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 negative electrode materials, and more specifically, to negative electrode materials and batteries. [Background technology]

[0002] Graphite has several advantages, including high electrical conductivity, a large lithium-ion diffusion coefficient, minimal volume change before and after lithium absorption in its layered structure, high lithium absorption capacity, and a low lithium absorption potential. For these reasons, it is currently the dominant negative electrode material in commercially available lithium-ion batteries.

[0003] Graphite materials also have many drawbacks as anode materials for lithium-ion batteries. The electrolyte absorption performance of materials and electrode pieces in lithium-ion batteries greatly affects the final performance of the battery. Poor anode electrolyte absorption performance limits the reactable area of ​​the graphite anode material, resulting in a lack of electrochemically active sites, which limits the battery's rate performance, causes lithium deposition, and further deteriorates the battery's rate performance and capacity, potentially having a serious impact on battery safety and cycle life. Therefore, good electrolyte absorption performance and an effective reactable area of ​​the material both have a positive effect on the rate performance and capacity 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 rate performance by simply improving a single parameter. Currently, in order to maximize the rate performance of graphite, it is necessary to diligently study the synergistic effects between multiple factors. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In view of this, this application provides an anode material and a battery, and develops an anode material to improve the high-rate charge-discharge performance of the anode material by comprehensively considering the synergistic effects of graphite's oil absorption, pore volume, specific surface area, and powder porosity on the anode material, thereby increasing the number of active sites and diffusion channels for lithium ion release and storage in the anode material. [Means for solving the problem]

[0006] In a first embodiment, the present application provides a negative electrode material comprising graphite, having pores inside and / or on the surface of the graphite, wherein the negative electrode material has an oil absorption capacity of 0 mL / 100 g and a pore volume of V cm 3 The specific surface area is Sm in / kg. 2 When the powder porosity is expressed as Φ% per gram, the following conditions are met: 50≦0×V×S≦391 and 40≦Φ≦58. The pore volume was measured using an ASAP 2460 instrument manufactured by Micromerities, Inc., USA, and calculated within the pore diameter range of 17Å to 3000Å ​​using the BJH Desorption cumulative volume of pores model.

[0007] In some embodiments, the negative electrode material has a coefficient of 30 ≤ 0 ≤ 62 when the oil absorption rate is 0 mL / 100 g.

[0008] In some embodiments, the negative electrode material has a pore volume of V cm 3 When converted to / kg, the relationship is 1.812 ≤ V ≤ 5.012.

[0009] In some embodiments, the negative electrode material has a specific surface area of ​​Sm 2 When expressed as / g, the equation is 0.872 ≤ S ≤ 1.781.

[0010] In some embodiments, the negative electrode material has a particle size of 12 μm ≤ D 50 The relationship ≤20μm is satisfied.

[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 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 has an interlayer spacing d of the crystal plane of the (002) plane by X-ray diffraction measurement, 3.358 Å ≤ d 002 ≤ 3.365 Å, and the deposition thickness Lc of the crystal layer plane obtained by X-ray diffraction is 400 Å to 450 Å. 002

[0016] In some embodiments, when the negative electrode material is under a pressure condition of 9T by X-ray diffraction measurement, 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 / 100g and a pore volume of Vcm 3 ​The specific surface area is Sm in / kg. 2 When the powder porosity is expressed as Φ% in units of / g, 50≦O×V×S≦391 and 40≦Φ≦58. On the other hand, powder porosity is an overall property related to elements such as particle morphology, particle surface state, particle size, and particle size distribution, and is a parameter that greatly affects powder processing performance. Appropriate powder porosity is advantageous for the production of graphite negative electrode pieces with a certain compressive density and ensures good performance. On the other hand, a large pore volume is Li + Increasing the diffusion channels and having a large specific surface area ensures a sufficient electrochemical reaction interface, promotes the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reduces concentration polarization, and is advantageous for improving the capacity and rate performance of the anode material. However, even if the appropriate pore volume and specific surface area are met, there is still room for improvement in the rate performance of the anode material. Lithium ion release and storage require not only diffusion channels and reaction interfaces but also an electrolyte as a medium. Some pores, due to the influence of surface morphology or other factors, do not penetrate the electrolyte and therefore cannot exert their function, and naturally, electrochemical reactions cannot occur on the corresponding surfaces, resulting in an insufficient "effective electrochemical reaction space." Furthermore, the electrolyte penetration capacity is generally expressed by the amount of oil absorbed. This application involves conducting extensive experimental research combining three elements: pore volume, specific surface area, and oil absorption. By controlling the O×V×S of the anode material within the above range and controlling the powder porosity of the material, the anode material is given sufficient reaction space favorable for lithium ion release and storage, which is advantageous for improving the high-rate charge-discharge performance of graphite anode materials. [Brief explanation of the drawing]

[0020] [Figure 1] This is a scanning electron microscope image of the graphite anode material provided in Example 11 of this application. [Figure 2] This is a scanning electron microscope image of the graphite anode material provided in Example 12 of this application. [Modes for carrying out the invention]

[0021] To better explain this application and facilitate understanding of its proposed technology, the application will be described in further detail below. Note that the following embodiments are merely simplified examples of the application and do not indicate or limit the scope of protection. The scope of protection is as defined in the claims.

[0022] A negative electrode material containing graphite, having pores inside and / or on the surface of the graphite, wherein the negative electrode material has an oil absorption capacity of 0 mL / 100 g and a pore volume of V cm². 3 The specific surface area is Sm in / kg. 2 When the powder porosity is expressed as Φ% per gram, the values ​​are 50≦O×V×S≦391 and 40≦Φ≦58. The pore volume was measured using an ASAP 2460 instrument manufactured by Micromerities, Inc., USA, and calculated within the pore diameter range of 17Å to 3000Å ​​using the BJH Desorption cumulative volume of pores model.

[0023] The negative electrode material has pores inside and / or on the surface of the graphite, and has an oil absorption capacity of 0 mL / 100 g and a pore volume of V cm². 3 The specific surface area is Sm in / kg. 2 When the powder porosity is expressed as Φ% in units of / g, the following conditions are met: 50≦O×V×S≦391 and 40≦Φ≦58.

[0024] Generally, particles with a large pore volume are Li +The diffusion channels can be increased, and a large specific surface area ensures a sufficient electrochemical reaction interface, promoting the diffusion of lithium ions at the solid-liquid interface and within the solid phase, reducing concentration polarization, and is advantageous for improving the capacity and rate performance of the anode material. However, lithium ion release and storage require not only diffusion channels and reaction interfaces, but also an electrolyte as a medium. Lithium ions achieve the purpose of lithium storage through lithium ion release and storage by diffusion of lithium ions into the electrolyte. The lithium storage mode involves lithium ions diffusing between the intermediate layers of graphite to achieve the purpose of lithium storage, and also involves lithium storage at the edges and on the surface. Therefore, if only appropriate pore volume and specific surface area are met, there is room for further improvement in the rate performance of the anode material. Here, intercalated lithium storage of graphite is a process in which lithium ions are inserted between graphite layers, which is an intercalation process from higher to lower order. Carbon atoms exposed at the edges of the graphite sheet layers are in an amorphous state, have high energy, and are active sites for lithium ions, enabling lithium storage at the edges. The bonding between carbon atoms and lithium ions on the graphite surface is similar to lithium storage at the edges, thus enabling lithium storage at the surface.Some pores, influenced by surface morphology, pore structure, or other factors, cannot penetrate the electrolyte and therefore cannot exert their effect. However, due to capillary action, the electrolyte first penetrates partly into the voids between graphite particles, and partly into the surface or internal voids of the graphite particles. However, simply controlling the pore volume or specific surface area, which is commonly used in the prior art, only increases the number of open pores. In this study, depending on the diffusion mechanism of lithium ions in the electrolyte and graphite particles, the applicant found that some closed pores exist in the graphite particles, and the closed pores Although it was discovered that carbon atoms capable of lithium ion reactions exist even at the defective ends of graphite, forming lithium storage at the ends, in actual processes, it is difficult to accurately characterize closed pores, and therefore whether the presence of closed pores affects the performance of graphite materials is often ignored. In addition, open pores are distributed on the surface and inside of graphite, and the carbon at the defective ends of open pores can react with lithium ions to realize lithium storage at the ends. Furthermore, electrolyte may permeate into the interior of the pore pathways by capillary action, but the degree of permeation differs depending on the structure and depth of the pore pathways. Moreover, after the interparticle voids are permeated, if there are many active sites on the outer surface of the graphite particles, a solid electrolyte film is formed on the particle surface. However, 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, electrochemical reactions cannot occur on that surface, which corresponds to an insufficient "effective electrochemical reaction space". From the above, it can be concluded that the morphology and distribution of pores (including open and closed pores) have a significant influence on the lithium storage mode of graphite particles and the functions of graphite particles such as surface / internal penetration. Furthermore, the surface and surface-closed pores of graphite particles also have a certain influence on the voids in the graphite particles formed by the deposition mode of the graphite particles, thereby further reflecting the penetration ability and lithium storage mode of the graphite particles.This application involves conducting extensive experimental research combining three elements: pore volume, specific surface area, and oil absorption. The O×V×S of the anode material is controlled within the above range, and the powder porosity Φ of the material is controlled. The characteristics of the voids between graphite particles, the surface morphology of the graphite particles, the open pores and internal void structure of the surface, and the characteristics of the closed pores are thoroughly investigated. This enlarges the lithium ion diffusion channels, allowing lithium ions to be rapidly transmitted through the graphite interior via surface and internal void passages after the graphite particles have sufficiently permeated the electrolyte. Polarization due to adsorption of excess electrolyte permeated to the surface is reduced, thereby achieving sustained capability that further improves the lithium ion transmission rate and the rapid transmission rate of lithium ions. This ensures that the anode material has sufficient reaction space favorable for lithium ion release and storage, which is advantageous for improving the high-rate charge-discharge performance of the graphite anode material.

[0025] In some embodiments, the negative electrode material has an oil absorption capacity of 0 mL / 100 g such that 30 ≤ 0 ≤ 62, and specifically, it may be 30, 35, 40, 45, 50, 55, or 60, but is not limited thereto. Controlling the oil absorption capacity of the material within the above range is advantageous for improving the adsorption and penetration performance of the material to the electrolyte, resulting in better electrochemical performance of the negative electrode material.

[0026] In some embodiments, the negative electrode material has a pore volume of V cm 3 When expressed in units of kg, 1.812 ≤ V ≤ 5.012, and 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 thereto. When pores generate electrochemical reactions inside the electrode, the pores create more lithium ion diffusion channels and electrochemical reaction interfaces in 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 is advantageous for improving the rate performance of the negative electrode material.

[0027] In some embodiments, the negative electrode material has a specific surface area of ​​Sm 2When expressed in units of g, 0.872 ≤ S ≤ 1.781, and 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, or 0.879, and is not limited thereto. As can be understood, if the specific surface area is too large, it is more likely to lead to the formation of a solid electrolyte film, which causes excessive consumption of irreversible lithium salt and reduces the initial efficiency of the battery.

[0028] In some embodiments, the negative electrode material has a powder porosity of Φ%, where 40 ≤ Φ ≤ 58, specifically 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 thereto. As can be understood, controlling the powder porosity of the negative electrode material is advantageous in improving the compressive density of the electrode piece and in improving the degree of sufficient penetration of the graphite particles with the electrolyte. Lithium ions are rapidly transmitted through the graphite interior via surface and internal void passages, reducing polarization due to adsorption of excess electrolyte that has penetrated the surface, and ensuring good performance.

[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 The particle size is 12 μm to 20 μm. Specifically, it may be 12 μm, 13 μm, 14 μm, 15 μm, 18 μm, 19 μm, or 20 μm, and is not limited thereto. Note that in the volume-based cumulative particle size distribution measured using the laser diffraction method, D 50 This indicates the corresponding particle size when the cumulative particle size distribution percentage reaches 50%.

[0031] In some embodiments, the anode material further contains amorphous carbon, with amorphous carbon in a mass percentage of 0.1 wt% to 5 wt% relative to the anode material. Specifically, the mass percentage of amorphous carbon in the anode material may be 0.1 wt%, 0.3 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%, and the presence of amorphous carbon provides lithium ions with more irregular and open diffusion pathways, which is advantageous for improving material rate performance.

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

[0033] In some embodiments, the negative electrode material is determined by X-ray diffraction measurement to have a (002) plane with a layer spacing of d 002 When this is done, 3.358 Å ≤ d 002 The depth is ≤3.365 Å, and the deposition thickness Lc of the crystal layer plane, determined by X-ray diffraction, is 400 Å to 450 Å. Interlayer distance d of the crystal plane 002 Since the values ​​fall within the above range, it can be seen that the graphite particles have a high degree of graphitization, i.e., a high degree of graphitization, and therefore a high product volume.

[0034] In some embodiments, the negative electrode material is determined by X-ray diffraction measurement by the integral intensity I of the peak on the (004) plane of the negative electrode material. 004 and the integrated intensity I of the peak on the (110) plane of the negative electrode material 110 The ratio is 1.0 ≤ I 004 / I 110 ≤5.0, I 004 / I 110 If the conditions are met and within this range, the degree of orientation of the negative electrode material is relatively high and cycle expansion is low.

[0035] In some embodiments, the negative electrode material comprises artificial graphite primary particles and / or artificial graphite secondary particles. In some embodiments, the pores comprise 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, and may specifically be, but is not limited to, 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, or 380 mAh / g.

[0037] This application further provides a method for manufacturing a negative electrode material. S10 involves shaping coke raw materials to obtain coke powder with a median diameter of 10 μm to 20 μm, A mixture containing coke powder and a binder is carbonized at 500°C to 1200°C to obtain a carbonized product, where the mass ratio of coke powder to binder is 100:(3~15) S20, S30 is obtained by oxidizing the carbonized product at 300°C to 600°C for 2 to 6 hours under an oxygen-containing atmosphere, The precursor is graphitized at 2800°C to 3200°C to obtain the negative electrode material, which includes S40.

[0038] The method for manufacturing a negative electrode material provided in this application involves shaping a coke raw material into coke powder, then carbonizing a mixture of the coke powder and a binder. During the carbonization process, impurities, volatile substances, and unstable substances in the coke powder decompose and leach out. The remaining fluid coke raw material and binder harden and form after carbonization. The carbonized product is further oxidized, thereby forming a rich microporous structure on the surface of the material. Finally, the precursor is graphitized. In the case of high-temperature graphitization, some of the microporous structures formed by pre-oxidation continue to expand in diameter and depth as volatile components evaporate in the earlier stage, thereby increasing the lithium ion diffusion channels. Furthermore, the evaporation of impurities and volatilization of organic matter in the raw material leads to a larger pore size. As a large number of pores are formed, and in the later stages at high temperatures, the volatilization of impurities and organic matter is completely simultaneous and ordered according to the arrangement of carbon atoms, some of the pores of the pyrolyzed carbon begin to contract and phenomena such as decay occur, ultimately resulting in some closed pores and the remaining parts forming open pore passages in the developed network structure. As a result, after the graphite particles have sufficiently permeated the electrolyte, lithium ions are rapidly transported through the inside of the graphite via surface and internal void passages, reducing polarization due to the adsorption of excess electrolyte that has permeated the surface. This achieves a sustained ability that further improves the lithium ion transport rate and the rapid transport rate of lithium ions, and the anode material has sufficient reaction space favorable for lithium ion release and storage, which is advantageous for improving the high-rate charge-discharge performance of the graphite anode 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, shaping includes at least one of crushing, spheroidizing, or classifying.

[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, or 20 μm, but it is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable. Controlling the median diameter of the coke powder within the above range through multiple tests is advantageous in achieving both processing performance, capacity, and rate performance.

[0042] 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. As can be understood, a heating rate of the carbonization process within the above range is advantageous for the gradual elution of volatile components in the raw material, pre-forming a pore structure, which, combined with the rapid heating in the subsequent graphitization process, yields a negative electrode material satisfying 50 ≤ 0 × V × S ≤ 391.

[0043] In some embodiments, the carbonization temperature may be, specifically, 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 these values, and other unlisted values ​​within that range are also applicable. As can be understood, having the carbonization temperature within the above range is advantageous for the discharge of substances such as volatile components in coke powder.

[0044] In some embodiments, the heat retention time for the carbonization treatment may be specifically 2h, 3h, 4h, 4.5h, 5h, 5.5h, or 6h, but is not limited to the values ​​listed, and other values ​​within that range that are not listed are also applicable. Preferably, the heat retention time for the carbonization treatment is 3h to 4h.

[0045] In some embodiments, the binder includes at least one of coal-based pitch, petroleum-based pitch, petroleum resin, phenolic resin, epoxy resin, coumarone resin, and furan resin. Specifically, the petroleum-based 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 100:3, 100:5, 100:8, 100:10, 100:12, 100:13, or 100:15, but is not limited to the values ​​listed above, and other unlisted values ​​within that range are also 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, propeller-type stirrers, turbine-type stirrers, flat-blade stirrers, etc., can be used as long as each component in the mixture is sufficiently and uniformly mixed.

[0048] In some embodiments, the stirring speed is 10 r / min to 1000 r / min, and may specifically be, but is not limited to, 10 r / min, 50 r / min, 70 r / min, 100 r / min, 120 r / min, 150 r / min, 200 r / min, 300 r / min, 350 r / min, 400 r / min, 500 r / min, or 1000 r / min. Controlling the stirring speed within the above range is advantageous for mixing each component to form a homogeneous mixture.

[0049] Stirring may be carried out at room temperature or under preheating conditions, and preferably the stirring temperature may be controlled to 25°C to 200°C. As can be understood, appropriate preheating is advantageous for mixing the components to form a homogeneous mixture.

[0050] In some embodiments, the oxidation temperature may be, specifically, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, or 600°C, but is not limited to these values, and other unlisted values ​​within this range are also applicable. As can be understood, by having the oxidation temperature within the above range, it is possible to form an abundant and appropriate amount of microporous structure on the material surface, thereby constructing ideal graphite surface ion pathways.

[0051] In some embodiments, the holding time for the oxidation treatment may be specifically 2h, 3h, 4h, 4.5h, 5h, 5.5h, or 6h, but is not limited to the values ​​listed, and other unlisted values ​​within that range are also applicable. Preferably, the holding time for the oxidation treatment is 3h to 4h.

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

[0053] In some embodiments, the heat retention temperature for the graphitization treatment may be specifically 2800°C, 2850°C, 2900°C, 2950°C, 3000°C, 3100°C, or 3200°C, but is not limited to the values ​​listed above, and other values ​​within that range that are not listed are also applicable.

[0054] In some embodiments, the holding time for the graphitization treatment may be specifically 2h, 2.5h, 3h, 3.5h, 3.8h, 4h, 4.5h, or 5h, but is not limited to the values ​​listed, and other unlisted values ​​within that range are also applicable. Preferably, the holding time for the graphitization treatment is 2h to 3h.

[0055] In some embodiments, the heating rate of the graphitization treatment 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 these values, and other unlisted values ​​within that range are also applicable. A specific heating rate is advantageous for pore formation and control of specific surface area in the interior and / or surface of the graphite material.

[0056] In some embodiments, at least one of the following is performed after the graphitization treatment: crushing, sieving, and demagnetization. Preferably, after the carbonization treatment, crushing, demagnetization, and sieving are performed in that order.

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

[0058] In some embodiments, the sieving method is one of the following: a fixed sieve, a drum screen, a resonant sieve, a roller sieve, a vibrating sieve, and a chain grizzly. The mesh size of the sieve is 100 to 500 meshes, and specifically, the mesh size 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 demagnetizer is 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 ultimately control the content of magnetic material in the negative electrode material to avoid adverse effects of magnetic material on the discharge effect of lithium-ion batteries and the safety of the batteries during use.

[0060] The embodiments of this application will be further described below with reference to several examples. However, the embodiments of this application are not limited to the following specific examples. Appropriate modifications can be made within the scope of protection.

[0061] Example 1 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and coal-based pitch binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:15, and the mixture is carbonized for 10 hours under conditions of 1000°C, (3) The carbonization product is oxidized for 6 hours under an air atmosphere at 600°C to obtain a precursor. (4) The process includes the steps of (4) placing a precursor in a graphite crucible, then moving the graphite crucible into an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 10°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0062] Example 2 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and petroleum-based pitch binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:13, and the mixture is carbonized for 10 hours under conditions of 1000°C, (3) The carbonization product is oxidized for 6 hours under an air atmosphere at 600°C to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 8°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0063] Example 3 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and petroleum resin binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:11, and the mixture is carbonized for 10 hours under conditions of 1000°C, (3) The carbonization product is oxidized for 6 hours under an air atmosphere at 600°C to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 6°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0064] Example 4 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and phenol resin binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:9, and the mixture is carbonized for 10 hours under conditions of 1000°C, (3) The carbonized product is oxidized for 4 hours under an air atmosphere at 500°C to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 4°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0065] Example 5 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and epoxy resin binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:7, and the mixture is carbonized for 10 hours under conditions of 1000°C, (3) The product after carbonization is oxidized under an air atmosphere at 500°C, and the oxidation time is 4 hours, to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, then transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 3°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0066] Example 6 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and coumarone resin binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:5, and the mixture is carbonized for 10 hours under conditions of 800°C, (3) The carbonized product is oxidized for 4 hours under an air atmosphere at 400°C to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, then transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 2900°C at a rate of 2°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0067] Example 7 The method for manufacturing the negative electrode material in this embodiment is: (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and furan resin binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:3, and the mixture is carbonized for 10 hours under conditions of 500°C, (3) The carbonized product is oxidized for 2 hours under an air atmosphere at 300°C to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 7°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

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

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

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

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

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

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

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

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

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

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

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

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

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

[0081] Comparative Example 1 (1) A step of crushing petroleum coke raw materials and shaping them with a shaping device to obtain coke powder with a median diameter of 15 μm after crushing and shaping, (2) A step in which coke powder and coal-based pitch binder are uniformly mixed to obtain a mixture, the mass ratio of coke powder to binder is controlled to 100:15, and the mixture is carbonized for 10 hours under conditions of 1200°C, (3) The carbonization product is oxidized for 15 hours under an air atmosphere at 600°C to obtain a precursor. (4) The process includes the steps of (4) placing the precursor in a graphite crucible, then transferring the graphite crucible to an Acheson furnace, heating the Acheson furnace to 3000°C at a rate of 10°C / min for 8 hours to perform high-temperature graphitization, and obtaining a graphite anode material.

[0082] Comparative Example 2 The raw coke material from Daqing Petroleum Coke is crushed and shaped using a shaping device to obtain crushed and shaped coke powder. The resulting coke powder, with a median diameter of 15 μm, is placed directly into a graphite crucible. The graphite crucible is then moved into an Acheson furnace, where the negative electrode material is obtained by high-temperature graphitization. The graphitization process involves a heating rate of 4°C / min, a maximum temperature of 2900°C, and a holding time of 8 hours at the maximum temperature.

[0083] Measurement method (1) The method for measuring the particle size of the negative electrode material is: The objective is to measure the particle size distribution range of the composite anode material using a Malvern laser particle size analyzer.

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

[0085] (3) The method for measuring the specific surface area of ​​the negative electrode material is: The measurement was performed using the JW-DX dynamic rapid specific surface area analyzer manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd., and the unit is m. 2 The condition is / g.

[0086] (4) The method for measuring the surface morphology of the negative electrode material is: The objective 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 amount of oil absorbed by the negative electrode material is: The oil absorption amount was measured using an ASAHI S-500 oil absorption meter manufactured by Asahi Research Institute Co., Ltd., and the oil absorption amount 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 the unit is mL / 100g.

[0088] (6) X-ray diffraction determines the interlayer spacing d of the crystal planes of the material (002) plane. 002 The following characteristics are characterized, 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, as determined by X-ray diffraction, are I 004 / I 110 That is the case.

[0089] (7) The method for measuring the powder porosity of the negative electrode material is: The measurement will be performed using the AutoPore V series high-performance fully automatic mercury intrusion porosimeter manufactured by Micromeritics.

[0090] (8) The test method for battery performance is as follows: The negative electrode materials produced in Examples 1-20 and Comparative Examples 1-2, carboxymethylcellulose, conductive carbon black, and styrene-butadiene rubber, were uniformly mixed in deionized water for 8 hours by magnetic stirring in a mass ratio of 95:1.5:1.5:2. The resulting slurry was applied to copper foil and vacuum-dried at 60°C to prepare the working electrode. Metallic lithium was used as the counter electrode and reference electrode, the separator was Celgard 2325, and the electrolyte was 1 mol·L-1LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1). The assembly of the CR2016 type coin cell battery pack was completed in a glove box filled with high-purity argon gas.

[0091] The initial discharge capacity / initial discharge efficiency measurement was performed using a LAND battery measuring device. The charge / discharge conditions were as follows: leave for 2 hours, discharge to 0.005V at 0.1C, discharge to 0.001V at 0.09C, 0.08C, ..., 0.02C, leave for 15 minutes, charge to 1.5V at 0.1C, and leave for 15 minutes.

[0092] The button-type half-cell underwent rate performance measurements in an environment of 25±2℃ to obtain charge-discharge ratio capacities and Coulomb efficiencies of 0.2C, 1C, and 2C. The rate measurement charge-discharge conditions for the button-type half-cell are as follows: (1) Discharge to 0.01V at 0.1C, maintain constant voltage for 5 hours, and charge to 1.5V at 0.1C; (2) Discharge to 0.01V at 0.2C, maintain constant voltage to 0.01C, and charge to 1.5V at 0.2C; (3) Discharge to 0.01V at 0.2C, maintain constant voltage to 0.01C, and charge to 1.5V at 2C; (4) Discharge to 0.01V at 0.2C, maintain constant voltage to 0.01C, and charge to 1.5V at 0.2C; (5) Discharge to 0.01V at 1C, maintain constant voltage to 0.01C, and charge to 1.5V at 0.2C; (6) Discharge to 0.01V at 2C.

[0093] For the total battery measurement, the negative electrode material produced in each example was used as the negative electrode active material. The negative electrode active material, conductive agent, binder, and dispersant were dissolved and mixed in deionized water in a mass percentage of 95.2:1.5:2:1.3, controlling the solid content to 50 wt%, and this mixture was applied to an 8 μm thick copper foil current collector and vacuum dried to produce a negative electrode piece. Lithium iron phosphate, polyvinylidene fluoride, and conductive carbon black were uniformly mixed with the solvent NMP (N-methylpyrrolidone) in a mass ratio of 95:2:3, and this mixture was applied to a 16 μm thick aluminum foil and vacuum dried to produce a positive electrode piece. The applied positive and negative electrode pieces were then subjected to processes such as piece formation, winding, drying, liquid injection, sealing, chemical synthesis, and capacity grading to produce a 554065 type soft pack lithium-ion battery.

[0094] The obtained softpack batteries were subjected to charge and discharge measurements using the LAND battery measurement system manufactured by Wuhan Jinnuo Electronics Co., Ltd. Charge and discharge were performed under room temperature conditions and with a 1C / 1C current, and the charge / discharge voltage was limited to 3.0V-4.35V. Initial efficiency and capacity retention rate after 500 cycles were measured (compressed density of negative electrode piece: 1.60 g / cm³). 3 ).

[0095] In the press-form liquid absorption test, powder samples were prepared into a slurry using a JS-24FS powder press, dried, polished, and sieved. The slurry was then pressed into a polarity at a pressure of 4400 pounds, and after 8 hours of rebound, the liquid absorption time of the press-formed polarity was measured.

[0096] The results of performance measurements of the negative electrode material obtained in the above example are shown in Table 1 below, and the results of performance measurements of the battery manufactured with the negative electrode material 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 manufactured in the embodiments of this application, improving the high-rate charging performance of the material. This is because, when the negative electrode material manufactured as an electrode is applied to a lithium-ion battery, after the electrolyte is injected, there is sufficient effective electrochemical reaction space inside the material, 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% to 58%, the range 50 ≤ O × V × S ≤ 391 is satisfied. Controlling the powder porosity of the material is advantageous for improving the compressive density of the graphite negative electrode piece, and for improving the degree of sufficient penetration between the graphite particles and the electrolyte. This ensures that lithium ions are rapidly transmitted through the graphite interior via surface and internal void passages, and that polarization due to the adsorption of excess electrolyte that has penetrated the surface is reduced, thereby ensuring good performance.

[0101] In 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, the voids between particles are infiltrated, a solid electrolyte film is formed on the surface of the particles, 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, the diffusion of lithium ions is suppressed, so naturally, electrochemical reactions cannot occur on the surface, the "effective electrochemical reaction space" of the negative electrode material decreases, and the material's cycle performance is poor.

[0102] In the negative electrode material manufactured in Comparative Example 2, the raw coke raw material was carbonized during the manufacturing process, and then not oxidized, but directly graphitized. As a result, the artificial graphite pores were not sufficiently abundant, the pore volume V was too small, the specific surface area was reduced, O×V×S deviated from the above range, and there were not enough diffusion channels for lithium ions, which is not advantageous for improving the rate performance of the negative electrode material.

[0103] Although this application discloses the above-described preferred embodiments, it does not limit the scope of the claims, and any person skilled in the art may make some possible changes or modifications without departing from the technical concept of this application; therefore, the scope of protection of this application should be limited to the scope defined in the claims.

Claims

1. A negative electrode material containing graphite, The graphite has pores inside and / or on its surface, and the negative electrode material has an oil absorption capacity of 0 mL / 100 g and a pore volume of V cm. ３ / kg, with specific surface area Sm ２ When the powder porosity is given as Φ%, the following conditions apply: 50 ≤ 0 × V × S ≤ 391 and 40 ≤ Φ ≤ 58. The aforementioned pore volume was measured using an ASAP 2460 instrument manufactured by Micromerities, Inc., USA, and calculated within the pore diameter range of 17 Å to 3000 Å using the BJH Desorption Cumulative Volume of Pores model. The aforementioned powder porosity was measured using the AutoPore V series high-performance fully automatic mercury intrusion porosimeter manufactured by Micromeritics. The anode material is characterized by satisfying 30.3 ≤ O ≤ 62.1, 1.897 ≤ V ≤ 5.012, and 0.879 ≤ S ≤ 1.

781.

2. The negative electrode material according to claim 1, characterized in that when the oil absorption amount is 0 mL / 100 g, 31.2 ≤ 0 ≤ 62.

3. Pore ​​volume V cm ３ The negative electrode material according to claim 1, characterized in that when expressed as / kg, 1.945 ≤ V ≤ 5.

012.

4. Specific surface area Sm ２ The negative electrode material according to claim 1, characterized in that when expressed as / g, 0.894 ≤ S ≤ 1.

781.

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

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 dispersed between graphite particles.

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

8. X-ray diffraction measurement determined the interplanar spacing of the (002) plane to be d. ００２ When this is done, 3.358 Å ≤ d ００２ The negative electrode material according to any one of claims 1 to 5, characterized in that the ≤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.

9. 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 it satisfies the above conditions.

10. A battery characterized by comprising the negative electrode material described in any one of claims 1 to 5.

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