Artificial graphite and method for producing the same, negative electrode, and lithium ion battery

Abstract

The embodiment of the application provides artificial graphite and a preparation method thereof, a negative electrode and a lithium ion battery. The preparation method of the artificial graphite comprises the following steps: obtaining a granulation precursor by sequentially performing first mixing and kneading and second mixing and kneading on raw coke powder and a modified solid-phase binder and a liquid-phase binder, and granulating; wherein the modified solid-phase binder comprises a mixture of a solid-phase binder and coke ultrafine powder subjected to fluorination treatment; and performing graphitization on the granulation precursor to obtain the artificial graphite. The preparation method can not only fully utilize the coke ultrafine powder and improve resource utilization, but also has good cycle performance and rate performance.

Description

Technical Field

[0001] This application relates to the field of battery materials, and in particular to an artificial graphite and its preparation method, a negative electrode, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, as the most widely used rechargeable batteries, typically consist of a positive electrode, a negative electrode, a separator, an electrolyte, and a casing. During charge-discharge cycles, the conversion between electrical and chemical energy relies on the insertion and extraction of lithium ions between the positive and negative electrodes in the internal circuit, and the directional migration of electrons in the external circuit. The negative electrode plays a crucial role in storing and releasing lithium ions and conducting current, significantly impacting the battery's energy density, cycle performance, charge-discharge rate, and low-temperature discharge performance. Among numerous materials suitable for negative electrodes, graphite has become the mainstream negative electrode material for large-scale commercial applications due to its advantages such as low cost, high structural stability, non-toxicity, good conductivity, and excellent mechanical properties.

[0003] In the production process of artificial graphite anode materials for lithium-ion batteries, raw coke (such as petroleum coke, needle coke, etc.) needs to be processed to a specific particle size (usually 5-20μm) through crushing and pulverizing to meet the particle size requirements of subsequent granulation, graphitization, and other processes. However, a certain amount of ultrafine powder (particle size <2μm) is inevitably generated during the pulverizing process, which usually accounts for 5%-15% of the total mass of raw coke. Due to its extremely small particle size, this ultrafine powder is difficult to utilize effectively in the production process, resulting in resource waste and increased production costs. Summary of the Invention

[0004] Based on this, embodiments of this application provide an artificial graphite and its preparation method, a negative electrode, and a lithium-ion battery.

[0005] In a first aspect, embodiments of this application provide a method for preparing artificial graphite, comprising:

[0006] The raw coke powder is mixed with a modified solid-phase binder and a liquid-phase binder in a first kneading and a second kneading process, and then granulated to obtain a granulation precursor; wherein, the modified solid-phase binder comprises a mixture of a solid-phase binder and fluorinated coke ultrafine powder.

[0007] The granulation precursor is graphitized to obtain artificial graphite.

[0008] In some embodiments, the solid binder includes one or more of coal tar pitch, petroleum asphalt, phenolic resin, epoxy resin, and polyacrylonitrile; and / or,

[0009] The softening point of the solid binder is above 150°C; and / or,

[0010] The liquid phase binder includes one or more of emulsified asphalt, liquid phase asphalt, tar, and polyacrylic acid.

[0011] In some embodiments, the liquid-phase binder further includes a biomass-based binder, which comprises one or more of lignin, cellulose, protein, amino acids, and starch; and / or,

[0012] The biomass-based binder in the liquid phase binder accounts for 20 wt% to 45 wt% by mass.

[0013] In some embodiments, the mass ratio of the raw coke powder to the modified solid binder is 100:(2-5); and / or,

[0014] In the modified solid binder, the mass ratio of the solid binder to the fluorinated coke ultrafine powder is 100:(15-25); and / or,

[0015] The mass ratio of the raw material coke powder to the liquid phase binder is 100:(6-8).

[0016] In some embodiments, the method for preparing the fluorinated coke ultrafine powder includes:

[0017] The coke ultrafine powder is placed in a fluorine-containing atmosphere for fluorination treatment; the fluorine-containing atmosphere includes fluorine-containing gases, including one or more of fluorine, trifluorine, hexasulfur, carbon tetrafluoride, and hydrogen fluoride.

[0018] In some embodiments, the fluorination treatment includes a first fluorination treatment and a second fluorination treatment performed sequentially;

[0019] The first fluorination treatment includes: placing the coke ultrafine powder in a first fluorine-containing atmosphere, heating it to 230℃~270℃, and holding it at that temperature for 1 hour~2 hours; the first fluorine-containing atmosphere includes fluorine-containing gas and protective gas, and the volume percentage of fluorine-containing gas in the first fluorine-containing atmosphere is 10%~15%;

[0020] The second fluorination treatment includes: placing the coke ultrafine powder that has undergone the first fluorination treatment in a second fluorine-containing atmosphere, heating it from 230℃~270℃ to 330℃~370℃, and holding it at that temperature for 2 hours to 5 hours; the second fluorine-containing atmosphere includes fluorine-containing gas and protective gas, and the volume percentage of fluorine-containing gas in the second fluorine-containing atmosphere is 85%~90%.

[0021] In some embodiments, prior to the fluorination treatment, the coke ultrafine powder is further subjected to nano-sizing treatment; and / or,

[0022] A liquid dispersant is also added during the first mixing process; the mass ratio of the liquid dispersant to the raw coke powder is (1-1.5):100; the liquid dispersant includes one or more of sodium carboxymethyl cellulose, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, fatty acid soap, sodium polyacrylate, polycarboxylate, hydroxyethyl cellulose, and polyacrylate; and / or,

[0023] The graphitization temperature is 2800℃-3000℃, and the graphitization time is 70-85 hours; and / or,

[0024] The granulation process includes: heating the material obtained after mixing to 250℃~290℃, holding it at that temperature for 4 hours~6 hours, then heating it to 630℃~670℃ and holding it at that temperature for 8 hours~10 hours.

[0025] Secondly, embodiments of this application provide an artificial graphite, wherein the artificial graphite satisfies 0.89 < B < 1, and B = pore volume under 2T pressure / pore volume under no pressure.

[0026] Thirdly, embodiments of this application provide a negative electrode comprising the artificial graphite described above.

[0027] Fourthly, embodiments of this application provide a lithium-ion battery, including the negative electrode as described above.

[0028] The method for preparing artificial graphite provided in this application involves sequentially kneading raw coke powder with a modified solid-phase binder and a liquid-phase binder, followed by granulation to obtain a granulation precursor. The modified solid-phase binder comprises a mixture of a solid-phase binder and fluorinated coke ultrafine powder. The granulation precursor is then graphitized to obtain artificial graphite. Adding coke ultrafine powder to the solid-phase binder enhances the graphitization degree and electrical conductivity of the carbon layer in the graphitized solid-phase binder. Fluorination of the coke ultrafine powder avoids or alleviates the problem of self-agglomeration, enhancing the bonding force between the coke ultrafine powder and the solid-phase binder. This preparation method not only fully utilizes the coke ultrafine powder, improving resource utilization and reducing production costs, but also produces artificial graphite with good recycling and rate performance. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0030] Figure 1 A flowchart illustrating a method for preparing artificial graphite provided in an embodiment of this application. Detailed Implementation

[0031] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0033] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, a+b, a+c, b+c, or a+b+c, where a, b, and c can be single or multiple.

[0034] "Parts by weight" is a basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit mass, such as 1g, 1kg, 2g, 2kg, etc. If we say that component A has "a" parts by weight and component B has "b" parts by weight, it means the mass ratio of component A to component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike parts by weight, the sum of the parts by weight of all components is not limited to 100 parts.

[0035] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0036] Please see Figure 1 This application provides a method for preparing artificial graphite, comprising:

[0037] S100, the raw coke powder is mixed with the modified solid-phase binder and the liquid-phase binder in sequence for a first kneading and a second kneading, and then granulated to obtain a granulation precursor; wherein, the modified solid-phase binder includes a mixture of solid-phase binder and fluorinated coke ultrafine powder.

[0038] It should be noted that by adding coke ultrafine powder to the solid binder, the graphitization degree and electrical conductivity of the carbon layer of the solid binder after graphitization can be enhanced; by fluorinating the coke ultrafine powder, the problem of self-agglomeration of the coke ultrafine powder can be avoided or alleviated, and the bonding force between the coke ultrafine powder and the solid binder can be enhanced.

[0039] For example, both the coke ultrafine powder and the raw coke powder are obtained by crushing the raw coke, and the raw coke includes one or more of needle coke, petroleum coke, and pitch coke.

[0040] For example, the particle size D50 of the raw coke powder is 6.5μm-10.5μm, such as 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, etc.

[0041] For example, the particle size D50 of the coke ultrafine powder is less than or equal to 2 μm, such as 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, etc.

[0042] For example, the solid binder includes one or more of coal tar pitch, petroleum pitch, phenolic resin, epoxy resin, and polyacrylonitrile.

[0043] For example, the particle size D50 of the solid binder is 3μm-5μm, such as 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc.

[0044] For example, the softening point of the solid binder is above 150°C.

[0045] It should be noted that when the softening point of the solid binder is below 150℃, it may soften or even liquefy prematurely during the granulation process, resulting in excessive loss or uneven distribution of the binder during the mixing stage. This prevents the formation of an effective bonding network within the particles and leads to excessively large pore sizes in the carbon layer of the resulting artificial graphite, resulting in poor cycle performance. On the other hand, solid binders with softening points above 150℃ can maintain an appropriate solid or semi-solid state at the initial granulation temperature. As the material is uniformly dispersed, they gradually exert their bonding effect under subsequent higher temperatures, resulting in artificial graphite with relatively smaller pore sizes and better cycle performance.

[0046] For example, the liquid phase binder includes one or more of emulsified asphalt, liquid phase asphalt, tar, and polyacrylic acid.

[0047] For example, the liquid phase binder further includes a biomass-based binder, which includes one or more of lignin, cellulose, protein, amino acids, and starch.

[0048] It should be noted that by adding a biomass binder to the liquid phase binder, the biomass binder can be introduced into the prepared artificial graphite particles to enhance the carbon layer, thereby improving the structural stability of the artificial graphite particles.

[0049] For example, the biomass-based binder in the liquid phase binder has a mass percentage of 20wt% to 45wt%, such as 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, etc.

[0050] For example, the mass ratio of the raw material coke powder to the modified solid phase binder is 100:(2-5), such as 100:2, 100:3, 100:4, 100:5, etc.

[0051] For example, in the modified solid binder, the mass ratio of the solid binder to the fluorinated coke ultrafine powder is 100:(15-25), such as 100:15, 100:18, 100:20, 100:22, 100:25, etc.

[0052] For example, the mass ratio of the raw material coke powder to the liquid phase binder is 100:(6-8), such as 100:6, 100:7, 100:8, etc.

[0053] For example, the method for preparing the fluorinated coke ultrafine powder includes:

[0054] The coke ultrafine powder is placed in a fluorine-containing atmosphere for fluorination treatment; the fluorine-containing atmosphere includes fluorine-containing gases, including one or more of fluorine, trifluorine, hexasulfur, carbon tetrafluoride, and hydrogen fluoride.

[0055] For example, the fluorination treatment includes a first fluorination treatment and a second fluorination treatment performed sequentially;

[0056] The first fluorination treatment includes: placing the coke ultrafine powder in a first fluorine-containing atmosphere, heating it to 230℃~270℃, and holding it at that temperature for 1 hour~2 hours; the first fluorine-containing atmosphere includes fluorine-containing gas and protective gas, and the volume percentage of fluorine-containing gas in the first fluorine-containing atmosphere is 10%~15%;

[0057] The second fluorination treatment includes: placing the coke ultrafine powder that has undergone the first fluorination treatment in a second fluorine-containing atmosphere, heating it from 230℃~270℃ to 330℃~370℃, and holding it at that temperature for 2 hours to 5 hours; the second fluorine-containing atmosphere includes fluorine-containing gas and protective gas, and the volume percentage of fluorine-containing gas in the second fluorine-containing atmosphere is 85%~90%.

[0058] It should be noted that the first fluorination treatment is mainly used to fluorinate the sharp edges of the coking ultrafine powder surface, while the second fluorination treatment is mainly used to fluorinate the smooth parts of the coking ultrafine powder surface.

[0059] For example, the protective gas includes one or more of nitrogen and inert gases, wherein the inert gas includes one or more of helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0060] For example, in the first fluorination treatment, the heating rate during the heating process is 5°C / min-10°C / min; in the second fluorination treatment, the heating rate during the heating process is 2°C / min-5°C / min.

[0061] For example, prior to the fluorination treatment, the coke ultrafine powder is further subjected to nano-sizing treatment.

[0062] It should be noted that by nano-processing the coke ultrafine powder, the particle size of the coke ultrafine powder can be reduced to the nanoscale, and the particle size of the coke ultrafine powder can be made more uniform, thereby improving the uniformity of mixing the coke ultrafine powder with the solid binder.

[0063] For example, the nano-processing includes: ball milling the coking ultrafine powder with a ball-to-material ratio of (10-15):1, a ball milling speed of 600 r / min-800 r / min, and a ball milling time of 18 hours-36 hours.

[0064] For example, after nano-sizing, the particle size D50 of the coke ultrafine powder is less than or equal to 500nm, such as 500nm, 400nm, 300nm, 200nm, 100nm, 50nm, 10nm, etc.

[0065] For example, a liquid dispersant is also added during the first kneading process; the mass ratio of the liquid dispersant to the raw material coke powder is (1-1.5):100; the liquid dispersant includes one or more of sodium carboxymethyl cellulose, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, fatty acid soap, sodium polyacrylate, polycarboxylate, hydroxyethyl cellulose, and polyacrylate.

[0066] For example, the mass ratio of the liquid dispersant to the raw material coke powder can be 1:100, 1.1:100, 1.2:100, 1.3:100, 1.4:100, or 1.5:100.

[0067] It should be noted that by adding a liquid phase dispersant, the mixing uniformity of the raw coke powder and the liquid phase binder can be improved when they are kneaded.

[0068] For example, the granulation includes: heating the material obtained after kneading to 250°C to 290°C, holding it at that temperature for 4 to 6 hours, then heating it to 630°C to 670°C, and holding it at that temperature for 8 to 10 hours.

[0069] For example, the material obtained after kneading is heated to 250℃~290℃ at a heating rate of 3℃ / min-6℃ / min, and the material obtained after kneading is heated from 250℃~290℃ to 630℃~670℃ at a heating rate of 5℃ / min-7℃ / min.

[0070] S200 is used to graphitize the granulation precursor to obtain artificial graphite.

[0071] For example, graphitization is carried out in an Atchison furnace.

[0072] For example, the graphitization temperature is 2800℃-3000℃, such as 2800℃, 2850℃, 2900℃, 2950℃, 3000℃, etc.

[0073] For example, the graphitization time is 70-85 hours, such as 70 hours, 72 hours, 75 hours, 78 hours, 80 hours, 82 hours, 85 hours, etc.

[0074] For example, before graphitizing the granulation precursor, the granulation precursor is fed into a carbonization furnace for carbonization at a temperature of 1050°C to 1250°C for a duration of 11 to 19 hours.

[0075] The method for preparing artificial graphite provided in this application involves sequentially kneading raw coke powder with a modified solid-phase binder and a liquid-phase binder, followed by granulation to obtain a granulation precursor. The modified solid-phase binder comprises a mixture of a solid-phase binder and fluorinated coke ultrafine powder. The granulation precursor is then graphitized to obtain artificial graphite. Adding coke ultrafine powder to the solid-phase binder enhances the graphitization degree and electrical conductivity of the carbon layer in the graphitized solid-phase binder. Fluorination of the coke ultrafine powder avoids or alleviates the problem of self-agglomeration, enhancing the bonding force between the coke ultrafine powder and the solid-phase binder. This preparation method not only fully utilizes the coke ultrafine powder, improving resource utilization and reducing production costs, but also produces artificial graphite with good recycling and rate performance.

[0076] This application provides an artificial graphite, prepared using the method described above. The artificial graphite satisfies 0.89 < B < 1, where B = pore volume under 2T pressure / pore volume without applied pressure. Both the pore volume under 2T pressure and the pore volume without applied pressure are obtained using an F-Sorb 3400 multi-station pore size analyzer.

[0077] This application provides a negative electrode comprising the artificial graphite described above.

[0078] This application provides a lithium-ion battery, including the negative electrode as described above.

[0079] For example, the negative electrode includes a negative electrode current collector, a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer and the second negative electrode active material layer are respectively disposed on opposite sides of the negative electrode current collector, and at least one of the first negative electrode active material layer and the second negative electrode active material layer includes artificial graphite as described above.

[0080] The artificial graphite and its preparation method provided in this application will be described in detail below with reference to specific embodiments.

[0081] Example 1

[0082] A method for preparing an artificial graphite includes:

[0083] Step 10: Provide raw coke (petroleum coke), dry and pulverize the raw coke to obtain raw coke powder (aggregate) with a particle size D50 of 8.5 μm and coke ultrafine powder with a particle size D50 of 1 μm; place the coke ultrafine powder in a fluorination reactor, and introduce a fluorine-containing atmosphere (fluorine gas mixed with inert gas) at a flow rate of 70 ml / min. Perform two-stage fluorination. The first stage of pre-fluorination is from room temperature to 250℃ (the volume percentage of inert gas in the fluorine-containing atmosphere is 88%), with a heating rate of 7.5℃ / min and a holding time of 1.5 hours; the second stage of fluorination is at 300℃ (the volume percentage of fluorine gas in the fluorine-containing atmosphere is 88%), with a heating rate of 3.5℃ / min and a holding time of 3.5 hours. After cooling, fluorinated coke ultrafine powder can be obtained.

[0084] Step 20: Fluorinated coke ultrafine powder and a solid-phase binder (coal tar pitch) with a particle size D50 of 3.5 μm are uniformly mixed at a mass ratio of 20:100 to obtain a modified solid-phase binder. The modified solid-phase binder is then uniformly mixed with aggregate (raw coke powder with a particle size D50 of 8.5 μm) at a mass ratio of 3.5:100. A liquid-phase binder (emulsified asphalt) is added for solid-liquid kneading at a speed of 35 Hz for 3.5 hours. The liquid-phase binder and aggregate (coke powder with a particle size D50 of 8.5 μm) are then mixed uniformly at a mass ratio of 3.5:100. The mass ratio of raw coke powder (8.5 μm) to 50 was 7:100; it was then fed into a reactor, and the temperature profile was two-stage. The first stage involved heating from room temperature to 270°C at a heating rate of 4°C / min and holding at 270°C for 3.5 hours at a rotation speed of 18 Hz. The second stage involved heating from 270°C to 650°C at a heating rate of 6°C / min and holding at 650°C for 9 hours at a rotation speed of 25 Hz. The mixture was then cooled to room temperature to obtain the granulation precursor.

[0085] Step 30: The granulation precursor is fed into a carbonization furnace for carbonization at a temperature of 1150°C for 15 hours. Then, it is graphitized in an Atchison graphitization furnace at a temperature of 2900°C. After being powered on for 78 hours, it is allowed to cool naturally before being removed from the furnace. The material is then mixed, screened twice, and demagnetized twice to obtain artificial graphite.

[0086] Example 2

[0087] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0088] In step 20, the fluorinated coke ultrafine powder and the solid phase binder (coal tar pitch) with a particle size D50 of 3.5 μm are uniformly mixed at a mass ratio of 15:100 to obtain the modified solid phase binder.

[0089] Example 3

[0090] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0091] In step 20, the fluorinated coke ultrafine powder and the solid phase binder (coal tar pitch) with a particle size D50 of 3.5 μm are uniformly mixed at a mass ratio of 25:100 to obtain the modified solid phase binder.

[0092] Example 4

[0093] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0094] In step 20, the modified solid binder and aggregate (raw coke powder with a particle size D50 of 8.5 μm) are mixed uniformly at a mass ratio of 2:100.

[0095] Example 5

[0096] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0097] In step 20, the modified solid binder and aggregate (raw coke powder with a particle size D50 of 8.5 μm) are mixed uniformly at a mass ratio of 5:100.

[0098] Example 6

[0099] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0100] In step 20, the mass ratio of liquid phase binder to aggregate (raw coke powder with a particle size D50 of 8.5 μm) is 6:100.

[0101] Example 7

[0102] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0103] In step 20, the mass ratio of liquid phase binder to aggregate (raw coke powder with a particle size D50 of 8.5 μm) is 8:100.

[0104] Example 8

[0105] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0106] In step 10, before placing the coke ultrafine powder in the fluorination furnace, the coke ultrafine powder is ball-milled with a ball-to-material ratio of 13:1, a ball milling speed of 700 r / min, and a ball milling time of 27 hours to obtain nano-sized ultrafine powder.

[0107] Example 9

[0108] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0109] In step 20, before adding the liquid phase binder (emulsified asphalt) for solid-liquid mixing, a liquid phase dispersant (sodium carboxymethyl cellulose) is added for solid-solid mixing. The mass ratio of the liquid phase dispersant to the aggregate (raw coke powder with a particle size D50 of 8.5 μm) is 1.5:100, the rotation speed is 30 Hz, and the mixing time is 1 hour.

[0110] Example 10

[0111] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0112] In step 20, the liquid phase binder (emulsified bitumen) also includes a biomass-based binder (lignin), and the biomass-based binder (lignin) in the liquid phase binder (emulsified bitumen) accounts for 32.5 wt%.

[0113] Example 11

[0114] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0115] In step 20, the liquid phase binder (emulsified bitumen) also includes a biomass-based binder (lignin), and the biomass-based binder (lignin) in the liquid phase binder (emulsified bitumen) accounts for 20 wt%.

[0116] Example 12

[0117] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0118] In step 20, the liquid phase binder (emulsified bitumen) also includes a biomass-based binder (lignin), and the biomass-based binder (lignin) in the liquid phase binder (emulsified bitumen) accounts for 45 wt% of the total mass.

[0119] Example 13

[0120] A method for preparing an artificial graphite differs from that in Example 1 in that:

[0121] In step 10, before placing the coke ultrafine powder in the fluorination reactor, the coke ultrafine powder is ball-milled with a ball-to-material ratio of 13:1, a ball milling speed of 700 r / min, and a ball milling time of 27 hours to obtain nano-sized ultrafine powder.

[0122] In step 20, before adding the liquid phase binder (emulsified asphalt) for solid-liquid mixing, a liquid phase dispersant (sodium carboxymethyl cellulose) is added for solid-solid mixing. The mass ratio of the liquid phase dispersant to the aggregate (raw coke powder with a particle size D50 of 8.5 μm) is 1.5:100, the rotation speed is 30 Hz, and the mixing time is 1 hour. The liquid phase binder (emulsified asphalt) also includes a biomass-based binder (lignin), and the mass percentage of the biomass-based binder (lignin) in the liquid phase binder (emulsified asphalt) is 32.5 wt%.

[0123] Comparative Example 1

[0124] A method for preparing an artificial graphite includes:

[0125] Step 11: Provide raw coke (petroleum coke), dry and pulverize the raw coke to obtain raw coke powder with a particle size D50 of 8.5μm.

[0126] Step 12: A solid binder (coal tar pitch) with a particle size D50 of 3.5 μm and raw coke powder (aggregate) with a particle size D50 of 8.5 μm are uniformly mixed at a mass ratio of 3.5:100, and then fed into a mechanical kneader for solid-solid mixing; then fed into a reactor, the temperature curve is two-stage: the first stage: the temperature is increased from room temperature to 270℃ at a heating rate of 4℃ / min, and held at 270℃ for 3.5 hours at a rotation speed of 18Hz; the second stage: the temperature is increased from 270℃ to 650℃ at a heating rate of 6℃ / min, and held at 650℃ for 9 hours at a rotation speed of 25Hz; then cooled to room temperature; the granulation precursor is obtained.

[0127] Step 13: The granulation precursor is fed into a carbonization furnace for carbonization at a temperature of 1150°C for 15 hours. Then, it is graphitized in an Atchison graphitization furnace at a temperature of 2900°C. After being powered on for 78 hours, it is allowed to cool naturally before being removed from the furnace. The material is then mixed, screened twice, and demagnetized twice to obtain artificial graphite.

[0128] It can be seen that the difference between Comparative Example 1 and Example 1 is that: Comparative Example 1 did not add coke ultrafine powder when preparing artificial graphite, but only used raw coke powder (aggregate) with a particle size D50 of 8.5μm and a solid phase binder (coal tar pitch) for blending.

[0129] Material property testing:

[0130] The artificial graphite prepared in Examples 1-13 and Comparative Example 1 was subjected to performance tests. The test parameters and methods are as follows:

[0131] Particle size: obtained using a Malvern Panaco Zetasizer Ultra dynamic scattering particle size analyzer;

[0132] Tap density: obtained using a Canta tap density instrument;

[0133] Specific surface area (BET): obtained using a quanta tester;

[0134] Graphite orientation degree (OI value): obtained by measuring the intensity ratio of the 002 peak and the 110 peak using an X-ray diffractometer;

[0135] Oil absorption value: obtained using a DABS-H oil absorption value tester;

[0136] Compacted density (5T): obtained using a universal testing machine;

[0137] The pore volume under no pressure and the pore volume under 2T pressure were obtained using an F-Sorb 3400 multi-station pore size analyzer.

[0138] B: B = pore volume under 2T pressure / pore volume without pressure.

[0139] The test results are shown in Table 1.

[0140] Table 1

[0141]

[0142]

[0143] As can be seen from Table 1:

[0144] The compacted density of the artificial graphite prepared in Examples 1-13 is higher than that of the artificial graphite prepared in Comparative Example 1, indicating that the artificial graphite prepared in Examples 1-13 has higher structural density. The artificial graphite prepared in Examples 1-13 can satisfy 0.89 < B < 1, while the B value of the artificial graphite prepared in Comparative Example 1 is less than 0.89, indicating that the artificial graphite prepared in Examples 1-13 has better structural stability.

[0145] Button power test:

[0146] The method for preparing the coin cell used to test electrochemical performance is as follows: The negative electrode materials of the batteries prepared in Examples 1-13 and Comparative Example 1 were mixed with conductive agent (SP), CMC, and SBR in a mass ratio of 95:1.5:1.5:2, respectively, and coated onto copper foil with a compaction density of 1.60 g / cm³. 3After vacuum drying, the electrolyte is used as the negative electrode, with lithium metal as the counter electrode. The electrolyte is a 1M LiPF6 mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 mass ratio. The separator is a PE / PPPE composite membrane, forming a coin cell. Initial discharge capacity and efficiency were tested: Cyclic performance was tested at 3C current density with a charging voltage limited to 0.005-2V. Rate performance tests were also conducted at different rates (50 cycles at a single rate). The EIS internal resistance was measured using electrochemical impedance spectroscopy. The test results are shown in Table 2.

[0147] Table 2

[0148]

[0149] As can be seen from Table 2:

[0150] The artificial graphite prepared in Examples 1-13 exhibits higher initial discharge capacity, initial discharge efficiency, capacity retention after 1000 cycles at 1C at room temperature, and capacity retention at 4C rate than the artificial graphite prepared in Comparative Example 1. Furthermore, the artificial graphite prepared in Examples 1-13 has lower EIS internal resistance and 50-cycle expansion rate at 4C rate than the artificial graphite prepared in Comparative Example 1. This indicates that the cycling performance and rate performance of the artificial graphite prepared in Examples 1-13 are superior to those of Comparative Example 1. It is known that the preparation method of Comparative Example 1 is a traditional method for preparing artificial graphite, while the preparation method of this application involves fluorinating the coke ultrafine powder before adding it to the raw materials of artificial graphite. In other words, this application not only achieves efficient resource utilization of the coke ultrafine powder and reduces raw material costs, but also effectively improves the overall performance of artificial graphite.

[0151] The artificial graphite and its preparation method, negative electrode, and lithium-ion battery provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application, and the descriptions of the embodiments above are only for the purpose of helping to understand this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing artificial graphite, characterized in that, include: After mixing raw coke powder with a modified solid-phase binder, a liquid-phase binder is added for kneading and granulation to obtain a granulation precursor. The modified solid-phase binder comprises a mixture of a solid-phase binder and fluorinated coke ultrafine powder. Prior to the fluorination treatment, the coke ultrafine powder undergoes nano-sizing. The particle size D50 of the coke ultrafine powder is less than or equal to 2 μm, and the particle size D50 of the raw coke powder is 6.5 μm to 10.5 μm. The granulation precursor is graphitized to obtain artificial graphite; The mass ratio of the raw coke powder to the modified solid phase binder is 100: (2-5); the mass ratio of the solid phase binder to the fluorinated coke ultrafine powder is 100: (15-25); and the mass ratio of the raw coke powder to the liquid phase binder is 100: (6-8).

2. The method for preparing artificial graphite according to claim 1, characterized in that, The solid binder includes one or more of coal tar pitch, petroleum asphalt, phenolic resin, epoxy resin, and polyacrylonitrile; and / or, The softening point of the solid binder is above 150°C; and / or, The liquid phase binder includes one or more of emulsified asphalt, liquid phase asphalt, tar, and polyacrylic acid.

3. The method for preparing artificial graphite according to claim 2, characterized in that, The liquid-phase binder further includes a biomass-based binder, which comprises one or more of lignin, cellulose, protein, amino acids, and starch; and / or, The biomass-based binder in the liquid phase binder accounts for 20wt% to 45wt% of the total mass.

4. The method for preparing artificial graphite according to claim 1, characterized in that, The method for preparing the fluorinated coke ultrafine powder includes: The coke ultrafine powder is placed in a fluorine-containing atmosphere for fluorination treatment; the fluorine-containing atmosphere includes fluorine-containing gases, including one or more of fluorine, trifluorine, hexasulfur, carbon tetrafluoride, and hydrogen fluoride.

5. The method for preparing artificial graphite according to claim 4, characterized in that, The fluorination treatment includes a first fluorination treatment and a second fluorination treatment performed sequentially. The first fluorination treatment includes: placing the coke ultrafine powder in a first fluorine-containing atmosphere, heating it to 230℃~270℃, and holding it at that temperature for 1 hour~2 hours; the first fluorine-containing atmosphere includes a fluorine-containing gas and a protective gas, and the volume percentage of the fluorine-containing gas in the first fluorine-containing atmosphere is 10%~15%; The second fluorination treatment includes: placing the coke ultrafine powder that has undergone the first fluorination treatment in a second fluorine-containing atmosphere, heating it from 230℃~270℃ to 330℃~370℃, and holding it at that temperature for 2 hours~5 hours; the second fluorine-containing atmosphere includes fluorine-containing gas and protective gas, and the volume percentage of fluorine-containing gas in the second fluorine-containing atmosphere is 85%~90%.

6. The method for preparing artificial graphite according to any one of claims 1-5, characterized in that, Before adding the liquid phase binder and kneading, the process further includes: adding a liquid phase dispersant and performing solid-solid kneading; the mass ratio of the liquid phase dispersant to the raw material coke powder is (1-1.5):100; the liquid phase dispersant includes one or more of sodium carboxymethyl cellulose, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, fatty acid soap, sodium polyacrylate, polycarboxylate, hydroxyethyl cellulose, and polyacrylate; and / or, The graphitization temperature is 2800℃~3000℃, and the graphitization time is 70 hours~85 hours; and / or, The granulation process includes: heating the material obtained after mixing to 250℃~290℃, holding it at that temperature for 4 to 6 hours, then heating it to 630℃~670℃ and holding it at that temperature for 8 to 10 hours.

7. A type of artificial graphite, characterized in that, It is prepared by the method for preparing artificial graphite according to any one of claims 1-6.

8. The artificial graphite according to claim 7, characterized in that, The artificial graphite satisfies 0.89 < B < 1, where B = pore volume under 2T pressure / pore volume under no pressure.

9. A negative electrode, characterized in that, Includes the artificial graphite as described in any one of claims 7-8.

10. A lithium-ion battery, characterized in that, Includes the negative electrode as described in claim 9.

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