Negative electrode material, battery

Abstract

This application provides a negative electrode material and a battery. 【Solution means】The negative electrode material contains graphite, has pores inside and / or on the surface of the graphite, and when the negative electrode material has an oil absorption of OmL / 100g, a pore volume of Vcm 3 / kg, a specific surface area of Sm 2 / g, and a powder porosity of Φ%, 50 ≦ O × V × S ≦ 391 and 40 ≦ Φ ≦ 58. Regarding the negative electrode material and the battery provided by this application, there is a relatively sufficient reaction space for effectively releasing and storing lithium ions in the negative electrode material, which is advantageous for improving the high-rate charge and discharge performance of the graphite negative electrode material.

Description

Technical Field

[0001] This application relates to the technical field of anode materials, specifically to anode materials and batteries.

Background Art

[0002] Graphite has advantages such as high electrical conductivity, large lithium ion diffusion coefficient, small volume change before and after lithium intercalation in the layered structure, high lithium intercalation capacity, and low lithium intercalation potential. Therefore, it has become the mainstream commercial anode material for lithium ion batteries.

[0003] Graphite materials also have many drawbacks as anode materials for lithium ion batteries. The liquid absorption performance of the materials and electrode sheets in a lithium ion battery towards the electrolyte has a great impact on the final performance of the battery. Poor anode liquid absorption performance limits the reactive area of the graphite anode material, resulting in insufficient electrochemical active sites, restricting the rate performance of the battery, forming lithium deposition, further deteriorating the rate performance and capacity utilization of the battery, and potentially having a serious impact on the safety and cycle life of the battery. Therefore, good liquid absorption performance and effective reactive area of the materials have a good promoting effect on the rate performance and capacity utilization of lithium ion batteries.

[0004] Therefore, at the current stage where the development of graphite materials has already matured, it is difficult to further optimize the rate performance by simply improving parameters. Currently, in order to maximize the improvement of the rate performance of graphite, it is necessary to intensively study the synergistic effect among multiple factors.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of this, the present application provides a negative electrode material and a battery, and comprehensively considers the synergistic effects of the oil absorption amount, pore volume, specific surface area, and powder porosity of graphite on the negative electrode material, increasing the active sites and diffusion channels for lithium ion release and storage in the negative electrode material, and developing a negative electrode material to improve the high-rate charge and discharge performance of the negative electrode material.

Means for Solving the Problems

[0006] In a first aspect, the present application provides a negative electrode material, the negative electrode material includes graphite, has pores inside and / or on the surface of the graphite, and when the negative electrode material has an oil absorption amount of OmL / 100g, a pore volume of Vcm 3 / kg, a specific surface area of Sm 2 / g, and a powder porosity of Φ%, 50 ≦ O × V × S ≦ 391 and 40 ≦ Φ ≦ 58, and the pore volume is measured using an ASAP 2460 device manufactured by Micromeritics, USA, and calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0007] In some embodiments, when the negative electrode material has an oil absorption amount of OmL / 100g, 30 ≦ O ≦ 62.

[0008] In some embodiments, when the negative electrode material has a pore volume of Vcm 3 / kg, 1.812 ≦ V ≦ 5.012.

[0009] In some embodiments, when the negative electrode material has a specific surface area of Sm 2 / g, 0.872 ≦ S ≦ 1.781.

[0010] In some embodiments, the negative electrode material satisfies the relational expression of 12 μm ≦ D 50 ≦ 20 μm.

[0011] In some embodiments, the negative electrode material further includes amorphous carbon, and the amorphous carbon is present on the surface of the graphite and / or dispersed between the graphite particles.

[0012] In some embodiments, the mass ratio of the amorphous carbon in the negative electrode material is 0.1 wt% to 5 wt%.

[0013] In some embodiments, the negative electrode material includes artificial graphite primary particles and / or artificial graphite secondary particles.

[0014] In some embodiments, the pores include at least one of micropores and mesopores.

[0015] In some embodiments, when the negative electrode material is subjected to X-ray diffraction measurement and the interlayer spacing of the crystal plane of the (002) plane is d 002 it satisfies 3.358 Å ≤ d 002 ≤ 3.365 Å, and the stacking thickness Lc of the crystal layer plane obtained by X-ray diffraction is 400 Å to 450 Å.

[0016] In some embodiments, when the negative electrode material is subjected to X-ray diffraction measurement under a pressure condition of 9 T, the ratio of the integrated intensity I 004 of the peak of the (004) plane of the negative electrode material to the integrated intensity I 110 of the peak of the (110) plane of the negative electrode material satisfies 1.0 ≤ I 004 / I 110 ≤ 5.0.

[0017] In a second aspect, the present application provides a battery including the graphite negative electrode material described in the first aspect.

Advantages of the Invention

[0018] The technical means of the present application has at least the following beneficial effects.

[0019] The negative electrode material provided by the present application includes graphite, has pores inside and / or on the surface of the graphite, and the negative electrode material has an oil absorption amount of OmL / 100 g and a pore volume of Vcm 3per kg, with a specific surface area of Sm 2 per g, when the powder porosity is Φ%, 50 ≤ O×V×S ≤ 391 and 40 ≤ Φ ≤ 58. On the other hand, the powder porosity is a comprehensive property related to factors such as particle morphology, particle surface state, particle size and particle size distribution, and is a parameter that greatly affects the powder processing performance. An appropriate powder porosity is beneficial for the manufacture of a graphite negative electrode plate having a certain compression density, ensuring good performance. While a large pore volume can increase the diffusion channels of Li + , and a large specific surface area can ensure a sufficient electrochemical reaction interface, promote the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduce concentration polarization, and is beneficial for improving the capacity and rate performance of the negative electrode material. However, only satisfying the appropriate pore volume and specific surface area, there is still room for further improvement in the rate performance of the negative electrode material. Lithium ion release and absorption not only require diffusion channels and reaction interfaces, but also require an electrolyte as a medium. Some pores are not infiltrated by the electrolyte due to the influence of surface morphology or other factors, so their functions cannot be exerted, and naturally no electrochemical reaction can occur on the corresponding surface, which corresponds to insufficient "effective electrochemical reaction space". Also, the infiltration ability of the electrolyte is generally manifested by the oil absorption amount. This application combines three factors of pore volume, specific surface area and oil absorption amount to conduct a large number of experimental studies, controls the O×V×S of the negative electrode material within the above range, and controls the powder porosity of the material, so that the negative electrode material has a sufficient reaction space favorable for lithium ion release and absorption, which is beneficial for improving the high rate charge and discharge performance of the graphite negative electrode material.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0021] To better explain the present application and make it easier to understand the technical solution of the present application, the present application will be described in more detail below. It should be noted that the following examples are only simplified examples of the present application and do not indicate or limit the protection scope of the present application. The protection scope of the present application shall conform to the scope of the claims.

[0022] A negative electrode material containing graphite, having pores inside and / or on the surface of the graphite, the negative electrode material having an oil absorption amount of OmL / 100g, a pore volume of Vcm 3 / kg, a specific surface area of Sm 2 / g, and a powder porosity of Φ%, when 50 ≤ O × V × S ≤ 391 and 40 ≤ Φ ≤ 58, and the pore volume is measured using an ASAP 2460 device manufactured by Micromeritics, USA, and calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0023] Having pores inside and / or on the surface of the graphite, the negative electrode material having an oil absorption amount of OmL / 100g, a pore volume of Vcm 3 / kg, a specific surface area of Sm 2 / g, and a powder porosity of Φ%, when 50 ≤ O × V × S ≤ 391 and 40 ≤ Φ ≤ 58.

[0024] Generally, particles with a large pore volume have Li +The diffusion channels can be increased, and a large specific surface area can ensure a sufficient electrochemical reaction interface, promote the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduce concentration polarization, and is beneficial to improving the capacity and rate performance of the anode material. However, the release and insertion of lithium ions not only require diffusion channels and reaction interfaces but also an electrolyte as a medium. Lithium ions achieve the purpose of lithium storage through the release and insertion of lithium ions by means of the diffusion of the electrolyte. The lithium storage mode of lithium ions is that lithium ions diffuse between the graphite layers to achieve the purpose of lithium storage, and is accompanied by lithium storage at the ends and on the surface. Therefore, only an appropriate pore volume and specific surface area are satisfied, and there is still room for improvement in the rate performance of the anode material. Here, the lithium storage between graphite layers is a process in which lithium ions are inserted between graphite layers, which is an intercalation process from high order to low order. The carbon atoms exposed at the ends of the graphite sheet layer are in an amorphous state, with high energy, and are active sites for lithium ions, and lithium storage can be realized at the ends. The binding between the carbon atoms on the graphite surface and lithium ions is similar to that of lithium storage at the ends, that is, lithium storage on the surface is realized.Some pores are affected by surface morphology, pore channel structure or other elements and cannot be wetted by the electrolyte, thus failing to exert their functions. However, due to capillary action, part of the electrolyte first infiltrates into the voids between graphite particles, and part infiltrates into the surface or internal voids of graphite particles. Nevertheless, in the prior art, research is simply conducted by increasing the number of open pores by merely controlling the pore volume or specific surface area. According to the diffusion mechanism of lithium ions in the electrolyte and graphite particles, the applicant has discovered that there are some closed pores in graphite particles, and there are also carbon atoms capable of participating in the lithium ion reaction at the defective ends of the closed pores, forming lithium storage at the ends. However, in the actual process, since it is difficult to accurately characterize the closed pores, whether the existence of closed pores affects the performance of the graphite material is often ignored. In addition to the distribution of open pores on the surface and inside of the graphite, the carbon at the defective ends of the open pores can react with lithium ions to achieve lithium storage at the ends. The inside of the pore channel may also be infiltrated by the electrolyte due to capillary action, but due to different pore channel structures and depths, the infiltration degree is also different. Moreover, after the interparticle voids are infiltrated, if there are many outer surface active sites on the graphite particles, a solid electrolyte film will be formed on the particle surface. If many electrolyte cations aggregate on the surface of the graphite particles, concentration polarization is likely to occur, further suppressing the diffusion of lithium ions, and naturally no electrochemical reaction can occur on its surface, corresponding to the insufficient "effective electrochemical reaction space". From the above, there are non-negligible effects of the morphology of pores (including open pores and closed pores) and pore distribution on the lithium storage mode of graphite particles and functions such as surface / inner infiltration of graphite particles. The surface and surface closed pores of graphite particles also have a certain influence on the voids of graphite particles formed by the deposition mode of graphite particles, thereby further reflecting the infiltration ability and lithium storage mode of graphite particles.This application conducts a large number of experimental studies by combining three elements: pore volume, specific surface area, and oil absorption amount. It controls the O×V×S of the anode material within the above range, controls the powder porosity Φ of the material, deeply explores the void characteristics between graphite particles, the surface morphology of graphite particles, the open pore voids and internal void structure on the surface, and the closed pore characteristics, enlarges the lithium-ion diffusion channels. After the graphite particles are sufficiently infiltrated by the electrolyte, lithium ions are rapidly transmitted into the graphite through the surface and internal void passages, reducing the polarization caused by the adsorption of excessive electrolyte infiltrated on the surface. Thereby, the transmission speed of lithium ions and the sustainable ability to further improve the rapid transmission speed of lithium ions are achieved, enabling the anode material to have a sufficient reaction space favorable for lithium ion release and storage, which is beneficial to improving the high-rate charge-discharge performance of the graphite anode material.

[0025] In some embodiments, when the oil absorption amount of the anode material is OmL / 100g, 30≦O≦62, specifically, it may be 30, 35, 40, 45, 50, 55, or 60, etc., and is not limited herein. Controlling the oil absorption amount of the material within the above range is beneficial to improving the adsorption and infiltration performance of the material for the electrolyte, and the electrochemical performance of the anode material is better.

[0026] In some embodiments, when the anode material has a pore volume of Vcm 3 / kg, 1.812≦V≦5.012, specifically, it may be 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., and is not limited herein. When pores generate electrochemical reactions inside the electrode, the pores can create more lithium-ion diffusion channels and electrochemical reaction interfaces with the anode material, promote the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduce concentration polarization, and are beneficial to improving the rate performance of the anode material.

[0027] In some embodiments, when the anode material has a specific surface area of Sm 2When it is made into / g, 0.872 ≤ S ≤ 1.781, specifically, it may be 1.781, 1.713, 1.598, 1.501, 1.445, 1.327, 1.308, 1.179, 1.106, 1.007, 0.966, 0.879, etc., and is not limited here. As can be understood, if the specific surface area is too large, it is likely to cause the formation of the solid electrolyte membrane, the irreversible lithium salt is excessively consumed, and the initial efficiency of the battery is reduced.

[0028] In some embodiments, when the powder porosity of the negative electrode material is Φ%, 40 ≤ Φ ≤ 58, specifically, it may 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., and is not limited here. As can be understood, controlling the powder porosity of the negative electrode material is advantageous for improving the compression density of the electrode sheet, advantageous for improving the sufficient infiltration degree between the graphite particles and the electrolyte, lithium ions are rapidly transmitted inside the graphite through the surface and the internal pore channels, the polarization caused by the adsorption of the excessive electrolyte infiltrated on the surface is reduced, and good performance is ensured.

[0029] In some embodiments, the pores include at least one of micropores and mesopores.

[0030] In some embodiments, the negative electrode material has a particle size D 50 of 12 μm to 20 μm. Specifically, it may be 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 19 μm, 20 μm, etc., and is not limited here. In the volume-based cumulative particle size distribution measured by the laser diffraction method for measuring the particle size distribution, D 50 represents the corresponding particle size when the percentage of the cumulative particle size distribution reaches 50%.

[0031] In some embodiments, the negative electrode material further includes amorphous carbon. For the negative electrode material, the mass ratio of amorphous carbon is 0.1 wt% to 5 wt%. Specifically, the mass ratio of amorphous carbon in the negative electrode material may be 0.1 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%. The presence of amorphous carbon provides more irregular and more open diffusion paths for lithium ions, which is advantageous for improving the material rate performance.

[0032] In some embodiments, the amorphous carbon is present on the surface of the graphite and / or dispersed between the graphite particles.

[0033] In some embodiments, when the negative electrode material has an interlayer spacing d of the crystal plane of the (002) plane determined by X-ray diffraction measurement 002 such that 3.358 Å ≤ d 002 ≤ 3.365 Å, and the stacking thickness Lc of the crystal plane determined by X-ray diffraction is 400 Å to 450 Å. Since the interlayer distance d of the crystal plane is within the above range, it can be seen that the crystallinity of the graphite particles is high, that is, the graphitization degree is high, and the capacity of the product is high. 002

[0034] In some embodiments, for the negative electrode material, the ratio of the integrated intensity I 004 of the peak of the (004) plane of the negative electrode material to the integrated intensity I 110 of the peak of the (110) plane of the negative electrode material satisfies 1.0 ≤ I 004 / I 110 ≤ 5.0, I 004 / I 110 Within this range, the degree of orientation of the negative electrode material is relatively high and the cycle expansion is low.

[0035] 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.

[0036] ​In some embodiments, the negative electrode material has a specific capacity of 330 mAh / g to 380 mAh / g. Specifically, it may be 330 mAh / g, 340 mAh / g, 342 mAh / g, 345 mAh / g, 353 mAh / g, 355 mAh / g, 357 mAh / g, 360 mAh / g, 370 mAh / g, 380 mAh / g, etc., and is not limited herein.

[0037] This application further provides a method for manufacturing a negative electrode material. S10: Shaping the coke raw material to obtain coke powder with a median diameter of 10 μm to 20 μm. S20: Carbonizing a mixture containing coke powder and a binder at 500°C to 1200°C to obtain a carbonized product. Here, the mass ratio of the coke powder to the binder is 100:(3 to 15). S30: Oxidizing the carbonized product in an oxygen-containing atmosphere at 300°C to 600°C for 2 h to 6 h to obtain a precursor. S40: Graphitizing the precursor at 2800°C to 3200°C to obtain a negative electrode material.

[0038] The method for manufacturing the negative electrode material provided by this application shapes the coke raw material into coke powder, and first carbonizes the mixture of the coke powder and the binder. During the carbonization process, impurities, volatiles, and unstable substances in the coke powder decompose and are lost. After carbonization, the flowing coke raw material and the binder harden and are formed. The carbonization product is further oxidized to form a rich microporous structure on the surface of the material. Finally, the precursor is graphitized. When performing high-temperature graphitization treatment, for some of the pre-formed micropores formed by oxidation, the pore diameter of the pores continues to expand with the volatilization of the volatile components in the early stage, the depth of the pores is increased, the lithium-ion diffusion channel is enlarged, and a large number of pores are formed due to the escape of impurities and the volatilization of organic substances in the raw material. In the later stage of high temperature, since the volatilization of impurities and organic substances is completely regularized according to the arrangement of carbon atoms at the same time, some pores of the pyrolytic carbon begin to shrink, and phenomena such as collapse occur, and finally some closed pores are generated, and the remaining part forms an open pore passage with a developed network structure. Thereby, after the graphite particles are sufficiently infiltrated by the electrolyte, lithium ions are rapidly transmitted into the graphite through the surface and the internal void passage, and the polarization caused by the adsorption of the excessive electrolyte infiltrated on the surface is reduced, thereby achieving the sustainable ability to further improve the transmission speed of lithium ions and the rapid transmission speed of lithium ions, enabling the negative electrode material to have a sufficient reaction space favorable for lithium ion release and storage, which is beneficial to the improvement of the high-rate charge and discharge performance of the graphite negative electrode material.

[0039] In some embodiments, the coke raw material includes at least one of petroleum coke, needle coke, pitch coke, and isotropic coke.

[0040] In some embodiments, the shaping includes at least one of pulverization, spheroidization, or classification.

[0041] The median diameter of the shaped coke powder is 10 μm to 20 μm, and more specifically, it may be 12 μm, 13 μm, 14 μm, 16 μm, 18 μm, 18.5 μm, 19 μm, 20 μm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable. Through multiple tests, controlling the median diameter of the coke powder within the above range is advantageous for achieving both processing performance, capacity, and rate performance.

[0042] In some embodiments, the heating rate during the carbonization process is specifically, for example, 2 °C / min, 3 °C / min, 5 °C / min, 6 °C / min, 8 °C / min, 9 °C / min, or 10 °C / min. As can be understood, the heating rate of the carbonization process being within the above range is advantageous for the gradual escape of volatile components in the raw material, pre-forming the pore structure, and in combination with the rapid heating in the subsequent graphitization process, obtaining a negative electrode material that satisfies 50 ≦ O×V×S ≦ 391.

[0043] In some embodiments, the temperature of the carbonization process may specifically be 500 °C, 550 °C, 600 °C, 700 °C, 750 °C, 800 °C, 850 °C, 900 °C, 1000 °C, 1200 °C, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable. As can be understood, the carbonization process temperature being within the above range is advantageous for the discharge of substances such as volatile components in the coke powder.

[0044] In some embodiments, the heat preservation time of the carbonization process may specifically be 2 h, 3 h, 4 h, 4.5 h, 5 h, 5.5 h, or 6 h, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable. Preferably, the heat preservation time of the carbonization process is 3 h to 4 h.

[0045] In some embodiments, the binder includes at least one of coal pitch, petroleum pitch, petroleum resin, phenolic resin, epoxy resin, coumarone resin, and furan resin. Specifically, the petroleum pitch may be petroleum pitch, modified pitch, mesophase pitch, etc.

[0046] In some embodiments, the mass ratio of coke powder to binder is 100:(3 - 15). Specifically, it may be 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 this numerical range are equally applicable.

[0047] 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, if each component in the mixture is mixed sufficiently uniformly, a propeller stirrer, a turbine stirrer, a flat blade stirrer, etc. can be used.

[0048] In some embodiments, the stirring speed is 10 r / min - 1000 r / min. Specifically, it may 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., and is not limited herein. Controlling the stirring speed within the above range is advantageous for mixing each component to form a uniform mixture.

[0049] The stirring may be carried out at room temperature or in a preheated state. Preferably, the stirring temperature may be controlled at 25°C - 200°C. As can be understood, appropriate preheating is advantageous for mixing each component to form a uniform mixture.

[0050] In some embodiments, the temperature of the oxidation treatment may specifically be, for example, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, or 600°C, etc., but is not limited to the recited values, and other unrecited values within the numerical range are equally applicable. As can be understood, when the oxidation treatment temperature is within the above range, a rich and appropriate amount of microporous structure can be formed on the material surface, and an ideal graphite surface ion channel can be constructed.

[0051] In some embodiments, the heat preservation time of the oxidation treatment may specifically be, for example, 2h, 3h, 4h, 4.5h, 5h, 5.5h, or 6h, etc., but is not limited to the recited values, and other unrecited values within the numerical range are equally applicable. Preferably, the heat preservation time of the oxidation treatment is 3h - 4h.

[0052] In some embodiments, the oxygen-containing atmosphere includes at least one of air and a mixed gas with an oxygen content reaching 30% or more.

[0053] In some embodiments, the heat preservation temperature of the graphitization treatment may specifically be, for example, 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3100°C, or 3200°C, etc., but is not limited to the recited values, and other unrecited values within the numerical range are equally applicable.

[0054] In some embodiments, the heat preservation time of the graphitization treatment may specifically be, for example, 2h, 2.5h, 3h, 3.5h, 3.8h, 4h, 4.5h, or 5h, etc., but is not limited to the recited values, and other unrecited values within the numerical range are equally applicable. Preferably, the heat preservation time of the graphitization treatment is 2h - 3h.

[0055] In some embodiments, the heating rate of the graphitization treatment may be 2°C / min to 10°C / min. Specifically, it may be 2°C / min, 3°C / min, 4°C / min, 6°C / min, or 8°C / min, etc., but is not limited to the recited values, and other unrecited values within this numerical range are equally applicable. A specific heating rate is advantageous for the formation of pores and the control of specific surface area inside and / or on the surface of the material graphite.

[0056] In some embodiments, after the graphitization treatment, at least one of grinding, sieving, and demagnetization is further performed. Preferably, after the carbonization treatment, grinding, demagnetization, and sieving are further performed in sequence.

[0057] In some embodiments, the grinding method may be any one of a mechanical grinder, a pneumatic grinder, and a cryogenic grinder.

[0058] In some embodiments, the sieving method is any one of a fixed sieve, a drum screen, a resonance sieve, a roller sieve, a vibrating sieve, and a chain grizzly. The mesh number of the sieving is 100 to 500 meshes. Specifically, the mesh number of the sieving may be 100 meshes, 200 meshes, 250 meshes, 325 meshes, 400 meshes, 500 meshes, etc. Controlling the particle size of the negative electrode material within the above range is advantageous for improving the processing characteristics of the negative electrode material.

[0059] In some embodiments, the demagnetization device is any one of a permanent magnet drum type magnetic separator, an electromagnetic iron remover, and a pulsating high-gradient magnetic separator. The purpose of demagnetization is to finally control the content of magnetic substances in the negative electrode material to avoid the adverse effects of magnetic substances on the discharge effect of the lithium-ion battery and the safety during the use of the battery.

[0060] Hereinafter, the embodiments of the present application will be further described by way of a plurality of examples. However, the embodiments of the present application are not limited to the following specific examples. Appropriate changes can be made within the protection scope.

[0061] Example 1 The manufacturing method of the negative electrode material in this example is as follows: (1) Step of pulverizing a petroleum coke raw material and shaping it with a shaping device to obtain coke powder with a median diameter of 15 μm after pulverization and shaping; (2) Step of uniformly mixing the coke powder and a coal-based pitch binder to obtain a mixture, controlling the mass ratio of the coke powder to the binder to 100:15, and subjecting the mixture to carbonization treatment at 1000 °C for 10 h; (3) Step of subjecting the carbonization product to oxidation treatment in an air atmosphere at 600 °C for 6 h to obtain a precursor; (4) Step of putting the precursor into a graphite crucible, transferring the graphite crucible into an Acheson furnace, heating the inside of the Acheson furnace to 3000 °C at a rate of 10 °C / min, and performing high-temperature graphitization treatment for 8 h to obtain a graphite negative electrode material.

[0062] Example 2 The manufacturing method of the negative electrode material in this example is as follows: (1) Step of pulverizing a petroleum coke raw material and shaping it with a shaping device to obtain coke powder with a median diameter of 15 μm after pulverization and shaping; (2) Step of uniformly mixing the coke powder and a petroleum-based pitch binder to obtain a mixture, controlling the mass ratio of the coke powder to the binder to 100:13, and subjecting the mixture to carbonization treatment at 1000 °C for 10 h; (3) Step of subjecting the carbonization product to oxidation treatment in an air atmosphere at 600 °C for 6 h to obtain a precursor; (4) Step of putting the precursor into a graphite crucible, transferring the graphite crucible into an Acheson furnace, heating the inside of the Acheson furnace to 3000 °C at a rate of 8 °C / min, and performing high-temperature graphitization treatment for 8 h to obtain a graphite negative electrode material.

[0063] Example 3 The manufacturing method of the negative electrode material in this example is as follows: (1) Step of pulverizing a petroleum coke raw material and shaping it with a shaping device to obtain coke powder with a median diameter of 15 μm after pulverization and shaping; (2) Mix the coke powder and the petroleum resin binder uniformly to obtain a mixture, control the mass ratio of the coke powder to the binder to 100:11, and carbonize the mixture under the condition of 1000 °C for 10 h; (3) Oxidize the carbonized product under the condition of an air atmosphere at 600 °C for 6 h to obtain a precursor; (4) Put the precursor into a graphite crucible, transfer the graphite crucible into an Acheson furnace, heat the inside of the Acheson furnace to 3000 °C at a rate of 6 °C / min and perform high-temperature graphitization treatment for 8 h to obtain a graphite negative electrode material.

[0064] Example 4 The manufacturing method of the negative electrode material of this example is as follows: (1) Crush the petroleum coke raw material and shape it with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping; (2) Mix the coke powder and the phenolic resin binder uniformly to obtain a mixture, control the mass ratio of the coke powder to the binder to 100:9, and carbonize the mixture under the condition of 1000 °C for 10 h; (3) Oxidize the carbonized product under the condition of an air atmosphere at 500 °C for 4 h to obtain a precursor; (4) Put the precursor into a graphite crucible, transfer the graphite crucible into an Acheson furnace, heat the inside of the Acheson furnace to 3000 °C at a rate of 4 °C / min and perform high-temperature graphitization treatment for 8 h to obtain a graphite negative electrode material.

[0065] Example 5 The manufacturing method of the negative electrode material of this example is as follows: (1) Crush the petroleum coke raw material and shape it with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping; (2) Mix the coke powder and the epoxy resin binder uniformly to obtain a mixture, control the mass ratio of the coke powder to the binder to 100:7, and carbonize the mixture under the condition of 1000 °C for 10 h; (3) Oxidize the carbonized product under the condition of an air atmosphere at 500 °C, with the oxidation time being 4 h, to obtain a precursor; (4) Place the precursor into a graphite crucible, transfer the graphite crucible into an Acheson furnace, heat the interior of the Acheson furnace to 3000 °C at a rate of 3 °C / min for 8 h for high-temperature graphitization treatment to obtain a graphite negative electrode material.

[0066] Example 6 The method for manufacturing the negative electrode material of this example is (1) Step of pulverizing a petroleum coke raw material and shaping it with a shaping device to obtain coke powder with a median diameter of 15 μm after pulverization and shaping; (2) Step of uniformly mixing the coke powder and a coumarone resin binder to obtain a mixture, controlling the mass ratio of the coke powder to the binder to 100:5, and subjecting the mixture to carbonization treatment at 800 °C for 10 h; (3) Step of oxidizing the carbonized product under air atmosphere conditions at 400 °C for 4 h to obtain a precursor; (4) Step of placing the precursor into a graphite crucible, transferring the graphite crucible into an Acheson furnace, heating the interior of the Acheson furnace to 2900 °C at a rate of 2 °C / min for 8 h for high-temperature graphitization treatment to obtain a graphite negative electrode material.

[0067] Example 7 The method for manufacturing the negative electrode material of this example is (1) Step of pulverizing a petroleum coke raw material and shaping it with a shaping device to obtain coke powder with a median diameter of 15 μm after pulverization and shaping; (2) Step of uniformly mixing the coke powder and a furan resin binder to obtain a mixture, controlling the mass ratio of the coke powder to the binder to 100:3, and subjecting the mixture to carbonization treatment at 500 °C for 10 h; (3) Step of oxidizing the carbonized product under air atmosphere conditions at 300 °C for 2 h to obtain a precursor; (4) Step of placing the precursor into a graphite crucible, transferring the graphite crucible into an Acheson furnace, heating the interior of the Acheson furnace to 3000 °C at a rate of 7 °C / min for 8 h for high-temperature graphitization treatment to obtain a graphite negative electrode material.

[0068] Example 8 The difference from Example 1 is only that the raw material used in step (1) is needle coke.

[0069] Example 9 The difference from Example 2 is only that the raw material used in step (1) is needle coke.

[0070] Example 10 The difference from Example 3 is only that the raw material used in step (1) is needle coke.

[0071] Example 11 The difference from Example 4 is only that the raw material used in step (1) is needle coke.

[0072] Example 12 The difference from Example 5 is only that the raw material used in step (1) is needle coke.

[0073] Example 13 The difference from Example 6 is only that the raw material used in step (1) is needle coke.

[0074] Example 14 The difference from Example 7 is only that the raw material used in step (1) is needle coke.

[0075] Example 15 The difference from Example 1 is only that the raw material used in step (1) is pitch coke.

[0076] Example 16 The difference from Example 2 is only that the raw material used in step (1) is pitch coke.

[0077] Example 17 The difference from Example 3 is only that the raw material used in step (1) is pitch coke.

[0078] Example 18 The difference from Example 4 is only that the raw material used in step (1) is pitch coke.

[0079] Example 19 The difference from Example 5 is only that the raw material used in step (1) is pitch coke.

[0080] Example 20 The difference from Example 6 is only that the raw material used in step (1) is pitch coke.

[0081] Comparative Example 1 (1) A step of pulverizing a petroleum coke raw material and shaping it with a shaping device to obtain coke powder having a median diameter of 15 μm after pulverization and shaping; (2) A step of uniformly mixing the coke powder and a coal-based pitch binder to obtain a mixture, controlling the mass ratio of the coke powder to the binder to 100:15, and subjecting the mixture to carbonization treatment at 1200 °C for 10 h; (3) A step of subjecting the carbonized product to oxidation treatment in an air atmosphere at 600 °C for 15 h to obtain a precursor; (4) A step of putting the precursor into a graphite crucible, then transferring the graphite crucible into an Acheson furnace, heating the inside of the Acheson furnace to 3000 °C at a rate of 10 °C / min and performing high-temperature graphitization treatment for 8 h to obtain a graphite negative electrode material.

[0082] Comparative Example 2 The green coke raw material of Daqing petroleum coke is pulverized and shaped by a shaping device to obtain pulverized and shaped coke powder. The obtained coke powder having a median diameter of 15 μm is directly put into a graphite crucible, and then the graphite crucible is transferred into an Acheson furnace to obtain a negative electrode material by high-temperature graphitization. The graphitization process has a heating rate of 4 °C / min, a maximum temperature of 2900 °C, and a holding time at the maximum temperature of 8 h.

[0083] Measurement method (1) The measurement method for the particle size of the negative electrode material is The particle size distribution range of the composite negative electrode material is measured by Malvern laser particle sizer.

[0084] (2) The method for measuring the pore volume of the negative electrode material is as follows: The measurements were performed using an ASAP 2460 apparatus manufactured by Micromeritics, Inc., USA, and the pore volume V was calculated within the pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0085] (3) The method for measuring the specific surface area of the negative electrode material is as follows: The measurements were taken using a dynamic rapid specific surface area measuring device JW-DX manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd. The unit is m 2 / g.

[0086] (4) The method for measuring the surface morphology of the negative electrode material is as follows: The purpose of the present study is to observe the surface morphology of the negative electrode material particles using a Hitachi S4800 scanning electron microscope.

[0087] (5) The method for measuring the oil absorption of the negative electrode material is as follows: The oil absorption was measured using an ASAHI S-500 oil absorption meter manufactured by Asahi Research Institute Co., Ltd. The oil absorption O is the amount of linseed oil dropped when the torque due to the change in viscosity characteristics reaches 70% of the maximum torque, and is expressed in mL / 100 g.

[0088] (6) The layer spacing d of the (002) crystal plane of the material by X-ray diffraction 002 The unit is Å, and the deposition thickness Lc of the crystal layer plane and the ratio of the peak intensities of the (004) plane and the (110) plane obtained by X-ray diffraction are I 004 / I 110 It is.

[0089] (7) The method for measuring the powder porosity of the negative electrode material is as follows: The measurements were carried out using a Micromeritics AutoPore V series high performance fully automatic mercury intrusion porosimeter.

[0090] (8) The test method for battery performance is as follows. The negative electrode materials produced in Examples 1 to 20 and Comparative Examples 1 to 2, carboxymethyl cellulose, conductive carbon black, and styrene-butadiene rubber are magnetically stirred in deionized water at a mass ratio of 95:1.5:1.5:2 for 8 h to be uniformly mixed. The obtained slurry is coated on a copper foil and vacuum dried at 60 °C to make a working electrode. Lithium metal is used as the counter electrode and the reference electrode, the separator is Celgard 2325, and the electrolyte is 1 mol·L-1 LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1). The assembly of the CR2016 coin cell pack is completed in a glove box filled with high-purity argon gas.

[0091] The measurement of the initial discharge capacity / initial discharge efficiency is performed with a LAND battery measurement device. The charge and discharge conditions are: standing for 2 h, discharging to 0.005 V at 0.1 C, discharging to 0.001 V at 0.09 C·0.08 C···0.02 C, standing for 15 min, charging to 1.5 V at 0.1 C, and standing for 15 min.

[0092] The rate performance of the button-type half-cell is measured in an environment of 25 ± 2 °C to obtain the charge and discharge specific capacities and Coulomb efficiencies at 0.2 C, 1 C, and 2 C. The charge and discharge conditions for the rate measurement of the button-type half-cell are: (1) discharging to 0.01 V at 0.1 C, constant voltage for 5 h, charging to 1.5 V at 0.1 C; (2) discharging to 0.01 V at 0.2 C, constant voltage to 0.01 C, charging to 1.5 V at 0.2 C; (3) discharging to 0.01 V at 0.2 C, constant voltage to 0.01 C, charging to 1.5 V at 2 C; (4) discharging to 0.01 V at 0.2 C, constant voltage to 0.01 C, charging to 1.5 V at 0.2 C; (5) discharging to 0.01 V at 1 C, constant voltage to 0.01 C, charging to 1.5 V at 0.2 C; (6) discharging to 0.01 V at 2 C.

[0093] For the full cell measurement, the negative electrode materials manufactured in each example were used as the negative electrode active materials. The negative electrode active materials, conductive agents, binders, and dispersants were dissolved in deionized water and mixed at a mass percentage of 95.2:1.5:2:1.3, and the solid content was controlled to 50 wt%. Then it was applied to a copper foil current collector with a thickness of 8 μm and vacuum dried to manufacture a negative electrode sheet. Lithium iron phosphate, polyvinylidene fluoride, and conductive agent carbon black were uniformly mixed with a solvent NMP (N-methylpyrrolidone) at a mass ratio of 95:2:3, and then applied to an aluminum foil with a thickness of 16 μm and vacuum dried to manufacture a positive electrode sheet. The applied positive and negative electrode sheets were processed through steps such as wafering, winding, drying, electrolyte injection, sealing, and chemical synthesis, capacity grading, etc., to manufacture a 554065 type soft pack lithium-ion battery.

[0094] The obtained soft pack battery was subjected to charge and discharge measurement using a LAND battery measurement system manufactured by Wuhan Jinnuo Electronics Co., Ltd. Under normal temperature conditions, charge and discharge were carried out at a current of 1C / 1C, and the charge and discharge voltage was limited to 3.0V - 4.35V. The initial efficiency and 500-cycle capacity retention rate were measured (the compression density of the negative electrode sheet was 1.60 g / cm 3 ).

[0095] For the pressure piece liquid absorption test, a powder sample was prepared into a slurry using a JS-24FS powder pressing machine, dried, polished, and sieved. Then it was pressed onto the electrode sheet at a pressure of 4400 pounds, and after 8 hours of repulsion, the liquid absorption time of the pressed electrode sheet was measured.

[0096] The results of the performance measurement of the negative electrode materials obtained in the above examples are shown in Table 1 below, and the results of the performance measurement of the batteries manufactured with the negative electrode materials are shown in Table 2 below.

[0097]

Table 1

[0098]

Table 2

[0099] As can be seen from the measurement data of Examples 1 to 20, pores are formed inside and / or on the surface of the graphite produced in the examples of the present application, improving the high-rate charging performance of the material. When the negative electrode material manufactured as an electrode is applied to a lithium-ion battery, after injecting the electrolyte, the effective electrochemical reaction space inside the material is sufficient, which is advantageous for improving the rate performance of the negative electrode material.

[0100] By controlling the powder porosity of the negative electrode material to 40% - 58%, the range of 50 ≦ O×V×S ≦ 391 is satisfied, and the powder porosity of the material is controlled, which is advantageous for improving the compression density of the graphite negative electrode plate, advantageous for improving the sufficient infiltration degree between the graphite particles and the electrolyte, and lithium ions are rapidly transmitted inside the graphite through the surface and internal void channels. By reducing the polarization caused by the adsorption of the excessive electrolyte infiltrated on the surface, good performance is ensured.

[0101] For the negative electrode material manufactured in Comparative Example 1, if the pore volume is too large and the oil absorption amount O is too large, O×V×S deviates from the above range. After the voids between the particles are infiltrated, a solid electrolyte film is formed on the surface of the particles, and at the same time, lithium is adsorbed and stored on the surface. Concentration polarization occurs due to the electrolyte cations aggregated on the surface of the graphite particles, and further, if the diffusion of lithium ions is suppressed, an electrochemical reaction cannot occur on its surface naturally, the "effective electrochemical reaction space" of the negative electrode material decreases, and the cycle performance of the material is poor.

[0102] For the negative electrode material manufactured in Comparative Example 2, after the green coke raw material is carbonized in the manufacturing process, it is not oxidized and is directly graphitized, so the artificial graphite pores are not sufficiently abundant, the pore volume V is too small, the specific surface area also decreases, O×V×S deviates from the above range, there is no sufficient diffusion channel for lithium ions, and it is not advantageous for improving the rate performance of the negative electrode material.

[0103] Although the present application has been disclosed by the above preferred embodiments, it does not limit the scope of the claims. Any person skilled in the art can make some possible changes and modifications without departing from the technical idea of the present application. Therefore, the protection scope of the present application should conform to the scope defined in the claims of the present application.

Claims

1. A negative electrode material containing graphite, The graphite has pores inside and / or on the surface thereof, and when the negative electrode material has an oil absorption amount of OmL / 100 g, a pore volume of Vcm ３ / kg, a specific surface area of Sm ２ / g, and a powder porosity of Φ%, 50 ≦ O × V × S ≦ 391 and 40 ≦ Φ ≦ 58, wherein the pore volume is measured using an ASAP 2460 apparatus manufactured by Micromeritics, USA, and is calculated within a pore diameter range of 17 Å to 3000 Å using a BJH Desorption cumulative volume of pores model. The negative electrode material is characterized by this.

2. The negative electrode material according to Claim 1, wherein when the oil absorption amount is OmL / 100 g, 30 ≤ O ≤ 62.

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

012.

4. When the specific surface area is Sm ２ / g, the negative electrode material according to claim 1, characterized in that 0.872 ≦ S ≦ 1.

781.

5. The particle size satisfies the relational expression of 12 μm ≤ D ５０ ≤ 20 μm, and the negative electrode material according to claim 1, characterized in that it satisfies the above relational expression.

6.

7.

6. The negative electrode material according to any one of Claims 1 to 5, further comprising amorphous carbon, wherein the amorphous carbon is present on the surface of the graphite and / or is dispersed between the graphite particles.

7. The negative electrode material according to Claim 6, characterized by satisfying at least one of the following features (1) to (3). (1) The mass ratio of the amorphous carbon in the negative electrode material is 0.1 wt% to 5 wt%; (2) The negative electrode material contains artificial graphite primary particles and / or artificial graphite secondary particles; When the interplanar spacing of the (002) plane is d by X-ray diffraction measurement ００２ it is 3.358 Å ≤ d ００２ ≤ 3.365 Å, and the deposition thickness (Lc) of the crystal layer plane determined by X-ray diffraction measurement is 400 Å to 450 Å. The negative electrode material according to any one of claims 1 to 5, characterized in that (3) The pores include at least one of micropores and mesopores. By X-ray diffraction measurement, under a pressure condition of 9 T, the integrated intensity (I ００４ ) of the peak belonging to the (004) plane of the negative electrode material and the integrated intensity (I １１０ ) of the peak belonging to the (110) plane of the negative electrode material, and the ratio (I ００４ / I １１０ ) satisfy 1.0 ≤ I ００４ / I １１０ ≤ 5.

0. The negative electrode material according to any one of claims 1 to 5, characterized in that.

8.

9.

10. A battery, characterized by containing the negative electrode material according to any one of Claims 1 to 9.

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