Anode materials, batteries

Abstract

The present application provides a negative electrode material, a battery, that includes artificial graphite having internal and / or surface pores. The negative electrode material has a pore volume of Vcm 3 / kg, specific surface area is Sm 2 / g and tap density is Tg / mL, then 8.5≦V×S / T≦27. The negative electrode material and the battery provided by the present application can improve the electrochemical performance of the negative electrode material while ensuring the processing performance of the material.

Description

[Technical Field]

[0001] This application relates to the technical field of anode materials, and more particularly to anode materials, batteries. [Background technology]

[0002] Currently, graphite has become the mainstream negative electrode material for commercial lithium-ion batteries due to its advantages such as high electrical conductivity, a large lithium ion diffusion coefficient, a layered structure with a small volume change before and after lithium absorption, a high lithium absorption capacity, and a low lithium absorption potential.

[0003] Conventional graphitization equipment for graphite anodes is mainly divided into two types: crucible furnaces and box furnaces. Both are batch-type furnaces, and the graphitization process requires power outages, making continuous production impossible. Furthermore, the heating and cooling processes of the equipment are particularly limited, and the heating and cooling rates are slow, resulting in long production cycles. Generally, the graphitization cycle is within 15 to 45 days. During the graphitization production process, volatile components and impurity elements in the raw materials are released under high-temperature conditions, forming pores inside and / or on the surface of the graphite. Generally, artificial graphite has a certain number of pore structures, and the presence of pores is due to the Li + increases the diffusion channels inside the graphite material, + This reduces the diffusion resistance of the graphite, thereby effectively improving the rate performance of the material. In fact, simply improving the pore structure alone does not result in optimal rate performance, and there is still significant room for improvement. Researchers have only studied the effect of a single factor on the performance of graphite materials, and have not delved into the synergistic effects between multiple factors to maximize the improvement of graphite's rate performance.

[0004] Therefore, at the current stage where graphite materials are already mature, improving a single parameter alone cannot meet the market demand for low-cost, high-performance graphite materials. It is necessary to research the synergistic action mechanism of various factors and develop graphite anode materials that meet market demand. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of this, the present application provides an anode material and a battery that can improve the rate characteristics and capacity of the anode material while improving the processing performance of the material. [Means for solving the problem]

[0006] According to a first aspect, the present application provides a negative electrode material, the negative electrode material comprising artificial graphite, the artificial graphite having an internal and / or surface pore structure, and the negative electrode material having a pore volume of Vcm 3 / kg, and the specific surface area is Sm 2 / g and tap density is Tg / mL, 8.5≦V×S / T≦27, The pore volume was measured using an ASAP 2460 device manufactured by Micromeritics, Inc., USA, and calculated within the pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0007] In some embodiments, the negative electrode material has a pore volume of Vcm 3 / kg, 5.0≦V≦8.0.

[0008] In some embodiments, the negative electrode material has a specific surface area of ​​Sm 2 / g, 1.78≦S≦3.00.

[0009] In some embodiments, the negative electrode material has a tap density, Tg / mL, of 0.734≦T≦1.160.

[0010] In some embodiments, the pores comprise at least one of micropores and mesopores.

[0011] In some embodiments, the pores have an average pore diameter of 50 Å to 200 Å.

[0012] In some embodiments, the negative electrode material has a lattice spacing of d 002 When the 002 ≦3.364 Å.

[0013] In some embodiments, the particle size D of the negative electrode material 50 is 10 μm to 30 μm.

[0014] In some embodiments, the negative electrode material includes primary particles of artificial graphite and / or secondary particles of artificial graphite.

[0015] In some embodiments, the negative electrode material further comprises amorphous carbon.

[0016] In some embodiments, the negative electrode material further includes amorphous carbon, and the mass percentage of the amorphous carbon in the negative electrode material is 0.1 wt % to 5 wt %.

[0017] According to a second aspect, the present application provides a battery comprising the negative electrode material according to the first aspect. [Effects of the Invention]

[0018] The technical solution of the present application has at least the following beneficial effects: The negative electrode material provided by the present application includes artificial graphite having pores inside and / or on the surface thereof, and the pore volume of the negative electrode material is Vcm 3 / kg, and the specific surface area is Sm 2 / g and tap density Tg / mL, V×S / T is 8.5≦V×S / T≦27. Generally, a certain range of pore volume in artificial graphite can increase the diffusion channels for lithium ions, reduce the diffusion resistance of lithium ions, and effectively improve the rate performance of the material. A certain range of specific surface area ensures sufficient electrochemical reaction interfaces, promotes lithium ion diffusion at solid-liquid interfaces and within the solid phase, reduces concentration polarization, and is beneficial for improving the capacity and rate performance of anode materials. Through extensive research, the applicant has found that the migration rate of lithium ions is not only related to the migration space (i.e., the pore volume size) and the reaction interface size, but also to the friction conditions on the artificial graphite surface. Therefore, even if the pore volume and specific surface area are sufficient, it does not necessarily guarantee complete absorption and desorption of lithium ions, and the friction conditions can directly affect the tap density. By limiting V×S / T to this range, it is possible to ensure that lithium ions are absorbed and released more smoothly inside the artificial graphite material particles at the appropriate spatial and reaction interfaces, thereby significantly improving the rate and capacity of the material.

[0019] The anode material provided by the present application is produced and processed using a continuous graphitization process, in which all materials are continuously charged and discharged, and the time and temperature at which all materials pass through the high-temperature zone are synchronized. The graphitization process controls the temperature rise and fall rates to uniformly and quickly release volatile components, impurity elements, and other substances contained in the material, thereby achieving precise control of the internal and / or surface pore volume of the graphite, and thus control of the pore volume and specific surface area of ​​the material. The synergistic use of the above process methods overcomes the problems of conventional graphitization furnaces, such as uneven heating of the material due to temperature gradients at different locations, and the large and uncontrollable variations in indicators such as the specific surface area, pore volume, and tap density of the processed product, thereby enabling the pore volume, specific surface area, and tap density of the processed material to meet ideal control design requirements.

[0020] The negative electrode material provided by the present application has low energy consumption per unit mass, has obvious advantages in cost and production cycle, and is environmentally friendly. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a scanning electron microscope photograph of the negative electrode material provided in Example 10 of the present application. [Figure 2] FIG. 2 is a magnified view of a scanning electron microscope photograph of the negative electrode material provided in Example 10 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to better explain the present application and facilitate understanding of the technical solution of the present application, the present application will be described in more detail below. However, the following examples are merely simplified examples of the present application, and do not indicate or limit the scope of protection of the present application, which is governed by the claims.

[0023] In the field of anode materials, the development of continuous graphitization equipment has continued for decades, with patent US06619591 disclosing an apparatus capable of continuous graphitization of carbon-containing materials as early as 1987. In recent years, applicants have also continued to develop continuous graphitization equipment. For example, patent CN211425033U, filed in 2019, discloses a vertical, continuous kiln for producing anode materials for lithium batteries, with continuous discharge from an outlet and continuous loading through a material pipe. Compared to conventional processes, continuous graphitization processes shorten the graphitization time from days to hours, significantly reducing energy consumption. However, the significant reduction in graphitization time also results in changes to the microstructure of the artificial graphite, particularly changes to the internal pore structure and crystalline form of the artificial graphite, compared to conventional artificial graphite. It has been proven in the industry that such modifications make it difficult to satisfy the performance requirements of artificial graphite and are difficult to improve. Therefore, even though continuous graphitization equipment has existed for 30 to 40 years, there has been no precedent for successful mass production of continuously graphitized artificial graphite anode products.

[0024] In recent years, with the increasing energy scarcity, in order to further reduce the cost of artificial graphite, the applicant has continued to develop the application of continuous graphitization equipment to develop artificial graphite anode materials with performance equivalent to or even better than current conventional graphitized anode materials, with the goal of reducing the energy consumption of artificial graphite anode materials and further reducing costs. The applicant has developed a large-scale preparation process, devised various means to improve the rapid temperature fluctuations that cause adverse changes in artificial graphite products, and selected the products to obtain a series of different types of artificial graphite anode materials. Although these artificial graphite anode materials differ from conventional artificial graphite products in microstructure, their electrical performance can be basically equivalent to that of conventional artificial graphite products, and in some respects, their electrical performance and processing performance are superior or more stable, making them eligible to replace conventional artificial graphite products.

[0025] The preparation process and related products will be described in more detail below, taking as an example the preparation process developed by the applicant.

[0026] A method for producing a negative electrode material, Step S10: shaping the raw coke to obtain coke powder; Step S20: pressing a mixture containing coke powder, a binder, and a solvent at a pressure of 5 MPa to 100 MPa to obtain a precursor, where the coke powder, the binder, and the solvent have a mass ratio of 100:(3-20):(5-50); Step S30: subjecting the precursor in S20 to a carbonization treatment at a temperature of 1000°C to 1500°C for 2 hours to 6 hours, and then cooling the precursor to obtain a carbonized product; The precursor is placed in a continuous graphitization furnace and graphitized to obtain a negative electrode material. The specific graphitization method involves heating the precursor to 2800-3200°C at a heating rate of 12-25°C / min, maintaining the temperature at 2800-3200°C for 2-5 hours, and then cooling the precursor to 30°C at a heating rate of 22-26°C / min, including step S40 of controlling the ratio of the heating rate for the graphitization process to the heating rate for the carbonization process to 4-8.

[0027] The method for producing a negative electrode material provided by the present application involves pressing a mixture of coke powder, binder, and solvent, carbonizing the pressed product under certain temperature conditions, and then directly placing the carbonized product in a continuous graphitization furnace. The temperature is then rapidly increased, allowing the precursor to reach the graphitization temperature in a relatively short period of time, resulting in the volatilization and escape of impurity atoms, and the formation of pores inside and / or on the surface of the graphite particles. Furthermore, the process of loading and unloading materials into and from the continuous graphitization furnace can be completed within a few hours. This continuous operation allows the materials to be continuously loaded and unloaded, eliminating power outages during this period and minimizing the temperature gradient at different positions within the furnace. This improves the uniformity of graphitization of the negative electrode material, while also improving the thermal energy utilization rate of the continuous graphitization furnace and reducing production costs.

[0028] In some embodiments, the green coke comprises at least one of petroleum coke, needle coke, pitch coke, and isotropic coke.

[0029] In some embodiments, the shaping comprises at least one of milling, spheronizing, or classification, and the shaping process is advantageous for improving particle morphology and increasing tap density.

[0030] The median diameter of the coke powder obtained by shaping is 10 μm to 20 μm, and more specifically, may be 10 μm, 11.5 μm, 12 μm, 13 μm, 15 μm, 17 μm, 18 μm, 18.5 μm, 19 μm, or 20 μm, but is not limited to the listed numerical values, and other unlisted numerical values ​​within the numerical range also apply. Controlling the median diameter of the coke powder within the above range through multiple tests is advantageous for achieving both processability, capacity, and rate characteristics.

[0031] In some embodiments, the mass content of carbon in the coke powder is 80% or more, and may be specifically 80%, 81%, 82%, 85%, 90%, 95%, or 96%, but is not limited to the recited values, and other unrecited values ​​within the range also apply.

[0032] In some embodiments, the solvent comprises at least one of water, ethanol, acetone, benzene, toluene, quinoline, tetrahydrofuran, and carbon tetrachloride.

[0033] In some embodiments, the binder includes at least one of heavy oil, mineral oil, coal tar, ethylene tar, pitch, petroleum resin, phenolic resin, epoxy resin, coumarone resin, potato starch, wheat starch, corn starch, sweet potato starch, arrowroot flour, and tapioca flour. The pitch may include at least one of petroleum-based liquid pitch and coal-based liquid pitch. Specifically, the petroleum-based liquid pitch may be petroleum pitch, modified pitch, mesophase pitch, etc.

[0034] In some embodiments, the mass ratio of coke powder, binder, and solvent is 100:(3-20):(5-50), and specifically may be 100:3:5, 100:10:15, 100:15:20, 100:20:20, 100:20:15, 100:10:10, or 100:15:25, but is not limited to the recited values, and other unrecited values ​​within the numerical range also apply.

[0035] As can be seen, in the examples, when the binder ratio is low (the mass ratio of binder to coke powder is 3 to 10:100), the obtained artificial graphite is mainly composed of primary particles, and in the examples, when the binder ratio is high (the mass ratio of binder to coke powder is 10 to 20:100), the obtained artificial graphite is mainly composed of secondary particles.

[0036] In some embodiments, the mixing method of the mixture includes at least one of mechanical stirring and ultrasonic dispersion. When mechanical stirring is used for mixing, a propeller stirrer, a turbine stirrer, a flat blade stirrer, etc. can be used as long as the respective fractions in the mixture are sufficiently mixed uniformly.

[0037] In some embodiments, the stirring speed is 10 r / min to 1000 r / min, specifically, but not limited to, 10 r / min, 50 r / min, 70 r / min, 100 r / min, 120 r / min, 150 r / min, 200 r / min, 300 r / min, 350 r / min, 400 r / min, 500 r / min, or 1000 r / min. Controlling the stirring speed within the above range is advantageous for mixing the fractions to form a uniform mixture.

[0038] The stirring may be carried out at room temperature or in a preheated state, and preferably the stirring temperature may be controlled to 25°C to 200°C. As will be understood, appropriate preheating is advantageous for mixing each fraction to form a uniform mixture.

[0039] In some embodiments, the pressing method includes at least one of extrusion, die pressing, roll pressing, and isostatic pressing.

[0040] In some embodiments, the pressing pressure is 5 MPa to 100 MPa, and may be, for example, 5 MPa, 15 MPa, 25 MPa, 30 MPa, 35 MPa, 40 MPa, 45 MPa, 50 MPa, 55 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, or 100 MPa. Pressing can improve the fluidity of the material during the graphitization process, thereby accelerating the cooling rate during the graphitization temperature reduction process and favoring control of the micromorphology, specific surface area, and tap density, and can also improve furnace loading and production capacity.

[0041] In some embodiments, the carbonization temperature may be, for example, 1000°C, 1050°C, 1100°C, 1200°C, 1300°C, 1400°C, or 1500°C, but is not limited to the listed values, and other unlisted values ​​within the range also apply. As will be understood, a carbonization temperature within the above range is advantageous for removing substances such as volatile components in the raw material and for forming a pore structure that meets demand.

[0042] In some embodiments, the incubation time for the carbonization treatment is 2 hours to 6 hours, and specifically may be 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, or 6 hours, but is not limited to the recited values, and other unrecited values ​​within the range also apply.

[0043] In some embodiments, the carbonized product is obtained by natural cooling after the carbonization treatment.

[0044] In some embodiments, the temperature for graphitization may be, for example, 2800°C, 2900°C, 3000°C, 3050°C, 3100°C, 3150°C, 3180°C, or 3200°C, but is not limited to the listed values, and other unlisted values ​​within the ranges also apply.

[0045] In some embodiments, the incubation time for the graphitization treatment is 2 hours to 5 hours, and specifically may be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 3.8 hours, 4 hours, 4.5 hours, or 5 hours, but is not limited to the recited values, and other unrecited values ​​within the range also apply. Preferably, the incubation time for the graphitization treatment is 2 hours to 3 hours.

[0046] In some embodiments, the heating rate of the graphitization treatment is 12°C / min to 25°C / min, and may be, for example, 12°C / min, 13°C / min, 15°C / min, 18°C / min, 20°C / min, or 25°C / min, but is not limited to the listed values, and other unlisted values ​​within the range also apply. Rapid heating is advantageous for controlling the pore volume and specific surface area of ​​the material, while simultaneously reducing heat dissipation and production costs.

[0047] In some embodiments, the graphitization treatment temperature reduction rate is 22°C / min to 26°C / min, and specifically may be 22°C / min, 23°C / min, 24°C / min, 24.5°C / min, 25°C / min, 25.5°C / min, or 26°C / min, but is not limited to the recited values, and other unrecited values ​​within the range also apply. Rapid temperature reduction can significantly shorten the graphitization process cycle and reduce production costs.

[0048] In some embodiments, the ratio of the heating rate in the graphitization process to the heating rate in the carbonization process is controlled to be between 4 and 8, and may be specifically 4, 4.5, 5, 6, 7, or 8. Maintaining both heating rates within the above ranges can affect the pore structure, surface micromorphology, and friction conditions of the material, which is advantageous for controlling the specific surface area and tap density of the material, and can also achieve the formation of a certain amount of pore volume inside the artificial graphite without using a pore-forming agent.

[0049] In some embodiments, the graphitization treatment is followed by at least one of pulverization, sieving, and demagnetization. Preferably, the carbonization treatment is followed by pulverization, demagnetization, and sieving, in that order.

[0050] In some embodiments, the grinding means is any one of a mechanical grinder, an airflow grinder, and a cryogenic grinder.

[0051] In some embodiments, the sieving method is any one selected from a fixed sieve, a drum screen, a resonating sieve, a roller sieve, a vibrating sieve, and a chain grizzly, and the mesh number of the sieve is 100 to 500 mesh. Specifically, the mesh number of the sieve may be 100 mesh, 200 mesh, 250 mesh, 325 mesh, 400 mesh, 500 mesh, etc. Controlling the particle size of the negative electrode material within the above range contributes to improving the processing characteristics of the negative electrode material.

[0052] In some embodiments, the demagnetizing device is any one selected from a permanent magnet drum magnetic separator, an electromagnetic iron remover, and a pulsating high gradient magnetic separator, and the demagnetization is performed to ultimately control the content of magnetic materials in the negative electrode material, to avoid the discharging effect of the magnetic materials on the battery, and to ensure the safety of the battery during use.

[0053] The negative electrode material according to one embodiment includes artificial graphite and has pores inside and / or on the surface of the artificial graphite. The negative electrode material has a pore volume of Vcm 3 / kg, and the specific surface area is Sm 2 When the V×S / T is 8.5≦V×S / T≦27, where V×S / T is the saturation coefficient and Tg / mL is the tap density, the pore volume was measured using an ASAP 2460 device manufactured by Micromeritics, Inc., USA, and calculated using the BJH Desorption cumulative volume of pores model within the pore diameter range of 17 Å to 3000 Å.

[0054] The negative electrode material provided by the present application is produced and processed by a continuous graphitization process, and the time and temperature at which all materials pass through the high temperature zone are synchronized, and the temperature rise and fall rate is controlled, so that volatile components, impurity elements and other substances in the material can be uniformly and quickly released, thereby making the pore volume, specific surface area and tap density of the material reach the ideal adjustment and control design requirements.

[0055] Generally, the pore volume of artificial graphite within a certain range is +Increase the diffusion channel of Li + This reduces the diffusion resistance of the material, thereby effectively improving the rate performance of the material. A specific surface area within a certain range ensures sufficient electrochemical reaction interfaces, promotes lithium ion diffusion at solid-liquid interfaces and within the solid phase, reduces concentration polarization, and is beneficial for improving the capacity and rate performance of the anode material. Through extensive research, the applicant has found that when lithium ions move, their migration rate is not only related to the migration space (i.e., the pore volume size) and the size of the reaction interface, but also to the friction conditions on the artificial graphite surface. Therefore, sufficient pore volume and specific surface area do not necessarily guarantee complete and smooth lithium ion desorption / absorption; the friction conditions can directly affect the tap density. Limiting V×S / T within this range ensures that lithium ions can more smoothly desorb and absorb within the artificial graphite material particles with adequate space and reaction interfaces, thereby significantly improving the rate and capacity of the material.

[0056] In some embodiments, the negative electrode material has a pore volume of Vcm 3 When the viscosity is 1000 ppm or less, V is 5.0≦V≦8.0 when the viscosity is 1000 ppm or less, and specifically, V may be 5.0, 5.1, 5.2, 5.5, 5.8, 6.0, 6.3, 6.5, 6.8, 6.9, 7.0, 7.1, 7.5, 7.6, 7.8, or 8.0, etc., but is not limited thereto.

[0057] In some embodiments, the pores include at least one of micropores and mesopores. Micropores are pores with a diameter of less than 2 nm, and mesopores are pores with a diameter of 2 nm to 50 nm. The formation of abundant pores within and / or on the surface of graphite is advantageous for creating more lithium ion diffusion channels, thereby improving the electrochemical performance of the negative electrode material.

[0058] In some embodiments, the average pore diameter of the pores is 50 Å to 200 Å. Specifically, the average pore diameter of the pores may be specifically 50 Å, 60 Å, 70 Å, 100 Å, 150 Å, or 200 Å, etc.

[0059] In some embodiments, the negative electrode material has a specific surface area of ​​Sm 2 / g, S is 1.78≦S≦3.00, and specifically, it may be 1.78, 1.85, 1.95, 2.00, 2.25, 2.43, 2.57, 2.61, 2.72, 2.75, 2.80, 3.00, etc., but is not limited thereto. As can be understood, if the specific surface area is too large, it is likely to cause the formation of a solid electrolyte film, and the irreversible lithium salt is excessively consumed, resulting in a decrease in the initial efficiency of the battery.

[0060] In some embodiments, the tap density of the negative electrode material, when expressed as Tg / ml, is 0.734≦T≦1.160, and specifically may be, but is not limited to, 0.734, 0.751, 0.768, 0.784, 0.797, 0.818, 0.822, 0.837, 0.863, 0.989, 0.963, 0.958, 0.983, 0.981, 0.997, 1.012, 1.023, 1.033, 1.041, 1.086, or 1.160.

[0061] In some embodiments, the negative electrode material has a (002) plane spacing of d 002 When the 002 ≦3.364Å. 002 is within the above range, it can be seen that the graphite crystallinity of the artificial graphite particles is high, that is, the degree of graphitization is high.

[0062] In some embodiments, the negative electrode material has a particle size D 50 is 10 μm to 30 μm. Specifically, it may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 20 μm, 25 μm, or 30 μm, and is not limited thereto. Specifically, it can be obtained by measuring the particle size at 50% in the cumulative particle size distribution on a volume basis of the negative electrode material by a laser diffraction method. Preferably, the particle size D of the negative electrode material 50 is 10μm to 20μm.

[0063] In some embodiments, the negative electrode material includes synthetic graphite primary particles and / or synthetic graphite secondary particles.

[0064] In some embodiments, the negative electrode material further comprises amorphous carbon. As will be understood, after the adhesive is graphitized, a portion is difficult to convert to graphitized carbon, and a portion that cannot be converted to graphitized carbon exists on the surface of the artificial graphite particles in the form of amorphous carbon.

[0065] In some embodiments, the mass ratio of amorphous carbon in the negative electrode material is 0.1 wt % to 5 wt %, and the presence of a small amount of amorphous carbon provides more irregular and more open diffusion paths for lithium ions, which is advantageous for improving the rate capability of the material.

[0066] In some embodiments, the negative electrode material has a specific capacity of 320 mAh / g to 370 mAh / g, and specifically, the specific capacity may be, but is not limited to, 320 mAh / g, 340 mAh / g, 342 mAh / g, 345 mAh / g, 353 mAh / g, 355 mAh / g, 357 mAh / g, 360 mAh / g, 365 mAh / g, or 370 mAh / g.

[0067] In some embodiments, the initial coulombic efficiency of the negative electrode material is 93% or greater, and may be, but is not limited to, 93.0%, 93.1%, 94.3%, 94.4%, 94.5%, 94.6%, 94.7%, 94.8%, 94.9%, or 95.1%.

[0068] A battery comprising the above negative electrode material.

[0069] As will be apparent to those skilled in the art, the battery manufacturing method described above is merely an example, and other methods commonly used in the art may be employed without departing from the scope of the present invention, and other types of batteries, such as sodium ion batteries and potassium ion batteries, may be manufactured and measured. [Example]

[0070] The present application will be further described below with reference to several examples. However, the present application is not limited to the following specific examples. Appropriate modifications can be made within the scope of protection.

[0071] Example 1 The method for producing the negative electrode material according to this embodiment is as follows: (1) crushing Shandong Jingyang coke and shaping it with a shaping device to obtain crushed and shaped coke powder, and controlling the median diameter to 12 μm; (2) uniformly mixing coke powder, coal tar, and quinoline in a mass ratio of 100:5:20 to obtain a mixture; (3) pressing the mixture at a pressure of 20 MPa to obtain a precursor; (4) carbonizing the precursor at a temperature of 1100°C for 4 hours, with a temperature increase rate of 3.3°C / min during the carbonization process, and cooling to obtain a carbonized product; (5) The carbonized material is graphitized in a continuous graphitization furnace at 3100°C to obtain a graphitized product. The temperature rise curve is as follows: the temperature is raised to 3100°C at a rate of 17.2°C / min, the temperature is maintained at 3100°C for 3 hours, and then the temperature is lowered to 30°C at a rate of 25.6°C / min. The ratio of the temperature rise rate in the graphitization process to the temperature rise rate in the carbonization process is controlled to 5.2. (6) The graphitized product is subjected to a dispersion, demagnetization, and sieving process to obtain an artificial graphite negative electrode material.

[0072] The negative electrode material includes primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0073] Example 2 The method for producing the negative electrode material according to this embodiment is as follows: (1) crushing raw coke from Jingyang Needle Coke Co., Ltd. in Shandong Province and shaping it with a shaping device to obtain crushed and shaped coke powder, and controlling the median diameter to 12 μm; (2) uniformly mixing coke powder, phenolic resin, and water in a mass ratio of 100:5:20 to obtain a mixture; (3) pressing the mixture at a pressure of 20 MPa to obtain a precursor; (4) carbonizing the precursor at a temperature of 1100°C for 4 hours, with a temperature increase rate of 3.3°C / min during the carbonization process, and cooling to obtain a carbonized product; (5) The carbonized material is graphitized in a continuous graphitization furnace at 3100°C to obtain a graphitized product. The temperature rise curve is as follows: the temperature is raised to 3100°C at a rate of 16.0°C / min for 3.2 hours, the temperature is maintained at 3100°C for 3 hours, and then the temperature is lowered to 30°C at a rate of 22°C / min for 2.3 hours. The ratio of the temperature rise rate in the graphitization process to the temperature rise rate in the carbonization process is controlled to 4.8. (6) The graphitized product is subjected to a dispersion, demagnetization, and sieving process to obtain an artificial graphite negative electrode material.

[0074] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0075] Example 3 The method for producing the negative electrode material according to this embodiment is as follows: (1) crushing raw coke from Daqing petroleum coke and shaping it with a shaping device to obtain crushed and shaped coke powder, and controlling the median diameter to 15 μm; (2) uniformly mixing coke powder, coal tar, and quinoline in a mass ratio of 100:5:15 to obtain a mixture; (3) pressing the mixture at a pressure of 20 MPa to obtain a precursor; (4) carbonizing the precursor at a temperature of 1200°C for 3 hours, with a heating rate of 3.2°C / min, and cooling to obtain a carbonized product; (5) The carbonized material is graphitized in a continuous graphitization furnace at 3000°C to obtain a graphitized product. The temperature rise curve is as follows: the temperature is raised to 3000°C at a temperature rise rate of 13.5°C / min for 3.7 hours, the temperature is maintained at 3000°C for 3 hours, and then the temperature is lowered to 30°C at a temperature drop rate of 24.7°C / min for 2 hours. The ratio of the temperature rise rate in the graphitization treatment to the temperature rise rate in the carbonization treatment is controlled to 4.2. (6) The graphitized product is subjected to a dispersion, demagnetization, and sieving process to obtain an artificial graphite negative electrode material.

[0076] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0077] Example 4 The method for producing the negative electrode material of this example is as follows: (1) crushing raw coke from Daqing petroleum coke and shaping it with a shaping device to obtain crushed and shaped coke powder, and controlling the median diameter to 15 μm; (2) uniformly mixing coke powder, phenolic resin, and water in a mass ratio of 100:5:15 to obtain a mixture; (3) pressing the mixture at a pressure of 20 MPa to obtain a precursor; (4) carbonizing the precursor at a temperature of 1150°C for 4 hours, with a heating rate of 3.1°C / min, and cooling to obtain a carbonized product; (5) The carbonized material is graphitized in a continuous graphitization furnace at 3000°C to obtain a graphitized product. The temperature rise curve is as follows: the temperature is raised to 3000°C at a temperature rise rate of 14.3°C / min for 3.5 hours, the temperature is maintained at 3000°C for 3 hours, and then the temperature is lowered to 30°C at a temperature drop rate of 22.5°C / min for 2.2 hours. The ratio of the temperature rise rate in the graphitization treatment to the temperature rise rate in the carbonization treatment is controlled to 4.6. (6) The graphitized product is subjected to a dispersion, demagnetization, and sieving process to obtain an artificial graphite negative electrode material.

[0078] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0079] Example 5 The difference from Example 1 is that the carbonization temperature in step (4) is 1500°C.

[0080] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0081] Example 6 The difference from Example 1 is that the carbonization temperature in step (4) is 1000°C.

[0082] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0083] Example 7 The difference from Example 1 is that the carbonization time in step (4) is 3 hours.

[0084] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0085] Example 8 The difference from Example 1 is that the carbonization time in step (4) is 6 hours.

[0086] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0087] Example 9 The difference from Example 1 is that in step (2), coke powder, coal tar, and quinoline are uniformly mixed in a mass ratio of 100:3:20 to obtain a mixture.

[0088] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0089] Example 10 The difference from Example 9 is that the raw material used in step (1) is Daqing petroleum coke, and in step (2), coke powder, coal tar and quinoline are uniformly mixed in a mass ratio of 100:20:20 to obtain mixture A.

[0090] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite. As can be seen from the scanning electron microscope images of FIGS. 1 and 2, the majority of the material is secondary particles of artificial graphite, and the overall surface is flat and the morphology is good.

[0091] Example 11 The difference from Example 9 is that the raw material used in step (1) is raw coke from Jinzhou Petrochemical Petroleum Coke, and in step (2), coke powder, coal tar and quinoline are uniformly mixed in a mass ratio of 100:5:5 to obtain a mixture.

[0092] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0093] Example 12 The difference from Example 10 is that in step (2), coke powder, coal tar, and quinoline are uniformly mixed in a mass ratio of 100:5:50 to obtain a mixture.

[0094] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0095] Example 13 The difference from Example 10 is that in step (2), coke powder, phenol resin, and ethanol are uniformly mixed in a mass ratio of 100:5:20 to obtain a mixture.

[0096] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0097] Example 14 The difference from Example 10 is that in step (2), coke powder, epoxy resin, and water are uniformly mixed in a mass ratio of 100:5:20 to obtain a mixture.

[0098] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0099] Example 15 The difference from Example 10 is that the pressing pressure in step (3) is 5 MPa.

[0100] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0101] Example 16 The difference from Example 10 is that the pressing pressure in step (3) is 100 MPa.

[0102] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0103] Example 17 The difference from Example 10 is that the graphitization temperature in step (5) is 3000°C.

[0104] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0105] Example 18 The difference from Example 10 is that the graphitization temperature in step (5) is 3200°C.

[0106] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0107] Example 19 The difference from Example 10 is that the temperature rise curve in the graphitization process in step (5) is that the temperature rises to 3000°C at a rate of 12°C / min.

[0108] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0109] Example 20 The difference from Example 10 is that the temperature retention time for the graphitization treatment in step (5) is 5 hours.

[0110] The negative electrode material obtained in this example contains primary particles of artificial graphite and secondary particles of artificial graphite, the majority of which is primary particles of artificial graphite.

[0111] Comparative Example 1 The difference from Example 1 is that in step (5), the carbonized material is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace for graphitization to obtain a negative electrode material. The temperature rise curve for the graphitization process is to raise the temperature to 3100°C at a heating rate of 0.7°C / min, maintain the temperature for 3 hours, and then cool to 30°C at a heating rate of 0.1°C / min. The ratio of the heating rate for the graphitization process to the heating rate for the carbonization process is controlled to 0.2, thereby obtaining a negative electrode material.

[0112] Comparative Example 2 Raw coke from Jingyang Needle Coke in Shandong Province was crushed and shaped using a shaping device. The resulting coke powder, with a median diameter of 12 μm, was carbonized at 1100°C for 4 hours. The carbonized coke powder was placed in a graphite crucible, which was then transferred to an Acheson furnace for graphitization to obtain the anode material. The temperature rise curve for the graphitization process was as follows: the temperature was raised to 3100°C at a rate of 0.7°C / min, held at that temperature for 8 hours, and then cooled to 30°C at a rate of 0.1°C / min. The ratio of the heating rate for the graphitization process to the heating rate for the carbonization process was controlled to 0.2, resulting in the anode material.

[0113] Comparative Example 3 The raw coke raw material from Jingyang Needle Coke in Shandong Province is carbonized at a temperature of 1100°C for 4 hours, and then fed into a conventional continuous graphitization furnace for graphitization. The temperature rise curve for the graphitization process is to heat up to 2900°C at a heating rate of 9.6°C / min, hold the temperature for 3 hours, and then cool down to 30°C at a heating rate of 10°C / min. The ratio of the heating rate during the graphitization process of the negative electrode material obtained after shaping and crushing to the heating rate during the carbonization process is controlled to 2, thereby obtaining the negative electrode material.

[0114] Measurement method (1) The particle size of the negative electrode material is measured by measuring the particle size distribution range of the negative electrode material using a Malvern laser particle size analyzer. (2) The specific surface area of ​​the negative electrode material is measured using a dynamic specific surface area high-speed measuring instrument JW-DX manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd., and the unit is m 2 / g. (3) The method for measuring the surface morphology of the negative electrode material is to observe the surface morphology of the negative electrode material particles using a Hitachi S4800 scanning electron microscope. (4) The tap density of the negative electrode material was measured using a Quanta tap density analyzer, Dual Autotap, manufactured by Anton Paar (Shanghai) Trading Co., Ltd. The tap density T was measured after 1,000 vibrations, and its unit was g / mL. (5) The method for measuring the interlayer distance of the graphite crystal planes in the negative electrode material is to measure the interlayer distance d of the (002) plane of the graphite crystals in the negative electrode material by X-ray diffraction. 002 and has units of Å. (6) Battery performance was measured by magnetically stirring the negative electrode materials prepared in Examples 1 to 20 and Comparative Examples 1 to 3, carboxymethyl cellulose, conductive carbon black, and styrene-butadiene rubber in a mass ratio of 95:1.5:1.5:2 in deionized water for 8 hours. The resulting slurry was applied to copper foil and vacuum dried at 60°C to prepare a working electrode. Metallic lithium was used as the counter electrode and reference electrode. The separator was Celgard 2325, and the electrolyte was 1 mol L LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1). CR2016 coin batteries were assembled in a glove box filled with high-purity argon gas.

[0115] The initial discharge capacity / initial discharge efficiency measurements were performed using a LAND battery measuring device. The charge / discharge conditions were as follows: let stand for 2 hours, discharge at 0.1C to 0.005V, then discharge at 0.09C, 0.08C...0.02C to 0.001V, let stand for 15 minutes, charge at 0.1C to 1.5V, and let stand for 15 minutes.

[0116] The rate characteristics of the button-type half-cell were measured under an environment of 25±2°C, and the charge / discharge specific capacity and coulomb efficiency were obtained at 0.2C, 1C, and 2C. The charge and discharge conditions for rate measurement of the button cell were: (1) discharge at 0.1C to 0.01V, hold at constant voltage for 5 hours, and charge at 0.1C to 1.5V; (2) discharge at 0.2C to 0.01V, hold at constant voltage to 0.01C, and charge at 0.2C to 1.5V; (3) discharge at 0.2C to 0.01V, hold at constant voltage to 0.01C, and charge at 2C to 1.5V; (4) discharge at 0.2C to 0.01V, hold at constant voltage to 0.01C, and charge at 0.2C to 1.5V; (5) discharge at 1C to 0.01V, hold at constant voltage to 0.01C, and charge at 0.2C to 1.5V; (6) discharge at 2C to 0.01V.

[0117] The full battery measurements are as follows: The negative electrode material prepared in each example was used as the negative electrode active material. The mass percentages of the negative electrode active material, conductive agent, binder, and dispersant were dissolved and mixed in water so that the mass percentage was 95.2:1.5:2:1.3, and the solid content was controlled to 50 wt%. The mixture was applied to an 8 μm-thick copper foil current collector and dried in a vacuum to prepare a negative electrode piece. Lithium iron phosphate, polyvinylidene fluoride, and conductive agent carbon black were uniformly mixed with a solvent NMP (N-methylpyrrolidone) in a mass ratio of 95:2:3, and then applied to a 16 μm-thick aluminum foil and dried in a vacuum to prepare a positive electrode piece. The coated positive and negative electrode pieces were subjected to the processes of piece preparation, winding, drying, injection, sealing, chemical synthesis, and capacity grading to prepare a 554065-type soft-pack lithium-ion battery.

[0118] The obtained soft-pack battery was subjected to a charge-discharge test using the LAND battery test system of Wuhan King Nuo Electronics Co., Ltd., charging and discharging at a current of 1C / 1C under room temperature conditions, limiting the charge-discharge voltage to 3.0V to 4.35V, and measuring the initial efficiency and 500-week capacity retention rate (press density of the negative electrode piece was 1.60g / cm). 3 ), The above performance measurement results are shown in the table below.

[0119] [Table 1]

[0120] [Table 2]

[0121] As can be seen from the measurement data in Examples 1 to 20, pores are formed inside and / or on the surface of the graphite produced in the examples of the present application, and the pores serve as additional lithium storage spaces, improving the lithium storage capacity of the anode material, with a specific capacity of 343 mAh / g or more. Controlling V×S / T within the range of 8.5 to 27 ensures that lithium ions are absorbed and released more smoothly inside the anode material particles at appropriate spatial and reactive interfaces, thereby improving the electrochemical performance of the anode material.

[0122] The negative electrode material produced by the discontinuous graphitization process in Comparative Example 1 had a specific surface area that was too large, a tap density that was too small, and a V×S / T that was outside the above range. Compared with Examples 1 and 2 produced from the same types of raw materials, the specific capacity and rate characteristics of the material were significantly reduced.

[0123] In the negative electrode material produced by the discontinuous graphitization process in Comparative Example 2, the pores of the artificial graphite were not sufficiently abundant, the pore volume V was too small, the tap density was too large, and V×S / T was outside the above range. As a result, the number of available active sites on the surface of the artificial graphite as a negative electrode material, where reactions to release and absorb lithium occur, was reduced, and the rate characteristics of the material were significantly reduced.

[0124] In Comparative Example 3, a negative electrode material was produced using a continuous graphitization process, but no binder was added, and the graphitization temperature increase / decrease rate and the ratio of the graphitization temperature increase rate to the carbonization temperature increase rate were not controlled. As a result, V×S / T was outside the above range, and the capacity and rate characteristics were inferior to those of Examples 1 and 2 produced under the same process conditions.

[0125] Although the present application has been disclosed above by way of preferred embodiments, it does not limit the scope of the claims, and any person skilled in the art may make some possible changes or modifications without departing from the technical idea of ​​the present application, so the scope of protection of the present application should conform to the scope defined in the claims.

Claims

1. A negative electrode material for a lithium ion battery, comprising artificial graphite having pores inside and / or on the surface thereof, The negative electrode material has a pore volume of V cm 3 / kg, and the specific surface area is Sm 2 / g and tap density is Tg / mL, 8.5≦V×S / T≦27, The pore volume was measured using an ASAP 2460 device manufactured by Micromeritics, Inc., USA, and calculated using the BJH Desorption cumulative volume of pores model within the pore diameter range of 17 Å to 3000 Å. When the pore volume is V cm 3 / kg, 5.0≦V≦8.0; When the specific surface area is expressed as Sm 2 / g, 1.78≦S≦3.00; A negative electrode material for a lithium ion battery, characterized in that, when the tap density is expressed as Tg / mL, 0.734≦T≦1.

160.

2. The negative electrode material for a lithium ion battery according to claim 1, characterized in that it satisfies at least one of the following characteristics (1) to (2): (1) The pores include at least one of micropores and mesopores; (2) The average pore diameter of the pores is 50 Å to 200 Å.

3. When measured by X-ray diffraction, the interplanar spacing of the (002) plane of the graphite crystal is d 002 When the 002 2. The negative electrode material of claim 1, wherein the thickness is ≦3.364 Å.

4. Particle size D in the volume-based cumulative particle size distribution measured by a laser diffraction method 50 The negative electrode material for a lithium ion battery according to claim 1, characterized in that the particle size is 10 μm to 30 μm.

5. 2. The negative electrode material for a lithium ion battery according to claim 1, comprising primary particles of artificial graphite and / or secondary particles of artificial graphite.

6. The negative electrode material for a lithium ion battery according to claim 1, characterized in that it satisfies at least one of the following characteristics (1) to (2): (1) The negative electrode material further includes amorphous carbon; (2) The negative electrode material further contains amorphous carbon, and the mass ratio of the amorphous carbon in the negative electrode material is 0.1 wt % to 5 wt %.

7. A battery comprising the negative electrode material for a lithium ion battery according to any one of claims 1 to 6.

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