Graphite anode materials for lithium batteries and their preparation methods

Abstract

The present application relates to the technical field of lithium battery negative electrode material, and particularly relates to a lithium battery graphite negative electrode material and a preparation method thereof. The preparation method of the graphite negative electrode material comprises the following steps: taking natural graphite as raw material, performing the steps of crushing, shaping and spheroidizing shaping in a high-pressure fan suction airflow pulverizer to obtain a pre-product graphite powder, and performing secondary crushing and spheroidizing on the modified graphite powder; the main elements added in the modification are silicon, titanium and cerium, etc., and the elements produce effects through mutual cooperation; the graphite negative electrode material prepared through modification and secondary spheroidizing improves the mechanical strength and wear resistance of the material, is beneficial to secondary spheroidizing, makes the spheroidization degree of the material better, and inhibits volume expansion, so that the conductivity and structural stability of the material can be improved, and the cycle service life in the battery and the electrochemical performance can be improved.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, specifically to lithium battery graphite anode materials and their preparation methods. Background Technology

[0002] Natural graphite is processed into spherical shapes before being used as a negative electrode material in lithium-ion batteries, rather than being directly applied after being crushed. This is primarily due to the working principle of lithium-ion batteries. Simply put, the operation of a lithium-ion battery is its charging and discharging process, which involves Li+ ions moving in and out of spherical graphite. Because graphite has a layered structure and is anisotropic, Li+ ions can more easily move in and out between the graphite layers. Processing graphite into spherical shapes minimizes directional restrictions on Li+ ions as they move in and out of the graphite layers, thus improving the performance of the lithium-ion battery.

[0003] There are many processing methods for carbon materials used in lithium-ion battery anodes. Natural graphite must be shaped and modified to improve battery performance. The main methods for processing natural graphite into anode materials are spheroidization, surface oxidation, surface carbonization, and graphitization. Spheroidization can further agglomerate to form secondary particles with high sphericity and concentrated particle size, reducing surface defects and anisotropy, and improving the material's structural stability. Lithium-ion batteries primarily use graphite as the anode material, but natural graphite anode materials suffer from low compaction density and poor rate performance, resulting in low energy density, poor power performance, and low high-current charge / discharge performance in lithium-ion batteries. Therefore, graphite modification and secondary spheroidization are necessary to improve battery performance. Summary of the Invention

[0004] The purpose of this invention is to provide a graphite anode material for lithium batteries and its preparation method, which solves the problems of volume expansion, electrochemical performance and structural stability of the anode material itself during lithium intercalation.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing graphite anode materials for lithium-ion batteries includes the following steps:

[0007] S1. The flake graphite is crushed and graded multiple times to obtain graphite powder of the target particle size; then the graphite powder of the target particle size is spheroidized to obtain spheroidized graphite powder.

[0008] S2. First-stage spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water are stirred at room temperature for 2-5 hours. After stirring, surfactant II, titanium source and cerium source are added and stirred for 6-8 hours. After drying, grinding and sintering, modified graphite anode material is obtained.

[0009] S3. The modified graphite anode material is subjected to a secondary spheroidization process to obtain a secondary spheroidized modified graphite anode material.

[0010] Furthermore, the flake graphite uses natural flake graphite with a particle size of 32-500 mesh and a carbon content of over 92%.

[0011] Furthermore, the crushing parameters are set to 800-1600 rpm, and the parameters for a single spheroidization process are 800-1500 rpm and 15-80 minutes.

[0012] Furthermore, the ratio of the amount of primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water is 30-60g: 10-20g: 20-35g: 5-25g: 200-400mL.

[0013] Furthermore, the silicon source is tetraethyl silicate, surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0014] Furthermore, the ratio of surfactant II, titanium source, and cerium source is 25-75mL: 10-25g: 15-30g.

[0015] Furthermore, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridine chloride, and the cerium source is cerium nitrate.

[0016] Furthermore, the sintering temperature is 600-800℃, and the total sintering time is 8-16h.

[0017] Furthermore, the secondary spheroidizing equipment operates at a speed of 600-1000 rpm for 10-50 minutes.

[0018] Furthermore, the graphite anode material for this lithium battery includes:

[0019] The ratio of the following components to be used in a single application of spherical graphite powder, silicon source, surfactant I, conductive agent, deionized water, surfactant II, titanium source, and cerium source is 30-60g: 10-20g: 20-35g: 5-25g: 200-400mL: 25-75mL: 10-25g: 15-30g.

[0020] Based on the preparation method of lithium battery graphite anode material, it is prepared using the above-mentioned preparation process.

[0021] The beneficial effects of this invention are:

[0022] (1) Compared with the prior art, the present invention has simple operation, low cost, easy control of particle size of material airflow pulverization, easy to destroy the structure of the material itself, and makes the particle shaping more complete during the pulverization and spheroidization process. At the same time, the electrochemical performance and compaction density are higher than the level of the prior art.

[0023] (2) By modifying graphite, silicon and graphite are combined, and silicon atoms form chemical bonds with carbon atoms, which enhances the interlayer bonding force of graphite, improves the mechanical strength and wear resistance of the material, and the added cerium element can reduce the side reaction between the electrode and the electrolyte and suppress volume expansion. Titanium element can be used as a coating material for graphite to improve conductivity and structural stability.

[0024] (3) The present invention can improve the specific capacity and cycle stability of lithium-ion battery anode materials through silicon-titanium-graphite composite, while improving their wear resistance. Silicon-cerium-graphite composite can alleviate the volume expansion problem during lithium-ion insertion / extraction and improve conductivity. Titanium-cerium-graphite composite can synergistically improve the conductivity and cycle life of anode materials. The synergistic effect of silicon, titanium and cerium is achieved through multi-scale structural coupling and functional complementarity. Silicon, titanium and cerium can form a layered structure, which is embedded in the network graphite. The synergistic effect of the three improves the wear resistance and electrochemical performance of the material, as well as the cycle life in the battery.

[0025] (4) The present invention uses natural graphite to modify graphite after airflow pulverization, shaping and spheroidizing, which can increase the interaction between molecules. The silicon-titanium nanoparticles and graphene sheets are stacked in an interleaved manner, which can easily form a multiphase composite effect, reduce the orientation of graphite, modify the particle surface, increase the filling density between particles, and facilitate the secondary pulverization of the material to achieve the particle size distribution requirements of small particles, as well as secondary spheroidization, so that the spheroidization degree of the material is better. Attached Figure Description

[0026] Figure 1 The image shows a SEM image of the modified silicon-titanium-cerium-graphite composite material prepared in Example 1.

[0027] Figure 2 The image shows the SEM image of the unmodified graphite composite material prepared in Comparative Example 1. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] The lithium-ion battery graphite anode material in this embodiment includes the following raw materials in the indicated weight proportions:

[0031] The natural flake graphite has a particle size of 200 mesh and a carbon content of 96%. The ratio of primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water is 16g:6g:10g:3g:100mL. The ratio of surfactant II, titanium source and cerium source is 5mL:2g:3g.

[0032] This embodiment is based on a method for preparing natural graphite anode materials. The method adopts a secondary spheroidization method, uses natural graphite as the raw material, and modifies the treated graphite.

[0033] The method for preparing the graphite anode material for lithium batteries includes the following steps:

[0034] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0035] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0036] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0037] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0038] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0039] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0040] Step 5: Mix the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water evenly to obtain a conductive graphite mixture;

[0041] In step five, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0042] The amount of spherical graphite powder added at one time was 32g, the amount of tetraethyl silicate added was 12g, the amount of surfactant I added was 20g, the amount of conductive agent added was 6g, and the amount of deionized water added was 200mL; the mixing parameters were: stirring at room temperature for 3 hours.

[0043] Step 6: Add surfactant II, titanium source and cerium source to the conductive graphite mixture, stir evenly for 7 hours, dry the stirred mixture to evaporate the solvent, grind it into powder and pass it through a 100-mesh sieve, and sinter it. After sintering, the modified graphite anode material is obtained.

[0044] In step six, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridine chloride, and the cerium source is cerium nitrate.

[0045] The amount of surfactant II added was 25 mL, the amount of tetrabutyl titanate added was 10 g, and the amount of cerium nitrate added was 15 g;

[0046] The sintering temperature is 700℃, and the temperature is increased at a rate of 3℃ / min. The holding time is set to 1 hour for every 100℃ increase in temperature, and the total sintering time is 12h.

[0047] Step 7: Process the modified graphite anode material according to steps 1 to 3 above to obtain graphite anode material with target particle size modification. Add the modified graphite anode material to the spheroidizing machine, set the machine speed to 900 rpm, and run for 40 minutes. After the machine finishes running, the graphite anode material is obtained.

[0048] Example 2

[0049] The lithium-ion battery graphite anode material in this embodiment includes the following raw materials in the indicated weight proportions:

[0050] The natural flake graphite has a particle size of 200 mesh and a carbon content of 96%. The ratio of primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water is 15g:5g:9g:5g:100mL. The ratio of surfactant II, titanium source and cerium source is 50mL:17g:22g.

[0051] This embodiment is based on a method for preparing natural graphite anode materials. The method adopts a secondary spheroidization method, uses natural graphite as the raw material, and modifies the treated graphite.

[0052] The method for preparing the graphite anode material for lithium batteries includes the following steps:

[0053] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0054] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0055] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0056] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0057] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0058] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0059] Step 5: Mix the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water evenly to obtain a conductive graphite mixture;

[0060] In step five, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0061] The amount of spherical graphite powder added at one time was 45g, the amount of tetraethyl silicate added was 15g, the amount of surfactant I added was 27g, the amount of conductive agent added was 15g, and the amount of deionized water added was 300mL; the mixing parameters were: stirring at room temperature for 3 hours.

[0062] Step 6: Add surfactant II, titanium source and cerium source to the conductive graphite mixture, stir evenly for 7 hours, dry the stirred mixture to evaporate the solvent, grind it into powder and pass it through a 100-mesh sieve, and sinter it. After sintering, the modified graphite anode material is obtained.

[0063] In step six, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridine chloride, and the cerium source is cerium nitrate.

[0064] The amount of surfactant II added was 50 mL, the amount of tetrabutyl titanate added was 17 g, and the amount of cerium nitrate added was 22 g;

[0065] The sintering temperature is 700℃, and the temperature is increased at a rate of 3℃ / min. The holding time is set to 1 hour for every 100℃ increase in temperature, and the total sintering time is 12h.

[0066] Step 7: Process the modified graphite anode material according to steps 1 to 3 above to obtain graphite anode material with target particle size modification. Add the modified graphite anode material to the spheroidizing machine, set the machine speed to 900 rpm, and run for 40 minutes. After the machine finishes running, the graphite anode material is obtained.

[0067] Example 3

[0068] The lithium-ion battery graphite anode material in this embodiment includes the following raw materials in the indicated weight proportions:

[0069] The natural flake graphite has a particle size of 200 mesh and a carbon content of 96%. The ratio of primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water is 12g:4g:7g:5g:80mL. The ratio of surfactant II, titanium source and cerium source is 15mL:5g:6g.

[0070] This embodiment is based on a method for preparing natural graphite anode materials. The method adopts a secondary spheroidization method, uses natural graphite as the raw material, and modifies the treated graphite.

[0071] The method for preparing the graphite anode material for lithium batteries includes the following steps:

[0072] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0073] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0074] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0075] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0076] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0077] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0078] Step 5: Mix the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water evenly to obtain a conductive graphite mixture;

[0079] In step five, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0080] The addition amount of spherical graphite powder was 60g, tetraethyl silicate was 20g, surfactant I was 35g, conductive agent was 25g, and deionized water was 400mL; the mixing parameters were: stirring at room temperature for 3 hours.

[0081] Step 6: Add surfactant II, titanium source and cerium source to the conductive graphite mixture, stir evenly for 7 hours, dry the stirred mixture to evaporate the solvent, grind it into powder and pass it through a 100-mesh sieve, and sinter it. After sintering, the modified graphite anode material is obtained.

[0082] In step six, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridine chloride, and the cerium source is cerium nitrate.

[0083] The amount of surfactant II added was 75 mL, the amount of tetrabutyl titanate added was 25 g, and the amount of cerium nitrate was 30 g;

[0084] The sintering temperature is 700℃, and the temperature is increased at a rate of 3℃ / min. The holding time is set to 1 hour for every 100℃ increase in temperature, and the total sintering time is 12h.

[0085] Step 7: Process the modified graphite anode material according to steps 1 to 3 above to obtain graphite anode material with target particle size modification. Add the modified graphite anode material to the spheroidizing machine, set the machine speed to 900 rpm, and run for 40 minutes. After the machine finishes running, the graphite anode material is obtained.

[0086] Test case

[0087] SEM test

[0088] SEM images of the modified silicon-titanium-cerium-graphite composite material obtained in Example 1 are shown below. Figure 1 As shown, the material appears as nearly spherical particles with a smooth and rounded outer surface, similar to Comparative Example 1. Figure 2 Compared to the previous method, this indicates that the modified negative electrode material facilitates secondary spheroidization and has a uniform distribution of particle size.

[0089] Comparative Example 1

[0090] Comparative Example 1 uses unmodified graphite material and prepares a secondary spherical graphite anode material using the spheroidization process of Example 1. The specific steps of the preparation method of this lithium battery graphite anode material are as follows:

[0091] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0092] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0093] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0094] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0095] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0096] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0097] Step 5: Process the obtained primary spherical graphite anode material according to steps 1 to 3 above, and then add it to the spheroidization machine. Set the machine speed to 900 rpm and the running time to 40 minutes. After the machine finishes running, secondary spherical graphite anode material is obtained.

[0098] Comparative Example 2

[0099] Comparative Example 2 uses silicon-cerium modified graphite material and prepares a graphite anode material using the spheroidization process of Example 1. The specific steps of the preparation method of this lithium battery graphite anode material are as follows:

[0100] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0101] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0102] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0103] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0104] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0105] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0106] Step 5: Mix the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water evenly to obtain a conductive graphite mixture;

[0107] In step five, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0108] The amount of spherical graphite powder added at one time was 32g, the amount of tetraethyl silicate added was 12g, the amount of surfactant I added was 20g, the amount of conductive agent added was 6g, and the amount of deionized water added was 200mL; the mixing parameters were: stirring at room temperature for 3 hours.

[0109] Step 6: Add surfactant II and cerium source to the conductive graphite mixture, stir evenly for 7 hours, dry the stirred mixture to evaporate the solvent, grind it into powder, pass it through a 100-mesh sieve, and sinter it. After sintering, the modified graphite anode material is obtained.

[0110] In step six, the surfactant II is selected as hexadecylpyridine chloride, and the cerium source is cerium nitrate;

[0111] The amount of surfactant II added was 25 mL, and the amount of cerium nitrate was 15 g;

[0112] The sintering temperature is 700℃, and the temperature is increased at a rate of 3℃ / min. The holding time is set to 1 hour for every 100℃ increase in temperature, and the total sintering time is 12h.

[0113] Step 7: Process the modified graphite anode material according to steps 1 to 3 above to obtain graphite anode material with target particle size modification. Add the modified graphite anode material to the spheroidizing machine, set the machine speed to 900 rpm, and run for 40 minutes. After the machine finishes running, the graphite anode material is obtained.

[0114] Comparative Example 3

[0115] Comparative Example 3 uses silicon-titanium modified graphite material and prepares a graphite anode material by referring to the spheroidization process of Example 1. The specific steps of the preparation method of this lithium battery graphite anode material are as follows:

[0116] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0117] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0118] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0119] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0120] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0121] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0122] Step 5: Mix the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water evenly to obtain a conductive graphite mixture;

[0123] In step five, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0124] The amount of spherical graphite powder added at one time was 32g, the amount of tetraethyl silicate added was 12g, the amount of surfactant I added was 20g, the amount of conductive agent added was 6g, and the amount of deionized water added was 200mL; the mixing parameters were: stirring at room temperature for 3 hours.

[0125] Step 6: Add surfactant II and titanium source to the conductive graphite mixture, stir evenly for 7 hours, dry the stirred mixture to evaporate the solvent, grind it into powder, pass it through a 100-mesh sieve, and sinter it. After sintering, the modified graphite anode material is obtained.

[0126] In step six, the titanium source is tetrabutyl titanate, and the surfactant II is selected as hexadecylpyridine chloride.

[0127] The amount of surfactant II added was 25 mL, and the amount of tetrabutyl titanate added was 10 g;

[0128] The sintering temperature is 700℃, and the temperature is increased at a rate of 3℃ / min. The holding time is set to 1 hour for every 100℃ increase in temperature, and the total sintering time is 12h.

[0129] Step 7: Process the modified graphite anode material according to steps 1 to 3 above to obtain graphite anode material with target particle size modification. Add the modified graphite anode material to the spheroidizing machine, set the machine speed to 900 rpm, and run for 40 minutes. After the machine finishes running, the graphite anode material is obtained.

[0130] Comparative Example 4

[0131] Comparative Example 4 uses titanium-cerium modified graphite material and prepares a graphite anode material using the spheroidization process of Example 1. The specific steps of the preparation method of this lithium battery graphite anode material are as follows:

[0132] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0133] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0134] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0135] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0136] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0137] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0138] Step 5: Mix the primary spherical graphite powder, surfactant I, conductive agent, and deionized water until homogeneous to obtain a conductive graphite mixture;

[0139] In step five, surfactant I is heptadecafluorodecyltriethoxysilane, and conductive agent is graphene;

[0140] The amount of spherical graphite powder added at one time was 32g, surfactant I was 20g, conductive agent was 6g, and deionized water was 200mL; the mixing parameters were: stirring at room temperature for 3 hours.

[0141] Step 6: Add surfactant II, titanium source and cerium source to the conductive graphite mixture, stir evenly for 7 hours, dry the stirred mixture to evaporate the solvent, grind it into powder and pass it through a 100-mesh sieve, and sinter it. After sintering, the modified graphite anode material is obtained.

[0142] In step six, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridine chloride, and the cerium source is cerium nitrate.

[0143] The amount of surfactant II added was 25 mL, the amount of tetrabutyl titanate added was 10 g, and the amount of cerium nitrate added was 15 g;

[0144] The sintering temperature is 700℃, and the temperature is increased at a rate of 3℃ / min. The holding time is set to 1 hour for every 100℃ increase in temperature, and the total sintering time is 12h.

[0145] Step 7: Process the modified graphite anode material according to steps 1 to 3 above to obtain graphite anode material with target particle size modification. Add the modified graphite anode material to the spheroidizing machine, set the machine speed to 900 rpm, and run for 40 minutes. After the machine finishes running, the graphite anode material is obtained.

[0146] Comparative Example 5

[0147] Comparative Example 5 uses unmodified graphite material and prepares a primary spherical graphite anode material using the spheroidization process of Example 1. The specific steps of the preparation method of this lithium battery graphite anode material are as follows:

[0148] Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material conveying pipeline by an auger. It is then drawn into a rotary airflow pulverizer by a high-pressure blower. After being pulverized by the pulverizer, the material is further conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next airflow pulverizer by a high-pressure blower, and so on. After continuous pulverization by 10 pulverizers, graphite powder with a qualified particle size is obtained.

[0149] In step one, the pulverizer speed is set to 1000 rpm and the pressure of the high-pressure blower is 0.2 MPa; the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0150] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then conveyed to a classifier by a high-pressure blower. The classifier separates the qualified material and it falls into a hopper. The qualified material in the hopper is then drawn into the next small rotary airflow pulverizer by a high-pressure blower. This process is repeated for 6 small pulverizers to continuously shape the material and obtain the graphite powder product.

[0151] In step two, the crusher rotates at 2000 rpm, and the waste material obtained by the classifier during the separation process is collected by a dust collector.

[0152] Step 3: The graphite powder product is classified by a high-speed classifier to obtain graphite powder of the target particle size. The waste material is drawn into the dust collector by an induced draft fan.

[0153] Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the machine speed to 1000 rpm, and run for 60 minutes. After the machine finishes running, one batch of spheroidized graphite powder is obtained.

[0154] To verify the performance of the graphite anode material examples and comparative examples obtained in this invention, conventional indicators and electrochemical performance were tested, and the results are shown in the table below:

[0155]

[0156] Results and Discussion:

[0157] The results from the table show that: the unmodified graphite material in Comparative Example 1 has a smaller particle size compared to the modified graphite material in Comparative Example 2, which facilitates spheroidization; the 0.1C discharge capacity and initial efficiency are also improved, and the constant voltage time is shortened. Compared to the examples, the comparative examples show better performance in terms of D50, D90, powder compaction, 0.1C discharge capacity, initial efficiency, and constant voltage time, suggesting that the addition of modifying elements improves the performance of the graphite anode material. Compared to Example 1, Comparative Example 2, without the addition of titanium, has a larger particle size ratio, the particles are not refined, and the coating is uneven. Therefore, the electrical performance is relatively low. Compared with Example 1, Comparative Example 3 did not contain cerium and the particle size was also larger, presumably due to incomplete particle shaping, which reduced the particle contact area and resulted in low conductivity. Compared with Example 1, Comparative Example 4, although the titanium-cerium-graphite composite anode material improved the conductivity and structural stability of graphite, still had problems such as a ceiling on specific capacity and insufficient mechanical strength without the introduction of silicon. Among all Comparative Examples 1 and 5, natural graphite with secondary spheroidization was better than that with primary spheroidization. The process improvement achieved good results, and the processing and shaping of graphite powder was better, which was beneficial to the modification of composite materials. All modified secondary spheroidized graphite powders were better than all comparative examples.

[0158] The above description is merely a preferred embodiment of the present invention. It should be noted that modifications and supplements made by those skilled in the art to the specific embodiments described, without departing from the principle of the present invention, can also be considered as falling within the protection scope of the present invention.

Claims

1. A method for preparing a lithium battery graphite negative electrode material, characterized by, The method comprises the following steps: S1, the flaky graphite is crushed and classified for multiple times to obtain graphite powder with a target particle size; the graphite powder is then subjected to a first spheroidization treatment to obtain first spheroidized graphite powder; S2, the first spheroidized graphite powder, a silicon source, a surfactant I, a conductive agent and deionized water are stirred at room temperature for 2-5 hours; after stirring, a surfactant II, a titanium source and a cerium source are added, and stirring is performed for 6-8 hours; after drying and grinding, sintering is performed to obtain a modified graphite negative electrode material; S3, the modified graphite negative electrode material is subjected to a second spheroidization treatment to obtain a second spheroidized modified graphite negative electrode material; The amount ratio of the first spheroidized graphite powder, the silicon source, the surfactant I, the conductive agent and the deionized water is 30-60 g: 10-20 g: 20-35 g: 5-25 g: 200-400 mL; The amount ratio of the surfactant II, the titanium source and the cerium source is 25-75 mL: 10-25 g: 15-30 g.

2. The method of claim 1, wherein the lithium battery graphite anode material is prepared by the steps of: The flaky graphite is natural flaky graphite with a particle size of 32-500 mesh and a carbon content of more than 92%. ​ 3. The method of claim 1, wherein the lithium battery graphite anode material is prepared by the steps of: The crushing parameters are set as 800-1600 revolutions per minute, and the parameters of the first spheroidization treatment are set as a rotation speed of 800-1500 revolutions per minute and a running time of 15-80 minutes. ​ 4. The method of claim 1, wherein the lithium battery graphite anode material is prepared by the steps of: The silicon source is tetraethyl orthosilicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene. ​ 5. The method of claim 1, wherein the lithium battery graphite anode material is prepared by the steps of: The titanium source is tetrabutyl titanate, the surfactant II is cetylpyridinium chloride, and the cerium source is cerium nitrate. ​ 6. The method of claim 1, wherein the lithium battery graphite anode material is prepared by the steps of: The sintering temperature is 600-800 DEG C, and the total sintering time is 8-16 hours. ​ 7. The method of claim 1, wherein the lithium battery graphite anode material is prepared by the steps of: The rotation speed of the second spheroidization equipment is 600-1000 revolutions per minute, and the running time is 10-50 minutes. ​ 8. A lithium battery graphite anode material, characterized in that, The lithium battery graphite negative electrode material is prepared by the method of any one of claims 1-7, and the lithium battery graphite negative electrode material comprises: The amount ratio of the first spheroidized graphite powder, the silicon source, the surfactant I, the conductive agent, the deionized water, the surfactant II, the titanium source and the cerium source is 30-60 g: 10-20 g: 20-35 g: 5-25 g: 200-400 mL: 25-75 mL: 10-25 g: 15-30 g.

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