Preparation method of graphite-based negative electrode material, graphite-based negative electrode material and application thereof

Abstract

The present invention discloses a preparation method of a graphite-based negative electrode material, a graphite-based negative electrode material, and its application. The preparation method of the graphite-based negative electrode material comprises the following steps: (1) preparing a modified liquid-phase coating agent: stirring the liquid-phase coating agent at 300° C. to 500° C., adding a conductive agent and a dispersant, and mixing to obtain a modified liquid-phase coating agent; (2) preparing a precursor: mixing a graphite-based aggregate and a modified liquid-phase coating agent to obtain a precursor; and (3) carbonizing the precursor: carbonizing the precursor and sieving it. In the preparation method of the present invention, the graphite-based aggregate and the modified liquid-phase coating agent are mixed to obtain a precursor, and then carbonizing the precursor to obtain a graphite-based material with a coating layer. The material has better rate and fast charging performance, lower electron transfer impedance, higher tap density, and lower specific surface area. The low specific surface area can improve the initial charge and discharge efficiency and reduce electrolyte loss. The preparation method does not require solvent recovery, drying, and other processes, can effectively reduce production costs, and has good commercial value.

Description

Technical Field

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

[0002] Lithium-ion batteries are one of the main energy storage devices, and negative electrode materials are the main component of lithium-ion batteries. Their performance and cost play a crucial role in lithium-ion batteries. The application of graphite materials as negative electrode materials in lithium-ion secondary batteries is of epoch-making significance. They have the advantages of low voltage, high safety, and low cost, and have a high lithium insertion capacity, with a theoretical lithium insertion capacity of up to 372mAh / g. However, as negative electrode materials, they also have significant shortcomings: First, their large specific surface area consumes more irreversible lithium and electrolyte during the charge and discharge process when reacting with the electrolyte and lithium salt to form the SEI film. Second, their low tap density leads to low initial coulombic efficiency and weakened cycling performance of lithium-ion batteries. To address this issue, technical processes can further reduce the specific surface area of ​​the negative electrode material and improve the material's reversible capacity and cycling performance.

[0003] The industry has also used coating agents such as asphalt to coat graphite materials to obtain modified graphite-based materials to improve the material's dynamic and cyclic performance. However, current coating methods either have poor coating effects or require the use of suspension, ultrasound, static pressure extrusion, etc. to improve the coating effect, making it difficult to achieve large-scale industrial application. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method for preparing a graphite-based negative electrode material, a graphite-based negative electrode material, and its application. The preparation method is simple to operate, requiring no solvent recovery or drying steps, and has good commercial value. The material exhibits excellent coating properties, and the resulting graphite-based negative electrode material exhibits low electron transfer resistance and high tap density. The low specific surface area improves initial charge and discharge efficiency and effectively reduces electrolyte loss.

[0005] To achieve the above object, the present invention provides a first aspect of a method for preparing a graphite-based negative electrode material, comprising the steps of:

[0006] (1) Preparation of modified liquid coating agent

[0007] The modified liquid coating agent is obtained by stirring the liquid coating agent at 300° C. to 500° C., and then adding a conductive agent and a dispersant and mixing.

[0008] (2) Preparation of precursor

[0009] A precursor is obtained by mixing a graphite-based aggregate and a modified liquid coating agent;

[0010] (3) Carbonization treatment

[0011] The precursor was carbonized and sieved.

[0012] In the preparation method of the present invention, a graphite-based aggregate and a modified liquid-phase coating agent are mixed to obtain a precursor, and then carbonized to obtain a graphite-based material coated with a coating layer, which has the following technical effects:

[0013] (1) The modified liquid phase coating agent is coated on the surface of the graphite-based aggregate, which can reduce the specific surface area of ​​the material while improving the isotropy of the material, so that the prepared graphite-based negative electrode material has better rate and fast charging performance.

[0014] (2) The liquid coating agent is subjected to a heat treatment at 300°C to 500°C, which can cause the light components in the liquid coating agent to evaporate or decompose. A conductive agent is then added to reduce the resistance of the coating layer. Adding a dispersant helps to improve the fluidity of the liquid coating agent during the processing to improve the coating effect. Therefore, the prepared graphite-based negative electrode material has a lower electron migration impedance and a higher tap density. The lower specific surface area can improve the initial charge and discharge efficiency and effectively reduce the electrolyte loss.

[0015] (3) The present invention disperses and coats the liquid-phase coating agent after heat treatment on the surface of the graphite-based aggregate through a dispersant, without the need for solvent recovery, drying and other processes. After carbonization, a low specific surface area graphite-based negative electrode material with a uniform coating layer can be obtained, which can effectively reduce the amount of liquid-phase coating agent added, reduce production costs, and has good commercial value.

[0016] In some embodiments, the liquid coating agent includes liquid asphalt or liquid resin.

[0017] In some embodiments, the viscosity of the liquid coating agent is 20 mPa·s to 5000 mPa·s.

[0018] In some embodiments, the conductive agent is at least one of graphene, carbon nanotubes, carbon black, and carbon fibers.

[0019] In some embodiments, the dispersant is at least one of a sulfonic acid dispersant, a sulfuric acid dispersant, and a carboxylate dispersant.

[0020] In some embodiments, the weight ratio of the liquid coating agent, the conductive agent, and the dispersant is 100:0.3-1:0.1-0.5.

[0021] In some embodiments, the stirring time in step (1) is 0.5 h to 3 h, and the mixing time is 0.1 h to 1 h.

[0022] In some embodiments, the weight ratio of the graphite-based aggregate to the modified liquid-phase coating agent is 100:5-15.

[0023] In some embodiments, the equipment used for mixing in step (2) is a VC high-speed mixer, a mechanical fusion machine, a horizontal mixer or a kneader.

[0024] In some embodiments, in step (2), the feeding rate of the graphite-based aggregate before the mixing is 1 kg / min to 7 kg / min, and the feeding rate of the modified liquid-phase coating agent before the mixing is 0.1 kg / min to 0.5 kg / min.

[0025] In some embodiments, the stirring speed of the equipment used for mixing in step (2) is 400 rpm to 3000 rpm, and the stirring time is 5 min to 20 min.

[0026] In some embodiments, the equipment used for carbonization in step (3) is a roller kiln, and the roller kiln adopts a static heat treatment method.

[0027] In some embodiments, the carbonization temperature in step (3) is 900° C. to 1400° C., and the carbonization time is 11 h to 15 h.

[0028] In some embodiments, the liquid coating agent is selected from at least one of petroleum asphalt, coal tar, phenolic resin, epoxy resin, aromatic petroleum resin, dicyclopentadiene petroleum resin, terpene resin, urea-formaldehyde resin, polyimide resin, furan resin and furfural resin.

[0029] In some embodiments, the graphite-based aggregate can be obtained by sequentially coarsely crushing, finely crushing, shaping, graphitizing, and then screening the graphite material.

[0030] In some embodiments, the particle size of the graphite material after the coarse grinding is 0.2 cm to 2 cm;

[0031] In some embodiments, the particle size of the graphite material after the fine grinding is 1 μm to 100 μm;

[0032] In some embodiments, the particle size of the graphite material after the shaping is 1 μm to 50 μm;

[0033] In some embodiments, the temperature of graphitization is 3000°C to 3500°C.

[0034] In some embodiments, the graphite material is selected from natural graphite or artificial graphite.

[0035] In some embodiments, the artificial graphite is selected from at least one of coal-based needle coke, petroleum-based needle coke, mesocarbon microbeads, and calcined petroleum coke.

[0036] To achieve the above objectives, the second aspect of the present invention provides a graphite-based anode material comprising a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The material exhibits low electron transfer resistance, high tap density, low specific surface area, and excellent initial charge and discharge efficiency, rate capability, and fast charge performance.

[0037] In some embodiments, Dv50 is 14.2 μm to 18.5 μm.

[0038] In some embodiments, the tap density is from 0.94 g / cm3 to 1.02 g / cm3. 3 .

[0039] In some embodiments, the specific surface area is 0.63 m 2 / g to 4.84m 2 / g.

[0040] In some embodiments, the tapped density is 1.95 g / cm 3 to 2.01g / cm 3 .

[0041] In some embodiments, the graphite-based aggregate has an ash content of ≤ 0.05 wt%.

[0042] In some embodiments, the graphite-based aggregate has a degree of graphitization of ≥ 90.0%.

[0043] In some embodiments, the carbonaceous coating comprises 0.1% to 5% by weight of the combined weight of the carbonaceous coating and the graphite-based aggregate.

[0044] The present invention also provides an application of the graphite-based negative electrode material in negative electrode materials. Using the graphite-based negative electrode material as a negative electrode active material can meet the requirements of batteries for energy storage devices. DETAILED DESCRIPTION

[0045] The graphite-based negative electrode material of the present invention can be used as a negative electrode active material in lithium-ion batteries, sodium-ion batteries, supercapacitors, and the like. It can be used alone or mixed with other negative electrode active materials (such as silicon-based negative electrode active materials, natural graphite, and artificial graphite). The graphite-based negative electrode material of the present invention inherently has excellent electrical conductivity, so the addition or absence of a conductive agent can be selected depending on the actual application.

[0046] The graphite-based negative electrode material of the present invention includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.1% to 5wt% of the sum of the weight of the carbonaceous coating layer and the graphite-based aggregate. As an example, the proportion of the carbonaceous coating layer to the sum of the weight of the carbonaceous coating layer and the graphite-based aggregate may be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5wt%. The graphite-based negative electrode material of the present invention has excellent physical properties, such as Dv50 of 14.2μm to 18.5μm and a tap density of 0.94g / cm3 to 1.02g / cm3. 3 , with a specific surface area of ​​0.63m 2 / g to 4.84m 2 / g, compacted density is 1.95g / cm 3 to 2.01g / cm 3 In the actual prepared graphite-based negative electrode materials, the physical properties thereof may be, but are not limited to, Dv50 of 14.2μm, 14.5μm, 14.8μm, 15.1μm, 15.5μm, 15.9μm, 16.3μm, 16.6μm, 17.0μm, 17.4μm, 17.7μm, 18.0μm, 18.5μm; and tap density of 0.94g / cm3, 0.95g / cm3, 0.96g / cm3, 0.97g / cm3, 0.98g / cm3, 0.99g / cm3, 1.0g / cm3, 1.01g / cm3, 1.02g / cm3 3 ;Specific surface area is 0.63m 2 / g, 0.86m 2 / g, 1.02m 2 / g, 1.23m 2 / g, 1.43m 2 / g, 1.65m 2 / g, 1.89m 2 / g, 2.34m 2 / g, 2.78m 2 / g, 2.97m 2 / g, 3.23m 2 / g, 3.61m 2 / g, 3.87m 2 / g, 4.01m 2 / g, 4.34m 2 / g, 4.58m 2 / g, 4.84m 2 / g; compacted density is 1.95g / cm 3 , 1.96g / cm 3 , 1.97g / cm 3 、1.98g / cm 3, 1.99g / cm 3 , 2.0g / cm 3 , 2.01g / cm 3 .

[0047] The method for preparing the graphite-based negative electrode material of the present invention comprises the steps of:

[0048] (1) Preparation of modified liquid coating agent

[0049] The modified liquid coating agent is obtained by stirring the liquid coating agent at 300° C. to 500° C., and then adding a conductive agent and a dispersant and mixing.

[0050] (2) Preparation of precursor

[0051] A precursor is obtained by mixing a graphite-based aggregate and a modified liquid coating agent;

[0052] (3) Carbonization treatment

[0053] The precursor was carbonized and sieved.

[0054] In step (1), the liquid coating agent comprises liquid asphalt or liquid resin. The liquid asphalt is petroleum asphalt or coal tar. The liquid resin is at least one of phenolic resin, epoxy resin, aromatic petroleum resin, dicyclopentadiene petroleum resin, terpene resin, urea-formaldehyde resin, polyimide resin, furan resin and furfural resin. The coating performance of the liquid coating agent can be improved by adding a conductive agent and a dispersant after the liquid coating agent is subjected to preliminary heat treatment, thereby obtaining a modified liquid coating agent.

[0055] The viscosity of the liquid coating agent is 20 mPa·s to 5000 mPa·s. The viscosity may be, but is not limited to, 20 mPa·s, 50 mPa·s, 100 mPa·s, 150 mPa·s, 200 mPa·s, 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 800 mPa·s, 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 4000 mPa·s, 4500 mPa·s, and 5000 mPa·s.

[0056] The conductive agent is at least one of graphene, carbon nanotubes, carbon black and carbon fibers, and the carbon black can be Ketjen black or acetylene black.

[0057] The dispersant is at least one of a sulfonic acid dispersant, a sulfuric acid dispersant, and a carboxylate dispersant. It is an anionic dispersant composed of an oleophilic hydrocarbon chain portion and a hydrophilic group, and the two groups are respectively located at the two ends of the molecule to form an asymmetric hydrophilic and lipophilic molecular structure. Sulfonic acid dispersants are usually R-SO3Na compounds, including but not limited to sodium dodecylsulfonate, sodium ligninsulfonate, or sodium dodecylbenzenesulfonate. Sulfuric acid dispersants are usually RO-SO3Na, including but not limited to sodium dodecyl sulfate or sodium ligninsulfate. Carboxylate dispersants include but are not limited to maleic acid-acrylic acid copolymer sodium salt, acrylic acid-acrylate-sulfonate terpolymer, and carboxylate-sulfonate-nonionic terpolymer. As an example, the dispersant is sodium ligninsulfonate or sodium ligninsulfate, which is more conducive to the mixing of the conductive agent and the liquid phase coating agent.

[0058] The weight ratio of the liquid coating agent, the conductive agent and the dispersant is 100:0.3 to 1:0.1 to 0.5. As an example, the weight ratio may be, but is not limited to, 100:0.3:0.1, 100:0.3:0.3, 100:0.3:0.0.5, 100:0.5:0.1, 100:0.5:0.4, 100:0.5:0.5, 100:0.8:0.1, 100:0.8:0.2, 100:0.8:0.4, 100:1:0.1, 100:1.0.2, 100:1:0.3, and 100:1:0.5.

[0059] The stirring time is 0.5h to 3h, and the mixing time is 0.1h to 1h. In actual operation, the stirring time may be, but not limited to, 0.5h, 0.8h, 1h, 1.2h, 1.5h, 1.8h, 2h, 2.4h, 2.8h, and 3h. The mixing time may be, but not limited to, 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, and 1h.

[0060] In step (2), the weight ratio of the graphite-based aggregate to the modified liquid-phase coating agent is 100:5 to 15. As an example, the weight ratio may be, but is not limited to, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14, and 100:15.

[0061] The graphite-based aggregate can be obtained by sequentially coarsely crushing, finely crushing, shaping, graphitizing and then screening the graphite material.

[0062] The graphite material is selected from natural graphite or artificial graphite, and the artificial graphite is selected from at least one of coal-based needle coke, petroleum-based needle coke, mesophase carbon microbeads and calcined petroleum coke.

[0063] The graphite material has a particle size of 0.2 cm to 2 cm, 1 μm to 100 μm, and 1 μm to 50 μm after coarse grinding, fine grinding, and shaping, respectively. Of course, in actual operation, the particle size after coarse grinding, fine grinding, and shaping can also be other parameters, as long as the particle size is reduced in sequence after treatment and ultimately meets the particle size requirements for use as a negative electrode active material. The graphitization temperature is 3000°C to 3500°C. As an example, the temperature may be, but is not limited to, 3000°C, 3100°C, 3200°C, 3300°C, 3400°C, and 3500°C. The graphitization degree of the graphite material is ≥90.0%. As an example, the graphitization degree is 90.0%, 90.5%, 91.0%, 91.5%, 92.0%, 93.0%, 94.0%, 94.5%, and 95.0%. The sieving is through a 325 mesh sieve. The ash content of the prepared graphite material is ≤0.05wt%. As an example, the ash content is 0.05wt%, 0.045wt%, 0.04wt%, 0.035wt%, 0.03wt%, 0.025wt%, and 0.02wt%.

[0064] The mixing equipment used is a VC high-speed mixer, a mechanical fusion machine, a horizontal mixer, or a kneader. The feeding rate of the graphite-based aggregate before mixing is 1 kg / min to 7 kg / min. As an example, the feeding rate of the graphite-based aggregate can be, but is not limited to, 1 kg / min, 2 kg / min, 3 kg / min, 4 kg / min, 5 kg / min, 6 kg / min, and 7 kg / min. The feeding rate of the modified liquid-phase coating agent before mixing is 0.1 kg / min to 0.5 kg / min. As an example, the feeding rate of the modified liquid-phase coating agent can be, but is not limited to, 0.1 kg / min, 0.2 kg / min, 0.3 kg / min, 0.4 kg / min, and 0.5 kg / min. The stirring speed of the mixing equipment is 400 rpm to 3000 rpm. As an example, the stirring speed may be, but is not limited to, 400 rpm, 500 rpm, 700 rpm, 900 rpm, 1000 rpm, 1200 rpm, 1500 rpm, 1800 rpm, 2000 rpm, 2400 rpm, 2700 rpm, and 3000 rpm. The stirring time is 5 min to 20 min. As an example, the stirring time may be, but is not limited to, 5 min, 7 min, 10 min, 13 min, 17 min, and 20 min.

[0065] In step (3), the carbonization equipment used is a roller kiln. The carbonization temperature is 900° C. to 1400° C., and as an example, the carbonization temperature may be, but is not limited to, 900° C., 950° C., 1000° C., 1050° C., 1100° C., 1150° C., 1200° C., 1250° C., 1300° C., 1350° C., and 1400° C. The carbonization time is 11 to 15 hours, and as an example, the carbonization time may be, but is not limited to, 11 hours, 12 hours, 13 hours, 14 hours, and 15 hours.

[0066] In order to better illustrate the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0067] Example 1

[0068] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0069] (1) Preparation of modified liquid coating agent

[0070] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then graphene and sodium dodecyl sulfate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium dodecyl sulfate was 100:0.3:0.1.

[0071] (2) Preparation of precursor

[0072] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0073] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0074] (3) Carbonization treatment

[0075] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0076] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.5 μm and a tap density of 0.97 g / cm 3 , with a specific surface area of ​​0.75m 2 / g, compacted density is 1.95g / cm 3 .

[0077] Example 2

[0078] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0079] (1) Preparation of modified liquid coating agent

[0080] Liquid phenolic resin (coking value > 10%, viscosity 1000 mPa·s) was stirred at 400°C for 2 hours, and then carbon nanotubes and sodium dodecyl sulfate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid phenolic resin, carbon nanotubes and sodium dodecyl sulfate was 100:0.8:0.5.

[0081] (2) Preparation of precursor

[0082] The petroleum needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% is coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh screen to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 16.3 μm and a tap density of 1.03 g / cm 3 , with a specific surface area of ​​0.91m 2 / g, compacted density is 1.88g / cm 3 , the ash content is 0.02wt%, and the degree of graphitization is 94.5%.

[0083] The VC high-speed mixer was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the VC high-speed mixer at a weight ratio of 100:12 at feeding rates of 1 kg / min and 0.1 kg / min, respectively. The speed was then increased to 3000 rpm, and the precursor was obtained after fusion for 5 minutes.

[0084] (3) Carbonization treatment

[0085] The precursor was carbonized in a roller kiln at 1400°C for 11 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0086] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.41% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 18.5 μm and a tap density of 0.98 g / cm 3 , with a specific surface area of ​​0.83m 2 / g, compacted density is 1.81g / cm 3 .

[0087] Example 3

[0088] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0089] (1) Preparation of modified liquid coating agent

[0090] A modified liquid coating agent was obtained by stirring liquid epoxy resin (coking value > 15%, viscosity 20 mPa·s) at 500°C for 0.5 h, adding graphene and sodium dodecyl sulfate and mixing for 0.5 h. The mass ratio of liquid epoxy resin, graphene and sodium dodecyl sulfate was 100:1:0.3.

[0091] (2) Preparation of precursor

[0092] Mesophase carbon microspheres with an ash content of less than 0.05% and a graphitization degree of more than 90.0% were coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 16.7 μm and a tap density of 1.19 g / cm 3 , with a specific surface area of ​​1.74m 2 / g, compacted density is 1.83g / cm 3 , the ash content is 0.01wt%, and the degree of graphitization is 93.8%.

[0093] The horizontal mixer was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:5 at a feeding rate of 3 kg / min and 0.2 kg / min, respectively. The speed was then increased to 1000 rpm, and the precursor was obtained after fusion for 6 minutes.

[0094] (3) Carbonization treatment

[0095] The precursor was carbonized in a roller kiln at 900°C for 15 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0096] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.11% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.2 μm and a tap density of 1.02 g / cm 3 , with a specific surface area of ​​0.63m 2 / g, compacted density is 1.96g / cm 3 .

[0097] Example 4

[0098] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0099] (1) Preparation of modified liquid coating agent

[0100] A modified liquid coating agent was obtained by stirring liquid epoxy resin (coking value > 15%, viscosity 5000 mPa·s) at 400°C for 2 hours, adding graphene and sodium dodecyl sulfate and mixing for 0.5 hours. The mass ratio of liquid epoxy resin, graphene and sodium dodecyl sulfate was 100:0.5:0.3.

[0101] (2) Preparation of precursor

[0102] Calcined petroleum coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% is coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000°C, and then passed through a 325-mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 16.2 μm and a tap density of 1.07 g / cm 3 , with a specific surface area of ​​0.98m 2 / g, compacted density is 1.81g / cm 3 , the ash content is 0.02wt%, and the degree of graphitization is 93.1%.

[0103] The kneader was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:5 at feeding rates of 7 kg / min and 0.5 kg / min, respectively. The speed was then increased to 400 rpm, and the precursor was obtained after fusion for 20 minutes.

[0104] (3) Carbonization treatment

[0105] The precursor was carbonized in a roller kiln at 1200°C for 12 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0106] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.49% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.9 μm and a tap density of 0.99 g / cm 3 , with a specific surface area of ​​0.69m 2 / g, compacted density is 1.96g / cm 3 .

[0107] Example 5

[0108] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0109] (1) Preparation of modified liquid coating agent

[0110] The modified liquid coating agent was obtained by stirring petroleum asphalt (viscosity 2000 mPa·s) at 300°C for 3 hours, adding graphene and sodium dodecyl sulfate and mixing for 0.5 hours. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium dodecyl sulfate was 100:0.3:0.1.

[0111] (2) Preparation of precursor

[0112] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0113] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0114] (3) Carbonization treatment

[0115] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0116] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.1 μm and a tap density of 0.91 g / cm 3 , with a specific surface area of ​​0.85m 2 / g, compacted density is 1.80g / cm 3 .

[0117] Example 6

[0118] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0119] (1) Preparation of modified liquid coating agent

[0120] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then graphene and sodium dodecyl sulfate were added and mixed for 1 hour to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium dodecyl sulfate was 100:0.3:0.1.

[0121] (2) Preparation of precursor

[0122] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 2 cm, finely crushed to a particle size of 150 μm, shaped to a particle size of 25 μm, graphitized at 3000 ° C, and then passed through a 325 mesh screen to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0123] The mechanical fusion machine was rotated at a low speed of 45 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at feeding rates of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0124] (3) Carbonization treatment

[0125] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0126] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.6 μm and a tap density of 0.88 g / cm 3 , with a specific surface area of ​​0.8m 2 / g, compacted density is 1.89g / cm 3 .

[0127] Example 7

[0128] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0129] (1) Preparation of modified liquid coating agent

[0130] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then graphene and sodium dodecyl sulfate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium dodecyl sulfate was 100:0.3:0.1.

[0131] (2) Preparation of precursor

[0132] The natural graphite with ash content below 0.05% and graphitization degree above 90.0% is coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, and shaped to a particle size of 20 μm to obtain a graphite-based aggregate. The Dv50 of the graphite-based aggregate is 14.6 μm and the tap density is 0.91 g / cm 3 , with a specific surface area of ​​7.55m 2 / g, compacted density is 1.95g / cm 3 , the ash content is 0.04wt%, and the degree of graphitization is 97.3%.

[0133] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0134] (3) Carbonization treatment

[0135] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0136] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.5 μm and a tap density of 0.97 g / cm 3 , with a specific surface area of ​​3.88m 2 / g, compacted density is 1.58g / cm 3 .

[0137] Example 8

[0138] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0139] (1) Preparation of modified liquid coating agent

[0140] A modified liquid coating agent was obtained by stirring liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) at 300°C for 3 hours, adding acetylene black and sodium dodecyl sulfate and mixing for 0.5 hours. The mass ratio of liquid urea-formaldehyde resin, acetylene black and sodium dodecyl sulfate was 100:0.3:0.1.

[0141] (2) Preparation of precursor

[0142] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0143] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0144] (3) Carbonization treatment

[0145] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0146] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.7 μm and a tap density of 0.95 g / cm 3 , with a specific surface area of ​​0.78m 2 / g, compacted density is 1.92g / cm 3 .

[0147] Example 9

[0148] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0149] (1) Preparation of modified liquid coating agent

[0150] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then carbon fiber and sodium dodecyl sulfate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, carbon fiber and sodium dodecyl sulfate was 100:0.3:0.1.

[0151] (2) Preparation of precursor

[0152] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0153] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0154] (3) Carbonization treatment

[0155] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0156] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.4 μm and a tap density of 0.96 g / cm 3 , with a specific surface area of ​​0.76m 2 / g, compacted density is 1.93g / cm 3 .

[0157] Example 10

[0158] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0159] (1) Preparation of modified liquid coating agent

[0160] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then graphene and sodium lignin sulfonate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium lignin sulfonate was 100:0.3:0.1.

[0161] (2) Preparation of precursor

[0162] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0163] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0164] (3) Carbonization treatment

[0165] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0166] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.6 μm and a tap density of 0.96 g / cm 3 , with a specific surface area of ​​0.68m 2 / g, compacted density is 1.94g / cm 3 .

[0167] Example 11

[0168] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0169] (1) Preparation of modified liquid coating agent

[0170] A modified liquid coating agent was obtained by stirring liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) at 300°C for 3 hours, adding graphene and sodium salt of maleic acid-acrylic acid copolymer and mixing for 0.5 hours. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium salt of maleic acid-acrylic acid copolymer was 100:0.3:0.1.

[0171] (2) Preparation of precursor

[0172] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0173] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0174] (3) Carbonization treatment

[0175] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0176] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.2 μm and a tap density of 0.96 g / cm 3 , with a specific surface area of ​​0.7m 2 / g, compacted density is 1.96g / cm 3 .

[0177] Comparative Example 1

[0178] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0179] (1) Preparation of precursor

[0180] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , the ash content is 0.02wt%, and the degree of graphitization is ≥96.0%.

[0181] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0182] (2) Carbonization treatment

[0183] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0184] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.2 μm and a tap density of 0.91 g / cm 3, with a specific surface area of ​​0.75m 2 / g, compacted density is 1.91g / cm 3 .

[0185] Comparative Example 2

[0186] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0187] (1) Preparation of modified liquid coating agent

[0188] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then graphene was added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin to graphene was 100:0.3.

[0189] (2) Preparation of precursor

[0190] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0191] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0192] (3) Carbonization treatment

[0193] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0194] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.4 μm and a tap density of 0.92 g / cm 3 , with a specific surface area of ​​0.76m 2 / g, compacted density is 1.92g / cm 3 .

[0195] Comparative Example 3

[0196] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0197] (1) Preparation of modified liquid coating agent

[0198] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 300°C for 3 hours, and then added with sodium dodecyl sulfate and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin to sodium dodecyl sulfate was 100:0.1.

[0199] (2) Preparation of precursor

[0200] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0201] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0202] (3) Carbonization treatment

[0203] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0204] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 16.4 μm and a tap density of 0.96 g / cm 3 , with a specific surface area of ​​0.69m 2 / g, compacted density is 1.96g / cm 3 .

[0205] Comparative Example 4

[0206] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0207] (1) Preparation of modified liquid coating agent

[0208] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 100°C for 3 hours, and then graphene and sodium dodecyl sulfate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium dodecyl sulfate was 100:0.3:0.1.

[0209] (2) Preparation of precursor

[0210] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0211] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0212] (3) Carbonization treatment

[0213] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0214] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.2 μm and a tap density of 0.93 g / cm 3 , with a specific surface area of ​​0.75m 2 / g, compacted density is 1.88g / cm 3 .

[0215] Comparative Example 5

[0216] The preparation method of the graphite-based negative electrode material of this embodiment includes:

[0217] (1) Preparation of modified liquid coating agent

[0218] Liquid urea-formaldehyde resin (coking value > 20%, viscosity 2000 mPa·s) was stirred at 700°C for 3 hours, and then graphene and sodium dodecyl sulfate were added and mixed for 0.5 hours to obtain a modified liquid coating agent. The mass ratio of liquid urea-formaldehyde resin, graphene and sodium dodecyl sulfate was 100:0.3:0.1.

[0219] (2) Preparation of precursor

[0220] The coal-based needle coke with an ash content of less than 0.05% and a graphitization degree of more than 90.0% was coarsely crushed to a particle size of 1 cm, finely crushed to a particle size of 50 μm, shaped to a particle size of 20 μm, graphitized at 3000 ° C, and then passed through a 325 mesh sieve to obtain a graphite-based aggregate. The graphite-based aggregate has a Dv50 of 13.9 μm and a tap density of 1.00 g / cm 3 , with a specific surface area of ​​1.01m 2 / g, compacted density is 2.01g / cm 3 , ash content is 0.02wt%, and graphitization degree is ≥96.0%.

[0221] The mechanical fusion machine was rotated at a low speed of 50 rpm, and the graphite-based aggregate and the modified liquid-phase coating agent were fed into the mechanical fusion machine at a weight ratio of 100:10 at a feeding rate of 4 kg / min and 0.32 kg / min, respectively. The speed was then increased to 900 rpm, and the precursor was obtained after fusion for 7 minutes.

[0222] (3) Carbonization treatment

[0223] The precursor was carbonized in a roller kiln at 1300°C for 13 hours. After the material was cooled, it was sieved through two layers of 200-mesh and three layers of 325-mesh sieves to obtain a graphite-based negative electrode material.

[0224] The resulting graphite-based negative electrode material includes a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate. The carbonaceous coating layer accounts for 0.32% of the weight of the graphite-based negative electrode material. The graphite-based negative electrode material has a Dv50 of 17.2 μm and a tap density of 0.92 g / cm 3 , with a specific surface area of ​​0.74m 2 / g, compacted density is 1.89g / cm 3 .

[0225] The graphite-based negative electrode materials obtained in Examples 1 to 11 and Comparative Examples 1 to 5 were used as the negative electrode active material and uniformly mixed with polyvinylidene fluoride and conductive carbon black, with the polyvinylidene fluoride accounting for 6% by weight of N-methylpyrrolidone and the conductive carbon black accounting for 2% by weight of N-methylpyrrolidone. The mixture was then coated on copper foil. The coated negative electrode sheet was then vacuum-dried in a vacuum drying oven at 110°C for 4 hours before use. Reference Group 1 also used the coal-based needle coke in Example 1 directly as the negative electrode active material, and Reference Group 2 used the natural graphite in Example 7 directly as the negative electrode active material.

[0226] The button cell was assembled in a nitrogen-filled Braun glove box in Germany. The electrolyte was 1MLiPF6+EC:DEC:DMC=1:1:1 (volume ratio). The metal lithium sheet was used as the counter electrode. The electrochemical performance test was carried out on a Wuhan Lantian CT2001A battery tester. The charge and discharge voltage range was 0.005V to 2.0V, and the charge and discharge rate was 0.1C. The first coulombic efficiency, 0.1C reversible capacity and electron transfer impedance were tested. The test results are shown in Table 1.

[0227] Table 1 Physical properties and electrochemical properties of graphite-based negative electrode materials obtained in each group of examples

[0228]

[0229]

[0230] It can be seen from the results in Table 1 that, compared with comparative examples 1 to 5 and reference groups 1 and 2, the preparation method of the graphite-based negative electrode material of Examples 1 to 11 of the present invention is to improve the coating effect by subjecting the liquid phase coating agent to a heat treatment at 300°C to 500°C, and then adding a conductive agent and a dispersant for modification and then coating, so that the prepared graphite-based negative electrode material has a lower electron transfer impedance, a higher tap density, a lower specific surface area, a higher first coulombic efficiency and a capacity.

[0231] Comparison of Examples 1, 10, and 11 shows that when the dispersant is sodium lignin sulfonate, the performance is better, which may be because sodium lignin sulfonate is more conducive to the mixing of the conductive agent and the liquid coating agent.

[0232] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a graphite-based negative electrode material, characterized in that: Including steps: (1) Preparation of modified liquid coating agent A modified liquid coating agent is obtained by stirring a liquid coating agent at 300° C. to 500° C., adding a conductive agent and a dispersant, and mixing. The viscosity of the liquid coating agent is 20 mPa·s to 5000 mPa·s, the dispersant is sodium lignin sulfonate, and the liquid coating agent includes liquid asphalt or liquid resin. (2) Preparation of precursor Mixing the graphite-based aggregate and the modified liquid-phase coating agent to obtain a precursor; (3) Carbonization treatment The precursor is carbonized and sieved.

2. The method for preparing a graphite-based negative electrode material according to claim 1, wherein: At least one of the following features (1) to (9): (1) The conductive agent is at least one of graphene, carbon nanotubes, carbon black and carbon fiber; (2) The weight ratio of the liquid coating agent, the conductive agent and the dispersant is 100:0.3-1:0.1-0.5; (3) The stirring time in step (1) is 0.5 h to 3 h, and the mixing time is 0.1 h to 1 h; (4) The weight ratio of the graphite-based aggregate to the modified liquid-phase coating agent is 100:5-15; (5) The mixing equipment used in step (2) is a VC high-speed mixer, a mechanical fusion machine or a kneading machine; (6) The feeding rate of the graphite-based aggregate in step (2) before the mixing is 1 kg / min to 7 kg / min, and the feeding rate of the modified liquid-phase coating agent before the mixing is 0.1 kg / min to 0.5 kg / min; (7) The stirring speed of the equipment used for mixing in step (2) is 400 rpm to 3000 rpm, and the stirring time is 5 min to 20 min; (8) The equipment used for carbonization in step (3) is a roller kiln; (9) The carbonization temperature in step (3) is 900° C. to 1400° C., and the carbonization time is 11 h to 15 h.

3. The method for preparing a graphite-based negative electrode material according to claim 1, wherein: The liquid coating agent is selected from at least one of petroleum asphalt, coal asphalt, phenolic resin, epoxy resin, aromatic petroleum resin, dicyclopentadiene petroleum resin, terpene resin, urea-formaldehyde resin, polyimide resin, furan resin and furfural resin.

4. The method for preparing a graphite-based negative electrode material according to claim 1, wherein: The graphite-based aggregate can be obtained by sequentially coarsely crushing, finely crushing, shaping, graphitizing and then screening the graphite material.

5. The method for preparing a graphite-based negative electrode material according to claim 4, wherein: At least one of the following features (1) to (4): (1) The particle size of the graphite material after the coarse pulverization is 0.2 cm to 2 cm; (2) The particle size of the graphite material after the fine grinding is 1 μm to 100 μm; (3) The particle size of the graphite material after the shaping is 1 μm to 50 μm; (4) The graphitization temperature is 3000°C to 3500°C.

6. The method for preparing a graphite-based negative electrode material according to claim 4, wherein: The graphite material is selected from natural graphite or artificial graphite.

7. The method for preparing a graphite-based negative electrode material according to claim 6, wherein: The artificial graphite is selected from at least one of coal-based needle coke, petroleum-based needle coke, mesocarbon microbeads and calcined petroleum coke.

8. The graphite-based negative electrode material prepared by the method for preparing a graphite-based negative electrode material according to any one of claims 1 to 7, characterized in that: The invention comprises a graphite-based aggregate and a carbonaceous coating layer coated on the surface of the graphite-based aggregate.

9. The graphite-based negative electrode material according to claim 8, characterized in that At least one of the following features (1) to (7): (1) Dv50 is 14.2 μm to 18.5 μm; (2) Tap density is 0.94g / cm 3 to 1.02g / cm 3 ; (3) Specific surface area is 0.63m 2 / g to 4.84m 2 / g; (4) The compacted density is 1.95g / cm 3 to 2.01g / cm 3 ; (5) The ash content of the graphite-based aggregate is ≤0.05wt.%; (6) The graphitization degree of the graphite-based aggregate is ≥90.0%; (7) The carbonaceous coating layer accounts for 0.1% to 5.0% of the total weight of the carbonaceous coating layer and the graphite-based aggregate.

10. Use of the graphite-based negative electrode material prepared by the method for preparing a graphite-based negative electrode material according to any one of claims 1 to 7 or the graphite-based negative electrode material according to any one of claims 8 to 9 in negative electrode materials.

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