Lithium battery graphite negative electrode material and preparation method thereof

Abstract

The invention relates to the technical field of lithium battery negative electrode materials, in particular 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 a raw material, sucking the natural graphite into a jet mill through a high-pressure fan for crushing, shaping, spheroidizing, shaping and the like to obtain a pre-product graphite powder, modifying the graphite powder, and performing secondary crushing and spheroidizing; according to the graphite negative electrode material prepared through modification and secondary spheroidization, the mechanical strength and the wear resistance of the material are improved, secondary spheroidization is facilitated, the spheroidization degree of the material is good, volume expansion is inhibited, the conductivity and the structural stability can be improved, and the service life of the material is prolonged. The cycle service life in the battery is prolonged; and the electrochemical performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a lithium battery graphite negative electrode material and a preparation method thereof. Background Art

[0002] Natural graphite must be processed into spherical shapes before being used as a negative electrode material for lithium-ion batteries, rather than being crushed and used directly. This is mainly due to the working principle of lithium-ion batteries. Simply put, the working process of a lithium-ion battery is its charge and discharge process, which is the process of Li+ entering and exiting the spherical graphite. Because graphite has a lamellar structure and anisotropy, it makes it easier for Li+ to enter and exit the graphite layers. Processing graphite into spherical graphite means that Li+ is less restricted in direction when entering and exiting the graphite layers, thereby improving the performance of lithium-ion batteries.

[0003] There are many methods for processing carbon materials used as negative electrode materials for lithium-ion batteries. Natural graphite must be shaped and modified to improve battery performance. The main methods for processing natural graphite into negative electrode materials are spheroidization, surface oxidation, surface coating 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 structural stability of the material. Lithium-ion batteries primarily use graphite as a negative electrode material, but natural graphite negative electrode materials have problems such as low compaction density and poor rate performance, resulting in low energy density and power performance of lithium-ion batteries, as well as low high-current charge and discharge performance. Therefore, graphite modification and secondary spheroidization are necessary to improve battery performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a graphite negative electrode material for lithium batteries and a preparation method thereof, which solves the problems of volume expansion of the negative electrode material itself during lithium insertion, as well as electrochemical performance and structural stability.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a lithium battery graphite negative electrode material comprises the following steps: S1, subjecting flake graphite to multiple crushing and classification screening to obtain target particle size graphite powder; then subjecting the target particle size graphite powder to a spheroidization treatment to obtain a primary spheroidized graphite powder; S2, stirring the primary spheroidized graphite powder, silicon source, surfactant I, conductive agent and deionized water at room temperature for 2-5 hours, adding surfactant II, titanium source and cerium source after stirring, stirring for 6-8 hours, drying and grinding, and then sintering to obtain a modified graphite negative electrode material; S3. Performing secondary spheroidization on the modified graphite negative electrode material to obtain a secondary spheroidized modified graphite negative electrode material.

[0006] Furthermore, the flake graphite is natural flake graphite with a particle size of 32 meshes to 500 meshes and a carbon content of more than 92%.

[0007] Furthermore, the parameters of the crushing process are set at 800-1600 rpm, the parameters of the primary spheroidization process are set at a rotation speed of 800-1500 rpm, and the operation time is 15-80 minutes.

[0008] Furthermore, the dosage ratio of the primary spherical 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.

[0009] Furthermore, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

[0010] Furthermore, the usage ratio of surfactant II, titanium source and cerium source is 25-75 mL: 10-25 g: 15-30 g.

[0011] Furthermore, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridinium chloride, and the cerium source is cerium nitrate.

[0012] Furthermore, the sintering temperature is 600-800° C., and the total sintering time is 8-16 hours.

[0013] Furthermore, the secondary spheroidization equipment has a rotation speed of 600-1000 rpm and a running time of 10-50 minutes.

[0014] Furthermore, the lithium battery graphite negative electrode material includes: The dosage ratio of the primary 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.

[0015] The preparation method of the graphite negative electrode material for lithium batteries is made using the above-mentioned preparation process.

[0016] Beneficial effects of the present invention: (1) Compared with the existing technology, the present invention has simple process operation, low cost, easy control of the particle size of the material air flow crushing, not easy to destroy the structure of the material itself, and in the process of crushing and spheroidization, the particle shape is more complete, and the electrochemical performance and compaction density are higher than the existing technology level; (2) The present invention modifies graphite. After silicon is combined with graphite, silicon atoms and carbon atoms form chemical bonds, which enhances the bonding force between graphite layers and improves the mechanical strength and wear resistance of the material. The added cerium element can reduce the side reaction between the electrode and the electrolyte and inhibit volume expansion. Titanium can be used as a coating material for graphite to improve conductivity and structural stability.

[0017] (3) The present invention can improve the specific capacity and cycle stability of the negative electrode material of the lithium-ion battery through the silicon-titanium-graphite composite, while improving its wear resistance. The silicon-cerium-graphite composite can alleviate the volume expansion problem during the lithium ion insertion / extraction process and improve the conductivity. The titanium-cerium-graphite composite can synergistically improve the conductivity and cycle life of the negative electrode material. 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 and be embedded in the network of graphite. The mutual synergy of the three improves the wear resistance and electrochemical performance of the material, as well as the cycle life in the battery.

[0018] (4) The present invention uses natural graphite to be pulverized and shaped by air flow and then spheroidized to modify the graphite, which can increase the interaction between molecules. The silicon titanium nanoparticles and graphene sheets are staggered and stacked, which is easy to form a multi-phase composite effect, reduce the orientation of the graphite, modify the particle surface, and increase the filling density between particles. It is beneficial to the secondary pulverization of the material to achieve the particle size distribution requirements of small particles, as well as the secondary spheroidization, so that the material has a better spheroidization degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the SEM image of the modified silicon-titanium-cerium-graphite composite material prepared in Example 1.

[0020] Figure 2 This is the SEM image of the unmodified graphite composite material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Example 1 The graphite negative electrode material for lithium batteries in this embodiment includes the following raw materials in the following weight ratios: The particle size of natural flake graphite is 200 mesh and the carbon content is 96%. The usage ratio of primary spheroidized graphite powder, silicon source, surfactant I, conductive agent and deionized water is 16g:6g:10g:3g:100mL, and the usage ratio of surfactant II, titanium source and cerium source is 5mL:2g:3g.

[0023] This embodiment is based on a method for preparing a natural graphite negative electrode material, which adopts a secondary spheroidization method, uses natural graphite as the raw material, and modifies the treated graphite; The method for preparing a lithium battery graphite negative electrode material comprises the following steps: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0024] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by a dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment is finished running, the spheroidized graphite powder is obtained. Step 5: stirring and uniformly mixing the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water to obtain a conductive graphite mixture; In step 5, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene; The amount of spherical graphite powder added was 32 g, the amount of tetraethyl silicate added was 12 g, the amount of surfactant I added was 20 g, the amount of conductive agent added was 6 g, and the amount of deionized water added was 200 mL; the stirring parameters were: stirring at room temperature for 3 hours; Step 6: Adding surfactant II, titanium source and cerium source to the conductive graphite mixture, stirring evenly for 7 hours, drying the stirred mixture to evaporate the solvent, grinding it into powder, passing it through a 100-mesh sieve, and sintering it to obtain a modified graphite negative electrode material after sintering; In step 6, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridinium chloride, and the cerium source is cerium nitrate; 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; The sintering temperature was 700 °C, and the temperature was raised at a heating rate of 3 °C / min. The constant temperature time was set to 1 hour every time the temperature rose to 100 °C, and the total sintering time was 12 h. Step 7: The modified graphite negative electrode material is processed according to the above steps 1 to 3 to obtain a modified graphite negative electrode material with a target particle size, and the modified graphite negative electrode material is added to the spheroidizing integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the graphite negative electrode material is obtained.

[0025] Example 2 The graphite negative electrode material for lithium batteries in this embodiment includes the following raw materials in the following weight ratios: The particle size of natural flake graphite is 200 mesh and the carbon content is 96%. The usage ratio of primary spheroidized graphite powder, silicon source, surfactant I, conductive agent and deionized water is 15g:5g:9g:5g:100mL, and the usage ratio of surfactant II, titanium source and cerium source is 50mL:17g:22g.

[0026] This embodiment is based on a method for preparing a natural graphite negative electrode material, which adopts a secondary spheroidization method, uses natural graphite as the raw material, and modifies the treated graphite; The method for preparing a lithium battery graphite negative electrode material comprises the following steps: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0027] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by a dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment is finished running, the spheroidized graphite powder is obtained. Step 5: stirring and uniformly mixing the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water to obtain a conductive graphite mixture; In step 5, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene; The amount of spherical graphite powder added was 45 g, the amount of tetraethyl silicate added was 15 g, the amount of surfactant I added was 27 g, the amount of conductive agent added was 15 g, and the amount of deionized water added was 300 mL; the stirring parameters were: stirring at room temperature for 3 hours; Step 6: Adding surfactant II, titanium source and cerium source to the conductive graphite mixture, stirring evenly for 7 hours, drying the stirred mixture to evaporate the solvent, grinding it into powder, passing it through a 100-mesh sieve, and sintering it to obtain a modified graphite negative electrode material after sintering; In step 6, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridinium chloride, and the cerium source is cerium nitrate; 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; The sintering temperature was 700 °C, and the temperature was raised at a heating rate of 3 °C / min. The constant temperature time was set to 1 hour every time the temperature rose to 100 °C, and the total sintering time was 12 h. Step 7: The modified graphite negative electrode material is processed according to the above steps 1 to 3 to obtain a modified graphite negative electrode material with a target particle size, and the modified graphite negative electrode material is added to the spheroidizing integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the graphite negative electrode material is obtained.

[0028] Example 3 The graphite negative electrode material for lithium batteries in this embodiment includes the following raw materials in the following weight ratios: The particle size of natural flake graphite is 200 mesh and the carbon content is 96%. The dosage ratio of primary spheroidized graphite powder, silicon source, surfactant I, conductive agent and deionized water is 12g:4g:7g:5g:80mL, and the dosage ratio of surfactant II, titanium source and cerium source is 15mL:5g:6g.

[0029] This embodiment is based on a method for preparing a natural graphite negative electrode material, which adopts a secondary spheroidization method, uses natural graphite as the raw material, and modifies the treated graphite; The method for preparing a lithium battery graphite negative electrode material comprises the following steps: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0030] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by the dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment runs, the spheroidized graphite powder is obtained. Step 5: stirring and uniformly mixing the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water to obtain a conductive graphite mixture; In step 5, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene; The amount of spherical graphite powder added was 60 g, the amount of tetraethyl silicate added was 20 g, the amount of surfactant I added was 35 g, the amount of conductive agent added was 25 g, and the amount of deionized water added was 400 mL; the stirring parameters were: stirring at room temperature for 3 hours; Step 6: Adding surfactant II, titanium source and cerium source to the conductive graphite mixture, stirring evenly for 7 hours, drying the stirred mixture to evaporate the solvent, grinding it into powder, passing it through a 100-mesh sieve, and sintering it to obtain a modified graphite negative electrode material after sintering; In step 6, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridinium chloride, and the cerium source is cerium nitrate; The amount of surfactant II added was 75 mL, the amount of tetrabutyl titanate added was 25 g, and the amount of cerium nitrate added was 30 g; The sintering temperature was 700 °C, and the temperature was raised at a heating rate of 3 °C / min. The constant temperature time was set to 1 hour every time the temperature rose to 100 °C, and the total sintering time was 12 h. Step 7: The modified graphite negative electrode material is processed according to the above steps 1 to 3 to obtain a modified graphite negative electrode material with a target particle size, and the modified graphite negative electrode material is added to the spheroidizing integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the graphite negative electrode material is obtained.

[0031] Test example SEM testing The SEM image of the modified silicon-titanium-cerium-graphite composite material obtained in Example 1 is as follows: Figure 1 As shown, the material appears to be round particles with smooth and rounded outer surface, which is different from the comparative example 1 ( Figure 2 ), which shows that the modified negative electrode material is conducive to secondary spheroidization and the large and small particles are evenly distributed.

[0032] Comparative Example 1 Comparative Example 1 uses unmodified graphite material and refers to the spheroidization process of Example 1 to prepare a secondary spherical graphite negative electrode material. The specific steps of the preparation method of the lithium battery graphite negative electrode material are as follows: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0033] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by a dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment is finished running, the spheroidized graphite powder is obtained. Step 5: The obtained primary spheroidized graphite negative electrode material is processed according to the above steps 1 to 3, and then added to the spheroidization integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the secondary spheroidized graphite negative electrode material is obtained.

[0034] Comparative Example 2 Comparative Example 2 uses a silicon-cerium modified graphite material and refers to the spheroidization process of Example 1 to prepare a graphite negative electrode material. The specific steps of the preparation method of the lithium battery graphite negative electrode material are as follows: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0035] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by the dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment runs, the spheroidized graphite powder is obtained. Step 5: stirring and uniformly mixing the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water to obtain a conductive graphite mixture; In step 5, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene; The amount of spherical graphite powder added was 32 g, the amount of tetraethyl silicate added was 12 g, the amount of surfactant I added was 20 g, the amount of conductive agent added was 6 g, and the amount of deionized water added was 200 mL; the stirring parameters were: stirring at room temperature for 3 hours; Step 6: Adding surfactant II and cerium source to the conductive graphite mixture, stirring evenly for 7 hours, drying the stirred mixture to evaporate the solvent, grinding it into powder, passing it through a 100-mesh sieve, and sintering it to obtain a modified graphite negative electrode material after sintering; In step 6, the surfactant II is cetylpyridinium chloride, and the cerium source is cerium nitrate; The amount of surfactant II added was 25 mL, and the amount of cerium nitrate was 15 g; The sintering temperature was 700 °C, and the temperature was raised at a heating rate of 3 °C / min. The constant temperature time was set to 1 hour every time the temperature rose to 100 °C, and the total sintering time was 12 h. Step 7: The modified graphite negative electrode material is processed according to the above steps 1 to 3 to obtain a modified graphite negative electrode material with a target particle size, and the modified graphite negative electrode material is added to the spheroidizing integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the graphite negative electrode material is obtained.

[0036] Comparative Example 3 Comparative Example 3 uses silicon-titanium modified graphite material and refers to the spheroidization process of Example 1 to prepare a graphite negative electrode material. The specific steps of the preparation method of the lithium battery graphite negative electrode material are as follows: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0037] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by the dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment runs, the spheroidized graphite powder is obtained. Step 5: stirring and uniformly mixing the primary spherical graphite powder, silicon source, surfactant I, conductive agent and deionized water to obtain a conductive graphite mixture; In step 5, the silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene; The amount of spherical graphite powder added was 32 g, the amount of tetraethyl silicate added was 12 g, the amount of surfactant I added was 20 g, the amount of conductive agent added was 6 g, and the amount of deionized water added was 200 mL; the stirring parameters were: stirring at room temperature for 3 hours; Step 6: Adding surfactant II and titanium source to the conductive graphite mixture, stirring evenly for 7 hours, drying the stirred mixture to evaporate the solvent, grinding it into powder, passing it through a 100-mesh sieve, and sintering it to obtain a modified graphite negative electrode material after sintering; In step 6, the titanium source is tetrabutyl titanate, and the surfactant II is hexadecylpyridinium chloride; The amount of surfactant II added was 25 mL, and the amount of tetrabutyl titanate added was 10 g; The sintering temperature was 700 °C, and the temperature was raised at a heating rate of 3 °C / min. The constant temperature time was set to 1 hour every time the temperature rose to 100 °C, and the total sintering time was 12 h. Step 7: The modified graphite negative electrode material is processed according to the above steps 1 to 3 to obtain a modified graphite negative electrode material with a target particle size, and the modified graphite negative electrode material is added to the spheroidizing integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the graphite negative electrode material is obtained.

[0038] Comparative Example 4 Comparative Example 4 uses titanium-cerium modified graphite material and refers to the spheroidization process of Example 1 to prepare a graphite negative electrode material. The specific steps of the preparation method of the lithium battery graphite negative electrode material are as follows: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0039] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by a dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment is finished running, the spheroidized graphite powder is obtained. Step 5: Stirring and uniformly mixing the primary spherical graphite powder, surfactant I, conductive agent and deionized water to obtain a conductive graphite mixture; In step 5, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene; The amount of spherical graphite powder added was 32 g, the amount of surfactant I added was 20 g, the amount of conductive agent added was 6 g, and the amount of deionized water added was 200 mL; the stirring parameters were: stirring at room temperature for 3 hours; Step 6: Adding surfactant II, titanium source and cerium source to the conductive graphite mixture, stirring evenly for 7 hours, drying the stirred mixture to evaporate the solvent, grinding it into powder, passing it through a 100-mesh sieve, and sintering it to obtain a modified graphite negative electrode material after sintering; In step 6, the titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridinium chloride, and the cerium source is cerium nitrate; 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; The sintering temperature was 700 °C, and the temperature was raised at a heating rate of 3 °C / min. The constant temperature time was set to 1 hour every time the temperature rose to 100 °C, and the total sintering time was 12 h. Step 7: The modified graphite negative electrode material is processed according to the above steps 1 to 3 to obtain a modified graphite negative electrode material with a target particle size, and the modified graphite negative electrode material is added to the spheroidizing integrated machine, the equipment speed is set to 900 rpm, the running time is 40 minutes, and after the equipment operation is completed, the graphite negative electrode material is obtained.

[0040] Comparative Example 5 Comparative Example 5 uses unmodified graphite material and refers to the spheroidization process of Example 1 to prepare a primary spheroidized graphite negative electrode material. The specific steps of the preparation method of the lithium battery graphite negative electrode material are as follows: Step 1: Natural flake graphite with a particle size of 200 mesh and a carbon content of 96% is fed into the material transmission pipeline through an auger and sucked into the rotary airflow pulverizer through a high-pressure fan. After the material is crushed by the pulverizer, it continues to be conveyed to the classifier through a high-pressure fan. The classifier separates the qualified materials and drops them into the material box; the qualified materials in the material box are sucked into the next airflow pulverizer through a high-pressure fan, and so on. After continuous crushing by 10 pulverizers, graphite powder with qualified particle size is obtained; In step 1, the speed of the crusher is set to 1000 rpm, and the pressure of the high-pressure blower is 0.2 MPa; the waste materials obtained by the classifier during the separation process are collected by a dust collector.

[0041] Step 2: The qualified graphite powder is shaped in a small rotary airflow pulverizer and then transported to a classifier through a high-pressure blower. The classifier separates the qualified materials and drops them into a material box. The qualified materials in the material box are sucked into the next small rotary airflow pulverizer through high-pressure induced air. And so on. After being continuously shaped by 6 small pulverizers, the graphite powder product is obtained. In step 2, the pulverizer rotates at 2000 rpm, and the waste materials obtained during the separation process of the classifier are collected by the dust collector; Step 3: The graphite powder product is passed through the final high-speed classifier for product classification to obtain the target particle size graphite powder. The waste material will be sucked into the dust collector by induced air; Step 4: Add the target particle size graphite powder into the spheroidizing machine, set the equipment speed to 1000 rpm, and run for 60 minutes. After the equipment runs, a spheroidized graphite powder is obtained.

[0042] In order to verify the performance of the graphite negative electrode material examples and comparative examples obtained in the present invention, conventional indicators and electrochemical performance tests were performed on them. The results are shown in the table: Results and Discussion From the results of the data in the table, it can be concluded that the unmodified graphite material in Comparative Example 1 has a smaller particle size than the modified graphite material in Comparative Example 2, which is conducive to spheroidization, and the 0.1C discharge capacity and the first efficiency are also improved, shortening the constant voltage time; compared with the examples, the performance indicators of D50, D90, powder compaction, 0.1C discharge capacity, first efficiency and constant voltage time of the examples have all achieved good results. It is speculated that the performance of the graphite negative electrode material is improved after adding the modified element; in Comparative Example 2, compared with Example 1, no titanium element is added, the obtained particle size ratio is larger, the particles are not refined, and the coating is uneven. Therefore, the electrical performance is relatively low. In Comparative Example 3 compared with Example 1, no cerium element is added and the particle size is also larger. It is speculated that the particle shaping is incomplete, which reduces the contact area of ​​the particles and leads to low conductivity. In Comparative Example 4 compared with Example 1, although the titanium-cerium-graphite composite negative electrode material improves the conductivity and structural stability of graphite, it still has problems such as a ceiling on specific capacity and insufficient mechanical strength when silicon is not introduced. In all Comparative Examples 1 and 5, natural graphite is better after secondary spheroidization than primary spheroidization. The process improvement has achieved good results, and the processing and shaping of graphite powder is better, which is beneficial to the modification of the composite material. All modified secondary spheroidized graphite powders are better than all comparative examples.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art may modify and supplement the specific embodiments described, and make several variations and improvements without departing from the principles of the present invention, which should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a graphite negative electrode material for a lithium battery, characterized in that: The following steps are involved: S1, subjecting flake graphite to multiple crushing and classification screening to obtain target particle size graphite powder; then subjecting the target particle size graphite powder to a spheroidization treatment to obtain a primary spheroidized graphite powder; S2, stirring the primary spheroidized graphite powder, silicon source, surfactant I, conductive agent and deionized water at room temperature for 2-5 hours, adding surfactant II, titanium source and cerium source after stirring, stirring for 6-8 hours, drying and grinding, and then sintering to obtain a modified graphite negative electrode material; S3. Performing secondary spheroidization on the modified graphite negative electrode material to obtain a secondary spheroidized modified graphite negative electrode material.

2. The method for preparing a lithium battery graphite negative electrode material according to claim 1, characterized in that: The flake graphite is natural flake graphite with a particle size of 32-500 mesh and a carbon content of more than 92%.

3. The method for preparing a lithium battery graphite negative electrode material according to claim 1, characterized in that: The parameters of the crushing process are: 800-1600 rpm, the parameters of the primary spheroidization process are: speed 800-1500 rpm, and the running time is 15-80 minutes.

4. The method for preparing a lithium battery graphite negative electrode material according to claim 1, characterized in that: The dosage ratio of the primary spherical 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.

5. The method for preparing a lithium battery graphite negative electrode material according to claim 4, characterized in that: The silicon source is tetraethyl silicate, the surfactant I is heptadecafluorodecyltriethoxysilane, and the conductive agent is graphene.

6. The method for preparing a lithium battery graphite negative electrode material according to claim 1, characterized in that: The usage ratio of surfactant II, titanium source and cerium source is 25-75mL:10-25g:15-30g.

7. The method for preparing a lithium battery graphite negative electrode material according to claim 6, characterized in that: The titanium source is tetrabutyl titanate, the surfactant II is hexadecylpyridinium chloride, and the cerium source is cerium nitrate.

8. The method for preparing a lithium battery graphite negative electrode material according to claim 1, characterized in that: The sintering temperature is 600-800°C, and the total sintering time is 8-16 hours.

9. The method for preparing a lithium battery graphite negative electrode material according to claim 1, characterized in that: The secondary spheroidization equipment has a rotation speed of 600-1000 rpm and a running time of 10-50 minutes.

10. A lithium battery graphite negative electrode material, characterized in that: The lithium battery graphite negative electrode material is prepared according to the method according to any one of claims 1 to 9, and the lithium battery graphite negative electrode material comprises: The dosage ratio of the primary 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.

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