Negative electrode material and battery

Abstract

The present application provides a negative electrode material and a battery. The negative electrode material comprises graphite, pores are formed in the graphite and / or on the surface of the graphite, the oil absorption value of the negative electrode material is O mL / 100g, the pore volume is V cm3 / kg, the specific surface area is S m2 / g, and the powder porosity is Φ%, wherein 50≤O*V*S≤391, and 40≤Φ≤58. According to the negative electrode material and the battery provided by the present application, the negative electrode material has a relatively sufficient reaction space in which effective lithium ion deintercalation can be performed, and the high-rate charging and discharging performance of the graphite negative electrode material can be improved.

Description

Anode materials, batteries Technical Field

[0001] The present application relates to the technical field of negative electrode materials, and in particular, to negative electrode materials and batteries. Background Art

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

[0003] Graphite materials also have many shortcomings as negative electrode materials for lithium-ion batteries: In lithium-ion batteries, the electrolyte absorption performance of the material and the electrode will have a significant impact on the battery's ultimate performance. Poor negative electrode absorption performance may lead to a limited reactive area of ​​the graphite negative electrode material, resulting in insufficient electrochemical active sites, limiting the battery's rate performance and forming lithium deposition, which in turn deteriorates the battery's rate performance and capacity utilization, seriously affecting the battery's safety and cycle life. Therefore, good material absorption performance and effective reactive area have a good promoting effect on the rate performance and capacity utilization of lithium-ion batteries.

[0004] Therefore, at the current stage when graphite materials have already developed to a very mature stage, it is difficult to further optimize the rate performance by simply improving a single parameter. Currently, in-depth research based on the synergistic effects of multiple factors is urgently needed to maximize the rate performance of graphite.

[0005] Application Contents

[0006] In view of this, the present application provides a negative electrode material and a battery, comprehensively considering the synergistic effects of graphite's oil absorption value, pore volume, specific surface area and powder porosity on the negative electrode material, and developing a negative electrode material to increase the active sites and diffusion channels for lithium ion deintercalation in the negative electrode material, thereby improving the high-rate charge and discharge performance of the negative electrode material.

[0007] In a first aspect, the present application provides a negative electrode material, wherein the negative electrode material comprises graphite, wherein the graphite has pores inside and / or on the surface, and the oil absorption value of the negative electrode material is 0 mL / 100 g and the pore volume is V cm 3 / kg, specific surface area is S m 2 / g, the powder porosity is Φ%, wherein 50≤O*V*S≤391, and 40≤Φ≤58, the pore volume is measured by ASAP2460 equipment of American Micromeritics Company, and the BJH Desorption cumulative volume of pores model is used. Calculated within the pore size range.

[0008] In some embodiments, the oil absorption value of the negative electrode material is 0 mL / 100 g, and 30≤0≤62.

[0009] In some embodiments, the pore volume V cm of the negative electrode material is 3 / kg, 1.812≤V≤5.012.

[0010] In some embodiments, the specific surface area of ​​the negative electrode material is S m 2 / g, 0.872≤S≤1.781.

[0011] In some embodiments, the particle size of the negative electrode material satisfies the following relationship: 12 μm ≤ D 50 ≤20μm.

[0012] In some embodiments, the negative electrode material further includes amorphous carbon, which exists on the surface of graphite and / or is dispersed between graphite particles.

[0013] In some embodiments, the amorphous carbon accounts for 0.1 wt % to 5 wt % of the negative electrode material.

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

[0015] In some embodiments, the pores include at least one of micropores and mesopores.

[0016] In some embodiments, the negative electrode material is measured by X-ray diffraction, and the interlayer spacing of the (002) plane is d002, The crystal layer stacking thickness Lc obtained by X-ray diffraction is

[0017] In some embodiments, the negative electrode material is measured by X-ray diffraction, and under the pressure condition of 9T, the integrated intensity I of the peak of the (004) surface of the negative electrode material is 004 The integrated intensity I of the peak of the (110) surface of the negative electrode material 110 The ratio satisfies: 1.0≤I 004 / I 110 ≤5.0.

[0018] In a second aspect, the present application provides a battery, comprising the graphite negative electrode material according to the first aspect.

[0019] The technical solution of this application has at least the following beneficial effects:

[0020] The negative electrode material provided in the present application includes graphite, which has pores inside and / or on the surface. The oil absorption value of the negative electrode material is 0 mL / 100 g, and the pore volume is V cm 3 / kg, specific surface area is S m 2 / g, the powder porosity is Φ%, where 50≤O*V*S≤391, and 40≤Φ≤58. On the one hand, powder porosity is a comprehensive property related to factors such as particle morphology, particle surface state, particle size and particle size distribution. It is a parameter that has a great influence on the powder processing performance. Appropriate powder porosity is conducive to the preparation of graphite negative electrode sheets with a certain compaction density, ensuring their better performance; on the other hand, a larger pore volume can increase Li + The diffusion channel and the larger specific surface area can ensure sufficient electrochemical reaction interface, promote the diffusion of lithium ions at the solid-liquid interface and in the solid phase, reduce concentration polarization, and help improve the capacity and rate performance of the negative electrode material. However, if the pore volume and specific surface area are only suitable, the rate performance of the negative electrode material still has a lot of room for improvement, because lithium ion deintercalation not only requires diffusion channels and reaction interfaces, but also requires electrolyte as a medium. Some pores cannot be wetted by the electrolyte due to the influence of surface morphology or other factors, and they cannot play their role. Naturally, the corresponding surface cannot undergo electrochemical reaction, which is equivalent to insufficient "effective electrochemical reaction space". The electrolyte infiltration ability is usually reflected by the oil absorption value. The present application conducts a large number of experimental explorations on the combination of the three factors of pore volume, specific surface area and oil absorption value, controls the O*V*S of the negative electrode material within the above range, and controls the powder porosity of the material at the same time, so that the negative electrode material has sufficient reaction space that is conducive to lithium ion deintercalation, which is beneficial to improving the high-rate charge and discharge performance of the graphite negative electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a scanning electron microscope image of the graphite negative electrode material provided in Example 11 of the present application.

[0022] Figure 2 is a scanning electron microscope image of the graphite negative electrode material provided in Example 12 of the present application. DETAILED DESCRIPTION

[0023] To better illustrate the present application and facilitate understanding of the technical solution of the present application, the present application is further described below. However, the following embodiments are merely simplified examples of the present application and do not represent or limit the scope of protection of the present application. The scope of protection of the present application shall be subject to the claims.

[0024] A negative electrode material comprises graphite, wherein the graphite has pores inside and / or on the surface, the oil absorption value of the negative electrode material is 0 mL / 100 g, and the pore volume is V cm 3 / kg, specific surface area is S m 2 / g, powder porosity is Φ%, where 50≤O*V*S≤391, and 40≤Φ≤58. The pore volume was measured using ASAP2460 equipment from Mack, USA, and the BJH Desorption cumulative volume of pores model. Calculated within the pore size range.

[0025] Graphite has pores inside and / or on its surface. The oil absorption value of the negative electrode material is 0 mL / 100 g and the pore volume is V cm 3 / kg, specific surface area is S m 2 / g, the powder porosity is Φ%, where 50≤O*V*S≤391, and 40≤Φ≤58.

[0026] Generally, particles with larger pore volume can increase Li +The diffusion channels and large specific surface area can ensure sufficient electrochemical reaction interface, promote the diffusion of lithium ions at the solid-liquid interface and in the solid phase, reduce concentration polarization, and help improve the capacity and rate performance of the negative electrode material. However, if the pore volume and specific surface area are only suitable, there is still room for improvement in the rate performance of the negative electrode material, because lithium ion deintercalation not only requires diffusion channels and reaction interfaces, but also requires electrolyte as a medium. Lithium ions diffuse through the electrolyte to achieve the purpose of lithium ion deintercalation and lithium storage. The lithium ion storage method includes the interlayer diffusion of lithium ions in graphite to achieve the purpose of lithium storage, accompanied by edge lithium storage and surface lithium storage. Among them, graphite interlayer lithium storage is the process of lithium ions embedding into the graphite interlayer, which is an intercalation process from high order to low order. The carbon atoms exposed at the edge of the graphite sheet are in an amorphous state with high energy, which is the active site of lithium ions and can achieve edge lithium storage. The bonding between carbon atoms on the graphite surface and lithium ions is similar to edge lithium storage, that is, surface lithium storage is achieved. Some pores cannot be wetted by the electrolyte due to the influence of surface morphology, pore structure or other factors, and thus cannot play their role. Due to capillary action, part of the electrolyte first wets the pores between the graphite particles, and part of it wets the surface or internal pores of the graphite particles. However, the simple control of pore volume or specific surface area commonly used in the prior art is only explored on the single increase in the number of open pores. According to the diffusion mechanism of lithium ions in the electrolyte and graphite particles, the applicant found that there are also some closed pores in the graphite particles, and there are also carbon atoms at the defect ends of the closed pores that can react with lithium ions to form edge lithium storage. However, in actual processes, since closed pores are difficult to be accurately characterized, whether the existence of closed pores will affect the performance of graphite materials is often ignored. In addition, there are open pores distributed on the surface and inside of graphite. In addition to reacting with lithium ions to achieve edge lithium storage, the carbon at the defect ends of the open pores can also be wetted by the electrolyte inside the pores due to capillary phenomena. However, due to different pore structures and depths, the degree of wetting will also be different. In addition, after the pores between the particles are wetted, the outer surface active sites of the graphite particles are more, and a solid electrolyte membrane will be formed on the surface of the particles. However, if a large number of electrolyte cations are gathered on the surface of the graphite particles, concentration polarization is likely to occur, thereby inhibiting the diffusion of lithium ions. Naturally, no electrochemical reaction can occur on its surface, which is equivalent to insufficient "effective electrochemical reaction space". In summary, the morphology of pores (including open pores and closed pores) and pore distribution have an impact on the lithium storage method of graphite particles and the surface / internal wetting of graphite particles that should not be ignored. At the same time, the surface of graphite particles and the surface pores will also have a certain influence on the pores between graphite particles formed by the stacking method of graphite particles, which further reflects the wetting ability of graphite particles and the lithium storage method.This application conducts a large number of experimental explorations on the combination of three factors: pore volume, specific surface area and oil absorption value, controls the O*V*S of the negative electrode material within the above range while controlling the powder porosity Φ of the material, and conducts in-depth research on the pore characteristics between graphite particles, the surface morphology of graphite particles, the open pores on the surface, and the internal pore structure and closed pore characteristics, thereby increasing the lithium ion diffusion channel so that after the graphite particles are fully infiltrated with the electrolyte, lithium ions are rapidly transmitted within the graphite through the surface and internal pore channels, and the polarization caused by excessive surface adsorption and infiltration of electrolyte is reduced, thereby further improving the lithium ion transmission rate and the sustained ability of the rapid lithium ion transmission rate, so that the negative electrode material has sufficient reaction space that is conducive to lithium ion deintercalation, which is beneficial to improving the high-rate charge and discharge performance of the graphite negative electrode material.

[0027] In some embodiments, the negative electrode material has an oil absorption value of 0 mL / 100 g, with a range of 30 ≤ 0 ≤ 62; specifically, it may be 30, 35, 40, 45, 50, 55, or 60, etc., without limitation herein. Controlling the material's oil absorption value within this range improves the material's adsorption and wettability with the electrolyte, thereby enhancing the negative electrode material's electrochemical performance.

[0028] In some embodiments, the pore volume V cm of the negative electrode material is 3 / kg, 1.812≤V≤5.012, specifically 1.812, 1.897, 1.945, 2.003, 2.224, 2.675, 2.755, 2.874, 2.807, 3.443, 4.203, or 5.012, etc., are not limited here. When electrochemical reactions occur in the pores within the electrode, the pores create more lithium ion diffusion channels and electrochemical reaction interfaces for the negative electrode material, which can promote the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduce concentration polarization, and help improve the rate performance of the negative electrode material.

[0029] In some embodiments, the specific surface area of ​​the negative electrode material is S m 2 / g, 0.872≤S≤1.781; specifically, it can be 1.781, 1.713, 1.598, 1.501, 1.445, 1.327, 1.308, 1.179, 1.106, 1.007, 0.966, or 0.879, etc., without limitation herein. It is understandable that an excessively large specific surface area can easily lead to the formation of a solid electrolyte membrane, consuming excessive amounts of irreversible lithium salt, and reducing the initial efficiency of the battery.

[0030] In some embodiments, the powder porosity of the negative electrode material is Φ%, 40≤Φ≤58; specifically, it can be 40, 41.1, 42.1, 45.9, 44.5, 43.3, 45.5, 47.5, 47.8, 48.3, 50.6, 51.3, 52.2, 52.8, 53.4, 55.1, 55.2, 56.1, 56.2, 56.8, 57.6, etc., without limitation herein. It is understood that controlling the powder porosity of the negative electrode material is beneficial to increasing the compaction density of the electrode sheet, and is beneficial to increasing the degree of sufficient infiltration of the graphite particles with the electrolyte, allowing lithium ions to be rapidly transported within the graphite through the surface and internal pore channels, and reducing polarization caused by excessive surface adsorption and infiltration of the electrolyte, thereby ensuring better performance.

[0031] In some embodiments, the pores include at least one of micropores and mesopores.

[0032] In some embodiments, the particle size D of the negative electrode material is 50 The particle size distribution of the particles is 12 μm to 20 μm. Specifically, it can be 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 19 μm or 20 μm, etc., which are not limited here. It should be noted that the volume-based cumulative particle size distribution of the particle size distribution is measured by laser diffraction method, D 50 It indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 50%.

[0033] In some embodiments, the negative electrode material also includes amorphous carbon, and the mass proportion of amorphous carbon in the negative electrode material is 0.1wt% to 5wt%. The mass proportion of amorphous carbon in the negative electrode material can specifically be 0.1wt%, 0.3wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%. The presence of amorphous carbon provides more irregular and open diffusion paths for lithium ions, which is beneficial to improving the rate performance of the material.

[0034] In some embodiments, the amorphous carbon exists on the surface of graphite and / or is dispersed between graphite particles.

[0035] In some embodiments, the negative electrode material is measured by X-ray diffraction, and the interlayer spacing of the (002) plane is d 002 , The crystal layer stacking thickness Lc obtained by X-ray diffraction is Crystal plane interlayer spacing d 002 Within the above range, it can be seen that the graphite crystallinity of the graphite particles is high, that is, the degree of graphitization is high, and the capacity of the product is high.

[0036] In some embodiments, the negative electrode material is measured by X-ray diffraction, and the integrated intensity I of the peak of the (004) plane of the negative electrode material is 004 The integrated intensity I of the peak of the (110) surface of the negative electrode material 110 The ratio satisfies: 1.0≤I 004 / I 110 ≤5.0, I 004 / I 110 In this range, the orientation degree of the negative electrode material is relatively high and the cycle expansion is low.

[0037] In some embodiments, the negative electrode material includes artificial graphite primary particles and / or artificial graphite secondary particles. In some embodiments, the pores include at least one of micropores and mesopores.

[0038] In some embodiments, the specific capacity of the negative electrode material is 330mAh / g to 380mAh / g, specifically 330mAh / g, 340mAh / g, 342mAh / g, 345mAh / g, 353mAh / g, 355mAh / g, 357mAh / g, 360mAh / g, 370mAh / g or 380mAh / g, etc., which is not limited here.

[0039] The present application also provides a method for preparing a negative electrode material, comprising the following steps:

[0040] S10, shaping the coke raw material to obtain coke powder with a median particle size of 10 μm to 20 μm;

[0041] S20, carbonizing the mixture containing the coke powder and the binder at 500° C. to 1200° C. to obtain a carbonized product, wherein the mass ratio of the coke powder to the binder is 100:(3-15);

[0042] S30, placing the carbonized product at 300° C. to 600° C. in an oxygen-containing atmosphere for oxidation treatment for 2 h to 6 h to obtain a precursor;

[0043] S40, placing the precursor at 2800° C. to 3200° C. for graphitization treatment to obtain a negative electrode material.

[0044] The preparation method of the negative electrode material provided by the present application is to shape the coke raw material into coke powder, and then carbonize the mixture of the coke powder and the binder. During the carbonization process, the impurities, volatiles and unstable substances in the coke powder will decompose and lose. After carbonization, the binder coke raw material and the binder in a fluid state are solidified and formed. The carbonized product is then oxidized. The oxidation treatment can form a rich microporous structure on the surface of the material. Finally, the precursor is graphitized. During the high-temperature graphitization treatment, the microporous structure formed by partial pre-oxidation continues to expand the pore diameter and deepen the pore depth as the volatile matter evaporates, thereby increasing the lithium ion diffusion channel. At the same time, due to the escape of impurities in the raw material and the volatilization of organic matter, a large In the later stage of high temperature, due to the complete volatilization of impurities and organic matter and the orderly arrangement of carbon atoms, some pores of pyrolytic carbon begin to shrink and collapse, and eventually some closed pores appear. The remaining part forms open channels with a developed network structure, so that after the graphite particles are fully infiltrated by the electrolyte, lithium ions are quickly transported inside the graphite through the surface and internal pore channels, and the polarization caused by excessive surface adsorption and infiltration of electrolyte is reduced, thereby further improving the lithium ion transmission rate and the sustained ability of lithium ion rapid transmission rate, so that the negative electrode material has sufficient reaction space that is conducive to lithium ion deintercalation, which is beneficial to improving the high-rate charge and discharge performance of the graphite negative electrode material.

[0045] In some embodiments, the coke feedstock includes at least one of petroleum coke, needle coke, pitch coke, and isotropic coke.

[0046] In some embodiments, shaping comprises at least one of comminuting, spheroidizing, or classifying.

[0047] The median particle size of the shaped coke powder is 10 to 20 μm. More specifically, it can be 12 μm, 13 μm, 14 μm, 16 μm, 18 μm, 18.5 μm, 19 μm, or 20 μm, but these values ​​are not limited to the listed values. Other values ​​not listed in this range are also applicable. Numerous tests have shown that controlling the median particle size of the coke powder within this range is beneficial for achieving a balanced balance between processability, capacity, and rate capability.

[0048] In some embodiments, the heating rate of the carbonization process is specifically 2°C / min, 3°C / min, 5°C / min, 6°C / min, 8°C / min, 9°C / min, or 10°C / min. It can be understood that the heating rate of the carbonization process within the above range is conducive to the slow escape of volatiles in the raw materials and the initial formation of a pore structure, which, combined with the rapid heating in the subsequent graphitization process, can obtain a negative electrode material that meets 50≤O*V*S≤391.

[0049] In some embodiments, the carbonization temperature can be 500°C, 550°C, 600°C, 700°C, 750°C, 800°C, 850°C, 900°C, 1000°C, or 1200°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable. It is understood that a carbonization temperature within the above range is conducive to the discharge of volatile substances and other substances in the coke fines.

[0050] In some embodiments, the holding time for the carbonization treatment can be 2 hours, 3 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours, but is not limited to the listed values. Other values ​​not listed in the numerical range are also applicable. Preferably, the holding time for the carbonization treatment is 3 hours to 4 hours.

[0051] In some embodiments, the binder includes at least one of coal tar, petroleum asphalt, petroleum resin, phenolic resin, epoxy resin, coumarone resin, and furan resin. Specifically, the petroleum asphalt can be petroleum asphalt, modified asphalt, and mesophase asphalt.

[0052] In some embodiments, the mass ratio of coke powder to binder is 100:(3-15), specifically 100:3, 100:5, 100:8, 100:10, 100:12, 100:13 or 100:15, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some embodiments, the mixture is mixed by at least one of mechanical stirring and ultrasonic dispersion. When mechanical stirring is used, a propeller stirrer, a turbine stirrer, a flat-blade stirrer, etc. can be used, as long as the components in the mixture are fully mixed.

[0054] In some embodiments, the stirring rate is 10 r / min to 1000 r / min, and specifically can be 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, etc., without limitation herein. Controlling the stirring rate within the above range is conducive to mixing the components to form a uniform mixture.

[0055] The stirring can be carried out at room temperature or in a preheated state. Preferably, the stirring temperature can be controlled at 25°C to 200°C. It can be understood that appropriate preheating is conducive to mixing the components to form a uniform mixture.

[0056] In some embodiments, the oxidation treatment temperature can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, or 600°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable. It can be understood that the oxidation treatment temperature within the above range can form a rich and appropriate amount of microporous structure on the material surface, constructing ideal graphite surface ion channels.

[0057] In some embodiments, the holding time for the oxidation treatment can be 2 hours, 3 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable. Preferably, the holding time for the oxidation treatment is 3 hours to 4 hours.

[0058] In some embodiments, the oxygen-containing atmosphere includes at least one of air and a mixed gas with an oxygen content of greater than 30%.

[0059] In some embodiments, the holding temperature of the graphitization treatment can be specifically 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3100°C or 3200°C, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0060] In some embodiments, the holding time for the graphitization treatment can 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 listed values. Other values ​​not listed within the numerical range are also applicable. Preferably, the holding time for the graphitization treatment is 2 hours to 3 hours.

[0061] In some embodiments, the graphitization heating rate may be 2°C / min to 10°C / min, specifically 2°C / min, 3°C / min, 4°C / min, 6°C / min, or 8°C / min, but is not limited to the values ​​listed above. Other values ​​not listed within this range are also applicable. A specific heating rate is beneficial for controlling the formation of pores inside and / or on the surface of the graphite material and the specific surface area.

[0062] In some embodiments, after the graphitization treatment, at least one of pulverization, screening, and demagnetization is further performed. Preferably, after the carbonization treatment, pulverization, demagnetization, and screening are further performed in sequence.

[0063] In some embodiments, the pulverization method is any one of a mechanical pulverizer, a jet mill, and a low-temperature pulverizer.

[0064] In some embodiments, the screening method is any one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen and a chain screen, and the screening mesh number is 100 to 500 meshes. Specifically, the screening mesh number can be 100 mesh, 200 mesh, 250 mesh, 325 mesh, 400 mesh, 500 mesh, etc. The particle size of the negative electrode material is controlled within the above range, which is beneficial to improving the processing performance of the negative electrode material.

[0065] In some embodiments, the demagnetization equipment is any one of a permanent magnetic drum magnetic separator, an electromagnetic iron remover, and a pulsating high gradient magnetic separator. The purpose of demagnetization is to ultimately control the magnetic material content of the negative electrode material, avoid the discharge effect of the magnetic material on the lithium-ion battery, and the safety of the battery during use.

[0066] The following further illustrates the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Within the scope of protection, appropriate changes can be made to the implementation.

[0067] Example 1

[0068] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0069] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0070] (2) The coke powder and the coal tar binder were mixed uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder was controlled to be 100:15, and the mixture was carbonized at 1000°C for 10 hours;

[0071] (3) The carbonized product was oxidized in an air atmosphere at 600°C for 6 h to obtain a precursor;

[0072] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, and the Acheson furnace is heated to 3000°C at a rate of 10°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0073] Example 2

[0074] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0075] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0076] (2) mixing the coke powder and the petroleum asphalt binder uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder is controlled to be 100:13, and carbonizing the mixture at 1000°C for 10 hours;

[0077] (3) The carbonized product was oxidized in an air atmosphere at 600°C for 6 h to obtain a precursor;

[0078] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, which is heated to 3000°C at a rate of 8°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0079] Example 3

[0080] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0081] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0082] (2) mixing the coke powder and the petroleum resin binder uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder is controlled to be 100:11, and carbonizing the mixture at 1000°C for 10 hours;

[0083] (3) The carbonized product was oxidized in an air atmosphere at 600°C for 6 h to obtain a precursor;

[0084] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, which is heated to 3000°C at a rate of 6°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0085] Example 4

[0086] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0087] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0088] (2) mixing the char powder and the phenolic resin binder uniformly to obtain a mixture, wherein the mass ratio of the char powder to the binder is controlled to be 100:9, and carbonizing the mixture at 1000°C for 10 hours;

[0089] (3) The carbonized product was oxidized in an air atmosphere at 500°C for 4 h to obtain a precursor;

[0090] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, which is heated to 3000°C at a rate of 4°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0091] Example 5

[0092] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0093] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0094] (2) mixing the coke powder and the epoxy resin binder uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder is controlled to be 100:7, and carbonizing the mixture at 1000°C for 10 hours;

[0095] (3) oxidizing the carbonized product in an air atmosphere at 500°C for 4 h to obtain a precursor;

[0096] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, which is heated to 3000°C at a rate of 3°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0097] Example 6

[0098] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0099] (1) The petroleum coke raw material is crushed and shaped by a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0100] (2) mixing the coke powder and the coumarone resin binder uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder is controlled to be 100:5, and carbonizing the mixture at 800°C for 10 hours;

[0101] (3) The carbonized product was oxidized in an air atmosphere at 400°C for 4 h to obtain a precursor;

[0102] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, which is heated to 2900°C at a rate of 2°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0103] Example 7

[0104] The method for preparing the negative electrode material of this embodiment includes the following steps:

[0105] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0106] (2) mixing the coke powder and the furan resin binder uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder is controlled to be 100:3, and carbonizing the mixture at 500°C for 10 hours;

[0107] (3) The carbonized product was oxidized in an air atmosphere at 300°C for 2 h to obtain a precursor;

[0108] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, which is heated to 3000°C at a rate of 7°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0109] Example 8

[0110] The only difference from Example 1 is that the raw material used in step (1) is needle coke.

[0111] Example 9

[0112] The only difference from Example 2 is that the raw material used in step (1) is needle coke.

[0113] Example 10

[0114] The only difference from Example 3 is that the raw material used in step (1) is needle coke.

[0115] Example 11

[0116] The only difference from Example 4 is that the raw material used in step (1) is needle coke.

[0117] Example 12

[0118] The only difference from Example 5 is that the raw material used in step (1) is needle coke.

[0119] Example 13

[0120] The only difference from Example 6 is that the raw material used in step (1) is needle coke.

[0121] Example 14

[0122] The only difference from Example 7 is that the raw material used in step (1) is needle coke.

[0123] Example 15

[0124] The only difference from Example 1 is that the raw material used in step (1) is pitch coke.

[0125] Example 16

[0126] The only difference from Example 2 is that the raw material used in step (1) is pitch coke.

[0127] Example 17

[0128] The only difference from Example 3 is that the raw material used in step (1) is pitch coke.

[0129] Example 18

[0130] The only difference from Example 4 is that the raw material used in step (1) is pitch coke.

[0131] Example 19

[0132] The only difference from Example 5 is that the raw material used in step (1) is pitch coke.

[0133] Example 20

[0134] The only difference from Example 6 is that the raw material used in step (1) is pitch coke.

[0135] Comparative Example 1

[0136] (1) crushing the petroleum coke raw material and shaping it through a shaping device to obtain coke powder with a median particle size of 15 μm after crushing and shaping;

[0137] (2) The coke powder and the coal tar binder were mixed uniformly to obtain a mixture, wherein the mass ratio of the coke powder to the binder was controlled to be 100:15, and the mixture was carbonized at 1200°C for 10 hours;

[0138] (3) oxidizing the carbonized product in an air atmosphere at 600°C for 15 h to obtain a precursor;

[0139] (4) The precursor is placed in a graphite crucible, and then the graphite crucible is transferred to an Acheson furnace, and the Acheson furnace is heated to 3000°C at a rate of 10°C / min for high-temperature graphitization treatment for 8 hours to obtain a graphite negative electrode material.

[0140] Comparative Example 2

[0141] The Daqing petroleum coke raw material was crushed and shaped by shaping equipment to obtain crushed and shaped coke powder. The obtained coke powder with a median particle size of 15μm was directly loaded into a graphite crucible, and then the graphite crucible was transferred to an Acheson furnace for high-temperature graphitization to obtain the negative electrode material. The heating rate of the graphitization process was 4℃ / min, the maximum temperature was 2900℃, and the maximum temperature holding time was 8h.

[0142] Test Method

[0143] (1) Test method for particle size of negative electrode material:

[0144] The particle size distribution range of the composite negative electrode material was tested by Malvern laser particle size analyzer.

[0145] (2) Testing method of pore volume of negative electrode material:

[0146] The test was carried out using the ASAP2460 equipment from American Micromeritics. The pore volume V was calculated using the BJH Desorption cumulative volume of pores model. Calculated within the pore size range.

[0147] (3) Testing method for specific surface area of ​​negative electrode material:

[0148] The dynamic specific surface area rapid tester JW-DX of Beijing Jingwei Gaobo Science and Technology Co., Ltd. was used for testing. The unit is m 2 / g.

[0149] (4) Testing method of surface morphology of negative electrode materials:

[0150] The surface morphology of the negative electrode material particles was observed using a Hitachi S4800 scanning electron microscope.

[0151] (5) Test method for oil absorption value of negative electrode material:

[0152] The oil absorption value O is the amount of linseed oil added when the torque generated by the change in viscosity reaches 70% of the maximum torque, and the unit is mL / 100g.

[0153] (6) X-ray diffraction characterization of the interlayer spacing d of the (002) plane of the material 002 , the unit is The crystal layer stacking thickness Lc and the peak intensity ratio I between the (004) plane and the (110) plane obtained by X-ray diffraction 004 / I 110 .

[0154] (7) Powder porosity test method of negative electrode material:

[0155] The test was conducted using the AutoPore V series high-performance fully automatic mercury intrusion instrument from Micromeritics.

[0156] (8) Battery performance test method:

[0157] The negative electrode materials, carboxymethyl cellulose, conductive carbon black, and styrene-butadiene rubber prepared in Examples 1 to 20 and Comparative Examples 1 to 2 were magnetically stirred in deionized water at a mass ratio of 95:1.5:1.5:2 for 8 hours to mix them evenly. The mixed slurry was coated on copper foil and dried in vacuo at 60°C as a working electrode. Metallic lithium was used as the counter electrode and reference electrode, the diaphragm was Celgard 2325, and the electrolyte was 1 mol·L-1 LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio of 1:1:1). The CR2016 button cell was assembled in a glove box filled with high-purity argon.

[0158] The first discharge capacity / first discharge efficiency test was performed on a LAND battery tester with the following charge and discharge conditions: 2 h rest; discharge: 0.1C to 0.005V, 0.09C, 0.08C…0.02C to 0.001V; 15 min rest; charge: 0.1C to 1.5V; 15 min rest.

[0159] The coin cell half-cell was subjected to rate performance testing at 25±2°C, and the charge-discharge specific capacity and coulombic efficiency at 0.2C, 1C, and 2C were obtained. The charge-discharge conditions for the coin cell rate test were as follows: ① 0.1C discharge to 0.01V, constant voltage for 5h, 0.1C charge to 1.5V; ② 0.2C discharge to 0.01V, constant voltage to 0.01C, 0.2C charge to 1.5V; ③ 0.2C discharge to 0.01V, constant voltage to 0.01C, 2C charge to 1.5V; ④ 0.2C discharge to 0.01V, constant voltage to 0.01C, 0.2C charge to 1.5V; ⑤ 1C discharge to 0.01V, constant voltage to 0.01C; 0.2C charge to 1.5V; ⑥ 2C discharge to 0.01V.

[0160] Full battery test: The negative electrode material prepared in each embodiment was used as the negative electrode active material, and the mass percentage of the negative electrode active material, conductive agent, binder, and dispersant was 95.2:1.5:2:1.3. It was dissolved in deionized water and mixed to control the solid content to 50wt%. The mixture was coated on an 8μm thick copper foil current collector and vacuum dried to prepare a negative electrode sheet; lithium iron phosphate, polyvinylidene fluoride, and conductive agent carbon black were mixed in a mass ratio of 95:2:3 with solvent NMP (N-methylpyrrolidone), coated on a 16μm thick aluminum foil, and vacuum dried to prepare a positive electrode sheet; the coated positive and negative electrode sheets were subjected to sheeting, winding, drying, liquid injection, sealing, formation, and volume separation processes to make a 554065 soft-pack lithium-ion battery.

[0161] The obtained soft pack battery was charged and discharged on the LAND battery test system of Wuhan Jinnuo Electronics Co., Ltd. At room temperature, 1C / 1C current was charged and discharged, and the charge and discharge voltage was limited to 3.0V~4.35V. The first efficiency and 500-week capacity retention rate tests were performed (the compaction density of the negative electrode sheet was 1.60g / cm 3 );

[0162] Tablet absorption test: The powder sample is prepared into a slurry using a JS-24FS powder tablet press, dried, ground, and sieved, and then pressed into a pole piece using a pressure of 4400 pounds. After rebounding for 8 hours, the liquid absorption time of the tablet is tested.

[0163] The results of the performance test of the negative electrode material obtained in the above embodiment are shown in Table 1 below, and the results of the performance test of the battery made of the negative electrode material are shown in Table 2 below:

[0164] Table 1. Comparison of negative electrode material performance

[0165] Table 2. Battery performance comparison results

[0166] The test data from Examples 1 to 20 demonstrate that the pores formed within and / or on the surface of the graphite produced in the present invention enhance the material's high-rate charging performance. This is because, when the negative electrode material is made into an electrode for use in a lithium-ion battery, after the electrolyte is injected, the material has ample space for effective electrochemical reactions, which helps improve the negative electrode material's rate performance.

[0167] By controlling the powder porosity of the negative electrode material between 40% and 58%, while satisfying the above range of 50≤O*V*S≤391, and at the same time controlling the powder porosity of the material, it is beneficial to improve the compaction density of the graphite negative electrode sheet, and to improve the degree of full infiltration of the graphite particles with the electrolyte. Lithium ions are quickly transported within the graphite through the surface and internal pore channels, and the polarization caused by excessive surface adsorption and infiltration of the electrolyte is reduced, thereby ensuring that it has better performance.

[0168] The negative electrode material prepared in Comparative Example 1 has too much pore volume, the oil absorption value O is too large, and O*V*S is out of the above range. After the pores between the particles are infiltrated, a solid electrolyte membrane will be formed on the surface of the particles and surface adsorption and lithium storage will be formed at the same time. The electrolyte cations that gather more on the surface of the graphite particles will undergo concentration polarization, thereby inhibiting the diffusion of lithium ions. Naturally, no electrochemical reaction can occur on its surface, and the "effective electrochemical reaction space" of the negative electrode material will decrease, resulting in poor cycle performance of the material.

[0169] In the negative electrode material prepared in Comparative Example 2, the raw coke material was directly graphitized after carbonization treatment during the preparation process without oxidation treatment. The artificial graphite pores were not rich enough, the pore volume V was too small, the specific surface area was also reduced, O*V*S was out of the above range, and there was no sufficient diffusion channel for lithium ions, which was not conducive to improving the rate performance of the negative electrode material.

[0170] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any person skilled in the art may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A negative electrode material, characterized in that: The negative electrode material comprises graphite, the graphite has pores inside and / or on the surface, the oil absorption value of the negative electrode material is 0 mL / 100 g, and the pore volume is V cm 3 / kg, specific surface area is S m 2 / g, the powder porosity is Φ%, wherein 50≤O*V*S≤391, and 40≤Φ≤58. The pore volume is tested by using ASAP2460 equipment from Mack, USA, and the BJH Desorption cumulative volume of pores model. Calculated within the pore size range.

2. The negative electrode material according to claim 1, characterized in that The oil absorption value of the negative electrode material is 0 mL / 100 g, 30≤0≤62.

3. The negative electrode material according to claim 1, characterized in that The pore volume V cm of the negative electrode material 3 / kg, 1.812≤V≤5.

012.

4. The negative electrode material according to claim 1, characterized in that The specific surface area of ​​the negative electrode material is S m 2 / g, 0.872≤S≤1.

781.

5. The negative electrode material according to claim 1, characterized in that The particle size of the negative electrode material satisfies the following relationship: 12 μm ≤ D 50 ≤20μm.

6. The negative electrode material according to any one of claims 1 to 5, characterized in that The negative electrode material further includes amorphous carbon, which exists on the graphite surface and / or is dispersed between graphite particles.

7. The negative electrode material according to claim 6, characterized in that It meets at least one of the following characteristics: (1) The mass percentage of the amorphous carbon in the negative electrode material is 0.1wt% to 5wt%; (2) The negative electrode material comprises artificial graphite primary particles and / or artificial graphite secondary particles; (3) The pores include at least one of micropores and mesopores.

8. The negative electrode material according to any one of claims 1 to 5, characterized in that The negative electrode material is measured by X-ray diffraction, and the interlayer spacing of the (002) plane is d002. The crystal layer stacking thickness Lc obtained by X-ray diffraction is 9. The negative electrode material according to any one of claims 1 to 5, characterized in that The negative electrode material is measured by X-ray diffraction. Under the pressure condition of 9T, the peak integrated intensity I of the (004) surface of the negative electrode material is 004 The integrated intensity I of the peak of the (110) plane of the negative electrode material 110 The ratio satisfies: 1.0≤I 004 / I 110 ≤5.

0.

10. A battery, characterized in that: The battery comprises the negative electrode material according to any one of claims 1 to 9.

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