 V, generating approximately 169 mAh g'1of capacity only. Importantly, the voltage behavior of the thick CNTf current collector was only observed in the first cycle.

[0099] Example 6: Energy Density Improvement

[0100] The CellEst model was used for cell specific energy calculations using the parameters as indicated below and in Table 4.

[0101] Table 4 - Parameters used for cell specific energy calculations with the CellEst modelPositive electrode composition: 0.91:0.04:0.05 (active material conductive carbombinder) Separator porosity: 0.50Al foil areal density: 2.7 mg cm'2Cu foil areal density: 4.48 mg cm'2CNTf areal density: 0.14 mg cm'2Separator areal density: 1.419 mg cm'2Electrolyte density: 1.2 g cm'3Capacity ratio N / P = 1.1, where N is the Negative Electrode Capacity, which is the total capacity of the anode, typically expressed in milliampere-hours per gram (mAh / g). P is the Positive Electrode Capacity, which is the total capacity of the cathode, also expressed in mAh / g. The ratio is given by N / P = Capacity of Anode (N) / Capacity of Cathode (P).

[0102] Calculations using the CellEst model estimate an average improvement of around 25% in energy density at the cell level, for instance, from 200 and 302 Wh kg'1to 258 and 373 Wh kg'1for LiFePCU and Li-rich NMC cathodes respectively, by switching from Si / PPAN on copper to Si / PPAN / CNTf in pouch cells, as demonstrated by FIG. 18.

[0103] Example 7: Si / CNT films

[0104] An active layer material example of Si / CNT films were generated by mixing silicon nanoparticles with CNT in an oleum / methanesulfonic acid (OF-MSA). An example SEM image of the Si / CNT film is shown in FIG. 19. As a control sample, theslurry was cast via doctor-blade onto stainless steel substrate and then placed in a coagulation bath / wash & film lift-off from substrate. The films were then tested for capacity and cycle life. FIG. 20 illustrates that the free-standing Si / CNT composite anode shows high silicon loading, but reduced capacity and cycle life compared to the Si / PPAN / CNTf system of Example 4.

[0105] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMSWhat is claimed:

1. A lithium-ion battery anode composition, comprising: an active material layer comprising silicon nanoparticles and a conductive binder; and a carbon nanotube current collector, wherein the lithium-ion battery anode is a self-standing lithium-ion battery anode.

2. The lithium-ion battery anode composition of claim 1, wherein the conductive binder includes a material selected from the group consisting of pyrolyzed polyacrylonitrile, carbon nanotubes, and combinations thereof.

3. The lithium-ion battery anode composition of claim 1 or 2, wherein the conductive binder comprises 5 to 20 wt% of carbon nanotubes based on a total weight of the active material layer.

4. The lithium-ion battery anode composition of any one of claims 1-3, wherein the conductive binder comprises less than 30 wt% of a polymer binder.

5. The lithium-ion battery anode composition of any one of claims 1-4, wherein the silicon nanoparticles have a particle size in a range of 50 to 2000 nm.

6. The lithium-ion battery anode composition of any one of claims 1-5, wherein the current collector is a carbon nanotube fabric.

7. The lithium-ion battery anode composition of claim 6, wherein the carbon nanotube fabric is non-woven.

8. The lithium-ion battery anode composition of claim 6 or 7, wherein the carbon nanotube fabric has a thickness ranging from 1 to 50 pm.

9. The lithium-ion battery anode composition of any one of claims 6-8. wherein carbon nanotubes of the carbon nanotube fabric have a diameter ranging from 0.5 to 15 nml.

10. The lithium-ion battery anode composition of any one of claims 1-9, wherein the lithium-ion battery anode has a capacity retention of 1000 mAg g'1for a minimum of 700 cycles when tested in a half cell at a current density of 1 A g'1against a lithium metal reference.

11. A method of preparing a lithium-ion battery anode, comprising: spinning a carbon nanotube fabric via chemical vapor deposition; winding the carbon nanotube fabric onto a collector; coating a slurry of silicon nanoparticles onto the carbon nanotube fabric; and optionally annealing the slurry of silicon nanoparticles.

12. The method of claim 11, wherein the chemical vapor deposition comprises using a floating catalyst comprising a carbon source selected from the group consisting of toluene, benzene, methanol, ethanol, propanol, butanol, methane, biogenic methane, ethane, ethylene, acetylene, propane, propylene, butane, and combinations thereof.

13. The method of claim 12, wherein the floating catalyst comprises a ferrocene catalyst.

14. The method of any one of claims 11-13, wherein the slurry comprises a component selected from the group consisting of polyacrylonitrile, carbon nanotubes, and combinations thereof.

15. The method of any one of claims 11-14, wherein annealing the slurry of silicon nanoparticles comprises heating to a first temperature ranging from 50 to 350 °C and a second temperature ranging from 350 to 600 °C.

16. A lithium-ion battery comprising: a cathode; a free-standing anode, comprising: a carbon nanotube current collector; and an active material layer comprising silicon nanoparticles and a conductive binder; a separator; and an electrolyte.

17. The lithium-ion battery of claim 16, wherein the conductive binder is selected from the group consisting of pyrolyzed polyacrylonitrile, carbon nanotubes, and combinations thereof.

18. The lithium-ion battery of claim 16 or 17, wherein the conductive binder is carbon nanotubes.

19. The lithium-ion battery of any one of claims 16-18, wherein the cathode is selected from the group consisting of LiFePC (LFP), LiNio.33Coo.33Mno.33O2 (NMC-111), LiNio.4Mno.4Coo.2O2 (NMC-442), LiNio.5Mno.3Coo.2O2 (NMC-532), LiNio.6Mno.2Coo.2O2 (NMC-622), LiNio.8Coo.1Mno.1O2 (NMC-811), LiMn2O4(LMO), LiNio.5Mn1.5O4 (LMNO), LiNio.8Coo.15Alo.05O2 (NCA), Lii.i5Nio.i5Mno.55Coo.i50i.7 (LR-NMC), LiCoO2(LCO), LiMnO2(LMO), LiNiO2(LNO), and combinations thereof.

20. The lithium-ion battery of any one of claims 16-19, wherein the carbon nanotube current collector is a carbon nanotube fabric present in a layer having a thickness ranging from 1 to 50 pm.

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