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 anode materials, and specifically relates to anode materials and batteries in particular.

Background Art

[0002] Graphite-based anode materials have become the most mature anode materials at present due to factors such as their wide supply source, rich storage, relatively stable electrochemical performance, and the actual specific capacity density being close to the theoretical specific capacity.

[0003] + For graphite anode materials, the special layered structure of graphite determines that Li can only be inserted from the end face of the material and gradually diffuses inside the particles. The diffusion rate of lithium ions is low, the rate performance is poor, and lithium precipitation is likely to occur on the manufactured anode electrode sheet, which causes safety problems such as short circuit and thermal runaway of the battery. Therefore, it is necessary to improve the structure of the graphite material to improve the diffusion path of lithium ions. Those skilled in the art know that the ideal structure of the graphite material is formed by the regular arrangement of six-membered rings composed of carbon atoms. Generally, people hope to affect the pore volume and specific surface area of the graphite anode material by adjusting the size of the voids, thereby affecting the electrochemical performance of the graphite material. The coating layer improves the voids and cracks on the graphite surface. However, the applicant believes that in the actual application process, graphite has different defect structures both macroscopically and microscopically. There is a limit to improving the rate performance of the anode material by simply adjusting the size and structure of the voids, and it cannot meet the growing high demands of people for the performance of the graphite material.

[0004] Therefore, at the current mature stage of the development of graphite materials, it is necessary to further study graphite anode materials and maximize the improvement of the rate performance of graphite.

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​In order to overcome the above-mentioned drawbacks, the present invention provides a negative electrode material and a battery, which can improve the active sites and diffusion paths for lithium ion release and absorption in the negative electrode material, and are advantageous for improving the rate performance and processing performance of the negative electrode material.

Means for Solving the Problems

[0006] In a first aspect, an embodiment of the present invention provides a negative electrode material, the negative electrode material includes graphite, has pores inside and / or on the surface of the graphite, and the pore volume V (cm 3 / kg), specific surface area S (m 2 / g) and tap density T (g / cc) of the negative electrode material satisfy the relational expression 2 ≤ V×S / T ≤ 10, the pore volume is measured using an ASAP 2460 device manufactured by Micromeritics, USA, and calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model.

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

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

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

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

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

[0012] In some embodiments, the negative electrode material has a tap density of 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 pores have an average pore diameter of 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 stores Li +The diffusion path can be increased, and the specific surface area within a certain range can ensure a sufficient electrochemical reaction interface, promote the diffusion of lithium ions in the solid-liquid interface and within the solid phase, reduce concentration polarization, and is known to be beneficial for improving the capacity and rate performance of the anode material. As a result of intensive research based on this, the applicant has found that when only sufficient pore volume and specific surface area are satisfied, the overall performance of the anode material does not necessarily achieve the optimal and most stable effect. Graphite, as an anode material, not only needs to provide a sufficient diffusion path and reaction interface for lithium ion release and absorption depending on the pores and surface structure, but also requires the electrode sheet to have good processing performance, so that the battery can achieve a relatively ideal energy density and maintain the electrode sheet in a stable structure during the cycling process. The applicant believes that any structure that destroys the arrangement of other graphite six-membered rings such as the pores, particle surface, and crystal plane of graphite exists in graphite particles as defects of the ideal graphite structure. Therefore, reasonably controlling the defects can not only prevent the performance of the graphite material from degrading, but also improve the electrical performance of the material to a certain extent. In order to obtain the optimal graphite defect structure, it is necessary to accurately adjust the overall structural distribution of defects such as the surface, pores, and crystal lattice of graphite particles. Through analysis, the present invention combines these three elements for a large number of experimental explorations on the pore volume, specific surface area, and tap density of the graphite material. By controlling V×S / T of the anode material within the range of 2 to 10, while ensuring the processing performance of the anode material, the advantage of improving the lithium ion diffusion rate due to the rich overall structural defects of the material itself can be fully exerted, and ultimately the purpose of improving the high-rate charge and discharge performance of the artificial graphite anode material can be achieved.

[0019] Hereinafter, the present invention will be further described with reference to the drawings and examples.

Brief Description of the Drawings

[0020]

Figure 1

Embodiments for Carrying Out the Invention

[0021] To better understand the technical solution of the present invention, the following will describe in detail the embodiments of the present invention 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative labor 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", "the foregoing" and "said" used in the embodiments of the present invention and the claims 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 between 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 graphite negative electrode materials, 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 lithium ions in the process of lithium release and absorption by graphite can only enter between the graphite layers 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 high-rate charge and discharge performance of graphite is further restricted. Generally, all artificial graphites have a certain number of pore structures. On the one hand, the existence of pores increases the diffusion path of Li + inside the graphite material, and Li +By reducing the diffusion resistance, the rate performance of the material can be effectively improved. On the other hand, if the pore structure is too much, the specific surface area of the material is too large, which not only reduces the bulk density of graphite, but also due to the voids existing on the surface, the surface of graphite particles becomes more uneven and rough, the fluidity of graphite particles is poor, and finally the tap density of the graphite material decreases, further leading to the deterioration of the processing performance of the product and the electrochemical performance such as the initial efficiency and cycle. In fact, simply improving the pore structure alone cannot optimally achieve the comprehensive performance of the graphite negative electrode material, and there is still much room for improvement. Researchers have only studied the influence of single elements on the performance of graphite materials, and have not deeply studied the synergistic effect among multiple elements in order to maximize the improvement of the rate performance of graphite.

[0026] Therefore, at the current stage where the development of graphite materials has matured, improving a single parameter cannot meet the market's needs for low-cost and high-performance graphite materials. It is necessary to study the acting mechanism of the synergy of various elements and develop a graphite negative electrode material that meets the market's needs.

[0027] Hereinafter, taking the preparation process developed by the applicant as an example, the preparation process and related products will be described in more detail.

[0028] Embodiments of the present invention provide a method for manufacturing a negative electrode material, including the following steps. S10: Mix a carbon-based raw material, a pore-forming agent, and a binder 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, the pore-forming agent, and the binder is (70 - 94):(1 - 10):(5 - 20). S20: Perform a first heat treatment on the first precursor to carbonize it to obtain a second precursor. S30: The second precursor is subjected to a second heat treatment to graphitize it, obtaining a negative electrode material. Here, for the second heat treatment, first, the temperature is raised from room temperature to 1600°C - 1800°C at a heating rate of 2°C / min - 5°C / min, then the temperature is raised from 1600°C - 1800°C to 3000°C - 3200°C at a heating rate of 2°C / min - 8°C / min, held for 6h - 10h, after holding, the temperature is lowered to 800°C at a cooling rate of 0.1°C / min - 0.5°C / min, and finally the temperature is lowered to room temperature at a cooling rate of 2°C / min - 4°C / min.

[0029] In the above technical solution, the present invention mixes an appropriate proportion of a carbon-based raw material, a pore-forming agent with a specific particle size and particle size distribution, and a binder, and then performs carbonization and graphitization. By controlling the heating rate, cooling rate, and graphitization holding time during the carbonization and graphitization processes, the pore-forming agent is uniformly and rapidly removed, creating more lithium ion diffusion channels inside the graphite material, achieving the purpose of adjusting and controlling the defect structure and surface morphology of the graphite negative electrode material, optimizing the tap density, voids, and specific surface area parameters of the graphite negative electrode material, and ultimately effectively improving the processing performance and rate performance of the graphite negative electrode material. The process method is simple, the production cost is low, and the obtained graphite negative electrode material has characteristics such as a high tap density, good processing performance, and excellent rate performance, and can meet the usage needs of users for power batteries and energy storage.

[0030] Hereinafter, the manufacturing method of the present invention will be described in detail.

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

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

[0033] In some embodiments, the particle size of the carbon-based raw material after shaping treatment is 10 μm to 25 μm. Specifically, it may be 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein.

[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 former includes at least one of silicon oxide and silicon carbide.

[0036] In some embodiments, the pore former satisfies 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, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein. The median diameter D50 of the pore former may be 5 nm, 6 nm, 7 nm, 8 nm, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein. Within the above specific range, the fact that the pore former has a small and concentrated particle size is shown to be advantageous for the pore former to escape uniformly and rapidly from the carbon-based raw material during the graphitization process and form a uniform and controllable pore defect structure in the final graphite negative electrode material to serve as a lithium ion diffusion path.

[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). Specifically, the mass ratio of the carbon-based raw material, the pore-forming agent, and the binder may be, for example, 70:10:20, 75:8:17, 80:5:15, 85:3:12, or 94:1:5. Of course, other values within the above range are also possible, and the present invention is not limited here. If the addition amount of the pore-forming agent is greater than the limited range of the present invention, it is likely to increase the specific surface area of the material, reduce the tap density of the graphite material, and further cause deterioration of the electrochemical performance such as the processing performance, initial efficiency, and cycle of the product. If the addition amount of the pore-forming agent is less than the limited range of the present invention, the formed void structure is too small to achieve the purpose of creating more lithium ion diffusion channels and electrochemical reaction interfaces for the negative electrode material. Moreover, in the graphitization process, the pore-forming agent corresponds to impurities in the carbon raw material, which may affect the crystallization of graphite polycrystals and further affect the crystal lattice and the distribution of crystal plane defects of the graphite material. As can be understood, when the addition amount of the binder is less than the limited range of the present invention (the mass ratio of the carbon-based raw material to the binder is greater than 94:5), the obtained artificial graphite mainly consists of primary particles. When the proportion of the binder is high (the mass ratio of the carbon-based raw material to the binder is 85:12 or less), the obtained artificial graphite mainly consists of secondary particles.

[0039] S20: Subject the first precursor to a first heat treatment for carbonization to obtain a second precursor.

[0040] In some embodiments, the temperature of the first heat treatment is 800°C to 1100°C. Specifically, the temperature of the first heat treatment may be, for example, 800°C, 900°C, 1000°C, or 1100°C. Of course, other values within the above range are also possible, and the present invention is not limited here.

[0041] In some embodiments, the heat preservation time of the first heat treatment is 4h to 10h. Specifically, it may be 4h, 5h, 6h, 7h, 8h, 9h, or 10h. Of course, other values within the above range are also possible, and the present invention is not limited here.

[0042] In some embodiments, the heating rate of the first heat treatment is 2°C / min to 10°C / min. Specifically, it may 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, etc. Of course, other values within the above range may also be used, and the present invention is not limited herein.

[0043] In some embodiments, the cooling rate after the first heat treatment is 1°C / min to 5°C / min. Specifically, it may be 1°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min, etc. Of course, other values within the above range may also be used, and the present invention is not limited herein.

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

[0045] In the process of the first heat treatment, the carbon-based raw material in the first precursor shrinks due to pyrolysis and is converted into a carbon solid with a microcrystalline arrangement. The organic molecules and impurities present in the carbon-based raw material, pore former, and binder gradually escape during the heating process to form a pore structure. By controlling the temperature, time, and heating rate of the first heat treatment in the first precursor with a specific particle size of the pore former, pores and surfaces with a specific structure distribution are formed on the carbon solid, forming a uniformly distributed structural defect that is advantageous 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 form graphite. Here, for the second heat treatment, the temperature of the second precursor is raised from room temperature to 1600 °C to 1800 °C in 6 h to 10 h, with a heating rate of 2 °C / min to 5 °C / min, then raised from 1600 °C to 3000 °C to 3200 °C in 4 h to 6 h, with a heating rate of 2 °C / min to 8 °C / min, held at the temperature for 6 h to 10 h. After holding, the temperature is lowered to 800 °C in 150 h to 200 h, with a cooling rate of 0.1 °C / min to 0.5 °C / min, and then lowered to room temperature in 4 h to 6 h, with a cooling rate of 2 °C / min to 4 °C / min, thereby obtaining the negative electrode material.

[0047] Controlling the heating rate, cooling rate, and holding time of the second heat treatment within the above ranges is beneficial for the second precursor to uniformly and rapidly decompose and release the pore-forming agent from the material during the graphitization process, creating many lithium-ion diffusion channels inside the graphite material. Moreover, the graphite crystal structure is polycrystalline, with crystal plane defects existing between crystal grain boundaries. The above control can also maintain a highly regular crystal structure, achieving the purpose of adjusting and controlling the graphite negative electrode 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 negative electrode material.

[0048] As will be apparent to those skilled in the art, the battery manufacturing method described above is merely an example. Other methods commonly used in the art can be adopted without departing from the scope of the present description.

[0049] The present invention provides a negative electrode material, which includes graphite and has pores inside and / or on the surface of the graphite. 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. The pore volume is measured using an ASAP 2460 apparatus manufactured by Micromeritics, 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 technical solution, the negative electrode material according to the present invention is formed by adding a binder and a pore-forming agent with a specific particle size to a carbon-based raw material, and further performing production and processing through a carbonization and graphitization heating process at a specific heating rate and cooling rate. The pore-forming agent forms specific pores inside and / or on the surface of graphite, and the pore distribution can reflect the defect structure distribution in graphite polycrystals to a certain extent. Since there is a specific pore structure distribution inside the material after graphitization, these pore structure defects mainly originate from the volatilization of organic substances and the pore-forming agent, and are caused by phenomena such as shrinkage due to thermal decomposition of the carbon source and uneven internal stress due to differences in polycrystalline orientation. Finally, by presenting different pore forms such as closed pores, open pores, interlayer microcracks, and channels on the inside and / or surface of graphite, accurate control of the internal and / or surface defects of graphite is realized, and the pore volume, specific surface area, and tap density of the material reach the ideal adjustment and control design requirements. Here, pore defects uniformly distributed inside and / or on the surface of graphite are formed, and the uniformly distributed voids can reduce the expansion that occurs in the graphite negative electrode material during the charge and discharge process. Moreover, the pore defects improve the lithium storage capacity of the negative electrode material as an additional lithium storage space and cause an increase in the specific surface area. When the negative electrode material is manufactured as an electrode and applied to a battery, after injecting the electrolyte, the pores inside the artificial graphite particles are filled with the electrolyte. When charging and discharging, an electrochemical reaction occurs inside the electrode. The outer surface of the graphite particles with uneven stress at the pore defects and defect locations on the surface and inside of the graphite particles creates more lithium ion diffusion channels and electrochemical reaction interfaces with an appropriate tap on the negative electrode material, promotes the diffusion of lithium ions at the solid-liquid interface and within the solid phase, can reduce concentration polarization, and is beneficial to the improvement of the capacity and rate performance of the negative electrode material. In addition, the negative electrode material of the present invention has good processing performance and can prevent the exfoliation of the graphite sheet layer during the cycling process of the graphite negative electrode material, which is beneficial to the improvement of the cycling performance of the material.

[0051] Generally, the pore volume within a certain range in graphite can increase the diffusion path of Li ions, and the specific surface area within a certain range can guarantee 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 being beneficial to the improvement of the capacity and rate performance of the anode material. However, due to the disorder of the pore distribution of the material and the increase in the specific surface area, the improvement of the rate performance and processing performance of the graphite anode material is limited. Therefore, simply improving the pore structure cannot endow the graphite anode material with the optimal and most stable electrochemical performance. Thus, the present invention is advantageous in obtaining an anode material with excellent comprehensive performance such as rate performance and cycle performance while maintaining good processing performance by controlling V×S / T of the graphite anode material within the above range. In the present invention, the value range of V×S / T is 2 to 10. 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, etc. Naturally, other values within the above range may also be used, and the present invention is not limited here. 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. The larger V is, the richer the pore structure of the graphite particles is, and the specific surface area S increases within a certain range. However, the lower the initial efficiency of the graphite anode material is, the worse the cycle performance becomes. The smaller T is, the worse the processing performance is during the process of manufacturing slurry and electrodes using graphite as the anode material. That is, the rate performance and processing performance of the graphite anode material cannot be improved by a single factor, and the improvement of the rate performance of the material by controlling a single factor is limited.Therefore, the present invention can combine both of the above elements by using the combined parameter of V×S / T, and although the voids formed by the closed pores cannot be accurately measured, it is recognized that it can provide a passage rich in lithium ions. Due to the action of the defect stress, microcracks are likely to occur around the closed pore voids and at the grain boundaries of the crystal grains, and both are considered to be potential fracture sources inside the material. When crushing it, the graphite particles are preferentially collided and crushed at the locations where the defect stress is large and there are microcracks. At this time, the internal closed pore part is opened and exposed on the surface, or pores are opened inside and the deep pores are exposed to form the outer surface of the graphite particles. Finally, the material surface is roughened. At the same time, some grain boundary defects of the graphite polycrystals may also be split and exposed due to the stress action. Since its surface is relatively smooth, the combined state of the above two types of surface defects affects the fluidity of the graphite particles. Finally, the applicant can use the relationship between the tap density, specific surface area and pore volume to represent the comprehensive structural state of the internal / surface defects of the graphite to a certain extent, and control V×S / T to be 2 to 10, and relatively excellent rate performance and processing performance can be obtained simultaneously. Preferably, it is found that the value range of V×S / T is 2.5 to 8.4.

[0052] In some embodiments, the negative electrode material satisfies the relational expressions 0.9≦(D90-D10) / D50≦1.8 and 10μm≦D50≦20μm. In the above formula, D90 is the particle size at which the cumulative distribution of the material particles is 90%, D10 is the particle size at which the cumulative distribution of the material particles is 10%, D50 is the particle size at which the cumulative distribution of the material particles is 50%, and is also referred to as the median diameter.

[0053] An ideal battery material needs to have a narrow particle size distribution. As is clear from research, too much fine powder causes the battery material with high activity to continuously consume the electrolyte during cycling, leading to deterioration of the capacity retention rate. Large particles with larger expansion are likely to cause particle pulverization during cycling and are likely to result in continuous thickening of the SEI. Therefore, by narrowing the particle size distribution, the cycle performance of the material can be improved. In the anode material of the present invention, that (D90 - D10) / D50 is between 0.9 and 1.8 and D50 is between 10 μm and 20 μm indicates that the span of the particle size of the anode material is small, that is, the anode material has a uniform particle size distribution. Thereby, the material can avoid the above problems, has a higher tap density, and is more likely 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, etc. Of course, it may also be other values within the above range, and the present invention is not limited here. When (D90 - D10) / D50 is less than 0.9, it is shown that the particle size distribution of the anode material is too narrow, which is disadvantageous for the coating of the anode material for electrode sheet manufacturing, thereby deteriorating the processing performance. When (D90 - D10) / D50 exceeds 1.8, it is shown that there is a lot of fine powder in the anode material, which is disadvantageous for improving the cycle performance of the anode material.

[0054] In some embodiments, the median diameter D50 of the anode material may specifically be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc. Of course, it may also be other values within the above range, and the present invention is not limited here.

[0055] In some embodiments, the anode material has D90 between 25 μm and 36 μm, and specifically may be 25 μm, 28 μm, 30 μm, 32 μm, 35 μm or 36 μm, etc. Of course, it may also be other values within the above range, and the present invention is not limited here.

[0056] In some embodiments, the negative electrode material has a D10 of 7 μm to 9 μm. Specifically, it may be 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein.

[0057] In some embodiments, the negative electrode material has a pore volume of 2 cm 3 / kg to 6 cm 3 / kg. Specifically, the negative electrode material has a pore volume of 2 cm 3 / kg, 3 cm 3 / kg, 4 cm 3 / kg, 5 cm 3 / kg or 6 cm 3 / kg, etc. It may also be other values within the above range, and the present invention is not limited herein. Within the above range, it is shown that the graphite negative electrode material has an appropriate pore structure, can effectively provide sufficient channels for the diffusion of lithium ions, and is advantageous for improving the rate performance of the negative electrode material.

[0058] In some embodiments, the negative electrode material has a specific surface area of 1.0 m 2 / g to 2.0 m 2 / g. Specifically, the negative electrode material has a specific surface area of 1.0 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.3 m 2 / g, 1.4 m 2 / g, 1.5 m 2 / g, 1.6 m 2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g or 2.0 m 2 / g, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein. Within the above range, the negative electrode material has abundant surface active sites and 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, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein. Within the above range, the negative electrode material has good processing performance, reduces the difficulty of coating the electrode sheet and manufacturing the battery, maintains the structural stability of the electrode sheet during the cycling process, and is also advantageous for improving the cycling performance of the material and the energy density of the battery.

[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, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein.

[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, it may be 80 Å, 90 Å, 100 Å, 110 Å, 120 Å, or 150 Å, etc. Of course, it may also be other values within the above range, and the present invention is not limited herein.

[0063] The embodiments of the present invention further provide a battery including the above negative electrode material.

[0064] As will be apparent to those skilled in the art, the battery manufacturing method described above is only an example. Without departing from the content of the present invention, other methods commonly used in the art may be adopted, and it may also be manufactured and measured for other types of batteries, such as sodium-ion batteries, potassium-ion batteries, etc.

[0065] Hereinafter, embodiments of the present invention will be further described with reference to a plurality of examples. However, the present invention is not limited to the following specific examples and may be appropriately modified without changing the scope of the main claim.

[0066] Example 1 (1) The median diameter of the material powder after pulverizing the petroleum coke raw material is 20 μm or less. (2) The powder obtained in step (1), the nano-silica pore former, and the coal-based pitch binder are uniformly mixed to obtain a first precursor. Here, the mass ratio of petroleum coke, pore former, and binder is controlled to be 70:10:20. The pore former has a D50 of 8 nm and (D90 - D10) / D50 = 0.5. (3) The first precursor obtained in step (2) is carbonized under heating conditions of 1000 °C to obtain a second precursor. (4) The second precursor obtained in step (3) is graphitized at a high temperature under conditions of 3000 °C, and the heating and cooling process curve is controlled as follows: Heat up to 1800 °C within 10 h (heating rate is 3 °C / min), heat up to 3000 °C within 6 h (heating rate is 3.3 °C / min), keep warm for 6 h. After keeping warm, cool down to 800 °C within 150 h (cooling rate is 0.3 °C / min), and then cool down to room temperature within 6 h (cooling rate is 2.2 °C / min). (5) The material obtained in step (4) is crushed, sieved, and mixed to finally obtain a graphite negative electrode material with a D50 of 10 μm to 20 μm.

[0067] The above negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly mainly secondary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area of the negative electrode material are shown in Table 1.

[0068] Example 2 Example 1 is different in that the heating and cooling curve used in step (4) is as follows: heat up to 1800 °C within 8 h (heating rate is 3.8 °C / min), heat up to 3000 °C within 5 h (heating rate is 4 °C / min), hold for 8 h. After holding, cool down to 800 °C within 170 h (cooling rate is 0.2 °C / min), and then cool down to room temperature within 5 h (cooling rate is 2.7 °C / min). A graphite negative electrode material is obtained.

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

[0070] Example 3 Example 1 is different in that the heating and cooling curve used in step (4) is as follows: heat up to 1800 °C within 6 h (heating rate is 5 °C / min), heat up to 3200 °C within 5 h (heating rate is 4.7 °C / min), hold for 10 h. After holding, cool down to 800 °C within 190 h (cooling rate is 0.2 °C / min), and then cool down to room temperature within 4 h (cooling rate is 3.3 °C / min). A graphite negative electrode material is obtained.

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

[0072] Example 4 Example 1 is different in that the heating and cooling curve used in step (4) is as follows: heat up to 1600 °C within 6 h (heating rate is 4.4 °C / min), heat up to 3200 °C within 4 h (heating rate is 6.7 °C / min), hold for 10 h. After holding, cool down to 800 °C within 200 h (cooling rate is 0.2 °C / min), and then cool down to room temperature within 4 h (cooling rate is 3.3 °C / min). A graphite negative electrode material is obtained.

[0073] In this embodiment, the negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly secondary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area 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 former, 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 secondary artificial graphite particles. The numerical values of the pore volume, tap density, and specific surface area 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 former, 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 secondary artificial graphite particles. The numerical values of the pore volume, tap density, and specific surface area 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 former, 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 secondary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area 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 former, and binder in step (2) is 94:1:5.

[0081] In this embodiment, the negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite. As shown in FIG. 1, which is an SEM image of the negative electrode material manufactured for this embodiment, as can be seen from FIG. 1, the artificial graphite has a small particle size and mainly consists of primary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area of the negative electrode material are shown in Table 1.

[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 negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area of the negative electrode 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 negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area of the negative electrode 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 negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly consisting of secondary particle artificial graphite. The numerical values of the pore volume, tap density, and specific surface area of the negative electrode 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 negative electrode material includes primary particle artificial graphite and secondary particle artificial graphite, mainly mainly secondary particle artificial graphite. The numerical values of the pore volume, tap density and specific surface area of the negative electrode 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 in step (2), no pore-forming agent is added, and the mass ratio of petroleum coke and 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 of 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 a high temperature under the condition of 3000 °C, and the heating and cooling process curve is controlled as follows: heating up to 1800 °C within 17 h (heating rate is 1.76 °C / min), heating up to 3000 °C within 6 h (heating rate is 3.3 °C / min), holding for 6 h, and after holding, cooling down to room temperature (cooling rate 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 a high temperature under the condition of 3000 °C, and the heating and cooling process curve is controlled as follows: heating up to 3000 °C within 17 h (heating rate is 3 °C / min), holding for 6 h, and after holding, cooling down to room temperature (cooling rate 3 °C / min).

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

[0097] (2) Method for measuring the pore volume and average pore diameter of the negative electrode material: Measure using an ASAP2460 device manufactured by Micromeritics, USA. The 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: Measure using a JW-DX dynamic specific surface area rapid measuring instrument manufactured by Beijing Jingwei Gaobo Science and Technology Co., Ltd. The unit is m 2 / 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) Observe the surface morphology of the negative electrode material with an S4800 scanning electron microscope manufactured by Hitachi.

[0101] (6) Battery performance test method: Samples manufactured in Examples 1 to 20 and Comparative Examples 1 to 2: Conductive adhesive: (CMC + SP): SBR = 95:1.5:1.5:2 by mass ratio are magnetically stirred in deionized water for 8 h and uniformly mixed. The obtained slurry is applied onto a copper foil and vacuum dried at 60 °C to obtain a working electrode. Metallic lithium is used as the counter electrode and the reference electrode, the separator is Celgard 2325, the electrolyte is 1 mol∙L-1 LiPF6-EC (ethylene carbonate) / DMC (dimethyl carbonate) / EMC (ethyl methyl carbonate) (volume ratio 1:1:1), and the assembly of CR2016 type button cells is completed in a glove box filled with high-purity argon gas. Four cells are manufactured for each set of samples.

[0102] The initial discharge capacity / initial discharge efficiency test is performed using a LAND battery tester. The charge and discharge conditions are: standing for 2 h, discharging from 0.1C to 0.005V at 0.09C, 0.08C... 0.02C and then to 0.001V, standing for 15 min, charging to 1.5V at 0.1C, and standing for 15 min.

[0103] The full charge state swelling test for 20 cycles is measured using a mold cell. The surface density of the graphite negative electrode is 70 g / m 2 , the compacted density is 1.6 g / cc, the corresponding positive electrode is LCO, the surface density is 166 g / m 2 , the compacted density is 3.5 - 3.7 g / cc. The cycle test conditions are: performing 1 cycle of charge and discharge at 0.1C rate for the first time, 1 cycle of charge and discharge at 0.2C rate for the second time, and charge and discharge at 0.5C rate from the third time to the 20th time. Then, the thickness change data of the electrode sheet collected by the sensor during the cycle process is corresponded to the cycle data collected by the electrochemical test cabinet (test cabinet) to obtain the full charge state swelling value for 20 cycles.

[0104]

Table 1

[0105]

Table 2

[0106] As shown in Table 1 and Table 2, the present invention constructs a proportional relationship among the specific surface area, pore volume of the negative electrode material, and the tap density of the negative electrode material, so as to reflect the overall distribution status of defects such as channels, crystal lattices, and interlayer microcracks inside the graphite particles. If it is 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 pore defect distribution inside the negative electrode material is uniform. The uniformly distributed pore defects can reduce the expansion occurring during the charge and discharge process of the graphite negative electrode material, and the pores can improve the lithium storage capacity of the negative electrode material as an additional lithium storage space, and cause an increase in the specific surface area within a certain range. When the negative electrode material is manufactured into an electrode and applied to a battery, after injecting the electrolyte, the pores inside the artificial graphite particles are filled with the electrolyte. When charging and discharging, an electrochemical reaction occurs inside the electrode. The defects create more lithium ion diffusion paths and electrochemical reaction interfaces by the negative electrode material, promoting the diffusion of lithium ions at the solid-liquid interface and within the solid phase, and reducing the concentration polarization, which is shown to be advantageous for improving the capacity and rate performance of the negative electrode material. Also, appropriate surface roughness endows the negative electrode material of the present invention with good processing performance, can prevent the exfoliation of the graphite sheet layer during the cycling process of the graphite negative electrode material, and is advantageous for improving the cycle performance of the material.

[0107] In Comparative Example 1, since the addition amount of the pore former is too large, there are structural defects in the negative electrode material and the surface fluidity is worse, so the tap density of the negative electrode material is lowered, ultimately resulting in poor processing performance of the negative electrode material, increasing the difficulty of coating the electrode sheet and manufacturing the battery, and being disadvantageous for maintaining the structural stability of the electrode sheet during the cycling process, and also being disadvantageous for improving the cycle performance of the material and the energy density of the battery.

[0108] In Comparative Example 2, since no pore former was added, the pore structure of the negative electrode material was insufficient. The limited diffusion paths 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, since the particle size of the pore former used did not meet the limited range of the present invention, the pore sizes of some of the manufactured negative electrode materials were too large, the pore defect distribution of the graphite material was non-uniform, the tap density of the negative electrode material was low, and ultimately its processing performance was poor, increasing the difficulty of coating the electrode sheet and manufacturing the battery. It was also disadvantageous for maintaining the structural stability of the electrode sheet during the cycling process, and was also disadvantageous for improving the cycle performance and energy density of the battery.

[0110] In Comparative Example 4, since the median diameter of the pore former used was smaller than the limited range of the present invention, the pore size and pore volume of the manufactured artificial graphite were too small. The limited diffusion paths 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.

[0111] The graphitization treatment parameters and / or the addition ratio of the pore former in Comparative Examples 5 and 6 were not within the limited range of the present invention. However, the pore volume V, specific surface area S, and tap density T of the finally manufactured negative electrode material were respectively within the numerical ranges of the embodiments of the present invention. However, since the value of V×S / T did not satisfy the range between 2 and 10, the rate performance, initial efficiency, and cycle performance of the negative electrode material were all inferior to those of the negative electrode material manufactured in the examples of the present invention.

[0112] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, substitutions based on the doctrine of equivalents, improvements, etc. made within the spirit and principles of the present invention should all be included within the protection scope of the present invention.

Claims

1. A negative electrode material containing graphite, having pores inside and / or on the surface of the graphite, and satisfying the relational expression 2 ≤ V × S / T ≤ 10 for the pore volume V (cm ３ / kg), specific surface area S (m ２ / g), and tap density T (g / cc) of the negative electrode material. The pore volume is measured using an ASAP 2460 apparatus manufactured by Micromeritics, USA, and is calculated within a pore diameter range of 17 Å to 3000 Å using the BJH Desorption cumulative volume of pores model. The negative electrode material is characterized by this.

2. The negative electrode material according to Claim 1, wherein the particle size satisfies the relational expressions 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) In the negative electrode material, D90 is 25 μm to 36 μm; (2) In the negative electrode material, D10 is 7 μm to 9 μm.

4. The pore volume is 2 cm ３ / kg to 6 cm ３ / kg, and the negative electrode material according to claim 1 is characterized by this.

5. The specific surface area is 1.0 m ２ / g to 2.0 m ２ / g, and the negative electrode material according to claim 1, characterized in that it has such a specific surface area.

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

7. The negative electrode material according to Claim 1, characterized by including artificial graphite primary particles and / or artificial graphite secondary particles.

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

9. The negative electrode material according to Claim 1, characterized in that the average pore diameter of the pores is 80 Å to 125 Å.

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

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