Negative electrode material, preparation method thereof and battery

Abstract

The invention discloses a negative electrode material, a preparation method thereof and a battery. The negative electrode material comprises a graphite material and further has a hierarchical pore structure, and the hierarchical pore structure comprises a mesoporous structure located on the surface layer of the graphite material and a microporous structure which is communicated with the mesoporous structure and located on the outer layer of the mesoporous structure. Through the unique hierarchical pore structure in the negative electrode material, the capacity and fast charging performance of a negative electrode material product can be remarkably improved, meanwhile, the preparation process of the negative electrode material can be relatively simple, and the negative electrode material is suitable for commercial large-scale production.

Description

Technical Field

[0001] This application generally relates to the field of battery technology. More specifically, this application relates to a negative electrode material, a method for preparing the same, and a battery. Background Technology

[0002] Artificial graphite anode materials have the advantages of high energy density, good cycle performance, mature preparation technology and low manufacturing cost, making them the mainstream anode materials in the commercialization of lithium-ion batteries.

[0003] With the rapid development of the electric vehicle and energy storage markets, the demand for high-energy-density batteries is becoming increasingly urgent. Improving the capacity of artificial graphite anodes is an effective means to meet market demand and has a significant impact on the commercialization of lithium-ion batteries.

[0004] In the current market, the mainstream capacity of artificial graphite anode products is typically around 355 mAh / g. Although there are ways to improve the specific capacity of graphite anode materials through oxidation modification, fluorination modification, and surface chemical treatment, these methods often lead to increased production costs and may significantly affect the cycle performance of graphite anode materials, making it difficult to simultaneously improve the capacity and rate performance.

[0005] Therefore, there is an urgent need for an innovative anode material, its preparation method, and the battery, which can be suitable for large-scale commercialization while also possessing high initial coulombic efficiency, good cycle performance, and rate performance, thus meeting the market's demand for high-performance batteries. Summary of the Invention

[0006] In order to at least solve one or more of the technical problems mentioned above, this application proposes a negative electrode material and its preparation method, and a battery in several aspects.

[0007] In a first aspect, this application provides a negative electrode material, including a graphite material, the negative electrode material further having a hierarchical pore structure, the hierarchical pore structure including a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure communicating with the mesoporous structure.

[0008] In some embodiments, the negative electrode material has at least one of the following characteristics: (1) the average pore size R1 of the micropores in the microporous structure is 1nm-1.5nm, and the average pore size R2 of the mesoporous structure is 2nm-10nm; (2) the average pore size R1 of the micropores in the microporous structure and the average pore size R2 of the mesoporous structure satisfy the relationship: 1.3≤R2 / R1≤10.

[0009] In some other embodiments, the negative electrode material has at least one of the following characteristics: (1) the average pore depth D1 of the micropores in the microporous structure is 2nm-4nm, and the average pore depth D2 of the mesoporous structure is 5nm-15nm; (2) the average pore depth D1 of the micropores in the microporous structure and the average pore depth D2 of the mesoporous structure satisfy the relationship: 1.2≤D2 / D1≤7.5.

[0010] In some other embodiments, the negative electrode material has at least one of the following characteristics: (1) the average pore volume V1 of the micropores in the microporous structure is 0.01 cm³. 3 / g-0.1cm 3 / g, the average pore volume V2 of the mesoporous structure is 1cm. 3 / g-5cm 3 / g; (2) The average pore volume V1 of the micropores in the microporous structure and the average pore volume V2 of the mesoporous structure satisfy the following relationship: 10≤V2 / V1≤500.

[0011] In some other embodiments, the negative electrode material has at least one of the following features: (1) the graphite material includes primary porous graphite, secondary porous graphite composed of the primary particles, or primary porous graphite combined with secondary porous graphite; (2) the graphite material includes secondary porous graphite, which is composed of 2-4 primary porous graphite particles; (3) the negative electrode material further includes a carbon material coating layer, which is located on the outer layer of the graphite material, and the microporous structure is at least partially formed in the carbon material coating layer.

[0012] In some other embodiments, the negative electrode material has at least one of the following characteristics: (1) the oil absorption value of the negative electrode material is 50 mL / 100g-60 mL / 100g; (2) the particle size distribution of the negative electrode material is as follows: D 10 The diameter is 6μm-9μm, D 50 For 10μm-14μm, D 90 The diameter is 18μm-26μm, D 100 <60μm; (3) The tap density of the negative electrode material is 0.85g / m 3 -1.05g / m 3 (4) The specific surface area of ​​the negative electrode material is 1.5 m² / g-4.0 m² / g; (5) The 5T powder compaction density of the negative electrode material is ≥1.85 g / m³. 3 .

[0013] In a second aspect, this application provides a method for preparing a negative electrode material, comprising the following steps: 1) adding shaped graphite material raw material to a solution of a first etchant to obtain a first suspension; 2) drying the first suspension to obtain a first precursor; 3) mixing the first precursor with asphalt and a second etchant, mixing evenly, and then heating and granulating to obtain a second precursor; 4) graphitizing the second precursor at high temperature to obtain the negative electrode material; wherein the negative electrode material includes graphite material, and the negative electrode material also has a hierarchical porous structure, the hierarchical porous structure including a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure communicating with the mesoporous structure.

[0014] In some embodiments, the preparation method comprises at least one of the following features: (1) the graphite material raw material includes oil-based needle coke or coal-based needle coke; (2) the median particle size D of the graphite material raw material after shaping. 50 (3) The first etchant includes ZnCl2; (4) The second etchant includes K2CO3.

[0015] In some other embodiments, the preparation method has at least one of the following features: (1) the solid content of the first suspension is 30%-70%; (2) the mass fraction of the graphite material raw material in the solid obtained after drying the first suspension is 95%-99.5%, and the mass fraction of the first etchant is 0.5%-5%; (3) the drying method of the first suspension in step 2) includes spray drying, wherein the inlet temperature of the spray drying is 180℃-200℃, the outlet temperature is 90℃-120℃, and the liquid... The volume flow rate is 4ml / min-8ml / min; (4) In step 3), the mass fraction of the first precursor, asphalt, and second etchant in the mixture is 85%-89.5%, the mass fraction of the asphalt is 10%, and the mass fraction of the second etchant is 0.5%-5%; (5) The heating granulation temperature in step 3) is 500℃-700℃, and the time is 6h-10h; (6) The high-temperature graphitization temperature in step 4) is 2800-3000℃, and the time is 2-6h.

[0016] In a third aspect, this application provides a battery comprising: a negative electrode sheet, wherein the negative electrode sheet is prepared using the negative electrode material described in any one of the first aspects and multiple embodiments of this application or the negative electrode material prepared by any one of the preparation methods described in the second aspect and multiple embodiments of this application.

[0017] Through the aforementioned negative electrode material, its preparation method, and battery, this application allows for the design of the pore structure on the surface of the negative electrode material, forming a unique hierarchical pore structure. This hierarchical pore structure can include a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure, connected to it. The microporous structure can provide the negative electrode material with additional lithium-ion adsorption and storage capacity, thereby increasing the capacity of the negative electrode material product to 360 mAh / g or higher. The mesoporous structure can rapidly and preferentially deposit lithium ions adsorbed from the microporous structure, which are then gradually embedded within the graphite, thus improving the fast-charging performance of the negative electrode material product and enabling it to achieve higher charging rates. Attached Figure Description

[0018] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0019] Figure 1 A schematic diagram of the negative electrode material prepared according to some embodiments of this application is shown;

[0020] Figure 2 A schematic diagram of a battery electrode assembly according to some embodiments of this application is shown. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0023] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0024] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0025] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0026] Lithium-ion batteries are rechargeable batteries that rely primarily on the movement of lithium ions between the positive and negative electrodes to complete the charging and discharging process. Graphite, due to its unique layered structure, can provide a large number of insertion sites for lithium ions, making it the mainstream negative electrode material.

[0027] In the above scenarios, the quantity and rate of lithium ion storage / release in the graphite anode have a significant impact on the battery's capacity and rate performance. Furthermore, considering that lithium ions are inserted / extracted from the graphite anode through active sites such as the edges and interlayer spaces in the graphite layered structure, the capacity and rate performance of the graphite anode can be improved by increasing the number of active sites.

[0028] In view of this, this application discloses an anode material and its preparation method, as well as a battery. The anode material can increase the active sites of the graphite anode and enhance the processing capacity of the graphite anode through a unique hierarchical porous structure, thereby improving the capacity and rate performance of the graphite anode.

[0029] In a first aspect, this application provides a negative electrode material, including a graphite material, wherein the negative electrode material further has a hierarchical porous structure, the hierarchical porous structure including a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure communicating with the mesoporous structure. The surface of the graphite material may, for example, be located on the graphite material and away from its center, and the outer layer of the mesoporous structure may, for example, be located around the mesoporous structure and away from its center.

[0030] Figure 1 Schematic diagrams of negative electrode materials prepared according to some embodiments of this application are shown. Figure 1 As shown, the negative electrode material disclosed in this application includes graphite material 110, and the negative electrode material also has a hierarchical porous structure 120. The hierarchical porous structure 120 includes a mesoporous structure 122 located on the surface of the graphite material 110 and a microporous structure 121 located on the outer layer of the mesoporous structure 122 and communicating with the mesoporous structure 122. Figure 1 As shown, the negative electrode material provided in this application can increase the capacity of the negative electrode material product to 360mAh / g and above through the mesoporous structure located on the surface of the graphite material and the microporous junction located on the outer layer of the mesoporous structure connected to the mesoporous structure. At the same time, it greatly improves the fast charging performance of the negative electrode material product, enabling the negative electrode material product to achieve a higher charging rate.

[0031] In some embodiments, the negative electrode material disclosed in this application further includes a carbon material coating layer, which is located on the outer layer of the graphite material, and a microporous structure is at least partially formed in the carbon material coating layer. The outer layer of the graphite material can be, for example, a location or space in contact with the surface of the graphite material. It is understood that the outer layer of the graphite material is also a mesoporous outer layer, and the carbon material coating layer on the outer layer of the graphite material can form a microporous structure. This allows the negative electrode material disclosed in this application to form a unique hierarchical pore structure through the microporous structure in the carbon material coating layer in contact with the graphite material and the mesoporous structure on the surface of the graphite material, thereby improving the fast-charging performance of the negative electrode material product and enabling the negative electrode material product to achieve a higher charging rate.

[0032] In some embodiments, the carbon material coating layer may occupy at least part of the outer layer position or space of the graphite material, that is, the carbon material forms an incomplete coating on the graphite material; in other embodiments, the carbon material coating layer may occupy all the outer layer position or space of the graphite material, that is, the carbon material forms a complete coating on the graphite material.

[0033] In some embodiments, the graphite material in the negative electrode material disclosed in this application includes primary porous graphite, secondary porous graphite composed of primary particles, or secondary porous graphite as described in the primary porous graphite description. Primary porous graphite refers to unprocessed or untreated raw porous graphite particles, while secondary particles are particles composed of primary particles.

[0034] In some embodiments, secondary particle porous graphite is composed of 2-4 primary particle porous graphite particles.

[0035] As mentioned earlier, more active sites can improve the capacity and rate performance of graphite anodes. The hierarchical porous structure of graphite in the anode material disclosed in this application provides abundant pores, thereby increasing the number of active sites in the graphite anode. This allows lithium ions to be inserted into / extracted from the graphite material through a large number of active sites, thus improving the capacity and rate performance of the graphite anode material. Furthermore, this hierarchical porous structure includes a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure, which is connected to the mesoporous structure. The microporous structure not only creates more lithium storage sites but also generates capillary action with the electrolyte, giving the micropores additional lithium ion adsorption capabilities, increasing the capacity of the graphite anode to 360 mAh / g or higher. At the same time, the mesoporous structure can quickly and preferentially deposit the lithium ions adsorbed from the microporous structure and then slowly embed them into the interior of the graphite material. This improves the fast charging capability of the anode material product, enabling higher rate charging.

[0036] Considering that the average pore size of the microporous structure on the outer layer of graphite material has a significant impact on the initial coulombic efficiency and capacity of the anode material in practical applications, and that the average pore size of the mesoporous structure on the graphite surface affects the tap density and compaction density of the anode material, thus influencing its processing performance, it is necessary to control the average pore size of the micropores in the microporous structure and the mesoporous structure in the mesoporous structure. This is to ensure that the anode material can have high capacity, good initial coulombic efficiency, and good processing performance, while also ensuring that the average pore size of the microporous structure on the outer layer of graphite material allows lithium ions to pass through.

[0037] Specifically, in some embodiments, the average pore size R1 of the micropores in the microporous structure is 1nm-1.5nm, specifically 1nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, etc.; the average pore size R2 of the mesoporous structure is 2nm-10nm, specifically 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, etc., without limitation.

[0038] In some embodiments, the average pore diameter R1 of the micropores in the microporous structure and the average pore diameter R2 of the mesoporous structure also satisfy the relationship: 1.3≤R2 / R1≤10, which can be 1.3, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc., and is not limited here.

[0039] Furthermore, pore depth represents the distance from the pore structure to the surface of the negative electrode material. Considering that the average pore depth of micropores in a microporous structure affects the lithium-ion transport distance, thus influencing the charging rate and capacity of the negative electrode material, and similarly, the average pore depth of mesoporous structures affects the charging speed and processing performance of the negative electrode material, it is necessary to control the average pore depth of micropores in microporous structures and the average pore depth of mesoporous structures to maximize the capacity and charging speed of the negative electrode material, while ensuring that the tap density and compaction density of the negative electrode material do not affect the processing performance of the product.

[0040] Specifically, in some embodiments, the average pore depth D1 of the micropores in the microporous structure is 2nm-4nm, specifically 2nm, 2.3nm, 2.5nm, 2.8nm, 3nm, 3.3nm, 3.5nm, 3.8nm, 4nm, etc.; the average pore depth D2 of the mesoporous structure is 5nm-15nm, specifically 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, etc., without limitation.

[0041] In some embodiments, the average pore depth D1 of the micropores in the microporous structure and the average pore depth D2 of the mesoporous structure satisfy the relationship: 1.2≤D2 / D1≤7.5. Specifically, it can be 1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, etc., and is not limited here.

[0042] Furthermore, considering that the average pore volume of micropores in microporous structures affects the capacity and initial coulombic efficiency of anode materials, while the average pore volume of mesoporous structures significantly impacts the charging speed and processing performance of anode materials, it is necessary to control the average pore volume of micropores in microporous structures and the average pore volume of mesoporous structures to maximize the capacity and charging speed of anode materials and ensure that the tap density and compaction density of anode materials do not affect the processing performance of the products.

[0043] Specifically, in some embodiments, the average pore volume V1 of the micropores in the microporous structure is 0.01 cm³. 3 / g-0.1cm 3 / g, specifically 0.01cm 3 / g, 0.02cm 3 / g, 0.03cm 3 / g, 0.04cm 3 / g, 0.05cm3 / g, 0.06cm 3 / g, 0.07cm 3 / g, 0.08cm 3 / g, 0.09cm 3 / g, 0.1cm 3 / g, etc.; the average pore volume V2 of the mesoporous structure is 1 cm³. 3 / g-5cm 3 / g, specifically 1cm 3 / g, 1.5cm 3 / g、2cm 3 / g, 2.5cm 3 / g, 3cm 3 / g, 3.5cm 3 / g、4cm 3 / g, 4.5cm 3 / g, 5cm 3 / g, etc., can also be other values ​​within the above range, and are not limited here.

[0044] In some embodiments, the average pore volume V1 of the micropores in the microporous structure and the average pore volume V2 of the mesoporous structure satisfy the relationship: 10≤V2 / V1≤500, which can be 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, etc., and is not limited here.

[0045] In some embodiments, the oil absorption value of the negative electrode material disclosed in this application is 50mL / 100g-60mL / 100g, specifically 50mL / 100g, 51mL / 100g, 52mL / 100g, 53mL / 100g, 54mL / 100g, 55mL / 100g, 56mL / 100g, 57mL / 100g, 58mL / 100g, 59mL / 100g, 60mL / 100g, etc., or other values ​​within the above range, which are not limited here.

[0046] In some embodiments, the particle size distribution of the negative electrode material disclosed in this application is as follows: D 10 The thickness ranges from 6μm to 9μm, specifically 6μm, 7μm, 8μm, 9μm, etc.; D 50 The range is 10μm-14μm, specifically 10μm, 11μm, 12μm, 13μm, 14μm, etc.; D 90 The range is 18μm-26μm, specifically 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, etc.; D 100<60μm, specifically can be 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, etc., without limitation here.

[0047] In some embodiments, the tap density of the negative electrode material disclosed in this application is 0.85 g / m³. 3 -1.05g / m 3 Specifically, it can be 0.85g / m 3 0.90g / m 3 0.95g / m 3 1.00g / m 3 1.05g / m 3 "etc." can also be other values ​​within the above range, and are not limited here.

[0048] In some embodiments, the specific surface area of ​​the negative electrode material disclosed in this application is 1.5 m². 2 / g-4.0m 2 / g, specifically, 1.5m 2 / g, 2.0m 2 / g, 2.5m 2 / g, 3.0m 2 / g, 3.5m 2 / g, 4.0m 2 / g, etc., are not limited here.

[0049] In some embodiments, the 5T powder compaction density of the negative electrode material disclosed in this application is ≥1.85 g / cm³. 3 Specifically, it could be 1.85 g / cm³ 3 1.86 g / cm 3 1.87 g / cm 3 1.88g / cm 3 1.89 g / cm 3 1.90g / cm 3 1.91g / cm 3 1.92g / cm 3 1.93g / cm 3 1.94 g / cm 3 1.95g / cm 3 1.96g / cm 3 1.97g / cm 3 1.98g / cm 3 1.99g / cm 3 etc. are not specified here.

[0050] In a second aspect, this application provides a method for preparing a negative electrode material. This method involves sequentially coating a first etchant, pitch, and a second etchant onto the surface of a graphite raw material. Then, high-temperature carbonization is used to form a carbon material coating layer on the outer layer of the graphite material from the pitch. The first and second etchants are then etched at positions or spaces (e.g., within the carbon material coating layer) on the surface and outer layer of the graphite material, respectively, to form a hierarchical porous structure including mesoporous and microporous structures. The microporous structure within the hierarchical porous structure can provide the negative electrode material with additional capacity for adsorbing and storing lithium ions. The mesoporous structure can rapidly and preferentially deposit lithium ions adsorbed from the microporous structure, which are then gradually embedded into the graphite interior, thereby improving the capacity and fast-charging performance of the negative electrode material product. Specifically, the preparation method includes the following steps:

[0051] Step S10: Add the shaped graphite material raw material to the solution of the first etchant to obtain the first suspension.

[0052] In some embodiments, the graphite material raw material may be, for example, oil-based needle coke or coal-based needle coke. Preferably, the median particle size D of the shaped graphite material raw material is... 50 For example, it can be 6μm-10μm, specifically 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, etc., without limitation here.

[0053] In some embodiments, the first etchant may be, for example, ZnCl2 or other substances that can be used to etch a mesoporous structure on the surface of a graphite material, and this application makes no limitation in this regard.

[0054] In some embodiments, the solid content of the first suspension may be, for example, 30%-70%, specifically 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc., and is not limited herein. It is understood that the solid content may be obtained, for example, by measuring the solids obtained after drying the first suspension.

[0055] In some embodiments, the mass fraction of graphite material raw material in the solid obtained after drying the first suspension is 95%-99.5%, specifically 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, etc.; the mass fraction of the first etchant in the solid obtained after drying the first suspension is 0.5%-5%, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0056] Step S20: Dry the first suspension to obtain the first precursor.

[0057] In some embodiments, the method for drying the first suspension may be, for example, spray drying.

[0058] In some embodiments, the inlet temperature of the spray dryer can be, for example, 180℃-200℃, specifically 180℃, 185℃, 190℃, 195℃, 200℃, etc.; the outlet temperature can be, for example, 90℃-120℃, specifically 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, etc.; the liquid flow rate of the first suspension at the inlet can be, for example, 4ml / min-8ml / min, specifically 4ml / min, 4.5ml / min, 5ml / min, 5.5ml / min, 6ml / min, 6.5ml / min, 7ml / min, 7.5ml / min, 8ml / min, etc., and is not limited here.

[0059] Step S30: Mix the first precursor with asphalt and the second etching agent, and after mixing evenly, heat and granulate to obtain the second precursor.

[0060] In some embodiments, the mass fraction of the first precursor in the mixture of the first precursor, asphalt, and second etchant is 85%-89.5%, specifically 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, etc.; the mass fraction of the asphalt is 10%; and the mass fraction of the second etchant is 0.5%-5%, specifically 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., which are not limited here.

[0061] In some embodiments, the second etchant may be, for example, K2CO3 or other substances that can be used to etch microporous structures on a carbon material coating or other structure on the outer layer of graphite material, and this application makes no limitation in this regard.

[0062] In some embodiments, the temperature for heating and granulating the mixture of the first precursor, asphalt, and second etchant can be, for example, 500°C-700°C, specifically 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, etc.; the heating and granulation time can be, for example, 6h-10h, specifically 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h.

[0063] Step S40: The second precursor is graphitized at high temperature, so that the first etchant and the second etchant in the first etchant solution etch the second precursor to obtain the negative electrode material. The negative electrode material includes graphite material and also has a hierarchical porous structure, which includes mesoporous structures located on the surface of the graphite material and microporous structures located on the outer layer of the mesoporous structures and communicating with them.

[0064] It is understood that in the method for preparing the negative electrode material provided in this application, the first etchant and the second etchant of the microporous structure and mesoporous structure etching materials have been coated before high-temperature graphitization. During the graphitization process, the etching materials can form microporous and mesoporous structures on the surface of the graphite material, and can also remove impurity elements in the etching materials through high-temperature graphitization, thereby preventing the introduction of impurity elements into the negative electrode material.

[0065] In some embodiments, the temperature for high-temperature graphitization of the second precursor can be, for example, 2800℃-3000℃, specifically 2800℃, 2850℃, 2900℃, 2950℃, 3000℃, etc., or other values ​​within the above range, which are not limited here.

[0066] In some embodiments, the high-temperature graphitization time of the second precursor can be, for example, 2h-6h, specifically 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, etc., or other values ​​within the above range, which are not limited here.

[0067] In a third aspect, this application provides a battery including a negative electrode sheet, wherein the negative electrode sheet is made of the negative electrode material described in the first aspect and several embodiments of this application or the negative electrode material prepared by the preparation method described in the second aspect and several embodiments of this application.

[0068] In some embodiments, the capacity of the battery disclosed in this application is ≥362mAh / g, specifically 362Ah / g, 262.2Ah / g, 362.4Ah / g, 362.6Ah / g, 262.8Ah / g, 363Ah / g, etc.; the initial coulombic efficiency of the battery is ≥93%, specifically 93%, 93.5%, 94%, 94.5%, 95%, 95.5%, 96%, 96.5%, 97%, etc., which are not limited here.

[0069] In some embodiments, the battery provided in this application may be a secondary battery (such as a lithium-ion battery, sodium-ion battery, etc.), including a casing, an electrode assembly, and an electrolyte / electrolyte. Both the electrode assembly and the electrolyte / electrolyte are located within the casing.

[0070] The outer casing can be a packaging bag sealed with an encapsulating film (such as aluminum-plastic film), for example, a pouch battery for a secondary battery. In other embodiments, the secondary battery can also be a steel-cased battery, an aluminum-cased battery, etc.

[0071] Figure 2 A schematic diagram of a battery electrode assembly according to some embodiments of this application is shown.

[0072] like Figure 2 As shown, the electrode assembly includes a positive electrode 210, a negative electrode 220, and a separator 230, with the separator disposed between the positive and negative electrode sheets. The electrode assembly can be a stacked structure, formed by alternating layers of the positive electrode, separator, and negative electrode. In other embodiments, the electrode assembly can also be a wound structure, formed by winding the positive electrode, separator, and negative electrode after they have been stacked sequentially.

[0073] The positive electrode 210 includes a positive current collector 21 and a positive active layer 212 disposed on at least one surface of the positive current collector. The positive current collector can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The positive active layer contains a positive active material, which includes compounds that reversibly insert and extract metal ions. In some embodiments, the positive active material may include lithium transition metal composite oxides, sodium transition metal composite oxides, etc. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive active material may include, but is not limited to, lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary materials (NCM), lithium manganese oxide (LiMn2O4), and lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 At least one of lithium iron phosphate (LiFePO4) or lithium iron phosphate (LiFePO4).

[0074] The negative electrode sheet 220 includes a negative electrode current collector 221 and a negative electrode active material layer 222 disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collectors, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The negative electrode active material layer includes a negative electrode material, which is the negative electrode material described in the first aspect and several embodiments of this application or the negative electrode material prepared by the preparation method described in the second aspect and several embodiments of this application; the same content will not be repeated here.

[0075] During battery operation, i.e. when the battery is in a discharge state, metal ions 240 (e.g., lithium ions) in the negative electrode are released from the lattice of the negative electrode material, pass through the electrolyte / electrolyte through the separator 230, and are embedded into the lattice of the positive electrode material.

[0076] Conversely, when the battery is charged by applying an external circuit, the oxidation of the positive electrode material causes metal ions (such as lithium ions) in the positive electrode to be released from the lattice of the positive electrode material, pass through the electrolyte / electrolyte through the separator, and move to the negative electrode; at the same time, the negative electrode material undergoes a reduction reaction, causing metal ions to be embedded in the lattice of the negative electrode material.

[0077] As metal ions move back and forth between the positive and negative electrodes, the battery can achieve the discharge and charge process in thousands of cycles.

[0078] The present application will be further illustrated by specific embodiments below:

[0079] Example 1

[0080] (1): Select oil-based needle coke as raw material, crush and shape the oil-based needle coke, and then shape the oil-based needle coke D. 50 The diameter was 7 μm; then the shaped oil-based needle coke was added to a ZnCl2 solution to obtain a first suspension with a solid content of 50%. The solids of the first suspension after drying contained 99% shaped oil-based needle coke and 1% ZnCl2 by mass.

[0081] (2): The first suspension was dried by spray drying to obtain the first precursor. The inlet temperature of the spray dryer was 180℃, the outlet temperature was 110℃, and the liquid flow rate of the first suspension at the inlet was 5ml / min.

[0082] (3): The first precursor, asphalt, and K2CO3 were mixed evenly in a VC mixing device. The mass fraction of the first precursor in the mixture was 87%, the mass fraction of asphalt was 10%, and the mass fraction of K2CO3 was 3%. Then, the mixture of the first precursor, asphalt, and K2CO3 was subjected to heat granulation treatment at a temperature of 650℃ for 8 hours to obtain the second precursor.

[0083] (4): The second precursor was graphitized at high temperature in an Atchison furnace to obtain the anode material (parameters are detailed in Tables 1 and 2). The graphitization temperature was 2950℃ and the graphitization time was 3h.

[0084] The negative electrode material prepared in this embodiment includes graphite material, and the negative electrode material also has a hierarchical porous structure, which includes a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure that is connected to the mesoporous structure.

[0085] Example 2

[0086] (1): Selecting coal-series needle coke as raw material, crushing and shaping the coal-series needle coke, the shaped coal-series needle coke D 50The diameter was 8 μm; then the shaped coal-series needle coke was added to a ZnCl2 solution to obtain a first suspension with a solid content of 50%. The solids of the first suspension after drying contained 98% shaped coal-series needle coke and 2% ZnCl2 by mass.

[0087] (2): The first suspension was dried by spray drying to obtain the first precursor. The inlet temperature of the spray dryer was 180℃, the outlet temperature was 110℃, and the liquid flow rate of the first suspension at the inlet was 5ml / min.

[0088] (3): The first precursor, asphalt, and K2CO3 were mixed evenly in a VC mixing device. The mass fraction of the first precursor in the mixture was 86%, the mass fraction of asphalt was 10%, and the mass fraction of K2CO3 was 4%. Then, the mixture of the first precursor, asphalt, and K2CO3 was subjected to heat granulation treatment at a temperature of 650℃ for 8 hours to obtain the second precursor.

[0089] (4): The second precursor was graphitized at high temperature in an Atchison furnace to obtain the anode material (parameters are detailed in Tables 1 and 2). The graphitization temperature was 3000℃ and the graphitization time was 3h.

[0090] Example 3

[0091] (1): Selecting coal-series needle coke as raw material, crushing and shaping the coal-series needle coke, the shaped coal-series needle coke D 50 The diameter was 9 μm; then the shaped coal-series needle coke was added to a ZnCl2 solution to obtain a first suspension with a solid content of 50%. The solids of the first suspension after drying contained 97% shaped coal-series needle coke and 3% ZnCl2 by mass.

[0092] (2): The first suspension was dried by spray drying to obtain the first precursor. The inlet temperature of the spray dryer was 180℃, the outlet temperature was 110℃, and the liquid flow rate of the first suspension at the inlet was 5ml / min.

[0093] (3): The first precursor, asphalt, and K2CO3 are mixed evenly in a VC mixing device. The mass fraction of the first precursor in the mixture is 85%, the mass fraction of asphalt is 10%, and the mass fraction of K2CO3 is 5%. Then, the mixture of the first precursor, asphalt, and K2CO3 is subjected to heat granulation treatment at a temperature of 650℃ for 8 hours to obtain the second precursor.

[0094] (4): The second precursor was graphitized at high temperature in an Atchison furnace to obtain the anode material (parameters are detailed in Tables 1 and 2). The graphitization temperature was 3000℃ and the graphitization time was 3h.

[0095] Example 4

[0096] The difference between this embodiment and Embodiment 1 is that the mass fraction of the first precursor in the mixture of step (3) is 88%, the mass fraction of asphalt is 10%, and the mass fraction of K2CO3 is 2%.

[0097] All other conditions are exactly the same as in Example 1.

[0098] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0099] Example 5

[0100] The difference between this embodiment and Embodiment 1 is that, in step (1), the mass fraction of the shaped oil-based needle coke in the solids after drying the first suspension is 99.5%, and the mass fraction of ZnCl2 is 0.5%.

[0101] All other conditions are exactly the same as in Example 1.

[0102] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0103] Example 6

[0104] The difference between this embodiment and embodiment 1 is that the graphitization time in step (4) is less than 2 hours.

[0105] All other conditions are exactly the same as in Example 1.

[0106] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0107] Example 7

[0108] The difference between this embodiment and Embodiment 1 is that, in step (1), the solids after drying the first suspension contain 95% oil-based needle coke and 5% ZnCl2.

[0109] All other conditions are exactly the same as in Example 1.

[0110] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0111] Example 8

[0112] The difference between this embodiment and embodiment 1 is that the graphitization time in step (4) is greater than 4 hours.

[0113] All other conditions are exactly the same as in Example 1.

[0114] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0115] Example 9

[0116] The difference between this embodiment and embodiment 1 is that in step (1), the mass fraction of the shaped oil-based needle coke in the solid material after drying the first suspension is 96% and the mass fraction of ZnCl2 is 4%, and the graphitization time in step (4) is greater than 4 hours.

[0117] All other conditions are exactly the same as in Example 1.

[0118] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0119] Comparative Example 1

[0120] The difference between this embodiment and embodiment 1 is that in step (1), oil-based needle coke is selected as raw material, and after the oil-based needle coke is crushed and shaped, step (3) is carried out directly.

[0121] All other conditions are exactly the same as in Example 1.

[0122] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0123] Comparative Example 2

[0124] The difference between this embodiment and embodiment 1 is that K2CO3 is not added in step (3).

[0125] All other conditions are exactly the same as in Example 1.

[0126] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0127] Comparative Example 3

[0128] The difference between this embodiment and embodiment 1 is that in step (1), oil-based needle coke is selected as raw material, and after the oil-based needle coke is crushed and shaped, step (3) is carried out directly, and K2CO3 is not added in step (3).

[0129] All other conditions are exactly the same as in Example 1.

[0130] The parameters of the negative electrode material prepared in this embodiment are detailed in Tables 1 and 2.

[0131] Test method:

[0132] (1) Methods for testing average hole depth, hole diameter, and hole volume:

[0133] The results were calculated using the carbon dioxide gas adsorption DFT method and the BHJ method, specifically the NLDFT method based on the carbon dioxide adsorption and desorption isotherms, as detailed below:

[0134] Pore ​​volume (i.e., total pore volume): The total pore volume is calculated by assuming that the maximum amount of carbon dioxide adsorbed under relative pressure is completely adsorbed and filled in the pores.

[0135] Average pore diameter: Calculated using a slit pore model according to the following formula: R = 2V / S; where R is the average pore diameter, V is the total pore volume, and S is the specific surface area;

[0136] Average hole depth: Calculated using a slotted hole model according to the following formula: D=V / (Π(R / 2)) 2 ); where R is the average pore diameter and V is the total pore volume.

[0137] (2) Button cell battery test

[0138] The electrochemical cycle performance was tested using the following method: Anode material, conductive agent, and binder were dissolved in deionized water at a mass ratio of 94:1:5, with the solid content controlled at 50%. This mixture was then coated onto a copper foil current collector, vacuum dried, and the resulting anode sheet was obtained. A ternary cathode sheet prepared using conventional processes, a 1 mol / L LiPF6 / ethylene carbonate + dimethyl carbonate + methyl ethyl carbonate (v / v = 1:1:1) electrolyte, a Celgard 2400 separator, and a casing were assembled using conventional manufacturing processes to obtain a lithium-ion coin cell battery. The initial electrode thickness of the lithium-ion battery was measured to be H0 using a micrometer. Charge-discharge tests of the lithium-ion battery were conducted on the LAND battery testing system of Wuhan Jinno Electronics Co., Ltd., under room temperature conditions, with a constant current charge-discharge of 0.2C and a charge-discharge voltage limited to 0.05–1.5V, yielding the initial reversible capacity, first charge cycle capacity, and first discharge cycle capacity. Initial coulombic efficiency = first discharge capacity / first charge capacity; charge rate: 2C constant current discharge capacity / 0.2C constant current discharge capacity * 100%.

[0139] (3) Test method for specific surface area of ​​negative electrode material:

[0140] The dynamic specific surface area was measured using the JW-DX dynamic specific surface area rapid measuring instrument from Beijing Jingwei Gaobo Scientific Technology Co., Ltd., and the unit is m. 2 / g.

[0141] (4) Test method for particle size of negative electrode material:

[0142] The particle size distribution range of the negative electrode material was tested using a Malvern laser particle size analyzer.

[0143] (5) Test method for oil absorption value of negative electrode material:

[0144] The oil absorption value was tested using an ASAHI S-500 oil absorption value tester from ASAHISOUKEN, Japan. The oil absorption value O is the amount of linseed oil added when the torque generated by the change in viscosity characteristics reaches 70% of the maximum torque, and the unit is mL / 100g.

[0145] (6) Test method for tap density:

[0146] The compaction density was tested by weighing a certain amount of sample and vibrating it 3000 times at 300 times / min.

[0147] (7) Test method for compacted density of 5T powder:

[0148] Take 1g of sample in an area of ​​1cm² 2 The material is placed inside the mold, and then the height under 5T pressure is tested by an automatic powder pressing tester. The mass is then automatically calculated as a mass-to-volume ratio.

[0149] Table 1. Parameter test results of the negative electrode materials prepared in the examples and comparative examples.

[0150]

[0151]

[0152] Table 2. Parameter test results of the negative electrode materials prepared in the examples and comparative examples 2

[0153]

[0154]

[0155] As can be seen from the data in Examples 1-9, Comparative Examples 1-3, and Tables 1 and 2, when only microporous structures exist, the fast-charging performance of batteries made from negative electrode materials is relatively poor; when only mesoporous structures exist, the compaction performance of negative electrode materials and the capacity of the batteries made from them are relatively poor; when neither microporous nor mesoporous structures exist, the capacity and fast-charging performance of batteries made from negative electrode materials are both relatively poor.

[0156] As can be seen from the data in Examples 4, 6, and 8, and Tables 1 and 2, when the average pore size of the micropores in the microporous structure is relatively small, the improvement in capacity and rate performance of the battery made from this negative electrode material is relatively small; when the average pore depth of the micropores in the microporous structure is less than 2 nm, the improvement in capacity of the battery made from this negative electrode material is also relatively small; when the average pore volume of the micropores in the microporous structure is greater than 0.1 cm³, the improvement is more significant. 3The capacity increase of batteries made from this negative electrode material is also relatively large, even at a density of / g. Therefore, the average pore size, average pore depth, and average pore volume in the microporous structure of the negative electrode material all have a significant impact on the improvement of the negative electrode material product. Furthermore, as can be seen from Example 8, when the average pore volume of the micropores in the microporous structure is greater than 0.1 cm³, the capacity increase is also substantial. 3 At a density of / g, the specific surface area and initial coulombic efficiency of the anode material deteriorate significantly. In other words, the average pore volume of the micropores in the microporous structure of the anode material also has a significant impact on the specific surface area and initial coulombic efficiency of the anode material.

[0157] As can be seen from Examples 5, 7, and 9, and the data in Tables 1 and 2, when the average pore size of the mesoporous structure is relatively small, the improvement in fast-charging performance of the battery made from this negative electrode material is relatively small; when the average pore depth of the mesoporous structure is greater than 10 nm, the oil absorption value, tap density, and 5T compaction density of the negative electrode material all deteriorate significantly, resulting in poor processing performance of the negative electrode material; when the average pore volume of the mesoporous structure is greater than 5 cm³, the negative electrode material exhibits poor processing performance. 3 At a density of / g, the tap density and 5T compaction density of the negative electrode material also deteriorate significantly. Therefore, the average pore diameter, average pore depth, and average pore volume of the mesoporous structure have a significant impact on the processing performance of the negative electrode material, and also have a significant impact on the fast charging performance of the negative electrode material product.

[0158] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A negative electrode material, characterized in that, Including graphite materials, The negative electrode material also has a hierarchical pore structure, which includes a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure and communicating with the mesoporous structure.

2. The negative electrode material according to claim 1, characterized in that, The negative electrode material possesses at least one of the following characteristics: (1) The average pore diameter R1 of the micropores in the microporous structure is 1nm-1.5nm, and the average pore diameter R2 of the mesoporous structure is 2nm-10nm; (2) The average pore diameter R1 of the micropores in the microporous structure and the average pore diameter R2 of the mesoporous structure satisfy the following relationship: 1.3≤R2 / R1≤10.

3. The negative electrode material according to claim 1, characterized in that, The negative electrode material possesses at least one of the following characteristics: (1) The average pore depth D1 of the micropores in the microporous structure is 2nm-4nm, and the average pore depth D2 of the mesoporous structure is 5nm-15nm; (2) The average pore depth D1 of the micropores in the microporous structure and the average pore depth D2 of the mesoporous structure satisfy the following relationship: 1.2≤D2 / D1≤7.

5.

4. The negative electrode material according to claim 1, characterized in that, The negative electrode material possesses at least one of the following characteristics: (1) The average pore volume V1 of the micropores in the microporous structure is 0.01 cm³. 3 / g-0.1cm 3 / g, the average pore volume V2 of the mesoporous structure is 1cm. 3 / g-5cm 3 / g; (2) The average pore volume V1 of the micropores in the microporous structure and the average pore volume V2 of the mesoporous structure satisfy the following relationship: 10≤V2 / V1≤500.

5. The negative electrode material according to claim 1, characterized in that, The negative electrode material possesses at least one of the following characteristics: (1) The graphite material includes primary porous graphite, secondary porous graphite composed of the primary porous graphite, or primary porous graphite combined with the secondary porous graphite. (2) The graphite material includes secondary particle porous graphite, which is composed of 2-4 primary particle porous graphite particles. (3) The negative electrode material further includes a carbon material coating layer, which is located on the outer layer of the graphite material, and the microporous structure is at least partially formed in the carbon material coating layer.

6. The negative electrode material according to claim 1, characterized in that, The negative electrode material possesses at least one of the following characteristics: (1) The oil absorption value of the negative electrode material is 50mL / 100g-60mL / 100g; (2) The particle size distribution of the negative electrode material is as follows: D 10 The diameter is 6μm-9μm, D 50 For 10μm-14μm, D 90 The diameter is 18μm-26μm, D 100 <60μm; (3) The tap density of the negative electrode material is 0.85 g / m³. 3 -1.05g / m 3 ; (4) The specific surface area of ​​the negative electrode material is 1.5 m² / g to 4.0 m² / g; (5) The compacted density of the 5T powder of the negative electrode material is ≥1.85g / m³. 3 .

7. A method for preparing a negative electrode material, characterized in that, Includes the following steps: 1) The shaped graphite material raw material is added to the solution of the first etching agent to obtain the first suspension; 2) Dry the first suspension to obtain the first precursor; 3) The first precursor is mixed with asphalt and the second etching agent. After the mixture is homogeneous, it is heated and granulated to obtain the second precursor. 4) The second precursor is graphitized at high temperature to obtain the negative electrode material; wherein the negative electrode material includes graphite material, and the negative electrode material also has a hierarchical pore structure, the hierarchical pore structure including a mesoporous structure located on the surface of the graphite material and a microporous structure located on the outer layer of the mesoporous structure communicating with the mesoporous structure.

8. The preparation method according to claim 7, characterized in that, The preparation method possesses at least one of the following characteristics: (1) The graphite material raw materials include oil-based needle coke or coal-based needle coke; (2) The median particle size D of the graphite material raw material after shaping 50 The thickness is 6μm-10μm; (3) The first etchant includes ZnCl2; (4) The second etching agent includes K2CO3.

9. The preparation method according to claim 7, characterized in that, The preparation method possesses at least one of the following characteristics: (1) The solid content of the first suspension is 30%-70%; (2) The mass fraction of the graphite material raw material in the solid obtained after drying the first suspension is 95%-99.5%, and the mass fraction of the first etchant is 0.5%-5%. (3) The method for drying the first suspension in step 2) includes spray drying, wherein the inlet temperature of the spray drying is 180℃-200℃, the outlet temperature is 90℃-120℃, and the liquid flow rate is 4ml / min-8ml / min; (4) In step 3), the mass fraction of the first precursor, asphalt, and second etchant after mixing is 85%-89.5%, the mass fraction of the asphalt is 10%, and the mass fraction of the second etchant is 0.5%-5%. (5) The temperature for heating and granulation in step 3) is 500℃-700℃ and the time is 6h-10h; (6) In step 4), the high-temperature graphitization temperature is 2800-3000℃ and the time is 2-6h.

10. A battery, characterized in that, include: The negative electrode sheet is made of the negative electrode material according to any one of claims 1-6 or the negative electrode material prepared by any one of claims 7-9.

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