Material for lithium battery anode

Abstract

Provided herein is a silicon-carbon material comprising silicon and preparation thereof, for use as an anode in a lithium-ion battery.

Description

P-640242-PCMATERIAL FOR LITHIUM BATTERY ANODECROSS-REFERENCE TO RELATED APPLICATION

[0001] The application claims the benefit of a United States provisional application filed in the United States Patent and Trademark Office on January 29, 2025, which was assigned Application No. 63 / 751,016, which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION

[0002] This invention is directed to a material comprising silicon and preparation thereof, for use as an anode in a lithium-ion battery .BACKGROUND OF THE INVENTION

[0003] Lithium-ion batteries have become a dominant technology for energy storage, today used in applications for cell phones, tools, portable computers, and electric motor vehicles. The key attributes of a lithium battery are its charge capacity, measured in mAh / g, and energy¬ density, measured in Wh / kg. A battery comprises an anode and a cathode, and to first order the capacity / energy density of the battery is limited by which of these two items has the lowest charge capacity.

[0004] Typical cathodes used for lithium batteries are fabricated using metal composites. Typical anodes used for lithium batteries are fabricated using graphite. Historically the pure graphite anode is the part of the battery that limits the charge capacity- and energy density.

[0005] In the last 20 years efforts to develop anodes with higher charge capacity than graphite has focused on incorporating silicon with graphite. Silicon has a larger theoretical charge capacity than graphite and by developing anode materials comprising silicon and graphite in principle the charge capacity of the anode can be increased significantly. In 1995 Wilson (J. Appl. Phys. 77(6), 2363-2369 (1995)) reported a method to deposit silicon on graphite using CVD by using a vapor containing silicon and graphite in a quartz tube, the resulting silicon carbon material exhibited a higher charge capacity than graphite.

[0006] Yet in over 20 years of research and development efforts to develop silicon graphite anode materials there are still many roadblocks to produce a low cost, manufacturable anode material that can deliver sufficient charge capacity and energy density. In addition, the battery design must lead to a practical charge / discharge cycle life to be useful relative to the cost toP-640242-PCfabricate the batten . The key roadblock is the silicon, as it will trap lithium ions during charge / discharge cycles and when the lithium in the silicon reaches a critical concentration the silicon fractures. As the silicon fractures its surface area increases, this in turn traps more lithium, leading to more fracturing, trapping lithium eventually consuming so much lithium that the charge capacity of the battery drops to an unusable level and the life of the battery is too short.

[0007] Much research has been spent to address this limitation of silicon. In 2016 US 10,170.753 was filed and disclosed a method comprising treating graphite particles to form pores or hollows and using chemical vapor deposition (CVD) to deposit silicon into the pores / hollows of the graphite, then coating the particles with carbon by CVD. In 2000, US 6,383,686 was filed and disclosed a method of coating silicon particles with carbon to slow the trapping of lithium in the silicon. Since 2000, many variants of such silicon graphite strategies have been disclosed.

[0008] When designing a silicon / graphite composite anode material, a critical performance property7is the first cycle efficiency (FCE), also referred to as initial coulombic loss (ICL) or initial coulombic efficiency (ICE). This is a leading indicator of the anode’s characteristic defects which lead to depletion the battery' of lithium and the cycle life of the battery. Efforts to make silicon graphite composite anodes with silicon nanoparticles often show undesirable FCE values, to make these kinds of composites useful a technique called pre-lithiation is used. This provides a pre-dosing of lithium to the battery to compensate for the losses from FCE / ICL, then the battery can stabilize and operate with lower losses and deliver improved cycle life. The downside of pre-lithiation is that it increases manufacturing cost.

[0009] To overcome the issues of integration of silicon into an anode, many developers have taken to highly complicated nanoparticle fabrication methods involving modification of graphite, other forms of carbon and silicon using expensive solvent processes, acid etching coatings, etc to drive towards high cycle life (e.g US2023 / 0299362 Al).

[0010] There are very few examples of ICE performance in full cell lithium ion batteries using silicon anode types. Yan in Materials Today Energy 31, 101225 (2013), discloses silicon carbon anode battery formulations. Full cell testing shows a FCE of 87%. Son in Adv. Mater.32. 2003286 (2020) discloses silicon carbon anode battery formulations. Full cell testing shows a FCE of 85%. Park in Electrochimica Acta 357, 136870 (2020) discloses silicon carbon anode battery formulations. Full cell testing shows a FCE of 78%. Li in Adv. Energy’ Mater. 10,P-640242-PC1903110 (2020) discloses silicon carbon anode battery formulations. Full cell testing shows a FCE of 71%.

[0011] While cycle life of full cell batteries fabricated with silicon carbon anodes material has been improved since 2000, there remain questions and doubts as to if the silicon carbon anode material process can be readily scaled to high volume manufacturing and meet the cost requirements of the industry.

[0012] As a result, improvements of silicon carbon anodes material are still required to produce a material which can produce a sufficient cycle lil'e / battery- lifetime and still have low manufacturing costs.SUMMARY OF THE INVENTION

[0013] In some embodiments, provided herein a silicon-carbon material comprising:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles; (b) graphite particles with silicon nodules; or combination thereof;(c) graphite particles; and(d) silicon particles;wherein more than 95% of particles (a)-(d) have a particle size <25 pm.

[0014] In some embodiments, provided herein an anode for lithium-ion battery comprising the silicon-carbon material of this invention.

[0015] In some embodiments, provided herein a lithium-ion battery comprising the anode of provided herein, an electrolyte and a binder.

[0016] In some embodiments, provided herein a process for the preparation of the siliconcarbon material of this invention, wherein the process comprises:(i) suspending graphite particles in a gas stream comprising hydrogen and silicon precursor gas using a chemical vapor deposition (CVD);(ii) ball milling the particles obtained is step (i) to reduce the particle size to < 25 pm to obtain the silicon-carbon material of this invention.

[0017] In some embodiments, provided herein a silicon-carbon material comprising:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles; (b) graphite particles with silicon nodules; or combination thereof;(c) graphite particles; andP-640242-PC(d) silicon particles;wherein more than 95% of particles (a) -(d) have a particle size < 25 pm; wherein the silicon-carbon material is prepared by the process provided herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0019] Figure 1 - Typical plan view electron microscopy images with different angles and resolutions of the silicon-carbon anode precursor product. The top six figures are magnification pictures made with an electron microscope. The graphite in these images is dark. The last two images are cross-sections from a transmission electron microscope. These images show the abrupt interface between the graphite and the silicon (as opposed to silicon growing inside the graphite.) The last two images are at different magnifications.

[0020] Figure 2 - Typical image of the ball milled silicon-carbon anode precursor product, wherein the ball-milling step does not significantly change the silicon / graphite structure.

[0021] Figures 3A-3B - shows results of the first several discharge / charge cycles of the half cell batteries made with Figure 3A: the graphite (only graphite, no silicon) used in the CVD process (left and right graphs are repeated experiment) and Figure 3B: the half cell batteries made with the siliconcarbon anode precursor material (left and right graphs are repeated experiment). Comparing Figure 3A and 3B it shows that the application of the silicon CVD process to the graphite powder increased the battery capacity by >450 mAh / g.

[0022] Figure 4 - Plot showing the relation between the percent silicon content in the anode as measured using X-ray spectroscopy and the half cell battery capacity

[0023] Figure 5 - Graphs showing the first several discharge / charge cycles of half cell battery formation for battery comprising silicon-carbon anode precursor material coated with carbon using a CVD process (left and right graphs are repeated experiment, the Table below the graphs presents the results and the average results of the experiments).

[0024] Figure 6 - Graphs showing the results of charge cycle testing of full cell battery comprising silicon-carbon anode precursor material coated with carbon using a CVD processP-640242-PC(left and right graphs are repeated experiment, the Table below the graphs presents the results and the average results of the experiments).

[0025] Figure 7 - Graphs of half cell formation for batten’ comprising silicon-carbon anode precursor material coated with carbon using a carbon pitch process, (left and right graphs are repeated experiment, the Table below the graphs presents the results and the average results of the experiments).

[0026] Figure 8 - Graphs of half cell formation on batteries made with silicon-carbon anode precursor material, ball milled and coated with carbon CVD Process, (left and right graphs are repeated experiment, the Table below the graphs presents the results and the average results of the experiments).

[0027] Figure 9 - Graphs of full cell formation on batteries made with silicon-carbon anode precursor material, ball milled and coated with carbon CVD Process, (left and right graphs are repeated experiment, the Table below the graphs presents the results and the average results of the experiments)DETAILED DESCRIPTION OF THE INVENTION

[0028] In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.Silicon-carbon Material

[0029] In some embodiments provided herein a silicon-carbon material comprising:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles; (b) graphite particles with silicon nodules; or combination thereof;(c) graphite particles; and(d) silicon particles;wherein more than 95% of particles (a)-(d) have a particle size < 25 pm.

[0030] In other embodiments, the silicon-carbon material comprises:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles; (c) graphite particles; andP-640242-PC(d) silicon particles;wherein more than 95% of particles (a), (c) and (d) have a particle size < 25 pm.

[0031] In other embodiments, the silicon-carbon material comprises:(b) graphite particles with silicon nodules;(c) graphite particles; and(d) silicon particles;wherein more than 95% of particles (b), (c) and (d) have a particle size < 25 pm.

[0032] In other embodiments, the silicon-carbon material comprises:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles and (b) graphite particles with silicon nodules;(c) graphite particles; and(d) silicon particles;wherein more than 95% of the particles within the material have a particle size < 25 pm.

[0033] In some embodiments provided herein a silicon-carbon material comprising:• (a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles; (b) graphite particles with silicon nodules; or combination thereof;• (c) graphite particles; and• (d) silicon particles;wherein more than 95% of particles (a)-(d) have a particle size < 25 pm; and wherein the particles (a)-(d) are further partially or fully coated by at least one layer of carbon film.

[0034] In some embodiments, the particles within the silicon-carbon material provided herein have a particle size smaller or equal (<) to 25 pm. In some embodiments, more than 95% of the graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the particles have a particle size < 25 pm. In some embodiments, more than 95% of the graphite particles with silicon nodules have a particle size < 25 pm. In some embodiments, more than 95% of the graphite particles have a particle size < 25 pm. In some embodiments, more than 95% of the silicon particles have a particle size < 25 pm.P-640242-PC

[0035] In some embodiments, the particles within the material provided herein have a particle size smaller or equal (<) to 25 pm. In other embodiments more than 95% of the particles have a particle size < 25 pm. In other embodiments, 96%, 97%, 98%, 99%, 100% of the particles have a particle size < 25 pm. In other embodiments, more than 95% of the particles have a particle size between 1pm to 25 pm. In other embodiments, more than 95% of the particles have a particle size between 5pm to 25 pm. In other embodiments, more than 95% of the particles have a particle size between 10pm to 25 pm. In other embodiments, more than 95% of the particles have a particle size between 5pm to 20 pm. In other embodiments, more than 95% of the particles have a particle size between 5 pm to 15 pm. In other embodiments, more than 95% of the particles have a particle size between 20 pm to 25 pm. In other embodiments, more than 95% of the particles have a particle size between 15 pm to 20 pm.

[0036] The term “particle size” refers to the diameter of the particle.

[0037] In some embodiments, the silicon-carbon material provided herein comprises graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles. In other embodiments, the thickness of the silicon film disposed on at least a portion of, or fully covering the surface of the graphite particles is between 10-100 nm. In other embodiments, the thickness of the silicon film is between 10-50 nm, between 50-100 nm, between 30-100 nm, between 30-70 nm. In some embodiments, the graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles (a) and the graphite particles with silicon nodules (b) are obtained by chemical vapor deposition (CVD) of a silicon precursor gas and hydrogen on graphite powder.

[0038] In some embodiments, the silicon-carbon material provided herein comprises graphite particles with silicon nodules. “Silicon modules” are analogous to a skin tag, they grow on the surface and appear as rounded mounds. There is no interfacial mixing observed at the interface of the graphite and silicon nodule - this is evidenced by the TEM in Figure 1 showing a morphology that can be described as round silicon nodules dispersed on graphite particles along with thin (nm) silicon films formed on the surface of the graphite particles. In some embodiments, the silicon nodules are round shaped nodules. In some embodiments, the silicon nodules are approximately round shaped nodules. The size of the silicon nodules is estimated in a range between 65 nm to 400 nm. Table 1 discloses the range silicon weight fraction and range of silicon nodule particle size measured on typical product samples. The TEM image shows that little if any amount of the silicon deposited on the graphite particles by CVD penetrates into the graphite particle bulk. From TEM data, the interface is typically < 10 nm.P-640242-PC

[0039] In some embodiments, the silicon-carbon material provided herein comprises graphite particles with silicon nodules. In another embodiment, the silicon nodules size is between 65 to 400 nm. In another embodiment, the silicon nodules size is between 100 and 400 nm. In another embodiment, the silicon nodules size is between 200 and 400 nm, 300 and 400 nm or 65 and 200 nm.

[0040] In some embodiments, the silicon-carbon material provided herein comprises graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles. In another embodiment, the graphite particle’s surface is coated by silicon film. The partial deposition of, or the at least portion of silicon film onthe graphite particle’s surface refers to a graphite particle that may have no detectable silicon on part of the particle’s surface and another part of the particle’s surface has detectable silicon. In another embodiment, the graphite particle's surface is fully coated by silicon film. In another embodiment, the graphite particle’s surface is partially coated by silicon film.

[0041] In some embodiments the silicon-carbon material provided herein comprises:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles: (b) graphite particles with silicon nodules; or combination thereof;(c) graphite particles; and(d) silicon particles;wherein the particles are further coated / encapsulated with at least one layer of carbon film. In another embodiment, the particles (a)-(d) are further partially or fully coated with at least one layer of carbon film. In another embodiment, each of particles (a)-(d) are further coated with one, two, up to three layers of carbon film. In another embodiment the carbon source comprises petroleum pitch, or an unsaturated hydrocarbon gas (e.g. ethylene gas, acetylene). In another embodiment, the silicon-carbon material is coated / encapsulated with carbon by pitch process. In another embodiment, the silicon-carbon material is coated / encapsulated with carbon by CVD process of ethylene gas. In another embodiment, the thickness a layer of carbon coating is between 0.3-20 nm. In another embodiment, the coating includes one to five layers. In another embodiment, the coating includes one to three layers. In some embodiments, 100% of the particles are coated / encapsulated with carbon film. In other embodiments 20-100% of the particles are coated / encapsulated with carbon film. In other embodiments 20-70% of the particles are coated / encapsulated with carbon film. In other embodiments 20-80% of the particles are coated / encapsulated with carbon film. In other embodiments 20-50% of theP-640242-PCparticles are coated / encapsulated with carbon film. In other embodiments 50-100% of the particles are coated / encapsulated with carbon film. In other embodiments 70-100% of the particles are coated / encapsulated with carbon film. In other embodiments 80-100% of the particles are coated / encapsulated with carbon film.

[0042] In some embodiments, the silicon-carbon material is further doped with a dopant gas comprising phosphine, phosphine trichloride, trimethyl phosphine, diborane, boron trichloride, trimethyl boron, arsine, arsine trichloride, germane, germanium tetrachloride, or any combination thereof. In another embodiment, the doping is done by applying gas and hydrogen to the silicon-carbon material mixture.

[0043] The dopant gases are used to change the electrical properties of the graphite and deposited silicon. Typical dopant gases include phosphine, phosphine trichloride, trimethyl phosphine, diborane, boron trichloride, trimethyl boron, arsine, arsine trichloride, germane, germanium tetrachloride, or any combination thereof.

[0044] In some embodiments, the silicon-carbon material comprises herein possess a BET surface area of <7 m2 / g and a tap density of >0.85 g / cm3. In some embodiments, the siliconcarbon material comprises herein possess a BET surface area of 2-7 m2 / g and a tap density’ of 0.85-2 g / cm3.

[0045] The term “silicon-carbon material” provided herein is used interchangeably as siliconcarbon amalgam precursor, silicon-carbon amalgam or as silicon-carbon anode precursor. In another embodiment, the silicon-carbon material is a powder.Process of preparing the silicon-carbon material provided herein

[0046] The silicon-carbon material provided herein can be used for the preparation of an anode of a lithium-ion battery. The process of preparing the silicon-carbon material is easily scalable to high volume manufacturing at low cost due to use of only common CVD processes, annealing processes and ball milling - the process does not use expensive wet chemistries / processes, and generates minimum waste. The anodes made with the siliconcarbon material exhibit unexpectedly low consumption of lithium during initial charge cycling when tested in full cell batteries.

[0047] The silicon-carbon material provided herein comprises:(a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles;P-640242-PC(b) graphite particles with silicon nodules;(c) graphite particles; and(d) silicon particles.CVD Process:

[0048] The process for preparation of the silicon-carbon material of this invention comprising particles (a)-(d) include chemical vapor deposition process (CVD) and a ball milling step. In the CVD process graphite powder is used wherein the particles of the graphite powder are suspended in a gas stream comprising a silicon precursor gas and hydrogen (this type of CVD process is called a fluid bed process) and subsequently decomposition of the silicon precursor gas by thermal energy. The silicon precursor gas comprises trichlorosilane, dichlorosilane, or silane. The reaction products of this decomposition are primarily the radical Si Ch which is condensed on the surface of the graphite particles as silicon. The silicon deposited on the graphite particles form: 1) a thin film of silicon on the surface of graphite’s particles, and / or 2) a nodules of silicon on the graphite. Due to the random motion of the suspended graphite particles in the fluid bed any graphite particle may have silicon on its surface in either or both of the forms described above ((1) or (2)) or even have no silicon at all.

[0049] Thru control of the process temperature, gas composition and gas flow it is possible to control the amount of silicon deposited on the graphite particles and the silicon morphology. The charge storage capacity of the silicon-carbon material is directly determined by the mass fraction of silicon, the charge capacity of silicon, the mass fraction of graphite and the charge capacity of graphite. The distribution of silicon nodules size and or film area are controlled by various combination of values of the above parameters stated and time duration silicon gas (TCS) is fed to the chamber.

[0050] In another embodiment of this invention a dopant gas is added to the silicon-carbon particles formed in the CVD process. The dopant gas is mixed with the other gases in the CVD process, and dopant atoms incorporate into the silicon and graphite during the formation of the silicon carbon material. Dopant gases are used to change the electrical properties of the graphite and deposited silicon. Typical dopant gases include phosphine, phosphine trichloride, trimethyl phosphine, diborane, boron trichloride, trimethyl boron, arsine, arsine trichloride, germane, germanium tetrachloride, or any combination thereof.P-640242-PC

[0051] By changing the electrical properties of the silicon-carbon material the electrical conduction of the ions in the battery are improved and the charge storage properties of the battery are improved.Ball milling step

[0052] The silicon-carbon powder formed in the CVD process can agglomerate and in order to reduce their size, the silicon-carbon powder is ball milled. During a ball milling process the properties of the agglomerated particles can be undesirably altered. For instance, the milling of the graphite particle surfaces can increase the surface area which can lead to undesired consumption of lithium ions and reduced anode capacity and usable life. Also, during milling the silicon deposits on the graphite particles can be dislodged or broken.

[0053] Surprisingly, it was found that the silicon-carbon particles produced in the CVD process behave differently in a ball mill process compared to pure graphite particles or pure silicon nanoparticles. It is found that during ball milling in addition to the silicon-carbon particles formed in the CVD process, also isolated particles of silicon and isolated particles of graphite are formed. It is unexpectedly discovered that while the measured surface area of the ball milled material is increased during ball milling, the lithium ion conduction and trapping properties of the anode material remain unchanged as evidenced in battery testing: there is no loss of initial charge capacity value that can be attributed to ball milling. This is evidenced in the data presented in Table 1 and Table 2.

[0054] In some embodiments, ball milling the product of the CVD process produced a plurality of particles comprising graphite particles with rounded silicon nodules, along with thin silicon films formed on the surface of the graphite particles, isolated silicon particles, isolated graphite particles.Coating by carbon:

[0055] To improve the performance of the anode and its stability , particles (a)-(d) are coated by carbon film or carbon film layers. The role of the carbon film or film layers is understood as regulating expansion of silicon during charge / discharge cycles and slow or even block reactions between the silicon in the silicon-carbon anode precursor material and the electrolyte used in the battery. Common methods for generating the carbon coating silicon include chemical vapor deposition of carbon by decomposition of an unsaturated hydrocarbon gas (US 6,383,686). Another method to create a carbon coating involves mixing the silicon-carbon anode precursor material with carbon pitch (Journal of Physics: Conference Series 2783 (2024) 012024), then putting the anode material into a furnace, flushing with inert gas or hydrogenP-640242-PCand heating to temperatures in the range 800-1200 C. The typical thickness of the carbon coatings formed by CVD or from carbon pitch is in the range of 0.3-20 nm of a layer.

[0056] In some embodiment, the ball milled product is coated by carbon. For example coated with coal tar pitch or petroleum pitch and annealed to form a carbon coating. Alternatively coating with 2 carbon coatings, first carbon coating by CVD, second carbon coating formed using coal tar pitch or petroleum pitch.

[0057] In some embodiments, additional coating of thin film alloys such as Si-O-C, Si-C, Si-N, or Si-O-N is applied directly to the silicon-carbon material, or to the carbon coated siliconcarbon material. The additional coating is deposited by CVD. Regardless of the ty pe of coating process, the coating thickness is between 1-5 nm.

[0058] In some embodiments provided herein a process for the preparation of the siliconcarbon material, wherein the process comprises:(i) suspending graphite particles in a gas stream comprising hydrogen and silicon precursor gas using a chemical vapor deposition (CVD) process; (ii) ball milling the particles obtained is step (i) to reduce the particle size to < 25um to obtain the material provided herein.

[0059] In other embodiments, the CVD process of step (i) results with deposition of silicon on graphite particles comprising (a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles; (b) graphite particles with silicon nodules; or combination thereof. In another embodiment, the CVD process of step (i) results in an interface between the graphite and silicon, and only few atoms layers of silicon penetrates into the graphite particle bulk.

[0060] In some embodiments, following the ball milling of step (ii), further isolated graphite particles (c) and silicon particles (d) are obtained. In another embodiment, the ball milling step reduces the particles size and does not change the charge capacity or first cycle efficiency relative to material that is not ball milled.

[0061] In some embodiments, the CVD process is fluid bed process.

[0062] In some embodiments, the silicon precursor gas comprises trichlorosilane, dichlorosilane, silane or combination thereof.

[0063] In some embodiments, the median diameter of the graphite particles is between 3 - 20 pm. In another embodiment, the median diameter of the graphite particles is between 3-10 pm. In another embodiment, the median diameter of the graphite particles is between 5-15 pm. In another embodiment, the median diameter of the graphite particles is between 10-20 pm. InP-640242-PCsome embodiments, the surface area range of the graphite is between 1.3-20 m2 / g . In another embodiment, the surface area range of the graphite is between 5-10 m2 / g. In another embodiment, the surface area range of the graphite is between 10-20 m2 / g. In some embodiments, the tap density range of the graphite used is between 1.0-1.2 g / cm3. In some embodiments, the tap density range of the graphite used is between 1.02-1.1 g / cm3. In some embodiments, the tap density7range of the graphite used is between 1.05-1.2 g / cm3. In some embodiments, the tap density7range of the graphite used is between 1.1-1.2 g / cm’.

[0064] In some embodiments, the process provided herein further comprises coating part or all of the surfaces of all the particles ((a)-(d)) by7at least one layer of carbon. In another embodiment, the coating of at least one layer of carbon comprises thermal decomposition of an unsaturated hydrocarbon gas by CVD; or mixing coal tar pitch or petroleum pitch and annealing the mixture to form a at least one layer of carbon coating on the particles ((a)-(d)).

[0065] In some embodiments, the gas stream of step (i) further comprises a dopant gas. In another embodiments, the dopant gas comprises phosphine, phosphine trichloride, trimethyl phosphine, diborane, boron trichloride, trimethyl boron, arsine, arsine trichloride, germane, germanium tetrachloride, or any combination thereof.

[0066] In some embodiments, provided herein a silicon-carbon material comprising:• (a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles; (b) graphite particles with silicon nodules; or combination thereof;• (c) graphite particles; and• (d) silicon particles;wherein more than 95% of particles (a)-(d) have a particle size <25 pm; wherein the silicon-carbon material is prepared by the process provided herein.An anode and full cell lithium battery comprising the silicon-carbon material provided herein

[0067] A battery consists of an anode and a cathode and an electrolyte. In a lithium battery the electrolyte comprise of lithium ions. Historically anodes are fabricated with graphite powder which acts as the active material (a storage location for charged ions), a binder, and optionally powders which act to improve the electrical properties of the anode (commonly known as conductive additives). Provided herein a precursor material (=the silicon-carbon material) useful in the fabrication of an anode used in a lithium-ion battery.P-640242-PC

[0068] The lithium battery' anode provided herein is prepared by making a slurry comprising the active material (the silicon-carbon material described herein), conductive additives (e.g. carbon black), and a binder (e.g. LiPAA), all are combined using a high shear mixer. This material is then coated onto a thin metallic foil such as aluminum or copper using methods such as slot die coating or draw down coating.

[0069] In general, if the active material has large particles or agglomerated particles whose size is comparable to or larger than the target thickness of the anode coating, it is possible defects will be formed in the coating leading to poor battery performance. The active material provided herein (the silicon-carbon material) has particles with a diameter < 25pm providing improved battery performance.

[0070] In some embodiments, provided herein an anode for lithium-ion battery, wherein the anode comprises the silicon-carbon material of this invention. In another embodiment, the anode comprises the silicon-carbon material provided herein, a binder, a conductive material such as carbon black. In some embodiments, the anode comprises about 85 wt% the active material (the silicon-carbon material), 5 wt% of carbon black 45 and 10 wt% of Li-PAA binder.

[0071] In some embodiments, the anode exhibits charge capacity range of 700 mAh / gto 1500 mAh / g as measured in a half cell lithium battery. In another embodiment, the anode exhibits charge capacity' range of 700 mAh / g to 1000 mAh / g as measured in a half cell lithium battery. In another embodiment, the anode exhibits charge capacity range of 800 mAh / g to 1000 mAh / g as measured in a half cell lithium battery’.

[0072] In some embodiments provided herein a full cell lithium battery' comprising the anode provided herein, an electrolyte and a cathode. In another embodiment, the full cell lithium battery exhibits a first cycle efficiency of >87%.EXAMPLESExample 1Preparation of Silicon -Carbon Material Prepared By Chemical Vapor Deposition (CVD)

[0073] A CVD fluid bed system was loaded with 500 to 1000 grams of graphite particles comprising the properties.P-640242-PC• Median diameter of graphite particles: 3 - 20 um• Specific surface area range of graphite used in CVD: 1.3-20 m2 / g• Tap density range of graphite used in CVD 1.02-1.20 g / cm3• Graphite particle material tested in half cell lithium batteries to have a specific capacity range of - 350-390 mA / g.

[0074] The CVD reactor used is of cylindrical cross-sectional area ranging 220 to 820 cm2. a height of 2.1 meters and was oriented vertically with reference to its axis of symmetry. Once loaded the reactor was sealed and purged with N2 for a time sufficient to reduce the concentration oxygen containing gases to <0.1%. Next the reactor was purged with hydrogen to reduce the concentration of N2 to <0.1%. The hydrogen flow was adjusted in the range of 30-50 slm to stir and levitate the graphite particles. The reactor was heated to temperature ranging 750-850 C in the CVD reaction zone as measured by a thermocouple hanging in the chamber. A doping gas can be optionally mixed with the hydrogen gas to incorporate phosphorus or boron atoms into the graphite and silicon particles.

[0075] Silicon was deposited by CVD on the graphite particles using trichlorosilane (TCS) gas as the silicon source. TCS was introduced into the reactor using a heated bubbler arrangement with H2 as the carrier gas. A dopant gas can also be added at this time. The TCS was delivered to the chamber at a rate ranging 40 to 65 g / min based on the temperature of the TCS cylinder and H2 carrier gas flow. The process duration was set so as the total TCS delivered during process was in the range of 4.0-6.5 kg.

[0076] The process pressure was slightly higher than atmospheric pressure, approximately 0.1-0.4 psig. The process was operated for enough time to pass 3000-6000 g of TCS through the chamber.

[0077] Once the target time was elapsed, the flow of TCS and doping gas was terminated while the hydrogen flow was maintained to reduce the concentration of TCS and doping gas to less than 0.1% by volume.

[0078] A silicon-carbon material was obtained being a silicon-carbon anode precursor. The material was removed from the CVD chamber. Uniform samples of the product were extracted from the parent product using a Retsch GmbH PT 2000 Sample Divider. Material was tested by powder x-ray diffraction to determine the silicon content and imaged in an electron microscope to assess the morphology. An EDS system in the electron microscope was also used to assess the elemental composition of the sample.P-640242-PC

[0079] Figure 4 is a graph plotting the silicon weight percentage on the x axis as determined by XRD analysis (Rietveld approach) and the measured half-cell battery charge capacity on the y axis. The high linearity indicates that the capacity of the battery is uniquely determined by the weight percentages of the graphite and CVD silicon and their respective charge capacities.

[0080] Following CVD, graphite and the silicon-carbon material was analyzed using BET to assess specific surface area, the BET surface area measurements were made on approximately 2 g of powder under krypton gas flow. The BET analysis was performed in accordance with ISO 9277 standard. Tap density measurements were also made on the material in accordance with ASTM method B527-22.

[0081] The silicon-carbon material sampled from the riffler was then sieved to determine the fraction of particles >25 pm. The particles were separated by size using an ultrasonic sieving system. If the fraction of particles >25 pm was greater than about 3% by weight, the entire output of the CVD process was collected and milled using a roller ball mill with zirconia balls to reduce the maximum particle size of the product to less than 25 pm. The silicon-carbon material was placed in a glass jar with the milling media which was YSZ balls, 2 -mm and 5-mm diameters (80 / 20 mass ratio), Charge ratio: 1:30, roll speed: 190 rpm and the duration was 30 minutes.

[0082] The ball milled product was examined using an electron microscope. The siliconcarbon material typical measured BET surface area was of 2.5 m2 / g, and after ball milling for 30 minutes the measured BET surface area increased to 6.3 m2 / g.

[0083] Figure 2 shows image of the ball milled silicon-carbon anode precursor product. The key feature in this image is distinguished by a morphology that can be described as comprising round silicon nodules on graphite particles along with thin silicon fdms formed on the surface of the same graphite particles, isolated silicon particles, isolated graphite particles, graphite particles with a thin film of silicon. Table 1 displays the range of specific surface area, the range of silicon weight fraction measured on typical CVD product samples, without carbon coating, before and after the milling process, as well as the range of tap density. At this point the material can be optionally coated with carbon using a pitch process. Petroleum pitch is mixed with the product of the CVD process at a concentration of 3-10% by mass. The mixture is placed in a furnace and inert gas flow (for example, nitrogen or argon) is initiated to purge the chamber of air and moisture, and then the chamber is heated to 1000-1200 C for 1 -3 hours. At this point the heat source for the chamber is terminated and the furnace allowed to cool under inert gas to room temperature. (See Example 2B).P-640242-PCTable 1

[0084] Charge storage properties of the silicon-carbon material were evaluated using half cell and full cell lithium batteries fabricated in CR 2032 coin cells. Half Cell lithium batteries with pure graphite anodes or anodes made using the silicon-carbon anode precursor material (=silicon-carbon material) were fabricated as explained in Example 3.Example 2ACoating the Silicon-Carbon Material with Carbon

[0085] The Silicon-Carbon material obtained by method described in Example 1 was coated by carbon by CVD. A gas such as ethylene was introduced into the chamber to deposit a layer of carbon on the particles at a temperature in the range 800-1100 C. As an example, the flow of ethylene was in the range of 30-50% of the total flow and the time for carbon deposition could range 5-30 minutes at 900 C. After completion of the carbon coating step the flow of ethylene was terminated, and the chamber temperature cooled to <600 C while maintaining a flow of hydrogen. When the temperature dropped below 600 C the hydrogen gas flow was terminated, and nitrogen gas was introduced with the same gas flow as was used for hydrogen.P-640242-PCThe heat source was turned off and the chamber was allowed to cool to room temperature. At this point the nitrogen flow was terminated, and the material was unloaded from the chamber.Example 2BCoating the Silicon-Carbon Material with Carbon

[0086] The Silicon-Carbon material obtained by method described in Example 1 was coated with carbon fdm using petroleum pitch as a precursor. The petroleum pitch was mixed at a concentration of 3% by mass with the silicon-carbon material. The mixture was placed in a furnace and inert gas flow of 1 slm (for example, nitrogen or argon) was initiated to purge the chamber of air and moisture to less than 1% of the starting value, and then the chamber was heated to 1050 C and held for for 1 hour. At this point the heat source for the chamber was terminated and the furnace allowed to cool under inert gas to room temperature.Example 3Batery Anode Comprising Silicon-Carbon Material and Evaluation

[0087] Battery anodes were made from a slurry consisting of 85 wt% the active material (pure graphite or the silicon-carbon material), 5 wt% of carbon black 45 and 10 wt% of lithium polyacrylic acid (Li-PAA) binder. The slurry was applied to a copper sheet by draw down method. The target thickness of the anode coating is in the range 20-60 um depending on the properties of the anode material and full cell battery design. Once dned, the anode was calendared to 75% of its original thickness. Anode disks were stamped from the coated copper foil for use in coin cell fabrication.

[0088] Half cell coin cells were fabricated in a dry box using a lithium foil for the cathode and the anode disk described above. The typical electrolyte used was 1.15 M LiPFe in Ethyl Carbonate / Ethyl methyl carbonate with Diethyl carbonate, Fluoroethylene carbonate, Propylene sulfite & ADN (Methylboronic acid MIDA ester).

[0089] The half-cell test conditions were as follows: Discharge (lithiation): C / 10 to 0.01 V and voltage hold @ 0.01 V until current density <C / 20; Charge (de-lithiation): C / 10 to 1.5 V. Cycle testing was performed, first discharge: CC (0.3C) to 0.01V, then CV until current density < 0.05C then charge: CC (0.3C ) to 1.0V.

[0090] Figures 3A-3B show results of the first several discharge / charge cycles of the half cell batteries made with Figure 3A: the graphite used in the CVD process and Figure 3B: the halfP-640242-PCcell bateries made with the silicon-carbon material. Comparing Figure 3A and 3B it shows that the application of the silicon CVD process to the graphite powder increased the batery capacity by >450 mAh / g.

[0091] From the type of data presented in Figures 3A-3B, the first cycle efficiency, FCE (also referred to as ICL or Initial Coulombic Loss, ICL%=100-FCE%) is determined.

[0092] Table 2 lists the first cycle efficiency typical of the half cell batteries tested, these results range 89%<FCE<93%.Table 2: The first cycle efficiency / initial coulombic loss typical of the half and full cell bateries with anodes fabricated using only graphite or forms of the silicon carbon anode precursor.P-640242-PC

[0093] For half cell lithium batteries made using silicon carbon based anodes typically reported in the prior art, the values of FCE / ICL measured using half cell bateries range from 74% to 82%. As shown above the FCE values in Table 2 for half cells are higher than 82%.Example 4Full Cell Comprising Silicon-Carbon Material

[0094] Full cell coin cell batery testing was performed using the same anode fabrication process previously described for half-cell batery testing. In some examples the silicon carbon amalgam anode precursor was fabricated with the addition of carbon coating of the anode material after then CVD process. A full cell coin cell was fabricated comprising a cathode material NCM532 and the fabricated anode material as previously described.

[0095] The full cell test conditions were first formation using discharge: CC (0.1C) to 2.5V, then CV until current density < 0.05C then charge: CC (0.1C ) to 4.2V. Cycle testing was performed first discharge: CC (0.3C) to 2.5V, then CV until current density < 0.05C, then charge: CC (0.3C ) to 4.2V

[0096] From the data presented in Figures 6, 7, and 9, the first cycle efficiency, FCE (also referred to as ICL or Initial Coulombic Loss, ICL%=100-FCE%) is determined. Table 2 lists the first cycle efficiency typical of the full cell bateries tested, the results are as high as 87%. For lithium full cell bateries made using silicon anodes typically reported in the prior art, the values of FCE measured using full cell batteries range from 71% to 88%. The FCE values in Table 2 are unique to the invention of this anode material and material fabrication process.

[0097] Figure 5 shows the results of the first several discharge / charge cycles of half-cell formation for a batery comprising silicon-carbon anode precursor material which was coated after the CVD anode process with an additional carbon coating formed using a CVD process based on ethylene as described in Example 2A and 2B.P-640242-PC

[0098] Figure 6 shows the results of the first several discharge / charge cycles of full cell formation for a battery comprising silicon-carbon anode precursor material which was coated after the CVD anode process with an additional carbon coating formed using a CVD process based on ethylene.

[0099] Figure 7 shows the results of the first several discharge / charge cycles of full cell formation for batteries V259, battery comprising silicon-carbon anode precursor material which was coated after the CVD anode process with an additional carbon coating formed from carbon pitch.

[0100] Figure 8 shows the results of the first several discharge / charge cycles of half cell formation samples for a battery comprising silicon-carbon anode precursor material, ball milled and coated with carbon CVD Process based on ethylene.

[0101] Figure 9 shows the results of the first several discharge / charge cycles of full cell formation samples for battery comprising silicon-carbon anode precursor material, ball milled and coated with carbon CVD process based on ethylene.

[0102] Table 3 summarizes data first cycle efficiency (FCE) in half and full cell lithium batteries comprising anodes containing silicon and graphite taken from published prior art and the examples provided herein.

[0103] Table 3: Examples of first cycle efficiency (FCE) in full cell lithium batteries made with anodes containing silicon and graphite"P-640242-PC

[0104] From Table 3 it is concluded that the silicon carbon material, in many different forms (CVD / Milled / carbon coated) consistently produces half cell and full cell batteries with very high first cycle efficiency values.

Claims

P-640242-PCCLAIMSWhat is claimed is:

1. A silicon-carbon material comprising:• (a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles:• (b) graphite particles with silicon nodules; or combination thereof; • (c) graphite particles; and• (d) silicon particles;wherein more than 95% of particles (a)-(d) have a particle size < 25 um.

2. The silicon-carbon material of claim 1, wherein more than 95% of the graphite particles with thin film of silicon on the surface of the graphite particles (a) have a particle size of < 25 um.

3. The silicon-carbon material of claim 1 or claim 2, wherein the thickness of the silicon film on the graphite’s surface is between 10-100 nm.

4. The silicon-carbon material of claim 1, wherein the thin film of silicon is deposited partially or fully on the graphite particle’s surface.

5. The silicon-carbon material of claim 1, wherein the silicon nodules size is between 65 - 400 nm.

6. The silicon-carbon material of claim 1, wherein more than 95% of the graphite particles with silicon nodules (b) have a particle size of < 25 pm.

7. The silicon-carbon material of claim 1, wherein more than 95% of the graphite particles (c) have a particle size of < 25 pm.

8. The silicon-carbon material of claim 1, wherein more than 95% of the silicon particles (d) have a particle size of < 25 pm.

9. The silicon-carbon material of any one of claims 1-8, wherein the each of particles (a) -(d) are further partially or fully coated with at least one layer of carbon film.

10. The silicon-carbon material of claim 1, wherein the graphite particles with thin film of silicon on the graphite particle’s surface and the graphite particles with silicon nodules are obtained by chemical vapor deposition (CVD) of a silicon precursor gas and hydrogen on graphite powder.P-640242-PC11. The silicon-carbon material of any one of claims 1-10, wherein the BET surface area of the silicon-carbon material is <7 m2 / g and the tap density is > 0.85 g / cm212. An anode for lithium-ion battery comprising the silicon-carbon material of any one of claims 1-11.

13. The anode of claim 12, wherein the anode exhibits charge capacity between 700 mAh / g to more than 1000 mAh / g as measured in a half cell lithium battery7.

14. A lithium-ion battery comprising the anode of claim 13. an electrolyte and a cathode.

15. The lithium-ion battery of claim 16, wherein its first cycle efficiency is >87%.

16. A process for the preparation of the silicon-carbon material of any one of claims 1-11, wherein the process comprises:(i) suspending graphite particles in a gas stream comprising hydrogen and silicon precursor gas using a chemical vapor deposition (CVD) process; (ii) ball milling the particles obtained is step (i) to reduce the particle size to < 25 pm to obtain the silicon-carbon material of claim 1.

17. The process of claim 16, CVD process of step (i) results with (a) graphite particles with thin film of silicon on the graphite particle’s surface; (b) graphite particles with silicon nodules; or combination thereof.

18. The process of claim 16, wherein following the ball milling of step (ii), further isolated graphite particles (c) and silicon particles (d) are obtained.

19. The process of claim 16, wherein the CVD process is fluid bed process.

20. The process of claim 16, wherein the silicon precursor gas comprises trichlorosilane, dichlorosilane, silane or combination thereof.

21. The process of claim 16, wherein the process further comprises coating part or all of the surfaces of all the particles ((a)-(d)) by at least one layer of carbon.

22. The process of claim 21, wherein the coating of at least one layer of carbon comprises thermal decomposition of an unsaturated hydrocarbon gas by CVD; or mixing coal tar pitch or petroleum pitch and annealing the mixture to form a at least one layer of carbon coating on the particles ((a)-(d)).

23. The process of any one of claims 16-22, wherein the ball milling step reduces the particles size and does not change the charge capacity or first cycle efficiency relative to material that is not ball milled.P-640242-PC24. The process of any one of claims 16-23, wherein the CVD process of step (i) results in an interface between the graphite and silicon, and only few atoms layers of silicon penetrates into the graphite particle bulk.

25. The process of any one of claims 16-24, wherein the gas stream of step (i) further comprises a dopant gas.

26. The process of claim 25, wherein the dopant gas comprises phosphine, phosphine trichloride, trimethyl phosphine, diborane, boron trichloride, trimethyl boron, arsine, arsine trichloride, germane, germanium tetrachloride, or any combination thereof.

27. A silicon-carbon material comprising:• (a) graphite particles with thin film of silicon disposed on at least a portion of, or fully covering the surface of the graphite particles:• (b) graphite particles with silicon nodules; or combination thereof; • (c) graphite particles; and• (d) silicon particles;wherein more than 95% of particles (a)-(d) have a particle size <25 pm; wherein the silicon-carbon material is prepared by the process of any one of claims 16-26.

Images