Graphite negative electrode active material, and preparation method therefor and rate performance evaluation method therefor

Abstract

The present application relates to the technical field of secondary batteries, and provides a graphite negative electrode active material, and a preparation method therefor and a rate performance evaluation method therefor. The rate performance index of the graphite negative electrode active material is denoted as W, W=(O×T×Dv50finished product) / (OI×Dv50aggregate), and W≥3.0, wherein O is the oil absorption number of the graphite negative electrode active material, measured in mL / 100g; T is the tap density of the graphite negative electrode active material, measured in g / cm3; Dv50finished product is the particle size corresponding to the time point at which the cumulative volume distribution percentage of the graphite negative electrode active material reaches 50%, measured in μm; OI is the orientation degree of the graphite negative electrode active material; and Dv50aggregate is the particle size corresponding to the time point at which the cumulative volume distribution percentage of the aggregate used in the graphite negative electrode active material reaches 50%, measured in μm.

Description

Graphite negative electrode active material, preparation method thereof and evaluation method of rate capability

[0001] Cross-reference to related applications

[0002] The present application is based on and claims priority from Chinese Patent Application No. 202411001571.7, filed on July 24, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application belongs to the technical field of secondary batteries, and specifically relates to a graphite negative electrode active material, a preparation method thereof and an evaluation method of rate capability. BACKGROUND

[0004] Lithium ion batteries have the characteristics of long cycle life, high energy density, environmental friendliness and the like, and are widely used in new energy fields such as electric vehicles, energy storage, 3C and the like. At present, the negative electrode active material of commercialized lithium ion batteries is mainly graphite, but graphite itself has a crystal layer structure characteristic, and the theoretical interlayer spacing is small, which cannot meet the requirements of large current charging, and there is a risk of lithium precipitation during fast charging, which will bring serious safety hazards to the battery and the entire power system.

[0005] The related technology proposes to use pulverized needle coke (particle size D50 = 3-10 μm) as the main body, and to obtain high-compaction and high-rate artificial graphite by using a twice-coating granulation method. In the method, a binding granulation method is used for the first coating, and a resin material is uniformly coated on the surface of small particles to form a uniform hard carbon coating layer. Lithium ions can quickly diffuse into the particle interior in the medium of the hard carbon layer, and high rate capability is achieved. The fusion drying improves the tap density of the secondary particle material. Then, after depolymerization and screening, small particles (particle size D50 = 5-10 μm) coated well in the first coating are selected and combined with heavy oil (pitch) to form a soft carbon coating layer on the surface of the secondary particles by using a liquid phase coating granulation method, so as to reduce the specific surface area. Finally, after carbonization and graphitization treatment, high-compaction and high-rate artificial graphite material is obtained. However, the related technology needs to perform twice-coating and granulation processes, and also uses a liquid coating agent, so that the process and equipment are relatively complex, and the production cost is relatively high.

[0006] With the increasing demand for fast charging performance of lithium ion batteries in the domestic and foreign markets, the rate capability of graphite negative electrode active material still needs to be improved. In addition, the preparation method of the graphite negative electrode active material needs to be simplified, and the production cost needs to be reduced.

[0007] In addition, the current evaluation method for the rate performance of the graphite negative electrode active material is to assemble it into a button cell first, and then test the rate performance of the button cell. This evaluation method has a large workload, which is not conducive to rapid evaluation and subsequent selection work, so it is necessary to design an evaluation method for the rate performance of the graphite negative electrode active material, which can more simply judge the advantages and disadvantages of the rate performance. SUMMARY

[0008] The present application aims to at least partially solve one of the technical problems in the related art. To this end, the present application provides a graphite negative electrode active material, a preparation method thereof and an evaluation method for the rate performance thereof.

[0009] In a first aspect, the present application provides a graphite negative electrode active material, wherein an index of rate performance of the graphite negative electrode active material is marked as W, W = (O x T x Dv50 成品 ) / (OI x Dv50 骨料 ), and W ≥ 3.0; wherein O is an oil absorption value of the graphite negative electrode active material, in mL / 100g; T is a tap density of the graphite negative electrode active material, in g / cm 3 ; Dv50 成品 is a particle size corresponding to a cumulative volume distribution percentage of 50% of the graphite negative electrode active material, in μm; OI is an orientation degree of the graphite negative electrode active material; and Dv50 骨料 is a particle size corresponding to a cumulative volume distribution percentage of 50% of an aggregate used by the graphite negative electrode active material, in μm.

[0010] In some embodiments, W ≥ 5.0.

[0011] In some embodiments, W ≥ 30.0.

[0012] In some embodiments, W ≥ 55.0.

[0013] In some embodiments, Dv50 成品 is 6-25 μm; and / or, Dv50 骨料 is 5-10 μm; and / or, 1.2 ≤ Dv50 成品 / Dv50 骨料 < 5; and / or, O is 50-100 mL / 100g; and / or, T is 0.80-1.20 g / cm 3 ; and / or, OI is 2-11.

[0014] In a second aspect, the present application provides a preparation method of a graphite negative electrode active material, comprising the following steps:

[0015] S101. pretreating raw materials to obtain pretreated materials; then grinding and optionally shaping the pretreated materials to obtain aggregates; optionally, high-temperature calcining the aggregates to obtain high-temperature calcined aggregates;

[0016] S201. mixing the aggregates and / or the calcined aggregates with a binder and a solvent to obtain a mixture; then making the mixture into centimeter-level granular materials at room temperature; and drying the granular materials to obtain dry granular materials;

[0017] S301. graphitizing the dry granular materials to obtain graphitized granular materials;

[0018] S401. processing the graphitized granular materials into finished products after crushing to obtain finished products of the graphite negative electrode active material.

[0019] In some embodiments, Dv50 骨料 is 5-10 μm; and / or, Dv50 成品 is 6-25 μm; and / or, 1.2≤Dv50 成品 / Dv50 骨料 <5; and / or, O is 50-100 mL / 100g; and / or, T is 0.80-1.20 g / cm 3 ; and / or, OI is 2-11.

[0020] In some embodiments, the particle size of the granular materials is 1-50 cm.

[0021] In a third aspect, the present application provides a method for evaluating the rate capability of a graphite negative electrode active material, comprising the following steps:

[0022] S1. setting the rate capability index of the graphite negative electrode active material as W, W=(O×T×Dv50 成品 ) / (OI×Dv50 骨料 ); wherein, O is the oil absorption value of the graphite negative electrode active material, in units of mL / 100g; T is the tap density of the graphite negative electrode active material, in units of g / cm 3 ; Dv50 成品 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the graphite negative electrode active material, in units of μm; OI is the orientation degree of the graphite negative electrode active material; Dv50 骨料 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the aggregates used by the graphite negative electrode active material, in units of μm;

[0023] S2. according to O, T, Dv50 成品 , OI and Dv50骨料 W is calculated;

[0024] S3. When W is greater than or equal to 3.0, the graphite negative electrode active material is determined to be a high-rate performance negative electrode active material; when W is less than 3.0, the graphite negative electrode active material is determined to be a low-rate performance negative electrode active material.

[0025] In some embodiments, the greater the W, the higher the rate performance of the graphite negative electrode active material.

[0026] Compared with the related art, the application has the following advantages and technical effects:

[0027] (1) In the graphite negative electrode active material of the application, the oil absorption value O, the orientation degree OI, the tap density T, the finished product particle size Dv50 成品 and the aggregate particle size Dv50 骨料 of the material are matched and designed, so that the five parameters satisfy the above relationship W = (O x T x Dv50 成品 ) / (OI x Dv50 骨料 ), and W is greater than or equal to 3.0, so that the graphite negative electrode active material has high rate performance. If W is less than 3.0, the rate performance of the graphite negative electrode active material is poor.

[0028] (2) The preparation method of the application does not have a heating granulation process, and the process and equipment are simple, which has cost advantages, and can also be adapted to all raw materials. In addition, without the heating granulation process in step S201, the preparation method of the application can have an effect better than the heating granulation process by making centimeter-level granular materials in step S201, so that the graphite negative electrode active material has more graphite layer end faces exposed, which is beneficial to lithium ion deintercalation, and has high rate performance and cycle performance.

[0029] (3) The evaluation method of the application finds the relationship between the five core parameters of the oil absorption value, the tap density, the finished product particle size, the orientation degree and the aggregate particle size of the graphite negative electrode active material and the rate performance of the graphite negative electrode active material by comprehensively considering the influence of the five core parameters on the rate performance of the graphite negative electrode active material, and uses the W value to represent the pros and cons of the rate performance of the graphite negative electrode active material. Therefore, by the evaluation method of the embodiments of the application, the pros and cons of the rate performance of the graphite negative electrode active material can be quickly judged before the test battery is assembled, and the judgment result is accurate. There is no need to assemble a test battery to test the rate performance, which is beneficial to save time, improve efficiency and facilitate the rapid progress of the selection work. BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 1, magnified by 1000 times;

[0031] Fig. 2 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 1, magnified 2000 times;

[0032] Fig. 3 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 2, magnified 1000 times;

[0033] Fig. 4 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 2, magnified 2000 times;

[0034] Fig. 5 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 3, magnified 1000 times;

[0035] Fig. 6 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 3, magnified 2000 times;

[0036] Fig. 7 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 4, magnified 1000 times;

[0037] Fig. 8 is a SEM image of the graphite negative electrode active material obtained by the preparation method of Example 4, magnified 2000 times. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative work, fall within the scope of protection of the present application.

[0039] Unless otherwise defined, all the technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs; the terms used herein are only for the purpose of describing the specific embodiments of the present application, and are not intended to limit the present application; the terms "comprise" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings, are intended to cover the non-exclusive inclusion.

[0040] The ranges disclosed herein are defined by the endpoints as "from" and "to" and the given range is inclusive of the endpoints. Ranges can be combined, i.e., any lower limit of a range can be combined with any upper limit of another range to form a new range. For example, if a range is listed as 60-120 and another range is listed as 80-110, it is understood that a range of 60-110 is also contemplated. Furthermore, if a minimum range value is listed as 1 and a maximum range value is listed as 3, then the following ranges are contemplated: 1-3, 1-2, 2-3, and 1-2. In this application, unless otherwise indicated, a numerical value range "a-b" indicates a shorthand way of describing any integer combination of the range of values between "a" and "b", where "a" and "b" are both real numbers. For example, the numerical value range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand way of describing these numerical value combinations. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there can be three cases: A exists alone, A and B exist together, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after it.

[0042] In a first aspect, the embodiments of the present application provide a graphite negative electrode active material, a rate performance index of the graphite negative electrode active material is marked as W, W = (O × T × Dv50 成品 ) / (OI × Dv50 骨料 ), and W ≥ 3.0; wherein O is an oil absorption value of the graphite negative electrode active material, in mL / 100g; T is a tap density of the graphite negative electrode active material, in g / cm 3 ; Dv50 成品 is a particle size corresponding to a cumulative volume distribution percentage of 50% of the graphite negative electrode active material, in μm; OI is an orientation degree of the graphite negative electrode active material; and Dv50 骨料 is a particle size corresponding to a cumulative volume distribution percentage of 50% of aggregate used by the graphite negative electrode active material, in μm.

[0043] In the graphite negative electrode active material of the embodiments of the present application, the oil absorption value O, the orientation degree OI, the tap density T, the finished product particle size Dv50 成品 , and the aggregate particle size Dv50骨料 The matching design is performed to make the five parameters satisfy the above relationship formula W = (O x T x Dv50 成品 ) / (O1 x Dv50 骨料 ), and make W greater than or equal to 3.0, so that the graphite negative electrode active material has high rate performance. If W is less than 3.0, the rate performance of the graphite negative electrode active material is poor.

[0044] For example, the W of the graphite negative electrode active material of the embodiment of the present application can be 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 12.0, 14.0, 16.0, 18.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0, 55.0, 60.0, 65.0, 70.0, 75.0, 80.0, 85.0, 90.0, 95.0, 100.0, 105.0, 110.0, 115.0, 120.0, 125.0, 130.0, 135.0, 140.0, 145.0, etc.

[0045] In some embodiments, W≥5.0. When the rate performance evaluation index W of the graphite negative electrode active material is greater than or equal to 5.0, the rate performance of the graphite negative electrode active material is further improved.

[0046] In some embodiments, W≥30.0. When the rate performance evaluation index W of the graphite negative electrode active material is greater than or equal to 30.0, the rate performance of the graphite negative electrode active material is more excellent.

[0047] In some embodiments, W≥55.0. When the rate performance evaluation index W of the graphite negative electrode active material is greater than or equal to 55.0, the rate performance of the graphite negative electrode active material is further more excellent.

[0048] In some embodiments, 55.0≤W≤110.0. When the rate performance evaluation index W of the graphite negative electrode active material is too large, the tap density of the material can be too small, which can cause poor processing performance of the material, easy agglomeration when the material is made into battery slurry, and unstable area density when the material is made into battery pole piece. Or, when the rate performance evaluation index W of the graphite negative electrode active material is too large, the aggregate particle size Dv50 骨料 of the material can be too small, which can cause low efficiency and low material yield in the grinding and shaping process, and is not conducive to reducing the production cost of the graphite negative electrode active material. Therefore, in actual application, it is not required that the rate performance of the battery is higher and higher, but other aspects of performance need to be considered comprehensively, so as to design a battery with good comprehensive performance.

[0049] In some embodiments, Dv50 成品6-25 μm, for example 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 25 μm, etc. When the finished product particle size Dv50 成品 is too small, it is not conducive to the formation of secondary particles, thereby not conducive to improve the rate performance of the graphite negative active material. When the finished product particle size Dv50 成品 is too large, it will make the graphite negative active material processing performance is poor, easy to have large particles when coating, increase the difficulty of the battery.

[0050] In some embodiments, Dv50 骨料 is 5-10 μm, for example 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, etc., and can be selected to be 7-10 μm. When the aggregate particle size Dv50 骨料 is too small, it will make the efficiency and material yield in the process of grinding and optionally shaping are low, not conducive to reduce the production cost of the graphite negative active material. When the aggregate particle size Dv50 骨料 is too large, it is not conducive to the formation of secondary particles, thereby not conducive to improve the rate performance of the graphite negative active material.

[0051] In some embodiments, 1.2≤Dv50 成品 / Dv50 骨料 <5, for example 1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc. When the ratio is too small, it is not conducive to the formation of secondary particles, thereby not conducive to improve the rate performance of the graphite negative active material. When the ratio is too large, it will make the particles between the adhesion is too much, leading to the graphite negative active material processing is poor.

[0052] In some embodiments, O is 50-100 mL / 100g, for example 50 mL / 100g, 55 mL / 100g, 60 mL / 100g, 65 mL / 100g, 70 mL / 100g, 75 mL / 100g, 80 mL / 100g, 85 mL / 100g, 90 mL / 100g, 95 mL / 100g, 100 mL / 100g, etc., and can be selected to be 55-85 mL / 100g. When the oil absorption value O of the graphite negative active material is too large, it will make the battery impedance is large, thereby not conducive to improve the electrochemical performance of the battery, for example, the cycle performance.

[0053] In some embodiments, T is 0.80-1.20 g / cm 3 , for example 0.80 g / cm 3 , 0.85 g / cm 3 , 0.90 g / cm 3 , 0.95 g / cm3 1.00 g / cm 3 1.05 g / cm 3 1.10 g / cm 3 1.15 g / cm 3 1.20 g / cm 3 and so on, and can be 0.85-1.10 g / cm 3 When the tap density T of the graphite negative electrode active material is too small, the processability of the material will be poor, and especially in the sizing stage of the battery cell process, the material is prone to sedimentation.

[0054] In some embodiments, the orientation degree OI is 2-11, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and so on, and can be 3-8. When the orientation degree OI of the graphite negative electrode active material is too large, it is not conducive to improving the cycle performance of the battery cell.

[0055] In a second aspect, the embodiments of the present application provide a preparation method of a graphite negative electrode active material, comprising the following steps:

[0056] S101. Pre-treating raw materials to obtain pre-treated materials; then grinding and optionally shaping the pre-treated materials to obtain aggregates; optionally, high-temperature calcining the aggregates to obtain high-temperature calcined aggregates;

[0057] S201. Mixing the aggregates and / or the calcined aggregates with a binder and a solvent to obtain a mixture; then making the mixture into a centimeter-level granular material at room temperature; and drying the granular material to obtain a dried granular material;

[0058] S301. Graphitizing the dried granular material to obtain a graphitized granular material;

[0059] S401. Breaking the graphitized granular material and processing the broken material into a finished product to obtain a finished product of the graphite negative electrode active material.

[0060] The granulation process in the related art uses pitch, and is heated at about 600°C to bond micron-level aggregates and / or calcined aggregate small particles into micron-level large particles that are slightly larger, and still a powder from a naked eye observation. Then the powder is graphitized again.

[0061] The step S201 of the preparation method of the embodiment of the present application is to make the mixture of the aggregate and / or the calcined aggregate and the binder and the solvent into a centimeter-level granular material, and then the dry granular material is subjected to graphitization treatment through the step S301 to obtain a graphitized granular material. The granulation process in the preparation method of the embodiment of the present application can be carried out at room temperature without heating process, and the micron-level powder is made into a centimeter-level granular material. The bonding process in the preparation method of the embodiment of the present application occurs in the graphitization treatment stage.

[0062] Compared with the production process disclosed in the related art, the preparation method of the embodiment of the present application does not have a heating granulation process, the process and equipment are simple, and it has cost advantage, and meanwhile it can be adapted to all raw materials. In addition, in the absence of the heating granulation process of the step S201, the preparation method of the embodiment of the present application can make the centimeter-level granular material through the step S201, which can have an effect better than the heating granulation process, so that the graphite negative electrode active material has more graphite layer end faces exposed, which is beneficial to the lithium ion deintercalation, and has higher rate performance and cycle performance. In addition, the preparation method of the embodiment of the present application can control the particle size Dv50 成品 of the aggregate to control whether the finished product is a primary particle or a secondary particle according to the size of the particle size Dv50 骨料 of the aggregate, so as to realize customized production and meet different needs of customers.

[0063] In some embodiments, in the step S101, the pretreatment can include at least one of the following processes: crushing, drying, and low-temperature calcination treatment. If the pretreatment includes crushing, the raw material can be crushed to have a particle size Dv50 less than or equal to 5 mm, if the pretreatment includes drying, the crushed material can be dried to have a moisture content less than or equal to 2%, and if the pretreatment includes low-temperature calcination treatment, the holding temperature of the low-temperature calcination treatment can be 450-800℃.

[0064] In some embodiments, in the step S101, a pulverizer can be used to pulverize the pretreated material. The shaping process is a common process in the graphite industry, and the principle of shaping is to put the pulverized material into a shaper again to make the material rub against each other, so as to remove the edges and corners of the material particles, and then part of the fine powder is removed through classification. In the step S101, if only the pulverization is performed without shaping, the material obtained after the pulverization is the aggregate, and the pulverization particle size D50 磨粉 is the aggregate particle size Dv50 骨料 ; if the pulverization and shaping are performed, the material obtained after the shaping is the aggregate, and the shaping particle size D50 整形 is the aggregate particle size Dv50 骨料 .

[0065] In some embodiments, in the step S101, the particle size Dv50磨粉 may be 3-9 μm, for example 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc.; the particle size Dv50 after the shaping treatment 整形 may be 5-10 μm, for example 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc., and may be 7-10 μm.

[0066] In some embodiments, in step S101, the high-temperature calcination treatment is a common means for the negative active material, and can remove volatile impurities in the raw material, so that the graphitization loading is larger. In the embodiments of the present application, the high-temperature calcination treatment can make the volatile of the raw material very small, so that more raw materials can be added when the binder is added in step S102. Of course, it is also possible not to perform the high-temperature calcination treatment, but the formulation of the binder added in the raw material with different volatiles may be different.

[0067] In some embodiments, in step S201, the binder can be at least one of starch and pitch. The starch can include but is not limited to at least one of the following: corn starch, potato starch, gelatinized starch, etc. The pitch can include but is not limited to at least one of the following: oil-based pitch with a softening point of 70-350°C, coal-based pitch, and may be oil-based pitch with a softening point of 150-230°C.

[0068] In some embodiments, in step S201, the solvent can be deionized water, etc. The mixing time can be 1-180 min, for example 1 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, etc., and may be 10-30 min.

[0069] In some embodiments, in step S201, an extrusion device can be used to prepare the granular material, and the shape of the granular material is not particularly limited, for example, can be at least one of a cylinder, a sphere, and an ellipsoid.

[0070] In some embodiments, in step S201, the particle size of the granular material is 1-50 cm, for example 1 cm, 2 cm, 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 45 cm, 50 cm, etc., and may be 3-10 cm. When the particle size of the granular material is too small, the production efficiency of the device for preparing the granular material will be reduced, and it is not conducive to transportation and drying. When the particle size of the granular material is too large, it is not conducive to the loading or operation of the graphitization treatment, and the production efficiency of the graphitization treatment will be reduced.

[0071] In some embodiments, in step S201, the holding temperature for drying can be 50-300°C, such as 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, or the like, and can be optionally 80-150°C; the holding time for drying can be 2-24h, such as 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or the like, and can be optionally 3-8h.

[0072] If drying is not performed in step S201, the following two hazards can occur. First, if the material is not dried, it is in a wet granular material state, and the material strength is poor, which can cause the material to be pulverized more during transportation and loading into a crucible or other graphitization furnace, and is not conducive to the subsequent preparation of secondary granules. Second, in step S201, the aggregate and / or the calcined aggregate are added with a binder and a solvent to prepare a centimeter-level granular material, and a large amount of solvent is added in this process. If the centimeter-level granular material is not dried and is directly put into a graphitization furnace, a large amount of solvent vapor will be volatilized during graphitization, which will cause great harm to the graphitization furnace, and at the same time, a large amount of gas is also released, which is easy to cause safety accidents.

[0073] According to the preparation method of the embodiments of the present application, since the binder is added in step S201, the material obtained after the graphitization treatment in step S301 can be soft carbon and / or hard carbon coated graphite.

[0074] In some embodiments, in step S301, the holding temperature for graphitization treatment can be 2400-3500°C, such as 2400°C, 2450°C, 3000°C, 3050°C, 3100°C, 3150°C, 3200°C, 3250°C, 3300°C, 3350°C, 3400°C, 3450°C, 3500°C, or the like, and can be optionally 2600-3300°C.

[0075] In some embodiments, the crushing equipment used for crushing in step S401 can include, but is not limited to, a mechanical mill, a shaping fusion machine, a depolymerization machine, a stone mill, a double-roller crusher, etc. The finished product processing in step S401 mainly includes material mixing, screening, magnetic removal, and packaging. It should be understood that although the same equipment parameters are used for the production of the graphite negative electrode active material, the particle size of the crushed material can be non-uniform, and in the negative electrode industry, the materials can be mixed before being prepared into finished products to ensure the uniformity of the materials. The mixing time here can be 10-300min, such as 10min, 30min, 50min, 80min, 100min, 120min, 150min, 200min, 220min, 250min, 280min, 300min, or the like, and can be optionally 30-180min.

[0076] In some embodiments, in step S401, Dv50 成品 is 6-25 μm; and / or, 1.2≤Dv50 成品 / Dv50 骨料 <5; and / or, O is 50-100 mL / 100g; and / or, T is 0.80-1.20 g / cm 3 ; and / or, OI is 2-11.

[0077] In a third aspect, the embodiments of the present application provide a method for evaluating the rate capability of a graphite negative active material, comprising the following steps:

[0078] S1. Setting the rate capability index of the graphite negative active material as W, W=(OXTDv50 成品 ) / (OIxDv50 骨料 ); wherein, O is the oil absorption value of the graphite negative active material, in units of mL / 100g; T is the tap density of the graphite negative active material, in units of g / cm 3 ; Dv50 成品 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the graphite negative active material, in units of μm; OI is the orientation degree of the graphite negative active material; Dv50 骨料 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the aggregate used by the graphite negative active material, in units of μm;

[0079] S2. Calculating W according to O, T, Dv50 成品 , OI and Dv50 骨料 .

[0080] S3. When W≥3.0, judging that the graphite negative active material is a high-rate capability negative active material; when W<3.0, judging that the graphite negative active material is a low-rate capability negative active material.

[0081] The evaluation method of the embodiments of the present application finds the relationship between the five core parameters of the oil absorption value, the tap density, the finished product particle size, the orientation degree and the aggregate particle size of the graphite negative active material and the rate capability of the graphite negative active material by comprehensively considering the influence of the five core parameters on the rate capability of the graphite negative active material, and uses the W value to represent the pros and cons of the rate capability of the graphite negative active material. Therefore, by using the evaluation method of the embodiments of the present application, the pros and cons of the rate capability of the graphite negative active material can be quickly predicted before assembling into a test battery, and the judgment result is accurate. There is no need to assemble into a test battery to test the rate capability, which is beneficial to save time, improve efficiency and facilitate the rapid progress of the selection work.

[0082] In some embodiments, the larger the W, the higher the rate capability of the graphite negative electrode active material. The evaluation method of the embodiments of the present application can be used to compare the relative size of the rate capability between two or more graphite negative electrode active materials according to the above rule.

[0083] In a fourth aspect, the embodiments of the present application provide a secondary battery. The secondary battery of the embodiments of the present application is described below.

[0084] [Positive electrode tab]

[0085] The positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0086] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of itself, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0087] The positive electrode film layer includes a positive electrode active material. The positive electrode active material can be selected from materials capable of absorbing and releasing lithium.

[0088] The specific type of positive electrode active material is not particularly limited and can be selected as needed. As an example, the positive electrode active material can include, but is not limited to, lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), iron pyrophosphate (Li2FeP2O7), lithium cobaltate (LiCoO2), spinel lithium manganate (LiMn2O4), spinel lithium nickel manganate (LiNi 0.5 Mn 1.5 O4), layered lithium manganate (LiMnO2), lithium nickelate (LiNiO2), lithium niobate (LiNbO2), lithium ferrate (LiFeO2), lithium magnesiumate (LiMgO2), lithium calciumate (LiCaO2), lithium cuprate (LiCuO2), lithium zincate (LiZnO2), lithium molybdate (LiMoO2), lithium tantalate (LiTaO2), lithium tungstate (LiWO2), lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example, LiNi 0.8 Co 0.15 Al 0.05 O2), lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2, 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.), lithium-rich materials (e.g., lithium-rich nickel cobalt manganese oxide), manganese oxide (MnO2), vanadium oxide, sulfide oxide, silicate oxide, and each modified compound thereof. These materials can be used alone or in combination with two or more.

[0089] The modified compound of each of the above positive electrode active materials can be a doping modification, a surface coating modification, or a doping and coating simultaneous modification of the positive electrode active material.

[0090] In some embodiments, the positive current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin.

[0092] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode tab can be prepared by dispersing the above components for preparing the positive electrode tab, e.g., the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and subjecting to a drying, cold pressing, or the like process to obtain the positive electrode tab.

[0094] [Negative electrode tab]

[0095] The negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises the negative electrode active material of the embodiments of the present application.

[0096] For example, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0097] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the negative electrode film layer can further optionally comprise a binder. The binder can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0099] In some embodiments, the negative electrode film layer can further optionally comprise a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the negative electrode film layer can further optionally comprise other auxiliary agents, such as thickening agents (such as sodium carboxymethyl cellulose (CMC-Na), etc.

[0101] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and then performing processes such as drying, cold pressing, etc. to obtain the negative electrode sheet.

[0102] [Electrolyte]

[0103] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The embodiments of the present application do not have specific limitations on the type of electrolyte, which can be selected according to the needs. For example, the electrolyte can be in a liquid state, a gel state, or a full solid state.

[0104] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0105] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0106] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0107] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0108] [Separator]

[0109] In some embodiments, the secondary battery further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0110] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0111] The present application will be described in detail below with reference to examples and accompanying drawings.

[0112] The main material information used in the following examples and comparative examples is as follows:

[0113] Petroleum coke green coke was purchased from Anqing Petrochemical; needle coke green coke was purchased from Jinzhou Petrochemical, Shandong Yida, and Philips; starch was purchased from Zhenchao Starch; pitch was purchased from Xinxin New Material; polyvinylidene fluoride (PVDF) was analytical pure and purchased from Aldrich; and N-methyl pyrrolidone (NMP) was analytical pure and purchased from Aldrich.

[0114] Example 1

[0115] The preparation method of the graphite anode active material in this embodiment includes the following specific steps:

[0116] S101.① The needle coke raw coke purchased from Jinzhou Petrochemical is crushed until all particles can pass through a sieve with a 1cm×1cm aperture, and dried in a rotary kiln at a temperature of 150℃ for 2 hours to obtain coke powder A.

[0117] ② The coke powder A is calcined at a low temperature in a pusher kiln, with a maximum temperature of 500℃ and a holding time of 8 hours, to obtain low-temperature calcined powder B;

[0118] ③ Grind the low-temperature calcined powder B into powder using a roller mill, with a particle size of Dv50. 磨粉 The particle size is 7.6μm. After grinding, it is shaped using an 800 shaping machine to a particle size of Dv50. 整形 The particle size was 8.7 μm, resulting in shaping powder C, which is the aggregate, with a shaping particle size Dv50. 整形 This refers to the aggregate particle size Dv50. 骨料 ;

[0119] ④ The shaped powder C is calcined at high temperature in a tunnel kiln. The high-temperature calcination process is as follows: 100 min to 500℃, 500℃ for 100 min, 140 min to 1200℃, 1200℃ for 600 min, 300 min to 600℃, 600 min to room temperature and discharged to obtain high-temperature calcined powder D;

[0120] S102. Mix high-temperature calcined powder D with asphalt, starch and pure water in a mass ratio of 100:12:8:55, extrude the mixture into a 7-10cm long shaped material using a coal briquette machine, and dry it at 150℃ for 8 hours to obtain granular material E.

[0121] S103. Graphitize the particulate material E in a medium-frequency continuous furnace at a graphitization temperature of 3100℃ and a holding time of 4h to obtain graphitized material F.

[0122] S104. The graphitized material F is crushed to a finished particle size Dv50 using a shaping and fusion machine. 成品 The particle size is 14.7 μm. After being mixed evenly, the particles are sieved and demagnetized to obtain the finished product of artificial graphite secondary particle negative electrode active material.

[0123] The physical parameters Dv50 of the graphite anode active material obtained in this embodiment are as follows: 骨料 Dv50 成品 O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1. The SEM images of the graphite anode active material obtained in this embodiment at 1000x and 2000x magnification are shown in Figure 1 and Figure 2, respectively.

[0124] Example 2

[0125] The preparation method of the graphite anode active material in this embodiment includes the following specific steps:

[0126] S101.① The needle-shaped raw coke purchased from Shandong Yida is crushed until all particles can pass through a sieve with a 1cm×1cm aperture, and dried in a rotary kiln at a temperature of 150℃ for 2 hours to obtain coke powder A.

[0127] ② The coke powder A is calcined at a low temperature in a pusher kiln, with a maximum temperature of 500℃ and a holding time of 8 hours, to obtain low-temperature calcined powder B;

[0128] ③ Grind the low-temperature calcined powder B into powder using a roller mill, with a particle size of Dv50. 磨粉 The particle size is 7.9μm. After grinding, it is shaped using an 800 shaping machine to a particle size of Dv50. 整形 The particle size was 8.5 μm, resulting in shaping powder C, which is the aggregate, with a shaping particle size Dv50. 整形 This refers to the aggregate particle size Dv50. 骨料 ;

[0129] ④ The shaped powder C is calcined at high temperature in a tunnel kiln. The high-temperature calcination process is as follows: 100 min to 500℃, 500℃ for 100 min, 140 min to 1200℃, 1200℃ for 600 min, 300 min to 600℃, 600 min to room temperature and discharged to obtain high-temperature calcined powder D;

[0130] S102. Mix high-temperature calcined powder D with asphalt, starch and pure water in a mass ratio of 100:12:8:55, extrude the mixture into a 7-10cm long shaped material using a coal briquette machine, and dry it at 150℃ for 8 hours to obtain granular material E.

[0131] S103. Graphitize the particulate material E in a medium-frequency continuous furnace at a graphitization temperature of 3100℃ and a holding time of 4h to obtain graphitized material F.

[0132] S104. Crush the graphitized material F to the finished particle size Dv50. 成品 The particle size is 15.2 μm. After being mixed evenly, the particles are sieved and demagnetized to obtain the finished product of artificial graphite secondary particle negative electrode active material.

[0133] The physical parameters Dv50 of the graphite anode active material obtained in this embodiment are as follows: 骨料 Dv50 成品 O, OI, T, W, Dv50 成品 / Dv50 骨料See Table 1. The SEM images of the graphite anode active material obtained in this embodiment at 1000x and 2000x magnification are shown in Figures 3 and 4, respectively.

[0134] Example 3

[0135] The preparation method of the graphite anode active material in this embodiment includes the following specific steps:

[0136] S101.①Purchased needle coke GHBA-0 raw coke from Philips was crushed until all particles could pass through a sieve with a 1cm×1cm aperture, and dried in a rotary kiln at a temperature of 150℃ for 2 hours to obtain coke powder A.

[0137] ② The coke powder A is calcined at a low temperature in a pusher kiln, with a maximum temperature of 500℃ and a holding time of 8 hours, to obtain low-temperature calcined powder B;

[0138] ③ Grind the low-temperature calcined powder B into powder using a roller mill, with a particle size of Dv50. 磨粉 The particle size is 7.3μm. After grinding, it is shaped using an 800 shaping machine to a particle size of Dv50. 整形 The particle size was 8.6 μm, resulting in shaping powder C, which is the aggregate, with a shaping particle size Dv50. 整形 This refers to the aggregate particle size Dv50. 骨料 ;

[0139] ④ The shaped powder C is calcined at high temperature in a tunnel kiln. The high-temperature calcination process is as follows: 100 min to 500℃, 500℃ for 100 min, 140 min to 1200℃, 1200℃ for 600 min, 300 min to 600℃, 600 min to room temperature and discharged to obtain high-temperature calcined powder D;

[0140] S102. Mix high-temperature calcined powder D with asphalt, starch and pure water in a mass ratio of 100:12:8:55, extrude the mixture into a 7-10cm long shaped material using a coal briquette machine, and dry it at 150℃ for 8 hours to obtain granular material E.

[0141] S103. Graphitize the particulate material E in a medium-frequency continuous furnace at a graphitization temperature of 3100℃ and a holding time of 4h to obtain graphitized material F.

[0142] S104. Crush the graphitized material F to the finished particle size Dv50. 成品 The particle size is 14.5 μm. After being mixed evenly, the particles are sieved and demagnetized to obtain the finished product of artificial graphite secondary particle negative electrode active material.

[0143] The physical parameters Dv50 of the graphite anode active material obtained in this embodiment are as follows: 骨料 Dv50 成品 O, OI, T, W, Dv50 成品Dv50 骨料 See Table 1, the SEM images of the graphite negative electrode active material obtained in this embodiment at 1000 times and 2000 times are shown in Figures 5 and 6, respectively.

[0144] Example 4

[0145] The preparation method of the graphite negative electrode active material in this embodiment is as follows:

[0146] S101. ①The petroleum coke purchased from Anqing Petrochemical was crushed to all particles passing through a sieve with a pore size of 1 cm x 1 cm, and was dried in a rotary kiln with a temperature setting of 150°C for 2h to obtain coke powder A;

[0147] ②The coke powder A was calcined at low temperature in a push plate kiln with a maximum temperature of 500°C for 8h to obtain low-temperature calcined powder B;

[0148] ③The calcined powder B was ground by roller pressing grinding, and the ground powder had a particle size Dv50 磨粉 of 8.9μm, and was shaped by an 800 shaper after grinding, and the shaped powder had a particle size Dv50 整形 of 9.8μm to obtain shaped powder C, and the shaped particle size Dv50 整形 was the aggregate particle size Dv50 骨料 ;

[0149] ④The shaped powder C was calcined at high temperature in a tunnel kiln, and the high-temperature calcination process was as follows: 100min to 500°C, 500°C for 100min, 140min to 1200°C, 1200°C for 600min, 300min to cool to 600°C, 600min to cool to room temperature to discharge, to obtain high-temperature calcined powder D;

[0150] S102. The high-temperature calcined powder D was mixed uniformly with pitch, starch, and pure water at a mass ratio of 100:12:8:48, and was extruded into a length of 7-10cm by a coal rod machine, and was dried at 150°C for 8h to obtain granular material E;

[0151] S103. The granular material E was graphitized by a medium-frequency continuous furnace at a graphitization temperature of 3100°C for 4h to obtain graphitized material F;

[0152] S104. The graphitized material F was crushed to a finished product particle size Dv50 成品 of 13.5μm, and was screened and removed of magnetism after being mixed uniformly to obtain the finished product of artificial graphite secondary particle negative electrode active material.

[0153] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50成品 / Dv50 骨料 See Table 1, SEM images of the graphite negative electrode active material obtained in this example at 1000 times and 2000 times are shown in FIG. 7 and FIG. 8, respectively.

[0154] Example 5

[0155] This example is the same as Example 1, except that:

[0156] Step S104 increases the host frequency of the size-regulating fusion machine so that the particle size Dv50 成品 is controlled to be 11.5 μm;

[0157] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1.

[0158] Example 6

[0159] This example is the same as Example 2, except that:

[0160] Step S104 increases the host frequency of the size-regulating fusion machine so that the particle size Dv50 成品 is controlled to be 11.0 μm;

[0161] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1.

[0162] Example 7

[0163] This example is the same as Example 3, except that:

[0164] Step S104 increases the host frequency of the size-regulating fusion machine so that the particle size Dv50 成品 is controlled to be 11.3 μm;

[0165] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1.

[0166] Example 8

[0167] This example is the same as Example 4, except that:

[0168] Step S104 adjusts the host frequency of the shaping and fusing machine so that the finished product particle size Dv50 is controlled to be 11.5 μm. 成品 成品

[0169] The physical parameters Dv50, Dv50, O, OI, T, W, Dv50 / Dv50 of the graphite negative electrode active material obtained in this example are shown in Table 1. 骨料 成品 成品 骨料 See Table 1.

[0170] Example 9

[0171] This example is the same as Example 1, except that:

[0172] The ground powder particle size Dv50 in Step S1013 was 4.1 μm, and the shaped particle size Dv50 was 5.2 μm. 磨粉 整形

[0173] Step S104 adjusts the host frequency of the shaping and fusing machine so that the finished product particle size Dv50 is controlled to be 15.6 μm.

[0174] The physical parameters Dv50, Dv50, O, OI, T, W, Dv50 / Dv50 of the graphite negative electrode active material obtained in this example are shown in Table 1. 骨料 成品 成品 骨料 See Table 1.

[0175] Example 10

[0176] This example is the same as Example 2, except that:

[0177] The ground powder particle size Dv50 in Step S1013 was 4.3 μm, and the shaped particle size Dv50 was 5.1 μm. 磨粉 整形

[0178] Step S104 adjusts the host frequency of the shaping and fusing machine so that the finished product particle size Dv50 is controlled to be 14.8 μm. 成品

[0179] The physical parameters Dv50, Dv50, O, OI, T, W, Dv50 / Dv50 of the graphite negative electrode active material obtained in this example are shown in Table 1. 骨料 成品 成品 骨料 See Table 1.

[0180] Example 11

[0181] This example is the same as Example 3, except that:​​​​​​​​​​​​​​

[0182] Step S1013 grinding particle size Dv50 磨粉 was 4.2 μm, and the shaping particle size Dv50 整形 was 5.4 μm;

[0183] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 14.7 μm;

[0184] The graphite negative electrode active material obtained in this example has the physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1.

[0185] Example 12

[0186] This example is the same as Example 4, except that:

[0187] Step S1013 grinding particle size Dv50 磨粉 was 4.0 μm, and the shaping particle size Dv50 整形 was 4.9 μm;

[0188] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 13.5 μm;

[0189] The graphite negative electrode active material obtained in this example has the physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1.

[0190] Example 13

[0191] This example is the same as Example 9, except that:

[0192] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 6.3 μm;

[0193] The graphite negative electrode active material obtained in this example has the physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 See Table 1.

[0194] Example 14

[0195] This example is the same as Example 9, except that:

[0196] Step S104 adjusts the host frequency of the shaping and fusing machine so that the finished product particle size Dv50 成品 is controlled to be 20.1 μm;

[0197] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this example are shown in Table 1.

[0198] Example 15

[0199] This example is the same as Example 9, except that:

[0200] Step S104 adjusts the host frequency of the shaping and fusing machine so that the finished product particle size Dv50 成品 is controlled to be 25.5 μm;

[0201] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this example are shown in Table 1.

[0202] Example 16

[0203] This example is the same as Example 1, except that:

[0204] Step S101 adjusts the particle size Dv50 磨粉 of the ground powder to be 2.7 μm, and the shaping particle size Dv50 整形 is controlled to be 3.2 μm;

[0205] Step S104 adjusts the host frequency of the shaping and fusing machine so that the finished product particle size Dv50 成品 is controlled to be 15.5 μm;

[0206] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this example are shown in Table 1.

[0207] Comparative Example 1

[0208] This comparative example is the same as Example 1, except that:

[0209] Step S102 adjusts the ratio of high-temperature calcined powder D, pitch, starch, and pure water to be 100:0:6:45.

[0210] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 8.4 μm;

[0211] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this comparative example are shown in Table 1.

[0212] Comparative Example 2

[0213] This comparative example is the same as Example 2, except that:

[0214] Step S102 adjusts the ratio of high-temperature calcined powder D, pitch, starch, and pure water to be 100:0:6:45.

[0215] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 8.0 μm;

[0216] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this comparative example are shown in Table 1.

[0217] Comparative Example 3

[0218] This comparative example is the same as Example 3, except that:

[0219] Step S102 adjusts the ratio of high-temperature calcined powder D, pitch, starch, and pure water to be 100:0:6:45.

[0220] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 8.2 μm;

[0221] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this comparative example are shown in Table 1.

[0222] Comparative Example 4

[0223] The comparative example is the same as example 4, except that:

[0224] Step S102 adjusts the ratio of high-temperature calcined powder D, pitch, starch, and pure water to be 100:0:6:39;

[0225] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 9.2 pm;

[0226] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained by the comparative example are seen in Table 1.

[0227] Comparative example 5

[0228] The comparative example is the same as example 9, except that:

[0229] Step S102 adjusts the ratio of high-temperature calcined powder D, pitch, starch, and pure water to be 100:0:6:45;

[0230] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 5.0 pm;

[0231] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained by the comparative example are seen in Table 1.

[0232] Comparative example 6

[0233] The comparative example is the same as example 10, except that:

[0234] Step S102 adjusts the ratio of high-temperature calcined powder D, pitch, starch, and pure water to be 100:0:6:45;

[0235] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 5.3 pm;

[0236] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained by the comparative example are seen in Table 1.

[0237] Comparative Example 7

[0238] This comparative example is the same as Example 11, except that:

[0239] Step S102 adjusts the ratio of high-temperature calcined powder D to pitch, starch, and pure water to be 100:0:6:45;

[0240] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 5.1 pm;

[0241] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this comparative example are seen in Table 1.

[0242] Comparative Example 8

[0243] This comparative example is the same as Example 12, except that:

[0244] Step S102 adjusts the ratio of high-temperature calcined powder D to pitch, starch, and pure water to be 100:0:6:39;

[0245] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 4.7 pm;

[0246] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this comparative example are seen in Table 1.

[0247] Comparative Example 9

[0248] This comparative example is the same as Comparative Example 1, except that:

[0249] Step S102 adjusts the powder particle size Dv50 磨粉 to be 18.4 pm, and the shaping particle size Dv50 整形 to be 19.5 pm;

[0250] Step S104 adjusts the host frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 19.9 pm;

[0251] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50成品 / Dv50 骨料 See Table 1.

[0252] Comparative Example 10

[0253] This comparative example is the same as Comparative Example 1, except that:

[0254] Step S102 grinding particle size Dv50 磨粉 is 24.1 pm, and the shaped particle size Dv50 整形 is 25.1 pm;

[0255] Step S104 adjusting the main frequency of the shaping fusion machine so that the finished product particle size Dv50 成品 is controlled to be 25.6 pm;

[0256] The physical parameters Dv50 骨料 , Dv50 成品 , O, OI, T, W, Dv50 成品 / Dv50 骨料 of the graphite negative electrode active material obtained in this comparative example are shown in Table 1.

[0257] The physical parameters of the graphite negative electrode active materials of Examples 1-16 and Comparative Examples 1-10 are obtained by the following tests:

[0258] (1) The aggregate particle size Dv50 骨料 of the graphite negative electrode active material and the finished product particle size Dv50 成品 are measured by a Malvern Mastersizer 3000 using a laser method.

[0259] (2) The tap density of the graphite negative electrode active material is measured by a Dandong Baiter BT-313 tap density tester.

[0260] (3) The oil absorption value O of the graphite negative electrode active material is measured by a Japan ASAHI, S-500 type oil absorption tester, specifically the volume of dibutyl phthalate absorbed by 100 g of the graphite negative electrode active material under specified test conditions.

[0261] (4) The orientation degree OI of the graphite negative electrode active material is a parameter describing the degree of order of the arrangement of graphite layers in the graphite negative electrode active material, and is measured by a Panalytical Aeris XRD, specifically the ratio of the peak area of the 004 characteristic diffraction peak to the peak area of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the graphite negative electrode active material powder.

[0262] (5) According to W = (O x T x Dv50 成品 ) / (OI x Dv50 骨料) the rate performance index W of the graphite negative electrode active material; in addition, the ratio Dv50 成品 / Dv50 骨料 of Dv50 成品 and Dv50 骨料 .

[0263] (6) The scanning electron microscope pictures of the graphite negative electrode active material were measured using a Japanese Electron JSM-7900F.

[0264] Performance test:

[0265] 1) The first lithium intercalation capacity, the first lithium extraction capacity and the first efficiency of the graphite negative electrode active material were measured using a Shenzhen Xinwei button battery test system, and the test method was as follows: the graphite negative electrode active material was made into an electrode sheet, a lithium sheet was used as a counter electrode, an electrolyte was added, and a CR2032 button battery was assembled in a vacuum glove box, 0.1C was discharged to 0.005V, and 20μA was discharged to 0.005V after 120min of standing, the first lithium intercalation capacity of the material was obtained, and the first lithium extraction capacity of the material was obtained after 120min of standing and 0.1C charging to 2.0V to complete the first cycle. The ratio of the first lithium extraction capacity to the first lithium intercalation capacity is the first efficiency. The test results of the first lithium intercalation capacity and the first efficiency of the graphite negative electrode active material of each example and the comparative example are shown in Table 1.

[0266] 2) The normal temperature 3C constant current SOC test of the graphite negative electrode active material was determined on the button battery test system of Shenzhen Xinwei using the button battery whose first lithium extraction capacity was tested in 1), and the determination procedure was as follows: the button battery tested in 1) was discharged at 3C constant current to 0.005V, the lithium intercalation capacity of the material under this condition was obtained, and the ratio of this value to the first lithium extraction capacity was the normal temperature 3C constant current SOC, i.e., the 3C fast charging capacity. The test results of the 3C fast charging capacity of the graphite negative electrode active material of each example and the comparative example are shown in Table 1.

[0267] Table 1. Physical parameters and performance test results of the graphite negative electrode active material of Examples 1-16 and Comparative Examples 1-10

[0268] As can be seen from Examples 1-16 in Table 1, by controlling the material finished product particle size Dv50 成品 , aggregate particle size Dv50 骨料 , oil absorption value O, orientation degree OI and tap density T during the preparation process of the graphite negative electrode active material, W≥3.0, which can significantly improve the rate performance of the graphite negative electrode active material; and the greater W is, the higher the rate performance of the graphite negative electrode active material is.

[0269] As can be seen from the comparative examples 1-10 in Table 1, when the rate capability index W of the graphite negative electrode active material is less than 3.0, the 3C fast charging capacity is less than that of the examples 1-16, indicating that the rate capability of the graphite negative electrode active material prepared in the comparative examples is poor.

[0270] As can be seen from the scanning electron microscope images 1-8 of the examples 1-4, the graphite negative electrode active material prepared by the preparation method of the examples 1-16 is mainly secondary particles.

[0271] As can be seen from the comparison of the examples 1-4 in Table 1, the rate capability of the graphite negative electrode active material of the example 4 is slightly lower than that of the examples 1-3, which is caused by the larger aggregate particle size Dv50 骨料 and the smaller finished product particle size Dv50 成品 of the example 4.

[0272] As can be seen from the comparison of the example 6 and the example 7 in Table 1, the rate capability index W of the graphite negative electrode active material of the example 6 is 0.1 larger than that of the example 7, and the 3C fast charging capacity is 0.01% smaller than that of the example 7, indicating that the rate capability of the example 6 is slightly worse than that of the example 7, which is caused by the different raw materials used in the two examples and the too close W value and the error in the test process.

[0273] As can be seen from the comparison of the example 9 and the example 16 in Table 1, the finished product particle size Dv50 成品 is roughly the same, the aggregate particle size Dv50 骨料 is smaller, and the rate capability of the graphite negative electrode active material is better. In addition, the example 16 shows that although the aggregate particle size Dv50 骨料 is not within the optional range of 5-10 μm, the rate capability index W of the graphite negative electrode active material is greater than or equal to 3, so the graphite negative electrode active material still exhibits excellent rate capability, which can indicate that when the rate capability index W of the graphite negative electrode active material is greater than or equal to 3, the material is basically a high-rate capability material, but due to the too small aggregate particle size Dv50 骨料 of the example 16, the efficiency and the material yield in the grinding and shaping process are both low, which is not conducive to reducing the production cost of the graphite negative electrode active material. Therefore, in practical applications, it is not required that the rate capability of the battery is higher and higher, but the overall performance of the battery needs to be considered to design a battery with good overall performance.

[0274] As can be seen from the comparison of the example 13 and the other examples in Table 1, the rate capability of the graphite negative electrode active material of the example 13 is relatively low, which is caused by the close Dv50 成品 and Dv50 骨料 of the example 13, and at the same time, the small Dv50 成品 is not conducive to improving the efficiency in the finished product processing.

[0275] As can be seen from the comparison of Example 15 and other examples in Table 1, the graphite negative electrode active material of Example 15 exhibits more excellent rate performance than other examples, but the processing performance of the graphite negative electrode active material of Example 15 is poor, and the graphite negative electrode active material is prone to agglomeration when the slurry of the battery is prepared, and the surface density of the electrode sheet is unstable when the electrode sheet is prepared, which is caused by the small tap density. Therefore, in practical application, it is not required that the higher the rate performance of the battery is, the better, but the performance of other aspects needs to be considered comprehensively, and a battery with good comprehensive performance is designed.

[0276] As can be seen from the comparison of each example and the comparative example in Table 1, even if the graphite negative electrode active materials prepared from different raw materials, the rate performance index W is the same, that is, the larger the W is, the higher the rate performance of the graphite negative electrode active material is, which shows that the rate performance index W proposed in the application can be adapted to various raw materials.

[0277] Application Example 1

[0278] The rate performance of the graphite negative electrode active material prepared in Example 1 is evaluated, and the evaluation method is as follows:

[0279] S1. The rate performance index of the graphite negative electrode active material is set as W, W = (O x T x Dv50 成品 ) / (OI x Dv50 骨料 ); wherein O is the oil absorption value of the graphite negative electrode active material, unit: mL / 100g; T is the tap density of the graphite negative electrode active material, unit: g / cm 3 ; Dv50 成品 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the graphite negative electrode active material, unit: μm; OI is the orientation degree of the graphite negative electrode active material; Dv50 骨料 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the aggregate used by the graphite negative electrode active material, unit: μm;

[0280] S2. According to O, T, Dv50 成品 , OI and Dv50 骨料 , W is calculated, and W is shown in Table 1;

[0281] S3. Since W≥3, it is judged that the graphite negative electrode active material of Example 1 is a high-rate performance negative electrode active material.

[0282] Application Example 2

[0283] The evaluation method of the rate performance of the graphite negative electrode active material of the application example is the same as that of Application Example 1, and the difference is that the evaluation object is the graphite negative electrode active material prepared in Example 2. Since W≥3, it is judged that the graphite negative electrode active material of Example 2 is a high-rate performance negative electrode active material.

[0284] Application Example 3

[0285] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 3. Since W≥3, the graphite negative electrode active material of example 3 is judged to be a high rate capability negative electrode active material.

[0286] Application Example 4

[0287] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 4. Since W≥3, the graphite negative electrode active material of example 4 is judged to be a high rate capability negative electrode active material.

[0288] Application Example 5

[0289] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 5. Since W≥3, the graphite negative electrode active material of example 5 is judged to be a high rate capability negative electrode active material.

[0290] Application Example 6

[0291] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 6. Since W≥3, the graphite negative electrode active material of example 6 is judged to be a high rate capability negative electrode active material.

[0292] Application Example 7

[0293] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 7. Since W≥3, the graphite negative electrode active material of example 7 is judged to be a high rate capability negative electrode active material.

[0294] Application Example 8

[0295] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 8. Since W≥3, the graphite negative electrode active material of example 8 is judged to be a high rate capability negative electrode active material.

[0296] Application Example 9

[0297] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 9. Since W≥3, the graphite negative electrode active material of example 9 is judged to be a high rate capability negative electrode active material.

[0298] Application Example 10

[0299] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 10. Since W≥3, the graphite negative electrode active material of example 10 is judged to be a high rate capability negative electrode active material.

[0300] Application Example 11

[0301] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 11. Since W≥3, the graphite negative electrode active material of example 11 is judged to be a high rate capability negative electrode active material.

[0302] Application Example 12

[0303] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 12. Since W≥3, the graphite negative electrode active material of example 12 is judged to be a high rate capability negative electrode active material.

[0304] Application Example 13

[0305] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 13. Since W≥3, the graphite negative electrode active material of example 13 is judged to be a high rate capability negative electrode active material.

[0306] Application Example 14

[0307] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 14. Since W≥3, the graphite negative electrode active material of example 14 is judged to be a high rate capability negative electrode active material.

[0308] Application Example 15

[0309] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 15. Since W≥3, the graphite negative electrode active material of example 15 is judged to be a high rate capability negative electrode active material.

[0310] Application Example 16

[0311] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 16. Since W≥3, the graphite negative electrode active material of example 16 is judged to be a high rate capability negative electrode active material.

[0312] Application Example 17

[0313] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 15. Since W<3, the graphite negative electrode active material of example 15 is judged to be a high rate capability negative electrode active material.

[0314] Application Example 18

[0315] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 15. Since W<3, the graphite negative electrode active material of example 15 is judged to be a high rate capability negative electrode active material.

[0316] Application Example 19

[0317] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 15. Since W<3, the graphite negative electrode active material of example 15 is judged to be a high rate capability negative electrode active material.

[0318] Application Example 20

[0319] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in example 15. Since W<3, the graphite negative electrode active material of example 15 is judged to be a high rate capability negative electrode active material.

[0320] Application Example 21

[0321] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in Comparative Example 5. Since W < 3, the graphite negative electrode active material of Comparative Example 5 is judged to be a low rate capability negative electrode active material.

[0322] Application Example 22

[0323] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in Comparative Example 6. Since W < 3, the graphite negative electrode active material of Comparative Example 6 is judged to be a low rate capability negative electrode active material.

[0324] Application Example 23

[0325] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in Comparative Example 7. Since W < 3, the graphite negative electrode active material of Comparative Example 7 is judged to be a low rate capability negative electrode active material.

[0326] Application Example 24

[0327] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in Comparative Example 8. Since W < 3, the graphite negative electrode active material of Comparative Example 8 is judged to be a low rate capability negative electrode active material.

[0328] Application Example 25

[0329] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in Comparative Example 9. Since W < 3, the graphite negative electrode active material of Comparative Example 9 is judged to be a low rate capability negative electrode active material.

[0330] Application Example 26

[0331] The evaluation method of the rate capability of the graphite negative electrode active material of the present application example is the same as that of application example 1, except that the evaluation object is the graphite negative electrode active material prepared in Comparative Example 10. Since W < 3, the graphite negative electrode active material of Comparative Example 10 is judged to be a low rate capability negative electrode active material.

[0332] The evaluation results of application examples 1 to 26 are compared with the measured results of the 3C fast charging capacity of the graphite negative electrode active materials of the foregoing examples 1 to 16 and comparative examples 1 to 10, and it can be seen that the 3C fast charging capacity of the graphite negative electrode active materials of examples 1 to 16 is 34% or more, and the rate performance is high, and the 3C fast charging capacity of the graphite negative electrode active materials of comparative examples 1 to 10 is 34% or less, and the rate performance is low, indicating that the evaluation results of application examples 1 to 26 are accurate.

[0333] In addition, the W calculated from application examples 1 to 26 is sorted by size, and it is found that the size sorting of W is basically consistent with the size sorting of the measured results of the 3C fast charging capacity of the graphite negative electrode active materials of the foregoing examples 1 to 16 and comparative examples 1 to 10, indicating that the following judgment standard is also correct: the larger the W, the higher the rate performance of the graphite negative electrode active material.

[0334] Therefore, the evaluation method of the rate performance of the graphite negative electrode active material of the present application can quickly evaluate the rate performance of the graphite negative electrode active material, and the evaluation result is accurate, which is convenient for researchers to select the graphite negative electrode active material, greatly saving the work load and shortening the working time.

[0335] In the present application, the terms "in some embodiments", "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the features of different embodiments or examples described in the specification without contradiction.

[0336] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it mutually exclusive or alternative to other embodiments. The skilled person in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0337] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A graphite negative active material, the rate capability index of the graphite negative active material being marked as W, W = (O x T x Dv50 成品 ) / (OI x Dv50 骨料 ), and W > 3.0; wherein, O is the oil absorption value of the graphite negative electrode active material, in units of mL / 100g; T is the tap density of the graphite negative electrode active material, in units of g / cm 3 ; Dv50 成品 is the particle size corresponding to the cumulative volume distribution percentage of the graphite negative electrode active material reaching 50%, in units of μm; OI is the orientation degree of the graphite negative electrode active material; Dv50 骨料 is the particle size corresponding to the cumulative volume distribution percentage of the aggregate used by the graphite negative electrode active material reaching 50%, in units of μm.

2. The graphite negative active material according to claim 1, wherein, W≥5.0。 3. The graphite negative active material according to claim 2, wherein, W≥30.0。 4. The graphite negative active material according to claim 3, wherein, W≥55.0。 5. The graphite negative active material according to any one of claims 1 to 4, wherein, Dv50 成品 6 to 25 pm; and / or, Dv50 骨料 5 to 10 pm; and / or, 1.2 < Dv50 成品 / Dv50 骨料 < 5; and / or, O is 50 to 100 mL / 100 g; and / or, T is 0.80 to 1.20 g / cm 3 ; and / or, OI is 2 to 11. 6.A method for preparing a graphite negative electrode active material, comprising the following steps: S101. Pre-treating raw materials to obtain pre-treated materials; Then, grinding and optionally shaping the pre-treated materials to obtain aggregates; optionally, high-temperature calcining the aggregates to obtain high-temperature calcined aggregates; S201. Mixing the aggregates and / or the calcined aggregates with a binder and a solvent to obtain a mixture; then, making the mixture into centimeter-level granular materials at room temperature; and drying the granular materials to obtain dried granular materials; S301. Graphitizing the dried granular materials to obtain graphitized granular materials; S401. Breaking the graphitized granular materials and processing the broken materials to obtain a finished product of the graphite negative electrode active material.

7. The production method according to claim 6, wherein Dv50 骨料 5 to 10 pm; and / or, Dv50 成品 6 to 25 pm; and / or, 1.2 < Dv50 成品 / Dv50 骨料 < 5; and / or, O is 50 to 100 mL / 100 g; and / or, T is 0.80 to 1.20 g / cm 3 ; and / or, OI is 2 to 11.

8. The production method according to claim 6 or 7, wherein The particle size of the granular materials is 1-50 cm. 9.A method for evaluating the rate capability of a graphite negative electrode active material, comprising the following steps: S1. Setting the rate performance index of the graphite negative electrode active material as W, W = (O x T x Dv50 成品 ) / (OI x Dv50 骨料 ); wherein, O is the oil absorption value of the graphite negative electrode active material, unit is mL / 100g; T is the tap density of the graphite negative electrode active material, unit is g / cm 3 ; Dv50 成品 is the particle size corresponding to the cumulative volume distribution percentage of the graphite negative electrode active material reaching 50%, unit is μm; OI is the orientation degree of the graphite negative electrode active material; Dv50 骨料 is the particle size corresponding to the cumulative volume distribution percentage of the aggregate used by the graphite negative electrode active material reaching 50%, unit is μm; S2. Calculate W from O, T, Dv50 成品 , OI, and Dv50 骨料 . S3. When W≥3.0, judging that the graphite negative electrode active material is a high-rate-capability negative electrode active material; and when W<3.0, judging that the graphite negative electrode active material is a low-rate-capability negative electrode active material.

10. The evaluation method according to claim 9, wherein The larger W is, the higher the rate capability of the graphite negative electrode active material is.

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