Preparation method and application of asphalt-based lithium ion battery hard carbon negative electrode coating material and negative electrode material

Abstract

The invention belongs to the technical field of lithium ion battery negative electrode materials, and discloses an asphalt-based lithium ion battery hard carbon negative electrode coating material and a preparation method and application of a negative electrode material. The preparation method comprises the following steps: S1, carrying out heat treatment on the asphalt-based substance; a molten asphalt-based substance is obtained; and S2, at a certain temperature, adding a boron-containing substance into the molten asphalt-based substance, carrying out high-speed shearing stirring for 60-90 min, and cooling to room temperature to obtain the hard carbon negative electrode coating material. The hard carbon negative electrode coating material provided by the invention not only improves the initial coulombic efficiency and rate capability of the lithium battery, but also is simple to operate and environment-friendly, and provides possibility for industrial production and application.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium-ion battery anode materials. It relates to an asphalt-based lithium-ion battery hard carbon anode coating material, a method for preparing the anode material, and its application. Background Technology

[0002] The development and exploitation of renewable and clean energy have received increasing attention. Lithium-ion batteries, due to their excellent energy storage performance, cycle stability, long lifespan, and rapid charge-discharge characteristics, have been widely used in recent decades and have become the main type of energy storage battery.

[0003] Lithium-ion batteries store and release energy through the insertion and extraction of ions in the positive and negative electrode materials. Currently, the market commonly uses natural graphite as the negative electrode material, which has advantages such as high specific capacity and low plateau voltage. However, it also has some drawbacks. During charge and discharge, large-volume solvent molecules often co-intercalate with lithium ions into the natural graphite layer, causing the natural graphite layer to expand and peel off. The inhomogeneity of the natural graphite surface makes it difficult to form a uniform and dense SEI film during the first charge and discharge cycle, resulting in low initial charge and discharge efficiency and poor cycle performance. Asphalt, a widely available and inexpensive petroleum processing byproduct, can be used for coating negative electrode materials through certain heat treatments. Asphalt coating can reduce the specific surface area of ​​natural graphite, inhibiting SEI film formation; it isolates natural graphite particles from the electrolyte, preventing capacity reduction caused by solvent co-intercalation; and it can restrain and buffer the volume expansion of natural graphite, increasing cycle stability. Furthermore, asphalt can improve the performance of Li-ion batteries. + The diffusion properties enhance the high-current charge-discharge performance and fast charge-discharge performance of natural graphite materials.

[0004] However, the development of asphalt-based materials as anode coatings still faces significant challenges. On one hand, asphalt has a complex composition, and the properties of asphalt from different sources vary considerably, which places demands on its consistency and performance stability as a battery material. On the other hand, as asphalt is an amorphous carbon structure, its primary purpose in coating anode materials is to improve structural stability and reduce the contact between the solvent and the anode material, offering limited improvement to the electrochemical performance of natural graphite. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies and address the problems of easy pulverization of natural graphite materials during charge and discharge, resulting in low rate performance and initial coulombic efficiency, this invention provides a method for preparing a pitch-based lithium-ion battery hard carbon anode coating material and anode material, as well as their applications. It provides a hard carbon anode material that can improve initial coulombic efficiency and rate performance.

[0006] This invention enhances the fluidity of asphalt-based materials through heat treatment, then introduces boron to obtain coated asphalt. The coated asphalt is mixed with spherical natural graphite, and after carbonization and natural graphitization, a hard carbon anode material is obtained. By doping with boron, the microstructure can be controlled, improving the carbon structure and electrical performance of the anode material. The hard carbon anode coating material provided by this invention not only improves the initial coulombic efficiency and rate performance of lithium batteries, but also is simple to operate, environmentally friendly, and provides possibilities for industrial production and application.

[0007] The above-mentioned objective of this invention is achieved through the following technical solution:

[0008] A method for preparing an asphalt-based lithium-ion battery hard carbon anode coating material includes the following steps:

[0009] S1. Heat-treat the asphalt-based material to obtain molten asphalt-based material;

[0010] S2. At a certain temperature, boron-containing substances are added to molten asphalt-based substances, and after high-speed shearing and stirring for 60-90 minutes, the mixture is cooled to room temperature to obtain hard carbon anode coating material.

[0011] Furthermore, in step S1, the asphalt-based material is selected from petroleum asphalt, heavy petroleum oil, and biomass asphalt, as well as any one or more of the following: heavy petroleum oil / naphthalene / anthracene aromatic hydrocarbons, and the softening point of the asphalt-based material is between 120 and 180°C.

[0012] Furthermore, in step S1, the heat treatment specifically involves maintaining a temperature of 200-250℃ until it melts, then holding the temperature constant for 30 minutes to enhance its fluidity while preventing excessive decomposition. The heat treatment is carried out in a vertical reactor furnace or a box furnace.

[0013] Furthermore, in step S2, the specific temperature is 200-250℃.

[0014] Furthermore, in step S2, after the molten asphalt-based material is kept at a constant temperature of 200-250℃ for 30-40 minutes, a boron-containing substance is added. Preferably, the temperature is kept constant for 30 minutes.

[0015] Furthermore, in step S2, the boron-containing substance is any one or more of boric acid, borax, and boron heterocyclic compounds. The mass of the added boron-containing substance generally does not exceed 5% of the mass of the asphalt-based substance.

[0016] When the boron-containing substance is boric acid, it should be added slowly and stirred at a rate of 1500-2000 r / min for 30-60 min. Preferably, when adding boric acid, it should be added slowly and stirred at a rate of 500-1000 r / min for 30-60 min.

[0017] When the boron-containing substance is borax, add it intermittently while stirring at a rate of 500-700 r / min. The interval between two additions should be 20-30 min. Ensure that the fluidity is restored before adding more. Each addition should not exceed 1 / 3 of the total mass of borax. After all the borax has been added and the fluidity has been restored, stir at a rate of 1500-2000 r / min for 30-60 min.

[0018] Preferably, when the boron-containing substance is borax, the borax is added intermittently and stirred at a rate of 300-500 r / min. After all the borax has been added and the fluidity has been restored, the mixture is stirred at a rate of 500-1000 r / min for 30-60 min.

[0019] Furthermore, in step S2, the boron-containing substance is in powder form.

[0020] Furthermore, in step S2, after the boron-containing substance is dissolved in the asphalt-based substance, it is stirred at a rate of 1500-2000 r / min for 30-60 min.

[0021] This invention also claims protection for the application of the hard carbon anode coating material prepared by the above preparation method in the preparation of anode materials. The application specifically includes the following steps: mixing natural graphite with the hard carbon anode coating material and carbonizing it at high temperature in an inert atmosphere to obtain the hard carbon anode material; the mass ratio of natural graphite to hard carbon anode coating material is 100:1-5.

[0022] Furthermore, the mixture is mixed using a mixer at a speed of 800-100 r / min for 30 minutes.

[0023] Furthermore, the inert atmosphere is any one or more of argon, helium, and nitrogen.

[0024] Furthermore, the high-temperature carbon treatment specifically involves heating to 1000-1500℃ at a heating rate of 5-10℃ / min and holding at that temperature for 5-10 hours.

[0025] Furthermore, the natural graphite is spherical.

[0026] Furthermore, the natural graphite is commercially available natural graphite with a particle size of 10-20 μm.

[0027] The advantages of this invention compared to the prior art are:

[0028] This invention successfully prepared asphalt-coated and hard carbon anode materials using asphalt-based materials as key raw materials. This effectively improved the lithium storage sites of natural graphite anode materials, increasing their specific capacity. It also improved the coating layer structure; the increased short-range ordered structure after doping enhanced the rate performance of the natural graphite anode materials. This preparation method is simple to operate, low in cost, and environmentally friendly, making it more suitable for large-scale production of asphalt-coated materials and enabling their widespread application as anode materials in lithium-ion batteries. Attached Figure Description

[0029] Figure 1 The images shown are polarized images of Comparative Example 1 and Example 1. In Figure a, the polarized image of Comparative Example 1 is shown, and in Figure b, the polarized image of Example 1 is shown.

[0030] Figure 2 The XRD patterns are for Comparative Example 1 and Example 1.

[0031] Figure 3 The Ramn spectra are for Comparative Example 1 and Example 1. Detailed Implementation

[0032] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0033] The hard carbon anode coating material of this invention exhibits excellent electrochemical performance, with faster charge-discharge performance and good cycle stability. Furthermore, the preparation method is simple and inexpensive, making it suitable for large-scale production.

[0034] Example 1

[0035] S1 Take 1.0 kg of petroleum asphalt with a softening point of 150℃ into a three-necked flask and heat-treat it at 200℃;

[0036] After the petroleum asphalt melts, stirring begins at a speed of 650 r / min. Simultaneously, 30 g of boric acid is added and stirred for 30 minutes to obtain boron-doped coated asphalt, i.e., the hard carbon anode coating material.

[0037] S3. 80g of the boron-doped coated pitch, i.e., the hard carbon anode coating material, and 1000g of natural graphite were placed in a mixer and mixed for 30min. Inert gas was introduced into the mixer, and the mixing speed was 1000r / min to obtain mixture A. The mixture A was placed in a box furnace under a protective atmosphere and heated to 1000℃ at a heating rate of 5℃ / min. After holding at this temperature for 4h, it was cooled to room temperature at a cooling rate of 5℃ / min to obtain the modified material. The modified material was then removed, sieved, and the coated natural graphite anode material was obtained.

[0038] Example 2

[0039] The other conditions, operations and examples are the same as in Example 1, except that in step S1, petroleum asphalt with a softening point of 120°C is used instead of petroleum asphalt with a softening point of 150°C.

[0040] Example 3

[0041] The other conditions and operations are the same as in Example 1, except that the boric acid in step S1 is increased from 30g to 60g.

[0042] Example 4

[0043] The other conditions, operations and Example 1 are the same, except that in step S1, 30g of borax is used instead of 30g of boric acid.

[0044] Example 5

[0045] The other conditions, operations and Example 1 are the same, except that in step S1, 150g of borax is used instead of 30g of boric acid.

[0046] Comparative Example 1

[0047] 1000g of natural graphite was placed in a box furnace under a protective atmosphere and heated to 1000℃ at a heating rate of 5℃ / min. After holding at this temperature for 4 hours, the temperature was lowered to room temperature at a cooling rate of 5℃ / min to obtain unmodified graphite anode material.

[0048] Comparative Example 2

[0049] Take 80g of unadulterated petroleum asphalt with a softening point of 150℃ and 1000g of natural graphite and mix them in a mixer for 30min. Inert gas is introduced into the mixer and the mixing speed is 1000r / min to obtain mixture B. Place the above mixture B in a box furnace under a protective atmosphere and heat it to 1000℃ at a heating rate of 5℃ / min. After holding it at this temperature for 4h, cool it down to room temperature at a cooling rate of 5℃ / min to obtain the modified material. Take it out, sieve it, and obtain the surface-modified natural graphite anode material.

[0050] Comparative Example 3

[0051] Other conditions and operations were the same as in Comparative Example 2, except that 80g of sulfur-doped coated bitumen was used instead of 80g of undoped petroleum bitumen.

[0052] Table 1 Specifications of purchased natural graphite

[0053]

[0054] The negative electrode materials prepared in Examples 1-5 and Comparative Examples 1-3 were used to prepare electrodes, and 2032 coin cells were assembled for electrochemical testing, following the steps below:

[0055] The test material (the negative electrode material prepared in Examples 1-5 and Comparative Example 1) was mixed evenly according to the mass ratio of negative electrode material: conductive agent (SuperP): binder (LA133) = 94:3:3, coated on copper foil with a coating thickness of 200 μm, and dried in a vacuum oven at 80°C for 12 h to obtain the negative electrode sheet.

[0056] CR2032 coin cells were assembled in a glove box (water and oxygen concentrations less than 0.01 ppm). Lithium foil was used as the counter electrode, and the electrolyte was 1 mol / L LiF6 dissolved in DMC:DEC:EC (volume ratio 1:1:1). The assembled coin cells were then subjected to charge-discharge cycle tests at 1C and rate tests at 0.1C / 0.3C / 0.5C / 1C / 3C / 5C using a CT2100A Blue Electric system provided by Wuhan Blue Electric Electronics Co., Ltd. The test results are shown in Tables 2 and 3.

[0057] Table 2 Electrochemical performance data of each embodiment and Comparative Example 1

[0058]

[0059] Table 3 Reversible capacity retention rates of each embodiment and Comparative Example 1 under different currents.

[0060]

[0061] Table 4. Carbon structural parameters of each embodiment and Comparative Example 1

[0062]

[0063] As shown in Table 2, the reversible capacity, initial coulombic efficiency, and capacity retention after 100 cycles of the negative electrode material of this invention are improved by 13.5%, 5.9%, and 9%, respectively, compared to the undoped pitch-coated graphite material, and also show some improvement compared to sulfur doping. Table 3 shows that the improvement in reversible capacity is due to the formation of CBC / B=O bonds in the coating layer after boron doping, which enhances the adsorption capacity for lithium ions. Table 4 shows that sulfur mainly connects some aromatic layers through cross-linking, increasing the aromatic size and adding more lithium storage sites. Table 4 also shows that since the atomic radius of boron is closer to that of carbon than that of sulfur, boron, after entering the coating layer, increases the interlayer spacing of the coating layer, accelerating the lithium ion transport rate. Furthermore, boron increases the amorphous carbon content in the coating layer, further improving the fast charge / discharge performance of the negative electrode material.

[0064] This invention modifies the graphite coating layer by boron doping. Through a specific and preferred scheme, on the one hand, the doping provides more lithium storage sites and improves the structural order of the coating layer, thereby improving the cycle life of the anode material; on the other hand, the doping widens the interlayer spacing of the carbon material, accelerates lithium ion diffusion, and provides a buffer for lithium ions to enter the interlayer of spherical graphite, thus improving the performance of fast charge and discharge.

[0065] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a pitch-based hard carbon anode coating material for lithium-ion batteries, characterized in that, Includes the following steps: S1. Heat-treat the asphalt-based material to obtain molten asphalt-based material; S2. At a certain temperature, boron-containing substances are added to molten asphalt-based substances, and after high-speed shearing and stirring for 60-90 minutes, the mixture is cooled to room temperature to obtain hard carbon anode coating material.

2. The preparation method of the asphalt-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S1, the asphalt-based material is selected from petroleum asphalt, heavy petroleum oil, and biomass asphalt, as well as any one or more of the following: heavy petroleum oil / naphthalene / anthracene aromatic hydrocarbons. The softening point of the asphalt-based material is between 120 and 180°C.

3. The preparation method of the asphalt-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S1, the heat treatment specifically involves maintaining a temperature of 200-250℃ until the material melts, then holding the temperature constant for 30 minutes to enhance its fluidity while preventing excessive decomposition.

4. The method for preparing an asphalt-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S2, the specific temperature is 200-250℃.

5. The method for preparing an asphalt-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S2, after the molten asphalt-based material is kept at a constant temperature of 200-250℃ for 30-40 minutes, a boron-containing substance is added.

6. The method for preparing an asphalt-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S2, the boron-containing substance is any one or more of boric acid, borax, and boron heterocyclic compounds.

7. The method for preparing a pitch-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S2, the mass of boron-containing substances added generally does not exceed 5% of the mass of the asphalt-based material.

8. The method for preparing an asphalt-based lithium-ion battery hard carbon anode coating material as described in claim 1, characterized in that, In step S2, after the boron-containing substance is dissolved in the asphalt-based substance, it is stirred at a rate of 1500-2000 r / min for 30-60 min.

9. The application of the hard carbon anode coating material prepared by the preparation method according to any one of claims 1-8 in the preparation of anode materials.

10. The application as described in claim 9, characterized in that the application... Specifically, the steps include: mixing natural graphite with hard carbon anode coating material and carbonizing it at high temperature in an inert atmosphere to obtain hard carbon anode material; the mass ratio of natural graphite to hard carbon anode coating material is 100:1-5. The high-temperature carbon treatment specifically involves heating to 1000-1500℃ at a heating rate of 5-10℃ / min and holding at that temperature for 5-10 hours.

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