A dry-coated negative electrode material and a processing method thereof

Abstract

The present invention belongs to the technical field of secondary battery materials, and more specifically, relates to a dry-coated negative electrode material and a processing method thereof. The method of the present invention comprises the following steps: taking 150-160 parts of natural graphite, 10-12 parts of monosaccharide, 10-12 parts of disaccharide and 15-20 parts of high molecular weight polysaccharide by weight; mixing the raw materials, firstly subjecting the raw materials to ball milling for 10-15 minutes at a temperature of 150-160° C.; continuing to subject the raw materials to ball milling for 10-20 minutes at a temperature of 169-171° C.; further subjecting the raw materials to ball milling for 8-10 minutes at a temperature of 179-181° C.; subsequently subjecting the raw materials to ball milling for 10-15 minutes at a temperature of 185-188° C.; and finally subjecting the raw materials to ball milling for 10-12 minutes at a temperature of 210-212° C.; cooling, discharging and obtaining ball milling material; heating the obtained ball milling material to 780-800° C. under an inert gas protection state, high temperature carbonizing, cooling and discharging and obtaining a dry coated negative electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary battery materials, and more specifically, relates to a dry-coated negative electrode material and a processing method thereof. Background Art

[0002] Graphite used as negative electrode material has a conventional average particle size between 10-20 μm. Graphite particles of this size have a large specific surface area, surface activity and surface energy. Therefore, the particles are prone to agglomeration, resulting in a decrease in their dispersion performance, which restricts their industrial application.

[0003] At present, the coating of ultrafine powders is divided into dry coating and wet coating. Among them, the dry coating includes mechanical mixing method and solid phase reaction method.

[0004] For the mechanical mixing method, it uses mechanical forces such as extrusion, impact, shearing, and friction to evenly distribute the modifier on the outer surface of the powder particles, so that various components can penetrate and diffuse into each other to form a coating. The main methods currently used are ball grinding, stirring grinding, and high-speed airflow impact. The advantages of this method are short processing time, easy control of the reaction process, continuous batch production, and more conducive to the coating of powder particles with various resins, paraffin-like substances, and fluidity modifiers.

[0005] For the solid phase reaction method, several metal salts or metal oxides are fully mixed and ground according to a formula, and then calcined to directly obtain ultrafine coated powder through solid phase reaction. Summary of the invention

[0006] The technical problem to be solved by the present invention is that it is difficult to form a uniform coating layer on the surface of the negative electrode material by a dry coating process, which leads to differences in the conductivity of ions and electrons in different parts of the product during the charging and discharging process, especially when charging and discharging at a high rate, which easily leads to the problem of rapid attenuation of battery performance. The present invention provides a dry-coated negative electrode material and a processing method thereof.

[0007] The purpose of the present invention is to provide a dry-coated negative electrode material.

[0008] Another object of the present invention is to provide a method for processing dry-coated negative electrode materials.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a dry-coated negative electrode material, the specific preparation steps comprising:

[0011] Raw materials preparation:

[0012] By weight, take 150-160 parts of natural graphite, 10-12 parts of monosaccharide, 10-12 parts of disaccharide, and 15-20 parts of high molecular weight polysaccharide;

[0013] Ball milling:

[0014] After mixing the raw materials, ball milling begins.

[0015] First, ball mill and mix at 150-160℃ for 10-15min;

[0016] Continue to ball mill and mix at a temperature of 169-171°C for 10-20 minutes;

[0017] Then, the mixture was ball-milled at 179-181°C for 8-10 minutes;

[0018] Then, the mixture was ball-milled at 185-188°C for 10-15 minutes;

[0019] Finally, ball milling was performed at a temperature of 210-212°C for 10-12 minutes;

[0020] Cooling, discharging, and obtaining ball abrasive;

[0021] High temperature carbonization:

[0022] The obtained ball milled material is heated to 780-800°C under the protection of inert gas, carbonized at high temperature, cooled, and discharged to obtain the dry-coated negative electrode material.

[0023] The above scheme uses monosaccharides, disaccharides and high molecular weight polysaccharides as carbon sources, and cooperates with multi-step ball milling reactions under different temperature conditions to achieve a uniform coating effect;

[0024] Specifically, first, during ball milling at 150-160°C, monosaccharides and disaccharides begin to melt, and the viscosity of the system increases relatively, so that relative friction can occur between the materials, which is conducive to the uniform mixing of the materials; as the temperature further rises to 169-171°C, the monosaccharides and disaccharides are fully melted and begin to dehydrate. At this time, the viscosity of the system is smaller than that at the initial melting stage, so that the high-molecular polysaccharide can be fully coated on the graphite surface under the action of the molten monosaccharides and disaccharides. As the temperature further rises, the small-molecule monosaccharides and polysaccharides begin to react further, and finally condense to form a high molecule, thereby forming a firm coating on the graphite surface;

[0025] On the basis of the above coating, high-temperature carbonization is further carried out to convert the coating layer into a carbon coating layer, thereby achieving uniform carbon coating on the graphite surface; and, benefiting from the condensation reaction occurring during the above coating process, the carbon coating layer can also be firmly adhered to the graphite surface to prevent powdering during use.

[0026] Furthermore, the ball milling mixing further comprises:

[0027] First, at a temperature of 150-160°C, a rotation speed of 500-550r / min, and a revolution speed of 180-200r / min, ball milling is performed for 10-15 minutes;

[0028] Continue to ball mill and mix for 10-20 minutes at a temperature of 169-171°C, a rotation speed of 500-550 r / min, and a revolution speed of 180-200 r / min;

[0029] Then, the mixture is ball-milled for 8-10 minutes at a temperature of 179-181°C, a rotation speed of 400-450 r / min, and a revolution speed of 180-200 r / min;

[0030] Then, the mixture was ball-milled for 10-15 minutes at a temperature of 185-188°C, a rotation speed of 300-350 r / min, and a revolution speed of 180-200 r / min;

[0031] Finally, the mixture was ball-milled for 10-12 minutes at a temperature of 210-212°C, a rotation speed of 500-550 r / min, and a revolution speed of 180-200 r / min.

[0032] Cooling, discharging and obtaining ball abrasive.

[0033] Furthermore, at different processing temperatures, a suitable ball milling speed is matched so that the material can be evenly coated on the graphite surface during the ball milling process.

[0034] Furthermore, the raw material preparation also includes:

[0035] By weight, take 150-160 parts of natural graphite, 10-12 parts of monosaccharide, 10-12 parts of disaccharide, 15-20 parts of high molecular weight polysaccharide, and 4-6 parts of amino acid.

[0036] In the above scheme, by further adding amino acids, in addition to participating in the condensation reaction of the above monosaccharides and disaccharides, amino acids can also achieve N element doping of the carbon coating during the high-temperature carbonization process, thereby further improving the conductivity of the carbon coating and improving the fast charging capability of the product.

[0037] Furthermore, the amino acid is selected from any one of alanine, arginine, aspartic acid, glycine, phenylalanine, glutamic acid, proline, tryptophan and lysine.

[0038] Furthermore, the monosaccharide is selected from any one of glucose and fructose.

[0039] Furthermore, the disaccharide is selected from any one of sucrose, lactose, maltose and trehalose.

[0040] Furthermore, the high molecular weight polysaccharide is selected from any one of starch, cellulose, mannan and chitosan.

[0041] Furthermore, the natural graphite is spherical natural graphite;

[0042] The D50 of the spherical natural graphite is 12-16 μm;

[0043] The particle size distribution range of the spherical natural graphite is 1-30 μm;

[0044] The sphericity of the spherical natural graphite is 8.8-9.0.

[0045] By selecting natural graphite with high sphericity and controlling its particle size distribution within a relatively small range, the coating process can be made more controllable, thereby achieving uniform coating of the entire product.

[0046] A dry-coated negative electrode material is prepared by the above-mentioned preparation method. DETAILED DESCRIPTION

[0047] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0048] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0049] Example 1

[0050] Raw materials preparation:

[0051] By weight, take 150 parts of natural graphite, 10 parts of monosaccharide, 10 parts of disaccharide, 15 parts of high molecular weight polysaccharide, and 4 parts of amino acid;

[0052] Ball milling:

[0053] Pour the mixed raw materials into the ball mill, add ball mill beads at a ball-to-material mass ratio of 1:30, and start ball milling.

[0054] First, the mixture was ball-milled for 10 min at a temperature of 150°C, a rotation speed of 500 r / min, and a revolution speed of 180 r / min;

[0055] The mixture was then ball-milled for 10 min at a temperature of 169°C, a rotation speed of 500 r / min, and a revolution speed of 180 r / min.

[0056] Then, the mixture was ball-milled for 8 min at a temperature of 179°C, a rotation speed of 400 r / min, and a revolution speed of 180 r / min.

[0057] Then, the mixture was ball-milled for 10 min at a temperature of 185°C, a rotation speed of 300 r / min, and a revolution speed of 180 r / min.

[0058] Finally, the mixture was ball-milled for 10 min at a temperature of 210°C, a rotation speed of 500 r / min, and a revolution speed of 180 r / min.

[0059] After the ball milling is completed, the material is discharged, cooled to room temperature, and then broken into powder;

[0060] The obtained powder was then transferred into a carbonization furnace, and argon was introduced into the furnace as a protective gas at a rate of 100 L / min. In an argon atmosphere, the temperature was raised to 780°C at a rate of 5°C / min. After high-temperature carbonization for 2 hours, the powder was cooled to room temperature with the furnace and discharged to obtain a dry-coated negative electrode material.

[0061] The monosaccharide is selected from glucose;

[0062] The disaccharide is selected from sucrose;

[0063] The high molecular weight polysaccharide is selected from starch;

[0064] The amino acid is selected from alanine;

[0065] The natural graphite is spherical natural graphite;

[0066] The D50 of the spherical natural graphite is 12 μm;

[0067] The particle size distribution range of the spherical natural graphite is 1-30 μm;

[0068] The sphericity of the spherical natural graphite is 8.8.

[0069] Example 2

[0070] Raw materials preparation:

[0071] By weight, take 155 parts of natural graphite, 11 parts of monosaccharide, 11 parts of disaccharide, 18 parts of high molecular weight polysaccharide, and 5 parts of amino acid;

[0072] Ball milling:

[0073] Pour the mixed raw materials into the ball mill, add ball mill beads at a ball-to-material mass ratio of 1:30, and start ball milling.

[0074] First, the mixture was ball-milled for 12 min at a temperature of 155°C, a rotation speed of 520 r / min, and a revolution speed of 190 r / min;

[0075] The mixture was then ball-milled for 15 min at a temperature of 170°C, a rotation speed of 520 r / min, and a revolution speed of 190 r / min.

[0076] Then, the mixture was ball-milled for 9 minutes at a temperature of 180°C, a rotation speed of 420 r / min, and a revolution speed of 190 r / min;

[0077] Then, the mixture was ball-milled for 12 min at a temperature of 186°C, a rotation speed of 320 r / min, and a revolution speed of 190 r / min.

[0078] Finally, the mixture was ball-milled for 11 min at a temperature of 211°C, a rotation speed of 520 r / min, and a revolution speed of 190 r / min.

[0079] After the ball milling is completed, the material is discharged, cooled to room temperature, and then broken into powder;

[0080] The obtained powder was then transferred into a carbonization furnace, and argon gas was introduced into the furnace as a protective gas at a rate of 110 L / min. In an argon atmosphere, the temperature was raised to 790°C at a rate of 6°C / min. After high-temperature carbonization for 3 hours, the powder was cooled to room temperature with the furnace and discharged to obtain a dry-coated negative electrode material.

[0081] The monosaccharide is selected from fructose;

[0082] The disaccharide is selected from maltose;

[0083] The polymer polysaccharide is selected from cellulose;

[0084] The amino acid is selected from arginine;

[0085] The natural graphite is spherical natural graphite;

[0086] The D50 of the spherical natural graphite is 14 μm;

[0087] The particle size distribution range of the spherical natural graphite is 1-30 μm;

[0088] The sphericity of the spherical natural graphite is 8.9.

[0089] Example 3

[0090] Raw materials preparation:

[0091] By weight, take 160 parts of natural graphite, 12 parts of monosaccharide, 12 parts of disaccharide, 20 parts of high molecular weight polysaccharide, and 6 parts of amino acid;

[0092] Ball milling:

[0093] Pour the mixed raw materials into the ball mill, add ball mill beads at a ball-to-material mass ratio of 1:30, and start ball milling.

[0094] First, the mixture was ball-milled for 15 min at a temperature of 160°C, a rotation speed of 550 r / min, and a revolution speed of 200 r / min;

[0095] The mixture was then ball-milled for 20 min at a temperature of 171°C, a rotation speed of 550 r / min, and a revolution speed of 200 r / min.

[0096] Then, the mixture was ball-milled for 10 min at a temperature of 181°C, a rotation speed of 450 r / min, and a revolution speed of 200 r / min.

[0097] Then, the mixture was ball-milled for 15 min at a temperature of 188°C, a rotation speed of 350 r / min, and a revolution speed of 200 r / min.

[0098] Finally, the mixture was ball-milled for 12 min at a temperature of 212°C, a rotation speed of 550 r / min, and a revolution speed of 200 r / min.

[0099] After the ball milling is completed, the material is discharged, cooled to room temperature, and then broken into powder;

[0100] The obtained powder was then transferred into a carbonization furnace, and argon was introduced into the furnace as a protective gas at a rate of 120 L / min. In an argon atmosphere, the temperature was raised to 800°C at a rate of 8°C / min. After high-temperature carbonization for 4 hours, the powder was cooled to room temperature with the furnace and discharged to obtain a dry-coated negative electrode material.

[0101] The monosaccharide is selected from glucose;

[0102] The disaccharide is selected from trehalose;

[0103] The high molecular weight polysaccharide is selected from mannan;

[0104] The amino acid is selected from alanine;

[0105] The natural graphite is spherical natural graphite;

[0106] The D50 of the spherical natural graphite is 16 μm;

[0107] The particle size distribution range of the spherical natural graphite is 1-30 μm;

[0108] The sphericity of the spherical natural graphite is 9.0.

[0109] Example 4

[0110] Compared with Example 1, this example is different in that no amino acid is added and other conditions remain unchanged.

[0111] Example 5

[0112] The present embodiment is different from the embodiment 1 in that the particle size distribution range of the spherical natural graphite is 0.1-80 μm, and the other conditions remain unchanged.

[0113] Example 6

[0114] Compared with Example 1, the present embodiment differs in that the sphericity of the natural graphite is 8.5, and the other conditions remain unchanged.

[0115] Comparative Example 1

[0116] The difference between this comparative example and Example 1 is that no monosaccharide and disaccharide are added, and the other conditions remain unchanged.

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that the ball milling mixing process is different. Specifically, the ball milling mixing of this comparative example includes:

[0119] Pour the mixed raw materials into the ball mill, add ball mill beads at a ball-to-material mass ratio of 1:30, and start ball milling.

[0120] The mixture was ball milled for 48 min at a temperature of 150°C, a rotation speed of 500 r / min, and a revolution speed of 180 r / min.

[0121] After the ball milling mixing is completed, the material is discharged, cooled to room temperature, and then broken into powder.

[0122] The rest of the conditions remain unchanged.

[0123] Comparative Example 3

[0124] The difference between this comparative example and Example 1 is that the ball milling mixing process is different. Specifically, the ball milling mixing of this comparative example includes:

[0125] Pour the mixed raw materials into the ball mill, add ball mill beads at a ball-to-material mass ratio of 1:30, and start ball milling.

[0126] The mixture was ball-milled for 48 min at a temperature of 210°C, a rotation speed of 500 r / min, and a revolution speed of 180 r / min.

[0127] After the ball milling mixing is completed, the material is discharged, cooled to room temperature, and then broken into powder.

[0128] The rest of the conditions remain unchanged.

[0129] The performance tests were performed on the products obtained in the examples and comparative examples. The specific test methods and test results are as follows:

[0130] The products obtained in the above embodiments or comparative examples were used as negative electrode active materials, respectively. The negative electrode active material, conductive carbon black Super-P and carboxymethyl cellulose were mixed in a mass ratio of 9:0.5:0.5, and deionized water was added as a solvent. The mixture was stirred at a speed of 300 r / min for 12 h to prepare a negative electrode slurry. Subsequently, the negative electrode slurry was scraped on the surface of the copper foil, and the negative electrode was dried at 100° C. for 12 h to obtain a negative electrode sheet, which was cut into discs with a diameter of 12 mm, wherein the surface density of the active substance on the surface of the negative electrode sheet was controlled at 2.75 mg / cm2. In a glove box, a CR2032 battery shell was selected, a lithium sheet was used as a counter electrode and a reference electrode, and a porous polypropylene film (Clegard 2320) was used as a reference electrode. ) is used as a diaphragm, and a button-type half-cell is assembled in the order of a negative electrode sheet, a diaphragm, an electrolyte, a lithium sheet, a gasket, and a shell. The electrolyte is selected as a ternary mixture of 1 mol / L lithium hexafluorophosphate dissolved in a volume ratio of 1:1:1 of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate; after the battery is assembled and sealed, it is left to stand at room temperature for 36 hours for electrochemical performance testing; a CT2001A blue electric test system is used with a test voltage range of 0.005-3.0V to perform constant current charge and discharge tests on the above-mentioned battery; rate performance tests are performed at 0.2C, 0.6C, and 2.0C rates. Specifically, the capacity retention rate of the battery is tested after 500 cycles of charge and discharge at the corresponding current density. The ambient temperature for the electrochemical performance test is 25°C;

[0131] The detailed test results are shown in Table 1:

[0132] Table 1: Product performance test results

[0133] 0.2C capacity retention rate / % 0.6C capacity retention rate / % 2.0C capacity retention rate / % Example 1 96.2 94.2 90.0 Example 2 96.4 94.3 90.1 Example 3 96.5 94.4 90.0 Example 4 94.1 92.0 87.8 Example 5 94.0 91.8 87.5 Example 6 94.4 92.1 87.9 Comparative Example 1 90.4 86.5 80.9 Comparative Example 2 90.3 86.6 81.1 Comparative Example 3 90.1 86.2 80.2

[0134] It can be seen from the test results in Table 1 that the product obtained by the present invention has a good cycle life, especially, it still has a high capacity retention rate when charged and discharged at a high rate.

[0135] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a dry coated negative electrode material, characterized in that: The specific preparation steps include: Raw materials preparation: By weight, take 150-160 parts of natural graphite, 10-12 parts of monosaccharide, 10-12 parts of disaccharide, 15-20 parts of high molecular weight polysaccharide, and 4-6 parts of amino acid; Ball milling: After mixing the raw materials, ball milling begins. First, ball mill and mix at 150-160℃ for 10-15min; Continue to ball mill and mix at a temperature of 169-171°C for 10-20 minutes; Then, the mixture was ball-milled at 179-181°C for 8-10 minutes; Then, the mixture was ball-milled at 185-188°C for 10-15 minutes; Finally, ball milling was performed at a temperature of 210-212°C for 10-12 minutes; Cooling, discharging, and obtaining ball abrasive; High temperature carbonization: The obtained ball milled material is heated to 780-800°C under the protection of inert gas, carbonized at high temperature, cooled, and discharged to obtain the dry-coated negative electrode material.

2. The method for preparing a dry-coated negative electrode material according to claim 1, characterized in that: The ball milling mixing also includes: First, at a temperature of 150-160°C, a rotation speed of 500-550r / min, and a revolution speed of 180-200r / min, ball milling is performed for 10-15 minutes; Continue to ball mill and mix for 10-20 minutes at a temperature of 169-171°C, a rotation speed of 500-550 r / min, and a revolution speed of 180-200 r / min; Then, the mixture is ball-milled for 8-10 minutes at a temperature of 179-181°C, a rotation speed of 400-450 r / min, and a revolution speed of 180-200 r / min; Then, the mixture was ball-milled for 10-15 minutes at a temperature of 185-188°C, a rotation speed of 300-350 r / min, and a revolution speed of 180-200 r / min; Finally, the mixture was ball milled for 10-12 minutes at a temperature of 210-212°C, a rotation speed of 500-550 r / min, and a revolution speed of 180-200 r / min. Cooling, discharging and obtaining ball abrasive.

3. A method for preparing a dry coated negative electrode material according to any one of claims 1 to 2, characterized in that: The monosaccharide is selected from any one of glucose and fructose.

4. The method for preparing a dry-coated negative electrode material according to any one of claims 1 to 2, characterized in that: The disaccharide is selected from any one of sucrose, lactose, maltose and trehalose.

5. The method for preparing a dry-coated negative electrode material according to any one of claims 1 to 2, characterized in that: The high molecular weight polysaccharide is selected from any one of starch, cellulose, mannan and chitosan.

6. The method for preparing a dry-coated negative electrode material according to claim 1, characterized in that: The amino acid is selected from any one of alanine, arginine, aspartic acid, glycine, phenylalanine, glutamic acid, proline, tryptophan and lysine.

7. A method for preparing a dry coated negative electrode material according to any one of claims 1 to 2, characterized in that: The natural graphite is spherical natural graphite; The D50 of the spherical natural graphite is 12-16 μm; The particle size distribution range of the spherical natural graphite is 1-30 μm; The sphericity of the spherical natural graphite is 8.8-9.

0.

8. A dry-coated negative electrode material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.