Modified artificial graphite negative material, preparation method thereof and lithium ion battery

Abstract

The application provides a modified artificial graphite negative material, a preparation method thereof and a lithium ion battery, and the preparation method comprises the following steps: mixing raw coke and an ammonium source modifier, calcining to obtain a carbonized precursor; mixing the obtained carbonized precursor with a binder, granulating, carbonizing and graphitizing to obtain the modified artificial graphite negative material. The modified artificial graphite negative material, the preparation method thereof and the lithium ion battery have high charge-discharge capacity, high initial coulomb efficiency and excellent cycle stability, and overcome the defects that the initial coulomb efficiency and fast charging capacity cannot be simultaneously improved in the prior art.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a modified artificial graphite anode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] With the sustainable development of the national economy and society, energy production and storage have become a crucial issue of global concern. Lithium-ion batteries, as a new type of energy conversion device, are developing rapidly in the energy storage field. The negative electrode material is a key component of lithium-ion batteries; its specific capacity and operating voltage directly affect the energy density of the battery and play a decisive role in its performance. Currently, artificial graphite is gradually becoming the preferred negative electrode material for lithium-ion batteries. Artificial graphite refers to graphite obtained from needle coke, pitch coke, and mesophase carbon microspheres through high-temperature graphitization. Generally speaking, negative electrode materials produced using needle coke as raw material have advantages such as high specific capacity, long cycle life, and high compaction density, as well as good processing performance, simple processes, and ease of industrialization.

[0003] Currently, there are limited methods on the market to improve the initial coulombic efficiency and fast-charging capability of artificial graphite anode materials. These methods generally involve isotropic selection of raw material coke, carbonization modification with different types of coating agents, and doping modification during the process. However, the carbon layer formed on the surface of the anode material by existing coating agents does not fully form a layered or stable structure, resulting in excessive side reactions at high / room temperatures, thus leading to low initial coulombic efficiency. While optimizing raw materials can improve fast-charging capability, its effect on improving high-rate fast charging is minimal. Moreover, considering the inherent characteristics of the material, when fast-charging capability is good, the material kinetics weaken. Currently, there are almost no methods that can simultaneously improve the initial coulombic efficiency of artificial graphite anode materials and significantly enhance fast-charging capability. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a modified artificial graphite anode material, its preparation method and lithium-ion battery. The anode material has high charge and discharge capacity, initial coulombic efficiency and excellent cycle stability, overcoming the defect in the prior art that it is impossible to simultaneously improve initial coulombic efficiency and fast charging capability.

[0005] The present invention proposes a method for preparing a modified artificial graphite anode material, comprising the following steps:

[0006] S1. The raw material coke is mixed with an ammonium source modifier and calcined to obtain a carbonized precursor;

[0007] S2. The carbonized precursor obtained in step S1 is mixed with a binder, granulated, carbonized, and graphitized to obtain the modified artificial graphite anode material.

[0008] In this invention, the surface of the raw coke is modified by an ammonium source modifier, and then the ammonium source modifier in the raw coke is vaporized by calcination, thereby forming more defects and nano-gap on the surface of the obtained carbonized precursor, improving the surface activity performance, which helps to improve the coating effect of the subsequent binder and form a dense layered coating layer after graphitization. Ultimately, this improves the charge-discharge capacity and first coulombic efficiency of the obtained modified artificial graphite anode material, while maintaining excellent cycle stability.

[0009] Preferably, in step S1, the raw material coke is at least one of needle coke, petroleum coke, pitch coke, spherical coke, sponge coke, or honeycomb coke, and the ammonium source modifier is at least one of ammonium chloride, ammonium bicarbonate, ammonium sulfate, ammonium acetate, or melamine.

[0010] Preferably, the mass ratio of the raw material coke to the ammonium source modifier is 1:0.1-0.3.

[0011] Preferably, in step S1, the calcination temperature is 400-500℃ and the time is 2-4h.

[0012] Preferably, in step S2, the binder includes asphalt; the asphalt is at least one of coal tar pitch, petroleum asphalt, coal tar, or natural asphalt.

[0013] Preferably, the mass ratio of the carbonized precursor to asphalt is 1:0.01-0.03.

[0014] Preferably, in step S2, the adhesive further includes an organic resin; the organic resin is a copolymer of polyethylene glycol maleate and acrylate;

[0015] Preferably, the mass ratio of the carbonized precursor to the organic resin is 1:0.05-0.1.

[0016] In this invention, an organic resin compounded with asphalt is used as a binder for coating. The organic resin is a copolymer of polyethylene glycol maleate and acrylate. The abundant carboxyl and hydroxyl groups contained therein can effectively bond and coat the carbonized precursor. After thermal decomposition, it can form a layered structure on the surface of the graphitized inner layer and contain multidimensional void channels. It can effectively and quickly transport to the innermost layer, reduce surface accumulation and the formation of lithium plating interface, and improve fast charging performance.

[0017] Preferably, in step S2, the granulation temperature is 400-650℃ and the granulation time is 4-8h;

[0018] Preferably, the particle size D50 of the granulated particles is 16-18 μm.

[0019] Preferably, in step S2, the carbonization temperature is 400-1000℃ and the time is 1-12h.

[0020] Preferably, in step S2, the graphitization temperature is 3000-3200℃ and the time is 7-30h.

[0021] The present invention also proposes a modified artificial graphite anode material prepared by the above preparation method.

[0022] The present invention also proposes a lithium-ion battery, which includes a negative electrode, wherein the negative electrode is composed of the above-mentioned modified artificial graphite negative electrode material.

[0023] The purpose of this application is to provide a modified artificial graphite anode material, its preparation method, and a lithium-ion battery. By modifying the raw material coke, more defects and nanopores are formed on the surface of the raw material coke, thereby improving the surface activity performance. Subsequently, in the coating process, the adhesion effect is further improved, making the resulting composite material easier to graphitize and enhancing the degree of graphitization. At the same time, multi-dimensional void channels can be formed on the surface of the graphitized inner layer. Finally, the modified artificial graphite anode material has more stable long cycle performance and higher rate performance. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the modified artificial graphite anode material obtained in Example 1. Detailed Implementation

[0025] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0026] Example 1

[0027] This embodiment proposes a modified artificial graphite anode material, the preparation method of which includes:

[0028] (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed by a crusher, and finely ground to obtain needle coke powder with an average particle size D50 of 10μm; the obtained needle coke powder and ammonium chloride were added to a batch mixer at a mass ratio of 1:0.2 and mixed evenly to obtain a premix; the obtained premix was calcined at 450℃ for 3h to obtain a carbonization precursor;

[0029] (2) The obtained carbonized precursor and coal tar pitch (softening point of 150℃, residual carbon value of 56%) were added to a batch mixer at a mass ratio of 1:0.02 and mixed evenly to obtain a mixture. The mixture was added to a vertical coating kettle for granulation. Under N2 protection, the temperature was raised to 300℃ at a heating rate of 1.5℃ / min and held for 0.5h. Then the temperature was raised to 400℃ at a heating rate of 0.5℃ / min and held for 1h. Then the temperature was raised to 550℃ at a heating rate of 3.0℃ / min and held for 6h. After cooling to room temperature, the mixture was sieved to obtain secondary particles with an average particle size D50 of 17μm.

[0030] (3) The obtained secondary particles are added to a carbonization furnace for carbonization. Under N2 protection, the temperature is raised to 900℃ at a carbonization heating rate of 10℃ / min and held for 4h. After shaping, carbonized particles with an average particle size D50 of 14μm are obtained. The obtained carbonized particles are graphitized at 3000℃ for 16h, cooled, demagnetized, and sieved to obtain the modified artificial graphite anode material.

[0031] Figure 1 Here is a scanning electron microscope (SEM) image of the modified artificial graphite anode material obtained in Example 1, with reference to... Figure 1 It can be seen that the modified artificial graphite anode material obtained in Example 1 has a uniform particle size distribution and no obvious large loosely bonded particle morphology. The material has good charge-discharge capacity, initial coulombic efficiency and cycle stability.

[0032] Example 2

[0033] This embodiment proposes a modified artificial graphite anode material, the preparation method of which includes:

[0034] (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed by a crusher, and finely ground to obtain needle coke powder with an average particle size D50 of 10μm; the obtained needle coke powder and ammonium chloride were added to a batch mixer at a mass ratio of 1:0.1 and mixed evenly to obtain a premix; the obtained premix was calcined at 400℃ for 4h to obtain a carbonization precursor;

[0035] (2) The obtained carbonized precursor and coal tar pitch (softening point of 150℃, residual carbon value of 56%) were added to a batch mixer at a mass ratio of 1:0.01 and mixed evenly to obtain a mixture. The mixture was added to a vertical coating kettle for granulation. Under N2 protection, the temperature was raised to 300℃ at a heating rate of 1.5℃ / min and held for 0.5h. Then the temperature was raised to 400℃ at a heating rate of 0.5℃ / min and held for 7h. After cooling to room temperature, the mixture was sieved to obtain secondary particles with an average particle size D50 of 18μm.

[0036] (3) The obtained secondary particles are added to a carbonization furnace for carbonization. Under N2 protection, the temperature is raised to 800℃ at a carbonization heating rate of 10℃ / min and held for 4h. After shaping, carbonized particles with an average particle size D50 of 16μm are obtained. The obtained carbonized particles are graphitized at 3000℃ for 16h, cooled, demagnetized, and sieved to obtain the modified artificial graphite anode material.

[0037] Example 3

[0038] This embodiment proposes a modified artificial graphite anode material, the preparation method of which includes:

[0039] (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed by a crusher, and finely ground to obtain needle coke powder with an average particle size D50 of 10μm; the obtained needle coke powder and ammonium chloride were added to a batch mixer at a mass ratio of 1:0.3 and mixed evenly to obtain a premix; the obtained premix was calcined at 500℃ for 2h to obtain a carbonization precursor;

[0040] (2) The obtained carbonized precursor and coal tar pitch (softening point of 150℃, residual carbon value of 56%) were added to a batch mixer at a mass ratio of 1:0.03 and mixed evenly to obtain a mixture. The mixture was added to a vertical coating kettle for granulation. Under N2 protection, the temperature was raised to 300℃ at a heating rate of 1.5℃ / min and held for 0.5h. Then the temperature was raised to 400℃ at a heating rate of 0.5℃ / min and held for 1h. Then the temperature was raised to 650℃ at a heating rate of 3.0℃ / min and held for 4h. After cooling to room temperature, the mixture was sieved to obtain secondary particles with an average particle size D50 of 16μm.

[0041] (3) The obtained secondary particles are added to a carbonization furnace for carbonization. Under N2 protection, the temperature is raised to 1000℃ at a carbonization heating rate of 10℃ / min and held for 4h. After shaping, carbonized particles with an average particle size D50 of 12μm are obtained. The obtained carbonized particles are graphitized at 3000℃ for 16h, cooled, demagnetized, and sieved to obtain the modified artificial graphite anode material.

[0042] Example 4

[0043] This embodiment proposes a modified artificial graphite anode material, the preparation method of which includes:

[0044] (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed by a crusher, and finely ground to obtain needle coke powder with an average particle size D50 of 10μm; the obtained needle coke powder and ammonium chloride were added to a batch mixer at a mass ratio of 1:0.2 and mixed evenly to obtain a premix; the obtained premix was calcined at 450℃ for 3h to obtain a carbonization precursor;

[0045] (2) The obtained carbonized precursor, coal tar pitch (softening point 150℃, carbon residue 56%), and copolymer of polyethylene glycol maleate and acrylate were added to a batch mixer at a mass ratio of 1:0.02:0.08 and mixed evenly to obtain a mixture. The obtained mixture was added to a vertical coating reactor for granulation. Under N2 protection, the temperature was raised to 300℃ at a heating rate of 1.5℃ / min and held for 0.5h. Then, the temperature was raised to 400℃ at a heating rate of 0.5℃ / min and held for 1h. Then, the temperature was raised to 550℃ at a heating rate of 3.0℃ / min and held for 6h. After cooling to room temperature, the mixture was sieved to obtain secondary particles with an average particle size D50 of 18μm.

[0046] The copolymer of polyethylene glycol maleic anhydride and acrylate is prepared by the following method: polyethylene glycol (Mw is 400) and maleic anhydride are added to cyclohexane at a mass ratio of 1:1, followed by the addition of 1% p-toluenesulfonic acid by mass of polyethylene glycol. The mixture is heated to 90°C and stirred for 1 hour. Then, methyl acrylate (twice the mass of polyethylene glycol) and azobisisobutyronitrile (5% by mass of polyethylene glycol) are added. The mixture is heated to 80°C and stirred for 2 hours. After the reaction is completed, cyclohexane is removed by vacuum distillation. The mixture is then washed with deionized water and cyclohexane in sequence to obtain the copolymer of polyethylene glycol maleic anhydride and acrylate.

[0047] (3) The obtained secondary particles are added to a carbonization furnace for carbonization. Under N2 protection, the temperature is raised to 900℃ at a carbonization heating rate of 10℃ / min and held for 4h. After shaping, carbonized particles with an average particle size D50 of 15μm are obtained. The obtained carbonized particles are graphitized at 3000℃ for 16h, cooled, demagnetized, and sieved to obtain the modified artificial graphite anode material.

[0048] Comparative Example 1

[0049] This comparative example presents a modified artificial graphite anode material, the preparation method of which includes:

[0050] (1) Needle coke (volatile matter ≤10.0%) was used as raw material, crushed by a crusher, and finely ground to obtain needle coke powder with an average particle size D50 of 10μm.

[0051] (2) The obtained needle-shaped coke powder and coal tar pitch (softening point of 150℃, carbon residue of 56%) were added to a batch mixer at a mass ratio of 1:0.02 and mixed evenly to obtain a mixture. The mixture was added to a vertical coating kettle for granulation. Under N2 protection, the temperature was raised to 300℃ at a heating rate of 1.5℃ / min and held for 0.5h. Then the temperature was raised to 400℃ at a heating rate of 0.5℃ / min and held for 1h. Then the temperature was raised to 550℃ at a heating rate of 3.0℃ / min and held for 6h. After cooling to room temperature, the mixture was sieved to obtain secondary particles with an average particle size D50 of 18μm.

[0052] (3) The obtained secondary particles are added to a carbonization furnace for carbonization. Under N2 protection, the temperature is raised to 900℃ at a carbonization heating rate of 10℃ / min and held for 4h. After shaping, carbonized particles with an average particle size D50 of 15μm are obtained. The obtained carbonized particles are graphitized at 3000℃ for 16h, cooled, demagnetized, and sieved to obtain the modified artificial graphite anode material.

[0053] The modified artificial graphite anode materials obtained in the examples and comparative examples were subjected to the performance tests shown in the following methods, and the results are shown in Table 1.

[0054] The modified artificial graphite anode materials obtained in the examples and comparative examples were mixed evenly according to the following ratio: modified artificial graphite anode material: conductive carbon black (SP): carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 95:1:1.5:2.5 (mass ratio). The mixture was then coated onto copper foil, and the coated electrode was dried in a vacuum drying oven at 120°C for 12 hours to obtain the anode sheet. The obtained anode sheet was then used for simulated battery assembly in a Braun glove box under argon protection. The electrolyte was 1 mol / L LiPF6, and the solvent was EC:DEC:DMC (volume ratio 1:1:1). The lithium metal sheet was used as the counter electrode.

[0055] The simulated battery was tested using the Land battery testing system. The battery was discharged at a constant current of 0.6 mA to 5 mV, allowed to stand for 10 minutes, then discharged again at a constant current of 0.05 mA to 5 mV, allowed to stand for 10 minutes, and then charged at a constant current of 0.6 mA to 2.0 V. The charge and discharge capacity during this process was recorded. After standing for 10 minutes, the battery was discharged at a constant current of 12 mA to 5 mV (recorded as the 2.0C discharge capacity), allowed to stand for 10 minutes, and then charged at a constant current of 0.6 mA to 2.0 V. After standing for 10 minutes, the battery was discharged at a constant current of 18 mA to 5 mV (recorded as the 3.0C discharge capacity), allowed to stand for 10 minutes, and then charged at a constant current of 0.6 mA to 2.0 V. The test results are listed in Table 1.

[0056] Table 1. Electrochemical test results of the modified artificial graphite anode materials obtained in the examples and comparative examples.

[0057]

[0058]

[0059] As shown in the table above, the modified artificial graphite anode material obtained in the embodiments of the present invention has higher charge-discharge capacity and first coulombic efficiency in lithium-ion batteries compared with the comparative example; and the discharge specific capacity of Examples 2.0C and 3.0C is superior to that of the comparative example, indicating that the anode material obtained in the embodiments improves the fast-charging performance of the material; at the same time, Example 4 has advantages over other embodiments in terms of charge-discharge capacity, first coulombic efficiency, and fast-charging performance.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing a modified artificial graphite negative electrode material, characterized by, Includes the following steps: S1. The raw material coke is mixed with an ammonium source modifier and calcined to obtain a carbonized precursor; S2. The carbonized precursor obtained in step S1 is mixed with a binder, granulated, carbonized, and graphitized to obtain the modified artificial graphite anode material. In step S1, the raw material coke is at least one of needle coke, petroleum coke or pitch coke, and the ammonium source modifier is at least one of ammonium chloride, ammonium bicarbonate, ammonium sulfate or ammonium acetate. In step S2, the binder includes asphalt; the asphalt is at least one of coal tar pitch, petroleum asphalt, or natural asphalt; the binder also includes an organic resin; the organic resin is a copolymer of polyethylene glycol maleate and acrylate. The mass ratio of the raw material coke to the ammonium source modifier is 1:0.1-0.3; in step S1, the calcination temperature is 400-500℃ and the time is 2-4h.

2. The method for preparing the modified artificial graphite anode material according to claim 1, characterized in that, The mass ratio of the carbonized precursor to asphalt is 1:0.01-0.

03.

3. The method for preparing the modified artificial graphite anode material according to claim 1, characterized in that, The mass ratio of the carbonized precursor to the organic resin is 1:0.05-0.

1.

4. The method for producing a modified artificial graphite negative electrode material according to any one of claims 1 to 3, characterized by, In step S2, the granulation temperature is 400-650℃ and the granulation time is 4-8h; The particle size D50 of the granulated particles is 16-18 μm.

5. The method for producing the modified artificial graphite negative electrode material according to any one of claims 1 to 3, characterized by, In step S2, the carbonization temperature is 400-1000℃ and the time is 1-12h.

6. The method for producing a modified artificial graphite negative electrode material according to any one of claims 1 to 3, characterized by, In step S2, the graphitization temperature is 3000-3200℃ and the time is 7-30h.

7. A modified artificial graphite anode material prepared by the preparation method according to any one of claims 1-6.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes a negative electrode, which includes the modified artificial graphite negative electrode material as described in claim 7.

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