Negative electrode material, battery

Abstract

The present invention relates to a negative electrode material and a battery. The negative electrode material contains graphite, has pores inside and / or on the surface of the graphite, and when the negative electrode material has a pore volume of V (cm 3 / kg), a specific surface area of S (m 2 / g), and a tap density of T (g / cc), 2 ≤ V × S / T ≤ 10. 【Solution means】 By constructing the proportional relationship between the specific surface area, pore volume of the negative electrode material, and the tap density of the negative electrode material, the overall distribution status of defects such as internal channels, crystal lattices, and microcracks of graphite particles can be reflected. If within the above limited range, when the negative electrode material of the present invention is manufactured as an electrode and applied to a battery, the defect distribution inside the negative electrode material is uniform. The uniformly distributed defect structure can reduce the expansion that occurs during the charge and discharge process of the graphite negative electrode material, indicating that the electrical performance and processing performance can be improved.

Description

[Technical Field]

[0001] The present invention belongs to the technical field of negative electrode materials, and more specifically, relates to negative electrode materials and batteries. [Background technology]

[0002] Graphite-based anode materials are currently the most mature anode materials due to factors such as their wide availability of sources, abundant storage capacity, relatively stable electrochemical performance, and actual specific capacity density being close to theoretical specific capacity.

[0003] For graphite anode materials, the special layered structure of graphite is important for Li + Since lithium ions can only be inserted from the end face of the material and gradually diffuse into the interior of the particles, the diffusion rate of lithium ions is low, resulting in poor rate performance. Furthermore, lithium deposition is likely to occur on the manufactured negative electrode pieces, leading to safety problems such as battery short circuits and thermal runaway. Therefore, it is necessary to improve the structure of the graphite material to improve the diffusion pathway of lithium ions. Those skilled in the art know that the ideal structure of graphite material consists of six-membered rings made of carbon atoms arranged in a regular pattern. Generally, people desire to influence the pore volume and specific surface area of ​​the graphite negative electrode material by adjusting the size of the voids, thereby affecting the electrochemical performance of the graphite material. A coating layer improves voids and cracks on the graphite surface. However, the applicant argues that in actual application processes, graphite has different defect structures both macroscopically and microscopically, and there are limits to improving the rate performance of the negative electrode material by simply adjusting the size and structure of the voids, which cannot meet people's increasingly high needs for the performance of graphite materials.

[0004] Therefore, now that graphite materials are in a mature stage of development, it is necessary to further research graphite anode materials and maximize the improvement of graphite's rate performance. [Overview of the project] [Problems that the invention aims to solve]

[0005] To overcome the above-mentioned defects, the present invention provides an anode material and battery that can improve the active sites and diffusion pathways for lithium ion release and storage in the anode material, and is advantageous for improving the rate performance and processing performance of the anode material. [Means for solving the problem]

[0006] In a first embodiment, an embodiment of the present invention provides a negative electrode material comprising graphite, wherein the graphite has pores inside and / or on its surface, and the pore volume V (cm³) of the negative electrode material is such that 3 / kg), specific surface area S(m 2 The relationship between (g) and the tap density T (g / cc) satisfies the equation 2 ≤ V × S / T ≤ 10. The aforementioned pore volumes were 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.

[0007] In some embodiments, the negative electrode material has a particle size that satisfies the relationship 0.9 ≤ (D90 - D10) / D50 ≤ 1.8 and 10 μm ≤ D50 ≤ 20 μm.

[0008] In some embodiments, the negative electrode material has a D90 of 25 μm to 36 μm.

[0009] In some embodiments, the negative electrode material has a D10 of 7 μm to 9 μm.

[0010] In some embodiments, the negative electrode material has a pore volume of 2 cm². 3 / kg~6cm 3 It is / kg.

[0011] In some embodiments, the negative electrode material has a specific surface area of ​​1.0 m². 2 / g~2.0m 2 It is / g.

[0012] In some embodiments, the tap density of the negative electrode material is 0.85 g / cc to 1.40 g / cc.

[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, the average pore diameter of the pores is 80 Å to 125 Å.

[0016] In a second aspect, an embodiment of the present invention provides a battery including the negative electrode material described in the first aspect.

Advantages of the Invention

[0017] The technical solution of the present invention has at least the following beneficial effects.

[0018] Those skilled in the art know that the pore volume within a certain range of artificial graphite is Li +It is known that increasing the diffusion pathways and ensuring a specific surface area within a certain range guarantees 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 improving the capacity and rate performance of the negative electrode material. Based on this, the applicant has conducted diligent research and found that satisfying only sufficient pore volume and specific surface area does not necessarily result in the optimal and most stable overall performance of the negative electrode material. Therefore, graphite, as a negative electrode material, needs to provide sufficient diffusion pathways and reaction interfaces for lithium ion release and storage depending on its pores and surface structure to obtain excellent electrochemical performance, and the electrode pieces must also have good workability. This allows the battery to achieve a relatively ideal energy density and maintain a stable structure for the electrode pieces during the cycle process. The applicant recognizes that structures that disrupt the arrangement of other graphite six-membered rings, such as pores, particle surfaces, and crystal planes, all exist in graphite particles as defects in the ideal graphite structure. Therefore, by rationally controlling these defects, it is possible not only to avoid degrading the performance of the graphite material but also to improve the electrical performance of the material to some extent. To obtain the optimal graphite defect structure, it is necessary to precisely adjust the overall structural distribution of defects such as the surface, pores, and crystal lattice of graphite particles. Through analysis, the present invention demonstrates that by combining these three elements—pore volume, specific surface area, and tap density—into a large number of experimental searches for the graphite material, and controlling the V×S / T of the anode material within the range of 2 to 10, the processing performance of the anode material can be guaranteed, while fully utilizing the advantage of improved lithium ion diffusion rate due to the abundant overall structural defects in the material itself. Ultimately, the objective of improving the high-rate charge-discharge performance of the artificial graphite anode material is achieved.

[0019] The present invention will be further described below with reference to the drawings and embodiments. [Brief explanation of the drawing]

[0020] [Figure 1] This is a 1000x magnified SEM image of the negative electrode material manufactured in Example 8 of the present invention. [Modes for carrying out the invention]

[0021] To better understand the technical solution of the present invention, the following will describe the embodiments of the present invention in detail with reference to the accompanying drawings.

[0022] It is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the protection scope of the present invention.

[0023] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "one", "said", and "the" used in the embodiments and claims of the present invention are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0024] It should be understood that the term "and / or" used in this specification only describes the relationship of related objects and indicates that three types of relationships are possible. For example, A and / or B can indicate three situations: A exists alone, A and B exist simultaneously, and B exists alone. Also, the symbol " / " in this specification generally indicates that the related objects before and after are in an "or" relationship.

[0025] For the graphite negative electrode material, the graphite material needs to be prepared into a slurry during use and then coated on a copper foil current collector for use. In order to maintain a good electrode structure during the long cycle process, the graphite negative electrode material is required to have good processing performance. At the same time, since the lithium ions during the process of lithium release and absorption by graphite can only enter the graphite interlayer from the end face, the diffusion path is limited, the diffusion of lithium ions at the solid-liquid interface and within the solid phase is restricted, and the performance of high-rate charge and discharge of graphite is further restricted. Generally, all artificial graphite has a certain number of pore structures. On the one hand, the presence of pores increases the diffusion path of Li + inside the graphite material, and Li +Reducing the diffusion resistance can effectively improve the rate performance of the material. On the other hand, if there are too many pores, the specific surface area of ​​the material becomes too large, which not only reduces the volume density of graphite but also makes the surface of the graphite particles rougher due to the voids present on the surface, resulting in poor flowability of the graphite particles. Ultimately, this reduces the tap density of the graphite material and further deteriorates the electrochemical performance of the product, such as processing performance, initial efficiency, and cycle efficiency. In fact, simply improving the pore structure alone is not enough to optimize the overall performance of the graphite anode material, and there is still considerable room for improvement. Researchers have only studied the effect of a single element on the performance of graphite materials and have not deeply studied the synergistic effects between multiple elements in order to maximize the improvement of the rate performance of graphite.

[0026] Therefore, at this mature stage in the development of graphite materials, improving a single parameter will not be enough to meet the market need for low-cost, high-performance graphite materials. It is necessary to study the synergistic mechanisms of various factors and develop graphite anode materials that meet market needs.

[0027] The following describes in more detail the preparation process developed by the applicant and the related products, using the process as an example.

[0028] An embodiment of the present invention provides a method for manufacturing a negative electrode material, comprising the following steps. S10: A carbon-based raw material, a pore-forming agent, and a binder are mixed to obtain a first precursor, where the particle size of the pore-forming agent satisfies 0.5 ≤ (D90 - D10) / D50 ≤ 0.8 and 5 nm ≤ D50 ≤ 8 nm, and the mass ratio of the carbon-based raw material, pore-forming agent, and binder is (70-94):(1-10):(5-20). S20: The first precursor is subjected to a first heat treatment to carbonize it and obtain the second precursor. S30: The second precursor is subjected to a second heat treatment to graphitize it and obtain a negative electrode material. Hereinafter, the second heat treatment involves first raising the temperature to 1600°C to 1800°C at a heating rate of 2°C / min to 5°C / min, then raising the temperature to 3000°C to 3200°C at a heating rate of 2°C / min to 8°C / min, maintaining the temperature for 6 to 10 hours, then lowering the temperature to 800°C at a cooling rate of 0.1°C / min to 0.5°C / min, and finally lowering the temperature to room temperature at a cooling rate of 2°C / min to 4°C / min.

[0029] In the above-described technical proposal, the present invention mixes an appropriate proportion of carbon-based raw materials, a pore-forming agent with a specific particle size and particle size distribution, and a binder, then performs carbonization and graphitization. By controlling the heating rate, cooling rate, and graphitization holding time during the carbonization and graphitization process, the pore-forming agent is uniformly and rapidly released, creating more lithium ion diffusion pathways within the graphite material. This achieves the objective of adjusting and controlling the defect structure and surface morphology of the graphite anode material, optimizing the tap density, voids, and specific surface area parameters of the graphite anode material, and ultimately effectively improving the processing performance and rate performance of the graphite anode material. The process method is simple, production costs are low, and the resulting graphite anode material has characteristics such as high tap density, good processing performance, and excellent rate performance, meeting the user needs for power batteries and energy storage.

[0030] The manufacturing method of the present invention will be described in detail below.

[0031] Step S10: A carbon-based raw material, a pore-forming agent, and a binder are mixed to obtain a first precursor, where the particle size of the pore-forming agent satisfies 0.5 ≤ (D90 - D10) / D50 ≤ 0.8 and 5 nm ≤ D50 ≤ 8 nm, and the mass ratio of the carbon-based raw material, pore-forming agent, and binder is (70-94):(1-10):(5-20).

[0032] In some embodiments, in order to obtain a carbon-based raw material of a specific particle size, it is necessary to perform a shaping treatment on the carbon-based raw material before mixing it with a pore-forming agent and a binder.

[0033] In some embodiments, the particle size of the carbon-based raw material after shaping is 10 μm to 25 μm, specifically 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, or 25 μm, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0034] In some embodiments, the carbon-based raw material includes at least one of petroleum coke, needle coke, pitch coke, and isotropic coke.

[0035] In some embodiments, the pore-forming agent comprises at least one of silicon dioxide and silicon carbide.

[0036] In some embodiments, the pore-forming agent satisfies the following particle size: 0.5 ≤ (D90-D10) / D50 ≤ 0.8 and 5 nm ≤ D50 ≤ 8 nm. Specifically, the value of (D90-D10) / D50 may be 0.5, 0.6, 0.7, or 0.8, and of course, it may be any other value within the above range, and the present invention is not limited thereto. The pore-forming agent may have a median diameter D50 of 5 nm, 6 nm, 7 nm, or 8 nm, and of course, it may be any other value within the above range, and the present invention is not limited thereto. Within the above specific range, it has been shown that having a small and concentrated particle size of the pore-forming agent is advantageous for the pore-forming agent to escape uniformly and rapidly from the carbon-based raw material during the graphitization process, forming a uniform and controllable pore defect structure in the final graphite anode material to serve as a pathway for lithium ion diffusion.

[0037] 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.

[0038] In some embodiments, the mass ratio of the carbon-based raw material, the pore-forming agent, and the binder is (70-94):(1-10):(5-20), and specifically, the mass ratio of the carbon-based raw material, the pore-forming agent, and the binder may be 70:10:20, 75:8:17, 80:5:15, 85:3:12, or 94:1:5, and of course, it may be other values ​​within the above range, and the present invention is not limited thereto. If the amount of pore-forming agent added exceeds the limiting range of the present invention, it tends to increase the specific surface area of ​​the material, decrease the tap density of the graphite material, and further worsen the electrochemical performance of the product, such as processing performance, initial efficiency, and cycle. If the amount of pore-forming agent added is less than the limiting range of the present invention, the formed void structure is too small, failing to achieve the objective of creating more lithium ion diffusion passages and electrochemical reaction interfaces for the anode material. Furthermore, in the graphitization process, the pore-forming agent acts as an impurity in the carbon raw material, affecting the crystal structure of the polycrystalline graphite, and potentially affecting the crystal lattice and crystal plane defect distribution of the graphite material. To understand this, when the amount of binder added is less than the limiting range of the present invention (mass ratio of carbon-based raw material to binder greater than 94:5), the resulting artificial graphite mainly consists of primary particles, and when the proportion of binder is high (mass ratio of carbon-based raw material to binder 85:12 or less), the resulting artificial graphite mainly consists of secondary particles.

[0039] S20: The first precursor is subjected to a first heat treatment to carbonize it and obtain the second precursor.

[0040] In some embodiments, the temperature of the first heat treatment is 800°C to 1100°C, and specifically, the temperature of the first heat treatment may be, for example, 800°C, 900°C, 1000°C, or 1100°C, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0041] In some embodiments, the holding time for the first heat treatment is 4 to 10 hours, specifically 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0042] In some embodiments, the heating rate of the first heat treatment is 2°C / min to 10°C / min, and may specifically be 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, and of course may be other values ​​within the above range, and the present invention is not limited thereto.

[0043] In some embodiments, the cooling rate after the first heat treatment is 1°C / min to 5°C / min, and may specifically be 1°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min, and of course may be other values ​​within the above range, and the present invention is not limited thereto.

[0044] In some embodiments, the first heat treatment is performed in a protective atmosphere, which includes at least one of nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0045] In the first heat treatment process, the carbon-based raw material in the first precursor undergoes pyrolysis shrinkage and is converted into a carbon solid with a microcrystalline arrangement. Organic molecules and impurities present in the carbon-based raw material, pore-forming agent, and binder are gradually released during the heating process to form a pore structure. In the first precursor of the pore-forming agent with a specific particle size, the temperature, time, and heating rate of the first heat treatment are controlled to form pores and surfaces with a specific structural distribution in the carbon solid, creating uniformly distributed structural defects favorable for lithium ion diffusion, and providing an excellent reaction raw material for the subsequent second heat treatment graphitization.

[0046] S30: The second precursor is subjected to a second heat treatment to graphitize it. Here, the second heat treatment involves raising the temperature of the second precursor to 1600°C to 1800°C over 6 to 10 hours at a heating rate of 2°C / min to 5°C / min, raising the temperature to 3000°C to 3200°C over 4 to 6 hours at a heating rate of 2°C / min to 8°C / min, maintaining the temperature for 6 to 10 hours, then lowering the temperature to 800°C over 150 to 200 hours at a cooling rate of 0.1°C / min to 0.5°C / min, and then lowering the temperature to room temperature over 4 to 6 hours at a cooling rate of 2°C / min to 4°C / min to obtain the negative electrode material.

[0047] Controlling the heating rate, cooling rate, and holding time of the second heat treatment within the above range is advantageous because it allows the second precursor to uniformly and rapidly decompose and release the porosity agent from the material during the graphitization process, creating many lithium ion diffusion pathways within the graphite material. Furthermore, since the graphite crystal structure is polycrystalline and crystal plane defects exist between the grain boundaries, the above control can also maintain a highly regular crystal structure, achieving the objective of adjusting and controlling the graphite anode structure and morphology, optimizing the tap density, voids, and specific surface area parameters of the product, and improving the processing performance and rate performance of the anode material.

[0048] As will be apparent to those skilled in the art, the battery manufacturing methods described above are merely examples. Other methods commonly used in the art can be employed without departing from the scope of this description.

[0049] The present invention provides a negative electrode material comprising graphite, having pores inside and / or on the surface of the graphite, wherein the pore volume V (cm3 / kg), specific surface area S (m2 / g), and tap density T (g / cc) of the negative electrode material satisfy 2 ≤ V × S / T ≤ 10. Pore ​​volume was measured using an ASAP 2460 instrument manufactured by Micromeristics, Inc., USA, and calculated within the pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0050] In the above proposed technology, the anode material according to the present invention is formed by adding a binder and a pore-forming agent of a specific particle size to a carbon-based raw material, and then performing production processing by a heating process of carbidization and graphitization at specific heating and cooling rates. The pore-forming agent forms specific pores inside and / or on the surface of the graphite, and the distribution of these pores can reflect the defect structure distribution in polycrystalline graphite to some extent. Since a specific pore structure distribution exists inside the material after graphitization, these pore structure defects are mainly caused by phenomena such as the volatilization of organic matter, the pore-forming agent, shrinkage due to thermal decomposition of the carbon source, and non-uniformity of internal stress due to differences in polycrystalline orientation. Ultimately, by causing different pore forms such as closed holes, open holes, interlayer microcracks, and channels to appear inside / on the graphite, precise control of defects inside and / or on the graphite is achieved, and the material pore volume, specific surface area, and tap density meet the ideal adjustment and control design requirements. Here, uniformly distributed pore defects are formed inside and / or on the surface of the graphite, and these uniformly distributed voids can reduce the expansion that occurs in the graphite anode material during the charge-discharge process. Furthermore, the pore defects improve the lithium storage capacity of the anode material by providing additional lithium storage space, and also increase the specific surface area. When the anode material is manufactured as an electrode and applied to a battery, after the electrolyte is injected, the pores inside the artificial graphite particles are filled with the electrolyte, and during charge-discharge, an electrochemical reaction occurs inside the electrode. The stress on the surface of the graphite particles and the pore defects inside and on the exposed outer surface of the graphite particles is uneven, and the stress on the defective areas is uneven. This creates more lithium ion diffusion passages and electrochemical reaction interfaces in the anode material with appropriate tapping, 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. In addition, the anode material of the present invention has good processing performance and can prevent the detachment of the graphite sheet layer during the cycle process of the graphite anode material, which is advantageous for improving the material's cycle performance.

[0051] Generally, a certain range of pore volume in graphite can increase the diffusion pathways for Li ions, and a certain range of specific surface area can ensure a sufficient electrochemical reaction interface. This 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, the disruption of the void distribution and increase in specific surface area of ​​the material limit the improvement of the rate performance and processing performance of the graphite anode material. Therefore, simply improving the pore structure does not allow the graphite anode material to have the optimal and most stable electrochemical performance. Accordingly, the present invention is advantageous in obtaining an anode material with superior overall performance, such as rate performance and cycle performance, while maintaining good processing performance, by controlling the V×S / T of the graphite anode material within the above range. In the present invention, the range of the value of V × S / T is 2 to 10, and specifically it may be 2, 2.5, 3, 3.6, 4, 4.5, 5, 5.3, 6, 6.7, 7, 7.3, 8, 8.4, 9, 9.5, or 10, and of course it may be any other value within the above range, and the present invention is not limited thereto. In the above formula, V is the pore volume of the graphite material, S is the specific surface area of ​​the graphite material, and T is the tap density of the graphite material. A larger V indicates that the pore structure of the graphite particles is richer, and the specific surface area S increases within a certain range, but the cycle performance deteriorates as the initial efficiency of the graphite anode material decreases, and the smaller T is, the worse the processing performance in the process of manufacturing slurry and electrodes using graphite as an anode material. In other words, it is not possible to improve the rate performance and processing performance of the graphite anode material with a single element, and the improvement of the rate performance of the material is limited by controlling a single element.Therefore, the present invention can combine both of the above elements using a parameter that combines V × S / T, and although the voids formed by the closed holes cannot be accurately measured, it is recognized that it can provide abundant pathways for lithium ions. Due to the action of defect stress, microcracks are likely to occur around the closed voids and at the grain boundaries, both of which are considered to be potential fracture sources within the material. When it is fractured, graphite particles are preferentially struck and fractured at locations where the defect stress is large and there are microcracks, and at this time the internal closed portions are opened and exposed to the surface, or fine pores are opened inside and deep fine pores are formed. After the pores are exposed and the outer surface of the graphite particles is formed, the material surface is ultimately roughened, and at the same time, grain boundary defects of some polycrystalline graphite may also be fractured and exposed due to stress. Since the surface is relatively smooth, the combined state of these two types of surface defects affects the fluidity of the graphite particles. Ultimately, the applicant found that the overall structural state of graphite internal / surface defects can be represented to some extent by utilizing the relationship between tap, specific table and pore volume, and that by controlling V×S / T to 2~10, relatively excellent rate performance and processing performance can be obtained simultaneously, preferably in the range of V×S / T values ​​of 2.5~8.4.

[0052] In some embodiments, the negative electrode material has a particle size that satisfies the relationship 0.9 ≤ (D90 - D10) / D50 ≤ 1.8 and 10 μm ≤ D50 ≤ 20 μm. In the above equation, D90 is the particle size at which the cumulative distribution of material particles accounts for 90%, D10 is the particle size at which the cumulative distribution of material particles accounts for 10%, and D50 is the particle size at which the cumulative distribution of material particles accounts for 50%, and is also called the median diameter.

[0053] An ideal battery material needs to have a narrow particle size distribution. As research has shown, too much fine powder causes highly active battery materials to continuously consume electrolyte during cycling, leading to a deterioration in capacity retention. Larger particles with greater expansion are more likely to cause particle pulverization during cycling, leading to a sustained thickening of the SEI. Therefore, narrowing the particle size distribution can improve the cycling performance of the material. In the anode material of the present invention, the fact that (D90-D10) / D50 is between 0.9 and 1.8, and D50 is between 10 μm and 20 μm, indicates that the particle size span of the anode material is small, i.e., the anode material has a uniform particle size distribution. This allows the material to avoid the above problems, and furthermore, it has a high bulk density, making it easier to improve the electrochemical performance of the anode material. Specifically, the value of (D90-D10) / D50 may be 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8, and of course, it may be any other value within the above range, and the present invention is not limited thereto. If (D90-D10) / D50 is less than 0.9, it indicates that the particle size distribution of the negative electrode material is too narrow, which is unfavorable for coating the negative electrode material for manufacturing electrode pieces, resulting in poor processing performance. If (D90-D10) / D50 exceeds 1.8, it indicates that there is a large amount of fine powder in the negative electrode material, which is unfavorable for improving the cycle performance of the negative electrode material.

[0054] In some embodiments, the median diameter D50 of the negative electrode material may be specifically 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0055] In some embodiments, the negative electrode material has a D90 of 25 μm to 36 μm, specifically 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, or 36 μm, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0056] In some embodiments, the negative electrode material has a D10 of 7 μm to 9 μm, specifically 7 μm, 7.5 μm, 8 μm, 8.5 μm, or 9 μm, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0057] In some embodiments, the negative electrode material has a pore volume of 2 cm². 3 / kg~6cm 3 The value is / kg, and specifically, the negative electrode material has a pore volume of 2cm³. 3 / kg, 3cm 3 / kg, 4cm 3 / kg, 5cm 3 / kg or 6cm 3 The values ​​may be such as / kg, and other values ​​within the above range are also possible, and the present invention is not limited thereto. Within the above range, it is shown that the graphite anode material has an appropriate pore structure and can effectively provide sufficient passages for lithium ion diffusion, which is advantageous for improving the rate performance of the anode material.

[0058] In some embodiments, the negative electrode material has a specific surface area of ​​1.0 m². 2 / g~2.0m 2 The value is / g, and specifically, the negative electrode material has a specific surface area of ​​1.0 m². 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g or 2.0m 2 The value may be / g or other values, and naturally, other values ​​within the above range are also acceptable, and the present invention is not limited thereto. Within the above range, the negative electrode material has abundant surface active sites, which is also advantageous for improving the rate performance of the material.

[0059] In some embodiments, the negative electrode material has a tap density of 0.85 g / cc to 1.40 g / cc, specifically, the negative electrode material may have a tap density of 0.85 g / cc, 1.0 g / cc, 1.10 g / cc, 1.20 g / cc, 1.30 g / cc, or 1.40 g / cc, and of course, it may be other values ​​within the above range, and the present invention is not limited thereto. Within the above range, it is shown that the negative electrode material has good processability, reduces the difficulty of coating the electrode pieces and manufacturing the battery, maintains the structural stability of the electrode pieces during the cycling process, and is advantageous in improving the material's cycling performance and the battery's energy density.

[0060] In some embodiments, the negative electrode material has a specific capacity of 330 mAh / g to 370 mAh / g. Specifically, the negative electrode material may have a specific capacity of 330 mAh / g, 340 mAh / g, 350 mAh / g, 360 mAh / g, or 370 mAh / g, and of course, it may be any other value within the above range, and the present invention is not limited thereto.

[0061] In some embodiments, the pores include at least one of micropores and mesopores.

[0062] In some embodiments, the pores have an average pore diameter of 80 Å to 125 Å, specifically 80 Å, 90 Å, 100 Å, 110 Å, 120 Å, or 150 Å, and of course, other values ​​within the above range are also possible, and the present invention is not limited thereto.

[0063] Embodiments of the present invention further provide a battery containing the above-mentioned negative electrode material.

[0064] As will be apparent to those skilled in the art, the battery manufacturing methods described above are merely examples. Within the scope of the present invention, other methods commonly used in the art may be employed, and other types of batteries, such as sodium-ion batteries and potassium-ion batteries, may be manufactured and measured.

[0065] The embodiments of the present invention will be further described below with reference to several examples. However, the present invention is not limited to the following specific embodiments. It may be modified as appropriate without changing the scope of the main claims.

[0066] Example 1 (1) The median diameter of the material powder after crushing the petroleum coke raw materials is 20 μm or less. (2) The powder obtained in step (1), the nanosilica pore-forming agent, and the coal-based pitch binder are uniformly mixed to obtain the first precursor, where the mass ratio of petroleum coke, pore-forming agent, and binder is controlled to 70:10:20, and the pore-forming agent has a D50 of 8 nm, with (D90-D10) / D50 = 0.5. (3) The first precursor obtained in step (2) is carbonized under heating conditions of 1000°C to obtain the second precursor. (4) The second precursor obtained in step (3) is subjected to high-temperature graphitization under conditions of 3000°C, and the heating and cooling process curve is controlled as follows: heating is increased to 1800°C in 10 hours (heating rate of 3°C / min), heating is increased to 3000°C in 6 hours (heating rate of 3.3°C / min), the temperature is maintained for 6 hours, and after the maintenance, the temperature is cooled to 800°C in 150 hours (cooling rate of 0.3°C / min), and then the temperature is cooled to room temperature in 6 hours (cooling rate of 2.2°C / min). (5) The material obtained in step (4) is crushed, sieved, and mixed to obtain a graphite anode material with a D50 of 10 μm to 20 μm.

[0067] The above-mentioned anode material contains primary particle artificial graphite and secondary particle artificial graphite, with secondary particle artificial graphite being the main component. The pore volume, tap density, and specific surface area values ​​of the anode material are shown in Table 1.

[0068] Example 2 The difference from Example 1 is that the heating and cooling curve used in step (4) is as follows: the temperature is raised to 1800°C in 8 hours (heating rate of 3.8°C / min), then raised to 3000°C in 5 hours (heating rate of 4°C / min), maintained for 8 hours, then cooled to 800°C in 170 hours (cooling rate of 0.2°C / min), and then cooled to room temperature in 5 hours (cooling rate of 2.7°C / min). A graphite anode material is obtained.

[0069] In this embodiment, the negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The pore volume, tap density, and specific surface area values ​​of the negative electrode material are shown in Table 1.

[0070] Example 3 The difference from Example 1 is that the heating and cooling curve used in step (4) is as follows: the temperature is raised to 1800°C in 6 hours (heating rate of 5°C / min), then raised to 3200°C in 5 hours (heating rate of 4.7°C / min), maintained for 10 hours, then cooled to 800°C in 190 hours (cooling rate of 0.2°C / min), and then cooled to room temperature in 4 hours (cooling rate of 3.3°C / min). A graphite anode material is obtained.

[0071] In this embodiment, the negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The pore volume, tap density, and specific surface area values ​​of the negative electrode material are shown in Table 1.

[0072] Example 4 The difference from Example 1 is that the heating and cooling curve used in step (4) is as follows: the temperature is raised to 1600°C in 6 hours (heating rate of 4.4°C / min), then raised to 3200°C in 4 hours (heating rate of 6.7°C / min), maintained for 10 hours, then cooled to 800°C in 200 hours (cooling rate of 0.2°C / min), and then cooled to room temperature in 4 hours (cooling rate of 3.3°C / min). A graphite anode material is obtained.

[0073] In this embodiment, the negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The pore volume, tap density, and specific surface area values ​​of the negative electrode material are shown in Table 1.

[0074] Example 5 The difference from Example 1 is that the mass ratio of petroleum coke, pore-forming agent, and binder in step (2) is 80:5:15.

[0075] In this embodiment, the negative electrode material includes primary artificial graphite particles and secondary artificial graphite particles, mainly consisting of secondary artificial graphite particles. The pore volume, tap density, and specific surface area values ​​of the negative electrode material are shown in Table 1.

[0076] Example 6 The difference from Example 1 is that the mass ratio of petroleum coke, pore-forming agent, and binder in step (2) is 85:3:12.

[0077] In this embodiment, the negative electrode material includes primary artificial graphite particles and secondary artificial graphite particles, mainly consisting of secondary artificial graphite particles. The pore volume, tap density, and specific surface area values ​​of the negative electrode material are shown in Table 1.

[0078] Example 7 The difference from Example 1 is that the mass ratio of petroleum coke, pore-forming agent, and binder in step (2) is 90:2:8.

[0079] In this embodiment, the negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The pore volume, tap density, and specific surface area values ​​of the negative electrode material are shown in Table 1.

[0080] Example 8 The difference from Example 1 is that the mass ratio of petroleum coke, pore-forming agent, and binder in step (2) is 94:1:5.

[0081] In this embodiment, the anode material includes primary particle artificial graphite and secondary particle artificial graphite. As shown in Figure 1, this is an SEM view of the anode material manufactured for this embodiment. As can be seen from Figure 1, the artificial graphite has small particle sizes and mainly consists of primary particle artificial graphite. Table 1 shows the values ​​for pore volume, tap density, and specific surface area of ​​the anode material.

[0082] Example 9 The difference from Example 1 is that the pore-forming agent in step (2) has a D50 of 5 nm, and (D90-D10) / D50 = 0.7.

[0083] The above-mentioned anode material contains primary particle artificial graphite and secondary particle artificial graphite, with secondary particle artificial graphite being the main component. The pore volume, tap density, and specific surface area values ​​of the anode material are shown in Table 1.

[0084] Example 10 The difference from Example 1 is that the pore-forming agent in step (2) has a D50 of 6 nm, and (D90-D10) / D50 = 0.5.

[0085] The above-mentioned anode material contains primary particle artificial graphite and secondary particle artificial graphite, with secondary particle artificial graphite being the main component. The pore volume, tap density, and specific surface area values ​​of the anode material are shown in Table 1.

[0086] Example 11 The difference from Example 1 is that the carbonization temperature in step (3) is 800°C.

[0087] The above-mentioned anode material contains primary particle artificial graphite and secondary particle artificial graphite, with secondary particle artificial graphite being the main component. The pore volume, tap density, and specific surface area values ​​of the anode material are shown in Table 1.

[0088] Example 12 The difference from Example 1 is that the carbonization temperature in step (3) is 1100°C.

[0089] The above-mentioned anode material contains primary particle artificial graphite and secondary particle artificial graphite, with secondary particle artificial graphite being the main component. The pore volume, tap density, and specific surface area values ​​of the anode material are shown in Table 1.

[0090] Comparative Example 1 The difference from Example 1 is that the mass ratio of petroleum coke, pore-forming agent, and binder in step (2) is 65:23:12.

[0091] Comparative Example 2 The difference from Example 1 is that no pore-forming agent is added in step (2), and the mass ratio of petroleum coke to adhesive is 94:6.

[0092] Comparative Example 3 The difference from Example 1 is that the pore-forming agent in step (2) has a particle size D50 = 15 nm, and (D90 - D10) / D50 = 1.5.

[0093] Comparative Example 4 The difference from Example 1 is that the pore-forming agent in step (2) has a D50 of 3 nm, and (D90-D10) / D50 = 0.4.

[0094] Comparative Example 5 The difference from Example 1 is that in step (4), the second precursor obtained in step (3) is graphitized at high temperature under conditions of 3000°C, and the heating and cooling process curve is controlled as follows: heating is increased to 1800°C in 17 hours (heating rate of 1.76°C / min), heating is increased to 3000°C in 6 hours (heating rate of 3.3°C / min), the temperature is maintained for 6 hours, and after the temperature is maintained, it is cooled to room temperature (cooling rate of 2.2°C / min).

[0095] Comparative Example 6 The difference from Comparative Example 1 is that in step (4), the second precursor obtained in step (3) is graphitized at high temperature under conditions of 3000°C, and the heating and cooling process curve is controlled as follows: the temperature is raised to 3000°C in 17 hours (heating rate of 3°C / min), the temperature is maintained for 6 hours, and after the maintenance, the temperature is cooled to room temperature (cooling rate of 3°C / min).

[0096] Performance measurement (1) Method for measuring the median diameter of the negative electrode material: The particle size distribution range of the negative electrode material is measured using a Malvern laser particle size analyzer.

[0097] (2) Method for measuring the pore volume and average pore diameter of the negative electrode material: Measurements were performed using an ASAP2460 instrument manufactured by Micromeristics, Inc., USA. Pore volume V and average pore diameter were calculated within the pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

[0098] (3) Method for measuring the specific surface area of ​​the negative electrode material: Measurements are taken using the JW-DX dynamic specific surface area rapid measuring instrument manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd. The unit is m. 2 The condition is / g.

[0099] (4) Method for measuring the tap density of the negative electrode material: The tap density T is measured using a Quanta tap density analyzer Dual Autotap manufactured by Anton Paar (Shanghai) Trading Co., Ltd. The tap density T is the value after 222 vibrations, and the unit is g / cc.

[0100] (5) The surface morphology of the negative electrode material is observed using a Hitachi S4800 scanning electron microscope.

[0101] (6) Test method for battery performance: Samples prepared in Examples 1-20 and Comparative Examples 1-2: Conductive adhesive: (CMC+SP):SBR = 95:1.5:1.5:2 in mass ratio, magnetically stirred in deionized water for 8 hours to ensure uniform mixing. The slurry obtained from the mixing was applied to copper foil and vacuum-dried at 60°C to form 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 button cell was completed in a glove box filled with high-purity argon gas, and four batteries were produced from each sample set.

[0102] The initial discharge capacity / initial discharge efficiency test was performed using a LAND battery tester. The charge / discharge conditions were as follows: leave for 2 hours, discharge from 0.1C to 0.005V, then to 0.09C, 0.08C, ..., 0.02C to 0.001V, leave for 15 minutes, charge to 1.5V at 0.1C, and leave for 15 minutes.

[0103] The 20-cycle full-charge expansion test was performed using a molded battery, and the surface density of the graphite negative electrode was 70 g / m². 2 The compacted density is 1.6 g / cc, the corresponding cathode is LCO, and the areal density is 166 g / m². 2 The compact density is 3.5-3.7 g / cc. The cycle test conditions are as follows: the first cycle is charged and discharged once at a rate of 0.1C, the second cycle is charged and discharged once at a rate of 0.2C, and from the third to the twentieth cycle, it is charged and discharged at a rate of 0.5C. After that, the thickness change data of the electrode pieces collected by the sensor during the cycle process is correlated with the cycle data collected by the electrochemical test cabinet to obtain the expansion value of the fully charged state after 20 cycles.

[0104] [Table 1]

[0105] [Table 2]

[0106] As shown in Tables 1 and 2, the present invention can reflect the overall distribution of defects such as channels, crystal lattices, and interlayer microcracks within graphite particles by establishing a proportional relationship between the specific surface area, pore volume, and tap density of the negative electrode material. Within the limited range of 2 ≤ V × S / T ≤ 10, when the negative electrode material of the present invention is manufactured as an electrode and applied to a battery, the distribution of pore defects within the negative electrode material is uniform. Uniformly distributed pore defects can reduce the expansion that occurs during the charge-discharge process of the graphite negative electrode material. Furthermore, the pores act as additional lithium storage space, improving the lithium storage capacity of the negative electrode material and causing an increase in specific surface area within a certain range. When the negative electrode material is manufactured as an electrode and applied to a battery, after the electrolyte is injected, the pores inside the artificial graphite particles are filled with the electrolyte. During charge-discharge, an electrochemical reaction occurs inside the electrode, and the defects create more lithium ion diffusion pathways and electrochemical reaction interfaces in the negative electrode material. This promotes 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 negative electrode material. Furthermore, appropriate surface roughness provides the anode material of the present invention with good processing performance, prevents the graphite sheet layer from falling off during the cycle process of the graphite anode material, and is advantageous for improving the material's cycle performance.

[0107] In Comparative Example 1, the amount of pore-forming agent added was too high, resulting in structural defects in the anode material and poorer surface fluidity. This lowered the tap density of the anode material, ultimately worsening the processing performance of the anode material, increasing the difficulty of coating the electrode pieces and manufacturing the battery. Furthermore, it was detrimental to maintaining the structural stability of the electrode pieces during the cycle process, and thus detrimental to improving the material's cycle performance and the battery's energy density.

[0108] In Comparative Example 2, since no pore-forming agent was added, the pore structure of the negative electrode material was insufficient. The limited diffusion channels restricted the diffusion of lithium ions at the solid-liquid interface and within the solid phase, further limiting the high-rate charge-discharge performance of the graphite.

[0109] In Comparative Example 3, the particle size of the pore-forming agent used does not meet the limiting range of the present invention. As a result, some of the pore sizes in the manufactured negative electrode material are too large, the pore defect distribution in the graphite material becomes non-uniform, the tap density of the negative electrode material decreases, and ultimately its processing performance deteriorates. This increases the difficulty of coating the electrode pieces and manufacturing the battery, and is also detrimental to maintaining the structural stability of the electrode pieces during the cycle process, as well as to improving the material's cycle performance and the battery's energy density.

[0110] In Comparative Example 4, the median diameter of the pore-forming agent used is smaller than the limiting range of the present invention. As a result, the pore size and pore volume of the manufactured artificial graphite are too small, and the limited diffusion pathways restrict the diffusion of lithium ions at the solid-liquid interface and within the solid phase, further limiting the high-rate charge-discharge performance of the graphite.

[0111] The parameters of the graphitization treatment and / or the addition ratio of the pore-forming agent in Comparative Examples 5 and 6 are not within the limiting range of the present invention. However, although the pore volume V, specific surface area S, and tap density T of the final manufactured anode material are within the numerical range of the embodiments of the present invention, the value of V × S / T does not satisfy the range of 2 to 10. Therefore, the rate performance, initial effect, and cycle performance of the anode material are all inferior to those of the anode material manufactured in the embodiments of the present invention.

[0112] The foregoing describes only preferred embodiments of the present invention and is not intended to limit it. Those skilled in the art will know that the present invention can have various modifications and changes. Any modifications, substitutions under the doctrine of equivalents, improvements, etc., made within the spirit and principles of the present invention should be within the scope of protection of the present invention.

Claims

1. A negative electrode material containing graphite, wherein the graphite has pores inside and / or on its surface, and the pore volume V (cm³) of the negative electrode material. ３ / kg), specific surface area S (m ２ The ratio of the ions ( / g) and the tap density T (g / cc) satisfy the relationship 2 ≤ V × S / T ≤ 10. The pore volume ranges from 2 cm³ / kg to 4.989 cm³ / kg. 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 specific surface area was measured using the JW-DX dynamic specific surface area rapid measuring instrument manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd. The negative electrode material is characterized in that the graphite is artificial graphite primary particles and / or artificial graphite secondary particles.

2. The negative electrode material according to claim 1, characterized in that the particle size satisfies the relational expression 0.9 ≤ (D90 - D10) / D50 ≤ 1.8 and 10 μm ≤ D50 ≤ 20 μm.

3. The negative electrode material according to claim 2, characterized by including at least one of the following features (1) to (2). (1) The negative electrode material has a D90 of 25 μm to 36 μm; (2) The negative electrode material has a D10 of 7 μm to 9 μm.

4. Specific surface area is 1.0 m² ２ / g to 2.0m ２ The negative electrode material according to claim 1, characterized in that it is / g.

5. The negative electrode material according to claim 1, characterized in that the tap density is 0.85 g / cc to 1.40 g / cc.

6. The negative electrode material according to claim 1, characterized in that the pores include at least one of micropores and mesopores.

7. The negative electrode material according to claim 1, characterized in that the pores have an average pore diameter of 80 Å to 125 Å.

8. A battery characterized by comprising the negative electrode material described in any one of claims 1 to 7.

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