Electrode particles suitable for batteries

Abstract

To provide a method for forming a graphite anode material that achieves higher performance at lower cost.SOLUTION: A method for forming a graphite anode material for metal ion batteries, comprises: selecting and sizing a carbon precursor material into particles having a desired average particle size; combining the precursor material with a carbide-forming element at a ratio between 0.01% and 10% of the blend; graphitizing the combination at a temperature between about 2500°C and 3000°C in argon, helium or nitrogen gas to yield particles having a carbide compound on the surface and having a graphite core. The carbide compound comprises carbide-forming elements consisting of B and Ce.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Relationship with Related Applications This is a PCT international patent application claiming the benefit and priority of U.S. Provisional Patent Application Nos. 62 / 875,299 and 62 / 875,315, both filed on July 17, 2019, and U.S. Patent Application Nos. 16 / 929,222, 16 / 929,233, and 16 / 929,248, all filed on July 15, 2020, under the title "ELECTRODE PARTICLES SUITABLE FOR BATTERIES", which are hereby incorporated in their entirety by reference.

[0002] Field of the Invention This application relates to batteries, and more particularly to materials useful for making anodes for batteries, and more particularly to materials useful for anodes of metal ion batteries.

Background Art

[0003] Background of the Invention Rechargeable lithium-ion batteries have been widely introduced into many portable systems and devices such as mobile phones, tablets, computers, portable handheld tools, and new devices developed to rely on the power and weight advantages of lithium-ion batteries. These advantages are lightweight, high voltage, high electrochemical equivalence, and good conductivity. The wide use and acceptance of lithium-ion batteries have achieved many advancements and developments. One area of development of lithium-ion batteries has focused on the anode, i.e., the negative electrode, of the lithium-ion battery, where much has been achieved.

[0004] For portable devices in particular, important considerations regarding lithium-ion battery anodes are high volumetric and weight-specific capacity, and long battery life over numerous charge and discharge cycles. In previous studies, anode materials were coated, and anode materials with initial clonal efficiency reaching 95% were produced via graphitized carbon precursor materials. This was done by Mao et al. As described in Patent Document 1 to al., petroleum coke is ground to a suitable size, subjected to a solvent coating process, and has a coating that is oxidatively stabilized at high temperature, then the entire particle is carbonized and graphitized at a higher temperature in an inert environment. The particles form a highly graphitized structure with a protective coating on the surface, which protects the underlying graphite sheet from the battery electrolyte. The protective coating protects the edges of the graphite sheet, which are thought to be catalytically active to the battery electrolyte. The electrolyte thus decomposes the graphite sheet during the charging cycle, thereby rapidly and dramatically reducing the efficiency and storage capacity for lithium ions in the anode. The coating created on the anode particles, when graphitized with the remaining particles, forms graphite that is more stable with respect to catalytic decomposition from the electrolyte, but it contains material that is not so graphitized itself and is not suitable for lithium ion intercalation. However, lithium ions can easily pass through the coating and intercalate into a more organized graphite sheet. In fact, this is a very good material with good properties and good cycle life. However, its production requires the use of a considerable volume of solvent, involving numerous separate, continuous heat treatments in different ambient environments, all of which are costly. Nevertheless, for high-value applications where small space and minimal weight are crucial and high specific volume is important, this anode is currently the most advantageous.

[0005] The most important parameter of the graphite anode material in lithium-ion batteries is the initial clonal efficiency and This relates to specific capacity. It is well known that highly crystalline graphite powder has a high specific capacity and very poor initial cloning efficiency, and is therefore unsuitable as anode material for lithium-ion batteries. Through years of thorough research and development, sophisticated methods have been developed to mitigate the problems related to specific capacity and initial cloning efficiency. The main solution focuses on high-temperature graphitization and coating particles containing carbon that is not easily graphitized, followed by graphitization to provide protection for the graphite sheet inherent in the particles from the electrolyte. Since the mean average particle size of graphite anode material is less than 30 microns, and each particle must be uniformly coated with carbon that is not easily graphitized, graphite anode material is now manufactured through complex processing steps. As a result, manufacturing costs are high, and some of the coating processes have low yields.

[0006] For all materials, there is always a desire (driver) for higher performance at a lower cost, and any progress in either performance or cost is highly desirable. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 7,323,120 [Overview of the Initiative]

[0008] The present invention relates to graphite-carbon powder comprising particles having an average particle size between 1 μm and 50 μm, wherein the particles have a modified surface comprising a carbide compound constituting at least 5 ppm and 1% by weight of the particles, and contain at least 90% by weight of carbon graphite. [Brief explanation of the drawing]

[0009] A more complete understanding of the present invention and its benefits can be obtained by referring to the following description in conjunction with the attached drawings. [Figure 1] This is a schematic diagram of a battery cell in a hypothetical circuit showing the anode, cathode, electrolyte, and circuitry. [Modes for carrying out the invention]

[0010] We will now move on to a detailed description of one or more preferred configurations of the present invention, but it should be understood that the features and concepts of the present invention can be realized in other configurations, and that the scope of the present invention is not limited to the embodiments described or explained. The scope of the present invention is limited only by the claims that follow.

[0011] First, we move to Figure 1, where arrow 10 indicates a schematic cell. The cell contains numerous particles of cathode material 20 and numerous particles of anode material on the opposite side of the electrolyte separator 40. Each particle of cathode 20 and anode 30 is held to its respective metal electrode in an electrically conductive paste (not specifically shown). An electrical load, such as a light or electric motor, shown at 50, can be connected to the cell 10 by wiring shown at 51. When the cell 10 is charged, positive ions are stored in the anode particles 30. Due to the electrochemical properties of the cathode and anode materials, positive ions are driven (attracted and repelled) to move from the anode 30 through the electrolyte separator 40 to the cathode. While the ions are moving through the electrolyte, electrons pass around the metal electrode 31 and then move to the cathode through wire 51 and the load 50 to balance the charge. The process of electrons passing through the load causes electrical work, such as lighting a light bulb or turning an electric motor. In lithium-ion batteries, the cathode is generally formed with a chemical structure containing lithium, which moves across the separator 40 and intercalates into the anode, forming lithium ions during battery charging. The anode material has chemical complexity. Low-cost, high-performance anode materials can densely store lithium ions in a manner that allows them to be easily released without permanently binding to the anode and returned completely to the cathode. This invention focuses on the configuration of anode materials used in batteries as shown in Figure 1.

[0012] Carbon-clad anode materials have demonstrated very attractive properties for high-value batteries where light weight and small size are critical, but conversely, they have less use in batteries where weight and size are not critical. Such lower-value applications include power storage devices in fixed locations that require very high power capacity, such as standby power in switchboards.

[0013] Turning to batteries that meet such needs, research has been conducted to develop battery designs that use larger volumes of uncoated graphitized petroleum coke material to compensate for the expected degradation of anode performance over numerous charge and discharge cycles. In the process of exploring the optimal graphitization level for batteries, several graphite nucleating agents were added to accelerate the formation of graphite structures at low temperatures. However, the final result was a somewhat high-performance anode material, and further development research was quickly directed towards elucidating the properties of the new anode product and why it performed at a higher level than expected.

[0014] What is thought to have occurred in these tests is that, rather than nucleating graphite formation, the nucleating agent reacted with the carbon surface of the particles to form carbide compounds, or reacted with nitrogen gas to form nitride compounds on the particle surface. The carbide and nitride compounds do not appear to form deep within the particles, thereby protecting the bulk particles as crystalline graphite for ion intercalation. The carbides and nitrides clearly protect the graphite structure from the electrolyte in the metal-ion battery, thereby preventing the electrolyte from interacting with the graphite. It is generally known that the electrolyte decomposes graphite at the anode, and furthermore, this thin thickness of the modified surface protected the graphite sheet in this invention.

[0015] The initial experiments began with boron as the nucleating agent. Graphitization is generally carried out under a non-oxygen blanket gas, as it must occur in a non-oxygen environment or through combustion where carbon, in principle, forms carbon dioxide. Under a nitrogen blanket gas, nitrides also form on the surface. However, some nucleating agents may boil and not remain on the surface in nitride form. Stable nitrides and / or carbides appear to form most readily when the graphitization temperature is above the melting point of the stable carbide or nitride molecules but below their boiling point. For nucleating agents that form stable nitrides that boil below the graphitization temperature, other inert blanket gases can be selected. Argon has been successfully used in those situations. See Table 1, which shows the most promising nucleating agents for each of the carbides and nitrides that can be formed during graphitization. See Table 2, which shows the clonal efficiency and specific capacity for each cell created using boron as the carbide or nitride forming agent. [Table 1]

[0016] Carbide and nitride-forming materials are blended with powdered coke in amounts ranging from about 0.1% to about 5% by weight. Carbides and nitrides are thought to form on the surface of the particles when the intrinsic carbon forms a graphite structure within them. That is, the method of the present invention for producing anode powder involves preparing a graphite precursor to a desired size by milling or other means, adding an appropriate amount of carbide or nitride-forming elements by blending them together, and then subjecting the blended mixture to a graphite formation temperature for a sufficient amount of time to form the surface chemistry and the intrinsic graphite structure. In some coke materials, it is preferable to carbonize them in order to remove heteroatoms and other non-oxygen atoms (drive off) before graphitization by calcination. Carbonization is generally a heat treatment below the graphite temperature, but sufficiently high, such as between 900°C and 1500°C, and generally raising the carbon content of the coke in the calcination furnace to at least 92%, such as 95%, or at least 97%.

[0017] Preferably, the particle surface is continuous with either carbides or a mixture of carbides and nitrides, and there is no graphite exposed to the electrolyte. Furthermore, the particle surface is preferably as smooth as possible compared to rough or jagged surfaces. Most graphite materials have jagged surfaces where the graphite sheet tends to break more when the particles separate. A smooth surface is thought to be more resistant to electrolyte attack on the bulk graphite structure, which has been achieved conventionally by coating. The carbide surface is a modified surface with a thickness of several atoms, from a few nanometers thick, to a selected carbide-forming compound (if The thickness can be greater depending on the selected compound(s), but the jagged surface will not be modified into a more desirable smooth surface. The content of such carbide-forming surfaces or elements in the graphitized powder can range from about 50 ppm to about 5000 ppm, also depending on the selected compound(s).

[0018] The type of coke and carbide-forming compound has also been found to play an important role in the formation of the desired graphite anode material. The selected coke is preferably calcined, or at least partially calcined, at a temperature between 500 and 2000°C before graphitization. Untreated coke, especially that containing highly volatile substances, can react with the selected carbide-forming compound to form volatile compounds, resulting in the evaporation of such elements before the formation of suitable carbides at the graphitization temperature. On the other hand, coke that is calcined or graphitized at temperatures above 2000°C is more chemically stable and does not chemically react with the selected carbide-forming compound, such as salts and oxides, resulting in the evaporation of such added salts or oxides during the temperature increase to graphitization.

[0019] The atmosphere in which a mixture of coke and carbide-forming compounds is graphitized is a factor in selecting such carbide-forming compounds. Non-oxidizing gases such as argon, helium, and nitrogen are suitable for graphitization. However, in the case of a nitrogen gas atmosphere, some carbide-forming elements may react with nitrogen to form undesirable nitride compounds, particularly volatile nitride compounds that dilute or reduce the carbide content. Thus, the selection of carbide-forming compounds is limited to elements that form carbides and / or nitrides at high temperatures. For graphitization in argon or other non-reactive gases, suitable carbide-forming elements form carbides that are stable at temperatures above 2000 °C. In other words, the best results occur when the melting point of the carbide formed is higher than 2500 °C and preferably higher than 2700 °C.

[0020] Furthermore, the form of this anode material is not coated with a graphitization precursor (or a carbon layer different from the bulk). The present invention modifies the existing surface to have carbide compounds or carbide and nitride compounds formed on the surface that protect the core of the particles through many charge and discharge cycles. Thus, there is no high degree of graphitization crystallinity at the surface that chemically reacts with the electrolyte, and the nitride or carbide or both on the surface substantially reduces or eliminates the degradation of the bulk graphite material, thereby reducing one mode of battery inactivation.

[0021] This suggests that an anode material comprising coke, regardless of whether it is derived from petroleum or coal tar, can be sized by any number of methods to obtain an average particle size such that most particles are between about 3 microns and up to about 30 microns, and this can then be graphitized to about 3100 °C in an inert atmosphere.

[0022] The measurement of particle size serves many perspectives. In a preferred invention, the particle size can be tailored to the battery application or the specifications of the battery manufacturer. Ideally, the particles are substantially the same size, taking into account the variability of milling, sieving, and other sizing techniques. And the fact that the particles are not spherical adds an additional complexity. Fortunately, it is not necessary for the particle size measurement to be overly complex. Laser diffraction or imaging systems manufactured by Malvern or Horiba that generally use volume-based calculations provide adequate accuracy for the purpose of providing such anode powders for use in lithium-ion batteries. And from these measurements, the average particle size in the useful powder is generally between 1 and 50 microns, and more typically within a narrower range.

[0023] Therefore, the present invention provides a novel graphite electrode material for lithium-ion batteries and also provides a simple method suitable for the manufacture of such electrode materials. In one aspect regarding the graphite anode material, the graphite particles contain metal or non-metal carbide and nitride components on the particle surface, and such carbide or nitride content is between 5 ppm and 1 wt%, preferably between 50 ppm and 2000 ppm, more preferably less than about 1500 ppm, and even more preferably between about 100 ppm and 1000 ppm. The carbides and nitrides may be single elements or mixtures of different elements. The amount blended into the carbon precursor is between about 500 ppm and 10 weight percent, more preferably between 1000 ppm and 3 weight percent. The average particle size of the anode particles is between 3 and 30 microns, and preferably between 3 and 25 microns.

[0024] The process for producing graphite material involves two main steps: grinding a graphitizable carbon precursor to a specific particle size, and then graphitizing the resulting powder with carbide and nitride-forming materials within a specific temperature range. In more detail, the carbon precursor is selected from petroleum and coal tar coke. Untreated coke is preferred. The selected carbon precursor is ground into a powder having an average particle size of less than 30 μm, depending on the requirements of the particular battery, by any mechanical grinding method such as a ball mill, knife mill, impact mill, and jet mill. Typical average particle sizes range from 3 μm to 25 μm. Optionally, the ground powder is carbonized in a non-oxygen environment to remove non-carbon elements. Particle separation is preferred before graphitization, as graphitization makes the particles more brittle, resulting in more jagged and irregularly shaped particles, which are more vulnerable to catalytic decomposition of the graphite sheet structure.

[0025] The milled powder (carbonized or untreated) is combined with carbide and nitride-forming compounds and graphitized at a temperature higher than 2650°C, preferably between 2800°C and 3000°C, in an inert environment such as nitrogen, argon, helium, or a combination thereof. The carbide and nitride-forming compounds can be fibrous metals, nonmetals, rare earth metals, or combinations thereof. The amount of carbide or nitride-forming compound used is between 100 ppm and 10% by weight of the total mass, more preferably between 0.05% and 2% by weight. [Examples]

[0026] Description of the Examples The usefulness of such materials produced is evaluated as a negative electrode material (lithium intercalation) for coin-type batteries containing lithium metal as the counter electrode. The preparation procedure is described below:

[0027] Electrode Preparation - Each electrode was prepared using the following steps: Step 1) Approximately 2 g of graphitized powder, 0.043 g of carbon black, and 0.13 g of polyvinylidene difluoride (PVDF) (in a 10 wt% solution (in N-methylpyrrolidone (NMP))) were placed in a 25 ml plastic vial, and shaken in a mill with approximately 3 g of 1 / 8” steel balls for 10 minutes to form a uniform paste. Additional NMP was added to achieve the desired fluidity of the mixture. Step 2) A thin film of the resulting paste was placed on copper foil or aluminum foil and cut with a doctor blade. Step 3) The film was cast using a coater. The resulting film was dried on a hot plate at 120°C for at least 2 hours. Step 4) The dried film was cut into 5 cm wide pieces and compressed through a roller press. Step 5) Three discs (1.5 cm in diameter) of each film were punched out using a die cutter to be used as electrodes. The electrode weight was measured by subtracting the total weight of each disc from the weight of the disc substrate. The electrode composition was 92 wt% graphite, 6 wt% PVDF, and 2 wt% carbon black, and the mass load was approximately 10 mg / cm2.

[0028] Each coin-type battery was subjected to electrochemical testing. Each coin consisted of a bottom can, lithium metal as the counter electrode, a separator, a disc electrode, a stainless steel disc spacer, a wave spring, and a top can. These components were sequentially placed on the bottom can. After the electrolyte was added to the separator, the disk electrodes were stacked. A 1M LiPF6 electrolyte was used in a mixture of 40% ethylene carbonate, 30% dimethyl carbonate, and 30% diethylene carbonate. After the top can was dropped onto the stack, the assembly was transferred to coin cell compression pliers and then crimped together.

[0029] Electrochemical testing was performed at the electrochemical test station using different charge / discharge test programs for the negative and positive electrode materials, as follows:

[0030] As a negative electrode material for lithium-ion batteries, the following tests were conducted: A) charging to 0.0V with a constant current of -1.0mA, B) further charging at 0.0V for 1 hour, C) discharging at 1mA until the voltage reached 2.0V, and D) repeating steps A through C five times or five cycles. The charge that passed through each cycle during charging and discharging was recorded and used to calculate the specific capacity and clone efficiency. All tests were performed at ambient temperature, and the batteries were tested in a glove box with oxygen and humidity levels below 3 ppm.

[0031] Analysis of carbide and nitride-forming element content After graphitization, the powder was dissolved in an acid solution, and its elemental content was analyzed using standard inductively coupled plasma mass spectrometry. [Examples]

[0032] Example Set 1 Two samples of untreated petroleum coke were obtained from different sources, dried, crushed, and ground to an average particle size of 5 μm. The first sample was from Phillips 66 refinery in Ponk City, Oklahoma, and the second sample was from Phillips 66 refinery No. 2 in Lake Charles, Louisiana. Each powder was blended with 1 wt% and 2 wt% elemental boron (average particle size <1 μm) and compared to a sample of boron-free powder. The mixtures were graphitized in an argon environment at 2900°C and subsequently evaluated as anode materials for lithium-ion batteries. For comparison, these anode powders were graphitized under the same conditions. Table 2 lists the specific discharge capacity and initial clonal efficiency for such graphitized powders. Without boron, the initial clonal efficiency was very low (<40%), and the discharge capacity was also low (-300 mAh / g). Such materials are not suitable for use as anode materials in lithium-ion batteries. When boron is included, graphitized powder exhibits excellent properties as a negative electrode material for lithium-ion batteries (high capacity >350mAh / g and initial cloning efficiency >91%). [Table 2] [Examples]

[0033] Example Set 2 Additional coke sample powder from Coke Sample 1 of Example Set 1 was graphitized with several blends of boron and other carbide and nitride-forming elements. Six examples were prepared, each containing 1.5 wt% of the blend. The blends consisted of three different boron-to-cerium ratios of boron and cerium: 1:10, 10:1, and 1:1. These carbide and nitride-forming compounds were selected from metallic and non-metallic chemicals and graphitized at 2900°C under a nitrogen atmosphere. The graphitized powders were evaluated in the same manner as in Example Set 1. Table 3 lists the discharge specific capacity and initial clonal efficiency for such graphitized powders. Columns 4 and 5 show the elemental content of carbide and nitride-forming elements in the graphitized powder. The first three samples exhibited initial clonal efficiencies higher than 91% and specific capacities greater than 335 mAh / g, demonstrating that high-performance anode graphite powders can be economically produced according to the present invention.

[0034] As can be seen from Table 3 below, at a graphitization temperature of 2900°C, carbide-forming elements create physical differences in the resulting electrodes, which provides a tremendous enhancement to the initial cloning efficiency. Carbide-forming elements have high melting points and appear to either form carbide crystals on the surface carbon or accept (contain) nitride crystals on the surface. Both of these facilitate the passage of ions into and out of the graphite, while simultaneously protecting the graphite from the electrolyte. [Table 3] [Examples]

[0035] Example Set 3 A sample of untreated anode-grade petroleum coke, commonly used in the production of anodes for aluminum smelting, was dried at 100°C, crushed in a roller mill, and then pulverized to an average particle size of 5 μm in a laboratory jet mill. The coke sample had 12 wt percent volatile matter and was divided into six separate samples. The first three samples were blended with boron and cerium at approximately 1.5 wt percent, and the remaining three samples were blended with silicon, manganese, and yttrium at approximately 1.5 wt percent. Each group in a separate small crucible was placed in a larger graphite container and graphitized in an argon gas environment at 2900°C for 15 minutes.

[0036] The graphitized powder was evaluated as an anode material for lithium-ion batteries in coin-type batteries, as described above. The important parameters were specific discharge capacity and initial cloning efficiency, and the results are listed in Table 4. The content of carbide-forming elements in the graphitized samples is listed in Table 9. Graphitized samples with sufficient carbide-forming element content produced excellent initial cloning efficiency (>92%) and specific discharge capacity, while those with undetectable carbide-forming element content showed poor initial cloning efficiency (<60%) and low specific discharge capacity. [Table 4] [Examples]

[0037] Example Set 4 A set of the same mixture as in Example Set 3 was graphitized at a temperature of 2900°C, similarly but in a nitrogen gas environment. The resulting graphitized powder was evaluated in the same manner as in Example Set 3. The specific volume and initial clonal efficiency obtained for these samples are listed in Table 5 below. The measured properties were similar to those of Example Set 3, except for yttrium, which showed reduced performance in initial clonal efficiency. It is thought that the carbide-forming materials also form nitrides with nitrogen gas, which evaporates at temperatures lower than the graphitization temperature, and that the surface treatment does not retain particles, making them unsuitable as anode materials for metal-ion batteries. [Table 5]

[0038] These examples show that the presence of carbide-forming elements causes graphitized powder to form an anodized form in lithium-ion batteries. It exhibits excellent properties as a cloning material, and without such carbide-forming elements, it does not possess desirable properties (low cloning efficiency). [Examples]

[0039] Example Set 5 In Example 5, three grades of untreated petroleum coke were dried at 100°C, crushed in a roller mill, and then ground in a laboratory jet mill to average particle sizes of 5, 8, 11, and 15 μm, respectively. The resulting coke powder was heated in nitrogen gas at 950°C for 2 hours to remove volatile substances. These coke powders are labeled A, B, and C in the examples described below, where A is aluminum anode grade petroleum coke, B is a type of premium petroleum coke used as an anode to produce recycled steel in electric arc furnaces, and C is a lower grade premium petroleum coke with high volatility that has been used as a precursor to produce anodes in metal ion batteries.

[0040] Samples of various coke particles containing 11 μm powder of coke A, 5 and 8 μm powders of coke B, and 15 μm powder of coke C, along with two carbide-forming compounds (the elements boron and cerium oxide), were blended at weight contents of 0.5% and 1.5%. The resulting mixtures were graphitized under the same conditions as in Example 4 and tested as anode materials for lithium-ion batteries. The graphitized samples were labeled A5, B5, B8, and C15 in this example. The test results are listed in Table 6 below. [Table 6]

[0041] Comparative Example Set 1 5 μm powder of coke A and 5 and 8 micrometer powders of coke B were graphitized in a nitrogen gas environment under the same conditions as in Example Set 4, without any carbide-forming elements. The graphitized powders were evaluated as anode materials for lithium-ion batteries, as in the previous examples. These samples were labeled A5, B5, and B8 in this example. The test results are also listed in Table 7 in Comparative Example 1 below. [Table 7]

[0042] Comparative Example Set 2 5 and 8 micrometer powders of coke B were coated with 8 wt% and 6 wt% pitch using the solution-phase precipitation method described in U.S. Patent No. 7,323,120. The pitch coating method involved several steps, which included a) dispersing the coke powder in an organic solvent, b) dissolving the selected pitch in the organic solvent, c) heating both the coke and pitch solutions to a high temperature, d) mixing the two solutions and cooling the mixture under continuous stirring so that a certain heavy portion of the dissolved pitch precipitates on the coke particles as a solid film, e) separating the pitch-coated coke particles from the solution by filtration, f) washing off any remaining pitch solution on the coated coke particles with an additional organic solvent, and finally drying the pitch-coated particles. The pitch-coated powders were further treated by oxidation in air at a high temperature (below 350°C) so that the resulting powders would be non-fusing and the coated pitch would not graphitize more than the core of the bulk coke. This process is generally referred to as stabilization. After pitch coating and stabilization, the powders were graphitized under the same conditions as in Example Set 4. The graphitized powder was evaluated as an anode material for lithium-ion batteries in the same manner as described above, and the results are shown in Table 8 below Comparative Example 2. [Table 8]

[0043] Sample sets 3 and 4 were subjected to analytical testing to measure their components after graphitization. Table 9 shows the amounts of carbide and nitride-forming elements in the anode material after testing. Due to their inherently low levels and the limitations of our in-house testing equipment, not all samples could be measured. [Table 9]

[0044] In sample set 5, anode samples were prepared by graphitizing 8 μm premium coke in nitrogen gas at 2900°C, followed by 15 minutes in a nitrogen environment, combining boron and another carbide or nitride-forming element in a 1:3 ratio. Weight was measured before graphitization. The results are shown in Table 10. [Table 10]

[0045] The above examples demonstrate that graphite powder produced according to the present invention exhibits superior specific volume and excellent initial cloning efficiency compared to that produced by state-of-the-art methods, and that the process is simple, resulting in graphite powder with a different chemical composition, whether at the particle surface or bulk, compared to that produced by conventional methods.

[0046] Finally, it should be noted that any discussion of any reference, especially any reference that may have a publication date after the priority date of this application, does not constitute an acknowledgment that it is prior art to the present invention. At the same time, all of the following claims are hereby incorporated in this detailed description or specification as additional aspects of the present invention.

[0047] While the systems and methods described herein have been described in detail, it should be understood that various changes, substitutions, and modifications can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art can experiment with preferred embodiments and identify other methods for carrying out the invention that are not precisely described herein. The inventors intend that modifications and equivalents of the invention are within the scope of the claims, and that the description, abstract, and drawings are not used to limit the scope of the invention. The invention is particularly intended to be as broad as the following claims and their equivalents.

Claims

[Claim 1] A method for forming a graphite anode material for a metal-ion battery, Selectively dividing a carbon precursor material into particles having a desired average particle size; The aforementioned precursor material is combined with a carbide-forming element in a ratio between 0.01% and 10% of the blend; The process includes graphitizing the combination in argon, helium, or nitrogen gas at a temperature between approximately 2500°C and 3000°C to obtain particles having a carbide compound on the surface and a graphite core; The carbide compound comprises carbide-forming elements consisting of B and Ce, The carbide-forming element is selected from Ti, Y, Zr, Nb, La, and combinations thereof. method.

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