Liquid lithium battery negative electrode coating material and preparation method thereof

Abstract

The application discloses a kind of liquid lithium battery negative pole coating material and preparation method thereof, belong to lithium battery negative pole material technical field.The application uses ethylene tar as raw material, sequentially through filtration, distillation, polymerization, blending process, produce the liquid lithium battery negative pole coating material provided by the application is used for the coating treatment of lithium battery graphite negative pole material, can be fully wetted with graphite negative pole material, bonding;The "core-shell" structure formed after the graphite negative pole material is treated using the liquid coating material, including core and the coating layer coated on the surface of core.Coating layer is firm, stable, and presents uniformity.The liquid lithium battery negative pole coating material is in liquid state at normal temperature, and has good flowability;Coking value is higher;It is easy to store, convenient for transportation and use.

Description

Technical Field

[0001] This invention belongs to the technical field of lithium battery anode materials, and specifically relates to a liquid lithium battery anode coating material and its preparation method. Background Technology

[0002] In the context of today's global energy crisis, the development of lithium-ion rechargeable battery energy storage technology has gradually become a focus of attention.

[0003] Graphite is commonly used as the negative electrode material for lithium-ion batteries. Graphite has a layered structure, which is suitable for lithium-ion insertion and extraction. However, graphite has poor compatibility with organic solvents and is prone to peeling off of the graphite layer, resulting in poor battery cycle performance. Therefore, it is necessary to modify and coat its surface to improve its electrochemical performance.

[0004] Currently, the lithium battery anode coating material market mainly consists of solid asphalt particles with medium to high temperature softening points (ranging from 120℃ to 280℃), although there are also reports of liquid coating materials.

[0005] Mechanical mixing, commonly known as "dry coating," is a simple and industrially feasible coating method. However, it has the drawback that the coating material is solid at room temperature, and the asphalt powder may agglomerate during the coating process, resulting in uneven coating effect and thus affecting the electrochemical performance of the graphite anode.

[0006] Chinese patent CN115594826A discloses a low-energy synthesis method for a high-efficiency carbon anode coating material. The method involves preheating ethylene tar feedstock to 240℃~250℃, performing gas-liquid separation, and then polymerizing it in a polymerization reactor at 315℃~350℃, causing the polycyclic aromatic hydrocarbon components to undergo a high-temperature condensation reaction. The resulting polymer solution is cooled by heat exchange and then flash-evaporated to obtain the product. This invention produces a low-softening-point coated asphalt, which is in a fluid state at its application temperature and can be thoroughly and uniformly mixed with graphite materials. However, this product is solid at room temperature, which still limits its application.

[0007] Chinese patent CN114989354A discloses a liquid lithium-ion battery negative electrode coating material and its preparation method. This method involves hydrogenating anthracene- and phenanthrene-rich heavy aromatic oil at 360℃–390℃ to remove impurities such as sulfur and nitrogen, yielding a hydrogenated heavy aromatic mixed oil. This mixed oil is then fed into a polymerization reactor with the addition of mixed methylnaphthalene, and polymerized at 280℃–310℃. The material is liquid at room temperature and exhibits good fluidity. However, this process requires hydrogenation, resulting in high energy consumption; furthermore, the control of the hydrogenation process parameters is quite demanding. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, the present invention aims to provide a novel liquid lithium-ion battery anode coating material and its preparation method. This novel coating material and its preparation method are technologically feasible and easily industrialized. The "core-shell" structure formed by treating graphite anode material with this novel liquid coating material results in a firm, stable, and uniform coating layer. This novel liquid coating material is liquid at room temperature and exhibits good fluidity; it has a high coking value, enabling it to fully wet and bond with the graphite anode material; this novel liquid anode coating material is easy to store, transport, and use.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing a novel liquid lithium battery negative electrode coating material includes the following steps:

[0012] (1) Raw material pretreatment: The ethylene tar raw material is filtered using a filter to remove impurities. After purification, the raw material oil is preheated to 110℃~150℃ using a kettle reboiler.

[0013] (2) Distillation: The ethylene tar, after pretreatment, enters a vacuum distillation column for distillation. The bottom temperature of the column is 110-180℃ and the vacuum degree is 1.0-1.5KPa. The top temperature of the column is 110-170℃ and the vacuum degree is 1.0-1.5KPa. The top component is condensed by a condenser and flows into a separatory tank. The oil phase in the separatory tank is refluxed and collected. The reflux ratio is 50%-85%.

[0014] (3) Polymerization: The bottom product after distillation is fed into the polymerization reactor. The reactor temperature is 270-330℃, the vacuum degree is 400-1000Pa, and the reaction time is 40-80 minutes.

[0015] (4) Blending: The polymer liquid obtained in step (3) is first cooled down to 120-160°C by heat exchange and then fed into the blending vessel. Mixed methylnaphthalene is added, and the mixture is stirred continuously. After being kept warm for 2-3 hours, it is cooled to room temperature to obtain the new liquid coating material.

[0016] Furthermore, in step (1), the specific gravity of the ethylene tar feedstock at 20°C is between 0.900 and 1.200 g / cm³. 3 The total sulfur content is less than 1000 ppm, the initial boiling point is ≥160℃, the open flash point is ≥52℃, and the coking value is between 6.00 and 12.00%.

[0017] Furthermore, in step (4), the mass ratio of the polymerization liquid to the mixed methylnaphthalene is 3:1 to 10:1.

[0018] Furthermore, the mixed methylnaphthalene is industrial methylnaphthalene with a total mass fraction of not less than 60% for α-methylnaphthalene and β-methylnaphthalene, a naphthalene content mass fraction of not more than 15.0%, and a water content mass fraction of not more than 1.0%.

[0019] The performance indicators of the liquid lithium battery anode coating material prepared by the above method are: coking value 15-25 wt%; kinematic viscosity at 40℃ 100-300 mm⁻¹ 2 / s; Closed-cup flash point ≥70℃; Sulfur content ≤1100ppm.

[0020] The application of the liquid lithium battery anode coating material prepared by the above method in coating lithium battery anodes is as follows:

[0021] The process of coating graphite anode particles with this liquid coating material includes the following steps:

[0022] (a) Take graphite particles with a particle size of 14 to 25 μm and the coating material and mix them in a mixer. During the mixing process, the temperature is controlled at 80 to 140°C. The weight ratio of the novel liquid coating material to the graphite particles is 1:6 to 1:12.

[0023] (b) Heat the mixer to 160-250°C while maintaining negative pressure to fully coat the graphite particles with the new liquid coating material, and then continue to evaporate to dryness;

[0024] (c) The product obtained after evaporation in step (b) is subjected to carbonization and graphitization treatment to obtain a graphite anode material modified by a novel liquid coating material.

[0025] This invention uses ethylene tar as raw material, and through a series of processes including filtration, distillation, polymerization, and blending, produces the liquid lithium-ion battery anode coating material. The liquid lithium-ion battery anode coating material provided by this invention is used for coating graphite anode materials in lithium-ion batteries, and can fully wet and bond with the graphite anode material. The "core-shell" structure formed after treating the graphite anode material with this liquid coating material includes a core and a coating layer covering the surface of the core. The coating layer is firm, stable, and exhibits uniformity. This liquid lithium-ion battery anode coating material is in a liquid state at room temperature, has good fluidity, a high coking value, is easy to store, and is convenient for transportation and use.

[0026] Compared with existing technologies, the beneficial effects of this invention are:

[0027] 1. Using ethylene tar as raw material, the process of distillation and polymerization effectively improves the coking value of the coating material, thereby shortening the coating time.

[0028] 2. The present invention adopts a distillation-polymerization-blending process, which facilitates production control and the production of liquid coating materials.

[0029] 3. This novel coating material is liquid at room temperature and has good fluidity; it has a high coking value, enabling it to fully wet and bond with graphite anode materials; the core-shell structure is stable and the coating layer is uniform. It is easy to store, transport, and use.

[0030] This invention aims to provide a novel liquid lithium battery anode coating material and its preparation method. The invention uses ethylene tar as raw material and adopts a specific preparation method that is easy to control and convenient to produce. The prepared liquid coating material can improve the uniformity of coating and enhance the electrochemical performance of graphite anode materials. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the negative electrode material according to an embodiment of this application;

[0032] Figure 2 This is a simplified process flow diagram for preparing the liquid coating material according to the present invention.

[0033] In the diagram: 1-Anode material; 2-Covering layer; 3-Core. Detailed Implementation

[0034] 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.

[0035] Example 1

[0036] Example 1:

[0037] This embodiment prepares a novel liquid negative electrode coating material through a process of pretreatment, distillation, polymerization, and blending of raw material ethylene tar, such as... Figure 1 As shown.

[0038] The raw material, ethylene tar, is ethylene cracking tar, a brownish-black liquid with a density of 1.0893 g / cm³ at 20°C. 3 The total sulfur content is 996 ppm, the initial boiling point is ≥160℃, the open flash point is ≥52℃, and the coking value is 10.04%. The distillation range is shown in Table 1 below, and the composition is shown in Table 2.

[0039] Table 1 Distillation Range: (v / v) (All percentages in the table are volume percentages)

[0040] ％ ℃ ％ ℃ ％ ℃ IBP 59℃ 40％ 327℃ 90％ 622℃ 5％ 138℃ 50％ 422℃ 95％ 667℃ 10％ 217℃ 60％ 493℃ 20％ 253℃ 70％ 568℃ 30％ 275℃ 80％ 594℃

[0041] Table 2 Composition Analysis

[0042] Composition (Wt) / % numerical values Total monocyclic aromatic hydrocarbons 15.2 Total bicyclic aromatic hydrocarbons 30.2 Total tricyclic aromatic hydrocarbons 14.3 Total tetracyclic aromatic hydrocarbons 12.1 Total pentacyclic aromatic hydrocarbons 5.1 Total hexacyclic aromatic hydrocarbons and other aromatic hydrocarbons 17.9 gelatinous 5.2

[0043] 2. Pretreatment: The ethylene tar feedstock is filtered to remove impurities, and after purification, the feedstock oil is preheated to 140℃ using a kettle reboiler.

[0044] 3. Distillation: The pretreated ethylene tar is fed into a vacuum distillation column for distillation.

[0045] During distillation, the bottom temperature was 140℃ and the vacuum was 1.3 kPa, while the top temperature was 130℃ and the vacuum was 1.3 kPa. The top component was condensed by the condenser and flowed into the separatory tank, where the oil phase was refluxed and collected. The bottom product entered the polymerization reactor for polymerization. The test results of the bottom product are shown in Table 3.

[0046] Table 3 Analysis of Distillation Column Bottom Material

[0047] softening point Coking value (wt%) Quinoline insoluble matter Ash content (wt%) 31(±1) 11～12 0 0.001

[0048] 4. Polymerization: The bottom product after distillation was fed into the polymerization reactor. The reactor temperature was 270℃, the vacuum degree was 800Pa, and the reaction time was 60 minutes. The polymerization product test results are shown in Table 4.

[0049] Ethylene tar feedstock is mainly composed of polycyclic aromatic hydrocarbons (PAHs), which mainly undergo cracking and condensation reactions. On the one hand, the CH bond breaks, resulting in dehydrogenation, and the C-C bond of the aromatic side chain breaks, resulting in cracking. On the other hand, aromatic molecules undergo condensation, transforming the original 3- to 5-cyclic aromatic hydrocarbons into cyclic aromatic hydrocarbons with more carbon atoms.

[0050] The polymerization process is carried out in a polymerization reactor.

[0051] (5) Blending: The polymer liquid obtained in step (3) is first cooled down to 140°C by heat exchange and then fed into the blending vessel. Mixed methylnaphthalene is added, and the mixture is stirred continuously. After 2.5 hours of heat preservation, it is cooled to room temperature to obtain the new liquid coating material.

[0052] In the mixed methylnaphthalene, the sum of the mass fractions of α-methylnaphthalene and β-methylnaphthalene is 61%, and the mass fraction of naphthalene content is 14%.

[0053] The polymerization product, which was polymerized at a polymerization temperature of 270℃, was cooled by heat exchange to 140℃ and then mixed methylnaphthalene was added. The sulfur content of the mixed methylnaphthalene was 853 ppm, and the ratio of the polymerization product to the mixed methylnaphthalene was 4.6:1. The coking value of the new coating material obtained after blending is shown in Table 5.

[0054] Example 2:

[0055] In step 4, the reactor temperature during polymerization is 280℃. In the mixed methylnaphthalene, the sum of the mass fractions of α-methylnaphthalene and β-methylnaphthalene is 62%, and the mass fraction of naphthalene content is 13%.

[0056] Other aspects are the same as in Example 1. The detection results of the polymerization products are shown in Table 4. The coking values ​​of the novel coating material obtained after blending are shown in Table 5.

[0057] Example 3:

[0058] In step 4, the reactor temperature during polymerization is 290℃. In the mixed methylnaphthalene, the sum of the mass fractions of α-methylnaphthalene and β-methylnaphthalene is 63%, and the mass fraction of naphthalene content is 12%.

[0059] Other aspects are the same as in Example 1. The detection results of the polymerization products are shown in Table 4. The coking values ​​of the novel coating material obtained after blending are shown in Table 5.

[0060] Example 4:

[0061] In step 4, the reactor temperature during polymerization is 300℃. In the mixed methylnaphthalene, the sum of the mass fractions of α-methylnaphthalene and β-methylnaphthalene is 64%, and the mass fraction of naphthalene content is 11%.

[0062] Other aspects are the same as in Example 1. The detection results of the polymerization products are shown in Table 4. The coking values ​​of the novel coating material obtained after blending are shown in Table 5.

[0063] Table 4. Analysis of Polymer Products

[0064] Example Softening point / °C Coking value / % Quinoline insolubles / % Ash content / % Example 1 36(±1) 21～22 0 0.001 Example 2 39(±1) 23～24 0 0.001 Example 3 43(±1) 25～26 0 0.001 Example 4 47(±1) 28～29 0 0.001

[0065] Table 5. Test data of novel liquid coating materials

[0066]

[0067]

[0068] The coating materials prepared by mixing the materials from Examples 1, 2, 3, and 4 were subjected to performance testing. The test data are shown in Table 6.

[0069] Table 6 Technical Specifications of Novel Liquid Coating Materials

[0070] Example <![CDATA[40℃ kinematic viscosity / mm 2 / s]]> Closed-cup flash point / ℃ Sulfur content / ppm Example 1 221.3 84 784 Example 2 240.9 88 790 Example 3 256.6 89 792 Example 4 275.4 91 800

[0071] Application Example 1:

[0072] The coating material prepared in Example 1 is used for coating lithium battery anode materials, including the following steps:

[0073] (a) Take graphite particles with a particle size of 14-20 μm and the coating material and mix them in a mixer. During the mixing process, the temperature is controlled at 120°C. The weight ratio of the novel liquid coating material to the graphite particles is 1:8.

[0074] (b) Heat the mixer to 200°C while maintaining negative pressure to fully coat the graphite particles with the new liquid coating material and continue to evaporate to dryness;

[0075] (c) The product obtained after evaporation in step (b) is subjected to carbonization and graphitization treatment to obtain a novel liquid-coated graphite anode material. The average particle size and specific surface area of ​​the anode material were measured, and the test data are shown in Table 7.

[0076] Application Example 2

[0077] The coating material prepared in Example 2 is used for coating lithium battery anode materials, including the following steps:

[0078] (a) Take graphite particles with a particle size of 14-20 μm and the coating material and mix them in a mixer. During the mixing process, the temperature is controlled at 120°C. The weight ratio of the novel liquid coating material to the graphite particles is 1:8.

[0079] (b) Heat the mixer to 200°C while maintaining negative pressure to fully coat the graphite particles with the new liquid coating material and continue to evaporate to dryness;

[0080] (c) The product obtained after evaporation in step (b) is subjected to carbonization and graphitization treatment to obtain a novel liquid-coated graphite anode material. The average particle size and specific surface area of ​​the anode material were measured, and the test data are shown in Table 7.

[0081] Application Example 3

[0082] The coating material prepared in Example 3 is used for coating lithium battery anode materials, including the following steps:

[0083] (a) Take graphite particles with a particle size of 14-20 μm and the coating material and mix them in a mixer. During the mixing process, the temperature is controlled at 120°C. The weight ratio of the novel liquid coating material to the graphite particles is 1:8.

[0084] (b) Heat the mixer to 200°C while maintaining negative pressure to fully coat the graphite particles with the new liquid coating material and continue to evaporate to dryness;

[0085] (c) The product obtained after evaporation in step (b) is subjected to carbonization and graphitization treatment to obtain a novel liquid-coated graphite anode material. The average particle size and specific surface area of ​​the anode material were measured, and the test data are shown in Table 7.

[0086] Application Example 4

[0087] The coating material obtained in Example 4 is used for coating lithium battery anode materials, including the following steps:

[0088] (a) Take graphite particles with a particle size of 14-20 μm and the coating material and mix them in a mixer. During the mixing process, the temperature is controlled at 120°C. The weight ratio of the novel liquid coating material to the graphite particles is 1:8.

[0089] (b) Heat the mixer to 200°C while maintaining negative pressure to fully coat the graphite particles with the new liquid coating material and continue to evaporate to dryness;

[0090] (c) The product obtained after evaporation in step (b) is subjected to carbonization and graphitization treatment to obtain a novel liquid-coated graphite anode material. The average particle size and specific surface area of ​​the anode material were measured, and the test data are shown in Table 7.

[0091] Application Comparative Example 1.

[0092] Graphite particles of 14-20 μm were collected. Solid-phase coated asphalt powder and the collected 14-20 μm graphite particles were thoroughly mixed at a ratio of 1:14 using a solid-phase mixing method. The mixture was then molded into blocks using a press, carbonized and graphitized, pulverized, and sieved to obtain 14-20 μm graphite anode material coated with solid-phase asphalt, which was used as a control. The test data are shown in Table 7.

[0093] Application Comparative Example 2

[0094] The coating material obtained by Chinese patent CN114989354A is used for coating lithium battery anode materials, including the following steps:

[0095] Graphite particles with a particle size of 14–20 μm and the coating material prepared by Chinese Patent CN114989354A were mixed in a mixer. The temperature was controlled at 120℃ during mixing, and the weight ratio of the liquid coating material prepared by Chinese Patent CN114989354A to the graphite particles was 1:8. The mixer was then heated to 200℃ while maintaining negative pressure to ensure that the liquid coating material prepared by Chinese Patent CN114989354A fully coated the graphite particles, and the mixture was continuously evaporated to dryness. The resulting product was then subjected to carbonization and graphitization treatments to obtain the graphite anode material modified by the coating material prepared by Chinese Patent CN114989354A. The average particle size and specific surface area of ​​the anode material were measured, and the test data are shown in Table 7.

[0096] The test data are shown in Table 7.

[0097] Table 7. Test data of modified graphite anode materials

[0098]

[0099] As can be seen from the test results in Table 7, the specific surface area of ​​the liquid-coated anode material is significantly smaller than that of the solid-coated anode material, indicating that the liquid-coated material has a more uniform coating.

[0100] The initial discharge capacity and initial charge-discharge efficiency of the graphite anode materials prepared using Examples 1-4 and Comparative Examples 1-2 were tested, and the test data are shown in Table 8.

[0101] Table 8 Electrochemical performance test data

[0102] Serial Number Initial discharge capacity mAh / g First charge / discharge efficiency % Application Example 1 362.4 94.1 Application Example 2 361.2 95.6 Application Example 3 363.5 96.2 Application Example 4 361.0 95.3 Application Comparative Example 1 353.0 91.0 Application Comparative Example 2 358.6 92.8

[0103] As shown in Table 8, the liquid anode coating material prepared according to this invention effectively coats the graphite anode of lithium batteries, resulting in better conductivity and stronger adhesion. The coating significantly improves the initial efficiency of the graphite anode material, effectively enhancing the electrochemical performance of lithium batteries. Application Example 3, prepared in Example 3, demonstrates the best performance. In Comparative Example 2, the coating layer was too thick, increasing the resistance to lithium ion entry and exit, causing some lithium ions to fail to escape from the graphite anode, leading to a decrease in capacity. Table 8 also shows that the liquid coating material prepared by Chinese Patent CN114989354A is worse than dry coating for coating graphite anodes, but not as good as this patent.

[0104] The comparison results between the preferred embodiment 3 of the present invention and the prior art are shown in the table below:

[0105]

[0106]

[0107]

[0108] 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 liquid lithium battery negative electrode coating material, characterized in that, Includes the following steps: (1) Raw material pretreatment: The ethylene tar raw material is filtered to remove impurities and purified. The raw material oil is then preheated to 110℃~150℃ using a kettle reboiler. (2) Distillation: The ethylene tar is pretreated and then distilled in a vacuum distillation column. The bottom temperature of the column is 110-180℃ and the vacuum degree is 1.0-1.5KPa. The top temperature of the column is 110-170℃ and the vacuum degree is 1.0-1.5KPa. The top component is condensed by the condenser and flows into the separator. The oil phase in the separator is refluxed and collected. (3) Polymerization: The bottom product after distillation is fed into the polymerization reactor. The reactor temperature is 270-330℃, the vacuum degree is 400-1000Pa, and the reaction time is 40-80 minutes. (4) Blending: The polymer liquid obtained in step (3) is first cooled down to 120-160°C by heat exchange and then fed into the blending tank. Mixed methylnaphthalene is added, and the mixture is stirred continuously. The mixture is kept warm for 2-3 hours and then cooled to room temperature to obtain the liquid coating material. The mixed methylnaphthalene is industrial methylnaphthalene with a total mass fraction of not less than 60% for α-methylnaphthalene and β-methylnaphthalene, a naphthalene content mass fraction of not more than 15.0%, and a water content mass fraction of not more than 1.0%.

2. The method for preparing a liquid lithium battery negative electrode coating material as described in claim 1, characterized in that, In step (1), the specific gravity of the ethylene tar feedstock at 20°C is between 0.900 and 1.200 / cm³. 3 The total sulfur content is less than 1000 ppm, the initial boiling point is ≥160℃, the open flash point is ≥52℃, and the coking value is between 6.00 and 12.00%.

3. The method for preparing a liquid lithium battery negative electrode coating material as described in claim 2, characterized in that, In step (4), the mass ratio of the polymerization liquid to the mixed methylnaphthalene is 3:1 to 10:

1.

4. The application of the liquid lithium battery anode coating material prepared by the preparation method according to any one of claims 1-3 on the coating of lithium battery anodes.

5. The application of the liquid lithium battery anode coating material as described in claim 4 on the coating of lithium battery anodes, characterized in that, The process of coating graphite anode particles with this liquid coating material includes the following steps: (a) Take graphite particles with a particle size of 14-25 μm and the coating material and mix them in a mixer. During the mixing process, the temperature is controlled at 80-140°C and the weight ratio of liquid coating material to graphite particles is 1:6-1:

12. (b) Heat the mixer to 160-250°C while maintaining negative pressure to ensure that the liquid coating material fully coats the graphite particles, and then continue to evaporate to dryness; (c) The product obtained after evaporation in step (b) is subjected to carbonization and graphitization treatment to obtain a graphite anode material modified by liquid coating material.

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